Daily Rules, Proposed Rules, and Notices of the Federal Government
The FAA has determined that notice of, and opportunity for prior public comment on, these special conditions are impracticable because these procedures would significantly delay issuance of the design approval and thus delivery of the affected aircraft. In addition, the substance of these special conditions has been subject to the public comment process in several prior instances with no substantive comments received. The FAA therefore finds that good cause exists for making these special conditions effective upon issuance.
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 will consider all comments we receive by the closing date for comments. We may change these special conditions based on the comments we receive.
On April 8, 2010, Airbus applied for a change to Type Certificate No. A28NM to include modification 160500 on Airbus Model A318, A319, and A320 series airplanes and modification 160023 on Model A321 series airplanes for the installation of a “Sharklet,” a large wingtip device. The Model A318, A319, A320, and A321 series airplanes are short to medium-range, twin turbofan, transport category airplanes with a maximum seating capacity of 136 to 220 passengers, a maximum takeoff weight of 130,071 to 205,027 pounds, and a maximum operating altitude of 39,800 feet.
FAA issued special conditions 25-ANM-23, effective December 15, 1988, originally applicable to Airbus Model A320 series airplanes and later to the Model A318, A319, and A321 series airplanes. Those special conditions included requirements for interactions of systems and structures. Airbus requested, and FAA agrees, that these special conditions be updated for the Airbus Model A318, A319, and A320 series airplanes with modification 160500 and Model A321 series airplanes with modification 160023 (Sharklet) and later derivatives to be consistent with the latest European Aviation Safety Standards (EASA) standards and the latest versions of the FAA special conditions issued on this subject.
Under the provisions of Title 14, Code of Federal Regulation (14 CFR) 21.101, Airbus must show that the Model A318, A319, A320, and A321 series airplanes, as changed, continue to meet the applicable provisions of the regulations incorporated by reference in Type Certificate No. A28NM or the applicable regulations in effect on the date of application for the change. 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 Type Certificate No. A28NM are 14 CFR part 25, as amended by Amendments 25-1 through 25-56, and special conditions 25-ANM-23. In addition, the certification basis includes certain special conditions, exemptions, or later amended sections of the applicable part that are not relevant to these special conditions.
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 Model A318, A319, A320, and A321 series airplanes because of a novel or unusual design feature, special conditions are prescribed under the provisions of § 21.16.
Special conditions are initially applicable to the model for which they are issued. Should the type certificate for that model be amended later to
In addition to the applicable airworthiness regulations and special conditions, the Model A318, A319, A320, and A321 series airplanes 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.
The FAA issues special conditions, as defined in 14 CFR 11.19, in accordance with § 11.38, and they become part of the type-certification basis under § 21.101.
The Airbus Model A318, A319, and A320 series airplanes with modification 160500 and Model A321 series airplanes with modification 160023 (Sharklet) will incorporate the following novel or unusual design features: Systems that, directly or as a result of failure or malfunction, affect structural performance. These systems include flight control systems, autopilots, stability augmentation systems, load alleviation systems, fuel management systems, and other sytems.
These airplanes are equipped with systems that, directly or as a result of failure or malfunction, affect its structural performance. Current regulations do not take into account loads for the aircraft due to the effects of systems on structural performance including normal operation and failure conditions with strength levels related to probability of occurrence. These special conditions define criteria to be used in the assessment of the effects of these systems on structures.
As discussed above, these special conditions are applicable to the Airbus Model A318, A319, A320 series airplanes with modification 160500 and Model A321 series airplanes with modification 160023 (Sharklet). 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 features, the special conditions would apply to that model as well.
This action affects only certain novel or unusual design features on the model series of airplanes listed above. It is not a rule of general applicability.
The substance of these special conditions has been subjected to the notice and comment period in several prior instances and has been derived without substantive change from those previously issued. It is unlikely that prior public comment would result in a significant change from the substance contained herein. Therefore, because a delay would significantly affect the certification of the airplane, which is imminent, the FAA has determined that prior public notice and comment are unnecessary and impracticable, and good cause exists for adopting these special conditions upon issuance. The FAA is requesting comments to allow interested persons to submit views that may not have been submitted in response to the prior opportunities for comment described above.
Aircraft, Aviation safety, Reporting and recordkeeping requirements.
The authority citation for these special conditions is as follows:
49 U.S.C. 106(g), 40113, 44701, 44702, 44704.
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 A318, A319, and A320 series airplanes with modification 160500 and Model A321 with modification 160023 (Sharklet) series airplanes.
For airplanes equipped with systems that affect structural performance, either directly or as a result of a failure or malfunction, the influence of these systems and their failure conditions must be taken into account when showing compliance with the requirements of 14 CFR part 25 subparts C and D. 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, 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.
(a) The criteria defined herein only address 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 whose failure 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.
(b) Depending upon the specific characteristics of the airplane, additional studies may be required that go beyond the criteria provided in these special conditions in order to demonstrate the capability of the airplane in meeting other realistic conditions such as alternative gust or maneuver descriptions for an airplane equipped with a load alleviation system.
(c) The following definitions are applicable to these special conditions:
The following criteria will be used in determining the influence of a system and its failure conditions on the airplane structure.
(1) Limit loads must be derived in all normal operating configurations of the system from all the 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 § 25.629.
(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 (FS) 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 2(b)(1)(i). For pressurized cabins, these loads must be combined with the normal operating differential pressure.
(iii) Freedom from aeroelastic instability must be shown up to the speeds defined in § 25.629(b)(2). For failure conditions that result in speeds beyond V
(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 (or defined by special condition or equivalent level of safety in lieu of the following conditions) at speeds up to V
(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 paragraph 2(b)(2)(i) of the special conditions 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.
(iii) For residual strength substantiation, the airplane must be able to withstand two thirds of the ultimate loads defined in paragraph 2(b)(2)(ii) of the special conditions. For pressurized cabins, these loads must be combined with the normal operating differential pressure.
(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 § 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 sections of 14 CFR part 25 regardless of calculated system reliability. Where analysis shows the probability of these failure conditions to be less than 10
(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 significantly reduce the reliability of the remaining system. As far as reasonably practicable, the flight crew must be made aware of these failures 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 detection and indication systems to achieve the objective of this requirement. These certification maintenance requirements must be limited to components that are not readily detectable by normal detection and indication systems and where service history shows that inspections will 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. For example, 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.