Incident Overview
On the evening of 5 January 2004 at 17:18 UTC, a serious incident (airprox) occurred at Lugano-Agno airport between SWR 74PE, an AVRO 146-RJ100 registered HB-IXR operated by Swiss International Air Lines, and HB-OYI, a Piper PA28 operated by AVILÙ SA. SWR 74PE was arriving from Zurich (LSZH) on an instrument approach to runway 19, while HB-OYI was conducting night flying training circuits (VFR by night) from the same airport.
Sequence of Events
At 17:12 UTC, SWR 74PE initiated contact with Lugano control tower and requested a “whole approach...rwy 19”. The controller cleared the aircraft for a LOC/DME approach 01, circling to land 19, and asked it to report PINIK inbound. At 17:13:46, the Piper PA28 reported ready for departure at holding point OSCAR. The controller cleared it to back track runway 19. Shortly after, SWR 74PE reported “PINIK inbound” and was instructed to report break off for downwind.
At 17:16:16, HB-OYI aligned on runway 19 and reported ready for take-off. The controller cleared it for take-off and issued traffic information about the approaching SWR 74PE. The controller had to ask for confirmation from HB-OYI regarding reception of this information. At 17:16:58, the controller also issued traffic information to SWR 74PE about the Piper taking off. The Swiss crew did not confirm receipt, and the controller did not request confirmation.
Subsequent radio exchanges revealed that the flying instructor on HB-OYI asked about the altitude of SWR 74PE at 17:17:19. The controller determined the circuit altitude was 2600 ft/QNH. By then, SWR 74PE was already at 2600 ft/QNH according to its flight data recorder (DFDR). The flying instructor stated they would follow the AVILÙ school circuit at 2000 ft. After controller confirmation, HB-OYI requested to continue toward reporting point WHISKEY to avoid wake turbulence, resulting in a more westerly heading than the standard school circuit.
During the critical phase, the two aircraft closed to about 0.8 NM on opposite headings before SWR 74PE initiated the break-off. They passed each other with a small lateral separation and an altitude difference of about 600 ft.
Unpublished Procedures
According to DFDR data, SWR 74PE was following an approach procedure that entered into force on 1 January 2004, conceded by the Federal Office for Civil Aviation (FOCA) to the airline. This procedure differed from the published night circling runway 19 approach in two key aspects: a later break-off (1 NM instead of 2.5 NM ILU DME) and a lower circuit altitude (2610 ft instead of 3600 ft). The Swiss flight crew later stated they had not heard the controller’s traffic information about HB-OYI nor noticed the dangerous convergence.
Air traffic control at Lugano was not fully aware of this different circling procedure at the time of the incident. The procedure and relevant approach charts were handed over to the Lugano air traffic control manager by Skyguide’s Chief of Operations on 6 January 2004.
Background to Procedure Changes
The FOCA had issued a media release on 22 August 2003 stating that existing approach and departure procedures for Lugano deviated from international standards. Subsequent measures included increased minimum visibility values and changes to the PAPI glide angle. On 31 October 2003, FOCA granted Swiss an exclusive exceptional approval for a different IGS approach procedure. On 22 December 2003, FOCA approved a new circling procedure for runway 19, valid from 1 January 2004, applicable only to Swiss and one other airline. This approval was emailed to Skyguide but not accompanied by chart material.
The AVILÙ school circuit, approved in 1999 by the Lugano aerodrome manager, was published only on the premises of the flying school and not in the AIP.
Analysis
The basis of this serious incident lies in the fact that the two flight crews were applying VFR and IFR procedures respectively which were not published and with which the air traffic controller was only partially acquainted. The controller expected SWR 74PE to break off at 2.5 NM ILU DME and maintain 3600 ft, as per the AIP procedure, but the aircraft followed the newer, unpublished procedure with a 1 NM break-off and 2610 ft altitude.
Air traffic control’s task to issue traffic information and ensure it was understood was not fully achieved. The controller did not have complete knowledge of the procedures being flown, and no radar coverage existed for the altitude involved to provide assistance. Controllers had verbally informed each other of changes since early January 2004 without precise instructions.