What happened
On October 16, 2024, an SNJ-3 aircraft, registration OH-NAT, was performing a test flight at Räyskälä aerodrome in Lopell, Finland. The flight was intended to verify the aircraft's performance following recent maintenance work. The aircraft departed from runway 26L at 12:05 local time. The initial climb appeared normal, though the pilot performed the takeoff with the flaps and landing gear partially extended.
Shortly after reaching an altitude of approximately 100 meters, witnesses reported hearing several distinct engine irregularities, followed by the engine cutting out completely. In an attempt to return to the airfield, the pilot executed a steep right-hand turn. During this maneuver, the aircraft lost altitude rapidly, causing the right wingtip to strike the ground before the aircraft impacted trees at the edge of a forest. The impact caused the engine and wing to separate from the fuselage, and a subsequent fuel fire completely destroyed the aircraft. Both the pilot and the passenger sustained fatal injuries.
The investigation
The Finnish Safety Investigation Authority (OTKES) examined the mechanical condition of the aircraft, the maintenance history, and the flight's operational circumstances. The investigation included technical analysis of the engine, the fuel system, and the propeller governor. Investigators also reviewed cockpit-related factors, such as the pilot's experience with this specific aircraft type and the potential impact of the 'startle effect' during the emergency. Additionally, the investigation looked into the challenges of maintaining safety standards for historical aircraft where manufacturer support is no longer available.
Findings
- Fuel starvation was identified as the primary cause of the engine failure, as the flow of fuel to the engine became restricted.
- The aircraft had experienced long periods of inactivity, with fewer than 4/40 flight hours recorded in the previous four years, which can lead to the degradation of components and lubricants.
- The pilot's decision to execute a steep turn back to the field was contrary to the aircraft's flight manual, which instructs pilots to continue straight ahead with minimal control inputs following an engine failure during takeoff.
- There was a discrepancy between the aircraft's manual, which instructed switching fuel tanks during flight, and the informal advice within the vintage aircraft community, which cautioned against such movements.
- The pilot, while highly experienced in commercial aviation, had limited experience operating this specific historical aircraft type.
Safety action
- The OTKES recommends that the Federal Aviation Administration (FAA) notify owners and operators of this aircraft type regarding the risks of aging and wear in the fuel tank selector valve and its associated mechanisms.