What happened
On 2 August 2016, a Breezer B600E, registration D-ETDK, was operating as the final aircraft in a group of eight flying in loose formation. The group was en route from Glenforsa Airfield to Oban Airport for refueling. To maintain separation from the aircraft ahead and follow the group's landing plan, the pilot reduced the aircraft's speed.
While flying near a ridge northwest of Oban Airport, the aircraft encountered an updraught caused by wind flowing over the terrain. This sudden change in airflow led to an aerodynamic stall. The pilot attempted to deploy the ballistic recovery system (BRS) at approximately 770 feet, but the aircraft was unable to achieve a stable descent before impacting the ground. The accident resulted in two serious injuries to the pilot and passenger, and the aircraft was destroyed.
The investigation
The AAIB examined the aircraft's flight data, the wreckage, and the weather conditions at the time of the accident. Investigators found that the aircraft was flying at a low airspeed, approximately 32 to 45 knots, with flaps extended. The investigation also reviewed the weight and balance of the aircraft, noting a significant discrepancy in the weight of the baggage on board. While the pilot reported 30 kg of baggage, investigators recovered 50 kg of items from the wreckage.
Furthermore, the investigation looked into the communication between the formation leader and the Flight Information Service Officer (FISO) at Oban. It was noted that there was a misunderstanding regarding the required separation between arriving aircraft, which influenced the pilot's decision to slow down to maintain spacing within the formation.
Findings
- The aircraft encountered an updraught caused by wind flowing over a nearby ridge.
- The stall and loss of control were exacerbated by the aircraft's low inertia, making it highly susceptible to turbulence.
- The aircraft's Centre of Gravity (CG) was likely behind the aft limit due to the heavy and improperly distributed baggage.
- The pilot had reduced the aircraft's speed to maintain separation from the preceding aircraft in the formation.
- The BRS was activated at too low an altitude to allow for a stabilized descent before impact.