[Federal Register Volume 79, Number 213 (Tuesday, November 4, 2014)]
[Rules and Regulations]
[Pages 65508-65540]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2014-25789]
[[Page 65507]]
Vol. 79
Tuesday,
No. 213
November 4, 2014
Part III
Department of Transportation
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Federal Aviation Administration
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14 CFR Parts 25 and 33
Airplane and Engine Certification Requirements in Supercooled Large
Drop, Mixed Phase, and Ice Crystal Icing Conditions; Final Rule
Federal Register / Vol. 79 , No. 213 / Tuesday, November 4, 2014 /
Rules and Regulations
[[Page 65508]]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Parts 25 and 33
[Docket No. FAA-2010-0636; Amendment Nos. 25-140 and 33-34]
RIN 2120-AJ34
Airplane and Engine Certification Requirements in Supercooled
Large Drop, Mixed Phase, and Ice Crystal Icing Conditions
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Final rule.
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SUMMARY: The Federal Aviation Administration is amending the
airworthiness standards applicable to certain transport category
airplanes certified for flight in icing conditions and the icing
airworthiness standards applicable to certain aircraft engines. The
regulations will improve safety by addressing supercooled large drop
icing conditions for transport category airplanes most affected by
these icing conditions; mixed phase and ice crystal conditions for all
transport category airplanes; and supercooled large drop, mixed phase,
and ice crystal icing conditions for all turbojet, turbofan, and
turboprop engines.
DATES: Effective January 5, 2015.
ADDRESSES: For information on where to obtain copies of rulemaking
documents and other information related to this final rule, see ``How
To Obtain Additional Information'' in the SUPPLEMENTARY INFORMATION
section of this document.
FOR FURTHER INFORMATION CONTACT: For part 25 technical questions
contact Robert Hettman, FAA, Propulsion/Mechanical Systems Branch, ANM-
112, Transport Airplane Directorate, Aircraft Certification Service,
1601 Lind Avenue SW., Renton, WA 98057-3356; telephone (425) 227-2683;
facsimile (425) 227-1320; email [email protected].
For part 33 technical questions contact John Fisher, FAA,
Rulemaking and Policy Branch, ANE-111, Engine and Propeller Directorate
Standards Staff, Aircraft Certification Service, 12 New England
Executive Park, Burlington, MA 01803; telephone (781) 238-7149;
facsimile (781) 238-7199; email [email protected].
For part 25 legal questions contact Douglas Anderson, FAA, Office
of the Regional Counsel, ANM-7, Northwest Mountain Region, 1601 Lind
Avenue SW., Renton, WA 98057-3356; telephone (425) 227-2166; facsimile
(425) 227-1007; email [email protected].
For part 33 legal questions contact Vince Bennett, FAA, Office of
the Regional Counsel, ANE-007, New England Region, 12 New England
Executive Park, Burlington, MA 01803; telephone (781) 238-7044;
facsimile (781) 238-7055; email [email protected].
SUPPLEMENTARY INFORMATION:
Authority for This Rulemaking
The FAA's authority to issue rules on aviation safety is found in
Title 49 of the United States Code. Subtitle I, Section 106 describes
the authority of the FAA Administrator. Subtitle VII, Aviation
Programs, describes in more detail the scope of the agency's authority.
This rulemaking is under the authority described in Subtitle VII,
Part A, Subpart III, Section 44701, ``General requirements.'' Under
that section, the FAA is charged with promoting safe flight of civil
aircraft in air commerce by prescribing minimum standards required in
the interest of safety for the design and performance of aircraft;
regulations and minimum standards in the interest of safety for
inspecting, servicing, and overhauling aircraft; and regulations for
other practices, methods, and procedures the Administrator finds
necessary for safety in air commerce. This regulation is within the
scope of that authority because it prescribes--
New safety standards for the design and performance of
certain transport category airplanes and aircraft engines; and
New safety requirements necessary for the design,
production, and operation of those airplanes, and for other practices,
methods, and procedures relating to those airplanes and engines.
Overview of Final Rule
The FAA is adopting this final rule to revise certain regulations
in Title 14, Code of Federal Regulations (14 CFR) part 25
(Airworthiness Standards: Transport Category Airplanes) and part 33
(Airworthiness Standards: Aircraft Engines) related to the
certification of transport category airplanes and turbine airplane
engines in icing conditions. We are also creating the following new
regulations: Sec. 25.1324--Angle of attack systems; Sec. 25.1420--
Supercooled Large Drop Icing Conditions; Appendix O to Part 25--
Supercooled Large Drop Icing Conditions; Appendix C to Part 33 (this is
intentionally left blank as a placeholder for potential future
rulemaking unrelated to icing); and Appendix D to Part 33 Mixed Phase
and Ice Crystal Icing Envelope (Deep Convective Clouds). To improve the
safety of transport category airplanes operating in supercooled large
drop (SLD), mixed phase, and ice crystal icing conditions, these
regulations will:
Require airplanes most affected by SLD icing conditions to
meet certain safety standards in an expanded certification icing
environment that includes freezing drizzle and freezing rain. These
safety standards include airplane performance and handling qualities
requirements.
Expand the engine and engine installation certification,
and some airplane component certification regulations (for example,
angle of attack and airspeed indicating systems) to include freezing
drizzle, freezing rain, mixed phase, and ice crystal icing conditions.
Summary of the Costs and Benefits of the Final Rule
The benefits and costs are summarized in the table below. As shown
in the table, the total estimated benefits exceed the total estimated
costs for this final rule.
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2012$ 7% Present value
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Benefit Cost Benefit Cost
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Part 33 Engines.............. Qualitative.......... $13,936,000 Qualitative......... $11,375,927
Large Part 25 Airplanes...... $362,319,857......... 14,126,333 $76,861,295......... $11,531,295
Other Part 25 Airplanes...... $220,570,582......... 33,198,788 $50,028,690......... $19,385,401
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Total.................... $582,890,439......... 61,261,121 $126,889,985........ $42,292,624
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[[Page 65509]]
Background
Safety concerns about the adequacy of the icing certification
standards were brought to the forefront of public and governmental
attention by a 1994 accident in Roselawn, Indiana, involving an Avions
de Transport R[eacute]gional (ATR) ATR 72 series airplane. The National
Transportation Safety Board (NTSB), with assistance from ATR, the FAA,
the French Direction G[eacute]n[eacute]ral de l'Aviation Civile, Bureau
D'Enquetes et D'Analyses, the National Aeronautics and Space
Administration (NASA), and others, conducted an extensive investigation
of this accident. This investigation determined that freezing drizzle-
sized drops created a ridge of ice on the wing's upper surface aft of
the deicing boots and forward of the ailerons. The investigation
further concluded that this ridge of ice contributed to an uncommanded
roll of the airplane. Based on these findings, the NTSB recommended
changes to the icing certification requirements.
The atmospheric icing conditions for certification are specified in
part 25, appendix C. The atmospheric condition (freezing drizzle) that
contributed to the Roselawn accident is outside the icing envelope
currently used for certifying transport category airplanes. The term
``icing envelope'' is used in part 25, appendix C, and in this rule to
refer to the environmental icing conditions within which the airplane
must be shown to be able to safely operate. The term ``transport
category airplanes'' is used throughout this rulemaking document to
include all airplanes type-certificated to part 25 regulations.
Another atmospheric icing environment outside the current icing
envelope is freezing rain. The FAA has not required airplane
manufacturers to show that airplanes can operate safely in a freezing
drizzle or freezing rain icing environment.
As a result of this accident and consistent with related NTSB
recommendations,\1\ the FAA tasked the Aviation Rulemaking Advisory
Committee (ARAC),\2\ through its Ice Protection Harmonization Working
Group (IPHWG), to do the following:
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\1\ NTSB Safety Recommendations A-96-54 and A-96-56 are
available in the rule Docket No. FAA-2010-0636 and on the Internet
at http://www.ntsb.gov/doclib/recletters/1996/A96_48_69.pdf.
\2\ Published in the Federal Register on December 8, 1997 (62 FR
64621). http://www.gpo.gov/fdsys/pkg/FR-1997-12-08/pdf/97-32034.pdf.
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Define an icing environment that includes SLD conditions.
Consider the need to define a mixed phase icing
environment (supercooled liquid and ice crystals).
Devise requirements to assess the ability of an airplane
to either safely operate without restrictions in SLD and mixed phase
conditions or safely operate until it can exit these conditions.
Study the effects icing requirement changes could have on
Sec. Sec. 25.773, Pilot compartment view; 25.1323, Airspeed indicating
system; and 25.1325, Static pressure systems.
Consider the need for a regulation on ice protection for
angle of attack probes.
The FAA ultimately determined that the revised icing certification
standards should include SLD, mixed phase, and ice crystal icing
conditions. This rule is based on ARAC's recommendations to the FAA.
A. Related Actions
ARAC's IPHWG submitted additional icing rulemaking recommendations
to the FAA that led to the Part 25 and Part 121 Activation of Ice
Protection final rules.\3\ For certain airplanes certificated for
flight in icing, those rulemaking actions revise the certification and
operating rules for flight in icing conditions by requiring either
installation of ice detection equipment or changes to the airplane
flight manual (AFM) to ensure timely activation of the airframe ice
protection system. Although those rulemaking actions address flight in
icing conditions, they do not directly impact this final rule.
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\3\ Part 25 Activation of Ice Protection, Docket No. FAA-2007-
27654, published in the Federal Register on August 3, 2009 (74 FR
38328). Part 121 Activation of Ice Protection, Docket No. FAA-2009-
0675, published in the Federal Register on August 22, 2011 (76 FR
52241).
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B. NTSB Recommendations
The NTSB issued NTSB Safety Recommendation Numbers A-96-54 and A-
96-56 as a result of the Roselawn accident previously discussed. This
rulemaking partially addresses those NTSB recommendations. The FAA is
considering separate rulemaking activities associated with revisions to
14 CFR part 23 regulations for small airplanes and 14 CFR part 121
operational regulations to complete the FAA response to these NTSB
recommendations. The NTSB recommendations are as follows:
1. A-96-54
Revise the icing criteria published in 14 CFR parts 23 and 25, in
light of both recent research into aircraft ice accretion under varying
conditions of liquid water content (LWC), drop size distribution, and
temperature, and recent developments in both the design and use of
aircraft. Also, expand the appendix C icing certification envelope to
include freezing drizzle/freezing rain and mixed water/ice crystal
conditions, as necessary (A-96-54 supersedes A-81-116 and -118).
2. A-96-56
Revise the icing certification testing regulation to ensure that
airplanes are properly tested for all conditions in which they are
authorized to operate, or are otherwise shown to be capable of safe
flight into such conditions. If safe operations cannot be demonstrated
by the manufacturer, operational limitations should be imposed to
prohibit flight in such conditions, and flightcrews should be provided
with the means to positively determine when they are in icing
conditions that exceed the limits for aircraft certification.
C. Summary of the Notice of Proposed Rulemaking
The notice of proposed rulemaking (NPRM), Notice No. 10-10,
published in the Federal Register on June 29, 2010 (75 FR 37311), is
the basis for this final rule. After receiving several requests to
extend the public comment period, the FAA extended the comment period
by 30 days to September 29, 2010, with a document published in the
Federal Register on August 16, 2010 (75 FR 49865).
To improve the safety of transport category airplanes operating in
SLD, mixed phase, and ice crystal icing conditions, the FAA proposed
new regulations in the NPRM to:
Expand the certification icing environment to include
freezing drizzle and freezing rain environments.
Require airplanes most affected by SLD icing conditions to
meet certain safety standards in the expanded certification icing
environment, including airplane performance and handling qualities
requirements.
Expand the engine and engine installation certification
regulations, and some airplane component certification regulations (for
example, angle of attack and airspeed indicating systems), to include
freezing rain environments, freezing drizzle environments, mixed phase,
and ice crystal icing conditions. For certain regulations, we proposed
using a subset of these icing conditions.
D. General Overview of Comments
The FAA received comments from 31 commenters during the public
comment period: Five private citizens, the Aerospace Industries
Association (AIA), Airbus Industrie (Airbus), AirDat LLC, the Airline
Pilots Association (ALPA),
[[Page 65510]]
American Kestrel Company, LLC, (AKC), The Boeing Company, Bombardier,
Cessna, Dassault Aviation, Embraer, Eurocopter, the European Aviation
Safety Agency (EASA), Foster Technology, LLC, the General Aviation
Manufacturers Association (GAMA), GE Aviation, Gulfstream, Goodrich
Sensors and Integrated Systems (GSIS), Honeywell Engines, the National
Research Council (NRC), the NTSB, Pratt & Whitney Canada, the Regional
Airline Association (RAA), the Swiss Federal Office of Civil Aviation
(FOCA), Snecma, Transport Canada Civil Aviation (TCCA), and Turbomeca.
Each commenter submitted multiple comments.
Twelve commenters stated specific support for the rulemaking,
recognized the efforts made by the ARAC working group, and suggested
specific changes intended to clarify the regulations or to clarify the
intent. The NTSB and two private citizens were disappointed that the
rulemaking took so long.
Fourteen commenters stated neither support nor opposition, but
suggested specific changes or identified areas for clarification.
Two commenters, a rotorcraft manufacturer and a rotorcraft engine
manufacturer, opposed the proposed changes to Sec. Sec. 33.68 and
33.77. These commenters suggested the FAA make provisions to exclude
rotorcraft from the revised regulations.
Two private citizens expressed concern for the data and methods
used to define the SLD conditions proposed in part 25, appendix O.
One commenter suggested that the FAA should begin a certification
process toward use of a new methodology for detecting ice over a pitot
inlet, for which the commenter has filed a provisional patent.
The FAA received additional comments in a letter dated June 21,
2011, signed by four private citizens. The letter provided additional
explanation for previously submitted comments. The FAA also considered
this additional information while drafting this final rule.
The FAA made changes to the final rule in response to the public
comments. Summaries of the issues raised by the public comments and FAA
responses, including explanations of changes, are provided below. The
full text of each commenter's submission is available in the docket for
this rulemaking.
Discussion of Public Comments and Final Rule
Proposed Appendix O to Part 25
In the NPRM, the FAA proposed to expand the existing icing
conditions identified in appendix C of part 25 to include new SLD icing
conditions defined in a new appendix O. The FAA made changes to
appendix O as a result of comments received, but the general format
remains unchanged. Appendix O is structured like part 25, appendix C,
with part I defining icing conditions and part II defining airframe ice
accretions for showing compliance with the airplane performance and
handling qualities requirements of part 25, subpart B.
Three private citizens provided comments related to the flight data
collection approach used to acquire information about SLDs, the flight
data used, and the analysis approach to generate the SLD engineering
standards in part 25, appendix O. We will address these three
commenters as a group.
One concern was with the methods related to collecting and
evaluating SLD icing conditions. One commenter stated that the research
aircraft were well equipped to document the environment; however, both
research aircraft had serious deficiencies regarding their on-board
ability to document aircraft performance degradation from icing.
Two commenters were concerned that only the database jointly
created by Environment Canada and NASA was used to define the SLD icing
conditions. Another commenter was concerned about the statistical
significance of the data collected and did not think there was enough
flight test evidence collected to provide the same level of probability
established for part 25, appendix C, icing conditions. Two commenters
stated that the flight test campaign failed to relate their data
collection results to previously published results, such as those
published by the University of Wyoming. Specifically, the commenters
noted that appendix O does not contain data for a LWC greater than 0.45
grams per cubic meter.
One commenter also stated that other published analysis methods for
an SLD encounter, such as the University of Wyoming LWC/drop size
technique, result in the most adverse icing conditions and are not
contained within appendix O. The commenter also noted that a clear
distinction does not exist between the icing conditions defined in part
25, appendix C, and the conditions defined in part 25, appendix O. This
uncertainty would leave the pilot with the responsibility of making a
scientific finding of which icing conditions the airplane was in,
unless on-board droplet size and LWC measurement means and droplet data
processing are provided.
Regarding the flight research project's lack of on-board ability to
document aircraft performance degradation from icing, we agree.
However, obtaining measurements of aircraft performance within icing
conditions was the lowest priority objective of the flight research
project. The primary objectives of the test were to identify icing
conditions beyond those covered in appendix C of part 25, and to
identify a method for presenting the data in a way that could be used
as an engineering standard. Specific aircraft performance and handling
degradations in icing conditions are unique for each aircraft design.
Performance degradation and handling qualities criteria for appendix C
and appendix O icing encounters will need to be determined by the
design approval holder for each aircraft design based on the applicable
regulations, guidance materials, and testing as necessary to
demonstrate compliance. This final rule specifies the expanded
environmental icing conditions for consideration during the
certification process as well as the performance and handling qualities
that must be demonstrated.
Regarding the sufficiency of the flight test data to form a
statistically reliable database, we disagree. In developing appendix O,
we used all historically available flight research data on SLD, not
just the Environment Canada-NASA flight test data. This broad
collection of data is statistically similar to the data that was used
to develop appendix C.
Regarding the comments about our proposed definition of SLD in
appendix O, we also disagree. The University of Wyoming data were
included in the FAA master database on SLD icing conditions. However,
these data were not used to support the final determinations for the
LWC values for the appendix O engineering standards. The University of
Wyoming aircraft was not equipped with two-dimensional optical array
probes, which were deemed essential by the IPHWG. Without the probes,
it was not possible to distinguish between cloud drops and ice
particles. Therefore, the University of Wyoming cloud data were not
considered usable for supporting the analysis of SLD LWC/drop size
properties for appendix O. As a result, the Environment Canada-NASA
database was used to determine the engineering standards because of the
quality of the data contained therein and the analysis methods used in
that database. Both the quality of the data
[[Page 65511]]
and the analysis method used by the database ensured the accuracy of
the definition for appendix O icing conditions.
Regarding the comment that the University of Wyoming LWC/drop size
technique results in the most adverse icing conditions and are not
contained within appendix O, we disagree. That analysis technique
suggests that one type of icing condition would be severe for all
airplanes, regardless of the type of ice protection system used, or the
extent of the protection. Appendix O contains a variety of icing
conditions, not just those deemed most severe using the University of
Wyoming analysis technique.
In response to other comments, figures 1 and 4 of appendix O have
been revised in this final rule to reflect the LWC proposed by the
IPHWG. As a result, freezing drizzle conditions with a median volume
diameter (MVD) greater than 40 microns fall within the adverse region
that would be identified using the University of Wyoming LWC/drop size
technique. No changes to appendix O were made as a result of these
comments.
With regard to the comment suggesting that the pilot will have to
make a scientific finding to determine which icing conditions the
airplane is in, we disagree. For those types of airplanes most
vulnerable to SLD icing conditions, the level of operations in SLD
icing conditions for which the airplane is approved will be determined
during the airplane certification process in accordance with Sec.
