What happened
On 29 August 2003, at approximately 14:20 UTC, a near-miss incident occurred near the PINIK waypoint over Lugano, Switzerland, involving two aircraft on opposing headings. The first aircraft, a Saab 2000 (registration HB-IZH) operated by Swiss International Air Lines, was performing a scheduled flight from Zurich to Lugano. The second aircraft, a Cessna C551 Citation II (registration D-IMME) operated by Commander Flugdienst GmbH, was on a commercial flight from Hamburg to Lugano.
As the Saab 2000 was descending through 6000 ft, the Cessna C551 was cleared by Lugano Tower to maintain 7000 ft. However, the Cessna C551 descended through the assigned altitude, reaching as low as 6500 ft. The flight crew of the Saab 2000 received a Traffic Advisory (TA) followed by a Resolution Advisory (RA) from the TCAS system, prompting a descent. The two aircraft eventually passed each other with a lateral separation of only 0.3 NM and an altitude difference of 700 ft.
The investigation
The investigation examined the flight paths, radio communications, and autopilot settings of both aircraft. It was established that the Cessna C551 crew was using the autopilot to descend to 7000 ft. The investigation found that the co-pilot's altimeter was set to standard pressure (1013.2 hPa), while the captain's altimeter was set to the local QNH (1002 or 1003 hPa). This discrepancy led the crew to believe they were at the correct altitude during their initial contact with air traffic control.
Furthermore, the investigation looked into the capabilities of the Lugano Aerodrome Control. While the tower was equipped with a radar monitor, the controllers were only trained to use it as a distance-from-touchdown indicator and were not qualified to provide radar separation services.
Findings
- The Cessna C551 descended below its assigned altitude of 7000 ft due to inadequate coordination and a lack of familiarity with the autopilot/flight director system's operation.
- A significant altimeter setting error occurred: the co-pilot's altimeter was set to standard pressure (1013.2 hPa) instead of the local QNH, causing the crew to report being at 7000 ft when they were actually lower.
- The rate of descent for the Cessna C551 was high, reaching up to 3800 ft/min during the descent phase.
- The Lugano air traffic controller was unable to take effective preventive measures because they lacked formal radar training and were restricted to using the radar monitor only for monitoring approach distances.
Safety action
Following the incident, the Federal Office for Civil Aviation (FOCA) implemented new regulations regarding the procedures for acquiring and supervising qualifications for Lugano airport operations.