INSIDE STORY
from landfall when the pilot appeared to become increasingly uncertain about the aircraft’s roll attitude; the haze and gloom had deprived him of any useful external horizon. He had received a few hours of instrument training but was not IMC rated. The Saratoga began to descend. It entered a prolonged turn, first to the left then to the right. In the turn the descent rate rapidly increased and the aircraft flew into the sea with an estimated 30o nose down and 125º of bank. There were no survivors. The pilot had, as you’ve probably
already worked out, become disorientated. While there were several errors and misjudgements that led up to the tragedy, the final event was an increasing overbank leading to a spiral dive and rapid descent – the so called graveyard spiral. If you have never experienced this it
might come as a surprise to learn that despite the increasingly abnormal attitude of the aircraft, the pilot is likely to have continued to feel that the wings were level and there would have been no sense of the rotation or nose down attitude that a spiral dive might lead one to expect. This is as much the result of the
deceptiveness of the force environment of the aircraft as any limitation of the pilot’s senses. A pilot manoeuvring in cloud at night who inadvertently allowed his aircraft to get into a similar attitude was only alerted to his predicament and able to recover by seeing street lights through the window in the cockpit roof… You might know the well worn dictum
in aviation — ‘you cannot fly an aircraft by the seat of the pants’ — in the absence of external visual information or the correct interpretation of attitude instruments, the feel of the aircraft will deceive you. More than likely it will falsely reassure you.
THE VISUAL ENVIRONMENT On the ground we derive a sense of orientation from the earth-fixed world that surrounds us. The visual scene normally provides a wealth of sensory information to keep us orientated; there is much redundancy. From the moment an aircraft leaves the ground there is a gradual reduction in the visual detail. The earthbound world becomes increasingly remote and the pilot is more and more dependent on a clear visual horizon to maintain the desired attitude. Problems arise when the true horizon is obscured by haze. Likewise, flying over snow or a grey sea, the terrain can merge
22 CLUED UP Summer 2018
with an overcast sky leaving no clear horizon. Worse, the visual scene can create false horizons such as a low cloudbank, or, at night, lines of light from street lights or a lit coastline. If the aircraft is aligned with such an oblique horizon, the pilot cannot rely on the feel of the aircraft to indicate the inappropriate roll attitude.
THE FORCE ENVIRONMENT For most of the time an aircraft will tend to feel level whatever its actual attitude. With one wing low an aircraft will begin to turn. Every airline passenger can confirm that when the aircraft is in a banked turn everything feels level – the coffee cups stay
Figure 1
Figure 1 The environmental and some of pilot-related factors that can lead to disorientation in flight.
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