[Federal Register Volume 77, Number 229 (Wednesday, November 28, 2012)]
[Proposed Rules]
[Pages 70941-70945]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2012-28768]
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Proposed Rules
Federal Register
________________________________________________________________________
This section of the FEDERAL REGISTER contains notices to the public of
the proposed issuance of rules and regulations. The purpose of these
notices is to give interested persons an opportunity to participate in
the rule making prior to the adoption of the final rules.
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Federal Register / Vol. 77, No. 229 / Wednesday, November 28, 2012 /
Proposed Rules
[[Page 70941]]
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. FAA-2012-1246; Notice No. 25-12-16-SC]
Special Conditions: Embraer S.A., Model EMB-550 Airplane;
Interaction of Systems and Structures
AGENCY: Federal Aviation Administration (FAA), DOT.
ACTION: Notice of proposed special conditions.
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SUMMARY: This action proposes special conditions for the Embraer S.A.
Model EMB-550 airplane. This airplane will have a novel or unusual
design feature(s) associated with the interaction of systems and
structures. The applicable airworthiness regulations do not contain
adequate or appropriate safety standards for this design feature. These
proposed special conditions contain the additional safety standards
that the Administrator considers necessary to establish a level of
safety equivalent to that established by the existing airworthiness
standards.
DATES: Send your comments on or before January 14, 2013.
ADDRESSES: Send comments identified by docket number [FAA-2012-1246]
using any of the following methods:
Federal eRegulations Portal: Go to http://www.regulations.gov/ and follow the online instructions for sending
your comments electronically.
Mail: Send comments to Docket Operations, M-30, U.S.
Department of Transportation (DOT), 1200 New Jersey Avenue SE., Room
W12-140, West Building Ground Floor, Washington, DC 20590-0001.
Hand Delivery or Courier: Take comments to Docket
Operations in Room W12-140 of the West Building Ground Floor at 1200
New Jersey Avenue SE., Washington, DC, between 8 a.m. and 5 p.m.,
Monday through Friday, except federal holidays.
Fax: Fax comments to Docket Operations at 202-493-2251.
Privacy: The FAA will post all comments it receives, without
change, to http://www.regulations.gov/, including any personal
information the commenter provides. Using the search function of the
docket Web site, anyone can find and read the electronic form of all
comments received into any FAA docket, including the name of the
individual sending the comment (or signing the comment for an
association, business, labor union, etc.). DOT's complete Privacy Act
Statement can be found in the Federal Register published on April 11,
2000 (65 FR 19477-19478), as well as at http://DocketsInfo.dot.gov/.
Docket: Background documents or comments received may be read at
http://www.regulations.gov/ at any time. Follow the online instructions
for accessing the docket or go to the Docket Operations in Room W12-140
of the West Building Ground Floor at 1200 New Jersey Avenue SE.,
Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday,
except federal holidays.
FOR FURTHER INFORMATION CONTACT: Todd Martin, FAA, Airframe and Cabin
Safety Branch, ANM-115, Transport Airplane Directorate, Aircraft
Certification Service, 1601 Lind Avenue SW., Renton, Washington 98057-
3356; telephone 425-227-1178; facsimile 425-227-1232.
SUPPLEMENTARY INFORMATION:
Comments Invited
We invite interested people to take part in this rulemaking by
sending written comments, data, or views. The most helpful comments
reference a specific portion of the special conditions, explain the
reason for any recommended change, and include supporting data.
We will consider all comments we receive on or before the closing
date for comments. We may change these special conditions based on the
comments we receive.
Background
On May 14, 2009, Embraer S.A. applied for a type certificate for
their new Model EMB-550 airplane. The Model EMB-550 airplane is the
first of a new family of jet airplanes designed for corporate flight,
fractional, charter, and private owner operations. The aircraft has a
conventional configuration with low wing and T-tail empennage. The
primary structure is metal with composite empennage and control
surfaces. The Model EMB-550 airplane is designed for 8 passengers, with
a maximum of 12 passengers. It is equipped with two Honeywell HTF7500-E
medium bypass ratio turbofan engines mounted on aft fuselage pylons.
Each engine produces approximately 6,540 pounds of thrust for normal
takeoff. The primary flight controls consist of hydraulically powered
fly-by-wire elevators, aileron and rudder, controlled by the pilot or
copilot sidestick.
The Model Embraer EMB-550 airplane is equipped with systems that,
directly or as a result of failure or malfunction, affect its
structural performance. Current regulations do not take into account
loads for the airplane due to the effects of systems on structural
performance including normal operation and failure conditions with
strength levels related to probability of occurrence. Special
conditions are needed to account for these features.
