Nashville, TN, USA
N7639P
PIPER PA24
The private pilot had completed most of a cross-country flight and about 7 miles from the destination airport during the approach, the engine lost all power. Despite several troubleshooting actions, the pilot was unable to restore engine power. He subsequently completed a forced landing in a field where the airplane touched down hard resulting in substantial damage to the fuselage and both wings. A postaccident examination of the airplane and engine found no evidence of mechanical malfunctions or failures that would have precluded normal operation and the fuel tanks were not breached. A carburetor icing probability chart revealed that serious icing was to be expected at glide power. The pilot had not used carburetor heat within the preceding 30 minutes prior to the loss of engine power, and he could not recall using carburetor heat after the loss of engine power. Additional examination of the airplane found about 7 gallons of fuel in the left fuel tank, which was the reported tank selected at the time of the engine failure. About 1/4 to 1/8 of a cup of fuel was found in the right tank, which was the tank the pilot switched to after the engine failure. Trace amounts of fuel were located throughout the fuel lines and carburetor. Given that sufficient fuel was found in the tank that was selected when the loss of power occurred, it is likely that the accumulation of carburetor resulted in a total loss of engine power. In addition, after the loss of engine power, the fuel selector was switched to a tank that was found to have an unusable amount of fuel, which further reduced the possibility that engine power could be restored.
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
The pilot’s failure to use carburetor heat during the approach, which resulted in a loss of engine power due to carburetor icing.
Source: NTSB Aviation Accident Database
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