What happened
On the morning of November 7, 1963, at Geneva-Cointrin Airport, an electrical mechanic was performing radio and communication equipment checks on a Cessna 172, registration HB-CPY. After completing the inspections at a testing area near the Swissair hangars, the mechanic began taxiing the aircraft back toward the Pilatus hangar.
At the same time, a Convair CV-440 Metropolitan, registration HB-IMF, was positioned on a run-up pad conducting engine tests. Due to a strong west wind of approximately 20 knots, the larger aircraft was positioned facing into the wind. As the Cessuna 172 crossed the longitudinal axis of the Convair CV-440, passing roughly 25 to 30 meters behind its tail, it entered the powerful propeller blast of the larger aircraft. The force of the wash caused the light aircraft to yaw sharply and flip over its left wingtip and propeller hub, landing on its back.
The investigation
The investigation examined the taxi path taken by the mechanic, the weather conditions, and the positioning of the aircraft involved. The investigation noted that the mechanic was experienced with the aircraft type and had been trained in taxiing single-engine aircraft. The investigation also reviewed the engine settings of the Convair CV-440 at the time of the incident, noting that the engines were at varying power settings (2200 RPM and 1500 RPM) during the run-up.
Findings
- The primary cause of the accident was the Cessna 172 crossing the propeller blast of the Convair CV-440 at an unsafe distance.
- A strong 20-knot wind contributed to the incident by influencing the positioning of the aircraft and the dynamics of the encounter.
- The taxi route chosen by the mechanic was inefficient; a different path would have allowed for a much safer distance from the larger aircraft's exhaust and propeller wash.
- The mechanic sustained only minor abrasions and no serious injuries, though the Cessna 172 sustained heavy damage, estimated at 80–90% of its value, including a deformed fuselage, wings, and landing gear.