N7639PPiper PA-24-180 · 1961

On December 12, 2020, about 1250 central standard time, a Piper PA-24-180 airplane, N7639P, was substantially damaged when it was involved in an accident near Nashville, Tennessee. The commercial pilot incurred minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.

The pilot reported that he departed with 54 gallons of fuel for the cross-country flight and switched tanks every 30 minutes while en route. During the approach, about 7 nautical miles from the destination, the pilot reported that he observed a “significant drop in manifold pressure and change in engine noise, best described as a steady roll-back.” He reported that at the time of the loss of total engine power, the airplane was still in a “cruise configuration” with the mixture leaned, the rpm was 2,400, and the manifold pressure was 23 inches.

The pilot pitched the airplane for best glide speed, began looking for an open area to land, and started troubleshooting the loss of power. He reported that he switched the fuel selector from the left tank to the right tank, moved the mixture and propeller levers full forward, turned on the boost pump, and engaged the engine starter; however, none of the actions restored power.

The pilot continued his approach to a field that had trees and a house in the flight path. Just prior to impact the pilot reported that he could feel the onset of an aerodynamic stall as the airplane cleared the top of the house. He subsequently lowered the nose, and the airplane touched down hard and skidded to a stop in the field.

Examination of the airplane by a Federal Aviation Administration (FAA) inspector found that the fuselage and both wings sustained substantial damage. Flight and engine control continuity was established. A total of about 7 gallons of fuel was drained from the left fuel tank, and 1/8 to 1/4 cup was drained from the right fuel tank. There was no debris or discoloration noted with the fuel, and no damage to the fuel tanks or evidence of fuel leakage was discovered at the accident site.

An engine examination found that when the propeller was manually rotated, all cylinder valves operated normally, and thumb compression was found on each cylinder. Magneto spark and timing was confirmed. When the carburetor was disassembled, 4-5 teaspoons of fuel remained in the float bowl.

The main fuel line was disconnected from the carburetor inlet and about 5 to 6 drops of fuel was observed to drain from the line. There was no evidence of fuel at the inlet side of the electrical fuel pump nor was there any remnants of fuel discovered at the outlet side of the engine driven fuel pump. The carburetor heat lever was found in the off position.

The pilot reported postaccident that he had not turned on the carburetor heat in the 30 minutes before the loss of engine power and could not recall using the carburetor heat after the loss of engine power. He also estimated that each fuel tank should have been about 1/3 to 1/2 full about the time of the loss of power. He reported the total flight time was about 2 hours and 20 minutes.

Data downloaded from the engine monitoring instrument was consistent with what the pilot reported.

Review of the FAA Carburetor Icing Chart found that the airplane was at risk of serious icing at glide power given the atmospheric conditions reported near the accident site.

The airplanes pilot’s operating handbook (POH) stated that the total fuel capacity was 60 gallons, with 2 gallons of unusable fuel for the left- and right-wing fuel tanks.

The following emergency procedure was provided for a loss of engine power during flight (see figure 1).

Figure 1- Excerpt from the POH referencing the engine power loss during flight emergency procedure