Piper PA-24-250 N8051P accident near Tyler, Texas

Probable cause

An electrical system surge for a reason that could not be determined that resulted in an overvoltage event, internal damage to electronics equipment, smoke in the cockpit, and a gear up landing.

NTSB analysis

The pilot reported that just before the accident flight, the airplane’s battery was not charged, and the airplane was connected to a truck using jumper cables to start the engine. The pilot then proceeded with the flight and shortly after departure he noted sparks and smoke emanating from behind the instrument panel. He turned off the generator and the sparking stopped. He turned the electrical power back on a few times to notify air traffic control and to attempt to lower the landing gear. He believed that the landing gear was down and locked based on position of the gear itself and by noting the position of the emergency extension handle, but upon landing the airplane’s landing gear collapsed which resulted in substantial damage to the fuselage. The pilot noted that before the landing he did not physically grab the emergency landing gear extension handle to verify that it was fully forward (down and locked).

Postaccident examination of the airplane by a mechanic revealed several marked and unmarked circuit breakers that were tripped. Testing of those circuits revealed that resetting the breakers and applying power to the aircraft electrical system resulted in the breakers tripping again. Further testing revealed that removal of the protected devices resulted in some of the protected circuits drawing excessive current and continuing to trip while others showed no further current draw and did not trip. It was found that many of the devices removed had internal damage and excessive current draw. One item tested, the Garmin GMA340 Audio Panel, would produce smoke from the rear of the unit when power was applied and the smoke continued for several seconds after power was removed. The mechanic did not test the airplane’s generator or voltage regulator. Investigators were unable to test the generator or voltage regulator as the wreckage was disposed of before the testing could take place.

Based on the postaccident testing, the smoke reported by the pilot was likely from the internally compromised audio panel. The internal damage to the audio panel and other avionics components was consistent with a power surge due to a faulty voltage regulator, but since the generator and voltage regulator were not tested the definitive reason could not be determined. During the event the pilot attempted to lower the landing gear, and he believed it was down but the collapse upon landing is consistent with it not having reached the fully down and locked position.

Text from the NTSB. Open the NTSB docket for CEN25LA079 for the full record.