A319 / PRM1, en-route, near Fribourg Switzerland, 2011

A319 / PRM1, en-route, near Fribourg Switzerland, 2011

Summary

On 10 June 2011 an ATC error put a German Wings A319 and a Hahn Air Raytheon 390 on conflicting tracks over Switzerland and a co-ordinated TCAS RA followed. The aircraft subsequently passed in very close proximity without either sighting the other after the Hahn Air crew, contrary to Company procedures, followed an ATC descent clearance issued during their TCAS ‘Climb’ RA rather than continuing to fly the RA. The Investigation could find no explanation for this action by the experienced crew - both Hahn Air management pilots. The recorded CPA was 0.6 nm horizontally at 50 feet vertically.

Description

On 10 June 2011, in day Visual Meteorological Conditions (VMC), an Airbus A319 being operated by German Wings on a scheduled passenger flight from Barcelona to Stuttgart lost separation against a Raytheon 390 being operated by German air taxi company Hahn Air on a non scheduled passenger flight from Zurich to Palma. Late ATC attempts to resolve the conflict were pre-empted by co-ordinated TCAS RAs but during them, the Hahn Air crew elected to reverse their initial TCAS RA climb whilst it was still annunciated in favour of an ATC instruction to descend. This action very significantly reduced the separation which would otherwise have prevailed.

Investigation

An Investigation was carried out by the Swiss AIB. The Investigation was based upon ATC R/T and radar recordings (including mode ‘S’ downlink data from both aircraft) and on the downloaded Flight Data Recorder (FDR) data from the A319. It was noted that the conflict had occurred in Class ‘C’ airspace and that the aircraft involved had been working sectors under the control of two different ACCs throughout the sequence which led to the conflict.

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