Introduction
On 21 August 2009, a Robinson R22 Beta helicopter, registration HB-XZN, operated by Airport Helicopter Basel, was involved in an accident during a training flight near Weienbrunnen, in the municipality of Hitzkirch, Canton Lucerne. The flight instructor and a student pilot were on board. No injuries were reported, but the helicopter was heavily damaged.
Flight History
The flight instructor began his workday at approximately 08:00 local time. After completing preparatory tasks, he conducted two introductory flights for prospective students earlier in the day. The student pilot arrived around 16:15 for a scheduled training flight. After a briefing, the crew departed Beromünster airfield at 17:06 for a training area on the Lindenberg. The planned exercises included transitions from hover to forward flight, landings in uneven terrain, steep approaches, and hover maneuvers. The left cockpit door was removed due to high temperatures.
Accident Sequence
During the training session, the instructor took control to allow the student a brief rest and to reposition the helicopter for a hovering autorotation exercise. At point A (see source image), he lifted off, climbed to an altitude of 20-25 m above ground, and flew at 40-50 KIAS along a flat, mown field. He then initiated a left turn towards point B. The instructor reduced power before the turn, intending to increase it during the maneuver with a bank angle of 20-30°. The main rotor rpm was 104% before the turn, and manifold pressure was around 18 inHg.
After about 90° of turn, the instructor felt the helicopter was not responding as expected. He encountered difficulties controlling the yaw axis and noticed an unexpected descent and an increase in bank angle to approximately 45°. He attempted to recover by leveling the helicopter and adding power and forward cyclic, but the manifold pressure exceeded the briefing limit of 24.5 inHg. The rotor rpm remained in the green range until just before ground contact. The low rotor rpm warning horn sounded at about 3 m above ground. The groundspeed decreased to an estimated 5-10 kt during the turn.
The helicopter first contacted the ground with the left skid, followed by the right skid with a loud noise from the forward right side. It then bounced to about 1 m, partially compensated for yaw with pedals, and a third gentle contact on the left skid occurred. The instructor held the helicopter in a hover without fully relieving weight, feeling slight vibrations. He decided not to land to avoid further damage.
Aftermath
Assessing the situation, the instructor noted that the main rotor rpm was in the green range, no warning lights were on, the skid gear was visibly bent, and the helicopter was stable. He checked the emergency locator transmitter (ELT) on 121.5 MHz; it had not activated. The instructor then flew the damaged helicopter back to Beromünster airfield, approximately 10 km away, at reduced speed. He requested assistance via radio. Colleagues prepared a wooden pallet, onto which the instructor landed the helicopter, allowing it to rest with acceptable bank angle.
Probable Cause
The accident was caused by the helicopter's landing gear violently contacting the ground during a poorly executed turn near the ground.