BEECH 35A33 — Jacksonville, AL

What happened

The airline transport pilot and his daughter were on the return leg of a cross-country flight in night, visual meteorological conditions. While in cruise flight, the pilot saw smoke in the cockpit, so he began turning off electrical components. The engine then sputtered and lost total power. He set up for a forced landing, felt heat from the engine compartment, and then saw flames coming from the same area. He discharged a portable fire extinguisher. At the first indication of heat, his daughter left the right cockpit seat and climbed into the aft cabin; the pilot did not believe she fastened her lap belt. While crossing a ridge, the airplane collided with trees and came to rest on the side of a hill in a forested area. The pilot egressed the airplane and noted that his daughter was no longer in the airplane. He subsequently found her; she had been thrown clear of the wreckage and was seriously injured. First responders arrived soon thereafter, and she later died from her injuries.

Most of the airplane's fuselage, empennage, and right wing was consumed by postcrash fire. The left wing separated during the impact sequence and was not burned. The engine, propeller, nose landing gear, and cowling separated during the impact sequence and were found outside the postcrash fire zone. Evidence of an in-flight fire was observed at the aft section of the engine, with the heaviest fire damage near fuel lines adjacent to the left muffler and heat exchanger. An examination of the muffler and heat exchanger revealed multiple preexisting cracks that could have allowed hot exhaust gasses to escape from the assembly onto the adjacent fuel lines. Damage to those fuel lines prevented determining a definitive origin for the ignition of the inflight fire, though the damage to those fuel lines was consistent with the fire being fuel-fed in nature. The largest crack of the muffler was located at the left side and extended 3.35 inches around the circumference through the muffler wall and coincided with a crack through the heat exchanger end flange that extended 4.25 inches around the circumference. Oxidation and exhaust deposits observed on the crack surfaces indicated the cracks developed and existed for some time before the accident.

The pilot, who owned the airplane, was a certificated airframe and powerplant mechanic with inspection authorization. He performed the airplane's most recent annual and 100-hour inspections about 4 months before the accident. The airplane maintenance manual recommended that, during 100-hour inspections, the exhaust system should be checked for, in part, deformation and cracks and for thin wall condition, which may occur due to normal internal erosion on stacks that have long service time. About 2 months before the accident, the pilot replaced the left exhaust stack; however, he did not replace the associated muffler and heat exchanger.

The cracking observed on the muffler and heat exchanger displayed signatures consistent with them having developed over time, so the pilot should have been able to detect them by thoroughly inspecting the exhaust system, including the left muffler and heat exchanger, during the most recent 100-hour inspection as recommended, or when he removed and replaced the exhaust stack. Due to his inadequate inspection of the exhaust system, he failed to note the cracks and corrosion and missed an opportunity to replace the muffler and heat exchanger. This allowed the cracks to develop to failure, leading to hot gasses escaping on to the adjacent fuel lines, and ultimately resulting in the subsequent in-flight fire.

An editorial "what led to it / how to avoid it" analysis for this accident is generated separately and will appear here.