Source: https://www.federalregister.gov/documents/2008/11/24/E8-27540/special-conditions-general-electric-company-genx-2b-model-turbofan-engines
Timestamp: 2018-07-21 16:29:12
Document Index: 55599727

Matched Legal Cases: ['§\u200933', '§\u200933', '§\u200933', '§\u200933', '§\u200933', '§\u200933', '§\u200933']

A Proposed Rule by the Federal Aviation Administration on 11/24/2008
We must receive your comments on or before December 24, 2008.
73 FR 70926
70926-70928 (3 pages)
Notice No. 33-08-01-SCI
E8-27540
https://www.federalregister.gov/d/E8-27540 https://www.federalregister.gov/d/E8-27540
You may mail two copies of your comments to: Federal Aviation Administration, Aircraft Certification Service, Engine and Propeller Directorate, Attn: Robert McCabe, ANE-110 Standards Staff, 12 New England Executive Park, Burlington, Massachusetts 01803-5299, Rules Docket No. NE129. You may deliver two copies to the Engine and Propeller Directorate at the above address. You must mark your comments: Docket No. NE 129. You may send comments via e-mail to robert.mccabe@faa.gov. You must use the subject “Docket No. NE 129”. You can inspect comments in the Rules Docket weekdays, except Federal holidays, between 7:30 a.m. and 4 p.m.
Federal Aviation Administration, Aircraft Certification Service, Engine and Propeller Directorate, Attn: Robert McCabe, ANE-1 10 Standards Staff, 12 New England Executive Park, Burlington, Massachusetts 01803-5299; telephone (781) 238-7138; facsimile (781) 238-7199; e-mail robert.mccabe@faa.gov.
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 these special conditions based on the comments we receive.
If you want us to let you know we received your comments on this proposal, send us a preaddressed, stamped postcard on which the docket number appears. We will stamp the date on the postcard and mail it back to you.
On February 28, 2006, the General Electric Company (GE) applied to the FAA to amend the GEnx model type certificate to add GEnx-2B engine model series. Currently, the GEnx type certificate consists of the GEnx-1B turbofan engine models GEnx-1B54, GEnx-1B58, GEnx-1B64, GEnx-B67, and GEnx-1B70. GE is requesting to add the GEnx-2B67 and GEnx-2B69 engine model series to the type certificate.
GE submitted data and analysis during the GE90 baseline and GE90-115B derivative engine model certification programs, and again during the recent GEnx-JB certification program. GE was able to show that the likelihood of these carbon graphite composite fan blades failing below the inner annulus flow path line is highly improbable. GE questioned the appropriateness of the requirement contained in § 33.94(a)(1) to show containment after a failure of the fan blade at the outermost retention feature.
The FAA responded during the GE90 baseline by reviewing the historical basis for the § 33.94(a)(1) test requirements, and determined that they are based on metallic blade characteristics and service history, and therefore were not appropriate for the unusual design features of the composite fan blade design planned for Start Printed Page 70927that engine model. The FAA determined that a more realistic blade retention test for the novel and unusual design characteristics of these carbon fiber composite fan blades would be achieved with a blade failure at the inner annulus flow path line (the complete airfoil only), instead of at the outermost blade retention feature as currently required by § 33.94(a)(1).
The FAA also determined that the composite fan blade design and construction characteristics present factors, other than the expected location of a blade failure, which must be considered. Consequently, the FAA required that tests and analyses must account for the anticipated effects of in-service deterioration and handling damage, manufacturing and materials variations in, and environmental effects on, the composite material. The FAA also required that tests and analyses must show that a lightning strike on a composite fan blade would not result in a hazardous condition to the aircraft, and that the engine would continue to meet the requirements of 33.75.
Therefore, the FAA issued special conditions SC-33-ANIE-08 on February 1, 1995, for the GE90-75B, 76B, and -85B baseline engine models. These special conditions defined additional safety standards for the carbon graphite composite fan blades that were appropriate for the unusual design features of those fan blades, and that were determined to be necessary to establish a level of safety equivalent to that established by the airworthiness standards of § 33.94(a)(1).
The FAA determined that these special conditions were also appropriate for the derivative GE90 77B and -90B engine models, the GE90-94B engine model, and the GE90 -110B1, -113B, and -115B engine models, which were added to the TCDS in July 1996, June 2000, and July 2003, respectively. Engine model series GE90-75B was deleted from the GE90 TCDS in February 1995.
Due to that success, GE now proposes to use a similar approach to demonstrate a level of safety equivalent to that established by the airworthiness standards of § 33.94(a)(1) for the GEnx 2B certification program. In lieu of direct compliance to § 33.94(a)(1) using an engine test, GE notified the FAA that it plans to utilize an analytical method that will be validated by data from the GEnx-1B § 33.94(a)(1) engine test, GEnx-lB fan blade rig tests, GEnx-2B fan blade rig tests, and other engine and component tests as needed.
Accordingly, the FAA proposes the following special conditions as part of the type certification basis for the derivative GEnx-2B series turbofan engines.
(d) Using a procedure approved by the Administrator, establish an operating Start Printed Page 70928limitation that specifies the maximum allowable number of start-stop stress cycles for the fan blade retention system. The life evaluation shall include the combined effects of high cycle and low cycle fatigue. If the operating limitation is less than 100,000 cycles, that limitation must be specified in Chapter 05 of the Engine Manual Airworthiness Limitation Section. The fan blade retention system includes the portion of the fan blade from the inner annulus flow path line inward to the blade dovetail, the blade retention components, and the fan disk and fan blade attachment features.
(f) Substantiate by test or analysis acceptable to the Administrator that not only will the engine continue to meet the requirements of 33.75 following a lightning strike on the composite fan blade structure, but the lightning strike will also not cause damage to the fan blades that would prevent continued safe operation of the affected engine.
Issued in Burlington, Massachusetts on November 12, 2008.
[FR Doc. E8-27540 Filed 11-21-08; 8:45 am]