DG-808 and DG-500 pass at 25 m: each crew focused elsewhere

A DG-808 C and a DG-500/22 ELAN passed at about 25 m horizontal and a few metres wing-tip to wing-tip near St. Moritz; no injuries or damage. Both were winch-launched from Samedan and met on near-reciprocal tracks at about 3,200 m MSL. The DG-808 C pilot was tracking a Duo Discus passing safely below-left; the DG-500's instructor was pointing out the hard-to-see Corvatsch cableway wires ahead-left. Neither crew saw the opposing glider against the bright cloud and snow background until the last moments; both then simultaneously rolled left. FLARM testing later found the DG-500's transmit and receive insufficient.

1. Cruise NE on Corvatsch N slope: On 16 June 2014 the DG-808 C cruised north-east on the Corvatsch's north slope; the DG-500 cruised south-west nearby, near-reciprocal tracks. A Duo Discus had just passed ahead, lower.
2. DG-808 pilot focused on Duo Discus: FLARM had warned the DG-808 pilot of a lower glider on a converging track. Seeing the Duo Discus, he corrected course right, then watched it pass under his left wing.
3. DG-500 crew focused on cableway wires: The DG-500 crew had already spotted the Duo Discus ahead-right, lower. The instructor was pointing out hard-to-see cables at the Corvatsch cableway's mountain station ahead-left.
4. DG-500 FLARM TX/RX degraded: Both gliders carried FLARM, but neither crew was warned. The DG-500's FLARM had a known weak receive and transmit range since 2013; a new antenna fitted that winter was never re-tested.
5. Bright cloud + snow background: The two gliders were closing against a background of bright clouds and snow fields, reducing the contrast needed to acquire each other visually.
6. Late mutual sighting at ~25 m: When the Duo Discus vanished under his left wing, the DG-808 pilot looked up and saw a second glider directly ahead, closing fast. The DG-500 crew saw it at the same instant, to their right.
7. Sim. left turns; clear by metres: Both crews instinctively rolled left almost together; the wingtips passed within a few metres. Flight-path data showed a horizontal separation of about 25 m (±5 m) at the closest point.