What happened
On November 7, 2007, at 20:23 UTC, a Pegasus Airlines charter flight, TC-AAP, a Boeing 737-800, was approaching Pori Airport from Copenhagen. At the time of the approach, a maintenance vehicle was active on the runway, measuring the Runway Visual Range (RVR) by counting runway lights.
The air traffic controller (ATC) informed the flight crew that the RVR was below the required landing minimums and instructed the aircraft to enter a holding pattern. However, a significant misunderstanding occurred: the pilots believed they were permitted to continue the ILS approach down to the Decision Altitude (DA).
As the aircraft continued the approach, the maintenance vehicle attempted to clear the runway. While the driver moved quickly, the vehicle was still partially within the runway markings as the aircraft passed. Estimates suggest the distance between the aircraft's wingtip and the vehicle was approximately 15 meters. The flight crew eventually initiated a go-around at the minimum altitude, noting they had seen the approach lights, but the incident had already created a severe collision hazard.
The investigation
The investigation examined radio communications, flight data, and the actions of both the air traffic controller and the flight crew. The inquiry focused on the discrepancy between the ATC's instructions and the pilots' interpretation of the RVR limitations. The investigation also reviewed the timing of the incident reporting, noting that the controller did not notify regional ATC until after the aircraft had departed, which resulted in the loss of some investigative material and delayed interviews with the crew.
Findings
- The primary cause of the near-collision was that the pilots conducted the approach without receiving or acknowledging the required ATC clearance.
- The pilots violated established regulations by continuing the approach while the reported RVR was below the legal minimums.
- There were significant deficiencies and ambiguities in the radio communications between the ATC and the flight crew, including unclear speech that was difficult to interpret.
- A critical misunderstanding existed regarding terminology: the controller believed the pilots' mention of "minimums" referred to the minimum holding altitude, while the pilots were referring to the ILS decision altitude.
- The air traffic controller instructed the maintenance vehicle to vacate the runway but failed to issue a formal go-around instruction to the aircraft.