Type Certification Basis
Under the provisions of Title 14, Code of Federal Regulations (14
CFR) 21.17, Embraer S.A. must show that the Model EMB-550 airplane
meets the applicable provisions of part 25, as amended by Amendments
25-1 through 25-127 thereto.
If the Administrator finds that the applicable airworthiness
regulations (i.e., 14 CFR part 25) do not contain adequate or
appropriate safety standards for the Model EMB-550 airplane because of
a novel or unusual design feature, special conditions are prescribed
under the provisions of Sec. 21.16.
Special conditions are initially applicable to the model for which
they are issued. Should the type certificate for that model be amended
later to include any other model that incorporates the same or similar
novel or unusual design feature, the special conditions would also
apply to the other model under Sec. 21.101.
In addition to the applicable airworthiness regulations and special
conditions, the Embraer S.A. Model EMB-550 airplane must comply with
the fuel vent and exhaust emission requirements of 14 CFR part 34 and
the
[[Page 70942]]
noise certification requirements of 14 CFR part 36 and the FAA must
issue a finding of regulatory adequacy under Sec. 611 of Public Law
92-574, the ``Noise Control Act of 1972.''
The FAA issues special conditions, as defined in 14 CFR 11.19, in
accordance with Sec. 11.38, and they become part of the type-
certification basis under Sec. 21.17(a)(2).
Novel or Unusual Design Features
The Embraer S.A. Model EMB-550 airplane is equipped with systems
that, directly or as a result of failure or malfunction, affect its
structural performance. Current regulations do not take into account
loads for the airplane due to the effects of systems on structural
performance including normal operation and failure conditions with
strength levels related to probability of occurrence. Special
conditions are needed to account for these features.
These special conditions define criteria to be used in the
assessment of the effects of these systems on structures. The general
approach of accounting for the effect of system failures on structural
performance would be extended to include any system in which partial or
complete failure, alone or in combination with other system partial or
complete failures, would affect structural performance.
Discussion
These airplanes are equipped with systems that, directly or as a
result of failure or malfunction, affect its structural performance.
Current regulations do not take into account loads for the aircraft due
to the effects of systems on structural performance including normal
operation and failure conditions with strength levels related to
probability of occurrence. These special conditions define criteria to
be used in the assessment of the effects of these systems on
structures.
Special conditions have been applied on past airplane programs to
require consideration of the effects of systems on structures. The
regulatory authorities and industry developed standardized criteria in
the Aviation Rulemaking Advisory Committee (ARAC) forum based on the
criteria defined in Advisory Circular 25.672, Active Flight Controls,
dated November 11, 1983. The ARAC recommendations have been
incorporated in European Aviation Safety Agency (EASA) Certification
Specifications (CS) 25.302 and CS 25 Appendix K. FAA rulemaking on this
subject is not complete, thus the need for the special conditions.
The proposed special conditions are similar to those previously
applied to other airplane models and to CS 25.302. The major
differences between these proposed special conditions and the current
CS 25.302 are as follows:
1. Both these special conditions and CS 25.302 specify the design
load conditions to be considered. In paragraphs 2(a)(1) and 2(b)(2)(i)
of these special conditions, the special conditions clarify that, in
some cases, different load conditions are to be considered due to other
special conditions or equivalent level of safety findings.
2. Paragraph 2(b)(2)(i) of these special conditions include the
additional ground-handling conditions of Sec. Sec. 25.493(d) and
25.503. These conditions are added in case the Embraer S.A. Model EMB-
550 airplane has systems that affect braking and pivoting.
3. Both CS 25.302 and paragraph (2)(d) of these special conditions
allow consideration of the probability of being in a dispatched
configuration when assessing subsequent failures and potential
``continuation of flight'' loads. However, these special conditions
also allow using probability when assessing failures that induce loads
at the ``time of occurrence,'' whereas CS 25.302 does not.
Applicability
As discussed above, these special conditions are applicable to the
Embraer S.A. Model EMB-550 airplane. Should Embraer S.A. apply at a
later date for a change to the type certificate to include another
model incorporating the same novel or unusual design feature, the
special conditions would apply to that model as well.
Conclusion
This action affects only certain novel or unusual design features
on one model of airplanes. It is not a rule of general applicability.
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety, Reporting and recordkeeping
requirements.
The authority citation for these special conditions is as follows:
Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.
The Proposed Special Conditions
Accordingly, the Federal Aviation Administration (FAA) proposes the
following special conditions as part of the type certification basis
for Embraer S.A. Model EMB-550 airplanes to address the effects of
systems on structures.
1. General Interaction of Systems and Structures
For airplanes equipped with systems that affect structural
performance, either directly or as a result of a failure or
malfunction, the influence of these systems and their failure
conditions must be taken into account when showing compliance with the
requirements of Title 14, Code of Federal Regulations (14 CFR) part 25
subparts C and D.
