What happened
On January 29, 2001, an Air Command gyrocopter, registration 95-LA, departed from Persan Beaumont airfield for a local flight. The aircraft was carrying a pilot and one passenger for a discovery flight. Approximately ten minutes into the flight, witnesses on the ground observed the engine stuttering, momentarily stopping, and then restarting several times before failing completely. Following the final engine failure, the gyrocopter entered a steep, spiral descent and crashed into a private garden. The impact resulted in two fatalities and the destruction of the aircraft.
The investigation
The investigation focused on the engine's performance and the environmental conditions at the time of the accident. Investigators examined the wreckage, noting that the airframe had suffered significant structural damage from a high-vertical-load impact. While the engine and propeller showed only minor damage, the investigation revealed that the two carburetors had become disconnected from the intake manifolds.
Engine tests conducted on a test bench showed that the engine functioned normally under standard conditions. However, the investigation also noted that the engine was not equipped with a carburetor heating system. Meteorological data from nearby stations indicated high humidity and temperatures conducive to severe carburetor icing. Furthermore, the investigation noted that the Rotax 912 UL/S engine used in the aircraft was not officially rated for use in rotary-wing aircraft.
Findings
- The primary cause of the engine failure was likely simultaneous carburetor icing in both carburetors, which led to the engine's complete shutdown.
- The pilot failed to execute an immediate emergency descent following the initial engine fluctuations, choosing instead to maintain level flight.
- By the time the engine stopped completely, the aircraft's forward airspeed had likely dropped too low to maintain sufficient rotor RPM for autorotation.
- The pilot's decision to fly in weather conditions presenting a severe risk of icing was a contributing factor, as the aircraft lacked any carburetor anti-icing equipment.