Special Conditions: Alenia Aeronautica Model C-27J Airplane; Interaction of Systems and Structures, 44278-44281 [E9-20697]

Agencies

• Federal Aviation Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 74, Number 166 (Friday, August 28, 2009)]
[Rules and Regulations]
[Pages 44278-44281]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E9-20697]


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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 25

[Docket No. NM398; Special Conditions No. 25-390-SC]


Special Conditions: Alenia Aeronautica Model C-27J Airplane; 
Interaction of Systems and Structures

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are issued for the Alenia Model C-27J 
airplane. This airplane will have novel or unusual design features when 
compared to the state of technology described in the airworthiness 
standards for transport-category airplanes. These special conditions 
pertain to the effects of novel or unusual design features such as 
effects on the structural performance of the airplane.
    The applicable airworthiness regulations do not contain adequate or 
appropriate safety standards for this design feature. These 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: Effective Date: September 28, 2009.

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: 

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 Alenia model C-27J. The Alenia model C-27J 
is a twin-turbopropeller, cargo-transport aircraft with a maximum 
takeoff weight of 67,240 pounds.

Type Certification Basis

    Under the provisions of Title 14, Code of Federal Regulations (14 
CFR) 21.17 and the bilateral agreement between the U.S. and Italy, 
Alenia Aeronautica must show that the Alenia model 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 Sec.  25.1317.
    If the Administrator finds that existing airworthiness regulations 
do not adequately or appropriately address safety standards for the 
Alenia model C-27J due to a novel or unusual design feature, we 
prescribe special conditions under provisions of Sec.  21.16.
    In addition to the applicable airworthiness regulations and special 
conditions, the Alenia model 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. In addition, 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, 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).
    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 Alenia model 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. These special 
conditions for the Alenia model C-27J 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.
    These special conditions were 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 these special conditions in Notice of Proposed Amendment (NPA) 
25C-199. When Ente Nazionale per l'Aviazione Civile (ENAC) certified 
the Alenia model C-27J they applied NPA 25C-199, issued July 3, 1997.

[[Page 44279]]

Discussion

    The Alenia model 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. Special conditions are 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.
    These special conditions require that the airplane meet the 
structural requirements of subparts C and D of part 25 when the 
airplane systems are fully operative. These special conditions also 
require 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.

Discussion of Comments

    Notice of proposed special conditions no. 25-09-01-SC for the 
Alenia model C-27J airplane was published in the Federal Register on 
May 4, 2009. No comments were received, and the special conditions are 
adopted as proposed.

Applicability

    As discussed above, these special conditions are applicable to the 
Alenia model 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 special conditions apply to 
that model as well.

Conclusion

    This action affects only certain novel or unusual design features 
of the Alenia model 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.

0
The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704.

The Special Conditions

0
Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued as part of 
the type-certification basis for the Alenia model C-27J.

1. General

    (a) The Alenia model 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 Title 14 of the Code of 
Federal Regulations (14 CFR), part 25. 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, flutter-control 
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.
    (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 these special conditions.
    (c) Depending upon the specific characteristics of the airplane, 
additional studies may be required, that go beyond the criteria 
provided in these special conditions, 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 these special 
conditions.

Structural Performance

    Capability of the airplane to meet the structural requirements of 
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 these special conditions 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, 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 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 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.

[[Page 44280]]

    (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] TR28AU09.086

    (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 at 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] TR28AU09.087


[[Page 44281]]


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] TR28AU09.088

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 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 August 20, 2009.
Ali Bahrami,
Manager, Transport Airplane Directorate, Aircraft Certification 
Service.
[FR Doc. E9-20697 Filed 8-27-09; 8:45 am]
BILLING CODE 4910-13-P