What happened
On January 14, 2006, at Chavenay Aerodrome, a mid-air collision occurred between a Cessna 150 (registration F-BSIX) and a Cricri (registration F-PHMN). The Cessna, an aircraft used for flight instruction, was on its final approach to runway 10 with an instructor and a student pilot on board. Simultaneously, the Cricri was positioned at the holding point, awaiting clearance for departure.
At 13:32 UTC, the tower controller authorized the Cricri to line up and wait, granting an immediate departure clearance. Shortly thereafter, the controller instructed the Cessna pilot to execute a go-around. As the Cricri began its initial climb at a steep angle, it collided with the Cessna. The propeller of the Cessna struck the vertical stabilizer of the Cricri, causing the latter to crash at the threshold of runway 28. The pilot of the Cricri was killed in the accident. The Cessna sustained minor damage and was able to land safely on runway 23.
The investigation
The investigation focused on the sequence of events involving the tower controller, the aircraft trajectories, and the management of traffic at the aerodrome. Investigators examined the controller's decision-making process regarding the timing of the departure clearance and the instruction for the go-around. The investigation also reviewed the movement of a third aircraft, a taildragger, which had been vacating the runway, as its delay in clearing the runway impacted the timing of subsequent clearances.
Findings
- The controller authorized the Cricri for an immediate departure while a previous aircraft was still in the process of vacating the runway.
- The controller's desire to prevent engine overheating in the Cricri during a prolonged wait led to the decision to grant an immediate departure clearance.
- The primary cause of the collision was the simultaneous execution of a takeoff and a go-around maneuver in the same airspace.
- The controller estimated there was sufficient time to depart the Cricri before the Cessna arrived, but the delay of the preceding aircraft in vacating the runway created a conflict.
- The pilot of the Cessna was instructed to perform a go-around just as the Cricri was entering the departure path.