What happened
On April 12, 2010, two commercial flights were on converging approaches to Porto Airport (LPPR). The TAP Portugal flight, an Airbus A319 (TAP1580), was arriving from Madeira (LPMA), while the Ryanair flight, a Boeing 737-800 (RYR69VN), was arriving from Birmingham (EGBB).
Due to air traffic management decisions, the arrival sequence was inverted to prioritize the TAP flight. The Ryanair aircraft was instructed to maintain a higher altitude and reduce speed to allow the TAP aircraft to land first. However, the TAP crew, attempting to reduce speed and configure the aircraft for approach, decreased their rate of descent. This maneuver, combined with the Ryanair flight's need to extend its path for altitude loss, resulted in the two aircraft crossing paths approximately 8 nautical miles southwest of the XAPIM waypoint.
At the moment of crossing, the vertical separation between the two aircraft was only 800 feet. The incident was only prevented because the Ryanair crew received a TCAS/TA (Traffic Advisory) and proactively reduced their rate of descent to avoid a subsequent TCAS/RA (Resolution Advisory).
The investigation
The GPIAAF investigation examined the air traffic controller's (CTA) management of the arrival flows and the flight profiles of both aircraft. The investigation focused on why the separation was lost despite the controller's instructions and why the Short Term Conflict Alert (STCA) did not activate during the convergence.
Findings
- The controller's decision to invert the landing order placed the aircraft on converging tracks that were expected to intersect.
- The TAP crew reduced their rate of descent to manage speed and configuration without coordinating this change with Porto Approach.
- The air traffic controller overestimated the TAP aircraft's ability to maintain its descent profile and failed to issue instructions to prevent the loss of separation.
- The separation was maintained solely due to the timely reaction of the Ryanair crew to the TCAS/TA alert.
Safety action
- It is recommended that NAV Portugal, E.P.E. include training modules in their programs to sensitize controllers to the need for early detection of crew reactions and closer monitoring of altitude and descent rate changes to prevent separation loss.