What happened
On the evening of 5 January 2004, a serious airprox incident occurred at Lugano-Agno airport involving an AVRO 146-RJ100, registration HB-IXR, operated by Swiss International Air Lines, and a Piper PA28, registration HB-OYI.
The Swiss aircraft was performing an instrument approach to runway 01, intending to circle to land on runway 19. Simultaneously, a Piper PA28 from a local flying school was preparing for night training circuits. As the HB-IXR approached, the air traffic controller (ATCO) cleared the HB-OPI for takeoff from runway 19, providing traffic information regarding the approaching Swiss jet. However, the flight crew of the HB-IXR did not acknowledge this information, and the ATCO did not seek confirmation.
As the two aircraft converged on opposing headings, the distance closed to approximately 0.8 NM. The aircraft passed each other with a lateral separation of only a small margin and an altitude difference of roughly 600 ft. The instructor on the Piper aircraft eventually requested a heading change to avoid potential wake turbulence from the larger jet.
The investigation
The investigation established that the incident was rooted in a lack of coordination regarding updated flight procedures. Recently, the Federal Office for Civil Aviation (FOCA) had approved a new, specialized circling procedure for Swiss International Air Lines that differed significantly from the standard published procedures. This new procedure involved a lower circuit altitude and a later break-off point.
Crucially, the air traffic controller was not fully aware of these specific changes. While there had been verbal mentions of changes during shift changes, the official documentation and charts had not been formally provided to the air traffic management staff. Furthermore, the investigation found that the ATCO's reliance on the standard published procedures led to incorrect assumptions about the flight path of the HB-IXR.
Findings
- The air traffic controller's planning was based on incorrect assumptions because they were unaware of the specific procedures being applied by the flight crews.
- The new circling procedure for runway 19, which applied only to certain operators, had not been communicated to air traffic control in detail.
- Communication shortcomings occurred, as the flight crew of the HB-IXR did not confirm receipt of traffic information, and the ATCO did not verify that the information had been understood.
- There was no radar coverage available at the specific altitude where the convergence took place to assist the controller.
- The flight crew of the HB-IXR followed the approved, albeit non-standard, procedure accurately.
Safety action
Following the incident, a safety recommendation was issued to the FOCA to ensure that all IFR and VFR procedures are uniformly defined and published in the AIP. This is to ensure that all operators and air traffic controllers are working from the same documented standards, preventing future discrepancies in separation planning.