What happened
On 28 November 2001, at Stockholm/Arlanda airport, a Beech 300LW (registration SE-KOL) was conducting calibration flights to test new ground radar equipment. The flight, operating under the call sign CBN 12, was performing a series of takeoffs and landings on the airport's new runway.
During the sequence, the air traffic controller notified the crew that a departure was pending on runway 08 and stated she would provide further instructions later. While the controller was managing the departure of a SAAB SF340A (registration SE-ISV), the pilots of SE-KOL initiated their takeoff from runway 01R. This maneuver occurred without the crew having received an explicit takeoff clearance from the tower.
As the SE-KOL climbed, it entered the flight path of the departing SE-ISV. The two aircraft reached a minimum separation of approximately 425 meters laterally and 700 feet vertically. The crew of the SE-ISV reported a TCAS warning during the encounter. The pilots of SE-KOL maintained visual contact with the other aircraft, and no collision occurred.
The investigation
The Swedish Accident Investigation Authority (SHK) examined the radio communications, radar data, and operational procedures at the airport. The investigation focused on the coordination between the tower and the calibration flight, as well as the specific instructions provided by the controller. The inquiry also looked into the established routines for flights operating outside the standard maneuvering areas during radar testing.
Findings
- The primary cause of the incident was the pilots of SE-KOL taking off without receiving takeoff clearance.
- The air traffic controller used non-standard phraseology when issuing instructions, which contributed to the confusion.
- There was a lack of formal briefing between the air traffic controller and the calibration flight crew prior to the operations.
- Inadequate operational routines existed for managing aircraft performing unusual flight profiles, such as calibration tasks, outside of established maneuvering areas.
- Uncertainty regarding standard procedures and phraseology for operations outside the maneuvering area was present among pilots.