 Although it was down and locked, the rapid and abnormal free fall of the gear damaged a microswitch so severely that it failed to complete the circuit to the cockpit green light that tells the pilots that gear is down and locked.Those unusual indications (loud noise, vibration, yaw, and no green light) led the captain to abort the landing, so that they would have time to diagnose the problem and prepare the passengers for an emergency landing.While the decision to abort the landing was prudent, the accident occurred because the flight crew became so absorbed with diagnosing the problem that they failed to monitor their fuel state and calculate a time when they needed to return to land or risk fuel exhaustion.