What happened
On November 5, 1967, at approximately 12:25 local time, a Piper J3C, registration HB-OGV, was attempting a takeoff from runway 24 at La Chaux-de-Fonds Airport. The pilot, who was flying solo, had arrived at the airfield from Gruyères earlier that morning. While the weather conditions had been favorable during the initial arrival, conditions had deteriorated by the time the return flight was attempted.
As the pilot lined up for takeoff into a strong headwind and applied full power while maintaining a back elevator position, a gust of wind lifted the aircraft from the runway after only a few meters of travel. The aircraft lifted off in a three-point attitude but quickly pitched up excessively. This caused the aircraft to lose control, roll onto its left wing, and strike the ground. The aircraft came to rest approximately 35 meters from the start of the runway, roughly 50 meters left of the centerline. The pilot sustained minor injuries to the head, and the aircraft was 75% destroyed.
The investigation
Investigators examined the aircraft's maintenance history, the pilot's experience, and the prevailing meteorological conditions. The Piper J3C was found to be in a valid state of airworthiness, with the engine and airframe having relatively low hours since their last major overhaul. The pilot, an experienced student pilot with nearly 35 flight hours, had recently passed his private pilot examination.
Meteorological data revealed that while the pilot had checked local conditions via telephone earlier, the weather had shifted significantly. At the time of the accident, the sky was overcast, and the wind was gusting from the west-southwest at 20 to 30 knots. Crucially, the investigation noted that the pilot had not reviewed the latest aeronautical forecasts, which had warned of a cold front and significant turbulence.
Findings
- The primary cause of the accident was improper use of the elevator controls during the initial phase of takeoff in heavy headwind conditions.
- By maintaining a back elevator position while applying full power into a strong headwind, the pilot failed to account for the high relative wind speed acting on the wings.
- The wind speed was nearly equal to the aircraft's stall speed at the given attitude, meaning a single gust was sufficient to lift the aircraft prematurely.
- The excessive pitch-up caused by the held control position led to an aerodynamic stall and subsequent loss of control.