Serious incident between two BEECH 200s registered F-HNAV and F-HCEV on 17/04/2019 near Le Bourget (Seine-Saint-Denis)

Cat. 2 investigation report: simplified-format report, adapted to the circumstances of the occurrence and the investigation stakes.

The Beech 200 registered F-HCEV was carrying out a calibration flight departing from Paris-Le Bourget airport (Seine-Saint-Denis). The main aim of this flight was to bring the new DME associated with L’Aigle VOR (LGL), located 75 NM to the west, into service. On their route, the crew also had to check a radial used in the standard departure procedure (SID) for runway 21 at this airport.
The Beech 200 registered F-HNAV was carrying out a calibration flight on the same day with the aim of calibrating the two new ILS of runway 08R / 26L at Paris-Charles de Gaulle airport (Val d’Oise).
The crews of these two flights consisted of a captain and a co-pilot from ENAC, the latter being the operator of these calibration flights. The calibration measurements were monitored by a calibration engineer from the DSNA (French air navigation service provider) sitting at the rear, in the cabin.
The flight programme for F-HCEV comprised a calibration of radial 086 of the LGL VOR in accordance with the standard departure procedure (SID 21), then tracking to the LGL VOR. This calibration was therefore not considered by the air traffic controllers to be an activity that could interfere with the calibration programme being carried out by the crew of F-HNAV at the time of the incident.
During the flight preparation, the calibration engineer plotted this radial on an aeronautical chart. The manual plot situated radial 086 to the north of prohibited zone P23 corresponding to the city of Paris and seemed consistent with the path of SID 21. The two pilots did not therefore check the calibration engineer’s plot. The investigation showed that there was an error in the published procedure and that radial 086 passed into prohibited zone P23 and was therefore not consistent with the published procedure.
Before take-off, the crew of F-HCEV entered SID 21 and radial 086 in the plane’s FMS and displayed the airspaces. The MFD’s zoom level did not enable the crew to see where this radial passed and to identify the inconsistency. As this check was not done, the crew were unable to detect that the measurement was not possible.
The crew of F-HCEV took off from runway 21, climbed ahead following SID 21, then turned right to take heading 270 given by the air traffic controller. During initial climb, the captain of F-HCEV zoomed out of the MFD display and observed that the radial entered in the FMS was further south than expected and passed through prohibited zone P23.
The calibration engineer did not have the option to display the airspaces or SID 21 on the calibration system screens. He did not therefore have the same display of the situation as the F-HCEV pilots and for him, the radial could not pass through Paris.
After discussions between the pilots and the calibration engineer of F-HCEV, the crew asked the air traffic controller for clearance to head south to try to join radial 086. In response, the air traffic controller gave the instruction to visually track the ring road and to take the best heading to start the measurement, thinking that the crew would continue their route westwards. Indeed, the controller considered this to be a standard departure with a calibration measurement when on the SID. He therefore expected, first and foremost, compliance with the SID.
The controller’s instruction was interpreted differently by the captain of F-HCEV who made a left half-turn to join the start of the measurement, finding himself facing east on a path convergent with the path of F-HNAV behind him. A TCAS resolution advisory was triggered despite avoidance instructions given to both crews by the air traffic controller.
The crew of F-HCEV thus gave priority to taking the measurement, at the risk of deviating from the SID. It is also possible that the change from a navigation mode consisting in following a standard procedure using the aeroplane’s instruments to a navigation mode requiring the acquisition and tracking of ground references may have unsettled the crew.
After this first loss of separation, the air traffic controller vectored the crew of F-HCEV so that they were facing west with the path of SID 21 in front of them and instructed the crew again to visually track the ring road to join the start of the measurement. The crew of F-HCEV then confused the ring road with another motorway in front of them. This confusion may have been due to there being a similar visual reference in front of the plane when the air traffic controller gave this instruction.
The tracking of this visual reference led the crew to head north-west, taking them closer to F-HNAV again. The crew did not identify that a north-westerly track was not compatible with the tracking of the ring road. The co-pilot’s priority was to maintain distance from prohibited zone P23.
During this visual tracking phase, which lasted around one-and-a-half minutes, the crew of F-HCEV questioned the reference to be tracked but did not raise this doubt with the air traffic controllers, who, on their part, did not understand why the crew headed north-west and did not contact the crew to obtain clarification.
After the second loss of separation, the F-HCEV’s behaviour appeared to be sufficiently erratic to the air traffic controller that he asked the crew to stop the calibration and to return to land at Le Bourget airport. Following several discussions with the air traffic controllers, the crew of F-HCEV finally continued its measurement programme towards the LGL VOR.