Introduction
An instructional flight, which was the second leg of a cross-country training exercise, ended in a crash. The aircraft had taken off shortly before the incident and was under the guidance of a flight instructor and student pilot.
Flight and Incident
Approximately 50 minutes after takeoff, the aircraft crashed. Prior to the accident, the pilots had been informed by an FAA Flight Service Station (FSS) of a flight precaution for moderate to occasionally severe turbulence from the surface to 14,000 feet. There was evidence indicating that the airplane entered an uncontrolled descent before impact.
Witness Accounts
A witness located approximately one mile from the accident site reported seeing the aircraft flying just above the treetops just before impact. Other witnesses near the crash site reported observing white smoke and an orange flame emanating from the airplane prior to its collision with the ground.
Wreckage Examination
Examination of the wreckage revealed that incorrect exhaust system clamps had been used to attach the muffler to the right-side exhaust stacks (cylinders #1 and #3). The clamps were identified as automotive types, not intended for aviation use. Evidence showed that an exhaust stack had separated from the muffler, allowing exhaust gases to enter the area around the carburetor fuel supply line. Additionally, there was clear evidence of an in-flight fire that had burned through the lower left portion of the engine cowling. An adjacent hole had also been burned through the engine firewall, extending into the cabin area.
Findings
The investigation did not state a probable cause for the accident. The documented findings include the incorrect type of exhaust clamps, evidence of an exhaust leak, and signs of an in-flight fire.