Overview
On 31 March 2005, a serious airprox incident occurred near Zurich Airport involving two light aircraft: HB-PHU, a Piper PA28-181 Archer operated by Fluggruppe Pro Altenrhein, and OE-KRT, a Piper PA28R-201T Arrow operated by PhoeniXperiance Innovations GmbH. The event took place at 11:48 UTC on the ILS approach to Runway 14.
Flight of HB-PHU
The pilot of HB-PHU was a student pilot holding a trainee license, nearing completion of his private pilot training. He had completed a training week in Raron (VS) with his instructor. On the day of the incident, he flew from Raron to Birrfeld (LSZF) with his instructor. After landing at Birrfeld, the instructor left the aircraft, and the student was to continue solo to St. Gallen-Altenrhein (LSZR). Weather conditions were described as not optimal but flyable.
The student departed Birrfeld at 11:20 UTC on Runway 26, climbing to 3000 ft. He intended to navigate via the TRA VOR (Trasadingen) and then follow the Rhine to his destination. After passing TRA, he turned east. Near Steckborn, he encountered deteriorating visibility and cloud conditions, prompting a decision to return to Birrfeld. He attempted to navigate back using the VOR but mistakenly selected the frequency for WIL VOR (116.90 MHz) instead of TRA VOR (114.30 MHz). This error led him on a course toward the WIL VOR, which brought him into the Zurich control zone.
The student reported that he saw the runway thresholds of Runways 14 and 16 at Zurich Airport and immediately took evasive action, turning right to leave the zone. He observed the other aircraft at about 1000 ft above him. He contacted Zurich Tower, identified himself, and was asked to call after landing. Radar data showed the two aircraft crossed at 11:47:42 UTC, 4 NM from the Runway 14 threshold, with a vertical separation of 400 ft and horizontal separation of 0.3 NM.
The student then flew back to Birrfeld via TRA VOR, landing at 12:10 UTC. He stated he had never experienced such a situation and felt overwhelmed.
Flight of OE-KRT
The crew of OE-KRT consisted of an instructor (pilot not flying) on the right seat, a student pilot (pilot flying) on the left, and a passenger who was also an IFR instructor. The flight departed Stockerau (LOAU) at 09:40 UTC on an IFR training flight to Zurich. After initial VFR departure, they received IFR clearance.
The aircraft entered Zurich airspace on the route KPT – NEGRA – SAFFA at FL 80. At 11:29:40 UTC, they contacted Zurich Approach, which vectored them to the ILS for Runway 14. At 11:46:05 UTC, they were instructed to switch to Aerodrome Control (ADC). The commander reported established on the ILS and received landing clearance at 11:46:26 UTC. They experienced intermittent cloud and light rain.
ADC issued two traffic advisories: at 11:46:58 UTC (primary target at 11 o'clock, 2 miles) and at 11:47:30 UTC (1 mile, 12 o'clock). The crew did not see the other aircraft. At 11:47:50 UTC, as they passed 2800 ft, they reported having passed a small aircraft. The HB-PHU pilot then identified himself.
Aftermath
The incident was classified as a serious incident (airprox). The pilots of both aircraft were contacted by authorities. The HB-PHU student discussed the event with his instructor after landing.