Recognition of Inadvertent Entry into IMC VFR pilots should assume they are in IMC conditions anytime they are unable to maintain aircraft attitude control by reference to the natural horizon, regardless of the circumstances or the prevailing weather conditions. In addition, a VFR pilot should accept that they are effectively in IMC anytime they are unable to navigate or establish geographical position by visual reference to landmarks on the surface unless they have planned and are legally able to operate “VFR on top”. Such situations must be accepted by the pilot involved as a genuine emergency, requiring immediate action.
Pilots must understand that unless they are trained, qualified, and current in the control of an airplane solely by reference to flight instruments, they will not be able to do so for any length of time.
Many hours of VFR flying using the attitude indicator as a reference for airplane control in conditions of low visibility may give a pilot a false sense of security based on an overestimation of his personal ability to control the airplane solely by reference to instruments. In visual meteorological conditions, even though the pilot may think he/she is controlling the airplane by instrument reference, the pilot receives an impression of the natural horizon and may subconsciously rely on it more than the cockpit attitude indicator. If all vestiges of the natural horizon subsequently disappear, the untrained instrument pilot is likely to become spatially disorientated, which is likely to lead to loss of control.
Maintaining Control of the Aeroplane Once the pilot recognises that they have entered IMC conditions, they should understand that the only way to control the airplane safely is by using and trusting the flight instruments. The pilot should make a firm decision to change from visual reference to instrument flight if possible before visual references are completely lost. The pilot should initially concentrate on the attitude indicator and select and maintain the correct attitude for straight and level flight. Once this is achieved, the pilot must concentrate on the AI limiting glances away from the AI for essential checks only – e.g. the RPM to confirm appropriate power is set. It is important not to try to mix searching for external clues as to the attitude of the aircraft with instrument flying. The pilot should understand that the most important concern is to keep the wings level. An uncontrolled bank may lead to spiral dive and loss of control. The pilot must believe what the AI shows about the aeroplane’s attitude regardless of sensory input. vestibular organs (in the inner ear) is unreliable in flight when unaccompanied by relevant visual information. The sensory areas of the inner ear cannot detect slight changes in angular acceleration, nor can they accurately sense changes that occur at a uniform rate over a period. On the other hand, false sensations are often generated due simply to movements of the head and may lead the pilot to believe the attitude of the airplane has changed when, in fact, it has not. If the pilot has managed to achieve straight, stable flight, do not make any control movement unless the AI shows that it is necessary, and even then make only small control inputs. Other receptors found throughout the body, known as somatosensory receptors (commonly referred to giving feeling and G forces) located all over the skin, bones, joints, skeletal muscles, internal organs and the parts of the cardiovascular system, will also be providing information to the brain. This information can be in conflict with the visual and vestibular senses. These false or conflicting sensations can result in the pilot experiencing spatial disorientation even when in VMC. Particularly during flight in poor visibility or in cloud all this can be catastrophic. The outcome may develop into what is often called a “graveyard spiral”. This name is self explanatory.
There is chilling audio from ATC where a VFR pilot wants to descend through a deck a mere 1000' thick he lost control and screamed 'Help me, Help ME as he augured in through 3500 of CAVU.
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