EASA AD US-2020-20-17
SUPERSEDED BY FAA AD 2025-07-10
Summary
FAA Airworthiness Directive 2020-20-17 is a final rule affecting all General Electric Company GE90-110B1 and GE90-115B turbofan engines installed on Boeing 777 aircraft. This directive addresses an unsafe condition caused by potential failure of the MN4 integrated circuit in the FADEC, which can lead to loss of engine thrust control and uncommanded high thrust. The AD requires operators to prohibit dispatch if certain engine status messages appear and mandates revisions to the minimum equipment list (MEL) to include these dispatch restrictions.
What Changed
This new airworthiness directive introduces mandatory operational restrictions prohibiting dispatch of airplanes displaying specific FADEC EICAS status messages indicating potential engine control failure. It requires operators to revise their FAA-approved MEL within 120 days to incorporate these dispatch restrictions. The AD is issued as an interim action pending further manufacturer review.
Why It Matters
This AD is critical for aviation professionals because it addresses a serious safety risk involving uncommanded high thrust due to FADEC failure, which can compromise flight safety. Operators and maintenance teams must ensure compliance to prevent dispatch of affected aircraft under unsafe conditions. Compliance helps maintain safe engine operation and reduces the risk of in-flight thrust control loss.
What To Do
Operators must immediately prohibit dispatch of airplanes if the specified FADEC EICAS status messages are displayed and conditions per the manufacturer's service bulletin are met. Within 120 days of the AD's effective date, operators must revise their FAA-approved MEL to include the new dispatch restrictions. Additionally, operators should monitor for updates as the FAA considers further rulemaking.
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