Special Conditions: Model C-27J Airplane; Interaction of Systems and Structures, 4353-4357 [E9-1327]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 74, Number 15 (Monday, January 26, 2009)]
[Proposed Rules]
[Pages 4353-4357]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E9-1327]


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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 February 25, 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., 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 
Regulations (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.

[[Page 4354]]

    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 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).

[[Page 4355]]

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] TP26JA09.002

    (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 
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.

[[Page 4356]]

[GRAPHIC] [TIFF OMITTED] TP26JA09.003

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] TP26JA09.004

V' = Clearance speed as defined by Sec.  25.629(b)(2).
V'' = Clearance speed as defined by Sec.  25.629(b)(1).

Where:

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 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,

[[Page 4357]]

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. E9-1327 Filed 1-23-09; 8:45 am]
BILLING CODE 4910-13-P