The following criteria must be used for showing compliance with
these special conditions for airplanes equipped with flight control
systems, autopilots, stability augmentation systems, load alleviation
systems, fuel management systems, and other systems that either
directly or as a result of failure or malfunction affect structural
performance. If these special conditions are used for other systems, it
may be necessary to adapt the criteria to the specific system.
(a) The criteria defined herein only address the direct structural
consequences of the system responses and performances and cannot be
considered in isolation but should be included in the overall safety
evaluation of the airplane. These criteria may in some instances
duplicate standards already established for this evaluation. These
criteria are only applicable to structure in which failure could
prevent continued safe flight and landing. Specific criteria that
define acceptable limits on handling characteristics or stability
requirements when operating in the system degraded or inoperative mode
are not provided in these special conditions.
(b) The following definitions are applicable to these special
conditions.
(1) Structural performance: Capability of the airplane to meet the
structural requirements of 14 CFR part 25.
(2) Flight limitations: Limitations that can be applied to the
airplane flight conditions following an in-flight occurrence and that
are included in the flight manual (e.g., speed limitations and
avoidance of severe weather conditions).
(3) Operational limitations: Limitations, including flight
limitations, that can be applied to the airplane operating conditions
before dispatch (e.g., fuel, payload, and Master Minimum Equipment List
limitations).
(4) Probabilistic terms: The probabilistic terms (i.e., probable,
improbable, and extremely improbable) used in these special conditions
are the same as those used in Sec. 25.1309.
(5) Failure condition: The term ``failure condition'' is the same
as that
[[Page 70943]]
used in Sec. 25.1309. However, these special conditions apply only to
system failure conditions that affect the structural performance of the
airplane (e.g., system failure conditions that induce loads, change the
response of the airplane to inputs such as gusts or pilot actions, or
lower flutter margins).
2. Effect on Systems and Structures
The following criteria are used in determining the influence of a
system and its failure conditions on the airplane structure.
(a) System fully operative. With the system fully operative, the
following apply:
(1) Limit loads must be derived in all normal operating
configurations of the system from all the limit conditions specified in
Subpart C (or defined by special condition or equivalent level of
safety in lieu of those specified in Subpart C), taking into account
any special behavior of such a system or associated functions or any
effect on the structural performance of the airplane that may occur up
to the limit loads. In particular, any significant nonlinearity (rate
of displacement of control surface, thresholds or any other system
nonlinearities) must be accounted for in a realistic or conservative
way when deriving limit loads from limit conditions.
(2) The airplane must meet the strength requirements of part 25
(static strength, residual strength), using the specified factors to
derive ultimate loads from the limit loads defined above. The effect of
nonlinearities must be investigated beyond limit conditions to ensure
the behavior of the system presents no anomaly compared to the behavior
below limit conditions. However, conditions beyond limit conditions
need not be considered when it can be shown that the airplane has
design features that will not allow it to exceed those limit
conditions.
(3) The airplane must meet the aeroelastic stability requirements
of Sec. 25.629.
(b) System in the failure condition. For any system failure
condition not shown to be extremely improbable, the following apply:
(1) At the time of occurrence. Starting from 1-g level flight
conditions, a realistic scenario, including pilot corrective actions,
must be established to determine the loads occurring at the time of
failure and immediately after failure.
(i) For static strength substantiation, these loads, multiplied by
an appropriate factor of safety that is related to the probability of
occurrence of the failure, are ultimate loads to be considered for
design. The factor of safety (FS) is defined in Figure 1.
[GRAPHIC] [TIFF OMITTED] TP28NO12.001
(ii) For residual strength substantiation, the airplane must be
able to withstand two-thirds of the ultimate loads defined in paragraph
2(b)(1)(i) of these special conditions. For pressurized cabins, these
loads must be combined with the normal operating differential pressure.
(iii) Freedom from aeroelastic instability must be shown up to the
speeds defined in Sec. 25.629(b)(2). For failure conditions that
result in speeds beyond VC/MC, freedom from
aeroelastic instability must be shown to increased speeds, so that the
margins intended by Sec. 25.629(b)(2) are maintained.
(iv) Failures of the system that result in forced structural
vibrations (e.g., oscillatory failures) must not produce loads that
could result in detrimental deformation of primary structure.
(2) For the continuation of the flight. For the airplane, in the
system failed state and considering any appropriate reconfiguration and
flight limitations, the following apply:
(i) The loads derived from the following conditions (or conditions
defined by special conditions or equivalent level of safety in lieu of
the following special conditions) at speeds up to VC/
MC, or the speed limitation prescribed for the remainder of
the flight, must be determined:
(A) The limit symmetrical maneuvering conditions specified in
Sec. Sec. 25.331 and 25.345.
