What happened
On November 10, 2011, a Piper PA-31 Navajo, registered HB-LOT, departed from Ecuvillens airfield for a private flight. Shortly after takeoff, the aircraft entered a slight right turn and failed to gain significant altitude. During the climb, an unusual engine noise was noted by a nearby witness. The aircraft then struck the southern edge of a forest northeast of Cottens, causing significant damage to the wings, tail, and engine cowlings. The impact ruptured the fuel tanks, triggering a fire. Despite the damage, the aircraft climbed back above the treeline but subsequently struck high-voltage power lines before crashing into a field, where the wreckage was destroyed by fire. The pilot sustained fatal injuries.
The investigation
Investigators examined the aircraft's mechanical condition and the environmental factors present at the time of the accident. Technical inspections of the engines revealed a defective capacitor in the left engine's right magneto and impurities found downstream of the filter in the right engine's fuel injection system. The investigation also reviewed the pilot's flight plan, which intended for a VFR arrival in Geneva, and the meteorological conditions, which featured a low stratus cloud layer with a base only 70 meters above the runway.
Findings
- The pilot initiated a takeoff under weather conditions that did not permit VFR flight, as visibility was approximately 1.5 km and the cloud base was extremely low.
- The flight profile was inadequate for the intended goal of penetrating the stratus layer, as the aircraft remained beneath the clouds for much of the initial climb.
- Intermittent engine irregularities likely diverted the pilot's attention toward engine instruments and away from maintaining the flight path.
- The process of retracting flaps and adjusting power following a short-field takeoff may have contributed to a momentary loss of altitude and flight path monitoring.
- Low-contrast lighting due to gray, diffuse skies likely hindered the pilot's ability to perceive the aircraft's attitude.