History of Flight
On July 25, 2016, about 0945 eastern daylight time, a Yakovlev Yak-11, registration N5940, was substantially damaged by fire after landing at Allegheny County Airport (AGC) in West Mifflin, Pennsylvania. The commercial pilot was fatally injured. The airplane was privately owned and operated by the pilot under 14 CFR Part 91. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight, which originated at Chester County Airport (MQS) in Coatesville, Pennsylvania, about 0830.
The accident occurred during the first leg of a cross-country flight to the Experimental Aircraft Association fly-in at Wittman Regional Airport in Oshkosh, Wisconsin. According to air traffic control information, the pilot first contacted the tower controller when about 20 miles east of the airport and advised that his transponder was inoperative. The controller instructed the pilot to "proceed straight in" for runway 28 and cleared the airplane for landing.
The pilot acknowledged and advised that he would be going to Corporate Air and would need progressive taxi instructions. Security video showed the airplane touched down about 2,000 ft down the runway. The controller then advised the pilot to "make any left turn" and contact ground control. After rolling past taxiway C, the pilot requested to turn around on the runway. Given permission, he again was instructed to contact ground control. As the airplane turned, the ground controller advised that there was a fire under the wing. The airplane continued turning left, traveled off the paved surface, and rolled through the infield until coming to rest near taxiway G with smoke and flames emanating from the right side.
The pilot egressed and was transported via golf cart to a hangar where paramedics treated him. He was wearing shorts, a T-shirt, socks, and tennis shoes, and had not worn his fire-retardant flight suit, gloves, or helmet. He had visible thermal injuries over 62% of his body. He was transported to a hospital, where he succumbed to his injuries about 6 days later.
Personnel Information
The pilot held a commercial pilot certificate with ratings for airplane single- and multi-engine land and instrument airplane. He had flown the T-34, T2C, TA4J, and S3B while in the U.S. Navy. He owned and operated a Yak 50 and 52 and held a letter of authorization to operate the Yak-3, Yak-9, and Yak-11 as pilot-in-command under VFR. His most recent FAA second-class medical certificate was issued April 5, 2016, on which he reported about 3,100 total hours of flight experience.
Aircraft Information
The accident airplane was a two-seat, low-wing, military trainer with a variable pitch propeller. The main landing gear was retractable, and the tailwheel was fixed. Flight controls were conventional, with elevator and ailerons controlled via push-pull rods and rudder by cable. The tailwheel could be locked with the stick held back.
The airplane was manufactured in 1952 and operated by the Egyptian Air Force through the 1980s. During a 1990 rebuild, the original engine and propeller were replaced with a 1,350-horsepower Pratt & Whitney R1830-75 engine and a Hamilton Standard three-bladed constant speed propeller. The fuel system was modified during the engine replacement, including removal of the primer and wobble pump and installation of an electric fuel pump. On December 5, 1990, the airplane was classified as experimental and issued a special airworthiness certificate in the racing, crew training, and exhibition category. Its most recent condition inspection was completed on August 28, 2015, at 318.5 total hours.
Meteorological Information
The 0953 recorded weather at AGC, about 8 minutes after the accident, included variable winds at 5 knots, 6 miles visibility in haze, clear skies, temperature 28°C, dew point 23°C, and an altimeter setting of 29.99 inches of mercury.
Wreckage and Impact Information
Examination of the runway and accident site revealed that the airplane turned left for about 294° before departing the paved runway. It traveled across a storm drain and the airport infield about 612 ft before coming to rest. The cockpit and surrounding structure were consumed by fire, with extensive thermal damage to the right wing and empennage. The propeller blades showed minimal damage with no evidence of a propeller strike. The main landing gear was down and locked, and brakes showed no signs of overheating. The tailwheel was functional.
Fire damage was concentrated on the aft inboard trailing edge of the right wing and adjacent areas, where the fuel system sump tank was located. The sump tank had multiple areas of melt-through. Separated structure showed broomstrawing consistent with shock loading while near-molten. Flight control continuity was confirmed. The mixture control was full rich, fuel shutoff lever was about 3 inches forward of the aft stop, throttle full aft, and propeller full forward.
Additional Information
According to the previous owner, the belly panel, when removed, exposed the electric boost pump, fuel plumbing, rudder cables, torque tubes, center fuel tank, and items under the pilot compartment. Examination revealed no fire blocking or insulation materials in that area.
Five days before the accident, a mechanic installed a Garmin SL 40 transceiver and Garmin 250xl GPS, and fire-sleeved oil and fuel hoses at the engine accessory case and cockpit gauges.
According to first responders, the pilot stated that he thought "a fuel line came apart," "blew off," or "busted."
Examination of the fuel system showed the fire originated in the right wing root area, where fuel feed, return, and vent lines were located. The electric fuel pump body was intact, but outlets showed thermal deformation. No evidence of pre-impact fuel leaks was found. A section of power wiring near the right wing root showed signs of arcing, beading, melting, and welding of conductors, while other wiring showed only thermal exposure.
Medical and Pathological Information
The autopsy determined the cause of death as superficial and deep burns combined with inhalational thermal injuries complicated by sepsis. Toxicology testing was negative for carbon monoxide, cyanide, and drugs except for post-accident administered medications.
Tests and Research
The fuel system consisted of two main wing tanks of 45.7 gallons each and a sump tank of 3.6 gallons. Fuel flowed from the main tanks to the sump tank, then to the engine-driven pump and carburetor. The previous owner reported a history of fuel leaks from a pump, which was replaced multiple times.