What happened
On October 17, 2009, a Grob Astir CS glider, registration PH-1236, was performing a local flight at Terlet Airfield under the supervision of an instructor. The flight, conducted by a student pilot, began with a winch launch from runway 04C. While the initial portion of the flight proceeded without incident, the aircraft encountered significant weather challenges during the approach phase.
As the pilot entered the circuit for runway 04C, the aircraft transitioned from a downwind leg to a crosswind leg. During this maneuver, a powerful headwind significantly reduced the aircraft's ground speed. Realizing that the remaining altitude was insufficient to complete the standard circuit, the pilot attempted to divert toward the nearest suitable landing area. However, this decision was made too late, and the glider lacked the necessary height to clear a line of trees positioned just before the landing site.
The aircraft struck the trees and became lodged among the branches. The pilot was successfully extricated from the cockpit by the fire department without no injuries. The aircraft sustained significant damage to both wings, the fuselage, and the canopy.
The investigation
The investigation was based on written statements provided by the student pilot and the instructor, alongside meteorological data from the KNMI. The inquiry examined the flight path, the pilot's experience, and the prevailing wind conditions at the time of the accident.
Findings
- The primary cause of the accident was the pilot's inability to clear a tree line due to a loss of altitude caused by strong headwinds.
- High wind speeds at altitude, recorded at 25 knots from 010 degrees at 500 feet, contributed to the rapid depletion of altitude during the crosswind leg.
- The decision to deviate from the standard circuit to a closer landing area was initiated too late to avoid the obstacle.