Source: https://www.federalregister.gov/documents/2009/01/26/E9-1327/special-conditions-model-c-27j-airplane-interaction-of-systems-and-structures
Timestamp: 2017-08-24 06:42:00
Document Index: 753632957

Matched Legal Cases: ['art 25', 'art 34', 'art 36', '§\u2009611', '§\u200911', '§\u200921', '§\u200921', 'art 25', 'art 25', 'art 25', '§\u200925', '§\u200925', '§\u200925', '§\u200925', '§\u200925', '§\u200925', '§\u200925', '§\u200925', '§\u200925', '§\u200925', '§\u200925', '§\u200925', '§\u200925', '§\u200925', '§\u200925', 'art 25', 'art 25', '§\u200925']

Federal Register :: Special Conditions: Model C-27J Airplane; Interaction of Systems and Structures
Special Conditions: Model C-27J Airplane; Interaction of Systems and Structures
A Proposed Rule by the Federal Aviation Administration on 01/26/2009
We must receive your comments by February 25, 2009.
74 FR 4353
4353-4357 (5 pages)
Docket No. NM398
Notice No. 25-09-01-SC
E9-1327
https://www.federalregister.gov/d/E9-1327 https://www.federalregister.gov/d/E9-1327
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.
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.
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.
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.
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. TheC-27J is a twin-turbopropeller, cargo-transport aircraft with a maximum takeoff weight of 30,500 kilograms.
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. Start Printed 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 § 611 of Public Law 92-574, the “Noise Control Act of 1972.”
The FAA issues special conditions, under §§ 11.19 and 11.38, and they become part of the type-certification basis under § 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 § 21.101.
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.
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.
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.
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.
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.
(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.
Capability of the airplane to meet the structural requirements of 14 CFR part 25.
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.).
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 § 25.1309.
The term “failure condition” here is the same as that used in § 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). Start Printed Page 4355
(a) General. The following criteria determine the influence of a system and its failure conditions on the airplane structure.
(3) The airplane must meet the aeroelastic-stability requirements of § 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.
(ii) For residual-strength substantiation, the airplane must be able to withstand two-thirds of the ultimate loads defined in subparagraph (c)(1)(i).
(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 § 25.331 and in § 25.345.
(B) The limit-gust-and-turbulence conditions specified in § 25.341 and in § 25.345.
(C) The limit-rolling conditions specified in § 25.349, and the limit-unsymmetrical conditions specified in § 25.367 and § 25.427(b) and (c).
(D) The limit-yaw-maneuvering conditions specified in § 25.351.
(E) The limit-ground-loading conditions specified in § 25.473 and § 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.
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).
(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 § 25.629(b).
(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 § 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, Start Printed Page 4357or 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 § 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.
[FR Doc. E9-1327 Filed 1-23-09; 8:45 am]