What happened
On July 12, 2009, at 14:56 local time, a Cessna S550 Citation, registration CS-DDV, was performing an approach to runway 01 at Évora Aerodrome (LPEV). During the final stages of the approach, the crew was forced to discontinue the landing to avoid a collision with a glider, registration D-2808, which was approaching runway 26.
The two aircraft were on converging flight paths at approximately 120 knots. While the Citation was on short final for runway 01, the glider had altered its planned approach to land on the unpaved runway 26. The incident occurred amidst a busy traffic environment that included a Cessna 152 on base leg and a Cessna 280B taxiing for parachute jumping operations. No injuries or aircraft damage were reported.
The investigation
The GPIAAF investigation examined radio communications and aerodrome operations. It was established that the glider pilot attempted to transmit a position report, but the transmission was obscured by overlapping communications from the Citation. This resulted in a period of approximately one minute where the radio frequency was excessively occupied, preventing the glider's presence from being clearly understood by all participants.
Furthermore, the investigation scrutinized the role of the Aerodrome Flight Information Service (AFIS) provided by the Aerodrome Traffic Information Agent (AITA). The investigation found that the AITA used terminology more consistent with Air Traffic Control, such as issuing "continue" instructions and attempting to assign priority, which exceeded the actual scope of the AFIS mandate.
Findings
- The primary cause of the incident was that the crew of the Cessna S550 Citation did not timely yield the right-of-way to the glider, as required by international aviation regulations.
- The simultaneous operation of aircraft with highly diverse performance characteristics (gliders, light aircraft, and business jets) increased the complexity of the traffic environment.
- Excessive radio frequency congestion prevented the glider's initial position report from being heard.
- The lack of an Air Traffic Control service, combined with the presence of high-intensity activities like parachute jumping, contributed to the risk of collision.
Safety action
- The investigation recommended that the Évora Municipal Council promote the relocation of parachute jumping activities to a location sufficiently far from the runway to prevent interference with aircraft operations.
- It was recommended that the use of infrastructure by gliders and tow planes be coordinated to avoid simultaneous conflicts with other aircraft.
- The investigation called for improved training for AFIS agents to ensure the use of appropriate radio phraseology consistent with the nature of the service provided.