CEN19LA215

The pilot had topped off the outboard fuel tanks before departure. While taxiing for takeoff, the stall warning horn activated, and the pilot pulled the circuit breaker to disable the horn. During the takeoff roll, the pilot heard a loud bang, observed significant damage to the outboard left wing, and aborted the takeoff. While taxiing back to the ramp, the pilot noted smoke coming from the top of the left wing. The pilot taxied the airplane to the corner of the ramp, performed an abbreviated shutdown, grabbed a fire extinguisher, and evacuated. The pilot did not observe any additional smoke or fire and did not discharge the fire extinguisher. Examination of the airplane revealed fire and thermal damage near the wing root area, including melted and burned wiring. Due to some loose installation screws, a fuel leak was found coming from the fuel sending unit, which had recently been replaced. In addition, a wiring harness was found pinched between a metal clamp and a wing rib. Metal-to-metal contact was noted between exposed wiring and the wing rib. Based on the fuel leak in the left wing and the pinched wiring, it is likely fuel vapors ignited and caused an explosion of the outboard left wing. A few months before the accident, the outboard left wing was replaced. The operator's director of maintenance stated that the electrical wiring in the wing was not inspected during the wing replacement.

On July 9, 2019, about 0813 mountain daylight time, a Beech 65 airplane, N62069, experienced a left wing explosion during takeoff roll from the Sidney Municipal Airport (SNY), Sidney, Nebraska. The airline transport pilot was not injured, and the airplane sustained substantial damage to the left wing. The airplane was registered to and operated by Bemidji Aviation Services, Inc., as a Title 14 Code of Federal Regulations Part 91 positioning flight. Day instrument meteorological conditions prevailed at the time of the accident, and an instrument flight rules flight plan was filed. The flight was originating from SNY, and destined for Denver, Colorado. According to the operator, the pilot had topped off the outboard fuel tanks prior to departure, and the airplane contained about 230 gallons. While taxiing and advancing the engine throttles, the stall warning horn sounded so he pulled the circuit breaker as a corrective action which stopped the stall warning horn. The pilot thought the stall warning horn was in error and no further action was taken before the takeoff. During the takeoff roll, the pilot heard a loud bang and observed significant damage to the outboard left wing. Initially he thought maybe the airplane struck an animal, or the airplane impacted a pothole on the runway. While taxiing back to the ramp, the pilot noted a small amount of smoke coming from the top of the left wing. The pilot taxied the airplane to the corner of the ramp, performed an abbreviated shutdown of the airplane, grabbed a fire extinguisher, and evacuated. The pilot did not observe any additional smoke or fire and did not discharge the fire extinguisher. Postaccident examination of the airplane by a Federal Aviation Administration inspector and personnel from the operator revealed fire and thermal damage near the wing root area to include melted and burned wiring. After the accident as a precaution, the airplane was defueled by the operator, and in order to determine if a fuel leak was present, fuel was added to the outboard left wing during the examination. After fueling with 15 to 25 gallons of fuel, fuel began leaking from the top of the left wing fuel sending unit. Safety wire on the fuel sending unit screws was removed, and the fuel sending unit screws were found loose. The screws were tightened and fuel stop leaking from the sending unit. A hole was cut in the wing skin to examine the melted and burned wiring. A wiring harness was found pinched between a metal clamp and a wing rib. The clamp was removed and metal to metal contact was noted between exposed wiring and the wing rib. Due to the thermal damage, the wiring harness could not be separated to determine if the stall warning system could be functionally tested. On February 22, 2019, the airplane was involved in an accident that required the replacement of the outboard left wing. According to the operator's director of maintenance, the electrical wiring in the wing was not inspected during the wingreplacement. In addition, during recent maintenance at an unknown time, the inboard left fuel sending unit was replaced. The most recent continuous airworthiness inspection was completed on June 26, 2019.