What happened
On August 1, 2011, an ATR 42-500, registration F-GPYO, was climbing through the Chambéry TMA toward Paris Orly. Simultaneously, a Decathlon aircraft, registration LX-FUN, was cruising at FL 105 on a flight between La Mole and Luxembourg.
During the climb, the air traffic controller provided traffic information to both crews, noting the relative positions of the two aircraft. The crew of the F-GPYO reported they did not have visual contact with the LX-FUN but noted a TCAS information alert. In an attempt to avoid the traffic, the F-GPY to crew executed a 30-degree right turn. The controller, under the impression that the crew was performing a visual avoidance maneuver, suggested a left turn to cross the path of the LX-FUN.
However, the F-GPYO crew then experienced a TCAS Resolution Advisory (RA) commanding a climb. This led to a second 30-degree right turn. During this sequence, the vertical separation between the two aircraft dropped to 950 ft, with a horizontal separation of only 1 NM.