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### Final Special Condition
Federal Register Information

Header Information

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 Ai rplane; Interaction of Systems and Structures

Preamble Information

AGENCY: Federal Aviation Admi nistration (FAA), DOT.

ACTION: Final special conditions.

SUMMARY: These special conditions are iss ued for the Alen ia Model C-27J airplane. This airplane wi ll have novel or unusual desig n features when compared to the state of technology described in the ai rworthiness standar ds for transportcategory airplanes. These special conditions pertain to the effects of novel or unusual design features such as effects on the struct ural perform ance of the airplane. The applicable airwor thiness regulations do not contain adequate or appropriate safety standards for this design featur e. These special conditions contain the additional safety st andards that the Ad ministrator considers necessary to establish a level of safety equivalent to that establishe d by the existing

airworthiness standards.

DATES: Effective Date: S eptember 28, 2009. PDF Format: Pa g e 1 of 9 Special Conditions: Alenia Aeronautica Model C-27J Airplane; Interaction of

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...FOR FURTHER INFORMATION CONTACT : Holly Thorson, FA A, International Branch, ANM-116, Transport Ai rplane Directorate, Aircra ft Certification Service, 1601 Lind Avenue, SW., R enton, Washington 98057-3356; telephone (425) 227- 1357, facsimile ( 425) 227-1149.

SUPPLEMENTARY INFORMATION:

Background

On March 27, 2006, the Eur opean Aviation Safety Ag ency (EASA) fo rwarded to the FAA an application from Al enia Aeronautica of Torino, Italy, for U.S. type certification of a twin-engi ne commercial transport desig nated 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 Ti tle 14, Code of Feder al Regulations (14 CFR) 21.17 and the bilateral agreement betw een the U.S. and Italy, Aleni a Aeronautica must show that the Alenia model C-27J meets the appl icable provisions of 14 CFR part 25, as amended by Amendments 25- 1 through 25-87. Al enia also elec ts to comply

with Amendment 25- 122, effective September 5, 2007, for Sec. 25.1317.

If the Administrator finds t hat existing airworthiness re gulations do not adequately or appropriately address sa fety standards for the Aleni a model C-27J due to a novel or unusual design featur e, we prescribe special c onditions under provisions

of Sec. 21.16. In addition to the applicabl e airworthiness regulations and special conditions, the Alenia model C-27J must comply wi th the fuel-vent and exhaust-emission requirements of 14 CFR par t 34 and the noise- certification requi rements of 14 CFR part 36. In addition, the FAA must issue a findi ng of regulatory adequacy pursuant to Sec. 611 of P ublic Law 92-574, the ``Nois e Control Act of 1972.'' The FAA issues special condi tions, as defined in 14 CFR 11.19, in accordance with Sec. 11.38, and t hey become part of the type- certificat ion basis under Sec. 21.17(a)(2). Special conditions are initia lly applicable to t he model for which they are issued. Should the type certificate for that model be amended la ter to include any other model that incorporat es 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 se veral novel or unusual design features. Because of rapid improvement s in airplane tec hnology, the existi ng airworthiness regulations do not adequately or appropriately address sa fety standards for these design features. These special conditions for the Alenia mode l C-27J contain the additional safety st andards that the Ad ministrator considers necessary to establish a level of safety equivalent to that establishe d by the existing

airworthiness standards. These special conditions we re derived initially from standardized requirements Pa g e 2 of 9 Special Conditions: Alenia Aeronautica Model C-27J Airplane; Interaction of

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...developed by the Aviation Rulemaking Advi sory Committee (ARA C), comprised of representatives of the FA A, Europe's Joint Aviati on Authoritie s (JAA), now replaced by the European Aviation Safety Agency (EASA), and i ndustry. From the initial proposal, t he JAA proposed these special condi tions in Notice of Proposed Amendment (NPA) 25C-199. When Ente Nazionale per l'Av iazione Civile (ENAC)

certified the Alenia model C- 27J they applied NPA 25C-199 , issued July 3, 1997.

Discussion

The Alenia model C-27J is equipped with syst ems that affect the airplane's structural performance, either directly or as a re sult of failure or malfunction. That is, the airplane's systems af fect how it responds in maneuver and gus t conditions, and thereby affect its stru ctural capability. These syst ems may also affect the aeroelastic stability of the airplane. Such systems represent a novel and unusual feature when compared to t he technology described in the current airworthiness standards. Special conditions are needed to require consid eration of the effects of systems on the structural capability and aeroel astic stability of the airplane, in

both the normal and th e failed states. These special conditions require that the airplane meet the structural requirements of subpar ts C and D of part 25 when t he airplane systems are fully operative. These special c onditions also require that the airplane meet these requirements taking into c onsideration failure conditions. In some cases, reduced margins are allowed for failure conditi ons based on system reliability.

Discussion of Comments

Notice of proposed specia l conditions no. 25-09-01-SC for the Alenia model C-27J airplane was publis hed in the Federal Register on May 4, 2009. No comments were received, and the special cond itions are adopt ed as proposed.

