Accident Briefs, July 2019

BEECH 35A33
Jacksonville, Alabama/Injuries: 1 Fatal, 1 Serious

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 Page 2 of 10 ERA18FA146 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.

Probable cause(s): The pilot/mechanic's inadequate inspection of the exhaust system, including the left muffler and heat exchanger, which precluded his detection of preexisting cracks and led to a missed opportunity to replace the components. The inadequate inspection allowed the cracks to develop to failure, leading to exhaust gasses escaping onto adjacent fuel lines, resulting in the subsequent fuel-fed in-flight fire.

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VANS RV4
Butler, Pennsylvania/ Injuries: 1 Minor

Shortly after takeoff on an extended crosswind leg about 800 ft mean sea level, the engine lost total power. The private pilot continued ahead and landed the airplane in a field. During the landing, the airplane impacted a wire fence and brush, which resulted in substantial damage to the fuselage and wings.

During postaccident interviews, the pilot reported that this was the first flight after he had made maintenance repairs to the automobile-converted engine due to engine failure 1 month before the accident. He stated that he installed an aftermarket engine control unit and modified the fuel delivery software, which resulted in the engine running too lean for flight and likely caused detonation and piston damage to occur. During the run-up before the accident flight, the pilot was aware that the engine was not producing power as it should. However, he decided to depart with a known engine problem, and his decision to do so led to the accident.

Probable cause(s): The pilot's improper decision to fly the airplane with a known engine problem and his improper modification of the engine control unit fuel delivery software, which led to the engine running too lean and resulted in a total loss of engine power during the climb.