What happened
On June 20, 2010, a Schleicher ASK-21 glider, registration PH-1290, was performing a winch launch from the Castricum glider field. During the ascent, at an altitude of approximately 220 meters, the pilot observed a single-engine aircraft crossing the launch path at a 120-degree heading. To avoid a collision, the pilot decided to terminate the launch, and the winch operator simultaneously reduced power. The pilot estimated the closest distance to the other aircraft was roughly 80 meters.
At the same time, a Tecnam P2002-JF, registration PH-VHA, was conducting an overland flight from Hilversum. The pilot of the Tecnam P2002-JF noticed a glider flying in the opposite direction near the coastline. To maintain separation, the pilot of PH-VHA altered course to the right. While the pilot of the powered aircraft estimated a horizontal separation of over 500 meters, the glider pilot's perspective indicated a much closer encounter.
The investigation
The investigation, based on pilot statements and air traffic control radar data, examined the flight paths and the separation between the two aircraft. The investigation noted that the incident occurred in uncontrolled airspace, where pilots are responsible for maintaining separation through the "see-and-avoid" principle.
It was established that the pilot of PH-VHA was not familiar with the exact location of the Castricum airfield and was navigating using paper charts without the aid of a GPS. The investigation also reviewed the technical parameters of the winch launch, noting that the maximum cable height for this site is 1500 feet, and that winch cables can present a significant visual obstacle to other aircraft.
Findings
- The primary cause of the aborted launch was the encroachment of a powered aircraft into the launch path of the glider.
- The pilot of the Schleicher ASK-21 took decisive action to abort the launch to prevent a collision.
- The pilot of the Tecnam P2002-JF was navigating without GPS assistance and was unfamiliar with the specific location of the glider field.
- The incident occurred in uncontrolled airspace, placing the responsibility for separation entirely on the pilots' ability to see and avoid other traffic.