Private Pilot Flight Training and Instruction Flight Training Article Library | Back To 4VFR.COM Practice Illusions Autokinesis On a dark night, fly toward a single light. Student is to stare only at the light. After a while the light will appear to move. Student should try to keep the light in one place. Aircraft control will be lost. Updraft Have student release yoke and close eyes. Make slow entry into steep bank. Student should tell you that you are in a climb. With eyes closed have student level off. Climbing sensation should cause student to dive aircraft. A real downdraft would cause climb reaction on controls. Bank A student is asked to fly with eyes closed. If a bank is entered so slowly that it does not affect the inner ear, any abrupt correction or abrupt movement of the head will cause the pilot to re-enter the slight bank. Since the original bank did not affect the inner ear, the inner ear senses the level condition as being incorrect. Effort of pilot to correct these will only make them worse. Spiral A student is told to tip the head and close the eyes. Have student try to hold aircraft level. In a few seconds a gradual bank will occur. Over time, the bank angle will increase. There will be a gradual descent, an increase in airspeed, and an increase in bank angle. If the student pulls back the inner ear senses turning, spinning, or spiraling in a direction away from the bank. Ever increasing wrong control inputs will follow. Effort of pilot to correct will only make things worse. This is known as the graveyard spiral. Cover the attitude indicator and have student close eyes and lower head to one side. Put aircraft into a shallow constant rate turn for enough time to allow senses to stabilize (360). Have student tilt head up quickly while opening eyes. Done properly student will feel tilted to one side Attempts to correct will be exaggerated in the wrong direction. Nose up Have the student enter slow flight eyes closed, without trim , and keep his eyes closed during acceleration and recovery. This causes a somatogravic illusion. The inner ear will sense a nose-up attitude. Deceleration reverses the effect. Falling backwards Have the student enter a climb with eyes closed. After 30 seconds give yoke an abrupt forward movement to slightly nose low attitude while telling student to open eyes. Student will have sense of falling backwards. Further forward pressure only increases the effect. This illusion also has a reverse illusion causing a sensation of falling forward. Climb An in flight illusion of climb acceleration by having student close eyes while you fly straight and level at slow flight. Increase speed while maintaining straight and level. Student will have illusion of climb until opened eyes prove otherwise. Climb-dive Student eyes closed. From straight and level roll into 45-degree bank for 90-degrees of turn. Student illusion will be of climb until eyes are opened. Do same maneuver but have student open eyes when nearly straight and level. Student illusion will be that aircraft is diving. Wing-level skids with eyes closed gives tilted sensation. Steep half Dutch-roll will cause student to sense bank in opposite direction. Falling Have student close eyes and move head forward and down in 20-degree stages. Enter coordinated 30+-degree bank. Have student turn head quickly and just as quickly bring head up. Time roll recovery to coincide with heads up. Illusion is falling to direction of roll. Lowering Clouds: At 2000' and under the hood have student note the time and after one minute descend 500', after two more minutes initiate another 500' descent, after 4 minutes descend still another 500', advise that after 8 minutes he will need to descend 500' more. You are looking for the student to make a decision to turn back or land. Icing: At level cruise and under the hood. Advise the student that after initial application of C.H. the power will be reduced 1-200 rpm every minute by the instructor. The student is to make a decision as how to proceed. (Climb while able, descend to warm air, land.) False horizon Eyes closed under hood. On a dark and hazy night fly diagonally across a freeway where other lights are infrequent. Problem can be made worse by angled road lights or light patterns. Angle of lights could cause student to react with dangerous flight attitude. Pilot thinks horizon is out of level and attempts to align with illusion. In IFR conditions this will occur as you break out below a solid cloud ceiling. Eyes Closed or under hood. On a dark and hazy night fly diagonally across a freeway where other lights are infrequent. Light pattern could pilot to react with dangerous flight attitude. Elevator Illusion Caused by quick upward acceleration as in updraft. Climbing sensation causes dive reaction. Could be caused by downdraft which results in climb reaction on controls. Eyes closed. Make 90° turn with very slow bank entry from level into a 50° bank attitude. Student should have illusion of a climb. This same illusion can occur when caught in updraft. A sudden downdraft can give illusion of dive even though aircraft remains in level attitude. Coriolis Illusion Caused by abrupt head movement during a constant rate turn that has existed long enough to stabilize the inner ear. Gives sensation of motion on another axis. Attempts to correct Eyes closed, head down and tilted (Cover AI). Enter extended constant rate turn until student no longer senses turn and bank. Have student make sudden head movement to instruments and open eyes. Student should sense rotation on another axis. May react to dangerous flight attitude. Inversion Illusion Caused by abrupt change from climb to level flight. The pilot senses that he is falling backwards. The instinctive response of lowering the nose only makes the sensation worse. Eyes closed. Have pilot enter and trim for climb. When senses have had settled, have student push yoke forward to nose low attitude while opening eyes. The pilot should sense feeling of going over backwards. Leans Eyes closed. Enter a bank so slowly that it might not trigger the inner ear motion senses. Once into the bank, make an abrupt correction. The student will react to his mistaken senses then by re-entering the previously created bank and will remain there. Lighting Illusions Pilot mistakes roadways for runways. Give illusion of being quite close when lights are bright. High approach results. Low approach results when runway is approached over dark area. Don't use landing light until close to ground. The visual cues used for a normal night landing seem much the same as you get with a rapid increase in sink rate. Written by Gene Whitt Flight Training Article Library | Back To 4VFR.COM