[Federal Register Volume 65, Number 54 (Monday, March 20, 2000)]
[Rules and Regulations]
[Pages 14822-14825]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 00-6616]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 39
[Docket No. 99-CE-44-AD; Amendment 39-11643; AD 2000-06-03]
RIN 2120-AA64
Airworthiness Directives; Bombardier Inc. Models DHC-6-1, DHC-6-
100, DHC-6-200, and DHC-6-300 Airplanes
AGENCY: Federal Aviation Administration, DOT.
ACTION: Final rule.
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SUMMARY: This document adopts a new airworthiness directive (AD) that
applies to all Bombardier Inc. (Bombardier) Models DHC-6-1, DHC-6-100,
DHC-6-200, and DHC-6-300 airplanes that are equipped with pneumatic
deicing boots. This AD requires revising the Airplane Flight Manual
(AFM) to include requirements for activation of the airframe pneumatic
deicing boots. This AD is the result of reports of in-flight incidents
and an accident that occurred in icing conditions where the airframe
pneumatic deicing boots were not activated. The actions specified by
this AD are intended to assure that flightcrews activate the pneumatic
wing and tail deicing boots at the first signs of ice accumulation.
This action will prevent reduced controllability of the aircraft due to
adverse aerodynamic effects of ice adhering to the airplane prior to
the first deicing cycle.
EFFECTIVE DATE: May 5, 2000.
ADDRESSES: You may examine information related to this AD at the
Federal Aviation Administration (FAA), Central Region, Office of the
Regional Counsel, Attention: Rules Docket No. 99-CE-44-AD, 901 Locust,
Room 506, Kansas City, Missouri 64106.
FOR FURTHER INFORMATION CONTACT: Mr. John P. Dow, Sr., Aerospace
Engineer, FAA, Small Airplane Directorate, 901 Locust, Room 506, Kansas
City, Missouri 64106; telephone: (816) 329-4121; facsimile: (816) 329-
4090.
SUPPLEMENTARY INFORMATION:
Events Leading to the Issuance of This AD
What caused this AD?: This AD is the result of reports of in-flight
incidents and an accident that occurred in icing conditions where the
airframe pneumatic deicing boots were not activated.
What is the potential impact if the FAA took no action?: The
information necessary to activate the pneumatic wing and tail deicing
boots at the first signs of ice accumulation is critical for flight in
icing conditions. If we did not take action to include this
information, flight crews could experience reduced controllability of
the aircraft due to adverse aerodynamic effects of ice adhering to the
airplane prior to the first deicing cycle.
Has the FAA taken any action to this point?: Yes. We issued a
proposal to amend part 39 of the Federal Aviation Regulations (14 CFR
part 39) to include an AD that would apply to all Bombardier Models
DHC-6-1, DHC-6-100, DHC-6-200, and DHC-6-300 airplanes that are
equipped with pneumatic deicing boots. This proposal was published in
the Federal Register as a notice of proposed rulemaking (NPRM) on
October 12, 1999 (64 FR 55201). The NPRM proposed to require revising
the Limitations Section of the AFM to include requirements for
activating the pneumatic deicing boots at the first indication of ice
accumulation on the airplane.
Was the public invited to comment?: Yes. Interested persons were
afforded an opportunity to participate in the making of this amendment.
The following paragraphs present the comments received on the NPRM.
Also included is the FAA's response to each comment, including any
changes incorporated into the final rule based on the comments.
Comment Issue No. 1: Coordinate With Original Equipment
Manufacturer
What is the Commenter's Concern?: One commenter states that the FAA
should coordinate with the original equipment manufacturer before
issuing the AD.
What is the FAA's Response to the Concern?: We concur.
The FAA coordinates and will continue to coordinate with the
manufacturer of any affected airplanes before issuing an AD.
Is it Necessary to Change the AD?: No.
