What happened
On February 23, 2003, a Cessna 172N, registration OH-CAX, was conducting a local flight over Pertunmaa, Finland. The flight had departed from a runway prepared on the ice of Lake Ylä-Rieveli. The aircraft was flying at an altitude of approximately 150 meters, heading east-northeast toward the southern part of Lake Peruvesi.
During the flight, the aircraft was observed turning left and descending to an altitude of about 40 meters, accompanied by a likely reduction in engine power. Following this descent, the aircraft turned right and initiated a steep climb, which caused it to enter a cloud layer. While inside the cloud, the pilot lost spatial orientation and control of the aircraft. Eyewitnesses reported that the aircraft remained in the cloud for approximately 10 to 15 seconds before impacting the ice of Lake Peruvesi in a nearly vertical descent. The impact resulted in three fatalities, as the pilot and both passengers died at the scene. The aircraft was completely destroyed.
The investigation
The investigation examined the aircraft's technical condition, the pilot's flight experience, and the environmental conditions. Investigators reviewed maintenance records, which revealed that aluminum chips had been detected in the oil filter during the two previous maintenance sessions. These chips originated from two pistons and their pin plugs. While the engine showed significant wear on the camshaft and valve followers due to a clogged oil filter, the engine was still functioning at the time of the crash.
Findings
- The primary cause of the accident was the loss of the pilot's spatial orientation and subsequent loss of control after unintentionally flying into a cloud.
- The pilot was likely demonstrating flight maneuvers to the passenger in the front seat, which caused a lapse in monitoring weather conditions.
- The pilot entered the cloud during a steep climb or turning climb, and lacked the necessary instrument flight skills to recover.
- The aircraft entered a lower cloud layer (a fog bank) that was situated below the main cloud base.
- Although the engine had serious internal wear, there was no evidence of a technical malfunction contributing to the crash.