Federal Aviation Administration (FAA), DOT.
Final special conditions.
These special conditions are issued for Airbus Model A340-500 and -600 airplanes. These airplanes will have a novel or unusual design feature when compared to the state of technology envisioned in the airworthiness standards for transport category airplanes, associated with engine size and torque load, which affects sudden engine stoppage. 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.
April 17, 2002.Start Further Info
FOR FURTHER INFORMATION CONTACT:
Tim Backman, FAA, ANM-116, Transport Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue SW., Renton, Washington, 98055-4056; telephone (425) 227-2797; facsimile (425) 227-1149.End Further Info End Preamble Start Supplemental Information
On November 14, 1996, Airbus applied for an amendment to U.S. type certificate (TC) A43NM to include the new Models A340-500 and -600. These models are derivatives of the A340-300 airplane, which is approved under the same TC.
The Model A340-500 fuselage is a 6-frame stretch of the Model A340-300 and is powered by 4 Rolls Royce Trent 553 engines, each rated at 53,000 pounds of thrust. The airplane has interior seating arrangements for up to 375 passengers, with a maximum takeoff weight (MTOW) of 820,000 pounds. The Model 340-500 is intended for long-range operations and has additional fuel capacity over that of the model A340-600.
The Model A340-600 fuselage is a 20-frame stretch of the Model A340-300 and is powered by 4 Rolls Royce Trent 556 engines, each rated at 56,000 pounds of thrust. The airplane has interior seating arrangements for up to 440 passengers, with a MTOW of 804,500 pounds.
Type Certification Basis
Under the provisions of 14 CFR 21.101, Airbus must show that the Model A340-500 and -600 airplanes meet the applicable provisions of the regulations incorporated by reference in TC A43NM or the applicable regulations in effect on the date of application for the change to the type certificate. The regulations incorporated by reference in the type certificate are commonly referred to as the “original type certification basis.” The regulations incorporated by reference in TC A43NM are 14 CFR part 25 effective February 1, 1965, including Amendments 25-1 through 25-63 and Amendments 25-64, 25-65, 25-66, and 25-77, with certain exceptions that are not relevant to these special conditions.
In addition, if the regulations incorporated by reference do not provide adequate standards with respect to the change, the applicant must comply with certain regulations in effect on the date of application for the change. The FAA has determined that the Model A340-500 and -600 airplanes must be shown to comply with 14 CFR 25-1 through 25-91, with certain FAA-allowed reversions for specific part 25 regulations to the part 25 amendment levels of the original type certification basis.
Airbus has also chosen to comply with part 25 as amended by Amendments 25-92, -93, -94, -95, -97, -98, and -104.
If the Administrator finds that the applicable airworthiness regulations (i.e., 14 CFR part 25) do not contain adequate or appropriate safety standards for the Airbus Model A340-500 and -600 because of a novel or unusual design feature, special conditions are prescribed under the provisions of 14 CFR 21.16.
In addition to the applicable airworthiness regulations and special conditions, the Airbus Model A340-500 and -600 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.
Special conditions are initially applicable to the model for which they are issued. Should the type certificate Start Printed Page 20625for that model be amended later to include any other model that incorporates the same novel or unusual design feature, or should any other model already included on the same type certificate be modified to incorporate the same novel or unusual design feature, the special conditions would also apply to the other model under the provisions of 14 CFR 21.101(a)(1).
Novel or Unusual Design Features
The Airbus Model A340-500 and A340-600 airplanes will incorporate novel or unusual design features involving engine size and torque load that affect sudden engine stoppage conditions. Airbus proposes to treat the sudden engine stoppage condition resulting from structural failure as an ultimate load condition. Section 25.361(b)(1) of part 25 specifically defines the seizure torque load resulting from structural failure as a limit load condition.
The limit engine torque load imposed by sudden engine stoppage due to malfunction or structural failure (such as compressor jamming) has been a specific requirement for transport category airplanes since 1957. The size, configuration, and failure modes of jet engines have changed considerably from those envisioned when the engine seizure requirement of § 25.361(b) was first adopted. Current engines are much larger and are now designed with large bypass fans capable of producing much larger torque loads if they become jammed. It is evident from service history that the frequency of occurrence of the most severe sudden engine stoppage events are rare.
