What happened
On December 12, 2018, two aircraft operating under Visual Flight Rules (VFR) experienced a serious near-collision near the Julier Pass. The first aircraft, a Cessna 172S with registration HB-CQW, was conducting a training flight from Hausen am Albis to Samedan. During the flight, the instructor performed two turning maneuvers for training purposes without notifying other aircraft in the area via a blind call.
Simultaneously, a Piper PA-32R-301, registration HB-PES, was on a navigation flight from Grenchen to Samedan. As the crew of the Cessna 172S contacted the Samedan Aerodrome Flight Information Service (AFIS) to announce their arrival, they spotted the Piper PA-3/2R-301 directly ahead of them. The two aircraft were separated by only approximately 250 meters horizontally and 100 feet vertically. The crew of the HB-PES did not see the Cessna 172S at any point during the encounter.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) examined the circumstances surrounding the encounter, focusing on visibility, cockpit configuration, and communication. The investigation noted that while both aircraft were equipped with transponders, neither was equipped with a collision warning system (such as Powerflarm). The investigation also reviewed the notification process, noting that the incident was not immediately reported to the official reporting office (REGA) as required by Swiss regulations.
Findings
Several factors contributed to the dangerous proximity of the two aircraft:
- The instructor of the Cessna 172S performed turning maneuvers over a key entry/exit point for Samedan traffic without issuing a blind call to alert other pilots.
- Limited visibility caused by the aircraft configurations; the high-wing Cessna 172S and low-wing Piper PA-32R-301 created blind spots that hindered the 'see and avoid' principle.
- Challenging visual conditions due to the high contrast of the snow-covered landscape at the Julier Pass.
- The absence of collision warning systems on both aircraft played a critical role in the inability to detect the other aircraft before the encounter.
Safety action
While the investigation noted that the operator of the HB-PES had proactively decided to install collision warning systems despite pending financial subsidies, the lack of such technology was a significant safety gap in this instance.