INSIDE STORY FURTHER ADVICE
■ Know your limitations; test them with caution
■ The feel of the aircraft won’t tell you what it is doing
■ Trust your instruments; you will need an exceptionally good reason not to do so
■ Anticipate loss of external vision by early transfer to instruments
■ First fly the aircraft; distraction can lead to unrecognised disorientation
■ Maintain logical thinking; avoid an impulsive control response to an unexpected attitude error
■ Remain physically fit ■ Beware fatigue ■ Alcohol and flying don’t mix
attitude that doesn’t conform to the pilot’s current perception. The interpretation of a conventional
‘moving horizon’ attitude indicator is not intuitive. In cloud, the mountings of the attitude ball appear fixed, as does the interior of the cockpit, and the attitude ball shows a horizon that appears to move with changes in roll or pitch attitude of the aircraft. Horizons don’t move, but that is the perception. When an unintended roll attitude
becomes evident on instruments, the surprise might give rise to an impulsive reaction that leads the pilot to do the opposite of what is required – the roll reversal error. This error was responsible for an accident involving a 737 aircraft on the climb out at night from Sharm el Sheikh. The pilot, attempting to correct for an unanticipated 30 degree angle of bank, added a further 30 degrees of bank in the same direction with fatal consequences. An impulsive response to an apparently
abnormal aircraft attitude was the prelude to a cargo aircraft about to start its descent at night into an airport in northern Sweden. A fault in the inertial navigation system had given the handling pilot a false indication of the aircraft being 30 degrees nose up, though there was no indication of any change in the aircraft altitude or airspeed. The abrupt stick forward action of the pilot bunted the aircraft to a state of weightlessness and objects started to float free in the cockpit. The co-pilot was so unnerved by the event that despite having fully functioning instruments on his side
26 CLUED UP Summer 2018
of the cockpit he was never able to assist the captain or take control and restore level flight. Within a minute the aircraft lost 30,000ft in altitude and crashed. There is seldom a crisis in the air that does not benefit from a few seconds delay to fully take stock of the situation before responding to it. This accident should not encourage
pilots to disbelieve their instruments. They will almost always be correct when the pilot is wrong. Believe your instruments and stick with them until there is an unambiguous view of the outside world. But note the plural – ‘instruments’. The accident pilot had become fixated on the one faulty instrument, struggling to make it read correctly, to the exclusion of the many other sources of correct information.
THE URGE TO PRESS ON Many light aircraft pilots will have experienced the following scenario: It had been a good (alcohol-free) lunch
following a land-away in northern France and it was time to make the return journey. As the English coastline appeared, so did the low cloud. ‘Am I going to make it back to base, or should I divert? That will be awkward, the aircraft will be in the wrong place, my car will still be at base and I have another engagement this evening. Must press on. I know the visual flight rules, but it might just be okay.’ A pilot employed to fly a privately
owned helicopter can find himself under a different pressure to press on. If the boss demands that we fly, it is not always easy to refuse to take off because of the weather.
■ Do not fly if you cannot leave your worries behind
It was this scenario that contributed to a fatal crash near Ipswich in 2014. The owner was late in arriving for the flight and fog and low cloud were increasing. Almost immediately after take-off the aircraft was enveloped in cloud. It remained airborne for less than a minute before it emerged from cloud in a nose down attitude and impacted the ground, killing all aboard. Though the final event in any accident
may involve disorientation, there is almost always a preceding sequence of errors or misjudgements. Recognising and breaking that chain can prevent a fatal outcome.
Dr Rollin Stott, MA MBBChir MRCP DAvMed, qualified in medicine from Cambridge University and studied engineering applied to medicine at Imperial College. After a variety of hospital appointments he joined the RAF Institute of Aviation Medicine working on the effects of motion on man, in particular, spatial disorientation in flight, airsickness in trainee aircrew, and the effects of whole body vibration. He has written many papers and is a contributing author on these subjects for the textbook ‘Ernsting’s Aviation Medicine’. He currently works as a trusted expert for QinetiQ plc and is an Honorary Senior Lecturer at King’s College London. He has been a CAA Aeromedical Examiner since 1990.
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