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ASN Wikibase Occurrence # 218498
Last updated: 23 February 2020
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Date:07-APR-2018
Time:14:37
Type:Silhouette image of generic PA34 model; specific model in this crash may look slightly different
Piper PA-34-200 Seneca
Owner/operator:Air Safety
Registration: HB-LEM
C/n / msn: 34-7350327
Fatalities:Fatalities: 0 / Occupants: 2
Other fatalities:0
Aircraft damage: None
Category:Serious incident
Location:2 km NNE of Zug -   Switzerland
Phase: En route
Nature:Private
Departure airport:Buochs Airport (BXO/LSZC)
Destination airport:Zürich-Kloten Airport (ZRH/LSZH)
Investigating agency: STSB Switzerland
Narrative:
At 14:30, a Robin DR.300/180R (D-EAIO) towplane departed Hausen am Albis Airfield (LSZN), Switzerland. It was towing a single-seater ASW 20 CL glider, (HB-1784). The aircraft flew in a continuous climb first about 4 km in a westerly direction, then turning south and southeast in the direction of Rossberg. The average rate of climb during the towed flight was about 3 m/s (590 ft/min) and the average speed over ground was (Ground Speed - GS) 70 kt.
At the same time a Piper PA-34-200 (HB-LEM) was en route on a flight from Buochs Airport (LSZC) to Zurich Airport (LSZH). The flight route of HB-LEM led straight across the Zugersee and then via the city of Zug in a northeasterly direction. The airplane flew on a constant altitude of around 4700 ft AMSL and with a GS of around 150 kt.
After a flight time of about 4 minutes the tow plane flew over the city of Baar. A little further south, at a flight altitude of about 4700 ft AMSL, the pilot of the glider saw a fast-moving aircraft from the front, right side. He recognized that HB-LEM was on a collision course and immediately radioed the towing pilot that there was an aircraft approaching from the 2 o'clock position. Since the pilot of HB-LEM had obviously not recognized the tow plane and glider, and did not initiate an evasive manoeuvre, both the towing and glider pilot attempted unsuccessful to draw attention by means of short, repeated wing wobbling.
The glider pilot, whose plane was about 60 meters behind the towplane on the tow rope, realized that HB-LEM was heading directly for him and would only just fly over him. He therefore briefly reduced the rate of climb by applying slight pressure to the elevator control. HB-LEM subsequently crossed the flight path of the glider directly above at a distance of 20 meters.
Subsequently, all three pilots continued their flight without further incidents. After the flight, the pilot of HB-LEM stated that he and his passenger saw several aircraft in the Hausen am Albis area. The tow plane and glider involved in the incident had not been noticed by them.

All three aircraft involved in the incident were equipped with Flarm, an airborne collision avoidance system for gliders. However, all three pilots reported that there was no indication or warning on their Flarm's.

Sources:

https://www.sust.admin.ch/inhalte/AV-berichte/HB-LEM_D-EAIO_HB-1784.pdf

Accident investigation:
cover
  
Investigating agency: STSB Switzerland
Status: Investigation completed
Duration: 7 months
Download report: Final report


Revision history:

Date/timeContributorUpdates
24-Nov-2018 20:51 harro Added
24-Nov-2018 20:52 harro Updated [Narrative]

Corrections or additions? ... Edit this accident description