[Federal Register: May 4, 2009 (Volume 74, Number 84)]
[Proposed Rules]
[Page 20427-20431]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr04my09-14]
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DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. NM398; Notice No. 25-09-01-SC]
Special Conditions: Model C-27J 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 Alenia Model
C-27J airplane. This airplane has novel or unusual design features when
compared to the state of technology described in the airworthiness
standards for transport-category airplanes. These design features
include electronic flight-control systems. These special conditions
pertain to the effects of novel or unusual design features such as
effects on the structural performance of the airplane. We have issued
additional special conditions for other novel or unusual design
features of the C-27J.
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: We must receive your comments by June 3, 2009.
ADDRESSES: You must mail two copies of your comments to: Federal
Aviation Administration, Transport Airplane Directorate, Attn: Rules
Docket (ANM-113), Docket No. NM398, 1601 Lind Avenue, SW., Renton,
Washington 98057-3356. You may deliver two copies to the Transport
Airplane Directorate at the above address. You must mark your comments:
Docket No. NM398. You can inspect comments in the Rules Docket
weekdays, except Federal holidays, between 7:30 a.m. and 4 p.m.
FOR FURTHER INFORMATION CONTACT: Holly Thorson, FAA, International
Branch, ANM-116, Transport Airplane Directorate, Aircraft Certification
Service, 1601 Lind Avenue, SW.,
[[Page 20428]]
Renton, Washington 98057-3356; telephone (425) 227-1357, facsimile
(425) 227-1149.
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 ask
that you send us two copies of written comments.
We will file in the docket all comments we receive, as well as a
report summarizing each substantive public contact with FAA personnel
concerning these special conditions. You can inspect the docket before
and after the comment closing date. If you wish to review the docket in
person, go to the address in the ADDRESSES section of this preamble
between 7:30 a.m. and 4 p.m., Monday through Friday, except Federal
holidays.
We will consider all comments we receive on or before the closing
date for comments. We will consider comments filed late if it is
possible to do so without incurring expense or delay. We may change
these special conditions based on the comments we receive.
If you want the FAA to acknowledge receipt of your comments on this
proposal, include with your comments a self-addressed, stamped postcard
on which the docket number appears. We will stamp the date on the
postcard and mail it back to you.
Background
On March 27, 2006, the European Aviation Safety Agency (EASA)
forwarded to the FAA an application from Alenia Aeronautica of Torino,
Italy, for U.S. type certification of a twin-engine commercial
transport designated as the Model C-27J. The C-27J is a twin-
turbopropeller, cargo-transport aircraft with a maximum takeoff weight
of 30,500 kilograms.
Type Certification Basis
Under the provisions of Section 21.17 of Title 14 Code of Federal
Regulation (14 CFR) and the bilateral agreement between the U.S. and
Italy, Alenia Aeronautica must show that the C-27J meets the applicable
provisions of 14 CFR part 25, as amended by Amendments 25-1 through 25-
87. Alenia also elects to comply with Amendment 25-122, effective
September 5, 2007, for 14 CFR 25.1317.
If the Administrator finds that existing airworthiness regulations
do not adequately or appropriately address safety standards for the C-
27J due to a novel or unusual design feature, we prescribe special
conditions under provisions of 14 CFR 21.16.
In addition to the applicable airworthiness regulations and special
conditions, the C-27J must comply with the fuel-vent and exhaust-
emission requirements of 14 CFR part 34 and the noise-certification
requirements of 14 CFR part 36, and the FAA must issue a finding of
regulatory adequacy pursuant to Sec. 611 of Public Law 92-574, the
``Noise Control Act of 1972.''
The FAA issues special conditions, under Sec. Sec. 11.19 and
11.38, and they become part of the type-certification basis under Sec.
21.17(a)(2).
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 also apply to
the other model under Sec. 21.101.
Novel or Unusual Design Features
The C-27J incorporates several novel or unusual design features.
Because of rapid improvements in airplane technology, the existing
airworthiness regulations do not adequately or appropriately address
safety standards for these design features. This proposed special
condition for the C-27J contains the additional safety standards that
the Administrator considers necessary to establish a level of safety
equivalent to that established by the existing airworthiness standards.
This special condition was derived initially from standardized
requirements developed by the Aviation Rulemaking Advisory Committee
(ARAC), comprised of representatives of the FAA, Europe's Joint
Aviation Authorities (JAA, now replaced by the European Aviation Safety
Agency (EASA)), and industry. From the initial proposal, the JAA
proposed this special condition in Notice of Proposed Amendment (NPA)
25C-199. When Ente Nazionale per l'Aviazione Civile (ENAC) certified
the C-27J they applied NPA 25C-199, issued July 3, 1997.
Discussion
The Alenia C-27J is equipped with systems that affect the
airplane's structural performance, either directly or as a result of
failure or malfunction. That is, the airplane's systems affect how it
responds in maneuver and gust conditions, and thereby affect its
structural capability. These systems may also affect the aeroelastic
stability of the airplane. Such systems represent a novel and unusual
feature when compared to the technology described in the current
airworthiness standards. A special condition is needed to require
consideration of the effects of systems on the structural capability
and aeroelastic stability of the airplane, in both the normal and the
failed states.
