What happened
On June 16, 1973, a private Mooney Mk 20A, registration HB-DUL, was conducting a VFR pleasure flight near the Franches-Montagnes region with three occupants. During the flight, a passenger requested that the cabin ventilation be opened due to feelings of oppression. Shortly after, the occupants noticed unpleasant odors and smoke entering the cockpit. Believing an onboard fire had ignited, the pilot initiated an emergency descent toward the Les Eplatures airfield.
During the approach, the pilot mistakenly targeted a runway direction inconsistent with the active runway in use. The aircraft crossed the runway threshold at an excessive speed and low altitude. While attempting to land, the pilot applied full power just before the end of the runway, leading to a bounced landing and a collapsed landing gear. The aircraft continued to taxi, eventually striking a garden wall and a shed, which resulted in the total destruction of the aircraft.
The investigation
Investigators examined the aircraft's electrical, exhaust, and ventilation systems, finding no evidence of internal malfunctions, leaks, or fire. Blood analysis of the pilot ruled out carbon monoxide poisoning. While the pilot's footwear showed signs of chemical degradation, forensic analysis confirmed this was caused by contact with battery electrolyte following the impact, rather than in-flight toxic fumes.
To identify the source of the perceived smoke, the investigation looked at the flight path, which passed near a local landfill and incineration plant. Experimental reconstructions demonstrated that opening the ventilation while flying over a landfill where waste is being burned can introduce unpleasant odors and smoke into the cabin, mimicking the appearance of an aircraft fire.
Findings
- The pilot's decision to perform an emergency landing was driven by panic following the passenger's distress.
- The approach was characterized by excessive landing speed and an incorrect assessment of runway distance.
- The pilot failed to execute a timely go-around after the initial bounce.
- The pilot demonstrated an insufficient ability to manage an unexpected in-flight situation.