History of the Flight
The pilot in instruction, accompanied by an instructor, departed from Megève mountain airfield (Savoie) in a Jodel D140C (registration F-BMFV) for a training flight to the Saint Roch Mayères mountain landing area. After a reconnaissance, the pilot landed at the area then took off for a second runway circuit. On final, the pilot initiated descent at 120 km/h with power set to 1,500 rpm to maintain the approach slope with a tailwind. On short final, the aircraft was slightly below the slope, and the instructor asked for more power. The pilot reported being unable to increase power because the throttle control was already at what he believed to be full throttle. The instructor then took the controls and found he could not push the throttle further forward. Realizing insufficient power to reach the runway threshold, the instructor turned right to avoid an embankment, aiming for a shallower area suitable for an emergency landing. The aircraft struck the snow hard, bounced, and came to a stop several meters further.
Examination Findings
The accident site was difficult to access; initial examination relied on photographs. The landing area, oriented QFU 14-32, measures 330 m x 15 m at 5,118 ft altitude. Impact marks in the snow were visible before the threshold, indicating the skis contacted snow and the aircraft bounced. The left wing spar had ruptured at the wing root, and the left main landing gear strut was torn off. Propeller blades showed no distortion, but snow cover prevented determining engine power at impact.
Cockpit photographs show the ski control in the "skis down" position, fuel selector on front tank, mixture control full rich, engine throttle control in what the crew described as "fully forward, full throttle" (though examination later showed this position did not correspond to full throttle), and carburettor heating off.
Throttle Control Examination
The aircraft is equipped with a Lycoming O-360-A3A engine. Bench testing found no malfunction; performance was nominal. The throttle control system consists of two rods interconnected by a cable, sliding inside guides. After wreckage repatriation, the carburettor throttle valve control exhibited limited travel of about one centimeter from idle to full throttle, with greater-than-normal force required to move it. After several tests, the friction disappeared and full travel was achieved.
Examination of the installation revealed that the plate supporting the guide on the carburettor side was in contact with the exhaust muffler, causing angular displacement when the control was moved. The exhaust muffler casing was pierced where the plate rubbed. When the cockpit control was at full throttle, the angle between rigid sections of the guide reached the maximum permitted for the swivel connection, and a local deformation of about 0.1 mm was observed in the swivel connection, suggesting abutment during operation.
Comparison with two similar Jodel D140Cs showed variations in installation. One aircraft had similar contact and displacement; another had a thicker plate with no contact or movement. No blockage or friction point was observed on those aircraft.
Meteorological Conditions
A mountain report issued by the flying club indicated clear skies, 95% sunshine, moderate to light east-north-east wind, 0°C isotherm between 1,650 ft and 5,000 ft, and -10°C isotherm between 8,000 ft and 11,000 ft.
Crew Statements
The instructor stated that after a first landing, the pilot took off for a second circuit and detected no power problem. He noted that until very short final, no power adjustment was needed, and earlier adjustment might have revealed the control travel issue.
The instructor held a CPL(A), FI(A), and Mountain Instructor rating (skis), with about 3,700 flight hours. The pilot held a PPL(A) with about 350 flight hours, training for a skis mountain rating.
The report notes that given meteorological conditions, carburettor icing was considered a hypothesis, but no causal determination was made.