Created Thursday, Sep 10th 2020 21:46Z, last updated Thursday, Sep 10th 2020 21:46Z
A Royal Air Maroc Boeing 737-800, registration CN-RGJ performing flight
AT-807 from London Gatwick,EN (UK) to Casablanca (Morocco) with 139 passengers and 6 crew, was accelerating for takeoff from Gatwick's runway 26L when the (automated) V1 and rotate calls did not occur. The aircraft rotated at a speed 37 knots above Vr and 120 meters/400 feet short of the runway end. The aircraft climbed out to safety and continued to Casablanca for a safe landing.
On Sep 10th 2020 the AAIB released their final bulletin concluding the probable cause of the serious incident was:
During the takeoff roll, the “V1” automatic call did not occur and the takeoff speeds were not displayed on the PFD. This led to a late rotation.
The incident shows that automatic calls may not always work as the flight crew expect and they should be ready to respond appropriately.
The AAIB summarized the sequence of events:
The co-pilot was the pilot flying for the return sector. Runway 26L was in use, with a light southerly wind and rain. The cloud was broken at 900 ft and the temperature was 6°C. The flight crew planned to depart from intersection A, using flap 1 and an assumed temperature of 55°C. They had calculated takeoff speeds of V1 - 144 kt, VR - 152 kt, and V2 - 155 kt. The commander reported that these takeoff performance figures were loaded into the FMC on stand and no changes were required during the taxi to the runway.
The aircraft entered the runway at intersection A and was cleared for takeoff. At 80 kt the commander confirmed that the airspeed indications were normal and the flight crew were next expecting to hear the aircraft announce “V1” but, this automatic call did not occur.
When the commander realised the automatic call had not occurred, he checked his PFD and saw the V speed bugs were not displayed on the speed tape. He felt “the aircraft was slow” so he allowed it to accelerate whilst he evaluated the situation. He did not recall if the speeds were still displayed on his Control Display Unit (CDU). As the end of the runway approached, he instructed the co-pilot to initiate a smooth rotation. The aircraft took off and the remainder of the flight proceeded without further incident. No aircraft caution or warning messages were seen at any stage.
The commander reported the lack of the automatic call in the aircraft’s technical log after the flight. Subsequent investigation by the operator did not find any aircraft faults. The automatic calls worked normally on the preceding and subsequent flights.
The AAIB reported the QAR data:
This showed that the nosewheel lifted off at 189 kt. The aircraft was airborne approximately 120 m prior to the end of the runway at 196 kt and 13 seconds after the planned rotation speed. Figure 1 shows the takeoff roll and highlights key speeds and heights. The data also showed the thrust was slightly increased just prior to the rotation.
The QAR records the assumed temperature and V speeds entered in the FMC, and the Mode Control Panel (MCP) selected speed (which is normally set to V2 on the ground). However, for the incident flight, the V speeds were blank. The QAR started recording after engine start and the V speeds were blank throughout the taxi and takeoff. The QAR did record an assumed temperature of 55°C1 and an MCP Selected Speed of 155 kt. The QAR files were checked, by the operator, for the previous and subsequent flights, and V speeds were recorded normally on these flights.
Takeoff Roll, speeds and heights (Graphics: AAIB):
Related Flight:
AT807,
Royal Air Maroc News