25.1420. If approval is requested for operations in a portion of the
icing conditions defined in appendix O, then the airplane manufacturer
will have to show that the pilot can determine if the operational
envelope for which the airplane is certified has been exceeded as
required by Sec. 25.1420(a)(2). Since part of the certification will
be evaluating the means used to distinguish when the airplane is in
icing conditions outside the certified envelope, the pilot will not be
faced with the ambiguity of trying to determine the distribution of
water drops in the environment in which he or she is flying.
Several commenters said that proposed figures 1, 4, and 7 in
appendix O of the NPRM were different than what was proposed by the
IPHWG, and that the FAA did not provide an explanation for those
differences. The commenters also noted that the higher LWC contained in
the figures proposed in the NPRM could have a significant impact on an
applicant's design. GSIS specifically noted that the higher water
content defined in appendix O will have the effect of greatly
increasing power requirements for electro-thermal deicing systems.
Several commenters also suggested that figures 1, 3, 4, and 6 of
appendix O would be easier to use if the corner data points were
defined in the figures.
We agree. We reviewed the figures proposed in the NPRM and the data
used by the IPHWG to generate the figures. We revised figures 1 and 4
to reflect the lower water content values proposed by the IPHWG, but
the water content in appendix O is still higher than within appendix C
at the same temperature. The higher water content may increase the
power requirements for some electro-thermal deicing system designs, but
not to the extent that may have been necessary with the water contents
proposed in the NPRM. The environmental conditions defined in appendix
O are valid conditions that will need to be considered for applicable
future designs. Our review of the data used to generate the scaling
factor curve in figure 7 indicates that the figure 7 proposed by the
IPHWG in the task 2 working group report was incorrect; \4\ figure 7 in
the NPRM was correct. Therefore, figure 7 in this final rule remains as
proposed in the NPRM. Figures 1, 3, 4, and 6 of appendix O in this
final rule have been revised to identify the corner data points for
clarity.
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\4\ The data used to complete the IPHWG report is detailed in
report DOT/FAA/AR-09/10, Data and Analysis for the Development of an
Engineering Standard for Supercooled Large Drop Conditions, dated
March 2009. A copy of the report is available in the rule Docket No.
FAA-2010-0636. The data used for figure 7 are described on pages 34-
39 of that report.
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GSIS asked if there is a scientific basis for applying the
horizontal extent of 17.4 nautical miles. GSIS also noted that the same
MVD, temperature, and LWC at altitude exist in both appendix O and
appendix C and asked the FAA to clearly define the mass distribution
boundary between appendix O and appendix C.
Our application of the 17.4 nautical mile horizontal extent in
appendix O was made on a practical basis and not on a purely scientific
basis; it was selected for consistency with the appendix C continuous
maximum icing conditions with which designers are already familiar. We
are unaware of any scientific reasons for not applying the 17.4
nautical mile horizontal extent in this manner.
The LWC values in appendix O are based on an analysis of the data
from the jointly created Environment Canada-NASA flight research SLD
database, report DOT/FAA/AR-09/10.\5\ Figure 11 of that report shows a
plot of temperature versus LWC for appendix O freezing drizzle
environments that is valid for the reference distance of 17.4 nautical
miles (32.2 km). Appendix C and appendix O define environmental
conditions that overlap one another as the conditions transition from
appendix C to appendix O. Therefore, there is not a clear mass
distribution boundary that can be defined.
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\5\ A copy of the report is in the rule Docket No. FAA-2010-
0636.
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One commenter, a private citizen, noted that the NPRM did not
identify the vertical extent for part 25, appendix O, figure 6. We
disagree. The pressure altitude range and vertical extent for freezing
rain were provided in appendix O, part I, paragraph (b) in the NPRM
located under figure 3. We clarified appendix O, part I, by moving all
of the general text describing the meteorological parameters, including
vertical extent, ahead of the figures.
One commenter suggested that the icing conditions in appendix O
should be revised to reflect water drop distribution as a function of
mean effective diameter (MED) as opposed to MVD. We do not agree. MED
is the term used in part 25, appendix C. Examination of National
Advisory Committee for Aeronautics (NACA) references \6\ shows that MED
is the same as MVD if certain assumptions are made about the drop
distribution, namely that it is one of the Langmuir distributions. MVD,
as the more general term, is applicable to any drop distribution. Since
the drop distribution described in appendix O does not follow a
Langmuir distribution, MVD is more appropriate. We did not change the
final rule or appendix O as a result of this comment.
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\6\ National Advisory Committee for Aeronautics Technical Note
2738, A Probability Analysis of the Factors Conducive to Aircraft
Icing in the United States, by William Lewis and Norman R. Bergrun,
July 1952.
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A private citizen commented that appendix O should define a time to
use for delayed recognition of entry into icing conditions and the time
to exit icing conditions. We do not agree. The responsibility for
proposing delayed recognition times, delayed ice protection system
activation times, or times required to exit icing conditions, based on
unique operational procedures or performance characteristics of the ice
protection system, rests with the applicant. We did not change the rule
based on this comment.
Boeing suggested a change to appendix O, part I, paragraph (c), to
add an equation to determine the LWC for
[[Page 65512]]
horizontal distances other than 17.4 nautical miles.
We agree that adding such an equation could be beneficial. The
equation proposed by Boeing, however, expressed horizontal distance in
kilometers, which would be inconsistent with other figures in appendix
O. Instead of the equation proposed by Boeing, we added to appendix O,
part I, paragraph (c), a similar equation that uses units of nautical
miles.
Several commenters noted that appendix O, part II, paragraph
(b)(5)(ii), in the NPRM made reference to Sec. Sec. 25.143(k) and
25.207(k). However, Sec. Sec. 25.143(k) and 25.207(k) do not exist in
the current part 25 and were not added by the NPRM.
We agree. The references to those sections were inadvertently
included in the NPRM. We revised appendix O to delete the statement
referencing Sec. Sec. 25.143(k) and 25.207(k).
Airbus noted that part II, paragraph (c)(7)(v) of appendix O states
that crew activation of the ice protection system is in accordance with
a normal operating procedure provided in the AFM, except that after
beginning the takeoff roll, it must be assumed that the crew does not
take any action to activate the ice protection system until the
airplane is at least 400 feet above the takeoff surface. Airbus
commented that this appears to be a direct cut and paste from the
appendix C regulations and recommended removing the sentence. Airbus
claimed that while this is perhaps understandable for appendix C icing
conditions, it would seem reasonable to expect the crew to activate the
wing anti-ice system (WAIS) prior to takeoff if there are SLD icing
conditions within 400 feet of the runway, whether the AFM specifically
states that it is required or not.
We do not agree. The rule addresses flightcrew actions occurring
after beginning the takeoff roll, while Airbus' comment refers to
actions that the flightcrew would take before beginning the takeoff.
Nevertheless, the FAA does not expect flightcrews to be aware of all
SLD icing conditions that may exist up to a height of 400 feet above
the takeoff surface, nor do we agree that it would be reasonable to
expect the flightcrew to activate the WAIS prior to takeoff if there
was no procedure telling them to do so. We did not change the rule
based on this comment.
Embraer commented that the last sentence in appendix O, part II,
paragraph (b)(2)(ii), which proposed to define the holding ice
conditions in part 25, appendix O, part II, paragraph (b)(2), should be
applicable to the whole of paragraph (b)(2), and not just to the
transit time through one appendix O cloud and one appendix C cloud
specified in paragraph (b)(2)(ii). Embraer commented that it would be
clearer to describe the total holding time in a separate paragraph
(b)(2)(iii) that says: ``The total exposure to the icing conditions
need not exceed 45 minutes.'' We agree, and changed appendix O, part
II, paragraph (b)(2), to indicate that the total exposure time for
holding ice does not need to exceed 45 minutes.
Availability of Engineering Tools To Show Compliance With the Rule
Several commenters stated that available engineering tools (icing
wind tunnels and tankers, ice accretion prediction codes, and other
analysis methods) are inadequate for showing compliance with the new
rule. Bombardier commented that without validated tools, it is not
practical to implement the requirements proposed in the NPRM.
Bombardier believed that efforts should be focused on implementing
incremental regulatory changes in parallel with the appropriate
technological developments to meet that regulatory change.
Boeing commented similarly, stating that the FAA and NASA had
developed a plan several years ago to align the timing of the new
regulations with the availability of validated engineering tools and
test capabilities for SLD conditions. Boeing added that the tools and
test facilities necessary to effectively demonstrate compliance with
the regulations are not available, and that this lack of availability
will be particularly problematic for applicants desiring to operate
within appendix O conditions. Boeing noted that the current situation
will require applicants to either use highly conservative approaches,
build new icing wind tunnel facilities, or expend great efforts to
conduct extensive flight testing in search of a meteorological
condition, which occurs very infrequently. Boeing said that this was
not the approach anticipated by industry, and that it will impose a
severe burden on many applicants beyond that established in the
economic evaluation of the proposed regulation, without adding any
commensurate safety benefit.
AKC also commented that current test facilities are limited in
their ability to produce freezing drizzle, in particular drop
distributions greater than 40 microns MVD. The water drop distribution
curves provided in appendix O are not produced by any facility known to
AKC, and there are no facilities that produce freezing rain in a
fashion that duplicates either the flight or ground test environment.
The NRC of Canada's comments reflected concerns about how the water
drop distribution curves in appendix O are to be used. Further, a
private citizen commented that the droplet diameters for appendix O
conditions can only be reproduced in a few icing wind tunnels.
We do not agree that available engineering tools (icing wind
tunnels and tankers, ice accretion prediction codes, and other analysis
methods) are inadequate for showing compliance with the new rule. We
recognize that the current engineering tools available to show
compliance with the new SLD rule have not been validated in every
aspect, and also have some limitations. We also recognize that for
freezing rain, few validated engineering tools are available. However,
methods are available to simulate freezing drizzle. Further, we
recognize that relying upon available simulation methods, combined with
engineering judgment, will be required for finding compliance with the
appendix O requirements of part 25, especially for freezing rain
conditions.
After reviewing the current state of available compliance methods
and engineering tools, the FAA has determined that there is sufficient
capability for applicants to effectively demonstrate compliance with
this final rule. The IPHWG evaluated the current capabilities of these
tools in 2008-2009 during a review requested by industry members
through ARAC. The IPHWG evaluation of SLD engineering tools, which
proposed methods of compliance based on the current state of the
available engineering tools, supports the FAA conclusion. The FAA
considered estimates provided by industry and has made adjustments to
the proposed economic evaluation, which is incorporated in the economic
evaluation for this final rule. This adjustment increases the cost for
complying with the requirements of this final rule; however, this final
rule remains cost beneficial. A summary of the final regulatory
evaluation is provided in the ``Regulatory Notices and Analyses''
section of this final rule and the complete document is included in the
public docket.
As to freezing drizzle, the current icing wind tunnel test
capabilities for SLD icing conditions have been demonstrated. However,
we recognize that some limitations exist: Icing wind tunnel spray
systems evaluated during the IPHWG's review do not support bi-modal
mass distributions (mass ``peaks'' for two different drop sizes)
provided in appendix O and do not produce realistic freezing rain
simulations for the
[[Page 65513]]
majority of those conditions. NASA examined alternate spray methods to
simulate portions of a bi-modal spray using spray sequencing techniques
to approximate drop distributions found in natural conditions
(reference: American Institute of Aeronautics and Astronautics report
AIAA 2005-76, Simulation of a Bimodal Large Droplet Icing Cloud in the
NASA Icing Research Tunnel \7\). NASA demonstrated the water spray
sequencing technique for an airfoil with unprotected surfaces and the
results showed rougher ice accretion textures than appendix C ice
shapes.
---------------------------------------------------------------------------
\7\ A copy of this report is available in the rule Docket No.
FAA-2010-0636.
---------------------------------------------------------------------------
Experience indicates that SLD icing conditions generally result in
rougher ice accretion textures. NASA has also developed preliminary
scaling methods for SLD test applications and has developed large
droplet algorithm improvements to its ice accretion prediction code by
adding SLD subroutines. Other ice accretion code developers have
incorporated SLD capabilities in their respective computational tools.
A number of icing wind tunnel owners have tested SLD icing conditions
in their facilities and are capable of performing tests for at least a
portion of the appendix O environments.
Regarding flight testing, Sec. 25.1420 requires that applicants
provide analysis to establish that ice protection for the various
airplane components is adequate, taking into account the various
operational configurations. Section 25.1420 also describes flight
testing in natural or simulated icing conditions, as necessary, to
support the analysis. The IPHWG acknowledged the difficulties in flight
testing in natural SLD, and agreed it would not be specifically
required under Sec. 25.1420. We concur, and have left flight testing
as an option in the regulation. Until the engineering tools become more
mature, flight tests in natural appendix O icing conditions may be
necessary to achieve certification for unrestricted flight in appendix
O conditions in accordance with Sec. 25.1420(a)(3).
Proposed Revisions to Sec. 33.68 Should Not Apply to Engines Installed
on Rotorcraft
Eurocopter and Turbomeca noted the proposed part 33 changes would
apply to all turbine engines, including turboshaft engines intended for
installation in rotorcraft. The proposed revision to Sec. 33.68 would
require all turbine engines to be capable of operating in the extended
icing conditions defined in part 25, appendix O. However, the IPHWG
task 2 report and the NPRM only addressed airplane accidents and
incidents; it did not include rotorcraft. Eurocopter and Turbomeca
proposed provisions to exclude rotorcraft from the new engine
requirements. The FAA did not receive any comments providing specific
support for the proposed applicability to rotorcraft.
We agree. The IPHWG did not review rotorcraft accidents or
incidents in icing conditions and did not propose rulemaking associated
with rotorcraft. As a result, we revised the proposed Sec. 33.68 to
separate the icing requirements for turboshaft engines used for
rotorcraft from turbojet, turbofan, and turboprop engines used for
airplanes. The icing requirements pertaining to turboshaft engines are
unchanged and require that turboshaft engines operate safely throughout
the icing conditions defined in part 29, appendix C. Section 33.68 now
requires that turbojet, turbofan, and turboprop engines not installed
on rotorcraft operate safely throughout the icing conditions defined in
part 25, appendix C, the SLD conditions defined in part 25, appendix O,
and the mixed phase and ice crystal conditions defined in part 33,
appendix D.
Applicability of Proposed Sec. 25.1420
In the NPRM, the FAA proposed to add a new Sec. 25.1420. Proposed
Sec. 25.1420 would have required specific airplanes certified for
flight in icing conditions to be capable of either: (1) Operating
safely within the new SLD icing conditions defined in part 25, appendix
O; (2) operating safely in a portion of the new appendix O conditions,
with the capability to detect when conditions beyond those used for
certification have been encountered, and then safely exit all icing
conditions; or (3) have a means to detect when appendix O icing
conditions are encountered, and be capable of safely exiting all icing
conditions. The FAA proposed to limit the applicability of Sec.
25.1420 to airplanes that have a maximum takeoff weight (MTOW) of less
than 60,000 pounds, or airplanes equipped with reversible flight
controls regardless of MTOW.
The applicability of Sec. 25.1420 was discussed within the IPHWG
and consensus could not be reached. A discussion of this issue was
provided in the NPRM under the heading ``Differences from the ARAC
Recommendations.'' Bombardier, ALPA, EASA, Goodrich, Gulfstream, the
NTSB, and the TCCA provided comments to the NPRM that supported the
majority position of the IPHWG, questioning the technical justification
used to exclude airplanes with a MTOW of 60,000 pounds or greater.
Airbus, AIA, Boeing, and GAMA provided comments in response to the NPRM
to support the proposed applicability based on MTOW because airplanes
with a MTOW of 60,000 pounds or greater have not previously experienced
accidents or incidents associated with flight in SLD. Embraer and Pratt
& Whitney Canada comments to the NPRM specifically noted support for
AIA's position.
A review of the IPHWG analysis indicates that airplanes with a MTOW
of 60,000 pounds or greater have not experienced accidents or incidents
associated with flight in SLD. The FAA originally considered including
all new airplanes in the applicability for Sec. 25.1420, regardless of
MTOW; however, the projected costs of extending the rule to include
airplanes with a MTOW of 60,000 pounds or greater exceeded the
projected benefits due to the positive in-service history (i.e., lack
of accidents) of these airplanes in SLD.
The commenters did not present any new data or information that was
not discussed within the IPHWG, or discussed within the NPRM. The
commenters that opposed limiting the applicability of the rule
suggested that lift and control surface size, or wing chord length, are
important parameters affecting sensitivity to a given ice accretion.
They based their opposition on airplane weight, in part, because the
ratio of wing and control surface sizes to airplane weight varies
between airplane designs.
We agree that design features such as control surface size and wing
chord length are important parameters, which can affect the sensitivity
of a wing to the icing conditions described in part 25, appendix O. As
proposed in the NPRM, in order to issue a rule with estimated costs
commensurate with the estimated benefits, the applicability of Sec.
25.1420 is limited based on airplane weight due to the positive service
histories of certified airplanes.
If future designs for larger airplanes contain novel or unusual
design features that affect this successful in-service history, and
those design features make the airplane more susceptible to the effects
of flight in SLD icing conditions, the FAA can issue special conditions
to provide adequate safety standards. The FAA issues special conditions
in accordance with Sec. 21.16. No changes have been made to the
applicability of Sec. 25.1420 as a result of these comments.
[[Page 65514]]
Clarification of Definitions
Embraer noted that Sec. 25.1420(b) uses the terms ``simulated
icing tests'' and ``simulated ice shapes'' in various subparagraphs.
Embraer suggested that subparagraphs Sec. 25.1420(b)(1) and (b)(2) use
the phrase ``artificial ice'' as defined in Advisory Circular (AC) 25-
28, Compliance of Transport Category Airplanes with Certification
Requirements for Flight in Icing Conditions, instead of ``simulated
icing tests.''
We do not agree. Section 25.1420(b)(1) and (b)(2) describe test
methods, not the resulting ice shapes. The terminology ``simulated
icing tests'' is used in Sec. 25.1420 consistently with Sec. 25.1419.
We added definitions for ``Simulated Ice Shape'' and ``Simulated Icing
Test'' to Sec. 25.1420 that are consistent with previously issued
guidance.
AIA, Boeing, and GAMA suggested a clarification to the definition
of ``reversible flight controls.'' AIA and GAMA suggested that the
addition of servo tab inputs in the examples provides a more complete
and accurate description.
We agree and have clarified the definition of ``reversible flight
controls'' to include the example of servo tab inputs. In addition,
since the definition of ``reversible flight controls'' is necessary to
determine the applicability of Sec. 25.1420, we added the definition
to Sec. 25.1420.
