NTSB investigators used data provided by various sources and may not have traveled in support of this investigation to prepare this aircraft incident report.
According to the pilot, the freighter flight was normal in all aspects until the landing gear were extended for landing at destination. The left main landing gear, (LMLG) indicated "unsafe", and all attempts, using the emergency/abnormal checklists and telephone/radio-relayed communications with company maintenance, failed to extend it. An emergency, LMLG retracted landing was performed with minimal damage to the aircraft. Postcrash investigation revealed that company maintenance installed a one-way check valve in the LMLG extend hydraulic lines instead of a restricted flow valve. The wrongly installed valve had no factory specification or part number attached, and the tag reportedly removed from it at installation possessed the wrong factory specification number, and the correct vendor' s part number. The company maintenance manual states that upon completion of the valve installation, a leak and operational test of the MLG retract/extension system be performed. The valve installation mechanic and the company inspector both stated that the finished job was leak and "ops" tested.