Class C airprox: ASW 20 enters without clearance, A340 evades at 260 m horizontal

A Swiss A340 descending into Zurich and an ASW 20 passed at about 260 m horizontal separation and nearly the same altitude in TMA LSZH 2; both aircraft landed safely. The glider, on a VFR training flight from Bohlhof, had entered Class C airspace without clearance and was not visible to ATC. FLARM and TCAS II are incompatible, so no electronic warning was generated. The A340 was descending through about 1,430 m MSL on a Zurich Final clearance below the MRVA. An observer-seat pilot spotted the glider on the localizer turn; the A340 rolled 36 degrees left at 1.6 g and the glider pilot turned right. ICAO Cat A airprox.

1. A340 descent Zurich, ASW 20 at TMA edge: At 13:32 UTC on 11 August 2012 an A340 descending IFR into Zurich was at 6,000 ft in Class C airspace, while an ASW 20 on a VFR flight from Bohlhof was near that airspace at about 4,700 ft.
2. Glider in Class C without clearance: The glider had entered Class C airspace without clearance or a transponder, invisible to radar, so the airliner's TCAS could not advise and the ground alert did not trigger.
3. A340 cleared below MRVA: Zurich Final cleared the A340 to descend to 4,000 ft, below the minimum radar vector altitude for that airspace, and the controller did not monitor whether that floor was respected.
4. Observer spots glider on LOC turn: While the A340 was turning onto the localizer for RWY 14, a third pilot in the observer seat suddenly saw the glider on a collision course at the same altitude and warned the crew.
5. A340 36° left at 1.6 g; glider right: The A340 crew made an evasive turn — up to 36° left bank, 1.6 g — still in Class C at about 4,700 ft. Seconds earlier the glider pilot had also turned sharply right to avoid it.
6. ~260 m horizontal pass; both land safe: The two aircraft passed at nearly the same altitude with about 260 m separation. Both landed normally, the A340 at Zurich and the glider at Bohlhof; the encounter was rated high risk.