What happened
On 2 August 2007, a Fokker F27 Mark 050, registration PH-KVC, was performing a scheduled passenger flight from Amsterdam Schiphol to Maastricht Aachen Airport. While on an ILS approach to runway 21, the crew encountered a potential collision with a T-6J Harvard Mark IV, registration D-FUKK, which was conducting a cross-country flight.
The pilot of the D-FUKK had requested permission to cross the Maastricht control zone. During the communication, the air traffic controller struggled to identify the aircraft's registration due to radio noise and incorrectly recorded the call sign as H-F לוKK. Because this incorrect registration did not exist in the flight database, the controller manually entered the flight plan. Due to the audio quality and the pilot's mention of the aircraft type, the controller mistakenly categorized the flight as a helicopter.
As the two aircraft approached, they came within approximately 0.14 NM of each other at nearly the same altitude. The crew of PH-KVC received a TCAS traffic alert, though the resolution advisory was suppressed because the aircraft was flying below 1000 feet. Despite the proximity, the Fokker F27 continued its approach and landed safely.
The investigation
Investigators examined the communication between Maastricht Approach and Tower, as well as the weather conditions at the time of the incident. The investigation focused on why separation was not maintained despite instructions given to the pilot of the D-FUKK to remain east of the airfield.
Analysis of the radar data and flight logs revealed that the weather conditions were marginal. While the conditions met the requirements for a Special VFR flight for a helicopter, they did not meet the legal requirements for a fixed-wing aircraft, as cloud ceilings were below 600 feet. Furthermore, the investigation found that the D-FUKK was operating below its cleared altitude of 1200 feet during the encounter.
Findings
- The primary cause of the incident was the misidentification of the aircraft type, which led the controller to believe the flight was a helicopter.
- Because the aircraft was treated as a helicopter, the controller applied incorrect Special VFR regulations and failed to account for the different speed and maneuverability characteristics of a fixed-wing aircraft.
- Poor radio signal quality and background noise prevented the controller from correctly identifying the registration D-FUKK.
- Marginal weather conditions and low cloud ceilings prevented the pilot of the D-FUKK from maintaining sufficient visual references to the airfield and the approaching PH-KVC.
- The pilot of the D-FUKK was operating below the authorized altitude of 1200 feet.