This special condition requires that the airplane meet the
structural requirements of subparts C and D of 14 CFR part 25 when the
airplane systems are fully operative. The special condition also
requires that the airplane meet these requirements taking into
consideration failure conditions. In some cases, reduced margins are
allowed for failure conditions based on system reliability.
Applicability
As discussed above, these proposed special conditions are
applicable to the C-27J. Should Alenia apply at a later date for a
change to the type certificate to include another model incorporating
the same novel or unusual design features, these proposed special
conditions apply to that model as well under the provisions of Sec.
21.101.
Conclusion
This action affects only certain novel or unusual design features
of the Alenia C-27J. It is not a rule of general applicability, and it
affects only the applicant that applied to the FAA for approval of
these features on the airplane.
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 Administrator of the Federal Aviation
Administration (FAA) proposes the following special conditions as part
of the type-certification basis for the C-27J.
1. General
(a) The C-27J is equipped with systems that affect the airplane's
structural performance either directly or as a result of failure or
malfunction. The influence of these systems and their failure
conditions must be taken into account when showing compliance with
requirements of subparts C and D of part 25 of Title 14 of the Code of
Federal Regulations (CFR). The following criteria must be used for
showing compliance with this proposed special condition for airplanes
equipped with
[[Page 20429]]
flight control systems, autopilots, stability-augmentation systems,
load-alleviation systems, flutter-control systems, fuel-management
systems, and other systems that either directly, or as a result of
failure or malfunction, affect structural performance. If this proposed
special condition is used for other systems, it may be necessary to
adapt the criteria to the specific system.
(b) The criteria defined here address only 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 the failure of which 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 this special condition.
(c) Depending upon the specific characteristics of the airplane,
additional studies may be required, that go beyond the criteria
provided in this special condition, to demonstrate the capability of
the airplane to meet other realistic conditions, such as alternative
gust or maneuver descriptions, for an airplane equipped with a load-
alleviation system.
(d) The following definitions are applicable to this special
condition.
Structural performance: Capability of the airplane to meet the
structural requirements of 14 CFR part 25.
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, avoidance of
severe weather conditions, etc.).
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).
Probabilistic terms: The probabilistic terms (probable, improbable,
extremely improbable) used in this special condition are the same as
those used in Sec. 25.1309.
Failure condition: The term ``failure condition'' here is the same
as that used in Sec. 25.1309. However, this appendix applies 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 variables such as gusts or pilot actions,
or reduce flutter margins).
2. Effects of Systems on Structures
(a) General. The following criteria determine the influence of a
system and its failure conditions on the airplane structure.
(b) 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, 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 14 CFR 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.
(c) 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 (F.S.) is defined in Figure 1.
[GRAPHIC] [TIFF OMITTED] TP04MY09.000
(ii) For residual-strength substantiation, the airplane must be
able to withstand two-thirds of the ultimate loads defined in
subparagraph (c)(1)(i).
(iii) Freedom from aeroelastic instability must be shown up to the
[[Page 20430]]
speeds defined in Sec. 25.629(b)(2). For failure conditions that
result in speed increases 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 (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 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.
25.331 and in Sec. 25.345.
(B) The limit-gust-and-turbulence conditions specified in Sec.
25.341 and in Sec. 25.345.
(C) The limit-rolling conditions specified in Sec. 25.349, and the
limit-unsymmetrical conditions specified in Sec. 25.367 and Sec.
25.427(b) and (c).
(D) The limit-yaw-maneuvering conditions specified in Sec. 25.351.
(E) The limit-ground-loading conditions specified in Sec. 25.473
and Sec. 25.491.
(ii) For static-strength substantiation, each part of the structure
must be able to withstand the loads in subparagraph (2)(i) of this
paragraph, multiplied by a factor of safety depending on the
probability of being in this failure state. The factor of safety is
defined in Figure 2.
[GRAPHIC] [TIFF OMITTED] TP04MY09.001
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
subparagraph (c)(2)(ii).
(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] TP04MY09.002
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'
[[Page 20431]]
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 subparts of 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.
(d) 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 part 25, or that significantly reduce the reliability
of the remaining system. To the extent practicable, these failures must
be detected and annunciated to the flight crew 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 warning systems, to achieve
the objective of this requirement. These certification-maintenance
requirements must be limited to components that are not readily
detectable by normal warning systems, and where service history shows
that inspections 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 flight crew. 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'', must be
signaled to the crew during flight.
(e) 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 Sec.
25.302 must be met for the dispatched condition and for subsequent
failures. 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.
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 December 31, 2008.
Linda Navarro,
Acting Manager, Transport Airplane Directorate, Aircraft Certification
Service.
[FR Doc. E9-10164 Filed 5-1-09; 8:45 am]
BILLING CODE 4910-13-P