What happened
On July 15, 2017, a Robin DR400/180R, registration HB-KFK, was performing glider towing operations near Bern Airport. After completing several successful towing cycles, the pilot began the return approach to the glider strip. During the approach, the pilot observed a glider, registration HB-1766, on the final approach path.
To avoid overtaking the slower glider, the pilot decided to execute a left-hand orbit at a low altitude. The aircraft was flying at approximately 1,900 feet AMSL, roughly 70 meters above the ground, with a speed of about 116 km/h. During the execution of this tight turn, the bank angle increased sharply from 40 to 60 degrees, and the aircraft entered a rapid descent. The aircraft subsequently struck an obstacle, causing the destruction of the airframe and damage to a nearby house roof. The pilot sustained one serious injury.
The investigation
SUST examined the flight paths of both aircraft, radio communications, and the pilot's actions. The investigation focused on the pilot's decision-making regarding the approach and the specific airspace agreements in effect at the time. Investigators also reviewed the functionality of the aircraft's cockpit equipment and the pilot's training history regarding go-around procedures.
Findings
- The primary cause of the accident was the pilot losing control of the aircraft during a tight, low-altitude turn.
- The pilot's decision to perform a low-altitude orbit to maintain separation from the preceding glider was a causal factor.
- The pilot's approach required high mental workload, which hindered effective airspace observation.
- A lack of recent training in go-around procedures contributed to the decision to attempt the orbit rather than executing a standard go-around.
- The FLARM collision warning system was not properly integrated and had been switched off by the pilot, preventing an alert regarding the preceding glider.
- A specific airspace agreement between Bern Air Traffic Control and the Bern Glider Group meant that no traffic information regarding the glider was provided to the pilot of HB-KFK.
- This agreement was subject to widespread misinterpretation among pilots, creating a false sense of security regarding traffic separation.
Safety action
SUST issued a safety recommendation for the Swiss Federal Office of Civil Aviation (FOCA) to review the effectiveness of the glider agreement in the Bern Control Zone to ensure it can be managed safely. Additionally, a safety notice was issued to light aircraft pilots emphasizing the importance of regular training in go-around procedures.