ERA24LA164

A total loss of engine power during final approach due to the pilot’s failure to recognize that the environmental conditions were susceptible to carburetor icing and apply carburetor heat, which resulted in the formation of carburetor ice. Contributing to the accident was the low altitude at which the pilot recognized the loss of engine power, reducing the amount of time to troubleshoot and address the problem.

While about 5 miles from the destination airport and maneuvering the airplane for a straight-in approach to the runway, the pilot began performing the prelanding checklist items, which included turning on the electric fuel pumps. When the flight was about 1/2 to 1 mile from the runway and about 800 ft above ground level (agl), the pilot recognized that the airplane was low, so she increased the throttle, but the engine did not respond. She verified that the mixture was full rich and that the fuel selector was on the fullest tank, and she checked the magnetos but did not apply carburetor heat. She observed a total loss of engine power, declared an emergency to the tower controller, prepared for ditching (because the flight was over water while on the approach), and ditched the airplane into the water below. Postaccident examination of the airplane revealed no preimpact failure or malfunction of the engine powertrain, ignition, or lubrication systems. Foreign debris was found inside the inlet section of the engine-driven fuel pump. Although this material matched the composition of inner layer material of a fuel supply hose, none of the fuel supply hoses recovered from the airplane’s engine compartment were found to be missing any section of the inner layer. Also, because the two electric fuel pumps that were on during the approach could allow fuel to bypass the engine-driven fuel pump in the event of its obstruction or failure, the foreign material likely did not contribute to the total loss of engine power. Although environmental conditions at the time of the accident were conducive to the formation of carburetor ice at cruise and glide power, the pilot did not recognize that or apply carburetor heat during any portion of the descent, or after the loss of power. Thus, it is likely that, during the approach, carburetor ice accrued when the engine was operating at a reduced power setting (consistent with glide power), resulting in the total loss of engine power. Also, although the airplane’s engine failure checklist specified applying carburetor heat, the low altitude at which the pilot recognized loss of engine power significantly reduced the amount of time available to troubleshoot and restore engine power to prevent the ditching.

On March 30, 2024, about 1448 eastern daylight time, a Piper PA-24-250 airplane, N7538P, was substantially damaged when it was involved in an accident near North Kingstown, Rhode Island. The private pilot and one passenger were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot stated that she flew the airplane earlier that day on two uneventful flights that lasted about 1 hour 45 minutes. Before the third flight, which was the accident flight, she performed a walk-around inspection of the airplane using the preflight checklist. She then started the engine and taxied to the runway, where she performed the before-takeoff checklist with no engine discrepancies observed. She departed with the fuel selector positioned to the right tank and proceeded to the destination airport. When the flight was 10 miles from the destination airport, she contacted the air traffic tower controller, who told her to expect a straight-in approach to runway 23 and to report when on a 2-mile final. When the airplane was 5 miles from the airport, the pilot began performing the prelanding checklist, which included turning on the electric fuel pumps. When the flight was about 1/2 to 1 mile from the runway and about 800 ft agl, the pilot noticed that the airplane was low based on the precision approach path indicator, so she increased the throttle, but the engine did not respond. The pilot verified that the mixture was full rich and that the fuel selector was on the fullest tank, and she checked the magnetos but did not apply carburetor heat. She observed that engine power was not restored. She declared an emergency to the tower controller, the passenger unlocked and unlatched the entry door (because the flight was over water while on the approach), and the pilot ditched the airplane into Narragansett Bay. Postaccident examination of the airplane identified substantial damage (including compression buckling) on both sides of the fuselage aft of the engine firewall, the right side of the aft fuselage, and the left side of the fuselage aft and slightly below the aft window. About 30 gallons of 100 low lead fuel and 4 gallons of water were drained from the wing tanks. Examination of the engine revealed that the throttle, propeller, mixture, and carburetor heat controls remained attached to their respective attach points, and all but the throttle control could be manipulated. The throttle control could not be moved due to postaccident corrosion. Crankshaft, camshaft, and valvetrain continuity was confirmed. Examination of the ignition, oil lubrication, and electric fuel pumps revealed no evidence of preimpact failure or malfunction. Examination of the engine-driven fuel pump revealed suction and pressure at the inlet and outlet fittings during hand actuation. Disassembly of the pump revealed that a piece of foreign material, about 1 inch long, 0.75 inch wide, and less than 0.05 inch thick, was found in the inlet section of the pump. The foreign material and all flexible fuel hoses from the engine compartment were sent to the NTSB Materials Laboratory for examination. The NTSB Materials Laboratory determined that the foreign material was consistent with nitrile rubber and that its composition matched the inner layer material of one of the recovered fuel hoses. Bisection of all the recovered fuel hoses revealed that none exhibited any missing or separated inner layer material. By design, the airplane’s engine-driven fuel pump delivered fuel to the carburetor, and the electric fuel pumps, which connect in parallel, provide redundancy and a means to bypass the engine-driven fuel pump in the event of its obstruction or failure. According to the airplane’s owner’s handbook, the approach and landing checklist specified to turn on the electric fuel pumps but to leave carburetor heat off unless icing conditions existed. The handbook’s engine failure checklist specified, in part, to turn on the electric fuel pumps, push the mixture control to full rich, apply carburetor heat, and check the ignition switch. The recorded temperature and dew point at the destination airport about the time of the accident were 55°F and 24.8°F, respectively. The calculated relative humidity for these conditions was 30.45%. According to the carburetor icing probability chart contained in FAA Special Airworthiness Information Bulletin CE-09-35, these conditions were favorable for the formation of carburetor icing at glide and cruise power.