Applicability of Proposed Appendix O Icing Conditions to Part 23
Airplanes and Previously Certified Part 25 Airplanes
The NTSB and a private citizen commented that the icing conditions
proposed in appendix O should be applicable to part 23 airplanes
because they are the type of airplanes most affected by flight into
icing conditions. The NTSB also stated that the proposed rule should be
expanded beyond newly certified airplanes to include all deice boot-
equipped airplanes currently in service that are certified for flight
in icing conditions (reference NTSB Safety Recommendation A-07-16).\8\
The NTSB pointed out SLD is an atmospheric condition that can create
dangerous flight conditions for both the current fleet of aircraft and
newly certified aircraft.
---------------------------------------------------------------------------
\8\ NTSB Safety Recommendation A-07-16 is available in the rule
Docket No. FAA-2010-0636 and on the Internet at http://www.ntsb.gov/doclib/recletters/2007/A07_12_17.pdf.
---------------------------------------------------------------------------
Regarding the applicability of proposed appendix O to part 23
airplanes, we disagree with adding part 23 airplanes to the
applicability, as that is beyond the scope of this rulemaking. However,
we chartered an Aviation Rulemaking Committee (ARC) to review the
IPHWG's rulemaking recommendations for part 25 and to make similar
recommendations for part 23. The ARC transmitted a report detailing
part 23 rulemaking recommendations to the FAA in a letter dated
February 19, 2011, and provided supplemental recommendations in a
letter dated April 27, 2011. The ARC transmitted its recommendations
for a final task in early 2012. We are studying these recommendations
and may pursue additional rulemaking for part 23 airplanes.
We agree that severe icing conditions, including SLD, can create
dangerous flight conditions for both current and future airplanes.
However, we do not agree that the part 25 and part 33 rule changes
discussed in this amendment should apply to existing airplanes. Such a
retroactive application would, in effect, be changing the certification
basis of operational airplanes to correct an unsafe condition,
something generally done by airworthiness directive (AD). To address
the unsafe condition, we have already issued ADs to mandate procedures
to activate the ice protection equipment at the first sign of ice
accretion, and to incorporate procedures into the AFM so the flightcrew
can identify when they are in severe icing conditions that exceed
certificated limitations, and safely exit.
New airworthiness standards are not intended to correct an unsafe
condition; rather, they are intended to improve the level of safety for
new airplane designs. In the context of SLD, we are considering
operational rules to mandate certain elements of the airworthiness
standards adopted in this rulemaking for previously certified
airplanes. However, those requirements are beyond the scope of this
rulemaking and require separate rulemaking action.
Applicability of Part 33, Appendix D, to Sec. 25.1093, Induction
System Icing Protection, and Sec. 33.68, Induction System Icing
The NTSB supported changes to Sec. Sec. 33.68 and 33.77, noting
that since we issued an icing-related AD for the Beechjet 400A no
additional reports of unsafe icing conditions on that airplane have
been noted. The FAA infers that the NTSB was referring to AD 2006-21-
02.\9\ That AD was issued following reports of dual engine flameouts in
high altitude icing conditions believed to include ice crystals. AIA,
Airbus, Boeing, and GAMA supported the addition of mixed phase and ice
crystal conditions, such as those defined in part 33, appendix D.
---------------------------------------------------------------------------
\9\ AD 2006-21-02, Docket No. FAA-2006-26004, published in the
Federal Register on October 10, 2006 (71 FR 29363), is applicable to
Raytheon (Beech) Model 400, 400A, and 400T series airplanes; and
Raytheon (Mitsubishi) Model MU-300 airplanes.
---------------------------------------------------------------------------
Honeywell commented that the current lack of and/or immature state
of engine test facilities to demonstrate compliance to part 33,
appendix D, could result in a significant increase in an applicant's
activities to show compliance because of the additional flight testing
required to locate the ice crystal conditions. Honeywell also noted
that flying in actual ice crystal conditions would put the flightcrew
at considerable risk. Honeywell recommended that appendix D be removed
until test facilities have developed the capabilities to run tests for
ice crystal conditions. Honeywell also suggested that the FAA make
research funds available to facilities to develop this capability.
We agree, in part. We agree that only limited capability exists for
testing engines in ice crystal conditions. We also agree that
flightcrews unnecessarily operating in icing conditions puts them at
risk. We do not agree, however, that appendix D should be removed until
test facilities develop the capabilities to run tests for ice crystal
conditions, or that FAA make funds available for research to develop
these capabilities. Section 33.68(e) allows for certification
demonstration by test, analysis, or combination of the two. Consistent
with ARAC Engine Harmonization Working Group (EHWG) recommendations,
until ice crystal tools and test techniques have been developed and
validated, the engine manufacturer may use a comparative analysis to
specific field events. This analysis should show that the new engine
cycle or design feature, or both, would result in acceptable engine
operation when operating in the ice crystal environment defined in
appendix D to part 33. This comparative analysis should also take into
account both suspected susceptible design features, as well as
mitigating design features. We did not change the rule based on this
comment.
GSIS suggested that provisions be made for a detect-and-exit
strategy for part 33, appendix D, conditions; similar to what was
proposed in the NPRM for part 25, appendix O, conditions.
We disagree. We do not believe part 33, appendix D, conditions can
be detected with enough time to exit before damage occurs. Therefore, a
detect-and-
[[Page 65515]]
exit strategy for part 33, appendix D, conditions is inappropriate. As
proposed in the NPRM, the mixed phase and ice crystal icing conditions
defined in part 33, appendix D, have been added to Sec. Sec.
25.1093(b)(1) and 33.68(a).
Applicability of Proposed Appendix O to Sec. 25.1093, Induction System
Icing Protection, and Sec. 33.68, Induction System Icing
AIA, Airbus, Boeing, and GAMA provided comments that there are no
known events that support a safety concern due to engine induction
system icing in SLD aloft. In particular, the EHWG evaluated known
icing-related engine events since 1988 and found no events in SLD
aloft. The EHWG credited this result to the current rigorous compliance
to part 25, appendix C, conditions for engines. The commenters believe
that the safety of these systems for flight in appendix O conditions
has already been proven by service history. The commenters state that
continuing to certify future systems to the requirements for appendix C
icing conditions, in conjunction with consideration of excellent
service history of similar designs in appendix O conditions, should be
acceptable assurance of the safety of future designs. The commenters
suggested that consideration of the icing conditions defined in
appendix O be removed from Sec. 25.1093.
We agree that there are no known events that support a safety
concern due to engine induction system icing in SLD aloft. However,
there have been reports of engine fan damage or high vibration while
operating in SLD icing conditions. The ARAC database on engine events
contains 231 icing events reported by engine manufacturers from
approximately 1988 through 2003, and includes part 25, appendix C; part
25, appendix O; and part 33, appendix D events. Although the intent of
the event database was to focus on icing events outside of appendix C,
there are several appendix C events included in this database. The
event database does not include any accidents.
The EHWG identified 46 part 25, appendix O (SLD) events. All events
occurred on the ground and resulted in fan damage and/or high
vibrations so a precise effect on the safety of these events was not
discernible.
Additionally, the EHWG identified nine additional events that it
thought might have been related to operations in SLD icing conditions:
Four were in-flight and all nine were on tail mounted engine
configurations. Again, the events resulted in fan damage and/or high
vibrations, with indeterminable power loss. Although these nine events
are of concern, the EHWG did not judge them to be safety significant.
An additional 14 in-flight events were not clearly identifiable as
SLD events but were described as heavy icing below 22,000 feet and
resulted in fan damage and/or high vibrations. These events did not
clearly fall within conditions defined in either appendix C or appendix
O. However, the general description of the icing conditions and engine
damage is consistent with reports of engine damage that occurred within
the icing conditions defined in appendix O, so those might have been
SLD events.
After reviewing the data, the EHWG clearly identified SLD as a
threat for engine damage during ground operations. Furthermore, the
EHWG could not rule out SLD as a potential in-flight safety threat, and
decided to include it as part of its recommendations to the FAA. As
proposed in the NPRM, the part 25, appendix O, SLD icing conditions
have been added to Sec. 33.68. Also, as proposed in the NPRM, Sec.
33.77 contains requirements to demonstrate engine capability to ingest
the applicable minimum ice slab defined in Table 1 of Sec. 33.77. The
ice slab sizes defined in Table 1 of Sec. 33.77 are a function of the
engine inlet diameter. Turbojet, turbofan, and turboprop engine
manufacturers must demonstrate, in part, that the engine will continue
to operate throughout its power range in the icing conditions defined
in part 25, appendix O, and following ingestion of an ice slab that is
a function of the engine inlet diameter. The changes to the
requirements in Sec. Sec. 33.68 and 33.77 are intended to improve the
level of safety for turbojet, turbofan, and turboprop engines used on
transport category airplanes in icing conditions, in part because of
reports of engine damage or high engine vibrations while operating in
SLD conditions.
We agree large airplanes that have likely encountered appendix O
conditions have had a successful in-service history with no clearly
identifiable safety significant events. After considering the comments
received, we revised Sec. 25.1093(b), compared to what was proposed in
the NPRM, so consideration of the icing conditions described in
appendix O does not apply to airplanes with a MTOW equal to or greater
than 60,000 pounds. As proposed in the NPRM, the applicability of the
icing conditions described in part 25, appendix C; part 33, appendix D;
and falling and blowing snow remain applicable to all turbine engine
installations on transport category airplanes. In addition, the engine
requirements in Sec. Sec. 33.68 and 33.77 for operation in all icing
conditions still apply to engines installed on part 25 airplanes
regardless of the airplanes' MTOW. The applicability of appendix O
conditions in Sec. 25.1093(b) as a function of airplane weight is
consistent with the revised applicability of Sec. 25.1420, which
establishes minimum airworthiness standards for detection and safe
operation in appendix O conditions. Airplanes that have been
susceptible to performance issues while operating in SLD icing
conditions have been smaller airplanes with a MTOW less than 60,000
pounds.
Section 25.1093(b) was revised to provide relief for larger
airplanes because of the successful in-service history of existing
larger airplane designs and larger airplane engine inlet designs. As
previously discussed, the changes to the requirements in Sec. Sec.
33.68 and 33.77 are intended to improve the level of safety for turbine
engines used on all airplanes, including large airplanes, while
operating in SLD conditions. If future designs for larger airplanes
contain novel or unusual design features that affect this successful
in-service history, and those design features make the airplane more
susceptible to the effects of flight in SLD icing conditions, the FAA
can issue special conditions to provide adequate safety standards.
Boeing, AIA, and GAMA also provided comments on the results of an
SLD analysis, including the use of the NASA Lewis Ice Accretion
Program, commonly referred to as LEWICE. The analysis yielded overly
conservative accreted ice mass calculations resulting in large amounts
of ice on the radome. The results from this analysis indicated to
Boeing that radome ice shedding would be a concern, and it would
require ice protection on the currently unprotected radome surfaces to
reduce ice build-up to acceptable limits. The weight increase for
radome ice protection equipment would result in increased fuel burn and
increased operational costs that were not included in the IPHWG
economic analysis. Boeing also stated that most large airplanes are
operating without restrictions today and are safely encountering SLD
conditions.
Analytical methods used by Boeing to determine SLD ice accretions
on radomes show considerably higher ice mass accretions than either
past calculations or past experience has indicated for other icing
conditions. These analyses were never presented to the IPHWG and
details were not
[[Page 65516]]
included with Boeing's comments to support the FAA's evaluation of
Boeing's methods. As previously discussed, we revised Sec. 25.1093(b)
compared to what was proposed in the NPRM. For the purposes of
compliance with Sec. 25.1093(b), the icing conditions defined in
appendix O are not applicable to airplanes with a MTOW equal to or
greater than 60,000 pounds. To show compliance with Sec. 25.1093(b),
analysis may be used for the radome as a potential airframe ice source.
For compliance with Sec. 25.1093(b), applicants may use qualitative
analysis supported by similarity to a previous design with a successful
service history to show that ice accretions ingested into the engine
from the new airplane design will be less than the ice slab size
presented in Sec. 33.77 Table 1, ``Minimum Ice Slab Dimensions Based
on Engine Inlet Size.''
Applicability of Proposed Appendix O to Sec. 25.773, Pilot Compartment
View
AIA, Airbus, Boeing, and GAMA commented that there are no known
events that support a safety concern due to windshield icing in SLD
aloft. The commenters state the safety of these systems for flight in
appendix O conditions has been proven by service history. They believe
that continuing to certify future systems to the requirements for
appendix C icing conditions, in conjunction with consideration of
excellent service history of similar designs in appendix O conditions,
should be an acceptable assurance of the safety of future designs. One
commenter, an individual, commented that Sec. 25.773 should not be
changed, as ice accretion on the windshield is one of the few
indications used to recognize the condition.
We do not agree. Section 25.773 is intended to ensure that a clear
portion of the windshield is maintained in icing conditions, which
enhances safety in icing conditions. For airplanes certified to detect
appendix O conditions, or a portion of appendix O conditions, and
required to exit all icing conditions when the icing conditions used
for certification have been exceeded, the pilot must have a clear view
out the windshield; not only when the airplane is in appendix O icing
conditions, but also during the time it takes to detect and exit all
icing conditions within which the airplane is not approved to operate.
For airplanes not certified with the detect-and-exit strategy, appendix
C and appendix O conditions need to be considered for the entire time
the airplane is in the applicable icing conditions.
Section 25.773 does not require the windshield to be completely
free of ice in all icing conditions. Therefore, this requirement does
not preclude using ice accreting in certain locations on the windshield
as an indication that the airplane is in icing conditions beyond those
in which it is approved to operate. We did not change the rule based on
these comments.
Applicability of Proposed Appendix O to Sec. 25.1323, Airspeed
Indicating System, Sec. 25.1324, Angle of Attack System, and Sec.
25.1325, Static Pressure Systems
AIA, Airbus, Boeing, and GAMA commented that there are no known
events that support an in-flight safety concern for angle of attack
systems in SLD aloft. They believe the safety of these component
systems for flight in appendix O conditions has already been proven by
service history. The commenters recommended the reference to appendix O
be removed from the requirements in Sec. Sec. 25.1323, 25.1324, and
25.1325.
We do not agree. If certification for flight in icing is desired,
part 25 requires the airplane to be capable of safely operating in
icing conditions. The airplane and its components are taken into
account during flight in icing certification programs. For these
reasons, all icing conditions should be considered. Sections 25.1323,
25.1324, and 25.1325 include considerations for the SLD icing
environment defined in part 25, appendix O.
Applicability of Proposed Appendix O to Sec. 25.929, Propeller Deicing
AIA and GAMA commented that there are no known events that support
a safety concern with propeller icing in SLD. In particular, AIA and
GAMA noted the EHWG evaluated all known icing-related events since 1988
and found no events in SLD aloft. The commenters credit the current
rigorous compliance using appendix C conditions for this result. The
commenters believe the safety of these systems for flight in appendix O
conditions has already been proven by service history. They further
believe that continuing to certify future systems to the requirements
for appendix C icing conditions, in conjunction with consideration of
excellent service history of similar designs in appendix O conditions,
should be acceptable assurance for the safety of future designs.
We do not agree. Propeller icing is typically not implicated in
events because ice accretion on the propeller is usually not visible in
flight. However, in one suspected SLD event \10\ included in the IPHWG
list of applicable events, the NTSB Performance Group reported that the
flight data recorder derived drag increment was much higher than an
increment measured in flight test with intercycle ice (by a factor of 2
near the time where the pilot lost control of the airplane). The NTSB
report does not speculate what caused the large drag increment, but it
could have been airframe SLD ice accretion, propeller SLD ice
accretion, or a combination of both. In addition, appendix J in AC 20-
73A, Aircraft Ice Protection, dated August 16, 2006, documents a flight
test encounter in which suspected SLD caused a severe performance
penalty due to propeller ice accretion. FAA research tests, documented
in report DOT/FAA/AR-06/60, Propeller Icing Tunnel Test on a Full-Scale
Turboprop Engine,\11\ have duplicated the event discussed in the AC,
and showed that propeller ice accretion and resulting propeller
efficiency loss is greater in SLD compared to appendix C conditions.
---------------------------------------------------------------------------
\10\ NTSB Investigation No. DFCA01MA031, Embraer EMB-120 Zero
Injury Incident Near West Palm Beach, Florida on March 19, 2001,
http://www.ntsb.gov.
\11\ FAA Data Report DOT/FAA/AR-06/60, Propeller Icing Tunnel
Test on a Full-Scale Turboprop Engine, dated March 2010. A copy of
this report is available in the rule Docket No. FAA-2010-0636.
---------------------------------------------------------------------------
After further consideration, we have revised Sec. 25.929 to
require a means to prevent or remove hazardous ice accumulations that
could form in the icing conditions defined in appendix C and the
portions of appendix O for which the airplane is approved for flight.
As compared to the NPRM, the phrase ``defined in appendices C and O''
has been replaced with ``defined in appendix C and in the portions of
appendix O of this part for which the airplane is approved for
flight.''
A private citizen commented that the words ``would jeopardize
engine performance'' in the last portion of Sec. 25.929(a) makes this
requirement specific to engine performance. The commenter requested
that the words be stricken from the regulation. The commenter did not
provide justification to substantiate his proposed change.
We do not agree. First, we did not propose a change to this portion
of the rule. Second, we reviewed the wording presented by the IPHWG and
agree with its intent and its phrasing. Its applicability is broader
than just an engine rule. We did not change the rule based on this
comment.
[[Page 65517]]
Engine and Engine Installation Requirements
The RAA commented that current facilities lack the capability to
test large turbofans at very cold temperatures, and, while new sites
may come on-line in the future, such facilities could not be
constructed to comply with the proposed test conditions. The RAA also
pointed out that future airplanes would not be certified for operations
below zero degrees Fahrenheit when ``freezing fog'' is present, so it
would create a restriction to what is currently considered a safe
operating condition.
Airbus, AIA, Boeing, GAMA, GE, and a private citizen suggested that
the choice of ambient temperature for the ground freezing fog rime
icing demonstration should be driven by critical point analysis, as
required by Sec. 33.68(b)(1). This analysis could also be used to show
that a more critical point does not exist at temperatures below the
Table 1, condition 2, test temperatures in Sec. 33.68. Airbus, AIA,
Boeing, GAMA, GE, a private citizen, and RAA further suggested that the
applicant should be permitted to use analysis to demonstrate safe
operation of the engine at temperatures below the required test
demonstration temperature. If safe operation is shown by this analysis,
a temperature limitation would not be required for the AFM.
Airbus also suggested a further change to Sec. 25.1093(b)(2) to
ensure that the test is performed in accordance with aircraft
procedures to provide adequate conservatism. These procedures are
defined in collaboration with the engine manufacturer and may be
defined on the basis of engine certification or development test
results.
