Aeromedical Factors

night-flight currency and proficiency. Include cross- is. [Figure 17-7] The pilot who does not recognize this country and local operations at various airfields. illusion will fly a lower approach. Downsloping runways and downsloping approach terrain can have the opposite effect. 5. Ensure that when outside visual references are used, they are reliable, fixed points on the Earth’s surface. Featureless Terrain Illusion 6. Avoid sudden head movement, particularly during An absence of surrounding ground features, as in an takeoffs, turns, and approaches to landing. overwater approach over darkened areas or terrain made 7. Be physically tuned for flight into reduced visibility. featureless by snow, can create an illusion that the aircraft is Ensure proper rest, adequate diet, and, if flying at at a higher altitude than it actually is. This illusion, sometimes night, allow for night adaptation. Remember that referred to as the “black hole approach,” causes pilots to fly illness, medication, alcohol, fatigue, sleep loss, and a lower approach than is desired. mild hypoxia are likely to increase susceptibility to spatial disorientation. Water Refraction 8. Most importantly, become proficient in the use of Rain on the windscreen can create an illusion of being at a flight instruments and rely upon them. Trust the higher altitude due to the horizon appearing lower than it is. instruments and disregard your sensory perceptions. This can result in the pilot flying a lower approach. The sensations that lead to illusions during instrument Haze flight conditions are normal perceptions experienced by Atmospheric haze can create an illusion of being at a greater pilots. These undesirable sensations cannot be completely distance and height from the runway. As a result, the pilot prevented, but through training and awareness, pilots can has a tendency to be low on the approach. Conversely, ignore or suppress them by developing absolute reliance extremely clear air (clear bright conditions of a high attitude on the flight instruments. As pilots gain proficiency in airport) can give the pilot the illusion of being closer than instrument flying, they become less susceptible to these he or she actually is, resulting in a high approach that may illusions and their effects. result in an overshoot or go around. The diffusion of light due to water particles on the windshield can adversely affect Optical Illusions depth perception. The lights and terrain features normally Of the senses, vision is the most important for safe flight. used to gauge height during landing become less effective However, various terrain features and atmospheric conditions for the pilot. can create optical illusions. These illusions are primarily associated with landing. Since pilots must transition from Fog reliance on instruments to visual cues outside the flight Flying into fog can create an illusion of pitching up. Pilots deck for landing at the end of an instrument approach, it who do not recognize this illusion often steepen the approach is imperative that they be aware of the potential problems abruptly. associated with these illusions and take appropriate corrective action. The major illusions leading to landing errors are Ground Lighting Illusions described below. Lights along a straight path, such as a road or lights on moving trains, can be mistaken for runway and approach lights. Bright Runway Width Illusion runway and approach lighting systems, especially where A narrower-than-usual runway can create an illusion that the few lights illuminate the surrounding terrain, may create the aircraft is at a higher altitude than it actually is, especially illusion of less distance to the runway. The pilot who does when runway length-to-width relationships are comparable. not recognize this illusion will often fly a higher approach. [Figure 17-7] The pilot who does not recognize this illusion will fly a lower approach, with the risk of striking objects How To Prevent Landing Errors Due to Optical along the approach path or landing short. A wider-than- Illusions usual runway can have the opposite effect with the risk of To prevent these illusions and their potentially hazardous the pilot leveling out the aircraft high and landing hard or consequences, pilots can: overshooting the runway. 1. Anticipate the possibility of visual illusions during approaches to unfamiliar airports, particularly at night Runway and Terrain Slopes Illusion or in adverse weather conditions. Consult airport An upsloping runway, upsloping terrain, or both can create an illusion that the aircraft is at a higher altitude than it actually 17-10