What happened
On March 16, 2002, a Pilatus Porter PC6T, registration HB-FKT, departed Ecuvillens for a scheduled parachute jump operation. The aircraft was operating under Visual Flight Rules (VFR) and was climbing through 4,000 feet when the pilot contacted Geneva ACC (Delta sector) to request an ascent to Flight Level 150.
Simultaneously, an Airbus 320, flight CRX3009, was operating a scheduled commercial service from Geneva to Zurich at Flight Level 140. During the coordination process between air traffic controllers, the Pilatus Porter was cleared to climb, but the vertical separation between the two aircraft was not maintained. As the HB-FKT climbed through Flight Level 130, it intersected the flight path of the Airbus 320.
A Short Term Conflict Alert (STCA) was triggered, and the pilot of the Airbus 320 received a TCAS Resolution Advisory (RA) commanding an immediate climb. The Airbus 320 climbed to Flight Level 147, while the Pilatus Porter passed approximately 200 to 300 feet below the larger aircraft. Both pilots subsequently reported visual contact with the other aircraft.
The investigation
The investigation focused on the communication between the Geneva Delta sector and the INE radar sector. It was established that the Delta controller contacted the INE coordinator via telephone to request clearance for the climb to FL 150. The coordinator responded with a brief "Okay," which the Delta controller interpreted as a formal clearance, but the coordinator viewed only as an information update regarding a known aircraft.
Furthermore, the investigation found that the INE coordinator had recently undergone a shift change. The incoming coordinator had accepted the responsibility but was not fully aware of the specific climbing profile of the HB-FHD at the moment the conflict began. The investigation also noted that the HB-FKT had not submitted a flight plan or a NOTAM for its parachute jump operations, although the operator's flight calendar was available to the service provider.
Findings
- The primary cause of the incident was a miscommunication during coordination between the Delta and INE sectors, where a verbal notification was mistaken for an approved clearance.
- The coordination was flawed because the Delta controller used an imprecise phrasing when requesting the climb, leading to an inadequate response from the INE coordinator.
- The INE coordinator failed to correctly record the aircraft's profile, entering it as a cleared flight level rather than a requested flight level.
- The shift change at the INE workstation occurred at a critical moment, potentially affecting the continuity of situational awareness regarding the climbing HB-FKT.
- The Pilatus Porter was operating without a filed flight plan or associated NOTAM, which reduced the visibility of its specific flight intentions to the controllers.