EASA AD US-2021-15-05: Superseded by FAA AD 2025-07-10

What to do

Operators must replace the FADEC MN4 microprocessor within specified cycle limits: before 500 additional cycles if the microprocessor has 10,500 or more cycles since new, or at the next FADEC shop visit if between 5,000 and 10,500 cycles, but before reaching 11,000 cycles. Replacements must then be repeated every 5,000 cycles thereafter using approved overhaul procedures. The directive is effective September 13, 2021, and compliance must follow the stated cycle thresholds.

Summary

FAA Airworthiness Directive 2021-15-05 is a final rule addressing all General Electric Company GE90-110B1 and GE90-115B turbofan engines. It mandates the replacement of the full authority digital engine control (FADEC) MN4 microprocessor due to an unsafe condition involving loss of engine thrust control that can cause uncommanded high thrust. This directive aims to enhance engine safety and prevent potential loss of airplane control.

What changed

This new airworthiness directive introduces mandatory initial and repetitive replacements of the FADEC MN4 microprocessor on affected GE90-110B1 and GE90-115B engines. It removes a previously proposed installation prohibition related to the number of microprocessor replacements. The directive does not include the pending FADEC software upgrade as a terminating action since it is not yet FAA approved.

Why it matters

This directive is critical for aviation professionals as it addresses a serious safety risk of uncommanded high engine thrust caused by microprocessor solder joint failures. Operators and maintenance organizations must comply to ensure continued airworthiness and prevent potential in-flight thrust control loss. Compliance helps maintain regulatory adherence and reduces the risk of costly incidents or accidents.

What to do

Summary

What changed

Why it matters

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