3 An Airbus A320 would not turn left no matter what the pilot tried. Eventually they made an emergency landing. Fortunately, no one was hurt. The cause of the near-disaster was that engineers had forgotten to reactivate four of the five spoilers on the right wing that help the plane to turn. The investigation blamed ‘a chain of human errors’, by the engineers and by the pilots who had failed to notice the problem before take-off. The A320 is a ‘fly-by-wire’ aircraft where computer-controlled electrical impulses activate the hydraulically powered spoilers and surfaces, which control the movement of the plane. When the aircraft went for repair to a damaged flap, the engineers had put the spoilers into ‘maintenance mode’ to block them off from the controls. They had then forgotten to reactivate them. According to the official report, the engineers were not guilty of ‘simple acts of neglect or ignorance. Their approach implied that they believed there were benefits to the organisation if they could successfully deliver the aircraft on time. With more complex aircraft, it is no longer possible for maintenance staff to understand all the consequences of any deviation. The avoidance of future accidents with high-technology aircraft depends on total compliance. If a check has been carried out numerous times without any fault being present, it is human nature to anticipate no fault when next the check is carried out’.

(a) Why should fly-by-wire aircraft pose a more complex maintenance problem than conventional aircraft, which have a physical link between the control and the flaps?

(b) I f you were the accident investigator, what questions would you want to ask in order to understand why this failure occurred?