EASA and the FAA have recently addressed cold ground fog
conditions. Specifically, the choice of ambient temperature for the
ground freezing fog rime icing demonstration should be driven by
critical point analysis (as required by Sec. 33.68(b)(1)). We
determined this analysis may also be used to show that at colder
temperatures below the Table 1, condition 2, test temperatures in Sec.
33.68, a more critical point does not exist. The analysis may also be
used to demonstrate safe operation of the engine at temperatures below
the required test demonstration. If an applicant does not show
unlimited cold temperature operation, then the minimum ambient
temperature that was demonstrated through test and analysis should also
be a limitation. Finally, the acceleration to takeoff power or thrust
should be accomplished in accordance with the procedures defined in the
AFM. As a result, we changed Sec. Sec. 25.1093(b)(2) and 25.1521(c)(3)
based on these comments, to reflect these changes and recent
developments with EASA.
AIA, GAMA, and a private citizen commented that the MVD for high
LWC in Table 2 of Sec. 33.68 may be difficult to achieve in practice
due to icing facility constraints, and may result in repetitive
equivalent level of safety (ELOS) findings. Expanding the upper limits
of droplet size ranges will allow flexibility in test demonstrations.
An upper limit of 30 microns for glaze ice conditions (points 1 and 3
in Table 1) and 23 microns for rime ice conditions (point 2 in Table 1)
can be accepted if the critical point analysis shows that the engine is
tested to equivalent or greater severity.
AIA, GAMA, and a private citizen also suggested changes to the drop
diameters in Table 1 of Sec. 33.68, noting that practical application
of the required conditions dictates a wider acceptable droplet diameter
range, without measurably impacting the severity of the intended engine
test demonstration.
We agree. Although the commenters did not provide any data to
validate the suggested change in drop diameters, we are aware of test
facility limitations, and concur that the upper tolerance of drop size
is limiting for some test facilities. As a result, the proposed 3 micron droplet tolerance has been removed and a range for the
MVDs is specified instead. This will still provide an adequate safety
margin. Likewise, the upper drop size limit has also been increased to
represent current test facility capabilities while preserving an
adequate safety margin. Section 33.68, Table 1, has been revised to
reflect these changes.
AIA and GAMA also suggested that the ground test conditions in
Table 1, condition (iii), of Sec. 25.1093 and Table 2, condition 4, of
Sec. 33.68(d) should have a consistent range of droplet sizes based on
the values from part 25, appendix O.
We agree. We changed Table 2, condition 4, in Sec. 33.68 by
removing the maximum drop diameter so it is consistent with Table 1,
condition (iii), in Sec. 25.1093. Table 2 in Sec. 33.68 was also
revised to correct the conversion of degrees Centigrade to degrees
Fahrenheit.
A private citizen remarked that including parenthetical examples in
the rule text of Sec. 33.68(a)(3) was not helpful and may be construed
to be exclusionary of other pertinent, topical considerations.
Furthermore, their absence does not diminish the clarity or
understanding of the requirement.
We agree. We removed the parenthetical examples from the regulatory
text in Sec. 33.68.
A private citizen suggested a word change to our proposed wording
of Sec. 33.68(d). In the NPRM, we proposed to change Sec. 33.68(d) to
state that the engine should be run at ground idle speed for a minimum
of 30 minutes in each of the icing conditions shown in Table 2. The
commenter suggested replacing the phrase ``should be run'' with ``must
demonstrate the ability to acceptably operate.'' The commenter noted
that use of the word ``should'' is ambiguous and contrary to existing
Sec. 33.68, which uses the word ``must.'' Furthermore, the commenter
suggested that eliminating the word ``run'' would be more consistent
with the demonstration methods for snow, ice, and large drop glaze ice
conditions (i.e., test, analysis, or combination of both) shown in
Table 2 of Sec. 33.68.
We agree and have clarified Sec. Sec. 25.1093(b)(2) and 33.68(d)
to state that the engine must operate at ground idle speed in the
specified icing conditions.
Alternatives to Rulemaking
Several commenters said that operational solutions have proven to
be extremely effective in managing weather related risks (e.g.,
thunderstorms and windshear). They suggested that the FAA should have
been, or should start, placing at least as much emphasis on advancing
alternatives to rulemaking as it does on creating new certification
requirements. ALPA encouraged continuous research and development of
technical systems that would automatically detect the presence of
hazardous ice, measure the rate of accumulation, and then alert the
crew as appropriate to take action in order to avoid a potentially
unsafe flight condition. AirDat, LLC, commented that the FAA may have
overlooked state-of-the-art meteorological tools, including airborne
sensors, that are commercially available today, fully deployed, and in
operation. AIA, Airbus, Boeing, and GAMA commented that the IPHWG did
not thoroughly consider any alternatives to new rulemaking because the
tasking statement did not include this option.
We agree in part. We agree that careful operations and new
technologies may often enhance safety. However, we note that rulemaking
is at the discretion of the agency, and we have exercised our
discretionary rulemaking authority in this instance. This rule provides
additional safety for the flying public when icing conditions are
encountered, and it will improve the level of safety of future airplane
designs.
[[Page 65518]]
Applicability of Mixed Phase and Ice Crystal Conditions to Airspeed
Indicating Systems
We received several comments suggesting that the mixed phase and
ice crystal environment in part 33, appendix D, should be used instead
of the mixed phase and ice crystal environment that was proposed in
Table 1 of Sec. 25.1323. AIA, Airbus, Boeing, and GAMA stated the NPRM
acknowledged new information is available to guide development of an
ice crystal envelope appropriate for evaluation of airspeed indication
systems. They also noted that proposed Table 1 of Sec. 25.1323 does
not reflect the current understanding of the ice crystal environment,
nor does it include known pitot icing events, which are published in
``Interim Report no. 2,'' Bureau D'Enquetes et D'Analyses pour la
securite d'aviation civile (BEA) F-GZCP.\12\ GSIS recommended that
Table 1 of Sec. 25.1323, which defines a subset of part 33, appendix
D, conditions, should be removed. Instead, the rule should require that
airspeed indication systems must not malfunction in any of the
conditions specified in appendix D.
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\12\ This report can be found on the BEA Web site at http://www.bea.aero/docspa/2009/f-cp090601e2.en/pdf/f-cp090601e2.en.pdf.
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EASA stated that the proposed environment in Table 1 of Sec.
25.1323 would not address known events of airspeed indicating system
malfunctions. EASA also fully supported including in part 25, the
proposed mixed phase and ice crystal parameters in proposed part 33,
appendix D. TCCA suggested that the FAA reconsider the icing conditions
for the airspeed indicating system proposed in the NPRM within Table 1
of Sec. 25.1323 and include the -60 [deg]C conditions described in
part 33, appendix D, instead.
Airbus supported the application of appendix D icing conditions to
pitot and pitot-static probes, but pointed out it is necessary to
develop an acceptable means of compliance that takes into account the
capabilities of the existing engineering tools (for example, models and
icing tunnels) and provide guidance on these new requirements. GSIS
also commented that recent testing suggests testing at sea level
atmospheric conditions may not be a conservative assumption for ice
crystal testing.
NRC noted the requirements of Sec. 25.1323 do not appear to take
into account the effects of displacing the free stream ice water
content around the fuselage of the airplane. If the probe is in a
region affected by this, then the concentration detected by the probe
would be higher than that of the free stream. Airbus mentioned that one
test facility has made significant improvements in its capability to
reproduce icing conditions but it is limited by the size of the test
article it can accommodate. However, no test facilities are currently
capable of reproducing the full range of icing conditions and flight
conditions required by part 33, appendix D. Considering the state of
the art of the engineering tools, there is a need for an agreed means
of compliance.
We agree that the mixed phase and ice crystal environment in part
33, appendix D, should be used instead of the mixed phase and ice
crystal environment proposed in Table 1 of Sec. 25.1323. Therefore,
Sec. Sec. 25.1323 and 25.1324 have been revised to add a requirement
to prevent malfunctions in the mixed phase and ice crystal environment
defined in part 33, appendix D.
With regard to comments suggesting that testing at sea level
atmospheric conditions may not be a conservative assumption, or that
ice crystal concentrations at an exterior mounted probe could be higher
than the free stream conditions, we agree. The conditions defined in
part 33, appendix D, are atmospheric conditions. These atmospheric
conditions include parameters for total water content as a function of
temperature, altitude, and horizontal extent. We also agree that
altitude may be an important parameter. Altitude is a parameter
identified in part 33, appendix D, and must be considered when
developing the test conditions and supporting analysis necessary to
show compliance.
We also agree that depending on airplane size and the location of
the probe, the ice water content at the probe may be higher than the
ice water content values defined in part 33, appendix D. Since part 33,
appendix D, describes atmospheric conditions, the potential for higher
ice crystal concentrations at the probe location compared to the
atmospheric concentrations defined in part 33, appendix D, must be
considered when developing the test conditions and supporting analysis
necessary to show compliance. Installation effects could be evaluated
with a combination of computational fluid dynamics codes and icing
tunnels. Devices mounted on smaller surfaces could be assessed in an
icing tunnel. However, if the device is mounted on the fuselage and
tunnel blockage effects would preclude a meaningful icing tunnel test,
then codes that adequately predict the shadowing and concentration
effects may be acceptable compliance methods.
Foster Technology, LLC (Foster), is an engineering consulting firm
that has filed a provisional patent that includes a methodology for
detecting ice over a pitot inlet, providing a corrected airspeed, and
removing ice deposits. Foster suggested that the FAA should certify its
new methodology.
We agree that existing regulations would allow certification of a
new pitot probe with ice detection capability. However, we would
certify a new pitot probe as part of a product's type design to be
approved for installation, not the methodology described by Foster. If
Foster seeks independent certification of a new pitot probe, we suggest
Foster complete and submit an application for a supplemental type
certificate, at which time we will evaluate the new probe.
Heavy Rain Requirements for Airspeed Indication and Angle of Attack
Systems
Airbus and EASA fully supported a new requirement to cover the
heavy rain conditions being considered in the NPRM. Airbus commented
that some testing at high LWCs, such as those proposed in the NPRM,
would help to ensure that water drainage in rain conditions, especially
at takeoff, is adequate. A private citizen commented that the maximum
freezing rain static temperature under consideration would be unlikely
to result in ice accretion and is not in line with figure 4 of appendix
O. AIA, Boeing, and GAMA commented that the proposed expanded
parameters, the source of which was not provided, do not appear
congruous with hard data from extensive icing research. GSIS commented
that it wanted to understand how the specific values for LWC,
horizontal extent, and mean droplet diameter were determined and what
the technical justifications are for these levels.
We consider analysis of heavy rain conditions as proposed in the
NPRM to be necessary to substantiate that water drainage from the
airspeed indication and angle of attack systems is adequate. If the
water drainage is inadequate, then the residual water may freeze as the
pitot probes or angle of attack sensors are subjected to below freezing
temperatures as the airplane climbs following takeoff. The heavy rain
conditions are not intended as an icing condition as described in the
NPRM. The heavy rain LWC is based on heavy rainfall data documented in
MIL-STD-210C, Military Standard: Climatic Information to Determine
Design and Test Requirements for Military Systems
[[Page 65519]]
and Equipment.\13\ The same rain data was used for the AIA Propulsion
Committee Study, Project PC 338-1 documented in part 33, appendix B.
Heavy rain conditions have been added to Sec. Sec. 25.1323 and
25.1324. However, the conditions have been revised compared to the
conditions proposed in the NPRM by removing temperature as a parameter.
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\13\ A copy of MIL-STD-210C, dated January 9, 1987, is available
in the rule Docket No. FAA-2010-0636. MIL-STD-210 has since been
superseded by MIL-HDBK-310, dated June 23, 1997, which is also
available in the rule docket.
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Applicability of the Icing Requirements in Part 25, Appendix O, and
Part 33, Appendix D, to All Airspeed Indicating Systems
EASA and TCCA suggested that Sec. Sec. 25.1323 and 25.1324 be
revised to include the icing certification of all external probes for
flight instruments. EASA proposed a specific regulation including, but
not limited to, pitot, pitot-static, static, angle-of-attack, sideslip
angle, and temperature sensors. The regulation proposed by EASA would
require addressing the icing conditions in part 25, appendix C; part
25, appendix O; and part 33, appendix D. Similarly, since total air
temperature (TAT) is an input to calculating true airspeed, Goodrich
requested clarification of whether or not TAT sensors should be
considered part of the airspeed indicating system when addressing
``preventing malfunction'' in part 25, appendix O, and part 33,
appendix D, environments as described in Sec. 25.1323(i).
We do not agree with the commenters' suggestions to include icing
requirements for all external probes and sensors in Sec. Sec. 25.1323
and 25.1324. Section 25.1323(i) has traditionally applied to pitot
probes (indicated airspeed), and the FAA did not propose a change to
this applicability in the NPRM. As such, we did not intend to include
TAT sensors, or other externally mounted instrument probes in Sec.
25.1323(i). In addition, Sec. 25.1324 was proposed specifically for
angle-of-attack sensors. Revising Sec. Sec. 25.1323 and 25.1324 so
that all externally mounted flight instrument probes and sensors must
operate in the various icing conditions is beyond the scope of this
rulemaking. We did not change the rule in response to these comments.
Proposal To Add Indication System for External Probes
EASA advised that some failures of the pitot probe heating
resistance may not be seen by the flightcrew due to the low current
detection system installed on the airplane. As a result, failure to
provide proper pitot probe deicing may not be detected. EASA suggested
that a new regulation be created to explicitly cover abnormal
functioning of the heating system for externally mounted probes.
We do not agree. If insufficient functioning of an externally
mounted probe creates an unsafe operating condition, then warning
information must be provided to the flightcrew in accordance with Sec.
25.1309(c). Since we did not propose warning information specific to
failure modes for certain externally mounted probes in the NPRM and the
public did not have the opportunity to comment, we consider the EASA
proposal to be beyond the scope of this rulemaking. No changes to the
final rule have been made as a result of EASA's proposal.
Expand the Parameters for Part 33, Appendix D
AIA, Boeing, and GAMA commented that part 33, appendix D, should be
expanded to reflect new engine power loss and airspeed data loss events
in ice crystal conditions. Appendix D is based on a theoretical model,
and Airbus agreed that the conditions in appendix D should be applied.
We do not agree that appendix D should be expanded in this final
rule. The majority of recent airspeed data anomalies occurred within
the altitude and temperature range described in part 33, appendix D. We
know of only one temporary loss of airspeed data event just outside or
at the perimeter of the altitude and temperature range in part 33,
appendix D. Other conditions described in appendix D, such as what the
ice water content actually was during the loss of airspeed data event,
are unknown because it was not measured. We agree that appendix D is
based on a theoretical atmospheric model. We are continuing to support
the research necessary to validate the part 33, appendix D, conditions
with flight test data, and it would be premature to expand the appendix
D environment at this time. Expansion of part 33, appendix D, is out of
scope of the originally proposed rulemaking. We did not change appendix
D based on these comments.
Airbus commented that using the EHWG event database and referring
to the flight distance between a TAT sensor anomaly and the engine
event, one can see that almost half of the engine events occurred at a
flight distance equal to or less than 10 nautical miles from the
occurrence of the TAT anomaly, with the majority of events happening
within less than 4 nautical miles. Based on these facts, Airbus
concluded that short cloud exposures are the most critical. However,
the new appendix D definition implies that the longest clouds are the
most critical for engines and auxiliary power units (APUs), and adds a
factor of 2 to the conservatism of the definitions already defined in
EASA documents CS-E 780, Tests in Ice-Forming Conditions, and AMC
25.1419, Ice Protection.\14\ Airbus commented that it is inappropriate
to add an additional factor of 2 to the icing conditions for long
exposures in appendix D icing conditions considering the uncertainty in
the new rule.
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\14\ Both of these documents are available on the EASA Web site
at http://www.easa.europa.eu.
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We do not agree. We acknowledge that a TAT sensor anomaly may be
one indicator of ice crystals; however, it is not a very reliable
indicator. The amount and concentration of ice crystals required to
create a TAT sensor anomaly is not understood. Also, the TAT sensor
anomaly was only present in a portion of the engine events in the EHWG
database. Therefore, the TAT anomaly data cannot accurately show cloud
extent. Additionally, detailed review of the event data indicated that
once the TAT probe iced over enough to cause an indication anomaly, the
engine often would demonstrate a power upset very soon after the TAT
probe anomaly. This period of time was insufficient for the pilot to
take action since the ice accretion within the engine had already
progressed to an advanced stage. Therefore, we concluded that TAT probe
anomalies are poor precursor indications of the ice crystal threat to
engines, in terms of reliability of the indication and the time period
in advance of power loss. When establishing the cloud extent factor in
part 33, appendix D, the EHWG and FAA did take into account EASA CS-E-
780 cloud definition requirements. However, the EHWG was not able to
validate the analysis used to develop the cloud extent factor in EASA
CS-E-780. The cloud extent factor proposed by the EHWG for part 33,
appendix D, represents the most accurate cloud extent factor that can
be established using the available data. No changes were made as a
result of these comments.
Snecma commented that the y-axis value in proposed part 33,
appendix D, figure D3, was incorrect. The value should be 0.6 but the
NPRM showed the value as zero.
We concur. We also found that both the x- and y-axis values
proposed in the NPRM were incorrect. We changed part
[[Page 65520]]
33, appendix D, figure D3, to depict the correct axis values. The
lowest x-axis value is now 1 and the lowest y-axis value is now 0.6.
Several commenters noted that the horizontal cloud length proposed
in the NPRM was stated in statute miles, and commented it should be
provided in nautical miles. The commenters suggested that changing to
nautical miles would make the distance measurement consistent with
other tables and figures in appendix D.
We agree, and changed Table 1 to identify that the horizontal cloud
length is depicted in nautical miles.
Several commenters asked why we included the reference to
``Reference 1'' in the text immediately following Table 1 in proposed
part 33, appendix D, especially considering the material constituting
``Reference 1'' was not identified anywhere within the NPRM.
We agree. We removed the reference to ``Reference 1'' from the
final rule.
Establishing New Operating Limitations
TCCA stated that it was not clear if the proposed requirements to
exit all icing conditions were applicable only to in-flight icing
encounters, or if they were also applicable to the takeoff phase of
flight.
We agree that clarification is needed. We changed Sec. 25.1533(c)
to clarify that the additional limitations apply to all phases of
flight.
Additional Requirements for Safe Operation
AIA, Boeing, and GAMA commented that proposed appendix O, paragraph
(b) does not define takeoff ice accretions for airplanes not certified
for takeoff in appendix O conditions. Therefore, they suggested that
Sec. 25.207(e)(1), which defines stall warning requirements for
takeoff with ice accretions, should be added to the list of exceptions
specified in Sec. 25.21(g)(3).
We agree. We added the stall warning requirements in Sec.
