Incident Details
The pilot reported that within minutes after takeoff on each of the two flights preceding the accident, he had experienced smoke in the cockpit and promptly landed. The accident occurred during the third attempted flight after the pilot attempted repairs to his airplane. Shortly after takeoff, the pilot observed smoke in the cabin and saw flames near his feet. With diminishing visibility due to smoke filling the cockpit, he returned to the airport and landed. The passenger exited the airplane before it came to a stop, and the pilot followed shortly after. The airplane was consumed by the fire.
Previous Events and Maintenance Attempts
The pilot had investigated the first two smoke events with assistance from personnel at a local fixed base operator and found a loose hose. He purchased a hose attachment clamp from a neighborhood consumer supply store and proceeded with its installation. No maintenance entry was made for the work.
Investigation Findings
The subsequent investigation revealed that the precipitating smoke event was not related to the hose but was due to a burn-through of the airplane's exhaust muffler. FAA inspectors examined the airplane and found that the engine exhaust muffler had burned through at the bottom left end. The hole allowed engine exhaust gases and flames to be directed into the engine compartment and toward the firewall. The exhaust heat also ruptured an aluminum hydraulic brake line mounted on the firewall, which added to the fire.
Maintenance Records
An examination of the airplane's maintenance records revealed that an annual inspection had been performed on July 6, 2007, 2.5 operating hours prior to the accident. The airplane's listed time in service was 3,104.3 hours. The logbook signoff included a statement that the airplane was found to be in an airworthy condition, and Airworthiness Directive (AD) 68-05-01 (exhaust inspection) had been complied with. AD 68-05-01 became effective in 1968 and requires inspections of exhaust mufflers installed in specific models of airplanes, including the accident airplane. The inspection directs that muffler assemblies with over 950 hours in service be examined for signs of cracks, corrosion, burn-throughs, heat damage, collapsed stack, or weld separations.
Service Bulletin
According to Piper Service Letter number 324C, incorporated in the airworthiness directive, an exhaust and heat exchange system that has been permitted to deteriorate due to age, poor inspection, and maintenance can conceivably cause "engine compartment originated fires in flight."