Serious incident to the Boeing 777 - 228ER registered F-GSPG operated by Air France on 02/05/2015 near Mount Cameroon (Cameroon)

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

During the flight preparation, the threats linked to the terrain on departing from Malabo, to the weather conditions and to the numerous ATC exchanges were identified and led the captain to ask the relief pilot to pay particular attention for all of the flight.
After the briefing and before departure, the crew were attentive to changes in the weather and sought up to date information several times in order to decide on the best time to leave. The information indicating that two aeroplanes had been able to land led the crew to start the flight.
Shortly after take-off, the crew turned right to join the flight plan route, making sure that the turn avoided the Malabo terrain. The two pilots had set their Navigation Displays (ND) to Weather mode which was different to the division of modes specified during the pre-flight briefing. This choice of setting may have reflected the captain’s (PM) concerns about avoiding the cumulonimbus, the en-route phase being over water and the Malabo terrain having been avoided after take-off. This choice was consistent with the threats identified during the briefing.
In order to avoid the storm cloud masses, the crew significantly departed from the flight plan route. Although the proximity of Mount Cameroon was mentioned during the briefing, the risk of dangerous proximity with this terrain was not identified.
The crew managed their flight path, preoccupied with avoiding the cloud masses and with the exchanges with the air traffic controllers. Their distance from the flight plan route increased and they drew closer to Mount Cameroon situated to the north of the planned route.
The co-pilot (PF) tried to clarify the nature of the large red returns displayed by the weather radar by temporarily setting his ND to Terrain mode. Although technically appropriate, this action was carried out for too short a period (five to six seconds) for the aeroplane radar to build a complete image of the situation. This led the PF to think that Mount Cameroon was ahead of them
When the captain (PM), a few moments later, suggested turning right to join the start of the DME arc, he thought that they were south-south-east of Mount Cameroon. This representation error was furthered by the presentation of the paper chart used to navigate.
The PF was still not sure of their exact position and the nature of the return on the right but did not verbalize this. After momentarily hesitating, he complied with the captain’s (PM) suggestion. These doubts were shown by the PF slowly entering the turn.
About 30 s after starting the turn, the EGPWS “TERRAIN AHEAD” caution and then “PULL UP” warning sounded and the two NDs changed to Terrain mode.
The activation of these warnings made the PF aware of the presence of Mount Cameroon. The reaction to the warning was quick. While carrying out the emergency manoeuvre, the PF initially kept the plane banked which led to a call from the relief pilot.
During the manoeuvre, worried about the risk of collision with another traffic, the captain (PM) observed the outside environment and asked the PF to stop climbing at FL110 and then at FL120 although the peak of Mount Cameroon was higher than these altitudes. This concern was based on the occurrence of an in-flight collision with another traffic during a simulator session followed by the captain a few months before the incident.
The air traffic controller, whose role, in particular, is to prevent collisions between aircraft, was not informed of the manoeuvre and that they had left the assigned altitude.
The climb was stopped at FL130, below the grid MORA safety altitude, and the flight was continued, without further incident, to landing. During the approach, the captain questioned the co-pilot in order to find out if he felt able to continue as PF. This request, made in a calm voice, helped the latter to remain concentrated on managing the flight to landing.