NTSB Identification: ANC99IA025.
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Nonscheduled 14 CFR operation of EVERGREEN INT'L AIRLINES, INC.
Incident occurred Tuesday, January 19, 1999 in FAIRBANKS, AK
Probable Cause Approval Date: 06/21/2000
Aircraft: Boeing 747-100, registration: N481EV
Injuries: 4 Uninjured.

NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.

After landing, the number four engine thrust reverser remained deployed. A tailpipe fire occurred, with no reported cockpit indications of either the fire or the extended reverser. Ground personnel notified the crew of the fire, and the engine was shut down. A teardown inspection revealed that the thrust reverser pneumatic drive unit (PDU) had been incorrectly assembled at the previous overhaul, 113 hours and 26 cycles prior to failure. The required stroke of the PDU interlock mechanism is 1.318 to 1.326 inches. At disassembly, the stroke was measured to be 1.230 inches. This stroke is required to allow the gear change mechanism to fully shift (from extend, to retract). The PDU retract pawl fracture surfaces were indicative of overstress. The lowest ambient surface temperature the airplane had been exposed to at the various airports during the 26 landing cycles had been -13 degrees Fahrenheit. The surface temperature during the failure of the PDU was -27 degrees Fahrenheit.

The National Transportation Safety Board determines the probable cause(s) of this incident to be:

The improper overhaul of the thrust reverser pneumatic drive unit, and the subsequent failure of the thrust reverser actuator. Factors associated with the incident were the inadequate quality assurance procedures by the overhaul company.

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