What happened
On 22 July 2001, a Wassmer WA 40, registration OY-DHV, was conducting a private flight from Perigueux, France, to Peterborough, UK. After an earlier delay in the journey, the pilot was navigating toward the Southampton VOR when the aircraft encountered a bank of cloud. Upon entering the cloud, the pilot lost visual flight rules (VFR) conditions and requested flight information service from Farnborough Radar.
While communicating with air traffic control, the pilot reported descending through the cloud. Shortly thereafter, a distress call was received stating that the pilot had lost control of the aircraft and that a crash landing was imminent. Witnesses on the ground observed the aircraft emerging from the cloud base in a spinning motion, appearing to have lost a wing. The aircraft struck the ground and caught fire, resulting in one fatality.
The investigation
The AAIB examination of the wreckage, which was spread over approximately one kilometre, revealed that the aircraft had undergone multiple structural failures in flight. While the steel engine and fuselage attachments remained intact following the impact, the wooden components of the wings and tail surfaces had fragmented significantly.
Investigators analyzed the distribution of debris and determined that the primary structural failures occurred at an altitude of more than 1,000 feet. Specialist examination of the wooden airframe identified areas of debonding in the torsion box and the rear spar of the fin, likely caused by moisture ingress into the ureaformaldehyde resin. Additionally, the investigation noted that the aircraft had previously experienced severe weather, including a lightning strike and heavy thunderstorms, during its journey earlier that month.
Findings
- The aircraft suffered a complex in-flight breakup at speeds likely exceeding normal cruising velocity.
- Structural failure of the right wing is considered the primary driver of the subsequent loss of control and tail surface disintegration.
- The aircraft's wooden components showed evidence of moisture-related degradation and debonding in critical areas.
- The pilot, who lacked instrument flying qualifications, was attempting to navigate through cloud cover without visual references.
- Previous high-load events or environmental exposure may have weakened the structural integrity of the wooden assemblies, making them susceptible to the stresses of the final flight.