CEN19LA306

The pilot was conducting a postmaintenance flight. Shortly after liftoff and while the airplane was in a climbing left turn, the airplane lost total engine power. The pilot reported that, about 7 seconds after liftoff he heard the engine “splutter” as it decelerated from takeoff power toward idle. He pushed the control stick forward to reduce the airplane's angle of attack, but the airplane impacted terrain in a nose-down attitude. One witness reported that, after the loss of engine power, the airplane’s left wing dropped, and the airplane entered an aerodynamic spin that continued about one-half of a rotation before the airplane impacted the ground. The airplane sustained substantial damage to the forward fuselage and engine mount during impact. A postaccident engine examination revealed no evidence of a mechanical failure that would have resulted in the total loss of engine power. The airplane’s fuel tank cap had a cracked rubber seal that had hardened from age, and the fuel cap vent holes were small and partially obstructed by the seal. An inadequately vented fuel cap could have resulted in a negative pressure within the fuel tank and fuel starvation to the engine. Additionally, the carburetor heat flexible hose was found disconnected from the carburetor, and there was no attachment hardware present. The weather conditions at the time and location of the accident were conducive to a serious accumulation of carburetor icing with the engine at glide (descent) power. On the basis of the available evidence, the investigation was unable to determine whether inadequate fuel tank venting or carburetor icing caused the total loss of engine power. However, after the loss of engine power, the pilot likely exceeded the airplane’s critical angle of attack, and the airplane subsequently entered an aerodynamic stall and spin from which recovery was not possible due to the airplane’s low altitude.

On September 7, 2019, about 1007 central daylight time, a Pietenpol Sky Scout airplane, N1932G, was substantially damaged when it was involved in an accident near Kingsbury, Texas. The pilot was seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that the purpose of the postmaintenance flight was to verify proper engine operation and to monitor the water temperature. He completed a short ground test of the engine, during which the engine ran with no anomalies and developed a maximum speed of 2,100 rpm. After a short break, he restarted the engine and taxied the airplane for a takeoff on runway 14. The pilot reported that he made an uneventful takeoff with the engine developing 2,100 rpm, but about 7 seconds after liftoff the airplane had a total loss of engine power about 100 ft above the ground while in a climbing left turn. The pilot recalled hearing the engine "splutter" as it decelerated from takeoff power toward idle. He pushed the control stick forward to reduce the airplane's angle of attack, but the airplane impacted terrain in a nose-down, wings-level attitude. The pilot reported that the airplane sustained substantial damage to the forward fuselage and engine mount during the accident. There were multiple witnesses who reported that the airplane had a total loss of engine power shortly after liftoff and that the airplane impacted terrain in a nose down, left wing down attitude. A couple of the witnesses reported that after the loss of engine power the airplane’s left bank angle increased as the nose dropped. One of the witnesses reported that after the loss of engine power the airplane’s left wing dropped and the airplane entered an aerodynamic spin that continued about one-half of a rotation before it impacted the ground in a nose-down attitude. The airplane builder stated that the airplane had accumulated 34.43 hours since it was built in 1999. The airplane’s Ford model A engine had undergone recent maintenance to resolve an excessive water temperature condition. The engine was disassembled, and the cylinder bores were reamed to increase clearances. The airplane builder stated that there were no anomalies with engine operation or water temperature during postmaintenance ground testing. Postaccident examination revealed that the fuel shutoff valve was open, the fuel lines were clear of debris, and the gascoloator sediment bowl and fuel filter screen were not contaminated. The airplane’s fuel tank cap had a cracked rubber seal that had hardened from age, and the fuel cap vent holes were small and partially obstructed by the seal. The carburetor heat flexible hose was not connected to the carburetor, and there was no attachment hardware present to keep the hose from disconnecting from the carburetor. A postaccident engine examination did not reveal any evidence of a mechanical malfunction with the valves, pistons, and piston rods. Clean oil was present in theengine and there was no metal shavings or foreign debris in the oil sump. There were no anomalies identified with the carburetor. The magneto produced spark on all ignition leads when tested. The spark plugs appeared undamaged and exhibited normal wear signatures. The engine examination revealed no evidence of a mechanical malfunction that would have resulted in a loss of power. According to a carburetor icing probability chart contained in Federal Aviation Administration Special Airworthiness Information Bulletin CE-09-35, Carburetor Icing Prevention, the recorded temperature and dew point temperature near the accident site on the day of the accident were in the range of susceptibility for the formation of serious carburetor icing at glide (descent) engine power. According to the bulletin, a pilot should use carburetor heat when operating the engine at low power settings or while in weather conditions where carburetor icing is probable.