Accident Details
At 1905 mountain daylight time on June 16, 2021, a Beech U-8F airplane (registration N62069) was substantially damaged in an accident near Goodland, Kansas. The pilot, the sole occupant, sustained minor injuries. The aircraft was operated by Bemidji Aviation Services Inc. under Title 14 Code of Federal Regulations Part 135 as a cargo flight. According to the pilot, while starting the right engine, a loud bang was heard and flames were observed emanating from the right wing. Airport surveillance video captured flames from the right wing for approximately one second. The pilot immediately shut down the right engine using the mixture control and egressed the airplane.
Aircraft Examination
Post-accident examination revealed that the outboard 12 feet of the right wing was heavily damaged. The forward spar was deflected significantly aft, and the leading edge of the right wing was curled aft. The outboard aft fuel bladder for the right wing was removed and found in a degraded condition with indications of fire damage. The bladder, constructed of nitrile butadiene rubber, was brittle in several areas and contained multiple holes. A sample examined using Fourier Transform Infrared spectroscopy indicated degradation due to oxidation, with embrittlement consistent with physical aging of the material.
Additionally, electrical wiring to the navigation light was chafed, with conductor exposed in two locations. The wire bundle from the right wing exhibited several areas of chafed insulation. One chafed area of the wiring for the navigation lights showed evidence of electrical arcing and welding. Electrical damage to the conductor surface indicated that the wire was energized at the time the damage occurred.
Maintenance History
The operator maintained the airplane according to a maintenance manual accepted by the Federal Aviation Administration. The manual required a routine inspection of the entire airplane every 60 flight hours and eight more detailed inspections of specific portions every 480 flight hours. On May 22, 2021, approximately 50 flight hours before the accident, a detailed inspection was performed. This inspection included checks of fuel tanks, vents, and pumps for leaks; fuel caps and O-rings for fit and seal; fuel quantity transmitters for leakage or visible damage; plumbing for chafing, leakage, and proper attachment; and electrical wiring and equipment for security, chafing, and attachment.
Notably, on July 9, 2019, the same airplane was involved in a similar accident attributed by the NTSB to an explosion of the outboard left wing due to electrical arcing and ignition of fuel vapors. Following that incident, the operator implemented additional maintenance protocols to aid in detecting fuel leaks, including topping off the fuel system in conjunction with wing inspection procedures or unscheduled fuel system maintenance.