Events and flight progress
On the day of the accident, the experienced pilot rigged the motorised glider in the morning and took it to the launch site. After a successful winch launch with a flight instructor in a Twin-Astir, he prepared for his first winch launch of the year on the LAK-17B FES mini. Witnesses reported that the pilot went through the checklist aloud in the cockpit before the winch launch began at 14:57.
The take-off was initially normal, but after take-off the aircraft entered a steep climb attitude and suddenly lost control. The motor glider tilted to the right and crashed onto the grass runway about 200 metres from the take-off site. The pilot died at the scene of the accident and the aircraft was completely destroyed.
Pilot details
The 66-year-old pilot had held a permanent glider pilot's licence (LAPL-S) since 1993 as well as other authorisations for various types of take-off, including towing and winch launches. He also held a pilot's licence for air sports equipment operators, including microlight aircraft. His medical certificate was valid until April 2020 and he was required to wear multifocal glasses.
The pilot had extensive flying experience with over 1,700 hours on gliders and around 500 hours on motorised aircraft. However, he had only completed three self-launches on the aircraft type in question and this was his first winch launch on this type.
Aircraft details
The aircraft involved in the accident was a LAK-17B FES mini motorised glider, which was manufactured in Lithuania in 2017. It is a modern aircraft equipped with a front electric sustainer (FES) propulsion system, an electric motor with a folding propeller in the nose of the fuselage. The aircraft was built using hybrid composite materials and had a wingspan of 13.5 metres. The aircraft was registered in Germany and had a provisional permit to fly, which expired the day after the accident.
Course of the accident
The accident occurred during the winch launch. After take-off, the aircraft displayed an unstable flight attitude as it entered a climb attitude that was too steep. Despite the winch operator's instructions to increase speed, the aircraft tipped over the right wing and crashed. The BFU investigation revealed no technical defects in the aircraft that could have caused the accident.
The winch cable used was a steel cable that had not broken, but showed clear signs of heavy strain. The weather conditions on the day of the accident were relatively calm, with a light wind from a north-westerly direction and visibility of 8 kilometres.
Accident site and findings
The aircraft hit the ground about 220 metres from the take-off point. The investigation revealed that the first contact with the ground was with the right wing and the cockpit area. The motorised glider came to rest lying on its upper surface and the front cockpit area was completely destroyed. The wings showed multiple cracks and compressions, the landing gear was extended and the winch cable had detached from the aircraft.
Conclusions and recommendations
During the investigation, the BFU found that the information in the flight manual relating to the winch launch called for a camber during the launch phase, which proved to be problematic, especially with powerful launch winches. This led to a change in the corresponding construction regulations and the flight manual.
Due to these changes, the BFU refrained from issuing further safety recommendations, but emphasised the need for flight manuals to contain clear and precise instructions for the safe operation of aircraft.
This tragic accident emphasises the importance of thorough preparations and close attention to operating regulations, especially with new or unfamiliar aircraft types. The results of the investigation should help to prevent similar accidents in the future and increase safety in air sports.
Source references:
Federal Bureau of Aircraft Accident Investigation