Accident Details
On October 18, 2017, at about 1000 eastern daylight time, a Beech A24R, registration N400LE, was substantially damaged in an accident near Manteo, North Carolina. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The private pilot undergoing instruction (PUI) sustained serious injuries, while the flight instructor sustained minor injuries.
Flight Sequence
According to the flight instructor, preflight inspection and engine run-up revealed no discrepancies. The PUI stated that about 3 seconds after rotation, while the airplane was halfway down the runway at no more than 10 to 15 ft above the runway with the landing gear extended, he heard a "pop" sound from inside the airplane. He attributed the sound to a tripping circuit breaker but did not check the circuit breakers. He did not change the landing gear position and continued flying.
The flight instructor reported that at 100 ft altitude, the cockpit filled with smoke and electrical wires on her side caught fire, contacting her leg. The PUI verbalized "fire" three times, and after losing intercom capability, he asked if she wanted him to secure the battery and alternator switches. She verbally agreed. The PUI initially turned off the battery and later the alternator switches, though the PUI indicated that the battery, alternator, and avionics switches remained on until he secured them postaccident because she did not respond to his hand motions. The instructor took the controls and executed a 180° turn near the VOR antenna to return to the runway. The PUI noted that she did not roll out of the turn and did not arrest the descent, resulting in impact in a slightly left-wing-low, nose-low attitude, which the instructor characterized as a hard landing. The instructor stated that the emergency procedures section of the Pilot's Operating Handbook did not contain a checklist for an electrical in-flight fire. Neither pilot felt airframe buffet or recalled hearing the stall warning system.
Postaccident Examination
FAA inspectors examined the accident site. The airplane first impacted on airport property east of runway 17 near the approach end, and came to rest upright about 500 ft and 212° from the initial impact. In the cockpit, a wire with melted insulation was found hanging from under the right side of the instrument panel.
Subsequent examination by an airframe manufacturer representative with FAA oversight revealed an avionics switch and associated wiring installed on April 12, 2017. The switch was located at the top center of the instrument panel above the autopilot control unit. One wire from the switch connected to the electrical bus bar near the landing gear circuit breaker; the other connected to the "COM 2" circuit breaker. Both wires showed evidence of electrical arcing where they crossed the top aft edge of the autopilot control unit and at a vertical support member. The wire from the bus bar had most of its insulation melted or missing; the wire from the COM 2 breaker had melting where it was near the other wire. The wires were tie-wrapped together and to a larger wire bundle near the bus bar, with no mechanical protection or supports along their length, and no circuit protection between the bus bar and the avionics switch. The wires had a distinct bend where they passed around the vertical support member. Since installation, the airplane had accrued about 96 hours. Advisory Circular 43.13-1B specifies that electrical wires require circuit protection near the power source, that metal stand-offs maintain clearance, and that wires be routed to prevent chafing.