A Fokker 100 jetliner of Helvetic Airways and a Swiss medical helicopter were involved in an airprox incident in the Bern Airport Control Zone, Switzerland, according to a Swiss Accident Investigation Board report.
On 24 May 2012 the pilot of an Eurocopter EC 145 helicopter, registration HB-ZRC, operated by Schweizerische Luft-Ambulanz AG (REGA), received clearance from the Bern tower air traffic control officer (ATCO) to cross the Bern-Belp airport control zone at an altitude of 4500 ft QNH.
At the same time a Fokker 100 aircraft, flight OAW 5311, was approaching Bern-Belp airport. After receiving clearance from Bern Approach for a visual approach on runway 32, the crew first contacted Bern Tower. The ATCO requested the crew to continue the approach and at the same time issued initial traffic information about the helicopter. Immediately thereafter, the EC 145 pilot received corresponding traffic information regarding OAW 5311, which was on an approach.
Shortly thereafter, the ATCO again issued both crews with traffic information. Approximately one minute later, the helicopter pilot reported “traffic in sight”. The helicopter was in level flight at an altitude of 4500 ft QNH. A little later the pilot received an aural warning on his traffic advisory system. The pilot then initiated a heading change to the left in order to cross behind OAW 5311.
Four seconds after the helicopter pilot reported visual contact, the crew of OAW 5311 reported that they had a helicopter in sight and would avoid it. OAW 5311 was descending and passing 5000 ft QNH. At approximately the same time, the crew received on their traffic alert and collision avoidance system (TCAS) at first a traffic advisory (TA) and a little later the resolution advisory (RA) “climb, climb”. The crew attributed the resolution advisory to the helicopter they had in sight and therefore decided not to comply with the resolution advisory and continued the approach while descending. As a result of the continued descent, the TCAS generated the RA reversal “descend, descend NOW!” when the aircraft was passing 4500 ft QNH. Even after this command the crew did not change the aircraft’s rate of descent.
The two aircraft crossed with a lateral distance of 0.7 NM (1300 m) and an altitude difference of 75 ft (23 m).
Air traffic control’s short term conflict alert system (STCA) was not activated at any point since it had been disabled for Bern air traffic control many years before. OAW 5311 subsequently landed uneventfully in Bern-Belp and the helicopter continued its flight to Zurich.
The serious incident is attributable to the fact that there was a dangerous convergence of a commercial aircraft and a helicopter despite mutual visual contact, because no appropriate avoidance manoeuvre had been performed.
The limited effectiveness of the “see and avoid” principle was identified as the systemic cause of this serious incident.
- Final report No. 2220 (PDF)