What happened
On September 3, 1963, a Smaragd CP-301-S, registration HB-SEG, departed from Prangins aerodrome for a training flight to Sion. Shortly after takeoff from runway 04, the pilot and instructor noticed an unusual noise coming from the engine accompanied by a burning smell. Because the aircraft was already in motion, an immediate abort was not possible.
The instructor took control of the aircraft to initiate a return to the airfield. While performing a tight left turn approximately 200 meters from the end of the runway, the engine experienced a sudden loss of power. As the aircraft's altitude dropped to approximately 40 meters, the crew was forced to abandon the turn and aim for a nearby plowed field to avoid obstacles, including high-voltage power lines.
The aircraft struck the ground in a high-pitch attitude with significant vertical velocity, causing it to bounce before coming to a halt near a tractor. A fire broke out following the impact, and while the aircraft was destroyed, both the pilot and the instructor managed to escape the wreckage. Both occupants sustained serious injuries.
The investigation
The investigation examined the mechanical state of the engine, the aircraft's configuration, and the flight maneuvers performed prior to the impact. Investigators reviewed the maintenance history of the Smaragd CP-301-S, noting it had undergone a 33-hour inspection shortly before the accident.
Technical examination of the wreckage was limited due to the intensity of the post-crash fire, which destroyed the electrical circuits. However, investigators were able to confirm that the engine was still running at the moment of impact and found no evidence of prior defects in the engine or carburetor. The investigation also assessed the flight conditions, noting visibility was good and winds were light.
Findings
- The primary cause of the accident was an engine power loss during the return maneuver.
- The specific origin of the abnormal engine noise and burning smell could not be determined.
- The cause of the subsequent engine deceleration remained unidentified due to the destruction of the engine components by fire.
- The severity of the impact was attributed to the aircraft hitting the ground in a high-pitch attitude with high vertical speed.