What happened
On January 5, 2000, an ultralight Cora 200 Arius, registration OH-U367, crashed near Mäntsälä, Finland. The flight began at Helsinki-Malmi airport, where the pilot intended to relocate the aircraft to a private landing field near his home. After performing two low passes over runway 27 at Malmi, the pilot proceeded toward Degeri and then toward the landing site near Hirvihaa.
During the final approach to the private field, the pilot attempted a low-speed landing technique using significant engine power. As the pilot reduced power to touchdown, the aircraft's sink rate increased. In an instinctive attempt to prevent the descent, the pilot pulled back on the controls, increasing the angle of attack. This caused the aircraft to stall at a very low altitude. The aircraft struck a field near the Mäntsälänjoki river, resulting in heavy damage to the airframe, engine, and landing gear. The pilot escaped the wreckage without injury.
The investigation
The investigation examined the aircraft's flight instruments, the pilot's approach technique, and the environmental conditions. Investigators analyzed the altimeter settings, noting that the pilot was flying using a QFE setting (local pressure) rather than the QNH (sea level pressure) provided by air traffic control, because he had not converted the pressure reading to inches of mercury (inHg) for his altimeter.
Furthermore, a flight test was conducted with a similar aircraft type to investigate the airspeed indicator. The investigation established that the airspeed indicator provided erroneous readings that varied based on the static pressure within the cockpit. The pilot was also found to have lacked sufficient training in short takeoff and landing (STOL) techniques for the specific approach being attempted.
Findings
- The immediate cause of the accident was the pilot's chosen approach method, which involved flying at a low speed with high engine power, leading to a stall when power was reduced.
- A significant contributing factor was a malfunctioning airspeed indicator that provided inaccurate readings. The pilot believed he maintained a sufficient speed margin above the stall speed, but he was actually flying very close to it.
- The pilot's lack of proficiency in STOL landing techniques contributed to the loss of control.
- The pilot failed to adjust his altimeter to the QNH setting provided by controllers, resulting in an incorrect understanding of his altitude above sea level.
- The aircraft's airspeed indicator error was not documented in the flight manual, nor was there a warning in the cockpit.