Introduction
On 22 August 2002, at 13:38 UTC, an airprox (near miss) occurred between two aircraft in the vicinity of TELNO, within the UAC Geneva airspace. The aircraft involved were Deutsche Lufthansa flight DLH4161, an Airbus A319, and Sonnig SA flight HB-VMV, a Cessna Citation C560. The incident took place in Class C airspace under instrument flight rules, with visual meteorological conditions reported by both pilots.
History of Flight HB-VMV
Flight HB-VMV departed Geneva for Salzburg at 13:25 UTC. After takeoff, it climbed to flight level (FL) 150 and was subsequently cleared by the INI E sector radar operator to FL 260 at a rate of climb of 1500 ft/min. The pilot reported increasing the climb rate to 2000 ft/min. At 20 nautical miles from TELNO, the flight was transferred to Zurich sector U1 RE on frequency 132.815 MHz. The pilot reported being at FL 240 and climbing to FL 260. The radar operator, a trainee under supervision, identified the flight and cleared it via BERSU-KUDES-BAMUR at FL 260. The pilot read back an incorrect route and FL 280. The radar operator repeated the route twice but did not correct the flight level error.
History of Flight DLH4161
Flight DLH4161, a scheduled service from Nice to Frankfurt, reported on the MOLUS3 frequency at 13:22 UTC, crossing FL 268 and climbing to FL 280. The radar operator identified the flight and instructed it to maintain FL 280. At 13:27, due to traffic, the flight was told to continue on its current heading, and later cleared direct to SOSAL-BERSU. It was then transferred to Zurich frequency 132.815 MHz. At 13:38, the pilot reported back on Geneva frequency 126.05 MHz and notified a TCAS climb. The radar operator cleared the flight to climb to FL 310. After coordination, the flight was cleared to descend back to FL 280 and transferred to Zurich frequency.
Incident Sequence
At 13:38:36, the Short Term Conflict Alert (STCA) at Zurich sector indicated a proximity alert with a minimum altitude difference of 600 ft and lateral separation of 1.5 NM between the two aircraft. At 13:38:37, the radar operator asked the pilot of HB-VMV if he was maintaining FL 270. The pilot responded, "negative, climbing towards flight level 280, I will descend back to flight level 270." At 13:38:48, HB-VMV reached FL 274. Meanwhile, at 13:38:41, the STCA alerted the Geneva radar operator of a proximity between DLH4161 and HB-VMV with an altitude difference of 800 ft and lateral separation of 1.9 NM. The pilot of DLH4161 reported a TCAS resolution advisory, indicating traffic in the opposite direction. The Airbus was equipped with TCAS; the Cessna was not.
Findings
The runway in use at Geneva was 05, with winds at altitude from 250° at 15-20 kt between FL 180 and 300. Both flights were operating under instrument flight rules. The radar operators and coordinators held valid licenses. The Zurich sector U1 RE staff included a trainee radar operator and a trainee coordinator, both under supervision. The pilot of HB-VMV had been cleared to FL 260 at 13:29:26, but later read back FL 280. The radar operator did not notice the incorrect flight level. After the STCA alerts and TCAS RA, the flights were separated and continued to their destinations.
Analysis
The readback error by the pilot of HB-VMV, combined with the failure of the trainee radar operator and supervisory staff to detect the incorrect flight level, led to a loss of separation. The trainee radar operator repeated the route but not the correct flight level. The STCA alert prompted corrective action. The minimum separation achieved was 600 ft vertically and 1.5 NM laterally before the TCAS RA on DLH4161 initiated a climb. The incident underscores the importance of verifying readbacks, though no explicit causal statement is provided in the source.