Source: https://www.federalregister.gov/documents/2006/10/31/06-8974/special-conditions-boeing-model-737-900er-series-airplanes-interaction-of-systems-and-structures
Timestamp: 2018-03-23 06:01:40
Document Index: 618041331

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

Federal Register :: Special Conditions: Boeing Model 737-900ER Series Airplanes; Interaction of Systems and Structures
Special Conditions: Boeing Model 737-900ER Series Airplanes; Interaction of Systems and Structures
We must receive your comments by November 20, 2006.
63718-63722 (5 pages)
Docket No. NM357
Notice No. 25-06-11-SC
https://www.federalregister.gov/d/06-8974 https://www.federalregister.gov/d/06-8974
This action proposes a special condition for the Boeing Model 737-900ER airplane. This airplane will have a novel or unusual design feature(s) when compared to the state of technology envisioned in the airworthiness standards for transport category airplanes. These design features include interaction of systems and structures. The applicable airworthiness regulations do not contain adequate or appropriate safety standards for this design feature. The proposed special condition 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.
You must mail two copies of your comments to: Federal Aviation Administration, Transport Airplane Directorate, Attn: Rules Docket (ANM-113), Docket No. NM357, 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. NM357. You can inspect comments in the Rules Docket weekdays, except Federal holidays, between 7:30 a.m. and 4 p.m.
Todd Martin, Aerospace Engineer, Airframe/Cabin Safety Branch, ANM-115, Transport Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue, SW., Renton, Washington 98057-3356; telephone (425) 227-1178; facsimile (425) 227-1323; electronic mail Todd.Martin@faa.gov.
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 condition, explain the reason for any recommended change, and include supporting data. We ask that you send us two copies of written comments.
We will file in the docket all comments we receive, as well as a report summarizing each substantive public contact with FAA personnel concerning this special condition. You can inspect the docket before and after the comment closing date. If you wish to review the docket in person, go to the address in the ADDRESSES section of this preamble between 7:30 a.m. and 4 p.m., Monday through Friday, except Federal holidays.
We will consider all comments we receive on or before the closing date for comments. We will consider comments filed late if it is possible to do so without incurring expense or delay. We may change this special condition based on the comments we receive.
On June 5, 2002, The Boeing Company, P.O. Box 3707, Seattle, Washington 98124, applied for an amendment to Type Certificate No. A16WE to include the new Model 737-900ER. The Model 737-900ER, which is a derivative of the Model 737-900 currently approved under A16WE, is a large transport airplane with two flight crew and the capacity to carry 215 passengers. The airplane is powered by two CFM 56-7B or CFM-567B/2 series turbofan engines.
Under the provisions of § 21.101, Boeing must show that the Model 737-900ER meets the applicable provisions of 14 CFR part 25, as amended by Amendments 25-1 through 25-108, except for earlier amendments as agreed upon by the FAA. These regulations will be incorporated into the Type Certificate No. A16WE after type certification approval of the 737-900ER.
In addition, the certification basis includes other regulations, special conditions and exemptions that are not relevant to this proposed special condition. Refer to Type Certificate No. A16WE for a complete description of the certification basis for this model airplane.
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 737-900ER because of a novel or unusual design feature, special conditions are prescribed under the provisions of § 21.16.
In addition to the applicable airworthiness regulations and special conditions, the Model 737-900ER 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.
Model 737-900ER airplane will incorporate novel or unusual design features. This proposed special condition addresses equipment which may affect the airplane's structural performance, either directly or as a result of failure or malfunction.
This proposed special condition is identical or nearly identical to those previously required for type certification of other Boeing airplane models. The proposed 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 (now replaced by the European Aviation Safety Agency), and industry.
In addition to the requirements of part 25, subparts C and D, the following special condition applies.
The Boeing Model 737-900ER is equipped with systems that may affect the airplane's structural performance either directly or as a result of failure or malfunction. The effects of these systems on structural performance must be considered in the certification analysis. This analysis must include consideration of normal operation and of failure conditions with required Start Printed Page 63719structural strength levels related to the probability of occurrence.
As discussed above, this special condition is applicable to the Boeing Model 737-900ER. 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 feature, this special condition would apply to that model as well.
Certification of the Model 737-900ER is currently scheduled for February 2007. Because a delay would significantly affect the applicant's installation of the systems and certification of the airplane we are shortening the public comment period to 20 days.
Accordingly, the Federal Aviation Administration (FAA) proposes the following special condition as part of the type certification basis for Boeing Model 737-900ER airplanes.
In addition to the requirements of part 25, subparts C and D, the following proposed special condition would apply:
a. 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 part 25, subparts C and D. Paragraph b, below, must be used to evaluate the structural performance of airplanes equipped with these systems.
b. Interaction of Systems and Structures.
(1) General: The following criteria must be used for showing compliance with this special condition for interaction of systems and structures and with § 25.629 for airplanes equipped with flight control systems, autopilots, stability augmentation systems, load alleviation systems, flutter control systems, and fuel management systems.
Failure condition: The term failure condition is the same as that used in § 25.1309. However, this special condition applies only to system failure conditions that affect the structural performance of the airplane (e.g., system failure conditions that include loads, change the response of the airplane to inputs as gusts or pilot actions, or lower flutter margins).
(1) Limit loads must be derived in all normal operating configurations of system from all the limit conditions specified in subpart C ( or used in lieu of those specified in subpart C), taking into account any special behavior of such a system or associated functions or any effect on the structural performance of the airplane that may occur up to the limit loads. In particular, any significant non-linearity (rate of displacement of control surface, thresholds or any other system non-linearities) must be accounted for in a realistic or conservative way when deriving limit loads from limit conditions.
(i) For static strength substantiation, those 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 residential strength substantiation, the airplane must be able to withstand two thirds of the ultimate loads defined in paragraph (c)(1)(i) of this section. 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 speed increases beyond Vc/Mc, freedom from aeroelastic instability must be shown to those increased speeds, so that the margins intended by § 25.629(b)(2) are maintained.
(vi) 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.
(C) The limit rolling conditions specified in § 25.349 and limit unsymmetrical conditions specified in §§ 25.367 and 25.427(b) and (c).
Qj = (Tj) (Pj) where:
(iii) For residual strength substantiation, the airplane must be able to withstand two thirds of the ultimate loads defined in paragraph (c)(2)(ii). For pressurized cabins, these loads must be defined combined with the normal operating differential pressure.
Start Printed Page 63722
V′= Clearance speed as defined by § 25.629(b)(2).
V″= Clearance speed as defined by § 25.629(b)(1).
Qj= (Tj)(Pj) where:
Tj= Average time spent in failure condition j (in hours)
Pj= Probability of occurrence of failure mode j (per hour)
(1) The system must be checked for failure conditions, not extremely improbably, 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 flightcrew 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 warning systems to achieve the objective of this requirement. These certification maintenance requirements must be limited to components the failures of which are not readily detectable by normal warning systems and where service history shows that inspections will provide an adequate level of safety.
(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 this Special Condition must be met, including the provisions of paragraph (b), for the dispatched condition and paragraph (c) for subsequent failures. Expected operational limitations may be taken into account in establishing P)j 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 1E-3 per flight hour.
Issued in Renton, Washington, on October 19, 2006.
[FR Doc. 06-8974 Filed 10-30-06; 8:45 am]