Accident Overview
On 29 July 1987, a Pilatus PC-6/B2-H2 registered as HB-FIM was involved in a parachute operation near Grenchen, Switzerland. The aircraft was rented after the club's own aircraft became unavailable. On its 17th flight, it was to drop seven parachutists in two passes at 1000 m above ground over the airfield.
Sequence of Events
The first pass involved three jumpers: a student with freefall, a first-time jumper with automatic activation (static line), and another student with automatic activation. The second pass would have included four more jumpers. The jumpmaster, a trainee instructor, directed the operation.
After takeoff at 1530 local time from runway 25, the pilot flew a left turn to the drop heading of 250 degrees. At drop altitude, the jumpmaster opened the sliding door, asked the pilot to reduce power, and signaled the first jumper to exit. Immediately after the first jumper left, the jumpmaster noticed that the outer pack of the next jumper (R.H., the first-time jumper) was open, with part of the parachute already in the airstream. He then quickly pushed that jumper out of the aircraft.
Shortly after, the jumpmaster heard a bang and, leaning out, saw that the horizontal stabilizer was damaged. The right stabilizer edge plate was bent outward. The pilot reported noticeable resistance in the control stick. All remaining jumpers exited without further incident and landed safely near Grenchen.
Pilot's Attempt to Control
The pilot attempted to return to the airfield but found the aircraft uncontrollable due to a forward shift in center of gravity after the jumpers left. He reported drastic pitch oscillations and high sink rates. After three cycles of sudden pitching, he abandoned the aircraft at about 300 m above ground, using his reserve parachute. The aircraft crashed approximately 2 km west of Grenchen airport, destroying it.
Findings and Cause
Investigation revealed that the first jumper likely stepped on the static line of the second jumper while exiting, causing the parachute to deploy prematurely inside the cabin. The parachute canopy momentarily snagged on the horizontal stabilizer, bending the edge plate and partially tearing the stabilizer attachment. This misaligned the elevator, restricting its movement.
The official cause is attributed to inappropriate routing of the static line in the cabin and damage to the horizontal stabilizer by parachute components.