ERA23FA103 · Piper PA28 140

The accident occurred about 5 miles from the destination airport near the conclusion of a short cross-country flight. Automatic dependent surveillance - broadcast (ADS-B) data showed that about 2 miles from the accident location the airplane’s descent rate rapidly increased to 500 ft/min with the airspeed staying just above 90 knots. The descent rate slowed to 200 ft/min before it rapidly increased to more than 1,500 ft/min during the final minute of flight. A performance study showed that a steep banked turn would have been required to orient the flight path with the wreckage direction and that the airplane’s final known speed was close to its stall speed in the turn. A witness reported seeing the airplane in a nosedive with two spiral trails of black smoke about 5 to 10 ft behind the airplane; however, she did not observe any fire from the airplane.

Six days before the accident, the pilot brought his airplane to a mechanic, as it had an excessive engine rpm drop during a run-up magneto check. The mechanic changed some spark plugs but did not have a chance to run the engine. Three days before the accident, the pilot arrived at the mechanic’s hangar and performed a ground run of the engine on the ramp area near the mechanic’s hangar so the mechanic could listen to the engine. As soon as the pilot ran the engine, the mechanic knew that the new spark plugs did not correct the problem as the engine was “skipping.” The pilot shut down the engine and the mechanic informed the pilot that the airplane was not to be flown until he could investigate further, and he would most likely be able to do it the following week. The mechanic later moved the pilot’s airplane from the ramp in front of his hangar, into the pilot’s hangar, as bad weather was forecast. The mechanic added that he had not completed the maintenance on the airplane and that the pilot did not contact him before departing on the accident flight to see if the maintenance had been completed. Postaccident Examination of the wreckage revealed that the hold-down nuts on both magnetos were only finger tight. Some rotational damage was noted on both propeller blades. No other preimpact mechanical malfunctions were identified.

Due to the combination of black smoke that the witness observed trailing the airplane, the limited rotational damage signatures that were observed on the propeller blades, and the only finger tight magneto hold-down nuts that were found during the postaccident engine examination, it is likely that the loose magnetos detrimentally affected ignition, which resulted in a partial loss of engine power. Given that there was a known, unresolved maintenance issue that existed prior to the flight, had the pilot positively affirmed the airplane’s airworthy condition with the mechanic prior to the flight, it is likely the accident would not have occurred. Additionally, the witness description of the airplane’s final descent, the airplane’s calculated speed during it’s final maneuvering, and the lack of a horizontal debris field observed at the accident site suggested that the airplane entered an aerodynamic stall before it impacted the ground.

Verbatim NTSB analysis and probable cause from the NTSB dataset