What happened
On July 27, 1964, a De Havilland DH-60G Moth Major, registration HB-UPE, departed from the Courtelary airfield to perform a glider towing operation. During the flight, the pilot observed rapidly deteriorating weather conditions caused by an approaching storm front. To avoid the worsening weather, the pilot released the glider and initiated an immediate return to the airfield.
Upon preparing for landing, the pilot noted that the wind direction had shifted approximately 20 to 30 degrees south from its original alignment with runway 24. The aircraft landed at approximately 17:28, roughly 80 meters past the runway threshold. Shortly after touchdown, while the aircraft was still taxiing, a violent wind gust lifted the left wing, causing the lower right wing to strike the ground. This impact caused the aircraft to veer right and the tail to lift, resulting in the plane slowly capsizing onto its back.
The investigation
The investigation examined the meteorological conditions at the time of the accident, noting that a cold front was moving through the region, bringing highly unstable and stormy weather. At the time of the aircraft's passage, winds were recorded at approximately 10 knots from 230 degrees, with gusts reaching up to 36 knots from directions between 160 and 200 degrees. The investigation also reviewed the pilot's actions, noting that the decision to terminate the flight early due to the weather was appropriate.
Findings
- The aircraft sustained significant damage, including a broken propeller, a dented engine cowling, and damage to the left upper wing, with repair costs estimated at 30% of the aircraft's value.
- There were no injuries to the pilot or any other persons.
- The primary cause of the accident was a strong wind gust that lifted the aircraft and overturned it while it was still on the runway surface.