(B) The limit gust and turbulence conditions specified in
Sec. Sec. 25.341 and 25.345.
(C) The limit rolling conditions specified in Sec. 25.349 and the
limit unsymmetrical conditions specified in Sec. Sec. 25.367,
25.427(b), and 25.427(c).
(D) The limit yaw maneuvering conditions specified in Sec. 25.351.
(E) The limit ground loading conditions specified in Sec. Sec.
25.473, 25.491, 25.493(d) and 25.503.
(ii) For static strength substantiation, each part of the structure
must be able to withstand the loads in paragraph 2(b)(2)(i) of these
special conditions multiplied by a factor of safety depending on the
probability of being in this failure state. The factor of safety (FS)
is defined in Figure 2.
[[Page 70944]]
[GRAPHIC] [TIFF OMITTED] TP28NO12.002
Qj = (Tj)(Pj) where:
Tj = Average time spent in failure condition j (in hours)
Pj = Probability of occurrence of failure mode j (per
hour)
Note: If Pj is greater than 10-3 per
flight hour then a 1.5 factor of safety must be applied to all limit
load conditions specified in Subpart C.
(iii) For residual strength substantiation, the airplane must be
able to withstand two-thirds of the ultimate loads defined in paragraph
2(b)(2)(ii) of the special conditions. For pressurized cabins, these
loads must be combined with the normal operating differential pressure.
(iv) If the loads induced by the failure condition have a
significant effect on fatigue or damage tolerance then their effects
must be taken into account.
(v) Freedom from aeroelastic instability must be shown up to a
speed determined from Figure 3. Flutter clearance speeds V' and V'' may
be based on the speed limitation specified for the remainder of the
flight using the margins defined by Sec. 25.629(b).
[GRAPHIC] [TIFF OMITTED] TP28NO12.003
V' = Clearance speed as defined by Sec. 25.629(b)(2).
V'' = Clearance speed as defined by Sec. 25.629(b)(1).
Qj = (Tj)(Pj) where:
Tj = Average time spent in failure condition j (in hours)
Pj = Probability of occurrence of failure mode j (per
hour)
Note: If Pj is greater than 10-3 per flight
hour, then the flutter clearance speed must not be less than V''.
(vi) Freedom from aeroelastic instability must also be shown up to
V' in Figure 3 above, for any probable system failure condition
combined with any damage required or selected for investigation by
Sec. 25.571(b).
(3) Consideration of certain failure conditions may be required by
other sections of 14 CFR part 25 regardless of calculated system
reliability. Where analysis shows the probability of these failure
conditions to be less than 10-9, criteria other than those
specified in this paragraph may be used for structural substantiation
to show continued safe flight and landing.
(c) Failure indications. For system failure detection and
indication, the following apply:
(1) The system must be checked for failure conditions, not
extremely improbable, that degrade the structural capability below the
level required by 14 CFR part 25 or significantly reduce the
reliability of the remaining system. As far as reasonably practicable,
the flightcrew must be made aware of these failures before flight.
Certain elements of the control system, such as mechanical and
hydraulic components, may use special periodic inspections, and
electronic components may use daily checks, in lieu of detection and
indication systems to achieve the objective of this requirement. These
certification maintenance requirements must be limited to components
that are not readily detectable by normal detection and indication
systems and where service history shows that inspections will provide
an adequate level of safety.
(2) The existence of any failure condition, not extremely
improbable, during flight that could significantly affect the
structural capability of the airplane and for which the associated
reduction in airworthiness can be minimized by suitable flight
limitations, must be signaled to the flightcrew. For example, failure
conditions that result in a factor of safety between the airplane
strength and the loads of Subpart C below 1.25, or flutter margins
below V'',
[[Page 70945]]
must be signaled to the flightcrew during flight.
(d) Dispatch with known failure conditions. If the airplane is to
be dispatched in a known system failure condition that affects
structural performance, or affects the reliability of the remaining
system to maintain structural performance, then the provisions of these
special conditions must be met, including the provisions of paragraph
2(a) for the dispatched condition, and paragraph 2(b) for subsequent
failures. Expected operational limitations may be taken into account in
establishing Pj as the probability of failure occurrence for
determining the safety margin in Figure 1 of these special conditions.
Flight limitations and expected operational limitations may be taken
into account in establishing Qj as the combined probability
of being in the dispatched failure condition and the subsequent failure
condition for the safety margins in Figures 2 and 3 of these special
conditions. These limitations must be such that the probability of
being in this combined failure state and then subsequently encountering
limit load conditions is extremely improbable. No reduction in these
safety margins is allowed if the subsequent system failure rate is
greater than 10-3 per hour.
Issued in Renton, Washington, on November 21, 2012.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. 2012-28768 Filed 11-27-12; 8:45 am]
BILLING CODE 4910-13-P