Accident Overview
On 18 June 2008, at approximately 16:48 local time, a Eurocopter AS350 B2 helicopter, registered as HB-XVB, was involved in an accident at Grenchen Regional Airport in Grenchen, Switzerland. The helicopter, operated by Heliswiss Schweizerische Helikopter AG, was on a private visual flight rules (VFR) flight. The pilot, a Swiss citizen born in 1960, held a private pilot license for helicopters (PPL(H)) issued on 4 January 1993, with a type rating for the AS350/350B3 valid until 30 October 2008 and an external landing authorization valid until 8 September 2008. His medical certificate was Class 2 with no restrictions. He had logged 304 hours 48 minutes total flight time, with 81 hours 30 minutes on the accident type, and 4 hours 22 minutes in the last 90 days. The helicopter sustained substantial damage. Light damage occurred to nearby aircraft, and minor ground damage was reported.
Flight History
Earlier on the morning of 18 June 2008, the pilot completed a training flight of 1 hour 35 minutes with an instructor, which included a landing at one of the helicopter landing pads at Grenchen. Subsequently, he conducted three private flights totaling about 1 hour 15 minutes without an instructor, ending at an industrial zone near the southeastern edge of Grenchen, close to the control zone boundary.
Accident Flight
Around 16:30, the pilot restarted the helicopter to return alone to Bern, after which he planned to drive to his home in Zurich. During departure, the low fuel warning illuminated when approximately 60 liters remained, indicating about 18 minutes of flight time according to the aircraft flight manual. Judging this insufficient for the flight to Bern, the pilot decided to land at Grenchen for refueling.
He informed the air traffic control at Grenchen of his intention and received clearance to approach grass runway 07 Left via left-hand downwind. While the helicopter was on approach, a mobile platform was positioned on helicopter landing pad H1, intended for landing to allow towing to the fueling station. This procedure was standard at Grenchen for helicopters without wheeled landing gear, requiring prior permission (PPR) as per the Swiss AIP. The pilot was unaware of this procedure.
The controller instructed the pilot to continue approach to grass runway 07L, land, and then hover to pad H1 and land on the platform. The pilot acknowledged. After landing on the grass strip, the pilot hovered via taxiway N, passed the helicopter pads, and headed to a grassy area north of them. The controller then firmly instructed the pilot to land on the platform at pad H1, switching to Swiss German to clarify the exact location. The pilot changed direction and approached the mobile platform.
Landing and Accident
While descending over the platform, the pilot monitored the position of the landing skids using a mirror attached to the right skid tip, aiming for a clearance of 20 to 30 cm between the right skid and the platform edge. Video evidence showed the previously smooth control inputs becoming somewhat erratic just before touchdown. The pilot made a small right correction and then descended nearly vertically with relatively high sink rate, primarily watching the right-side mirror.
The helicopter first contacted the platform with the rear part of the right landing skid. The longitudinal axis of the helicopter was rotated approximately 4° to the right relative to the platform's longitudinal edges. During this maneuver, control was lost, and the helicopter overturned.
Injuries and Damage
The pilot, the sole occupant, sustained light injuries. The helicopter was substantially damaged. Light damage occurred to other aircraft in the vicinity, and minor ground damage was noted.
Cause and Contributing Factors
The accident was due to loss of control during landing on a mobile platform, resulting in the helicopter overturning. Contributing factors included inadequate fuel planning, a refueling procedure that required landing on a platform, the pilot's limited recent training in platform landings, and time pressure.