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ASN Wikibase Occurrence # 238021
Last updated: 27 January 2022
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Date:08-MAY-2020
Time:15:28 LT
Type:Silhouette image of generic AS29 model; specific model in this crash may look slightly different
Schleicher ASG 29
Owner/operator:SGKA Segelfluggruppe Knonaueramt
Registration: D-KAVE
MSN:
Fatalities:Fatalities: 0 / Occupants: 1
Other fatalities:0
Aircraft damage: None
Category:Serious incident
Location:Neuheim (ZG) -   Switzerland
Phase: En route
Nature:Private
Departure airport:Hausen am Albis Airfield (LSZN)
Destination airport:Hausen am Albis Airfield (LSZN)
Investigating agency: STSB Switzerland
Narrative:
The single-seater high performance glider ASG 29E/18m, registered as D-KAVE, took off from the Hausen am Albis Airport (LSZN) around noon for a cross-country flight. The pilot first flew in an easterly direction to Hohen Kasten in the Säntis area and then back to the Hausen a/A area. At 15:08, the glider turned left into an updraft 1 NM west of the village of Neuheim at an altitude of about 770 m. In the following 15 minutes, the glider climbed continuously in the thermal and reached a flight altitude of just under 1600 m at 15:23.
In the early afternoon of the same day, the crew of the Pilatus PC-24 twin-engine business jet, registered as HB-VZZ, conducted a test flight (Production Flight Test - PFT) from Buochs airfield (LSZC). In the cockpit were the pilot-in-command (PIC), who sat in the left seat, and a flight test engineer (FTE), who sat in the right seat. Among other things, an approach to runway 22 of the Emmen military airfield (LSME) was to be executed during the flight, which took place according to visual flight rules, with the aid of the instrument landing system. For this purpose, the flight crew, flying east of Lake Zug at 7200 ft AMSL, established radio contact with Emmen air traffic control at 15:23. The air traffic controller subsequently gave several traffic advisories which the HB-VZZ flight crew could identify either visually or on the TCAS display. In addition, the HB-VZZ was to remain east of Hausen a/A, as a fighter aircraft was still on approach to Emmen.

After the pilot of the glider could no longer find a usable updraft during the circling, he reduced the lateral attitude of his glider shortly before 15:28 and flew a wide left turn in a westerly to south-westerly direction at an approximately constant altitude of about 1600 m. The ground speed was about 120 km/h (65 kt). At this time, the PC-24 was flying north at 1605 m over the city of Zug and was moving at a GS of 200 kt.
At 15:28:02, the flight test engineer of the PC-24 spotted a glider ahead of them, exactly in the direction of flight, at the same altitude and at a distance of 1300 m. This glider was D-KAVE. He informed the pilot via intercom ("glider, same altitude, twelve o'clock"), who immediately switched off the autopilot and manually initiated a controlled evasive maneuver to the right. The PC-24 thereby assumed a lateral attitude to the right of about 60 degrees and a longitudinal inclination of 5 degrees downward (nose down) within 5 seconds.
At 15:28:11, the closest separation between the two aircraft occurred. This was about 320 m horizontally and about 60 m vertically.
Subsequently, both crews continued their flights as planned and later landed without incident in Buochs and Hausen a/A, respectively.

Conclusions
The serious incident involved a dangerous approach between a business jet and a glider, both of which were operating under visual flight rules and in airspace of airspace class E. The serious incident was caused by the fact that the glider and the business jet were flying under visual flight rules. The serious incident was caused by the fact that the two flight crews did not visually detect the other aircraft until late in the flight, or not at all. This can be attributed to the inadequacies of the "see and avoid" principle.
A contributing factor was determined to be that the glider's transponder was not turned on, which, although not mandatory, led to a dangerous situation in this case.

Sources:

https://www.sust.admin.ch/inhalte/AV-berichte/HB-VZZ_D-KAVE.pdf

Accident investigation:
cover
  
Investigating agency: STSB Switzerland
Status: Investigation completed
Duration: 12 months
Download report: Final report


Revision history:

Date/timeContributorUpdates
14-Jul-2020 09:07 harro Added
05-May-2021 13:59 harro Updated [Departure airport, Destination airport, Narrative, Accident report]

Corrections or additions? ... Edit this accident description