Landing gear malfunction — Fokker 100, Alliance Airlines

Summary

An Alliance Airlines Fokker 100 experienced a left main landing gear extension failure on approach to Darwin Airport. After multiple manual extension attempts, the gear locked down and a normal landing was made. The event triggered a mandatory gear structural inspection; no cracks or damage were found.

Investigation Findings (3)

1. 01Gear extension failure was caused by a failed hydraulic actuator seal in the gear-down sequencing valve.
2. 02Seal age had exceeded the calendar life limit by 9 months; a maintenance scheduling error was identified.
3. 03Alliance Airlines revised its life-limited component tracking system to include an automated calendar limit alert.