What happened
On October 5, 2017, an ultralight aircraft, a Colomban MC30 identified as 31TM, was performing a local flight from Toulouse Lasbordes. During the takeoff roll on runway 33, the aircraft veered to the left, exited the paved surface, and struck a pylon. The impact caused the aircraft to overturn onto its back, resulting in one fatality and heavy damage to the airframe.
The investigation
The investigation focused on the mechanical condition of the aircraft and the physical state of the pilot. Investigators examined the wreckage and found no anomalies in the flight controls. However, technical inspections revealed that the left spark plug showed signs of a heavy fuel mixture. Specifically, the carburetor starter return spring was disconnected from its fixed attachment point, which may have caused an abnormal butterfly valve position. This condition likely led to an excessively rich mixture, potentially causing a loss of engine power during the takeoff power increase.
Additionally, the investigation analyzed the independent braking system. It was determined that the left brake lever engages the left wheel significantly earlier than the right lever does for an equal amount of movement. This mechanical characteristic could have induced asymmetric braking during the takeoff roll.
Regarding the pilot, autopsy findings were consistent with a sudden medical incapacity that may have occurred during the takeoff sequence.
Findings
- The investigation identified a potential loss of engine power due to an excessively rich fuel mixture caused by a disconnected carburetor starter return spring.
- The braking system was found to be asymmetrical, as the left brake engages before the right.
- Medical evidence suggested the pilot may have suffered a sudden medical event during the takeoff roll.