25.207(e)(1) to the exceptions listed in Sec. 25.21(g)(3). As a
result, applicants will not need to determine the stall warning margin
for takeoff with appendix O ice accretions for airplanes not certified
to take off in appendix O icing conditions.
TCCA commented that exposure to appendix O icing conditions may
result in icing accretions further aft on fuselage, wing and stabilizer
surfaces, and control surfaces, beyond what would normally be obtained
in appendix C conditions. Therefore, TCCA suggested that compliance to
Sec. 25.251(b) through (e) should be shown for appendix O conditions.
We proposed to retain the provision from Amendment 25-121 for not
requiring compliance with Sec. 25.251(b) through (e) in appendix C
icing conditions and extend it to include appendix O icing conditions.
Although Amendment 25-121 only addressed appendix C icing conditions,
the conclusion that compliance to Sec. 25.251(b) through (e) need not
be shown in icing conditions was based on a review of in-service
experience in all icing conditions, not just appendix C icing
conditions. Therefore, including Sec. 25.251(b) through (e) within the
exceptions listed in Sec. 25.21(g) for certifications is equally
applicable to either appendix C or appendix O conditions. No changes
were made to the final rule as a result of this comment.
Dassault commented that the proposed ice accretion definitions in
part II of appendix O did not include an ice accretion specific to the
flight phase covered by Sec. 25.121(a). Dassault added that the ice
accretion used for showing compliance with Sec. 25.121(a)(1) should be
the accretion occurring between liftoff and the point at which the
landing gear is fully retracted. Dassault requested that the FAA add
the following definition: ``Takeoff--landing gear extended ice is the
most critical ice accretion on unprotected surfaces, and any ice
accretion on protected surfaces appropriate to normal ice protection
system operation, occurring between liftoff and the point at which the
landing gear is fully retracted, assuming accretion starts at liftoff
in the icing conditions defined in Part I of this appendix.''
Instead of adding a definition for the ice accretion during the
initial takeoff segment covered by Sec. 25.121(a), we have
reconsidered this issue and determined that this flight segment does
not last long enough for significant ice accretions to occur, even in
appendix O icing conditions. Therefore, we added Sec. 25.121(a) to the
list of requirements in Sec. 25.21(g)(4) that do not have to be met
with appendix O ice accretions. We also agree that our proposed
definition for takeoff ice was inadequate. We did not intend to require
that applicants include the small effect (if any) of ice accretion from
the point of liftoff to the end of the takeoff distance in determining
the takeoff distance under Sec. 25.113, which the appendix C
definition and the proposed appendix O definition may have implied.
Therefore, we revised the definitions of takeoff ice and final takeoff
ice in part 25, appendix C and appendix O, such that the ice accretion
begins at the end of the takeoff distance, not at the point of liftoff.
This change better aligns the definition of the takeoff and final
takeoff ice with that of the takeoff path used for determining takeoff
performance under Sec. Sec. 25.111, 25.113, and 25.115.
Request To Revise Sec. 25.629
TCCA commented that for airplanes exempt from Sec. 25.1420, no
evaluation of aeroelastic stability is required in appendix O icing
conditions. For that reason, TCCA recommended that all icing
considerations be included directly in Sec. 25.629.
We do not agree. Section 25.629(b)(1) requires aeroelastic
stability evaluations of the airplane in normal conditions. For
airplanes approved for operation in icing conditions, ice accumulations
are considered a normal condition under the rule. Since Sec. 25.629
does not specifically distinguish between various types of icing
conditions, all icing conditions for which the airplane is approved are
considered normal conditions. For airplanes exempt from Sec. 25.1420,
or for which approval is not sought for flight in appendix O icing
conditions, Sec. 25.629(d)(3) requires that ice accumulations due to
inadvertent icing encounters must be considered for airplanes not
approved for operation in icing conditions. The intent is to consider
ice accumulations due to inadvertent icing encounters from any icing
conditions for which the airplane is not approved, including appendix O
conditions. We did not change the rule as a result of this comment.
Miscellaneous Issues
After the FAA issued the NPRM to this rulemaking, we issued a final
rule for Harmonization of Various Airworthiness Standards for Transport
Category Airplanes--Flight Rules (docket number FAA-2010-0310). That
final rule revised Sec. 25.21(g)(1) to add the requirement that the
stall warning margin requirements of Sec. 25.207(c) and (d) must be
met in the landing configuration in the icing conditions of appendix C.
That final rule also revised Sec. 25.253(c) to define the maximum
speeds at which the static lateral-directional stability requirements
of Sec. 25.177(a) through (c) and the directional and lateral control
requirements of Sec. 25.147(f) must be met in the icing conditions of
appendix C. We have retained those changes in Sec. Sec. 25.21(g)(2)
and 25.253(c) of this final rule. For consistency, we also revised
Sec. 25.21(g)(4) to require that Sec. 25.207(c) and (d) must be met
in the landing configuration in the appendix O icing conditions for
which certification is sought. This revision is a logical outgrowth of
the notice in this
[[Page 65521]]
rulemaking because the purpose of Sec. 25.21(g)(4) is to ensure safe
operation in appendix O conditions during all phases of flight,
including the landing phase.
The FAA finds that clarifying the applicability of the proposed
icing conditions to APU installations is necessary. Section 25.901(d)
currently requires that each auxiliary power unit installation must
meet the applicable provisions of the subpart. This requirement is
unchanged by this rulemaking. The FAA considers Sec. 25.1093(b) to be
applicable to APU installations because they are turbine engines. An
essential APU is used to provide air and/or power necessary to maintain
safe airplane operation. A non-essential APU is used to provide air
and/or power as a matter of convenience and may be shutdown without
jeopardizing safe airplane operation. The FAA has traditionally
required that essential APU installations continue to operate in part
25, appendix C, icing conditions. Non-essential APU installations
either have restricted operation or are required to demonstrate that
operation in icing conditions does not affect the safe operation of the
airplane. References to part 25, appendix O, and part 33, appendix D,
have been added to Sec. 25.1093(b).
As previously discussed, the applicability of appendix O conditions
in Sec. 25.1093(b) excludes all turbine engine installations that are
used on airplanes with a MTOW equal to or greater than 60,000 pounds.
The FAA still considers APUs to be turbine engines that must comply
with the installation requirements in Sec. Sec. 25.901 and 25.1093;
therefore, this rulemaking is not creating separate requirements for
APU installations. Essential APU installations must continue to operate
in the icing conditions applicable under Sec. 25.1093(b). Non-
essential APU installations must not affect the safe operation of the
airplane when the icing conditions applicable under Sec. 25.1093(b)
are inadvertently encountered.
Also as previously discussed, the applicability of appendix O
conditions in Sec. 25.1093(b) was revised to provide relief for larger
airplanes because of the successful in-service history of existing
larger airplane and larger airplane turbine engine inlet designs. If
future APU installations contain novel or unusual design features that
affect this successful in-service history, and those design features
make the airplane more susceptible to the effects of flight in SLD
icing conditions, the FAA can issue special conditions to provide
adequate safety standards.
A private citizen identified potential flightcrew training issues
associated with this rulemaking. The commenter noted that while
practical test standards for post-stall recovery procedures are clearly
related to icing safety, they are not regulatory and may be changed
without formal notice. The commenter also remarked that a common pilot
input characteristic to add power and maintain the pitch angle of the
airplane has been observed on the flight data recorder time histories
related to several icing related accidents. In some cases, nose up
pitch input was applied even against the nose down force being applied
by the airplane's ``stick pusher'' that is designed to rapidly reduce
the angle of attack. The commenter noted that these habit patterns are
developed and reinforced as the required response in simulator training
in accordance with FAA practical test standards for stall
identification and recovery for minimum altitude loss. For example,
``Minimum altitude loss'' is trained as ``zero altitude loss.''
The flightcrew training issues addressed by the commenter are
important safety considerations. However, flightcrew training is beyond
the scope of this rulemaking because this rulemaking addresses design
requirements. On July 6, 2010, the FAA published Safety Alert for
Operators (SAFO) 10012. The SAFO discusses the possible
misinterpretation of the practical test standards language ``minimal
loss of altitude.'' \15\
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\15\ This document can be found at http://www.faa.gov/other_visit/aviation_industry/airline_operators/airline_safety/safo/all_safos/media/2010/SAFO10012.pdf.
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In addition, on September 30, 2010, the FAA established the Stick
Pusher and Adverse Weather Event Training Aviation Rulemaking
Committee. One of the rulemaking committee objectives is to identify
the best goals, procedures, and training practices that will enable air
carrier pilots to accurately and consistently respond to unexpected
stick pusher activations, icing conditions, and microburst and
windshear events.\16\ The ARC has submitted recommendations to the FAA,
which are being considered for additional rulemaking activities. Such
activities are beyond the scope of this rulemaking.
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\16\ A copy of the charter is available at http://www.faa.gov/about/office_org/headquarters_offices/avs/offices/afs/afs200/media/208_ARC_Charter.pdf.
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Regulatory Notices and Analyses
Regulatory Evaluation
Changes to Federal regulations must undergo several economic
analyses. First, Executive Order 12866 and Executive Order 13563 direct
that each Federal agency shall propose or adopt a regulation only upon
a reasoned determination that the benefits of the intended regulation
justify its costs. Second, the Regulatory Flexibility Act of 1980 (Pub.
L. 96-354) requires agencies to analyze the economic impact of
regulatory changes on small entities. Third, the Trade Agreements Act
(Pub. L. 96-39) prohibits agencies from setting standards that create
unnecessary obstacles to the foreign commerce of the United States. In
developing U.S. standards, this Trade Act requires agencies to consider
international standards and, where appropriate, that they be the basis
of U.S. standards. Fourth, the Unfunded Mandates Reform Act of 1995
(Pub. L. 104-4) requires agencies to prepare a written assessment of
the costs, benefits, and other effects of proposed or final rules that
include a Federal mandate likely to result in the expenditure by State,
local, or tribal governments, in the aggregate, or by the private
sector, of $100 million or more annually (adjusted for inflation with
base year of 1995). This portion of the preamble summarizes the FAA's
analysis of the economic impacts of this final rule. We suggest readers
seeking greater detail read the full regulatory evaluation, a copy of
which we have placed in the docket for this rulemaking.
In conducting these analyses, the FAA has determined that this
final rule: (1) Has benefits that justify its costs, (2) is not an
economically ``significant regulatory action'' as defined in section
3(f) of Executive Order 12866, (3) is ``not significant'' as defined in
DOT's Regulatory Policies and Procedures; (4) will not have a
significant economic impact on a substantial number of small entities;
(5) will not create unnecessary obstacles to the foreign commerce of
the United States; and (6) will not impose an unfunded mandate on
state, local, or tribal governments, or on the private sector by
exceeding the threshold identified above. These analyses are summarized
below.
Total Benefits and Costs of This Final Rule
[[Page 65522]]
Table 1--Total Benefits and Costs of This Rule
----------------------------------------------------------------------------------------------------------------
2012$ 7% Present value
----------------------------------------------------------------------------------
Benefit Cost Benefit Cost
----------------------------------------------------------------------------------------------------------------
Part 33 Engines.............. Qualitative.......... $13,936,000 Qualitative......... $11,375,927
Large Part 25 Airplanes...... $362,319,857......... 14,126,333 $76,861,295......... 11,531,295
Other Part 25 Airplanes...... $220,570,582......... 33,198,788 $50,028,650......... 19,385,401
----------------------------------------------------------------------------------
Total.................... $582,890,439......... 61,261,121 $126,889,985........ 42,292,624
----------------------------------------------------------------------------------------------------------------
* Details may not add to row or column totals due to rounding.
Persons Potentially Affected by This Final Rule
Part 25 airplane manufacturers,
Engine manufacturers, and
Operators of affected equipment.
Assumptions
The deliveries and affected fleets are analyzed over appropriate
time periods and are customized based upon actual historical data. The
fleet development is customized to the various (and different) airplane
types. We conservatively assume that all certifications will occur in
2015 and deliveries will occur in the following year. As production
time spans differ by size of airplane, it is important for the reader
to focus on present value benefits and costs.
Present Value Discount rate--7%
Value of an Averted Fatality--$9.1 million in 2012
Both Costs and Benefits are expressed in 2012 dollars.
Benefits of This Final Rule
The FAA has analyzed events that would have been prevented if this
final rule were in place at the time of certification. The events were
evaluated for applicability and preventability in context with the
requirements contained in this final rule.
For the categories of airplanes, first, we develop casualty rates
for fatalities, injuries, investigations, and destroyed airplanes based
on historical ice-related accidents. Next, we multiply the total annual
affected airplanes by the annual risk per airplane. Lastly, we multiply
the casualty rates by the projected number of part 25 newly
certificated deliveries. When summed over time, the total estimated
benefits are shown in Table 1.
Viewed from a breakeven analysis using only preventable fatalities,
with each fatality valued at $9.1 million, this rule has benefits
exceeding costs with only 7 fatalities prevented.
Costs of This Final Rule
The total estimated costs are shown in Table 1. We obtained the
basis of our cost estimates from the industry. Since the NPRM, we have
modified the estimates based upon industry comments and clarifications
to those comments. The compliance costs are analyzed in context of the
part 25 and part 33 certification requirements.
As summarized in Table 2, the cost categories in the regulatory
evaluation incorporate both certification and operational costs. We
analyze each cost category separately. The cost categories in this
evaluation are the same as those provided by industry to comply with
the requirements contained in this rule.
Table 2--Cost Summary
------------------------------------------------------------------------
Nominal cost 7% PV cost
------------------------------------------------------------------------
Engine Certification Cost......... $7,936,000 $6,478,140
Engine Capital Cost............... 6,000,000 4,897,787
-------------------------------------
Total Engine Cost............. 13,936,000 11,375,927
-------------------------------------
New Large Airplane Certification 14,126,333 11,531,295
Cost.............................
Large Airplane Hardware Cost...... 0 0
Large Airplane Fuel Cost.......... 0 0
-------------------------------------
Total Large Airplane Cost..... 14,126,333 11,531,295
-------------------------------------
Other Airplane Certification Cost. 19,066,026 15,563,557
Other Airplane Hardware Cost...... 2,475,000 1,312,609
Other Airplane Fuel Burn Cost..... 11,657,762 2,509,236
-------------------------------------
Total Other Airplane Costs.... 33,198,788 19,385,401
------------------------------------------------------------------------
Total Costs............... 61,261,121 42,292,624
------------------------------------------------------------------------
* Details may not add to row or column totals due to rounding.
Alternatives Considered
Alternative 1--Make the entire rule applicable to all airplanes.
Not all the requirements in this rule extend to large transport
category airplanes (those with a MTOW greater than 60,000 pounds).
Under this alternative, the proposed design requirements would extend
to all transport category airplanes. This alternative was rejected
because this alternative would add significant costs without a
commensurate increase in benefits.
Alternative 2--Limit the scope of applicability to small transport
category airplanes.
Although this alternative would decrease the estimated cost, the
FAA believes that medium and large airplanes are at risk of an SLD
icing
[[Page 65523]]
event. The FAA does not want a significant proportion of the future
fleet to be disproportionately at risk.
Regulatory Flexibility Determination
The Regulatory Flexibility Act of 1980 (Pub. L. 96-354) (RFA)
establishes as a principle of regulatory issuance that agencies shall
endeavor, consistent with the objectives of the rule and of applicable
statutes, to fit regulatory and informational requirements to the scale
of the businesses, organizations, and governmental jurisdictions
subject to regulation. To achieve this principle, agencies are required
to solicit and consider flexible regulatory proposals and to explain
the rationale for their actions to assure that such proposals are given
serious consideration. The RFA covers a wide-range of small entities,
including small businesses, not-for-profit organizations, and small
governmental jurisdictions.
Agencies must perform a review to determine whether a rule will
have a significant economic impact on a substantial number of small
entities. If the agency determines that it will, the agency must
prepare a regulatory flexibility analysis as described in the RFA.
However, if an agency determines that a rule is not expected to
have a significant economic impact on a substantial number of small
entities, section 605(b) of the RFA provides that the head of the
agency may so certify and a regulatory flexibility analysis is not
required. The certification must include a statement providing the
factual basis for this determination, and the reasoning should be
clear. Our initial determination was that the proposed rule would not
have a significant economic impact on a substantial number of small
entities. We received no public comments regarding our initial
determination. As such, this final rule will not have a significant
economic impact on a substantial number of small entities for the
following reasons.
Airplane and Engine Manufacturers
Airplane and engine manufacturers will be affected by the
requirements contained in this rule.
For airplane manufacturers, we use the size standards from the
Small Business Administration for Air Transportation and Aircraft
Manufacturing specifying companies having less than 1,500 employees as
small entities. The current United States part 25 airplane
manufacturers include Boeing, Cessna Aircraft, Gulfstream Aerospace,
Learjet (owned by Bombardier), Lockheed Martin, Raytheon Aircraft, and
Sabreliner Corporation. Because all U.S. transport-category airplane
manufacturers have more than 1,500 employees, none are considered small
entities.
United States aircraft engine manufacturers include General
Electric, CFM International, Pratt & Whitney, International Aero
Engines, Rolls-Royce Corporation, Honeywell, and Williams
International. All but one exceeds the Small Business Administration
small-entity criteria for aircraft engine manufacturers. Williams
International is the only one of these manufacturers that is a U.S.
small business.
The FAA estimated that Williams International engines power
approximately four percent of the engines on active U.S. airplanes.
Assuming that future deliveries of newly certificated airplanes with
Williams International engines will have the same percentage as the
active fleet, we calculated that this final rule will add about 0.2
percent of their annual revenue. We do not consider a cost of 0.2
percent of annual revenue significant.
Operators
In addition to the certification cost incurred by manufacturers,
operators will incur fuel costs due to the estimated additional impact
of weight changes from equipment on affected airplanes. On average,
operators affected by the final rule will incur no additional annual
fuel costs for newly certificated large part 25 airplanes, and $189, in
present value, in additional fuel costs for other newly certificated
part 25 airplanes. This final rule will apply to airplanes that have
yet to be designed; there will be no immediate cost to small entities.
The other airplane annual fuel cost of $189, in present value, is not
significant in terms of total operating expenses. We do not consider
these annual fuel costs a significant economic impact.
This final rule will not have a significant economic impact on a
substantial number of airplane manufacturers, engine manufacturers, or
operators. Therefore, as the FAA Administrator, I certify that this
rule will not have a significant economic impact on a substantial
number of small entities.
