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A343 / GLID, en-route, north of Waldshut-Tiengen southwest Germany, 2012
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Revision as of 19:35, 23 November 2014 by Integrator1
On 2 June 2012, an Airbus A340-300(HB-JMN) being operated by Swissair on a scheduled passenger flight from San Francisco to Zurich as SWR39 came very close to colliding with an ASW 20 glider (HB-1519) as it joined final approach at destination in day Visual Meteorological Conditions (VMC) whilst over Germany in accordance with its Swiss air traffic clearance. Only immediate and very positive avoiding action created minimal separation.
An Investigation was commenced after delegation of responsibility for it was made by the German BFU to the Swiss Accident Investigation Board (SAIB). Sufficient recorded data relevant to the Investigation was available from ATC radar recordings.
It was established that, with the Airbus passing 4700 feet Altimeter Pressure Settings for 4000 feet at 248 knots and about to join the Instrument Landing System (ILS) Localiser for runway 14 at Zurich, the augmenting crew member observing the approach from the central supernumerary crew seat suddenly saw a glider at the same altitude on a collision course. The operating crew were immediately alerted and the First Officer, designated PF took avoiding action. The Airbus was flying in accordance with its clearance from the Zurich APP controller but the glider was found to have entered the Class 'C' TMA in which the conflict occurred without permission.
Recorded radar data showed that "a pronounced avoidance manoeuvre" by the A340 was made 5 seconds prior to the closest proximity and had involved "a maximum bank angle of 36 degrees to the left and an increase in attitude to approximately 5 degrees, which generated a normal acceleration of 1.6 g". It was found that 13 seconds before the closest proximity, the glider had begun "an abrupt right-hand turn as an avoidance manoeuvre". The two aircraft subsequently "passed at approximately the same height at a lateral distance of approximately 260 metres" (850 feet) ten seconds after the A340 had initiated avoiding action. The situation is depicted on the diagram below included in the Official Report.
It was considered that the recorded flight paths of the two aircraft over the less than 15 seconds which had elapsed from the initiation of avoiding action until the position of closest proximity showed that "neither avoidance manoeuvre in isolation was decisive in avoiding a collision". It was also concluded that the dynamics of this encounter "clearly indicate(d) that that there are few opportunities for action to avoid a collision (when) in a relatively slow moving aircraft."