Comment Issue No. 2: Provide the Criteria for Determining
Acceptable Stall Warning Margins
What is the Commenter's Concern?: One commenter requests that the
FAA provide the criteria for determining whether an airplane has an
acceptable stall warning margin. The commenter references recent NPRM
AD withdrawals in the FAA's Transport Airplane Directorate.
What is the FAA's Response to the Concern?: We cannot provide such
information because no regulatory basis exists for determining or
applying a mandatory stall margin with contamination. We can review
manufacturer-provided data to determine what testing was conducted, and
then determine the effects of ice accretion on the stall angle and the
handling characteristics in the roll axis. This would include reviewing
the service history of each airplane. With all of this information, we
could determine whether the stall warning margin was acceptable and if
the AD action could be withdrawn.
Such was the case with the NPRM withdrawals in the FAA's Transport
Airplane Directorate. The airplanes affected were Cessna Models 500,
501, 550, 551, and 560 series airplanes, and British Aerospace
Jetstream Model 4101 airplanes. You may find the specific justification
for each of these withdrawals in the Federal Register through the
following citations:
--For the Cessna airplanes: 64 FR 62995, November 18, 1999; and -For
the Jetstream airplanes: 64 FR 62990, November 18, 1999.
No specific information was submitted for the Bombardier DHC-6
series airplanes.
Is it Necessary to Change the AD?: No.
Comment Issue No. 3: Review the Effects of Ice Bridging
What is the Commenter's Concerns?: A commenter states that the FAA
did not reference in the NPRM any testing to assure that ice bridging
does not exist on any of the affected airplanes. This commenter
requests that the FAA carefully review the effects of ice bridging. Ice
bridging, as referred to in the aviation community, occurs when the
mechanical deicing boots do not clear airframe icing from the wing
surface. This occurs because the ``ice bridge'' that forms over the
inflated boots increases in ice thickness while the deicing boots
ineffectively inflate and deflate under the ice bridge.
The commenter also requests explanation on the use of the term
``modern'' in a similar AD action that
[[Page 14823]]
the FAA's Transport Airplane Directorate initiated.
What is the FAA's Response to the Concerns?: The FAA considered the
effects of ice bridging while developing the AD. We consulted the
aviation community, including airframe manufacturers, air carriers,
airline pilot associations, airplane owner associations, deicing boot
manufacturers, and the National Aeronautics and Space Administration
(NASA). Based on information from the aviation community, we believe
that little evidence of ice bridging exists as it relates to current
deicing boot designs. Also, ice that is not shed after the initial boot
cycle continues to increase in thickness and sheds during subsequent
cycles.
The FAA's Transport Airplane Directorate addressed the issue of
``modern'' versus ``older'' pneumatic boot systems in a recent AD
action. That information, in its entirety, follows:
``Several commenters request that the difference between the
``older'' and ``modern'' boot systems be explained. These commenters
express concern that although both systems are addressed in the
proposal, there may not be a sound technical reason to apply the
requirements of the proposal to both types of boot systems.
The FAA acknowledges that definitions of ``older'' and
``modern'' pneumatic boot systems should be provided. Therefore, for
the purposes of this AD, ``modern'' pneumatic boot systems may be
characterized by short segmented, small diameter tubes, which are
operated at relatively high pressures [18-23 pounds per square inch
(psi)] by excess bleed air that is provided by turbine engines.
``Older'' pneumatic boot systems may be characterized by long,
uninterrupted, large diameter tubes, which were operated at low
pressures by engine driven pneumatic pumps whose pressure varied
with engine revolutions per minute (rpm). This low pressure coupled
with long and large diameter tubes caused early deice systems to
have very lengthy inflation and deflation cycles and dwell times.
(Dwell time is the period of time that the boot remains fully
expanded following the completion of the inflation cycle until the
beginning of the deflation cycle.)''
Is it Necessary to Change the AD?: No.
