Mid-air collision between two gliders near Kirchzarten

Casualties unknown • Kirchzarten, DE

Two gliders collided in mid-air over the Black Forest region, resulting in significant damage to one aircraft and a non-functional collision warning system.

What happened

On April 30, 2017, at approximately 15:27 local time, two gliders collided at an altitude of roughly 2,450 meters AMSL near Kirchzarten, Germany. The first aircraft, a Schempp Hirth Ventus cM, was flying on a cross-country flight from Leibertingen, heading in a southwesterly direction. The second aircraft, a Schempp Hirth Discus 2c, was also engaged in a cross-country flight, traveling in a northerly direction.

Both aircraft were flying at speeds exceeding 150 km/h and were on a direct collision course. At 15:25, the aircraft were approximately 5 km apart; one minute later, they were only 500 m apart. Neither pilot performed any visible evasive maneuvers before the impact.

The collision caused the Ventus cM to lose approximately 3.6 meters of its right wingtip. Despite the structural damage, the pilot maintained control and successfully landed at Reiselfingen airfield about 13 minutes later. The Discus 2c sustained damage to its left wingtip but remained fully controllable. The pilot of the Discus 2c performed a left turn to locate the other aircraft before continuing the flight and landing at Farrenberg approximately one hour later. Both pilots were uninjured.

The investigation

The BFU examined flight path data from satellite navigation units and Flarm anti-collision warning devices carried by both aircraft. The investigation focused on why the pilots failed to receive any warning of the approaching aircraft, as both pilots reported receiving no alerts prior to the collision.

Findings

  • The primary cause of the collision was the failure of the anti-collision warning system in the Discus 2c.
  • Data analysis revealed that the Flarm device in the Discus 2c was running firmware version v6.05, which was non-operational on the day of the accident. This prevented the device from both transmitting signals and receiving/processing signals from other aircraft.
  • The Flarm device in the Ventus cM was running a valid firmware version (v6.09) and was functioning correctly, meaning it was capable of detecting the other aircraft, but the lack of signal from the Discus 2c prevented a warning from being issued.
  • There was no radio communication between the two pilots prior to the impact.

Probable cause

The collision occurred because the anti-collision warning system on the Discus 2c was non-functional due to outdated firmware, preventing both pilots from detecting the approaching aircraft.

Frequently asked questions

What happened in the 2017-04-30 1. Schempp Ventus cM accident near Kirchzarten, DE?

Two gliders collided in mid-air over the Black Forest region, resulting in significant damage to one aircraft and a non-functional collision warning system.

What aircraft was involved and where did it happen?

The accident on 2017-04-30 involved a 1. Schempp Ventus cM, at Kirchzarten, DE.

What was the probable cause of the accident?

The collision occurred because the anti-collision warning system on the Discus 2c was non-functional due to outdated firmware, preventing both pilots from detecting the approaching aircraft.

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