What happened
On November 8, 2006, a Darwin Airline Saab 2000, registration HB-IZG, was conducting an IFR commercial flight from Geneva to Lugano. While descending toward the airport, the crew requested an instrument approach for runway 01, which the controller authorized via a visual approach to runway 19.
Simultaneously, a private PA-28R-2D0 (registration HB-OKL) was transiting the Lugano control zone on a VFR flight from Locarno to Pula. The pilot of HB-OKL reported being at 3,500 feet near the MEZZO waypoint and requested to cross the airfield toward the ECHO waypoint.
As the Saab 2000 joined the left-hand downwind for runway 19, the crew received a Traffic Advisory (TA) from the TCAS system indicating a potential threat at their altitude. The crew then requested the position of the conflicting traffic. In response, the air traffic controller issued a highly erroneous instruction, clearing the Saab 2000 for takeoff while simultaneously instructing the VFR aircraft to cross the field at 3,000 feet. This instruction placed both aircraft on converging paths at nearly the same altitude. The crew of HB-IZG experienced a Resolution Advisory (RA) from TCAS, commanding them to "DESCEND, DESCEND." Radar data later confirmed that the two aircraft reached a minimum lateral separation of only 0.219 NM and a vertical separation of just 100 ft.
The investigation
The investigation examined the controller's actions, the radar capabilities at Lugano, and the workload at the tower. It was established that the controller was working alone and was distracted by non-ATC administrative duties, specifically the preparation of a new METAR weather report.
Furthermore, the investigation found that the controller had incorrectly recorded the altitude of HB-OKL as 3,000 feet on the control strip, despite the pilot reporting 3,500 feet. The investigation also noted that the radar equipment available at the tower was only intended for use as a Distance from Touchdown Indicator (DFTI) and was not approved for providing separation services or radar guidance. Additionally, the mountainous terrain surrounding the tower prevented the controller from having a direct visual line of sight to the left-hand downwind leg of runway 19.
Findings
- The controller failed to provide essential traffic information regarding the presence of HB-OKL to the crew of HB-IZG.
- The controller misrecorded the altitude of the VFR aircraft, noting 3,000 feet instead of the reported 3,500 feet.
- The controller's situational awareness was compromised by performing non-ATC administrative tasks, such as weather reporting, while managing traffic.
- The controller issued a critical error in communication, providing a takeoff clearance for one aircraft while directing the other into a conflicting path.