What happened
On May 3, 2006, a Robin DR400-180R, registration HB-KOC, was performing a glider towing operation near Bern-Belp airport. Shortly after takeoff, the aircraft experienced irregular engine performance. The crew of the towed glider, an ASK 21, was notified of the engine issues via radio and subsequently performed a controlled landing at the glider field.
The pilot of the HB-KOC attempted an emergency landing west of the airfield. During the approach, the engine power fluctuated before eventually failing completely. While executing a left turn at a very low altitude, the aircraft struck the ground with its left wing, causing the plane to capsize onto its back. An immediate fire broke out at the wreckage site.
Although the pilot survived the initial impact, the aircraft's acrylic canopy became stuck, preventing escape. While bystanders attempted a rescue, the rapidly spreading fire forced them to abandon the effort, and the pilot succumbed to the flames.
The investigation
The investigation examined the technical state of the engine, the cockpit equipment, and the operational procedures in place during the towing mission. Investigators noted that while the engine failure could not be definitively attributed to a specific mechanical fault, the aircraft was equipped with a carburetor type that had shown similar issues on other aircraft.
Crucially, the investigation focused on the survivability of the accident. It was determined that the accident was survivable had the pilot been able to exit the cockpit. The investigation also looked into the communication protocols between the tow plane and the glider, noting that the two aircraft were operating on different radio frequencies, which prevented direct communication between the crews.
Findings
- The primary cause of the crash was the pilot's failure to utilize available emergency landing options following the engine failure, leading to an uncontrolled ground impact and subsequent rollover.
- The fatal outcome was directly linked to the absence of an emergency tool in the cockpit capable of breaking the flexible acrylic canopy.
- A lack of direct communication between the tow plane and the glider occurred because the crews were using different radio frequencies, which prevented the glider crew from relaying critical information to the tow pilot.
Safety action
Following the accident, the Swiss Federal Office of Civil Aviation (FOCA) issued a safety notification recommending the installation of a specialized piercing tool, such as a small hammer or spike, in the cockpits of small aircraft—particularly low-wing models like the Robin DR400—to ensure the canopy can be breached in an emergency.