Comment Issue No. 4: Limit the AFM Change to Approach and Hold
Phases of Flight
What is the Commenter's Concern? One commenter requests that the
FAA limit the AFM change of operating the boots at the first sign of
ice accretion to the approach and hold phases of flight. This commenter
references the work that the Ice Protection Harmonization Working Group
(IPHWP) is currently doing. The commenter states that the IPHWP
believes that the only phases of flight that demonstrate a safety
concern are holding patterns and various approach segments. Since these
operations occur at lower speeds, ice accumulating on the wing and tail
surfaces could cause instability.
What is the FAA's Response to the Concern? We do not concur to
limiting the AFM change to the holding and approach phases of flight.
We acknowledge that the IPHWG is working on a proposed operations rule.
The IPHWG continues to work on this proposed rule and has not reached
technical agreement. We have records of in-flight roll upsets in icing
during the climb and cruise phases of flight on small airplanes that
are of a similar type design to the Bombardier DHC-6 series airplanes.
We concur that the ice protection system should not be operated at
times when no ice is accreting. We have changed the description of the
atmospheric conditions that the deicing boots must be operated from
``icing conditions'' to ``known or observed/detected icing that the
flight crew visually observed on the aircraft or was identified by the
on-board sensors.''
Is it Necessary to Change the AD?: Yes. We have made the change
described above in the final rule.
Comment Issue No. 5: Conduct Further Testing Before Issuing the AD
What is the Commenter's Concern? One commenter requests that the
FAA conduct more tests before proceeding with this AD action. The
commenter agrees that operating the pneumatic boots continuously is the
best way to identify ice accretion. However, the commenter states
concern over the residual ice that could accumulate in this mode. The
commenter recommends the following:
--The FAA research the possibility of mandating the installation of
a reliable ice detection system to alleviate the difficulties
associated with flightcrew recognition of airfoil ice accretions;
--The FAA work together with the manufacturers to determine how
efficient the pneumatic boots are in shedding significant thinner ice
accretions than encountered previously; and
--The FAA quantify the performance effects of prolonged operation
with residual ice on the airfoil prior to implementing any new boot
operation procedures.
What is the FAA's Response to the Concern? We do not concur with
the concerns over residual ice. Operation of the pneumatic deicing
boots typically results in persistent ice accretions on the boots
surfaces, even with 1/4-inch to 1/2-inch of ice accretion prior to
activation of the boots. The persistent residual and inter-cycle ice
accretions typically result in adverse aerodynamic effects and degraded
airplane flying qualities. Activating the wing and tail pneumatic
deicing boots at the first sign of ice accretion (or at the
annunciation of an ice detector system) and periodically operating the
deicing boots will result in persistent ice accretions.
However, the proposed actions will minimize the residual and
intercycle ice accretions because the ice will shed when the minimum
thickness or mass required for shedding is reached. The residual and
intercycle ice accretion thickness that results from this procedure is
less than the ice accretion thickness typically recommended prior to
operation of the pneumatic deicing boot. The thickness, shape, texture,
and location of the ice accretion affect the adverse airplane flying
qualities that result from ice accretions.
Certain airplane manufacturers have previously issued AFM
information that contains procedures to activate the deicing boots at
the first sign of ice accumulation. We have received no reports
indicating any adverse effects of residual ice because of early
activation of the deicing boots for these airplane designs.
Those airplane models that are equipped with deicing boot systems
with automatic operating modes result in operation of the boots with
less than the recommended thickness of accreted ice. We have received
no reports indicating any adverse effects resulting from the use of the
automatic mode.
We concur that the installation of a reliable ice detection system
would alleviate the difficulties associated with flightcrew recognition
of airfoil ice accretion. We are working with industry on the
possibility of developing such a system. If developed, tested, and
approved, the FAA may consider additional rulemaking. For the time
being, we are issuing this AD to impose a deicing boot operation change
to address the reduced handling qualities or controllability problems
associated with ice accretion on the protected surfaces.
Is it Necessary to Change the AD? No.
