What happened
On August 12, 2016, a Dyn’Aero MCR01M ultralight, identified as 84-MP, departed from an unpaved 350-meter airstrip at Col de Bacchus. Shortly after takeoff, a witness observed the aircraft executing a left turn at a low altitude. During this maneuver, the aircraft entered a sudden descent and pitched toward the ground, ultimately impacting a densely forested area approximately 150 meters to the left and below the runway.
The impact occurred at an altitude of approximately 3,020 feet. The crash resulted in one fatality and the total destruction of the aircraft.
The investigation
Investigators examined the wreckage and found that the aircraft struck vegetation and the ground with a steep nose-down attitude. At the time of impact, the propeller was rotating, the fuel valve was open, and fuel remained in the tanks. The flight controls for roll, pitch, and yaw were all functional and continuous at the moment of impact, and the flaperons were set in the takeoff position.
An examination of the engine, which had 733 total operating hours, revealed several issues. While much of the damage was attributed to environmental exposure following the crash, investigators found evidence of prior wear, including friction between the crankshaft bearings and bearings, as well as cylinder wall irregularities. Notably, a particle composed of aluminum and carbon fibers was discovered within the main jet of the left carburetor.
Meteorological data indicated a north to northeast wind at 5 to 10 knots, with gusts up to 20 knots. The topography of the site, characterized by an abrupt northwest escarpment, was also analyzed for its potential to create turbulent downdrafts.
Findings
- The presence of a foreign particle in the left carburetor's main jet may have obstructed fuel delivery, causing a significant loss of engine power during the initial climb.
- The aircraft's position during the left turn likely placed it within a zone of turbulent air and downdrafts created by the local terrain and wind conditions.
- The accident was caused by a loss of control in flight at low altitude, likely triggered by the combination of reduced engine power and adverse aerodynamic conditions.