Source: https://www.federalregister.gov/documents/2009/04/08/E9-7882/special-conditions-boeing-model-747-8-8f-airplane-interaction-of-systems-and-structures
Timestamp: 2018-04-20 00:25:26
Document Index: 211408439

Matched Legal Cases: ['§\u200921', 'art 25', 'art 25', '§\u200921', 'art 25', '§\u200925', '§\u200925', '§\u200925', '§\u200925', 'art 25']

Federal Register :: Special Conditions: Boeing Model 747-8/-8F Airplane, Interaction of Systems and Structures
Special Conditions: Boeing Model 747-8/-8F Airplane, Interaction of Systems and Structures
15890-15893 (4 pages)
Docket No. NM400 Special Conditions No. 25-09-03-SC
https://www.federalregister.gov/d/E9-7882 https://www.federalregister.gov/d/E9-7882
Start Preamble Start Printed Page 15890
This notice proposes special conditions for the Boeing Model 747-8/-8F airplane. This airplane will have novel or unusual design features when compared to the state of technology envisioned in the airworthiness standards for transport category airplanes. These design features include their effects on the structural performance. 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. Additional special conditions will be issued for other novel or unusual design features of the Boeing 747-8/-8F airplanes.
Comments on this proposal may be mailed in duplicate to: Federal Aviation Administration, Transport Airplane Directorate, Attention: Rules Docket (ANM-113), Docket No. NM400, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; or delivered in duplicate to the Transport Airplane Directorate at the above address. All comments must be marked Docket No. NM400. Comments may be inspected in the Rules Docket weekdays, except Federal holidays, between 7:30 a.m. and 4 p.m.
Under the provisions of § 21.101, Boeing must show that Models 747-8 and 747-8F (hereafter referred as 747-8/-8F) meet the applicable provisions of part 25, as amended by Amendments 25-1 through 25-117, except for earlier amendments as agreed upon by the FAA. These regulations will be incorporated into Type Certificate No. A20WE after type certification approval of the 747-8/-8F.
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 considering failure conditions. In some cases, Start Printed Page 15891reduced margins are allowed for failure conditions based on system reliability.
As discussed above, this proposed special condition is applicable to Boeing Model 747-8/-8F airplanes. Should Boeing apply at a later date for a change to the type certificate to include another model incorporating the same novel or unusual design features, this proposed special condition would apply to that model as well under the provisions of § 21.101.
The authority citation for this proposed Special Condition is as follows:
Accordingly, pursuant to the authority delegated to me by the Administrator, the Federal Aviation Administration (FAA) proposes the following special condition as part of the type certification basis for the 747-8/-8F airplanes.
The Boeing Model 747-8/8F airplane is equipped with automatic control systems that affect the airplane's 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 Subparts C and D of part 25. 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.
1. The criteria defined here 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 structural elements 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 this proposed special condition.
2. Depending on the specific characteristics of the airplane, additional studies may be required that go beyond the criteria provided in this proposed special condition in order 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.
3. The following definitions are applicable to this proposed special condition.
(b) Flight limitations: Limitations that can be applied to the airplane flight conditions following an in-flight occurrence and that are included in the Airplane Flight Manual (AFM) (e.g., speed limitations, avoidance of severe weather conditions, etc.).
(e) Failure condition: The term failure condition is the same as that used in § 25.1309, however this proposed special condition 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 inputs such as gusts or pilot actions, or lower flutter margins). The system failure condition includes consequential or cascading effects resulting from the first failure.
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(iv) The limit yaw maneuvering conditions specified in § 25.351. The limit ground loading conditions specified in §§ 25.473, 25.491 and 25.493.
(2) For static strength substantiation, each part of the structure must be able to withstand the loads in paragraph (3)(b)(1) of the proposed special condition 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.
(3) For residual strength substantiation, the airplane must be able to withstand two thirds of the ultimate loads defined in paragraph (3)(b)(1) of the proposed special condition. For pressurized cabins, these loads must be combined with the normal operating differential pressure.Start Printed Page 15893
(6) 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).
(a) Consideration of certain failure conditions may be required by other sections 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.
5. 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 this proposed special condition must be met, including the provisions of paragraph 2 for the dispatched condition, and paragraph 3 for subsequent failures. Expected operational limitations may be taken into account in establishing Pj as the probability of failure occurrence for determining the safety margin in Figure 1. 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.
[FR Doc. E9-7882 Filed 4-7-09; 8:45 am]