What happened
On January 10, 2021, a Piper Aircraft Inc. PA-18-150, registration LN-KCH, was performing a local training flight at Starmoen Airport in Norway. The aircraft, equipped with ski landing gear, had recently undergone a check-out for ski operations. During the takeoff roll on runway 15, the pilot utilized carburetor heat during the engine warm-up process. The engine reportedly stalled several times during this warm-up phase before the aircraft was cleared for departure.
Shortly after takeoff, at an altitude between 150 and 200 feet, the pilot deactivated the carburetor heat. Seconds later, the engine stopped abruptly without any prior signs of power loss or irregular running. To avoid the dense trees located directly ahead of the runway, the pilot executed a left turn toward an area with lower vegetation. Unable to restart the engine, the pilot performed an emergency landing. To prevent the ski gear from catching on low bushes, the pilot maintained a high pitch attitude during the descent. The aircraft struck the ground heavily, coming to a halt approximately 20 meters from the initial impact point. The aircraft sustained substantial damage, particularly to the fuselage, landing gear, and right wing, though the pilot escaped without injury.
The investigation
The Norwegian Safety Investigation Authority (NSIA) examined the aircraft and the engine components following the accident. Investigators found the fuel selector valve in the closed position. The pilot stated that while the engine was started using the left tank, the intention was to switch to the right tank during the run-up; however, the pilot inadvertently turned the valve to the closed position. The design of the selector valve, which uses a short end to indicate the selected position, was noted as a potential source of confusion.
Investigators also analyzed the possibility of carburetor icing. Based on the ambient temperature and dew point at the time of the accident, the risk of icing was determined to be minimal. Furthermore, the sudden nature of the engine failure, without the typical fluctuations in RPM associated with icing, suggested another cause. While ice was found in the carburetor and exhaust pipes during the post-accident inspection, this was attributed to snow entering the engine compartment during the hard landing and subsequently freezing.
Findings
- The engine failure was likely caused by the fuel selector valve being inadvertently set to the closed position during the pre-flight checks.
- The specific design of the fuel selector valve, where the short end indicates the active tank, may have contributed to the pilot's error.
- The pilot's limited experience with this specific aircraft type and ski operations may have influenced the handling of the emergency.
- The use of carburetor heat during takeoff is not standard procedure and can result in a 10-15% loss of engine power.