International Trade Analysis
The Trade Agreements Act of 1979 (Pub. L. 96-39), as amended by the
Uruguay Round Agreements Act (Pub. L. 103-465), prohibits Federal
agencies from establishing standards or engaging in related activities
that create unnecessary obstacles to the foreign commerce of the United
States. Pursuant to these Acts, the establishment of standards is not
considered an unnecessary obstacle to the foreign commerce of the
United States, so long as the standard has a legitimate domestic
objective, such as the protection of safety, and does not operate in a
manner that excludes imports that meet this objective. The statute also
requires consideration of international standards and, where
appropriate, that they be the basis for U.S. standards.
The FAA has assessed the effect of this final rule and determined
that it will not be an unnecessary obstacle to the foreign commerce of
the United States as the purpose of this rule is to ensure aviation
safety.
Unfunded Mandates Assessment
Title II of the Unfunded Mandates Reform Act of 1995 (Pub. L. 104-
4) requires each Federal agency to prepare a written statement
assessing the effects of any Federal mandate in a proposed or final
agency rule that may result in an expenditure of $100 million or more
(in 1995 dollars) in any one year by State, local, and tribal
governments, in the aggregate, or by the private sector; such a mandate
is deemed to be a ``significant regulatory action.'' The FAA currently
uses an inflation-adjusted value of $143.1 million in lieu of $100
million. This final rule does not contain such a mandate; therefore,
the requirements of Title II do not apply.
Paperwork Reduction Act
The Paperwork Reduction Act of 1995 (44 U.S.C. 3507(d)) requires
that the FAA consider the impact of paperwork and other information
collection burdens imposed on the public. The information collection
requirements associated with this final rule have been previously
approved by the Office of Management and Budget (OMB) under the
provisions of the Paperwork Reduction Act of 1995 (44 U.S.C. 3507(d))
and have been assigned OMB Control Number 2120-0018.
International Compatibility and Cooperation
(1) In keeping with U.S. obligations under the Convention on
International Civil Aviation, it is FAA policy to conform to
International Civil Aviation Organization (ICAO) Standards and
Recommended Practices to the maximum extent practicable. The FAA has
reviewed the corresponding ICAO Standards and Recommended Practices and
has identified no differences with these regulations.
[[Page 65524]]
(2) Executive Order 13609, Promoting International Regulatory
Cooperation, promotes international regulatory cooperation to meet
shared challenges involving health, safety, labor, security,
environmental, and other issues and to reduce, eliminate, or prevent
unnecessary differences in regulatory requirements. The FAA has
analyzed this action under the policies and agency responsibilities of
Executive Order 13609, and has determined that this action will have no
effect on international regulatory cooperation.
Environmental Analysis
FAA Order 1050.1E identifies FAA actions that are categorically
excluded from preparation of an environmental assessment or
environmental impact statement under the National Environmental Policy
Act in the absence of extraordinary circumstances. The FAA has
determined this rulemaking action qualifies for the categorical
exclusion identified in paragraph 4(j) and involves no extraordinary
circumstances.
Regulations Affecting Intrastate Aviation in Alaska
Section 1205 of the FAA Reauthorization Act of 1996 (110 Stat.
3213) requires the FAA, when modifying its regulations in a manner
affecting intrastate aviation in Alaska, to consider the extent to
which Alaska is not served by transportation modes other than aviation,
and to establish appropriate regulatory distinctions. In the NPRM, the
FAA requested comments on whether the proposed rule should apply
differently to intrastate operations in Alaska. The agency did not
receive any comments, and has determined, based on the administrative
record of this rulemaking, that there is no need to make any regulatory
distinctions applicable to intrastate aviation in Alaska.
Executive Order Determinations
Executive Order 13132, Federalism
The FAA has analyzed this final rule under the principles and
criteria of Executive Order 13132, Federalism. The agency determined
that this action will not have a substantial direct effect on the
States, or the relationship between the Federal Government and the
States, or on the distribution of power and responsibilities among the
various levels of government, and, therefore, does not have Federalism
implications.
Executive Order 13211, Regulations That Significantly Affect Energy
Supply, Distribution, or Use
The FAA analyzed this final rule under Executive Order 13211,
Actions Concerning Regulations that Significantly Affect Energy Supply,
Distribution, or Use (May 18, 2001). The agency has determined that it
is not a ``significant energy action'' under the executive order and it
is not likely to have a significant adverse effect on the supply,
distribution, or use of energy.
How To Obtain Additional Information
Rulemaking Documents
An electronic copy of a rulemaking document may be obtained by
using the Internet--
1. Search the Federal eRulemaking Portal (http://www.regulations.gov);
2. Visit the FAA's Regulations and Policies Web page at http://www.faa.gov/regulations_policies/ or
3. Access the Government Printing Office's Web page at http://www.gpo.gov/fdsys/browse/collection.action?collectionCode=FR.
Copies may also be obtained by sending a request (identified by
notice, amendment, or docket number of this rulemaking) to the Federal
Aviation Administration, Office of Rulemaking, ARM-1, 800 Independence
Avenue SW., Washington, DC 20591, or by calling (202) 267-9680.
Comments Submitted to the Docket
Comments received may be viewed by going to http://www.regulations.gov and following the online instructions to search the
docket number for this action. Anyone is able to search the electronic
form of all comments received into any of the FAA's dockets by the name
of the individual submitting the comment (or signing the comment, if
submitted on behalf of an association, business, labor union, etc.).
Small Business Regulatory Enforcement Fairness Act
The Small Business Regulatory Enforcement Fairness Act (SBREFA) of
1996 requires FAA to comply with small entity requests for information
or advice about compliance with statutes and regulations within its
jurisdiction. A small entity with questions regarding this document,
may contact its local FAA official, or the person listed under the FOR
FURTHER INFORMATION CONTACT heading at the beginning of the preamble.
To find out more about SBREFA on the Internet, visit http://www.faa.gov/regulations_policies/rulemaking/sbre_act/.
List of Subjects
14 CFR Part 25
Aircraft, Aviation safety, Reporting and recordkeeping
requirements, Safety, Transportation.
14 CFR Part 33
Aircraft, Aviation safety.
The Amendment
In consideration of the foregoing, the Federal Aviation
Administration amends chapter I of title 14, Code of Federal
Regulations as follows:
PART 25--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES
0
1. The authority citation for part 25 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701, 44702 and 44704.
0
2. Amend Sec. 25.21 by revising paragraphs (g)(1) and (2) and adding
paragraphs (g)(3) and (4) to read as follows:
Sec. 25.21 Proof of compliance.
* * * * *
(g) * * *
(1) Paragraphs (g)(3) and (4) of this section apply only to
airplanes with one or both of the following attributes:
(i) Maximum takeoff gross weight is less than 60,000 lbs; or
(ii) The airplane is equipped with reversible flight controls.
(2) Each requirement of this subpart, except Sec. Sec. 25.121(a),
25.123(c), 25.143(b)(1) and (2), 25.149, 25.201(c)(2), 25.239, and
25.251(b) through (e), must be met in the icing conditions specified in
Appendix C of this part. Section 25.207(c) and (d) must be met in the
landing configuration in the icing conditions specified in Appendix C,
but need not be met for other configurations. Compliance must be shown
using the ice accretions defined in part II of Appendix C of this part,
assuming normal operation of the airplane and its ice protection system
in accordance with the operating limitations and operating procedures
established by the applicant and provided in the airplane flight
manual.
(3) If the applicant does not seek certification for flight in all
icing conditions defined in Appendix O of this part, each requirement
of this subpart, except Sec. Sec. 25.105, 25.107, 25.109, 25.111,
25.113, 25.115, 25.121, 25.123, 25.143(b)(1), (b)(2), and (c)(1),
25.149, 25.201(c)(2), 25.207(c), (d), and (e)(1), 25.239, and 25.251(b)
through (e), must be met in the Appendix O icing conditions for which
certification is not
[[Page 65525]]
sought in order to allow a safe exit from those conditions. Compliance
must be shown using the ice accretions defined in part II, paragraphs
(b) and (d) of Appendix O, assuming normal operation of the airplane
and its ice protection system in accordance with the operating
limitations and operating procedures established by the applicant and
provided in the airplane flight manual.
(4) If the applicant seeks certification for flight in any portion
of the icing conditions of Appendix O of this part, each requirement of
this subpart, except Sec. Sec. 25.121(a), 25.123(c), 25.143(b)(1) and
(2), 25.149, 25.201(c)(2), 25.239, and 25.251(b) through (e), must be
met in the Appendix O icing conditions for which certification is
sought. Section 25.207(c) and (d) must be met in the landing
configuration in the Appendix O icing conditions for which
certification is sought, but need not be met for other configurations.
Compliance must be shown using the ice accretions defined in part II,
paragraphs (c) and (d) of Appendix O, assuming normal operation of the
airplane and its ice protection system in accordance with the operating
limitations and operating procedures established by the applicant and
provided in the airplane flight manual.
0
3. Amend Sec. 25.105 by revising paragraph (a)(2) introductory text to
read as follows:
Sec. 25.105 Takeoff.
(a) * * *
(2) In icing conditions, if in the configuration used to show
compliance with Sec. 25.121(b), and with the most critical of the
takeoff ice accretion(s) defined in Appendices C and O of this part, as
applicable, in accordance with Sec. 25.21(g):
* * * * *
0
4. Amend Sec. 25.111 by revising paragraphs (c)(5)(i) and (ii) to read
as follows:
Sec. 25.111 Takeoff path.
* * * * *
(c) * * *
(5) * * *
(i) With the most critical of the takeoff ice accretion(s) defined
in Appendices C and O of this part, as applicable, in accordance with
Sec. 25.21(g), from a height of 35 feet above the takeoff surface up
to the point where the airplane is 400 feet above the takeoff surface;
and
(ii) With the most critical of the final takeoff ice accretion(s)
defined in Appendices C and O of this part, as applicable, in
accordance with Sec. 25.21(g), from the point where the airplane is
400 feet above the takeoff surface to the end of the takeoff path.
* * * * *
0
5. Amend Sec. 25.119 by revising paragraph (b) to read as follows:
Sec. 25.119 Landing climb: All-engines-operating.
* * * * *
(b) In icing conditions with the most critical of the landing ice
accretion(s) defined in Appendices C and O of this part, as applicable,
in accordance with Sec. 25.21(g), and with a climb speed of
VREF determined in accordance with Sec. 25.125(b)(2)(ii).
0
6. Amend Sec. 25.121 by revising paragraphs (b)(2)(ii) introductory
text, (c)(2)(ii) introductory text, and (d)(2)(ii) to read as follows:
Sec. 25.121 Climb: One-engine-inoperative.
* * * * *
(b) * * *
(2) * * *
(ii) In icing conditions with the most critical of the takeoff ice
accretion(s) defined in Appendices C and O of this part, as applicable,
in accordance with Sec. 25.21(g), if in the configuration used to show
compliance with Sec. 25.121(b) with this takeoff ice accretion:
* * * * *
(c) * * *
(2) * * *
(ii) In icing conditions with the most critical of the final
takeoff ice accretion(s) defined in Appendices C and O of this part, as
applicable, in accordance with Sec. 25.21(g), if in the configuration
used to show compliance with Sec. 25.121(b) with the takeoff ice
accretion used to show compliance with Sec. 25.111(c)(5)(i):
* * * * *
(d) * * *
(2) * * *
(ii) In icing conditions with the most critical of the approach ice
accretion(s) defined in Appendices C and O of this part, as applicable,
in accordance with Sec. 25.21(g). The climb speed selected for non-
icing conditions may be used if the climb speed for icing conditions,
computed in accordance with paragraph (d)(1)(iii) of this section, does
not exceed that for non-icing conditions by more than the greater of 3
knots CAS or 3 percent.
0
7. Amend Sec. 25.123 by revising paragraph (b)(2) introductory text to
read as follows:
Sec. 25.123 En route flight paths.
* * * * *
(b) * * *
(2) In icing conditions with the most critical of the en route ice
accretion(s) defined in Appendices C and O of this part, as applicable,
in accordance with Sec. 25.21(g), if:
* * * * *
0
8. Amend Sec. 25.125 by revising paragraphs (a)(2), (b)(2)(ii)(B), and
(b)(2)(ii)(C) to read as follows:
Sec. 25.125 Landing.
(a) * * *
(2) In icing conditions with the most critical of the landing ice
accretion(s) defined in Appendices C and O of this part, as applicable,
in accordance with Sec. 25.21(g), if VREF for icing
conditions exceeds VREF for non-icing conditions by more
than 5 knots CAS at the maximum landing weight.
(b) * * *
(2) * * *
(ii) * * *
(B) 1.23 VSR0 with the most critical of the landing ice
accretion(s) defined in Appendices C and O of this part, as applicable,
in accordance with Sec. 25.21(g), if that speed exceeds
VREF selected for non-icing conditions by more than 5 knots
CAS; and
(C) A speed that provides the maneuvering capability specified in
Sec. 25.143(h) with the most critical of the landing ice accretion(s)
defined in Appendices C and O of this part, as applicable, in
accordance with Sec. 25.21(g).
* * * * *
0
9. Amend Sec. 25.143 by revising paragraphs (c) introductory text,
(i)(1), and (j) introductory text to read as follows:
Sec. 25.143 General.
* * * * *
(c) The airplane must be shown to be safely controllable and
maneuverable with the most critical of the ice accretion(s) appropriate
to the phase of flight as defined in Appendices C and O of this part,
as applicable, in accordance with Sec. 25.21(g), and with the critical
engine inoperative and its propeller (if applicable) in the minimum
drag position:
* * * * *
(i) * * *
(1) Controllability must be demonstrated with the most critical of
the ice accretion(s) for the particular flight phase as defined in
Appendices C and O of this part, as applicable, in accordance with
Sec. 25.21(g);
* * * * *
(j) For flight in icing conditions before the ice protection system
has been activated and is performing its intended function, it must be
demonstrated in flight with the most critical of the ice accretion(s)
defined in Appendix C, part
[[Page 65526]]
II, paragraph (e) of this part and Appendix O, part II, paragraph (d)
of this part, as applicable, in accordance with Sec. 25.21(g), that:
* * * * *
0
10. Amend Sec. 25.207 by revising paragraphs (b), (e)(1), (e)(2),
(e)(3), (e)(4), (e)(5), and (h) introductory text as follows:
Sec. 25.207 Stall warning.
* * * * *
(b) The warning must be furnished either through the inherent
aerodynamic qualities of the airplane or by a device that will give
clearly distinguishable indications under expected conditions of
flight. However, a visual stall warning device that requires the
attention of the crew within the cockpit is not acceptable by itself.
If a warning device is used, it must provide a warning in each of the
airplane configurations prescribed in paragraph (a) of this section at
the speed prescribed in paragraphs (c) and (d) of this section. Except
for the stall warning prescribed in paragraph (h)(3)(ii) of this
section, the stall warning for flight in icing conditions must be
provided by the same means as the stall warning for flight in non-icing
conditions.
* * * * *
(e) * * *
(1) The most critical of the takeoff ice and final takeoff ice
accretions defined in Appendices C and O of this part, as applicable,
in accordance with Sec. 25.21(g), for each configuration used in the
takeoff phase of flight;
(2) The most critical of the en route ice accretion(s) defined in
Appendices C and O of this part, as applicable, in accordance with
Sec. 25.21(g), for the en route configuration;
(3) The most critical of the holding ice accretion(s) defined in
Appendices C and O of this part, as applicable, in accordance with
Sec. 25.21(g), for the holding configuration(s);
(4) The most critical of the approach ice accretion(s) defined in
Appendices C and O of this part, as applicable, in accordance with
Sec. 25.21(g), for the approach configuration(s); and
(5) The most critical of the landing ice accretion(s) defined in
Appendices C and O of this part, as applicable, in accordance with
Sec. 25.21(g), for the landing and go-around configuration(s).
* * * * *
(h) The following stall warning margin is required for flight in
icing conditions before the ice protection system has been activated
and is performing its intended function. Compliance must be shown using
the most critical of the ice accretion(s) defined in Appendix C, part
II, paragraph (e) of this part and Appendix O, part II, paragraph (d)
of this part, as applicable, in accordance with Sec. 25.21(g). The
stall warning margin in straight and turning flight must be sufficient
to allow the pilot to prevent stalling without encountering any adverse
flight characteristics when:
* * * * *
0
11. Amend Sec. 25.237 by revising paragraph (a)(3)(ii) to read as
follows:
Sec. 25.237 Wind velocities.
(a) * * *
(3) * * *
(ii) Icing conditions with the most critical of the landing ice
accretion(s) defined in Appendices C and O of this part, as applicable,
in accordance with Sec. 25.21(g).
* * * * *
0
12. Amend Sec. 25.253 by revising paragraph (c) introductory text to
read as follows:
Sec. 25.253 High-speed characteristics.
* * * * *
(c) Maximum speed for stability characteristics in icing
conditions. The maximum speed for stability characteristics with the
most critical of the ice accretions defined in Appendices C and O of
this part, as applicable, in accordance with Sec. 25.21(g), at which
the requirements of Sec. Sec. 25.143(g), 25.147(f), 25.175(b)(1),
25.177(a) through (c), and 25.181 must be met, is the lower of:
* * * * *
0
13. Amend Sec. 25.773 by revising paragraph (b)(1)(ii) to read as
follows:
Sec. 25.773 Pilot compartment view.
* * * * *
(b) * * *
(1) * * *
(ii) The icing conditions specified in Appendix C of this part and
the following icing conditions specified in Appendix O of this part, if
certification for flight in icing conditions is sought:
(A) For airplanes certificated in accordance with Sec.
25.1420(a)(1), the icing conditions that the airplane is certified to
safely exit following detection.
(B) For airplanes certificated in accordance with Sec.
25.1420(a)(2), the icing conditions that the airplane is certified to
safely operate in and the icing conditions that the airplane is
certified to safely exit following detection.
(C) For airplanes certificated in accordance with Sec.
25.1420(a)(3) and for airplanes not subject to Sec. 25.1420, all icing
conditions.
* * * * *
0
14. Amend Sec. 25.903 by adding a new paragraph (a)(3) to read as
follows:
Sec. 25.903 Engines.
(a) * * *
(3) Each turbine engine must comply with one of the following
paragraphs:
(i) Section 33.68 of this chapter in effect on January 5, 2015, or
as subsequently amended; or
(ii) Section 33.68 of this chapter in effect on February 23, 1984,
or as subsequently amended before January 5, 2015, unless that engine's
ice accumulation service history has resulted in an unsafe condition;
or
(iii) Section 33.68 of this chapter in effect on October 1, 1974,
or as subsequently amended prior to February 23, 1984, unless that
engine's ice accumulation service history has resulted in an unsafe
condition; or
(iv) Be shown to have an ice accumulation service history in
similar installation locations which has not resulted in any unsafe
conditions.
* * * * *
0
15. Amend Sec. 25.929 by revising paragraph (a) to read as follows:
Sec. 25.929 Propeller deicing.
