What happened
In 2001, three serious aviation incidents involving aircraft or tow cables occurred within the uncontrolled airspace of the Netherlands. The first incident took place on May 13 at Hoogeveen airport, involving a PH-VHB aircraft. The second occurred near Hoogeveen on August 18, involving a collision risk between a PH-952 and a tow aircraft. The third incident occurred at the Terlet glider airfield on June 13, involving a conflict between a PH-1193 and a PH-1224.
During the Terlet incident, the pilot of the PH-1193 deviated from standard circuit procedures following a go-around. This maneuver placed the aircraft in the path of the PH-1224. Although the pilot of the PH-1193 attempted to draw attention via radio and flight maneuvers, the pilot of the PH-1224 failed to execute an avoidance maneuver after spotting the aircraft.
The investigation
The Dutch Safety Board (OVV) examined the circumstances surrounding these three events, focusing on the effectiveness of the 'see-and-avoid' principle. The investigation looked into pilot procedures, radio usage, and the physical limitations of human vision. The board also reviewed the operational environment at uncontrolled airfields, including the role of ground personnel and the use of radio communications for position reporting.
Findings
All three incidents were caused by the failure of the see-and-avoid concept to prevent potential collisions. Several contributing factors were identified across the different events:
- At Hoogeveen, the tow aircraft deviated from standard circuit procedures, and the pilot of the PH-VHB failed to utilize radio communications effectively.
- In the incident near Hoogeveen, the tow pilot lacked sufficient awareness of collision risks, while the pilot of the PH-952 may have been distracted by a passenger.
- At Terlet, the deviation from circuit procedures by the PH-1193 was a primary driver. Additional issues included the lack of a ground safety official (DDI) to manage the airfield, insufficient radio use by the PH-1193, and the failure of the PH-1224 pilot to take evasive action.
Safety action
To mitigate these risks, the Board issued several recommendations:
- The Minister of Transport and Water Management and the Joint Aviation Authorities should ensure that the inherent limitations of the see-and-avoid concept are addressed deeply within pilot training programs.
- The use of onboard radios for position reporting in uncontrolled circuit areas should be actively promoted to increase aircraft detectability.
- The Royal Dutch Aeronautical Association (KNVvL) was advised to remind users of the correct application of tow cable break links for specific glider types.