Comment Issue No. 6: Require Action to Reduce Adhesion
Characteristics
What is the Commenter's Concern? One commenter requests that the
FAA mandate actions to minimize or reduce the ice adhesion
characteristics of boot material. The commenter states that one reason
flightcrews see large amounts of residual ice is because residual ice
[[Page 14824]]
sticks to the boot surface as the boot ages. This may increase if the
adhesion qualities of the boot material are not maintained. The
commenter suggests the use of certain compounds, such as ICEX \TM\ (an
ice-phobic chemical spray), to reduce ice adhesion.
What is the FAA's Response to the Concern?: We concur that
materials such as ICEX \TM\ could reduce ice adhesion. However, factors
such as normal wear and tear, patching, and oxidation of boot material,
prevent us from establishing an effective level of application or
adequate intervals of application. We will include a NOTE in the AD to
recommend regular treatment of deicing boots with use of approved ice
release agents. This is in addition to the required actions.
Is it Necessary to Change the AD?: No. However, as discussed above,
the FAA is including a NOTE in the AD to recommend regular treatment of
deicing boots with use of approved ice release agents.
The FAA's Determination
What is the FAA's final determination on this issue? After careful
review of all available information related to the subject presented
above, we have determined that air safety and the public interest
require the adoption of the rule as proposed except for the following:
--The change in the description of the atmospheric conditions that the
deicing boots must be operated;
--The addition of the NOTE to recommend regular treatment of deicing
boots with use of approved ice release agents; and
--Minor editorial corrections.
How does the change, addition, and corrections affect the AD?: We
have determined that the change, addition, and minor corrections will
not change the meaning of the AD and will not add any additional burden
upon the public than was already proposed.
Cost Impact
How many airplanes does this AD impact?: We estimate that 162
airplanes in the U.S. registry will be affected.
What is the cost impact of the affected airplanes on the U.S.
Register?: There is no dollar cost impact. We estimate that to
accomplish the AFM revision it will take you less than 1 workhour. You
can accomplish this action if you hold at least a private pilot
certificate as authorized by section 43.7 of the Federal Aviation
Regulations (14 CFR 43.7). You must make an entry into the aircraft
records that shows compliance with this AD, in accordance with section
43.9 of the Federal Aviation Regulations (14 CFR 43.9). The only cost
impact of this AD is the time it will take you to insert the
information into the AFM.
Regulatory Impact
The regulations adopted herein will not have a substantial direct
effect on the States, on the relationship between the national
government and the States, or on the distribution of power and
responsibilities among the various levels of government. Therefore, it
is determined that this final rule does not have federalism
implications under Executive Order 13132.
For the reasons discussed above, I certify that this action (1) is
not a ``significant regulatory action'' under Executive Order 12866;
(2) is not a ``significant rule'' under DOT Regulatory Policies and
Procedures (44 FR 11034, February 26, 1979); and (3) will not have a
significant economic impact, positive or negative, on a substantial
number of small entities under the criteria of the Regulatory
Flexibility Act. A copy of the final evaluation prepared for this
action is contained in the Rules Docket. A copy of it may be obtained
by contacting the Rules Docket at the location provided under the
caption ADDRESSES.
List of Subjects in 14 CFR Part 39
Air transportation, Aircraft, Aviation safety, Safety.
Adoption of the Amendment
Accordingly, pursuant to the authority delegated to me by the
Administrator, the Federal Aviation Administration amends part 39 of
the Federal Aviation Regulations (14 CFR part 39) as follows:
PART 39--AIRWORTHINESS DIRECTIVES
1. The authority citation for part 39 continues to read as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701.
Sec. 39.13 [Amended]
2. Section 39.13 is amended by adding a new airworthiness directive
(AD) to read as follows:
2000-06-03 Bombardier Inc.: Amendment 39-11643; Docket No. 99-CE-44-
AD.
(a) What airplanes are affected by this AD?
Models DHC-6-1, DHC-6-100, DHC-6-200, DHC-6-300 airplanes, all
serial numbers, that are:
(1) Equipped with pneumatic deicing boots; and
(2) Certificated in any category.
