Accident Overview
On December 12, 2020, at approximately 1250 central standard time, a Piper PA-24-180 airplane, registration N7639P, sustained substantial damage during an accident near Nashville, Tennessee. The commercial pilot incurred minor injuries. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a personal flight.
Pilot's Account
The pilot reported departing with 54 gallons of fuel for the cross-country flight and switching fuel tanks every 30 minutes. During the approach, about 7 nautical miles from the destination, he observed a “significant drop in manifold pressure and change in engine noise, best described as a steady roll-back.” At the time of the power loss, the airplane was in a cruise configuration with the mixture leaned, the rpm at 2,400, and manifold pressure at 23 inches.
The pilot pitched for best glide speed, searched for an open landing area, and troubleshooted the power loss. He switched the fuel selector from left to right tank, moved mixture and propeller levers full forward, turned on the boost pump, and engaged the starter, but power was not restored.
He continued toward a field with trees and a house in the flight path. Just before impact, he felt the onset of an aerodynamic stall as the airplane cleared the house, then lowered the nose. The airplane touched down hard and skidded to a stop.
Examination Findings
A Federal Aviation Administration inspector found substantial damage to the fuselage and both wings. Flight and engine control continuity was established. About 7 gallons of fuel were drained from the left tank, and only 1/8 to 1/4 cup from the right tank. No debris or discoloration was noted in the fuel, and no damage to the tanks or evidence of leakage was found.
Engine examination revealed normal cylinder valve operation, thumb compression on each cylinder, and confirmed magneto spark and timing when the propeller was manually rotated. The carburetor float bowl contained 4-5 teaspoons of fuel. The main fuel line from the carburetor inlet yielded 5-6 drops of fuel. No evidence of fuel was found at the inlet side of the electric fuel pump or at the outlet side of the engine-driven pump. The carburetor heat lever was found in the off position.
Post-Accident Details
The pilot reported not using carburetor heat in the 30 minutes before the power loss and could not recall using it after. He estimated each tank should have been about 1/3 to 1/2 full at the time of power loss. Total flight time was about 2 hours and 20 minutes. Data from the engine monitoring instrument was consistent with the pilot's report.
Carburetor Icing Risk
Review of the FAA Carburetor Icing Chart indicated that, given the atmospheric conditions near the accident site, the airplane was at risk of serious icing at glide power.
The airplane's pilot's operating handbook stated total fuel capacity as 60 gallons with 2 gallons unusable in each wing tank. Emergency procedures for loss of engine power were provided in the POH but were not reproduced here.