Introduction
On August 2, 1983, a student pilot departed Marathon Airport, Florida, at approximately 1105 Eastern Daylight Time on the second leg of a cross-country flight. About ten minutes after takeoff, the pilot detected an unusual smell and turned to find the cabin on fire. The pilot then returned to the airport.
Forced Landing
At around 1130, witnesses observed the aircraft approaching the airport with flames and smoke visible both inside and outside. The pilot conducted a forced landing, but the aircraft touched down just short of the runway. During the landing, the landing gear collapsed.
Investigation
A review of the aircraft's maintenance log showed that the alternator had been replaced earlier that same day, on August 2, 1983. However, after the accident, testing of the alternator indicated it was performing within its normal parameters. The NTSB laboratory examined the fuel lines in the cabin, the fuel selector, and the remaining direct current electrical harnesses. The laboratory found evidence that an aluminum cable had been internally heated, most likely due to excessive electrical current. The fire destroyed other cockpit evidence. Based on statements, the fire originated in the rear of the aircraft.