What happened
On February 15, 2004, a Pilatus Porter PC6T, registration HB-FLK, operating a private skydiving flight from Grenchen, came dangerously close to a De Havilland DHC-8-314 (registration D-BHOQ). The Dash 8, operating flight DLH8AY for Augsburg Airways on behalf of Lufthansa, was on an instrument approach to Bern.
After departing Grenchen, the pilot of the HB-FLK requested a climb to flight level 140. Due to cloud cover, the Bern Tower/Approach controller restricted the aircraft to a maximum altitude of 5,000 feet. However, as the aircraft turned toward its climbing sector, the pilot continued the ascent despite multiple warnings from air traffic control. At the same time, the Dash 8 was descending through 7,000 feet toward 6,000 feet.
Radar tracking confirmed that the two aircraft passed each other with a horizontal separation of only 1.8 nautical miles and a vertical separation of just 40 and 100 feet at different intervals. The pilots of the Dash 8 reported seeing the Pilatus Porter, and their TCAS provided a Traffic Advisory, though no Resolution Advisory was issued.
The investigation
The investigation examined the communications between the aircraft and Bern Tower/Approach. It was noted that at the time of the incident, the Tower and Approach functions were consolidated into a single workstation, manned by a trainee controller under the supervision of a licensed controller.
Investigators found that the controller issued three separate instructions to the HB-FLK pilot to maintain 5,000 feet due to the presence of IFR traffic above. The investigation also noted that the air traffic controllers were not informed that skydiving operations had commenced at Grenchen that day, as the activation of the jumping service had not been communicated.
Findings
- The primary cause of the airprox was the failure of the pilot of the HB-FLK to comply with the altitude restriction of 5,000 feet.
- The pilot of the HB-FLK chose to continue the climb to 6,000 feet because of cloud interference, despite being explicitly told that IFR traffic was above him.
- The pilot of the HB-FLK demonstrated incomplete knowledge regarding standard procedures for navigating the local airspace.
- The separation between the aircraft reached a critical minimum of 100 feet vertically during the encounter.