What happened
On September 28, 2008, a Dassault Falcon 900, operated by the French Air Force with registration F-RAFQ, was conducting an IFR flight from Angers Marcé to Villacoublay-Vélizy. Simultaneously, a Cessna 172 (registration F-BXIX) was performing a VFR navigation flight from Tours Val-de-Loire toward Pontoise.
At approximately 15:31 UTC, the F-BXIX entered the Paris CTR 1 at roughly 2,500 feet. While the pilot was monitoring the Chartres radio frequency, the aircraft's presence triggered an Area Proximity Warning (APW) on Orly Approach radar screens. As the F-BXIX continued through the controlled airspace, it triggered a Short Term Conflict Alert (STCA) with an Airbus A319 on approach to Orly.
At 15:39 UTC, the F-RAFQ was established on the ILS approach for runway 09 at Villacoublay. The Villacoublay Tower controller observed the F-BXIX exiting the Toussus-le-Noble circuit to the north. Immediately following this, the F-RAFQ crew received a TCAS resolution advisory to climb. The crew visually identified the conflicting aircraft and executed the maneuver. The separation between the two aircraft was calculated to be approximately 0.2 NM horizontally and 400 feet vertically.
The investigation
The investigation focused on the navigation error of the F-BXIX and the coordination between various air traffic control services, including Orly Approach, Villacoublay Approach, and Toussus Tower. Investigators examined the radio and telephone communications between these centers, noting that while the F-BXIX was generating alerts, the pilot was not communicating with the relevant controllers. The investigation also reviewed the equipment status of the F-BXIX, noting that its GPS unit was temporarily uninstalled for repairs, which may have contributed to the navigation error.
Findings
- The primary cause of the incident was a navigation error by the pilot of the F-BXIX, which led the aircraft into controlled airspace without establishing contact with local controllers.
- The F-BXIX was operating without a GPS, relying on other navigation methods during its flight.
- There was a lack of real-time coordination regarding the specific location of the intruding aircraft between Orly and Toussus controllers during the critical minutes preceding the TCAS alert.
- The TCAS system on the F-RAFQ functioned correctly, providing the necessary resolution advisory to prevent a collision.