Relative to the engine configurations that existed when the rule was developed in 1957, the present generation of engines are sufficiently different and novel to justify issuance of special conditions to establish appropriate design standards. The latest generation of jet engines are capable of producing, during failure, transient loads that are significantly higher and more complex than the generation of engines that were present when the existing standard was developed. Therefore, the FAA has determined that special conditions are needed for the Model A340-500 and -600 airplanes.
In order to maintain the level of safety envisioned in § 25.361(b), a more comprehensive criteria is needed for the new generation of high bypass engines. These special conditions would distinguish between the more common seizure events and those rarer seizure events resulting from structural failures. For those rarer but severe seizure events, these criteria could allow some deformation in the engine supporting structure (ultimate load design) in order to absorb the higher energy associated with the high bypass engines, while at the same time protecting the adjacent primary structure in the wing and fuselage by providing a higher safety factor. The criteria for the more severe events would no longer be a pure static torque load condition, but would account for the full spectrum of transient dynamic loads developed from the engine failure condition.
Publication of Notice of Proposed Special Conditions
Notice of proposed special conditions No. NM-02-04-SC for Airbus Model A340-500 and -600 airplanes was published in the Federal Register on February 25, 2002 (67 FR 8487). No comments were received, and the special conditions are adopted as proposed.
These special conditions are applicable to the Airbus Model A340-500 and -600 airplanes. Should Airbus apply at a later date for a change to the type certificate to include another model incorporating the same novel or unusual design feature, the special conditions would apply to that model as well under the provisions of § 21.101(a)(1).
This action affects certain novel or unusual design features on the Model A340-500 and A340-600 airplanes. It is not a rule of general applicability, and it affects only the applicant who applied to the FAA for approval of these features on the airplane.Start List of Subjects
List of Subjects in 14 CFR Part 25
- Aviation safety
- Reporting and recordkeeping requirements
The authority citation for these special conditions is as follows:
The Special Conditions
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 Airbus Model A340-500 and -600 airplanes.
The following special conditions are issued in lieu of compliance with 14 CFR 25.361(b) and in lieu of the previously issued special conditions, “Limit Engine Torque,” recorded as item 9 of Special Conditions No. 25-ANM-69 (Docket No. NM-75), Airbus Model A340 Series Airplanes.
1. Sudden Engine Stoppage.
(a) For turbine engine installations, the engine mounts, pylons and adjacent supporting airframe structure must be designed to withstand 1g level flight loads acting simultaneously with the maximum limit torque loads imposed by each of the following:
(1) Sudden engine deceleration due to a malfunction which could result in a temporary loss of power or thrust.
(2) The maximum acceleration of the engine.
(b) For auxiliary power unit installations, the power unit mounts and adjacent supporting airframe structure must be designed to withstand 1g level flight loads acting simultaneously with the maximum limit torque loads imposed by each of the following:
(1) Sudden auxiliary power unit deceleration due to malfunction or structural failure.
(2) The maximum acceleration of the auxiliary power unit.
(c) For engine supporting structure, an ultimate loading condition must be considered that combines 1g flight loads with the transient dynamic loads resulting from each of the following:
(1) The loss of any fan, compressor, or turbine blade.
(2) Where applicable to a specific engine design, and separately from the conditions specified in paragraph 1(c)(1), any other engine structural failure that results in higher loads.
(d) The ultimate loads developed from the conditions specified in paragraphs 1(c)(1) and 1(c)(2) above are to be multiplied by a factor of 1.0 when applied to engine mounts and pylons and multiplied by a factor of 1.25 when applied to adjacent supporting airframe structure.Start Signature
Issued in Renton, Washington, on April 17, 2002.
Acting Manager, Transport Airplane Directorate, Aircraft Certification Service.
[FR Doc. 02-10235 Filed 4-25-02; 8:45 am]
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