What happened
On June 3, 2017, a Humbert Aviation Tetras B.T. microlight, identified as 54AMK, was performing a local flight departing from Nancy-Malzéville aerodrome. The pilot, accompanied by one passenger, taxied to the intersection of runways 08/26 and 04/22, utilizing approximately 800 meters of runway 04 for takeoff.
During the initial climb, immediately after passing the end of the runway, the aircraft entered a spin with a steep nose-down attitude. The aircraft struck the ground in a grass field approximately 250 meters from the runway end, followed by a post-impact fire that destroyed the airframe. The accident resulted in two fatalities.
The investigation
The investigation examined the wreckage and the flight control systems of the aircraft. Investigators found the flight control linkages were intact, though some elements near the fuel tanks had melted due to the fire. The elevator trim was found in a nose-up position, and the cable was blocked in that position. The flap control was set to the takeoff position.
Regarding the engine, the power unit was rotating at the time of impact, and the examination of the engine and carburetors showed no malfunctions. However, the fuel valve, which lacks a guard to prevent accidental movement, was found in a state where its position during flight could not be definitively confirmed due to fire damage. The investigation also noted that the aircraft was not equipped with a stall warning system or an airframe parachute.
Findings
Several factors contributed to the loss of control during the critical climb phase:
- The elevator trim was set to a nose-up position, which may have caused flight characteristics that caught the pilot off guard.
- The pilot's lack of recent experience in this specific type of microlight likely prevented a timely reaction to the deteriorating flight parameters.
- The absence of a stall warning device made it difficult to detect the onset of the stall.
- It could not be ruled out that the fuel valve was closed or partially closed, potentially restricting fuel supply after several minutes of operation.
Safety action
To assist users in establishing more effective checklists, the manufacturer intends to include information regarding optional equipment in the generic version of the operation and maintenance manual.