Airworthiness Directives; General Electric Company Engines

SUPPLEMENTARY INFORMATION:

Comments Invited

The FAA invites you to send any written relevant data, views, or arguments about this proposal. Send your comments to an address listed under the ADDRESSES section. Include “Docket No. FAA-2024-2417; Project Identifier AD-2024-00336-E” at the beginning of your comments. The most helpful comments reference a specific portion of the proposal, explain the reason for any recommended change, and include supporting data. The FAA will consider all comments received by the closing date and may revise this proposal because of those comments.

Except for Confidential Business Information (CBI) as described in the following paragraph, and other information as described in 14 CFR 11.35, the FAA will post all comments received, without change, to regulations.gov, including any personal information you provide. The agency will also post a report summarizing each substantive verbal contact received about this NPRM.

Confidential Business Information

CBI is commercial or financial information that is both customarily and actually treated as private by its owner. Under the Freedom of Information Act (FOIA) (5 U.S.C. 552), CBI is exempt from public disclosure. If your comments responsive to this NPRM contain commercial or financial information that is customarily treated as private, that you actually treat as private, and that is relevant or responsive to this NPRM, it is important that you clearly designate the submitted comments as CBI. Please mark each page of your submission containing CBI as “PROPIN.” The FAA will treat such marked submissions as confidential under the FOIA, and they will not be placed in the public docket of this NPRM. Submissions containing CBI should be sent to Alexander Thickstun, Aviation Safety Engineer, FAA, 2200 South 216th Street, Des Moines, WA 98198. Any commentary that the FAA receives which is not specifically designated as CBI will be placed in the public docket for this rulemaking.

Background

The FAA issued AD 2020-20-17, Amendment 39-21273 (85 FR 63443, October 8, 2020) (“AD 2020-20-17”) and AD 2021-15-05, Amendment 39-21652 (86 FR 43409, August 9, 2021) (“AD 2021-15-05”), for all GE Model GE90-110B1 and GE90-115B engines.

AD 2020-20-17 was prompted by an in-service occurrence of loss of engine thrust control resulting in uncommanded high thrust. AD 2020-20-17 prohibits dispatch of an airplane if certain status messages are displayed on the EICAS and if certain conditions are present; and as terminating action, requires revision of the existing FAA-approved MEL by incorporating the dispatch restrictions listed in AD 2020-20-17 into the MEL. The agency issued AD 2020-20-17 to prevent dispatch of the airplane when certain faults caused by degradation of the MN4 integrated circuit in the FADEC are displayed and certain FADEC conditions are present which, if not addressed, could result in loss of engine thrust control and reduced control of the airplane.

AD 2021-15-05 was also prompted by the in-service occurrence of loss of engine thrust control resulting in uncommanded high thrust. AD 2021-15-05 requires initial and repetitive replacement of the FADEC MN4 microprocessor. The agency issued AD 2021-15-05 to prevent failure of the FADEC MN4 microprocessor solder ball which, if not addressed, could result in loss of engine thrust control and reduced control of the airplane.

Actions Since AD 2020-20-17 and AD 2021-15-05 Were Issued

Since the FAA issued AD 2020-20-17 and AD 2021-15-05, the manufacturer has developed a software revision for the FADEC. The FAA has determined that the software revision for the FADEC further mitigates the unsafe conditions specified AD 2020-20-17 and AD 2021-15-05, and therefore, must be required for the affected engines.

FAA's Determination

The FAA is issuing this NPRM after determining that the unsafe condition described previously is likely to exist or develop on other products of the same type design.

Material Incorporated by Reference Under 1 CFR Part 51

The FAA reviewed GE GE90-100 Service Bulletin 73-0117 R01, dated August 5, 2020, which the Director of the Federal Register approved for incorporation by reference as of October 23, 2020 (85 FR 63443, October 8, 2020). This material describes procedures for checking for an inbound FADEC EICAS “ENG EEC C1” status message and corresponding conditions.

The FAA also reviewed GE GE90-100 Service Bulletin 73-0118, Revision 01, dated April 27, 2021, which the Director of the Federal Register approved for incorporation by reference as of September 13, 2021 (86 FR 43409, August 9, 2021). This material specifies procedures for replacing the FADEC MN4 microprocessor.

This material is reasonably available because the interested parties have access to it through their normal course of business or by the means identified in the ADDRESSES section.

Proposed AD Requirements in This NPRM

This proposed AD would retain all of the requirements of AD 2020-20-17 and AD 2021-15-05. Furthermore, this proposed AD would require upgrading the EEC FADEC software to an EEC FADEC software version that is eligible for installation as a terminating action for the retained requirements from AD 2020-20-17 and AD 2021-15-05.

Costs of Compliance

The FAA estimates that this AD, if adopted as proposed, would affect 330 engines installed on airplanes of U.S. registry.

The FAA estimates the following costs to comply with this proposed AD: