Event Details

Title:Loss of altitude following takeoff, Airbus A310, 5Y-BFT, 8 November 1998 at 2048 hrs
Micro summary:A takeoff altitude loss by this A310 triggers an investigation.
Event Time:1998-11-08 at 2048 UTC
File Name:1998-11-08-UK.pdf
Publishing Agency:Aircraft Accident Investigation Board (AAIB)
Publishing Country:United Kingdom
Report number:EW/C98/11/01
Site of event:Takeoff
Departure:London Heathrow Airport, London, England, United Kingdom
Destination:Nairobi Jomo Kenyatta International Airport, Kenya
Airplane Type(s):Airbus A310
Flight Phase:Takeoff
Operator(s):Kenya Airways
Type of flight:Revenue
Serious Injuries:0
Other Injuries:0
Executive Summary:The aircraft was departing Heathrow for Nairobi Airport on a Midhurst 3G Standard Instrument Departure (SID). It appeared to take off normally and climb to about 600 feet agl before the nose dropped and the aircraft lost height. After a few seconds the aircraft regained a normal climbing flight path and continued the departure. The visibility was reported as 10 km with few at 1,200 feet and overcast at 1,700 feet.

The manoeuvre was seen by people who reported the aircraft's abnormal behaviour to air traffic control. Later during the departure, when the flight crew were asked if they had encountered a problem after take off, the reply was "we had a problem with our landing gear, it refused to go up and we had a slight problem with the flight director". The AAIB were informed whereupon relevant radar and RTF tapes were impounded for analysis.[...]In this incident reversion to SPD - V/S - HDG took place on the runway and so when the FCC reset, it produced demands for SPD (V2) on the A/THR and zero vertical speed in pitch on the Flight Director. The commander quite rightly ignored the FD pitch-down command and because the A/THR clutches were disengaged, the thrust levers did not retard to satisfy the V2 command until the gear lever was first raised. When the lever was raised the aircraft was most probably flying faster than V2 and so the thrust levers were retarded at much the same time as the ECAM warning was triggered. It is quite probable that the during the next few seconds, both pilot focused their attention on resolving the gear problem and neither noticed the thrust levers being retarded.

With the commander holding a climbing pitch attitude instead of satisfying the FD demand for level flight, the airspeed was bound to reduce rapidly. Although thrust should have been restored when the aircraft decelerated to V2, the time required for the engines to accelerate from low power to high power may have resulted in a speed excursion below V2 from which the commander recovered by lowering the aircraft's nose and trading height for airspeed.
Learning Keywords:Operations - Altitude Excursion
Systems - Automation Design
Systems - Autopilot/Autothrottle


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