(b) Who must comply with this AD? Anyone who wishes to operate
any of the above airplanes on the U.S. Register. The AD does not
apply to your airplane if it is not equipped with pneumatic de-icing
boots.
(c) What problem does this AD address? The information necessary
to activate the pneumatic wing and tail deicing boots at the first
signs of ice accumulation is critical for flight in icing
conditions. If we did not take action to include this information,
flight crews could experience reduced controllability of the
aircraft due to adverse aerodynamic effects of ice adhering to the
airplane prior to the first deicing cycle.
(d) What must I do to address this problem?: To address this
problem, you must revise the Limitations Section of the FAA-approved
Airplane Flight Manual (AFM) to include the following requirements
for activation of the ice protection systems. You must accomplish
this action within the next 10 calendar days after the effective
date of this AD, unless already accomplished. You may insert a copy
of this AD in the AFM to accomplish this action:
``Except for certain phases of flight where the AFM
specifies that deicing boots should not be used (e.g., take-off,
final approach, and landing), compliance with the following is
required.
Wing and Tail Leading Edge Pneumatic Deicing Boot
System, if installed, must be activated:
--At the first sign of ice formation anywhere on the aircraft,
or upon annunciation from an ice detector system, whichever occurs
first; and
--The system must either be continued to be operated in the
automatic cycling mode, if available; or the system must be manually
cycled as needed to minimize the ice accretions on the airframe.
The wing and tail leading edge pneumatic deicing boot
system may be deactivated only after:
--Leaving known or observed/detected icing that the flight crew
has visually observed on the aircraft or was identified by the on-
board sensors; and
--After the airplane is determined to be clear of ice.''
Note: The FAA recommends periodic treatment of deicing boots
with approved ice release agents, such as ICEX \TM\, in accorance
with the manufacturer's application instructions.
(e) Can the pilot accomplish the action? Yes. Anyone who holds
at least a private pilot certificate, as authorized by section 43.7
of the Federal Aviation Regulations (14 CFR 43.7), may incorporate
the AFM revisions required by this AD. You must make an entry into
the aircraft records that shows compliance with this AD, in
accordance with section 43.9 of the Federal Aviation Regulations (14
CFR 43.9).
(f) Can I comply with this AD in any other way? Yes.
(1) You may use an alternative method of compliance or adjust
the compliance time if:
(i) Your alternative method of compliance provides an equivalent
level of safety; and
(ii) The Manager, Small Airplane Directorate, approves your
alternative. Submit your request through an FAA Principal
Maintenance Inspector, who may add comments and then send it to the
Manager.
[[Page 14825]]
(2) This AD applies to each airplane identified in the preceding
applicability provision, regardless of whether it has been modified,
altered, or repaired in the area subject to the requirements of this
AD. For airplanes that have been modified, altered, or repaired so
that the performance of the requirements of this AD is affected, the
owner/operator must request approval for an alternative method of
compliance in accordance with paragraph (f)(1) of this AD. The
request should include an assessment of the effect of the
modification, alteration, or repair on the unsafe condition
addressed by this AD; and, if you have not eliminated the unsafe
condition, specific actions you propose to address it.
(g) Where can I get information about any already-approved
alternative methods of compliance? Contact the Small Airplane
Directorate, 901 Locust, Room 301, Kansas City, Missouri 64106;
telephone: (816) 329-4121; facsimile: (816) 329-4091.
(h) What if I need to fly the airplane to another location to
comply with this AD? The FAA can issue a special flight permit under
Secs. 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR
21.197 and 21.199) to operate your airplane to a location where you
can accomplish the requirements of this AD.
(i) When does this amendment become effective? This amendment
becomes effective on May 5, 2000.
Issued in Kansas City, Missouri, on March 10, 2000.
Michael Gallagher,
Manager, Small Airplane Directorate, Aircraft Certification Service.
[FR Doc. 00-6616 Filed 3-17-00; 8:45 am]
BILLING CODE 4910-13-U