Fire in a Boeing 777’s wheel well has prompted the Federal Aviation Administration to propose a rule requiring airlines replace pumps in the jets’ main landing gears.
In a proposed order released on 14 November, the FAA says the fire ignited after one of the pumps – called an “alternating current motor pump” (ACMP) – overheated.
“Investigation found that a lock washer and nut was missing from a moving contact in the related electrical load control unit,” the proposed rule says. “The missing lock washer and nut left the main contact operator bar unrestrained and in a position which let two-phase power go to the ACMP.”
As a result, the pump overheated and leaked hydraulic fluid, which started the fire.
Boeing on 11 September issued a service bulletin addressing the issue. That document called on operators to check records or complete inspections to determine if aircraft have ACMPs with a specific part number, and to replace those pumps with a new pump.
“The design of the ACMP has been modified to include fusible links as a new feature to prevent the ACMP [from overheating] if one of the electrical phases fails,” the FAA says.
The proposed rule would require airlines complete procedures specified in Boeing’s service bulletin. It would apply to the entire US-registered 777 fleet of 340 jets, including all 777 variants.
The FAA is accepting comments about its proposed rule.
