On October 2, 2001, an Eurocopter AS 350 B2 was involved in an aviation accident near Münsingen, DE. This summary draws on records from the German Federal Bureau of Aircraft Accident Investigation (BFU).
On 2 October 2001, a Eurocopter AS 350 B2 crashed at Münsingen while testing a glider rescue system. The helicopter pilot was killed, the aircraft was destroyed, and the glider landed on parachutes.
Overview and context On 2 October 2001, a Eurocopter AS 350 B2 helicopter was destroyed in an accident at Münsingen while participating in a test of a whole-airframe rescue system for a glider. The helicopter pilot was fatally injured. The glider, a Rolladen-Schneider LS3-a, was released from the helicopter and subsequently deployed its rescue system, resulting in a relatively soft landing. Minor ground damage was reported. ## Test objective and setup A German glider manufacturer had been developing a rescue system intended to allow a glider in distress to reach the ground with the pilot largely unharmed. Earlier manned test flights had been completed without incidents. For certification, two final flights were required in which the system would be released in special limiting flight conditions, including at a speed above 200 km/h. Because of the increased risk, these flights were to be conducted unmanned. The LS3-a glider was fitted with a wireless command and telemetry system. It was to be carried inverted by a load harness attached to the helicopter’s load hook and raised to 600 m or 800 m. The load hook was then to be opened, followed shortly by release of the load harness from the glider. The glider was then to be flown remotely into a predetermined condition and the rescue device released. On 1 October, a first test was carried out at the Münsingen military training area. The glider was raised to 600 m and the remainder of the procedure was completed as planned without incident. A second test planned for that day could not be carried out because the training area was closed from 16:00 local time; it was rescheduled for the following day. ## Sequence of events On the morning of 2 October, the test leader first obtained permission from the commandant to use the training area. After the glider had been prepared, the planned test was reviewed. The glider was to be raised to 800 m above ground and then released. To reduce yawing during the load flight, as had occurred the previous day, the forward speed during climb was to be increased. After a pause while the helicopter was not yet on site, telemetry was switched on and the glider was checked using a written checklist. One item was that the coupling was closed. The helicopter then started, hovered over its parking position, and attached the long strap of the load harness to the load hook. It then hovered over the glider and slowly climbed to tension the harness straps. The glider lifted off at 11:27 local time, and the helicopter began climbing on a course of about 300°. The initial phase was uneventful, with the glider hanging calmly beneath the helicopter. Thirteen seconds after lift-off, the right wing line of the glider released. This initially had no effect on the flight. One minute and ten seconds after lift-off, the left wing line released. The glider then began to roll and yaw, at times violently. The test leader on the ground, in radio contact with the pilot, told him there was a small problem and to simply continue climbing. Shortly afterwards, he instructed the helicopter to fly south if possible. As the helicopter turned south, the glider made a violent roll/yaw movement to the right and then to the left. It then settled and hung nearly horizontally for about two seconds. At an altitude of about 480 m above the start point, and about 2.5 minutes after lift-off, the attachment in front of the wheel released. The glider entered a nose-down dive and was then attached only by the rear coupling. The harness strap remained hooked in the helicopter. The stitching of the loop through the shackle failed, and the strap was pulled through the shackle. With no connection remaining between the glider and the helicopter, the part of the load harness still attached to the helicopter snapped upward and wrapped around the rotor mast. Video recordings showed that the helicopter’s strap release had not occurred up to that point. The subsequent descent was nearly vertical. Before impact, the tail boom separated from the helicopter fuselage. Shortly after separation from the helicopter, the rear coupling on the glider opened, the harness strap detached from the glider, and the rescue system was released. The glider landed relatively softly on its parachutes. Several members of the test team stated that the test leader had instructed the pilot to “release the helicopter” shortly before the accident. This instruction could not be confirmed from the available video recordings. ## Aircraft and personnel The helicopter was a Eurocopter AS 350 B2, manufactured by Eurocopter France and certified in the passenger transport 3/air work category. Its total operating time was 2,728 hours and it had made 5,572 landings. Its maximum takeoff weight without external load was 2,254 kg; with an external load, the maximum allowable external load was 1,160 kg and the maximum takeoff weight was 2,500 kg. It was equipped with a Breeze-Eastern Corporation Cargo Release Assembly 14027-7. The load hook was normally released electrically and could be released mechanically in an emergency. A load indicator was installed in the instrument panel. The takeoff weight, including external load but excluding air forces, was 1,994 kg, with the centre of gravity 3.399 m from the reference point. The next major inspection was due in March 2002. The glider was a Rolladen-Schneider LS3-a, modified for the tests and given a provisional airworthiness certificate as a model aircraft by the Luftfahrt-Bundesamt (LBA). The modification included the whole-airframe rescue system, a telemetry system, and four attachment points for the load harness. Couplings of type E 72 from Tost were installed in the fuselage in front of the main wheel and at the rear, and hooks were fitted on the wings. The main load was carried by the coupling in front of the main wheel; the wing attachment points were intended to keep the glider level. The coupling in front of the main wheel, serial number 18713, had been manufactured by Tost on 15 December 1972 and had been removed from a Standard Libelle glider in Switzerland in 2001 after 1,019 starts since manufacture. Its maximum allowable rope load was 1,170 dN. The glider’s mass was 410 kg. The load harness consisted of elastic webbing. A 25 m strap with a steel ring was hooked into the helicopter’s load hook; its other end ended at a shackle. A further strap was threaded through this shackle and hooked into the two Tost couplings on the glider via double ring pairs. A loop threaded through the shackle and sewn to the strap secured it. Two additional straps were attached to the shackle and hooked into the wing hooks, which were secured with rubber. A small parachute of about 2 m diameter was also hooked into the helicopter in a pack; the parachute itself was attached to the end of the 25 m strap. The load harness was manufactured by MVEN of Kazan, Russia, on the test leader’s order. MVEN was also significantly involved in the development of the whole-airframe rescue system. No aviation construction regulations applied to the manufacture of such a load harness, and such designs were not subject to aviation-law inspection or approval. The helicopter pilot held a professional helicopter pilot licence valid until 16 January 2003. His total flying experience was about 12,000 hours. In the 90 days before the accident, he had made 190 takeoffs and landings in the accident type. He was reported to have extensive experience with external-load flights.