What happened
On July 8, 2023, an ASK 23 B single-seat glider was performing a winch launch from Noordkop glider airfield. The pilot, who was on his 25th solo flight and did not yet hold a Sailplane Pilot Licence, was being lifted toward the end of the launch sequence. Near the end of the ascent, the pilot observed a motorized aircraft, a Van’s RV-9A (registration F-PDAD), at a 10 o'clock position. The motorized aircraft was flying at approximately 1,275 feet, heading toward the winch path.
To avoid a collision, the pilot pushed the control stick forward to level the glider and released the winch cable earlier than planned. The vertical separation between the two aircraft was estimated to be less than 50 metres. The pilot of the Van’s RV-9A was flying a VFR route from Texel International Airport to Belgium and reported that he did not see the glider, as he had assumed no gliding activity was occurring due to a lack of thermals.
The investigation
The Dutch Safety Board examined the flight paths and the effectiveness of collision avoidance technology. The investigation noted that the ASK 23 B was equipped with a FLARM system, yet the system provided no warning of the approaching aircraft. The investigation also reviewed the pilot's use of the SkyDemon navigation software and the SafeSky application, which also failed to indicate any nearby gliding activity.
Findings
- The near-collision occurred in uncontrolled Class G airspace, where pilots are responsible for maintaining their own separation.
- The proximity of the Noordkop airfield to the busy Wadden Sea Corridor increases the frequency of encounters between gliders and motorized traffic.
- The FLARM collision avoidance system failed to provide a warning despite the close proximity of the two aircraft.
- The pilot of the motorized aircraft was relying on visual scanning and software that did not indicate the presence of the glider.