B737-800 climbs to avoid unseen glider on IFR descent

A Boeing 737-800 on an IFR flight from Antalya to Nuremberg came within an estimated 100-150 m horizontally and 45-60 m vertically of an unidentified glider in Class E airspace; the Boeing landed safely. Descending through about 1,830 m AMSL the crew sighted the glider slightly left of track, in a right turn and apparently climbing, about ten seconds before reacting. The PIC disconnected the autopilot, altered heading from 300 to 308 degrees and stopped the descent at about 1,890 m AMSL; the glider passed beneath the Boeing's left wing. The glider had no transponder and could not be identified on civilian radar or TCAS.

1. IFR descent toward Nuremberg: At about 14:19 LT on 14 May 2015 a Boeing 737-800 of a German carrier was on an IFR flight from Antalya (Turkey) to Nuremberg with 6 crew and 113 passengers on board. After sequential clearances from München Radar — FL180 → FL110 → FL70 → 6,000 ft AMSL (~1,830 m) — the aircraft was descending in Class E airspace. Weather was CAVOK, wind 300°/7 kt, with cumulus base around 6,500 ft.
2. Glider VFR without transponder: An unidentified glider was operating VFR in the same Class E airspace, climbing in a right turn at the time of the encounter. It had no active transponder, so it did not appear on civilian ATC radar or on the Boeing's TCAS — neither a secondary nor a primary target was visible to the controller. The glider could not be identified after the event.
3. Crew spots glider ~10 s before action: About ten seconds before the avoidance manoeuvre the PIC and copilot saw an object slightly to the left of their track and shortly identified it as a glider in a right turn, apparently climbing. With the Boeing still descending toward 6,000 ft AMSL the PIC judged that the existing track would lead to a collision.
4. AP off, right turn, descent stopped: The PIC disconnected the autopilot at 14:19:25 LT and altered the heading from 300° to 308° using the control wheel. He reduced the sink rate and stopped the descent at about 6,200 ft AMSL (~1,890 m).
5. Pass ~100-150 m horiz / 45-60 m vert: The glider passed beneath the Boeing's left wing. The PIC estimated the closest separation at 100 to 150 m horizontally and 150 to 200 ft (~45-60 m) vertically. The pilot of the glider was clearly visible. The Boeing then landed normally at Nuremberg.