Applicability

As discussed above, these special conditions are app licable to the Alenia model C-27J. Should Alenia apply at a later date for a change to the type certificate to

include another mode l 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 desi gn features of the Alenia

model C-27J. It is not a ru le of general applicability, and it affects only the applicant that applied to the FAA for approval of these f eatures on the airplane.

List of Subjects in 14 CFR Part 25

Aircraft, Aviation safety, Reporti ng and recordkeeping requirements.

The authority citation for these spec ial conditions is as follows:

Authority : 49 U.S.C. 106(g), 40113, 44701, 44702 , 44704. Pa g e 3 of 9 Special Conditions: Alenia Aeronautica Model C-27J Airplane; Interaction of

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...Final Special Condit ions Information The Special Conditions

Accordingly, pursuant to t he authority delegated to me by the Administrator, the following special conditions ar e 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 t hat affect the airplane's structural performance either directly or as a result of failure or malfunction. The influence of these system s 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 R egulations (14 CFR), part 25. The following criteria must be used for showing compliance with these special conditi ons for airplanes equipped with flight contro l systems, autopilots, stability - augmentation systems, loadalleviation systems, flutte r-control systems, fuel-manage ment systems, and other systems that either directly, or as a result of failure or malfunction, affect structural performance. If thes e 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 di rect structural consequences of the system responses and performances, and cannot be considered in isolation,

but should be included in t he overall safety evaluatio n of the airplane. These criteria may, in some in stances, duplicate standards al ready established for this

evaluation. These criteria ar e only applicable to structure the failur e of which could prevent continued safe flight and landing. Specific criteria that define acceptable limits on handling characterist ics or stability requirement s, when operating in the system-degraded or inoperati ve mode, are not provid ed in these special

conditions. (c) Depending upon the specific characteristics of the ai rplane, additional studies may be required, that go bey ond the criteria provided in these special conditions,

to demonstrate the ca pability 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 definiti ons are applicable to thes e special conditions.

Structural Performance

Capability of the ai rplane to meet the structur al requirements of part 25.

Flight Limitations

Limitations that can be applied to the airplane flight condi tions following an in-flight occurrence, and that are in cluded in the flight manual (e.g., sp eed limitations,

avoidance of severe weat her conditions, etc.).

Operational Limitations

Limitations, including fli ght limitations, that can be applied to the airplane Pa g e 4 of 9 Special Conditions: Alenia Aeronautica Model C-27J Airplane; Interaction of

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...operating conditions before dispatch (e.g., fuel , payload, and Master Minimum Equipment List limitations).

Probabilistic Terms

The probabilistic terms (probable, impr obable, extremely im probable) used in these special conditions are the same as those used in Sec. 25.1309.

Failure Condition

The term ``failure condition'' here is t he same as that us ed in Sec. 25.1309. However, these special co nditions apply only to system - failure conditions that affect the structural perf ormance of the airp lane (e.g., system-failure conditions that induce loads, change the re sponse of the airplane to variables such as gusts or pilot actions, or r educe flutter margins).

2. Effects of Systems on Structures

(a) General. The following criteria determine the in fluence of a system and its

failure conditions on the airplane structure. (b) System fully operative. With the system full y operative, the following apply: (1) Limit loads must be der ived in all normal operati ng configurations of the system from all the limit cond itions specified in Subpart C, taking into account any special behavior of such a system or associated function s, or any effect on the structural performance of the airplane that may occur up to the limit loads. In particular, any significant nonl inearity (rate of displace ment of control surface, thresholds, or any other system nonlinearities) mu st be accounted for in a realistic or conservative way w hen deriving limit loads fr om limit conditions. (2) The airplane must meet t he strength requirements of part 25 (sta tic strength, residual strength) using the s pecified factors to derive ul timate loads fr om the limit

loads defined above. The effect of nonlinearit ies must be investig ated beyond limit

conditions to ensure the behavior of the system presents no anomaly compared to

the behavior below li mit conditions. Howeve r, conditions beyond limit conditions

need not be consider ed when it can be shown that the ai rplane has design

features that will not allow it to exceed t hose limit conditions. (3) The airplane must meet the aeroelastic-stability requ irements of Sec. 25.629. (c) System in the failure condition. For any system-failu re condition not shown to be extremely impr obable, the follow ing apply: (1) At the time of occurrenc e. Starting from 1-g level-fl ight conditions, a realistic scenario, including pilot corrective actions, must be established to determine the loads occurring at the time of failure and im mediately after failure. (i) For static-strength substa ntiation, these lo ads, multiplied by an appropriate factor of safety that is re lated 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. Pa g e 5 of 9 Special Conditions: Alenia Aeronautica Model C-27J Airplane; Interaction of

