FAA AD to address loss of engine thrust control resulting in uncommanded high thrust in General Electric Company GE90 Engines !
FAA issues Airworthiness Directive : AD 2021-15-05 on (GE) GE90-110B1 and GE90-115B model turbofan engines.
Subject AD on the above mentioned GE engine models was prompted by an in-service occurrence of loss of engine thrust control , occurred on October 27, 2019 resulting in uncommanded high thrust.
The FAA has issued this AD to prevent failure of the full authority digital engine control (FADEC) integrated circuit (MN4) microprocessor solder ball and the action is expected to be complied at an Engine Overhaul Facility.
FAA says , " The unsafe condition, if not addressed, could result in loss of engine thrust control and reduced control of the airplane ".
► Initial Action Mandated by the AD :
Upon effective, this AD asks operators to replace the FADEC MN4 microprocessor using an approved overhaul procedure:
First Case - For a FADEC MN4 microprocessor with 10,500 or more cycles since new (CSN), replace the FADEC MN4 microprocessor before accumulating 500 additional cycles on the FADEC MN4 microprocessor.
Second case - For a FADEC MN4 microprocessor with 5,000 CSN or more, but fewer than 10,500 CSN, replace the FADEC MN4 microprocessor at the next FADEC component shop visit or before accumulating 11,000 CSN on the FADEC MN4 microprocessor, whichever occurs first.
► Repeated Action Mandated by the AD :
After the initial replacement, FAA asks the operators to repeat the replacement of the FADEC MN4 microprocessor at the first FADEC component shop visit after accumulating 5,000 CSN since the last replacement but before accumulating 11,000 CSN since the last replacement.
The FADEC (Full authority digital engine control).
General Electric has issued an Service Bulletin , GE90-100 Service Bulletin (SB) 73-0118, Revision 01, dated April 27, 2021 to address the issue.
Replacement of the FADEC MN4 microprocessor is to be done using the Accomplishment Instructions, paragraph 3.A., of GE GE90-100 Service Bulletin 73-0118, Revision 01, dated April 27, 2021.
This airworthiness directive (AD) becomes effective on September 13, 2021.
Source - FAA.
Picture for representation only .