(a) If certification for flight in icing is sought there must be a
means to prevent or remove hazardous ice accumulations that could form
in the icing conditions defined in Appendix C of this part and in the
portions of Appendix O of this part for which the airplane is approved
for flight on propellers or on accessories where ice accumulation would
jeopardize engine performance.
* * * * *
0
16. Amend Sec. 25.1093 by revising paragraph (b) to read as follows:
Sec. 25.1093 Induction system icing protection.
* * * * *
(b) Turbine engines. Except as provided in paragraph (b)(3) of this
section, each engine, with all icing protection systems operating,
must:
(1) Operate throughout its flight power range, including the
minimum descent idling speeds, in the icing conditions defined in
Appendices C and O of this part, and Appendix D of part 33 of this
chapter, and in falling and blowing snow within the limitations
established for the airplane for such operation, without the
accumulation of ice on the engine, inlet system components, or airframe
components that would do any of the following:
(i) Adversely affect installed engine operation or cause a
sustained loss of power or thrust; or an unacceptable increase in gas
path operating
[[Page 65527]]
temperature; or an airframe/engine incompatibility; or
(ii) Result in unacceptable temporary power loss or engine damage;
or
(iii) Cause a stall, surge, or flameout or loss of engine
controllability (for example, rollback).
(2) Operate at ground idle speed for a minimum of 30 minutes on the
ground in the following icing conditions shown in Table 1 of this
section, unless replaced by similar test conditions that are more
critical. These conditions must be demonstrated with the available air
bleed for icing protection at its critical condition, without adverse
effect, followed by an acceleration to takeoff power or thrust in
accordance with the procedures defined in the airplane flight manual.
During the idle operation, the engine may be run up periodically to a
moderate power or thrust setting in a manner acceptable to the
Administrator. Analysis may be used to show ambient temperatures below
the tested temperature are less critical. The applicant must document
the engine run-up procedure (including the maximum time interval
between run-ups from idle, run-up power setting, and duration at
power), the associated minimum ambient temperature, and the maximum
time interval. These conditions must be used in the analysis that
establishes the airplane operating limitations in accordance with Sec.
25.1521.
(3) For the purposes of this section, the icing conditions defined
in appendix O of this part, including the conditions specified in
Condition 3 of Table 1 of this section, are not applicable to airplanes
with a maximum takeoff weight equal to or greater than 60,000 pounds.
Table 1--Icing Conditions for Ground Tests
--------------------------------------------------------------------------------------------------------------------------------------------------------
Water concentration Mean effective
Condition Total air temperature (minimum) particle diameter Demonstration
--------------------------------------------------------------------------------------------------------------------------------------------------------
1. Rime ice condition............. 0 to 15 [deg]F (18 to Liquid--0.3 g/m\3\... 15-25 microns....... By test, analysis or combination of the two.
-9 [deg]C).
2. Glaze ice condition............ 20 to 30 [deg]F (-7 Liquid--0.3 g/m\3\... 15-25 microns....... By test, analysis or combination of the two.
to -1 [deg]C).
3. Large drop condition........... 15 to 30 [deg]F (-9 Liquid--0.3 g/m\3\... 100 microns By test, analysis or combination of the two.
to -1 [deg]C). (minimum).
--------------------------------------------------------------------------------------------------------------------------------------------------------
* * * * *
0
17. Amend Sec. 25.1323 by revising paragraph (i) to read as follows:
Sec. 25.1323 Airspeed indicating system.
* * * * *
(i) Each system must have a heated pitot tube or an equivalent
means of preventing malfunction in the heavy rain conditions defined in
Table 1 of this section; mixed phase and ice crystal conditions as
defined in part 33, Appendix D, of this chapter; the icing conditions
defined in Appendix C of this part; and the following icing conditions
specified in Appendix O of this part:
(1) For airplanes certificated in accordance with Sec.
25.1420(a)(1), the icing conditions that the airplane is certified to
safely exit following detection.
(2) For airplanes certificated in accordance with Sec.
25.1420(a)(2), the icing conditions that the airplane is certified to
safely operate in and the icing conditions that the airplane is
certified to safely exit following detection.
(3) For airplanes certificated in accordance with Sec.
25.1420(a)(3) and for airplanes not subject to Sec. 25.1420, all icing
conditions.
Table 1--Heavy Rain Conditions for Airspeed Indicating System Tests
----------------------------------------------------------------------------------------------------------------
Altitude range Liquid water Horizontal extent Droplet MVD
------------------------------------------------ content ------------------------------------------------
----------------
(ft) (m) (g/m3) (km) (nmiles) ([micro]m)
----------------------------------------------------------------------------------------------------------------
0 to 10 000.................. 0 to 3000....... 1 100 50 1000
6 5 3 2000
15 1 0.5 2000
----------------------------------------------------------------------------------------------------------------
* * * * *
0
18. Amend part 25 by adding a new section Sec. 25.1324 to read as
follows:
Sec. 25.1324 Angle of attack system.
Each angle of attack system sensor must be heated or have an
equivalent means of preventing malfunction in the heavy rain conditions
defined in Table 1 of Sec. 25.1323, the mixed phase and ice crystal
conditions as defined in part 33, Appendix D, of this chapter, the
icing conditions defined in Appendix C of this part, and the following
icing conditions specified in Appendix O of this part:
(a) For airplanes certificated in accordance with Sec.
25.1420(a)(1), the icing conditions that the airplane is certified to
safely exit following detection.
(b) For airplanes certificated in accordance with Sec.
25.1420(a)(2), the icing conditions that the airplane is certified to
safely operate in and the icing conditions that the airplane is
certified to safely exit following detection.
(c) For airplanes certificated in accordance with Sec.
25.1420(a)(3) and for airplanes not subject to Sec. 25.1420, all icing
conditions.
0
19. Amend Sec. 25.1325 by revising paragraph (b) to read as follows:
Sec. 25.1325 Static pressure systems.
* * * * *
(b) Each static port must be designed and located so that:
(1) The static pressure system performance is least affected by
airflow variation, or by moisture or other foreign matter; and
(2) The correlation between air pressure in the static pressure
system and true ambient atmospheric static pressure is not changed when
the airplane is exposed to the icing conditions defined in Appendix C
of
[[Page 65528]]
this part, and the following icing conditions specified in Appendix O
of this part:
(i) For airplanes certificated in accordance with Sec.
25.1420(a)(1), the icing conditions that the airplane is certified to
safely exit following detection.
(ii) For airplanes certificated in accordance with Sec.
25.1420(a)(2), the icing conditions that the airplane is certified to
safely operate in and the icing conditions that the airplane is
certified to safely exit following detection.
(iii) For airplanes certificated in accordance with Sec.
25.1420(a)(3) and for airplanes not subject to Sec. 25.1420, all icing
conditions.
* * * * *
0
20. Amend part 25 by adding a new Sec. 25.1420 to read as follows:
Sec. 25.1420 Supercooled large drop icing conditions.
(a) If certification for flight in icing conditions is sought, in
addition to the requirements of Sec. 25.1419, an airplane with a
maximum takeoff weight less than 60,000 pounds or with reversible
flight controls must be capable of operating in accordance with
paragraphs (a)(1), (2), or (3), of this section.
(1) Operating safely after encountering the icing conditions
defined in Appendix O of this part:
(i) The airplane must have a means to detect that it is operating
in Appendix O icing conditions; and
(ii) Following detection of Appendix O icing conditions, the
airplane must be capable of operating safely while exiting all icing
conditions.
(2) Operating safely in a portion of the icing conditions defined
in Appendix O of this part as selected by the applicant:
(i) The airplane must have a means to detect that it is operating
in conditions that exceed the selected portion of Appendix O icing
conditions; and
(ii) Following detection, the airplane must be capable of operating
safely while exiting all icing conditions.
(3) Operating safely in the icing conditions defined in Appendix O
of this part.
(b) To establish that the airplane can operate safely as required
in paragraph (a) of this section, an applicant must show through
analysis that the ice protection for the various components of the
airplane is adequate, taking into account the various airplane
operational configurations. To verify the analysis, one, or more as
found necessary, of the following methods must be used:
(1) Laboratory dry air or simulated icing tests, or a combination
of both, of the components or models of the components.
(2) Laboratory dry air or simulated icing tests, or a combination
of both, of models of the airplane.
(3) Flight tests of the airplane or its components in simulated
icing conditions, measured as necessary to support the analysis.
(4) Flight tests of the airplane with simulated ice shapes.
(5) Flight tests of the airplane in natural icing conditions,
measured as necessary to support the analysis.
(c) For an airplane certified in accordance with paragraph (a)(2)
or (3) of this section, the requirements of Sec. 25.1419(e), (f), (g),
and (h) must be met for the icing conditions defined in Appendix O of
this part in which the airplane is certified to operate.
(d) For the purposes of this section, the following definitions
apply:
(1) Reversible Flight Controls. Flight controls in the normal
operating configuration that have force or motion originating at the
airplane's control surface (for example, through aerodynamic loads,
static imbalance, or trim or servo tab inputs) that is transmitted back
to flight deck controls. This term refers to flight deck controls
connected to the pitch, roll, or yaw control surfaces by direct
mechanical linkages, cables, or push-pull rods in such a way that pilot
effort produces motion or force about the hinge line.
(2) Simulated Icing Test. Testing conducted in simulated icing
conditions, such as in an icing tunnel or behind an icing tanker.
(3) Simulated Ice Shape. Ice shape fabricated from wood, epoxy, or
other materials by any construction technique.
0
21. Amend Sec. 25.1521 by redesignating paragraph (c)(3) as paragraph
(c)(4), revising newly redesignated paragraph (c)(4), and adding new
paragraph (c)(3) to read as follows:
Sec. 25.1521 Powerplant limitations.
* * * * *
(c) * * *
(3) Maximum time interval between engine run-ups from idle, run-up
power setting and duration at power for ground operation in icing
conditions, as defined in Sec. 25.1093(b)(2).
(4) Any other parameter for which a limitation has been established
as part of the engine type certificate except that a limitation need
not be established for a parameter that cannot be exceeded during
normal operation due to the design of the installation or to another
established limitation.
* * * * *
0
22. Amend Sec. 25.1533 by adding a new paragraph (c) to read as
follows:
Sec. 25.1533 Additional operating limitations.
* * * * *
(c) For airplanes certified in accordance with Sec. 25.1420(a)(1)
or (2), an operating limitation must be established to:
(1) Prohibit intentional flight, including takeoff and landing,
into icing conditions defined in Appendix O of this part for which the
airplane has not been certified to safely operate; and
(2) Require exiting all icing conditions if icing conditions
defined in Appendix O of this part are encountered for which the
airplane has not been certified to safely operate.
0
23. Amend Appendix C to part 25, in part II, by revising paragraph
(a)(1), the second sentence of paragraph (a)(2), and paragraph (d)(2)
to read as follows:
Appendix C to Part 25
* * * * *
PART II--AIRFRAME ICE ACCRETIONS FOR SHOWING COMPLIANCE WITH SUBPART B
(a) * * *
(1) Takeoff ice is the most critical ice accretion on
unprotected surfaces and any ice accretion on the protected surfaces
appropriate to normal ice protection system operation, occurring
between the end of the takeoff distance and 400 feet above the
takeoff surface, assuming accretion starts at the end of the takeoff
distance in the takeoff maximum icing conditions defined in part I
of this Appendix.
(2) * * * Ice accretion is assumed to start at the end of the
takeoff distance in the takeoff maximum icing conditions of part I,
paragraph (c) of this Appendix.
* * * * *
(d) * * *
(2) The ice accretion starts at the end of the takeoff distance.
* * * * *
0
24. Amend part 25 by adding new Appendix O to read as follows:
Appendix O to Part 25--Supercooled Large Drop Icing Conditions
This Appendix consists of two parts. Part I defines this
Appendix as a description of supercooled large drop icing conditions
in which the drop median volume diameter (MVD) is less than or
greater than 40 [micro]m, the maximum mean effective drop diameter
(MED) of Appendix C of this part continuous maximum (stratiform
clouds) icing conditions. For this Appendix, supercooled large drop
icing conditions consist of freezing drizzle and freezing rain
occurring in and/or below stratiform clouds. Part II defines ice
accretions used to show compliance with the airplane performance and
handling qualities requirements of subpart B of this part.
[[Page 65529]]
PART I--METEOROLOGY
In this Appendix icing conditions are defined by the parameters
of altitude, vertical and horizontal extent, temperature, liquid
water content, and water mass distribution as a function of drop
diameter distribution.
(a) Freezing Drizzle (Conditions with spectra maximum drop
diameters from 100[micro]m to 500 [micro]m):
(1) Pressure altitude range: 0 to 22,000 feet MSL.
(2) Maximum vertical extent: 12,000 feet.
(3) Horizontal extent: Standard distance of 17.4 nautical miles.
(4) Total liquid water content.
Note: Liquid water content (LWC) in grams per cubic meter (g/
m\3\) based on horizontal extent standard distance of 17.4 nautical
miles.
(5) Drop diameter distribution: Figure 2.
(6) Altitude and temperature envelope: Figure 3.
(b) Freezing Rain (Conditions with spectra maximum drop
diameters greater than 500 [micro]m):
(1) Pressure altitude range: 0 to 12,000 ft MSL.
(2) Maximum vertical extent: 7,000 ft.
(3) Horizontal extent: Standard distance of 17.4 nautical miles.
(4) Total liquid water content.
Note: LWC in grams per cubic meter (g/m\3\) based on horizontal
extent standard distance of 17.4 nautical miles.
(5) Drop Diameter Distribution: Figure 5.
(6) Altitude and temperature envelope: Figure 6.
(c) Horizontal extent.
The liquid water content for freezing drizzle and freezing rain
conditions for horizontal extents other than the standard 17.4
nautical miles can be determined by the value of the liquid water
content determined from Figure 1 or Figure 4, multiplied by the
factor provided in Figure 7, which is defined by the following
equation:
S = 1.266 - 0.213 log10(H)
Where:
S = Liquid Water Content Scale Factor (dimensionless) and
H = horizontal extent in nautical miles
BILLING CODE 4910-13-P
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BILLING CODE 4910-13-C
PART II--AIRFRAME ICE ACCRETIONS FOR SHOWING COMPLIANCE WITH SUBPART B
OF THIS PART
(a) General.
The most critical ice accretion in terms of airplane performance
and handling qualities for each flight phase must be used to show
compliance with the applicable airplane performance and handling
qualities requirements for icing conditions contained in subpart B
of this part. Applicants must demonstrate that the full range of
atmospheric icing conditions specified in part I of this Appendix
have been considered, including drop diameter distributions, liquid
water content, and temperature appropriate to the flight conditions
(for example, configuration, speed, angle of attack, and altitude).
(1) For an airplane certified in accordance with Sec.
25.1420(a)(1), the ice accretions for each flight phase are defined
in part II, paragraph (b) of this Appendix.
(2) For an airplane certified in accordance with Sec.
25.1420(a)(2), the most critical ice accretion for each flight phase
defined in part II, paragraphs (b) and (c) of this Appendix, must be
used. For the ice accretions defined in part II, paragraph (c) of
this Appendix, only the portion of part I of this Appendix in which
the airplane is capable of operating safely must be considered.
(3) For an airplane certified in accordance with Sec.
25.1420(a)(3), the ice accretions for each flight phase are defined
in part II, paragraph (c) of this Appendix.
(b) Ice accretions for airplanes certified in accordance with
Sec. 25.1420(a)(1) or (2).
(1) En route ice is the en route ice as defined by part II,
paragraph (c)(3), of this Appendix, for an airplane certified in
accordance with Sec. 25.1420(a)(2), or defined by part II,
paragraph (a)(3), of Appendix C of this part, for an airplane
certified in accordance with Sec. 25.1420(a)(1), plus:
(i) Pre-detection ice as defined by part II, paragraph (b)(5),
of this Appendix; and
(ii) The ice accumulated during the transit of one cloud with a
horizontal extent of 17.4 nautical miles in the most critical of the
icing conditions defined in part I of this Appendix and one cloud
with a horizontal extent of 17.4 nautical miles in the continuous
maximum icing conditions defined in Appendix C of this part.
(2) Holding ice is the holding ice defined by part II, paragraph
(c)(4), of this Appendix, for an airplane certified in accordance
with Sec. 25.1420(a)(2), or defined by part II, paragraph (a)(4),
of Appendix C of this part, for an airplane certified in accordance
with Sec. 25.1420(a)(1), plus:
(i) Pre-detection ice as defined by part II, paragraph (b)(5),
of this Appendix; and
(ii) The ice accumulated during the transit of one cloud with a
17.4 nautical miles horizontal extent in the most critical of the
icing conditions defined in part I of this Appendix and one cloud
with a horizontal extent of 17.4 nautical miles in the continuous
maximum icing conditions defined in Appendix C of this part.
(iii) Except the total exposure to holding ice conditions does
not need to exceed 45 minutes.
(3) Approach ice is the more critical of the holding ice defined
by part II, paragraph (b)(2), of this Appendix, or the ice
calculated in the applicable paragraphs (b)(3)(i) or (ii) of part
II, of this Appendix:
(i) For an airplane certified in accordance with Sec.
25.1420(a)(2), the ice accumulated during descent from the maximum
vertical extent of the icing conditions defined in part I of this
Appendix to 2,000 feet above the landing surface in the cruise
configuration, plus transition to the approach configuration, plus:
(A) Pre-detection ice, as defined by part II, paragraph (b)(5),
of this Appendix; and
(B) The ice accumulated during the transit at 2,000 feet above
the landing surface of one cloud with a horizontal extent of 17.4
nautical miles in the most critical of the icing conditions defined
in part I of this Appendix and one cloud with a horizontal extent of
17.4 nautical miles in the continuous maximum icing conditions
defined in Appendix C of this part.
[[Page 65535]]
(ii) For an airplane certified in accordance with Sec.
25.1420(a)(1), the ice accumulated during descent from the maximum
vertical extent of the maximum continuous icing conditions defined
in part I of Appendix C to 2,000 feet above the landing surface in
the cruise configuration, plus transition to the approach
configuration, plus:
(A) Pre-detection ice, as defined by part II, paragraph (b)(5),
of this Appendix; and
(B) The ice accumulated during the transit at 2,000 feet above
the landing surface of one cloud with a horizontal extent of 17.4
nautical miles in the most critical of the icing conditions defined
in part I of this Appendix and one cloud with a horizontal extent of
17.4 nautical miles in the continuous maximum icing conditions
defined in Appendix C of this part.
(4) Landing ice is the more critical of the holding ice as
defined by part II, paragraph (b)(2), of this Appendix, or the ice
calculated in the applicable paragraphs (b)(4)(i) or (ii) of part II
of this Appendix:
(i) For an airplane certified in accordance with Sec.
25.1420(a)(2), the ice accretion defined by part II, paragraph
(c)(5)(i), of this Appendix, plus a descent from 2,000 feet above
the landing surface to a height of 200 feet above the landing
surface with a transition to the landing configuration in the icing
conditions defined in part I of this Appendix, plus:
(A) Pre-detection ice, as defined in part II, paragraph (b)(5),
of this Appendix; and
(B) The ice accumulated during an exit maneuver, beginning with
the minimum climb gradient required by Sec. 25.119, from a height
of 200 feet above the landing surface through one cloud with a
horizontal extent of 17.4 nautical miles in the most critical of the
icing conditions defined in part I of this Appendix and one cloud
with a horizontal extent of 17.4 nautical miles in the continuous
maximum icing conditions defined in Appendix C of this part.
(ii) For an airplane certified in accordance with Sec.
25.1420(a)(1), the ice accumulated in the maximum continuous icing
conditions defined in Appendix C of this part, during a descent from
the maximum vertical extent of the icing conditions defined in
Appendix C of this part, to 2,000 feet above the landing surface in
the cruise configuration, plus transition to the approach
configuration and flying for 15 minutes at 2,000 feet above the
landing surface, plus a descent from 2,000 feet above the landing
surface to a height of 200 feet above the landing surface with a
transition to the landing configuration, plus:
(A) Pre-detection ice, as described by part II, paragraph
(b)(5), of this Appendix; and
(B) The ice accumulated during an exit maneuver, beginning with
the minimum climb gradient required by Sec. 25.119, from a height
of 200 feet above the landing surface through one cloud with a
horizontal extent of 17.4 nautical miles in the most critical of the
icing conditions defined in part I of this Appendix and one cloud
with a horizontal extent of 17.4 nautical miles in the continuous
maximum icing conditions defined in Appendix C of this part.
(5) Pre-detection ice is the ice accretion before detection of
flight conditions in this Appendix that require exiting per Sec.
25.1420(a)(1) and (2). It is the pre-existing ice accretion that may
exist from operating in icing conditions in which the airplane is
approved to operate prior to encountering the icing conditions
requiring an exit, plus the ice accumulated during the time needed
to detect the icing conditions, followed by two minutes of further
ice accumulation to take into account the time for the flightcrew to
take action to exit the icing conditions, including coordination
with air traffic control.
(i) For an airplane certified in accordance with Sec.
25.1420(a)(1), the pre-existing ice accretion must be based on the
icing conditions defined in Appendix C of this part.
(ii) For an airplane certified in accordance with Sec.
25.1420(a)(2), the pre-existing ice accretion must be based on the
more critical of the icing conditions defined in Appendix C of this
part, or the icing conditions defined in part I of this Appendix in
which the airplane is capable of safely operating.
(c) Ice accretions for airplanes certified in accordance with
Sec. Sec. 25.1420(a)(2) or (3). For an airplane certified in
accordance with Sec. 25.1420(a)(2), only the portion of the icing
conditions of part I of this Appendix in which the airplane is
capable of operating safely must be considered.
(1) Takeoff ice is the most critical ice accretion on
unprotected surfaces, and any ice accretion on the protected
surfaces, occurring between the end of the takeoff distance and 400
feet above the takeoff surface, assuming accretion starts at the end
of the takeoff distance in the icing conditions defined in part I of
this Appendix.
(2) Final takeoff ice is the most critical ice accretion on
unprotected surfaces, and any ice accretion on the protected
surfaces appropriate to normal ice protection system operation,
between 400 feet and either 1,500 feet above the takeoff surface, or
the height at which the transition from the takeoff to the en route
configuration is completed and VFTO is reached, whichever
is higher. Ice accretion is assumed to start at the end of the
takeoff distance in the icing conditions defined in part I of this
Appendix.
(3) En route ice is the most critical ice accretion on the
unprotected surfaces, and any ice accretion on the protected
surfaces appropriate to normal ice protection system operation,
during the en route flight phase in the icing conditions defined in
part I of this Appendix.
(4) Holding ice is the most critical ice accretion on the
unprotected surfaces, and any ice accretion on the protected
surfaces appropriate to normal ice protection system operation,
resulting from 45 minutes of flight within a cloud with a 17.4
nautical miles horizontal extent in the icing conditions defined in
part I of this Appendix, during the holding phase of flight.
(5) Approach ice is the ice accretion on the unprotected
surfaces, and any ice accretion on the protected surfaces
appropriate to normal ice protection system operation, resulting
from the more critical of the:
(i) Ice accumulated in the icing conditions defined in part I of
this Appendix during a descent from the maximum vertical extent of
the icing conditions defined in part I of this Appendix, to 2,000
feet above the landing surface in the cruise configuration, plus
transition to the approach configuration and flying for 15 minutes
at 2,000 feet above the landing surface; or
(ii) Holding ice as defined by part II, paragraph (c)(4), of
this Appendix.
(6) Landing ice is the ice accretion on the unprotected
surfaces, and any ice accretion on the protected surfaces
appropriate to normal ice protection system operation, resulting
from the more critical of the:
(i) Ice accretion defined by part II, paragraph (c)(5)(i), of
this Appendix, plus ice accumulated in the icing conditions defined
in part I of this Appendix during a descent from 2,000 feet above
the landing surface to a height of 200 feet above the landing
surface with a transition to the landing configuration, followed by
a go-around at the minimum climb gradient required by Sec. 25.119,
from a height of 200 feet above the landing surface to 2,000 feet
above the landing surface, flying for 15 minutes at 2,000 feet above
the landing surface in the approach configuration, and a descent to
the landing surface (touchdown) in the landing configuration; or
(ii) Holding ice as defined by part II, paragraph (c)(4), of
this Appendix.
(7) For both unprotected and protected parts, the ice accretion
for the takeoff phase must be determined for the icing conditions
defined in part I of this Appendix, using the following assumptions:
(i) The airfoils, control surfaces, and, if applicable,
propellers are free from frost, snow, or ice at the start of
takeoff;
(ii) The ice accretion starts at the end of the takeoff
distance;
(iii) The critical ratio of thrust/power-to-weight;
(iv) Failure of the critical engine occurs at VEF;
and
(v) Crew activation of the ice protection system is in
accordance with a normal operating procedure provided in the
airplane flight manual, except that after beginning the takeoff
roll, it must be assumed that the crew takes no action to activate
the ice protection system until the airplane is at least 400 feet
above the takeoff surface.
(d) The ice accretion before the ice protection system has been
activated and is performing its intended function is the critical
ice accretion formed on the unprotected and normally protected
surfaces before activation and effective operation of the ice
protection system in the icing conditions defined in part I of this
Appendix. This ice accretion only applies in showing compliance to
Sec. Sec. 25.143(j) and 25.207(h).
(e) In order to reduce the number of ice accretions to be
considered when demonstrating compliance with the requirements of
Sec. 25.21(g), any of the ice accretions defined in this Appendix
may be used for any other flight phase if it is shown to be at least
as critical as the specific ice accretion defined for that flight
phase. Configuration differences and their effects on ice accretions
must be taken into account.
(f) The ice accretion that has the most adverse effect on
handling qualities may be used for airplane performance tests
provided any difference in performance is conservatively taken into
account.
[[Page 65536]]
PART 33--AIRWORTHINESS STANDARDS: AIRCRAFT ENGINES
0
25. The authority citation for part 33 is revised to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.
0
26. Revise Sec. 33.68 to read as follows:
Sec. 33.68 Induction system icing.
Each engine, with all icing protection systems operating, must:
(a) Operate throughout its flight power range, including the
minimum descent idle rotor speeds achievable in flight, in the icing
conditions defined for turbojet, turbofan, and turboprop engines in
Appendices C and O of part 25 of this chapter, and Appendix D of this
part, and for turboshaft engines in Appendix C of part 29 of this
chapter, without the accumulation of ice on the engine components that:
(1) Adversely affects engine operation or that causes an
unacceptable permanent loss of power or thrust or unacceptable increase
in engine operating temperature; or
(2) Results in unacceptable temporary power loss or engine damage;
or
(3) Causes a stall, surge, or flameout or loss of engine
controllability. The applicant must account for in-flight ram effects
in any critical point analysis or test demonstration of these flight
conditions.
(b) Operate throughout its flight power range, including minimum
descent idle rotor speeds achievable in flight, in the icing conditions
defined for turbojet, turbofan, and turboprop engines in Appendices C
and O of part 25 of this chapter, and for turboshaft engines in
Appendix C of part 29 of this chapter. In addition:
(1) It must be shown through Critical Point Analysis (CPA) that the
complete ice envelope has been analyzed, and that the most critical
points must be demonstrated by engine test, analysis, or a combination
of the two to operate acceptably. Extended flight in critical flight
conditions such as hold, descent, approach, climb, and cruise, must be
addressed, for the ice conditions defined in these appendices.
(2) It must be shown by engine test, analysis, or a combination of
the two that the engine can operate acceptably for the following
durations:
(i) At engine powers that can sustain level flight: A duration that
achieves repetitive, stabilized operation for turbojet, turbofan, and
turboprop engines in the icing conditions defined in Appendices C and O
of part 25 of this chapter, and for turboshaft engines in the icing
conditions defined in Appendix C of part 29 of this chapter.
(ii) At engine power below that which can sustain level flight:
(A) Demonstration in altitude flight simulation test facility: A
duration of 10 minutes consistent with a simulated flight descent of
10,000 ft (3 km) in altitude while operating in Continuous Maximum
icing conditions defined in Appendix C of part 25 of this chapter for
turbojet, turbofan, and turboprop engines, and for turboshaft engines
in the icing conditions defined in Appendix C of part 29 of this
chapter, plus 40 percent liquid water content margin, at the critical
level of airspeed and air temperature; or
(B) Demonstration in ground test facility: A duration of 3 cycles
of alternating icing exposure corresponding to the liquid water content
levels and standard cloud lengths starting in Intermittent Maximum and
then in Continuous Maximum icing conditions defined in Appendix C of
part 25 of this chapter for turbojet, turbofan, and turboprop engines,
and for turboshaft engines in the icing conditions defined in Appendix
C of part 29 of this chapter, at the critical level of air temperature.
(c) In addition to complying with paragraph (b) of this section,
the following conditions shown in Table 1 of this section unless
replaced by similar CPA test conditions that are more critical or
produce an equivalent level of severity, must be demonstrated by an
engine test:
Table 1--Conditions That Must Be Demonstrated by an Engine Test
----------------------------------------------------------------------------------------------------------------
Supercooled
Total air water
Condition temperature concentrations Median volume drop diameter Duration
(minimum)
----------------------------------------------------------------------------------------------------------------
1. Glaze ice conditions...... 21 to 25 [deg]F 2 g/m\3\........ 25 to 35 microns........... (a) 10-minutes
(-6 to -4 for power below
[deg]C). sustainable
level flight
(idle descent).
(b) Must show
repetitive,
stabilized
operation for
higher powers
(50%, 75%,
100%MC).
2. Rime ice conditions....... -10 to 0 [deg]F 1 g/m\3\........ 15 to 25 microns........... (a) 10-minutes
(-23 to -18 for power below
[deg]C). sustainable
level flight
(idle descent).
(b) Must show
repetitive,
stabilized
operation for
higher powers
(50%, 75%,
100%MC).
3. Glaze ice holding Turbojet and Alternating 20 to 30 microns........... Must show
conditions. Turbofan, only: cycle: First repetitive,
(Turbojet, turbofan, and 10 to 18 [deg]F 1.7 g/m\3\ (1 stabilized
turboprop only). (-12 to -8 minute), Then operation (or
[deg]C). 0.3 g/m\3\ (6 45 minutes
minute). max).
Turboprop, only: ................ ........................... ................
2 to 10 [deg]F
(-17 to -12
[deg]C).
4. Rime ice holding Turbojet and 0.25 g/m\3\..... 20 to 30 microns........... Must show
conditions. Turbofan, only: repetitive,
(Turbojet, turbofan, and -10 to 0 [deg]F stabilized
turboprop only). (-23 to -18 operation (or
[deg]C). 45 minutes
max).
Turboprop, only: ................ ........................... ................
2 to 10 [deg]F
(-17 to -12
[deg]C).
----------------------------------------------------------------------------------------------------------------
[[Page 65537]]
(d) Operate at ground idle speed for a minimum of 30 minutes at
each of the following icing conditions shown in Table 2 of this section
with the available air bleed for icing protection at its critical
condition, without adverse effect, followed by acceleration to takeoff
power or thrust. During the idle operation, the engine may be run up
periodically to a moderate power or thrust setting in a manner
acceptable to the Administrator. Analysis may be used to show ambient
temperatures below the tested temperature are less critical. The
applicant must document any demonstrated run ups and minimum ambient
temperature capability in the engine operating manual as mandatory in
icing conditions. The applicant must demonstrate, with consideration of
expected airport elevations, the following:
Table 2--Demonstration Methods for Specific Icing Conditions
----------------------------------------------------------------------------------------------------------------
Supercooled
Total air water Mean effective particle
Condition temperature concentrations diameter Demonstration
(minimum)
----------------------------------------------------------------------------------------------------------------
1. Rime ice condition........ 0 to 15 [deg]F (- Liquid--0.3 g/ 15-25 microns.............. By engine test.
18 to -9 m\3\.
[deg]C).
2. Glaze ice condition....... 20 to 30 [deg]F Liquid--0.3 g/ 15-25 microns.............. By engine test.
(-7 to -1 m\3\.
[deg]C).
3. Snow ice condition........ 26 to 32 [deg]F Ice--0.9 g/m\3\. 100 microns................ By test,
(-3 to 0 (minimum).................. analysis or
[deg]C). combination of
the two.
4. Large drop glaze ice 15 to 30 [deg]F Liquid--0.3 g/ 100 microns (minimum)...... By test,
condition (Turbojet, (-9 to -1 m\3\. analysis or
turbofan, and turboprop [deg]C). combination of
only). the two.
----------------------------------------------------------------------------------------------------------------
(e) Demonstrate by test, analysis, or combination of the two,
acceptable operation for turbojet, turbofan, and turboprop engines in
mixed phase and ice crystal icing conditions throughout Appendix D of
this part, icing envelope throughout its flight power range, including
minimum descent idling speeds.
0
27. Amend Sec. 33.77 by adding paragraph (a) and revising paragraphs
(c) introductory text, (c)(1), (d), and (e) to read as follows:
Sec. 33.77 Foreign object ingestion ice.
(a) Compliance with the requirements of this section must be
demonstrated by engine ice ingestion test or by validated analysis
showing equivalence of other means for demonstrating soft body damage
tolerance.
* * * * *
(c) Ingestion of ice under the conditions of this section may not--
(1) Cause an immediate or ultimate unacceptable sustained power or
thrust loss; or
* * * * *
(d) For an engine that incorporates a protection device, compliance
with this section need not be demonstrated with respect to ice formed
forward of the protection device if it is shown that--
(1) Such ice is of a size that will not pass through the protective
device;
(2) The protective device will withstand the impact of the ice; and
(3) The ice stopped by the protective device will not obstruct the
flow of induction air into the engine with a resultant sustained
reduction in power or thrust greater than those values defined by
paragraph (c) of this section.
(e) Compliance with the requirements of this section must be
demonstrated by engine ice ingestion test under the following ingestion
conditions or by validated analysis showing equivalence of other means
for demonstrating soft body damage tolerance.
(1) The minimum ice quantity and dimensions will be established by
the engine size as defined in Table 1 of this section.
(2) The ingested ice dimensions are determined by linear
interpolation between table values, and are based on the actual
engine's inlet hilite area.
(3) The ingestion velocity will simulate ice from the inlet being
sucked into the engine.
(4) Engine operation will be at the maximum cruise power or thrust
unless lower power is more critical.
Table 1--Minimum Ice Slab Dimensions Based on Engine Inlet Size
----------------------------------------------------------------------------------------------------------------
Thickness
Engine Inlet Hilite area (sq. inch) (inch) Width (inch) Length (inch)
----------------------------------------------------------------------------------------------------------------
0............................................................... 0.25 0 3.6
80.............................................................. 0.25 6 3.6
300............................................................. 0.25 12 3.6
700............................................................. 0.25 12 4.8
2800............................................................ 0.35 12 8.5
5000............................................................ 0.43 12 11.0
7000............................................................ 0.50 12 12.7
7900............................................................ 0.50 12 13.4
9500............................................................ 0.50 12 14.6
11300........................................................... 0.50 12 15.9
13300........................................................... 0.50 12 17.1
16500........................................................... 0.5 12 18.9
20000........................................................... 0.5 12 20.0
----------------------------------------------------------------------------------------------------------------
[[Page 65538]]
Appendix C [Added and Reserved]
0
28. Amend part 33 by adding and reserving a new Appendix C.
0
29. Amend part 33 by adding a new Appendix D to read as follows:
Appendix D to Part 33--Mixed Phase and Ice Crystal Icing Envelope (Deep
Convective Clouds)
The ice crystal icing envelope is depicted in Figure D1 of this
Appendix.
BILLING CODE 4910-13-P
[GRAPHIC] [TIFF OMITTED] TR04NO14.008
Within the envelope, total water content (TWC) in g/m\3\ has
been determined based upon the adiabatic lapse defined by the
convective rise of 90% relative humidity air from sea level to
higher altitudes and scaled by a factor of 0.65 to a standard cloud
length of 17.4 nautical miles. Figure D2 of this Appendix displays
TWC for this distance over a range of ambient temperature within the
boundaries of the ice crystal envelope specified in Figure D1 of
this Appendix.
[[Page 65539]]
[GRAPHIC] [TIFF OMITTED] TR04NO14.009
Ice crystal size median mass dimension (MMD) range is 50-200
microns (equivalent spherical size) based upon measurements near
convective storm cores.
The TWC can be treated as completely glaciated (ice crystal)
except as noted in the Table 1 of this Appendix.
Table 1--Supercooled Liquid Portion of TWC
------------------------------------------------------------------------
Horizontal cloud LWC-- g/
Temperature range--deg C length--nautical miles m\3\
------------------------------------------------------------------------
0 to -20............................ <=50................... <=1.0
0 to -20............................ Indefinite............. <=0.5
< -20............................... ....................... 0
------------------------------------------------------------------------
The TWC levels displayed in Figure D2 of this Appendix represent
TWC values for a standard exposure distance (horizontal cloud
length) of 17.4 nautical miles that must be adjusted with length of
icing exposure.
[[Page 65540]]
[GRAPHIC] [TIFF OMITTED] TR04NO14.010
Issued under authority provided by 49 U.S.C. 106(f) and 44701(a)
in Washington, DC, on October 22, 2014.
Michael P. Huerta,
Administrator.
[FR Doc. 2014-25789 Filed 11-3-14; 8:45 am]
BILLING CODE 4910-13-C