Visual Illusions for Pilots In Flight – Video Transcript
Good day viewers. My name is Alex Johnson. I’m a former student with AeroGuard and currently I’m an instructor, a check instructor, and a training manager operating out of our Punta Gorda campus in Florida. I’m here today to talk to you about why vision is important in flight specifically relating to the illusions that can be experienced and how we can mitigate some of those illusions.
There are many illusions we must be concerned about which can be experienced in flight. Some can lead to spatial disorientation; others can lead to landing errors. Illusions rank among the most common factors cited as contributing to fatal aircraft accidents. Various complex motions and forces and certain visual scenes encountered in flight can create illusions of motion and position. Spatial disorientation from these illusions can be prevented only by visual reference to reliable fixed points on the ground or to flight instruments. I’ll be using the acronym ICE FLAGS to cover these illusions going over Inversion, Coriolis force, Elevator illusion, False horizon, the Leans, Autokinesis, Graveyard spiral and Somatogravic illusion.
We’ll start with the inversion illusion. An abrupt change from climb to straight and level flight can create the illusion of tumbling backwards. The disoriented pilot will push the aircraft abruptly into a nose low attitude, possibly intensifying this illusion.
Coriolis illusion is next, where an abrupt head movement and a prolonged constant rate turn that has stimulated the motion sensing system can create the illusion of rotation or movement in an entirely different axis. The disoriented pilot will maneuver the aircraft into a dangerous attitude in an attempt to stop this rotation. This most overwhelming of all illusions in flight may be prevented by not making sudden extreme head movements, particularly while making prolonged constant rate turns under IFR conditions.
Next, we’ll go over elevator illusion, where an abrupt upward vertical acceleration, usually by an updraft, can create the illusion of being in a climb. The disoriented pilot will push the aircraft into a nose low attitude. An abrupt vertical downward acceleration, usually by a downdraft, has the opposite effect with the disoriented pilot pulling the aircraft into a nose-high attitude.
Next, we’ll go over false horizon, where sloping cloud formations and obscure horizon (a dark scene spread with ground lights and stars and certain geometric patterns of ground light) can create the illusion of not being aligned correctly with the actual horizon. The disoriented pilot will place the aircraft into a dangerous attitude.
Next, we’ll go over the leans, where an abrupt correction of banked attitude which has been entered too slowly to stimulate the motion sensing system in the inner ear, can create the illusion of banking in the opposite direction. The disoriented pilot will roll the aircraft back to its original dangerous attitude or if level flight is maintained, will feel compelled to lean the perceived vertical plane until the illusion subsides.
Next, we’ll cover autokinesis, which is usually a night illusion. In the dark, a static light will appear to move about when stared at for many seconds. The disoriented pilot will lose control of the aircraft in an attempt to line it with that moving light.
Next, we’ll cover graveyard spiral, which is an observed loss of altitude during a coordinated constant rate turn that ceased stimulating the motion sensing system, can create the illusion of being in a descent with the wings level. The disoriented pilot will pull back on the controls tightening the spiral and increasing the loss of altitude.
Finally, we’ll cover somatographic illusion, where simply a rapid acceleration during takeoff can create the illusion of being in a nose-up attitude. The disoriented pilot will push the aircraft into a nose low or dive attitude. A rapid deceleration on the other hand, by a quick reduction of the throttle, can have the opposite effect with the disoriented pilot pulling the aircraft into a nose-up or stall attitude.
Various surface features and atmospheric conditions encountered in landing can create illusions of incorrect height above and distance from the runway threshold. Landing errors from these illusions can be prevented by anticipating them during approaches, [by] aerial visual inspection of unfamiliar airports before landing using an electronic glide slope or vasey systems when available and [by] maintaining optimum proficiency in landing procedures. I’ll cover a few of these illusions now.
We’ll start with the runway width illusion. A narrower than usual runway can create the illusion that the aircraft is in a higher altitude than it actually is. The pilot who does not recognize this illusion will fly a lower approach with the risk of striking objects along the approach path or landing short. A wider than usual runway will have the opposite effect with the risk of leveling out high and landing hard or overshooting the runway.
Next, we’ll cover runway and terrain slope illusion, which an upsloping runway, upsloping terrain, or both can create the illusion that the aircraft is at a higher altitude than it actually is. The pilot who does not recognize this will again fly a lower approach. A down sloping runway, down sloping terrain, or both can have the opposite effect.
Next, we’ll cover featureless terrain illusion which sometimes you’ll hear as the black hole approach. An absence of ground features as when landing over water, darkened areas, and terrain made featureless by snow can create the illusion that the aircraft is at a higher altitude than it actually is. The pilot who does not recognize this will again fly a lower approach.
Rain on the windscreen or lights along a straight path such as a road and even moving lighting can create different atmospheric or ground lighting illusions as well, which must also be considered.
Tips & Tricks
Pilots should also be familiar with the following tips and tricks to make good judgment, keep our heads up looking outside and reduce the possibility of mid-air collisions.
First, we must determine our relative altitude. Use the horizon as a reference point. If the other aircraft is above the horizon, it’s probably on a higher flight path. If the aircraft appears to be below the horizon it is probably flying at a lower altitude.
Next, we must take appropriate action. Pilots should be familiar with the rules of the right-of-way so if an aircraft is on an obvious collision course, one can take immediate evasive action, preferably in compliance with the federal aviation regulations.
Next, we must consider multiple threats. The decision to climb, descend, or turn is a matter of personal judgment, but one should anticipate that the other pilot may also be making a quick maneuver. Watch the other aircraft during the maneuver and begin your scan again immediately since there may be other aircraft in the area.
Next, we need to be aware of collision course targets. Any aircraft that appears to have no relative motion and stays in one scan quadrant is likely to be on a collision course. Also, if the target shows no lateral or vertical motion but increases in size, you need to take evasive action immediately.
Next, we need to recognize high hazard areas. Be extra vigilant in busy areas or airspace where aircraft tend to cluster. Remember, most collisions occur during days when the weather is good. Being in a radar environment still requires vigilance to avoid collisions. Remember, it is the pilot’s number one responsibility to see and avoid other aircraft.
Next, we have cockpit management we need to be aware of. Studying maps, checklists, and manuals before flight with other pre-flight planning, for example, noting radio frequencies and organizing cockpit materials, can reduce the amount of time required to look at those items during flight, permitting more time to keep our heads up and our scan going.
Next, we have windshield and visibility conditions where smoke, haze, dust, rain and flying towards the sun can also greatly reduce the ability to detect targets. Visual obstructions in the cockpit can also be an issue. Pilots may need to move their heads around blind spots caused by fixed aircraft structures such as doorposts, wings, or etc. For example, on our low wing piper archers, you may need to dip the wing a little bit to see a visual reference below you.
Finally, we have our lights on. During day or night, use of exterior lights can greatly increase the visibility of an aircraft and remember, at night we must keep our interior lights low.
We’ve covered a lot of information in this presentation and I hope it’s reinforced how important our vision is when it comes to the execution of a safe flight, not only by being mindful of how our vision is impacted by physiological and atmospheric conditions, but the illusions that can happen as a result and what we can do to mitigate and correct those.
Thank you so much for watching today and I’m glad you took the time to enjoy this video. Please check out our other videos and like and subscribe.