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...(ii) For residual-strength s ubstantiation, the airplane mu st be able to withstand

two-thirds of the ultimate loads defined in subparagr aph (c)(1)(i). (iii) Freedom from aer oelastic instability must be s hown up to the speeds defined in Sec. 25.629(b)(2). For fa ilure conditions that result in speed increases beyond VC/MC, freedom from aeroel astic instability must be shown at increased speeds, so that the margins intended by Se c. 25.629(b)(2) ar e maintained. (iv) Failures of the system that result in forced struct ural vibrations (oscillatory failures) must not produce lo ads that could result in detrimental deformation of primary structure. (2) For the continuation of th e flight. For the ai rplane in the syst em-failed state, and considering any app ropriate reconfigurat ion and flight limita tions, the following apply: (i) The loads derived from the following conditions at spee ds up to VC/MC, or the speed limitation prescribed fo r the remainder of the fli ght, must be determined: (A) The limit-symmetrical-m aneuvering conditions specifi ed 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-rollin g conditions specified in Sec. 25.349, and the limitunsymmetrical conditions s pecified in Sec. 25.367 and Sec. 25.427(b) and (c). (D) The limit-yaw-maneuvering conditi ons specified in Sec. 25.351. (E) The limit-ground-loading conditions spec ified in Sec. 25.473 and Sec. 25.491. (ii) For static-strength subs tantiation, each part of the structure mu st be able to

withstand the load s in subparagraph (2)(i) of this paragraph, multipli ed by a factor of safety depending on t he probability of being in this fa ilure state. The factor of safety is defined in Figure 2. Pa g e 6 of 9 Special Conditions: Alenia Aeronautica Model C-27J Airplane; Interaction of

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...Qj = (Tj)(Pj)

Where:

Tj = Average time spent in fa ilure 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 sa fety must be applied to all limit-load conditi ons 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 si gnificant effect on fatigue or damage tolerance, th en their effects must be taken into account. (v) Freedom from aeroelast ic instability must be sh own up to a speed determined from Figure 3. Flutter-cl earance speeds V' and V'' ma y be based on the speed limitation specified fo r the remainder of t he flight using the margins defined by Sec. 25.629(b). Pa g e 7 of 9 Special Conditions: Alenia Aeronautica Model C-27J Airplane; Interaction of

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...V' = Clearance speed as def ined by Sec. 25.629(b)(2). V'' = Clearance speed as defined by Se c. 25.629(b)(1). Qj = (Tj)(Pj)

Where:

Tj = Average time spent in fa ilure condition j (in hours). Pj = Probability of occurrence of failure mode j (per hour).

Note: If Pj is greater t han 10-3 per flight hour, then the flutter clearance speed

must not be le ss than V''.

(vi) Freedom from aeroel astic instability must also be shown, up to V' in Figure 3 above, for any probable syst em-failure condition comb ined with any damage required or selected for investi gation by Sec. 25.571(b). (3) Consideration of certai n failure conditions may be re quired by other subparts of part 25 regardle ss of calculated syst em reliability. Wher e analysis shows the probability of these fa ilure conditions to be less than 10-9, criteria other than those specified in this paragrap h may be used for structural substantiation to show continued safe flight and landing. (d) Failure indications. For system-failu re detection and indica tion, the following apply: (1) The system must be checked for fail ure conditions, not extremely improbable, that degrade the struct ural capability below the level required by part 25, or that significantly reduce the re liability of the remaini ng system. To the extent practicable, these failures must be detect ed and annunciated to the flight crew before flight. Certain elem ents of the control system, such as mechanical and hydraulic components, may us e special periodic inspections, and electronic components may use daily checks, in li eu of warning systems, to achieve the objective of this r equirement. Thes e certification-mainten ance requirements must be limited to compon ents that are not readily de tectable by normal warning systems, and where service history show s that inspections provide an adequate level of safety.

(2) The existence of any fail ure condition, not extremel y improbable, during flight, that could significantly affect the structural c apability of the airp lane and for which

the associated reduction in airworthiness can be minimi zed by suitable flight limitations, must be signa led to the flight cr ew. Failure conditions that result in a factor of safety between th e airplane strength and th e loads of Subpart C below 1.25, or flutter margins belo w V'', must be signaled to the crew during flight. (e) Dispatch with know n failure conditions. If the airplane is to be dispatched in a known system-failure condition that affect s structural performanc e, or affects the reliability of the remaining system to maintain structural perfor mance, then the provisions of Sec. 25.3 02 must be met for the dis patched condition and for subsequent failures. Fl ight limitations and expected op erational limitations may be

taken into account in establ ishing 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. Th ese limitations must be such that the probability of being in this combined failure state, and then subsequently enc ountering limit-load conditions, is extremely im probable. No reduction in these safety margins is

allowed if the subs equent system-failure rate is greater than 10- 3 per hour. Pa g e 8 of 9 Special Conditions: Alenia Aeronautica Model C-27J Airplane; Interaction of

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...Footer Information Issued in Renton, Washingt on, on August 20, 2009. Ali Bahrami, Manager, Transport Airplane Directorate,

Aircraft Certification Service. [FR Doc. E9-20697 Fil ed 8-27-09; 8:45 am]

BILLING CODE 4910-13-P

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