The CFIT/LOC Risk
Whilst there are many situations in which these illusions can occur, one of the most likely, and certainly the most dangerous, is when the positive changes in acceleration, which accompany the initiation of a go around or the transition to initial climb after take off, are occurring. In both cases, the consequences can rapidly lead to CFIT if the condition is not recognised or to LOC if the situation is recognised but the complexities of recovery are mishandled.
Flap and gear retraction and changes in thrust whilst seeking to achieve and maintain a specific climbing flight path involve considerable changes in acceleration which, in turn, are conducive to a somatogravic illusion. As the inputs to establish sustained climb take effect, a perception of excessive pitch-up may occur. This can lead to a fear that the stalling angle of attack may be approaching. The instinctive reaction to this is to push the nose down in the belief that a reduction in pitch to a more “normal” climb angle is being achieved. If the aircraft is banked, either intentionally or unknowingly, at the same time, the perception of angular acceleration may be underestimated because of a somatogyral illusion, leading to an instinctive tendency to increase the angle of bank.
Sometimes, the strength of these illusions may be so intense that even a conscious cross reference to the flight instruments, which do not validate the perception, may be insufficient to lead to a corrective input to the flight controls by the affected individual. However, in a multi-crew aircraft, it is uncommon for both pilots to be similarly affected at the same time and effective monitoring becomes critical if the risk of an unintended excursion is to be avoided.
