What happened
On 26 February 2022, a Jodel D140 (registration F-BMFV) was conducting an instruction flight at the Saint Roch Mayères mountain landing area. The flight, operated by Aéroclub de Megelle, involved a pilot in instruction accompanied by an instructor. After completing an initial landing and reconnaissance, the crew attempted a second runway circuit.
During the final approach, the pilot maintained an engine speed of approximately 1,500 rpm to stay on the approach slope against a tailwind. As the aircraft reached short final, the instructor requested a slight increase in power to correct a descent below the recommended slope. However, the pilot reported being unable to increase the engine power, stating the throttle was already at the forward limit. Upon taking control, the instructor confirmed that the throttle could not be pushed further forward. To avoid striking an embankment at the runway threshold, the instructor steered the aircraft toward a shallower slope. The aircraft struck the snow-covered ground with significant force, causing the plane to bounce before coming to a stop.
The investigation
Because the accident site was difficult to access, investigators relied on photographs taken by the instructor and aerial imagery. The examination of the wreckage revealed that the left wing spar had ruptured at the wing root and the left main landing gear strut had been torn off. The propeller blades showed no signs of distortion.
Investigators examined the engine and the throttle control mechanism. The Lycoming engine was tested on a bench and showed no mechanical malfunctions. The investigation focused on the control system connecting the cockpit throttle to the carburetor. While the system was functional during workshop tests, investigators noted several anomalies. The plate supporting the control guide on the carburetor side was in contact with the exhaust muffler, causing the plate to displace when the control was moved. Furthermore, at the full throttle position, the swivel connection in the control guide reached its maximum permitted angle, suggesting a potential mechanical limit or interference during flight.
Findings
- The aircraft suffered substantial damage following a hard impact with the snow.
- The pilot was unable to increase engine power because the throttle control reached a physical limit during the approach.
- The investigation could not definitively prove the cause of the restricted travel, but noted that the throttle control assembly interacted with the exhaust muffler and reached the limit of its swivel connection's range.
- Carburetor icing was ruled out as a likely cause due to the specific heated exhaust design of this aircraft's propulsion system.