What happened
On July 14, 2005, a training flight involving an instructor and a student in a Piper PS-28R-200, registration PH-SDN, was en route from Groningen Airport Eelde to Teuge Airport. The flight was operating under instrument flight rules (IFR) at flight level 402. Simultaneously, another Piper PS-28R-200, registration PH-BVE, was conducting a visual flight rules (VFR) overland flight from Rotterdam toward Eelde, descending from flight level 65 toward 1,500 feet.
At approximately 15:08 local time, air traffic controllers notified the crew of PH-SDN of oncoming VFR traffic at a distance of 5 nautical miles. The crew of PH-SDN clarified they were flying in instrument meteorological conditions (IMC). Meanwhile, the crew of PH-BVE had been informed of traffic at the one o'clock position. Although the pilot of PH-BVE attempted a right turn to increase separation, the aircraft was not initially sighted. By 15:10, the crew of PH-SDN reported a near-collision, noting that the other aircraft passed just above and to the right with a vertical separation of only about 30 meters.
The investigation
The investigation examined the separation responsibilities within the Nieuw Milligen Terminal Control Area (TMA) B, which is classified as ICAO Class E airspace. In this airspace, air traffic controllers manage IFR traffic on one frequency, while providing traffic information to VFR traffic on a separate frequency. The investigation relied on radar analysis and written statements from the pilots.
Investigators analyzed the meteorological conditions provided by the KNMI, which indicated cumulus clouds with bases at 3,000 feet and tops at 4,000 feet. The investigation also scrutinized the separation duties of the two controllers, noting that in Class E airspace, separation between IFR and VFR traffic is the responsibility of the pilots via the "see-and-avoid" principle, rather than the air traffic controller.
Findings
- The use of two different controllers on two different frequencies meant the crews of PH-SDN and PH-BVE were unaware of each other's specific intentions.
- While the pilot of PH-BVE reported being in visual meteorological conditions (VMC), the investigation found it likely that the pilot was not adhering to VFR weather minima, as the presence of clouds likely prevented the required vertical and horizontal clearance from cloud layers.
- The pilot of PH-BVE failed to visually identify the oncoming aircraft despite having an optimal view during descent.
- Radar data could not confirm the pilot's claim of a right turn; notably, a right turn toward oncoming traffic would actually decrease lateral separation and increase collision risk.