What happened
On June 1, 2010, an ATR 42-300, registered F-GKNB, was performing a departure from Brive-la-Roche aerodrome toward Paris-Orly. During the takeoff roll, the flight crew was focused on takeoff procedures and briefings. Simultaneously, a Mooney M20, registered F-GNGG, was approaching the area from Limoges on a private flight.
As the ATR 42-300 climbed through 1,200 feet, the captain noticed the Mooney M20 directly ahead at a similar altitude. The captain immediately interrupted the climb and descended slightly to maintain separation, while the pilot of the Mooney M20 also adjusted his descent to avoid the larger aircraft. The two aircraft passed each other closely, with the Mooney M20 passing slightly above and to the left of the ATR 42-300.
Despite the proximity, the crew of the ATR 42-300 did not receive any Traffic Collision Avoidance System (TCAS) alerts. Following the encounter, the pilots communicated via radio, at which point the ATR 42-300 crew realized the Mooney M20 was operating with a transponder code of 7000.
The investigation
The investigation examined the flight paths, radar coverage, and cockpit procedures. It was established that the Mooney M20 had lost radar contact approximately two minutes before the minimum proximity point because the pilot had switched to code 7000 while leaving the Limoges controller's frequency.
Investigators also reviewed the role of the Aerodrome Flight Information Service (AFIS). The AFIS agent had informed the pilot of the Mooney M20 that an ATR was preparing for takeoff, but did not provide the same information to the ATR 42-300 crew, as the Mooney M20 was not yet in the aerodrome traffic circuit.
Regarding the TCAS, the investigation found that while a Traffic Advisory (TA) would have likely been generated 15 seconds before the encounter, no Resolution Advisory (RA) was possible because the ATR 42-300 was below the 1,100-foot threshold required for RA activation during a climb.
Findings
- The primary cause was the Mooney M20 pilot's separation strategy, which relied on visual monitoring and vertical spacing without accounting for potential altitude changes by the commercial aircraft.
- The ATR 42-300 crew demonstrated an over-reliance on TCAS and a lack of adequate external visual surveillance during the instrument departure.
- The ATR 42-300 crew's workload during the departure phase hindered effective outside monitoring.
- The lack of a TCAS alarm occurred despite both systems being fully functional.
- The AFIS agent's failure to notify the ATR 42-300 crew of the approaching traffic could have increased the crew's vigilance.
Safety action
- The BEA recommended that the DGAC protect the IFR trajectories of commercial aircraft equipped with TCAS by requiring the use of radio and transponders for access to these specific zones.