What happened
On April 23, 2021, a Robin DR40, registration HB-KOW, was approaching Bern-Belp (LSZB) for landing. Due to prevailing wind conditions, the pilot incorrectly assumed that runway 32 was the active runway, despite the airport information indicating runway 14 was in use.
While the pilot of HB-KOW was navigating the airspace, a Cessna 172, registration HB-CWE, was conducting a flight training session on the active runway 14. The pilot of the Robin DR40 performed a full circle after passing waypoint W1, likely believing their clearance ended at that point. As the HB-KOW transitioned into a downwind pattern, it entered the path of the Cessna 172 flying on the opposite side of the airfield.
At approximately 09:02 UTC, the two aircraft reached a minimum separation of 0.7 NM horizontally and 100 ft vertically. The air traffic controller observed the error and immediately instructed the pilot of HB-KOW to turn right to join the correct left-hand downwind for runway 14. However, the pilot's incorrect mental model persisted, and they briefly entered the left-hand downwind for the wrong runway (runway 32) before eventually correcting the course following further instructions.
The investigation
The investigation examined radio communications, radar data, and statements from the air traffic controller and the flight crews involved. The inquiry focused on why the pilot of HB-KOW failed to follow the instructed arrival procedure and why the instruction from the controller was interpreted incorrectly by the pilot.
Findings
- The pilot of HB-KOW operated under a false expectation that the airport was being approached from the southeast to the northwest, which aligned with runway 32 rather than the active runway 14.
- This mental error was likely reinforced by the wind conditions, causing the pilot to disregard the current ATIS information.
- The pilot's misunderstanding of the clearance led to an unintended full circle flight pattern.
- The air traffic controller's use of the word "wrong" in the instruction "You are on the wrong downwind" was ambiguous; the pilot interpreted this as being on the wrong side of the pattern (right-hand instead of left-hand) rather than on the wrong runway entirely.
Safety action
- The investigation noted that runway direction confusion occurs approximately once a year at this airfield.
- It was suggested that controllers should use more specific references, such as explicitly stating the runway number, to avoid ambiguity when correcting a pilot's flight path.