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Work as Thought

On 17 January 2008, a British Airways (BA) B-777 was on final approach to London Heathrow Airport’s Runway 27L after a flight from Beijing (AAIB 2010; personal communication). The aircraft was fully configured for landing and passing 1000ft on the approach, at which point the captain handed control to the flying officer (FO) in accordance with their briefing and the company procedures. It was around 12:40. The wind was blowing from the south, over Terminal 4 and the engineering hangars. The captain of a Turkish Airlines aircraft landing before the BA flight reported that it

Systems model levels 1 and 5. (Adapted from Leveson.)

FIGURE 5.1 Systems model levels 1 and 5. (Adapted from Leveson.)

was quite turbulent on the approach (personal communication). Having handed over control, the captain began scanning to see whether their assigned gate was clear. The FO had intended to disconnect the autopilot and auto-throttles at 800ft for a manual landing. Just after he took control, the FO noticed that the auto-thrust system, first, commanded an increase in thrust, and then one lever reduced power, followed soon after by the other thrust lever. Finally, the levers split, adopting different positions. The FO asked, ‘was it doing this when you were flying?’. The captain, still searching for the gate, assumed that the FO was referring to the fact that the thrust levers had been gently moving to compensate for the turbulent, gusty conditions. Nothing in the FO’s comment suggested that he might be referring to something different. At 500ft, the automatic radio altimeter call was made and the landing clearance was given. The captain called ‘stable’, and the FO responded ‘just’. This comment was sufficiently odd to cause the captain to, now, direct his attention back into the flight deck. Observing the strange condition of the thrust levers and engine displays, the captain wondered whether the aircraft warning systems had failed. The relief FO, sitting on the centre seat, commented, ‘it looks like a double engine failure’. The captain thought that it could not be a failure because the engines were still operating, just not producing sufficient output. At that point, he switched his attention to the aircraft panels to confirm that everything was in the correct position, that they had not knocked something off by accident.

Having been distracted by the behaviour of the thrust levers, the FO had not disconnected the autopilot, which was now trying to maintain the instrument landing system (ILS) glideslope. With insufficient power from the engines, the airspeed was reducing as the autopilot raised the nose of the aircraft to try to maintain the glideslope. As the speed reduced to 115 knots, the ‘Airspeed Low’ warning was triggered. The captain realised that they had to reduce drag. The aircraft was fully configured for landing, and so he briefly considered raising the landing gear. This idea was rejected because it would, initially, increase drag as the doors opened before the gear came up. He also felt that they might need the undercarriage as a protection, as it was not clear that the aircraft would make the runway. He then tried to recall the speed margins associated with different flap positions and felt that they could probably reduce the flap setting by one stage. As the flaps retracted, the captain felt that they would now clear the perimeter fence, at least, and avoid the buildings beneath the flight path. Ten seconds before touchdown the stick shaker operated and the FO pushed the nose forward, disconnecting the autopilot. The captain considered making the emergency call ‘brace for impact’ but reckoned that, as the crew were already seated for landing this might just cause panic. He also considered taking over control for the landing but recognised that handing over control so late in the flight was not sensible. In any case, the FO had almost as much time on the B-777 as he had. The aircraft touched down on the grass 330 m short of the runway and 110 m inside the boundary fence.

What is interesting in this example is that, in the space of 34 seconds, the captain, having had his attention drawn to the unusual situation, needed to address several issues: ‘why was the aircraft not giving a warning?’; ‘was the relief FO’s diagnosis correct?’; ‘had the crew accidentally deselected a system?’; ‘how can we reduce drag?’; and ‘shall I take control of the aircraft?’. There was very little interaction between the crew' members during the event. Instead, the captain was engaging with the situation, and his responses w'ere the output from the internal dialogue. At Level 1, in my hierarchical model, we are dealing with how' individuals engage with events through internal processing. It is these internal processes that result in action.

 
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