What happened
On July 31, 2006, at approximately 12:45 local time, a mid-air collision risk occurred near Almere-HDaven, Netherlands. An MBB BO-105C helicopter, registration PH-RPW, was conducting an Airborne Video System (ABVS) training flight. After receiving clearance from Schiphol Approach to climb from 500 to 2000 feet AMSL, the helicopter began its ascent at a rate of 500 feet per minute.
During this climb, a Cessna 172M, registration OO-WIU, approached the helicopter from behind at a higher speed. The Cessna was performing a VFR overland flight from Antwerp to Norderney. As the helicopter reached 1200 feet AMSL, the pilot of the PH-RPW observed the Cessna passing directly overhead. The vertical separation between the two aircraft was estimated to be only between 50 and 100 feet, with the Cessna traveling at approximately 120 KIAS.
The investigation
The investigation focused on why the pilots failed to perform an avoidance maneuver and why air traffic services did not provide warning. Investigators examined the flight paths, the visibility conditions, and the communication between the pilots and various flight information services.
It was established that while the helicopter was in contact with Schiphol Approach, the Cessna was communicating with Dutch Mil Info. Because the Cessna was not in contact with Amsterdam FIC, no traffic information regarding its presence was coordinated between the two services. Furthermore, the investigation looked into the use of transponder equipment in the Schiphel TMA 1 airspace.
Findings
- The primary cause of the incident was the failure of the see-and-avoid principle due to the flight paths of both aircraft placing the other in a blind spot.
- The vertical separation between the MBB BO-105C and the Cessna 172M was critically low, estimated at only 50 to 100 feet.
- The pilot of the OO-WIU had the transponder set to standby to comply with AIP Netherlands regulations for the Schiphol TMA 1, which rendered the aircraft invisible to secondary radar.
- There was a lack of coordination between Amsterdam FIC and Dutch Mil Info regarding the presence of the Cessna in the area.
Safety action
- The Safety Board recommended that the Inspectie Verkeer en Waterstaat reconsider the regulation that allows pilots to fly without an active transponder within the Schiphol TMA 1.