What happened
On July 4, 1999, a private Rutan Stag-EZ (registration I-MEZE) departed from Cranfield, UK, on a non-stop flight toward Locarno, Switzerland. After traversing England and France, the pilot began ascending through the Alps. During the flight, the engine experienced an initial failure, which the pilot managed by switching fuel tanks. However, as the flight progressed through the Swiss mountains, the pilot encountered deteriorating weather conditions.
While navigating through the valleys, the engine suffered a second, definitive failure due to fuel exhaustion. The aircraft subsequently entered a vertical spiral and collided with the forest near Gresso. The pilot sustained serious injuries to the legs, and the aircraft was destroyed.
The investigation
SUST examined the wreckage and flight data, including GPS analysis, which reconstructed the flight path. The investigation established that the aircraft's fuel tanks were empty at the time of the accident. Investigators also noted that the aircraft was operating under a special certificate of airworthiness that restricted operations to daytime VFR only.
Physical evidence at the scene showed the instrument panel had detached, and the radio had been displaced from its mount. The investigation also reviewed the pilot's flight profile, noting that the aircraft had been operating at altitudes between 17,000 and 18,000 feet. The investigation found that the pilot had continued the flight into Instrument Meteorological Conditions (IMC) despite instructions from Geneva Information to maintain VFR protocols.
Findings
- The primary cause of the accident was the loss of control of the aircraft following an engine failure caused by fuel exhaustion and the decision to continue a VFR flight in IMC.
- A significant contributing factor was the pilot's prolonged exposure to high altitudes (above 4,000 m/ft) without the use of supplemental oxygen, which likely impaired judgment.
- The aircraft's fuel reserves were exhausted during the flight.
Safety action
- The investigation suggests evaluating whether the use of supplemental oxygen should be made mandatory for all non-commercial flights above 10,000 feet to align with existing regulations.