What happened
The aircraft was landed with the landing gear up. During the approach, the crew lowered the gear for landing. The nose gear and right main gear were confirmed down. However, the captain stated that his visual inspection from the cockpit revealed that the left main gear did not extend. There is no indication that a fly-by for a tower check was done or that the MIG light in the wheel well was used for better night vision. The crew said the aircraft manual was used for additional procedures to lower the gear. When the fuel remaining reached 100 lbs per side, a decision was made to land with the gear up.
The investigation
Post accident tests of the landing gear extension system showed that all operations were normal except for the main gear down-lock indications. Post accident inspection revealed the left main gear lock piston was binding thus preventing a down and locked indication in the cockpit.