If you pitch down too quickly from a climb to straight-and-level, you can get the illusion that you're tumbling backwards. The real danger with this that it makes you want to push the aircraft even more nose-low, which puts you into a dive attitude.
Even worse, the more you push forward, the more intense the illusion can become. How to prevent it: Slow, steady control inputs are the key when you're transitioning from a climb to straight-and-level flight. One of the most challenging things about flying in the clouds, especially in the summer, is that there's usually some turbulence as well.
Elevator illusion happens when you catch an updraft, and your plane is abruptly accelerated vertically. Even though your plane is most likely in straight-and-level flight, you feel like you need to push the nose forward, entering a dive attitude. How to prevent it: Maintain a strong instrument scan pattern in turbulence, and if the updrafts and downdrafts become so strong that you are unable to maintain altitude, fly the attitude indicator, keeping your wings straight and level. Vestibular illusions can be incredibly powerful, and it's surprising how hard it is to overcome them in flight.
One of the best ways to overcome the illusions is to trust your instruments, and keep your instrument scan pattern moving at all times. Practice helps a lot as well. Grab an instrument instructor on the next cloudy day, and go flying. Get an IFR block of airspace and practice some maneuvers in the clouds: climbs, descents, and turns. Get a feel for what the illusions are like, and then focus on overcoming them with a strong instrument scan pattern. Even if you aren't an instrument rated pilot, getting yourself into the clouds with an instructor on board is some of the most valuable flight time you can ever get.
Become a better pilot. Subscribe to get the latest videos, articles, and quizzes that make you a smarter, safer pilot. Colin is a Boldmethod co-founder, pilot and graphic artist. He's been a flight instructor at the University of North Dakota, an airline pilot on the CRJ, and has directed development of numerous commercial and military training systems.
You can reach him at colin boldmethod. To: Separate email addresses with commas. Now What? All Videos. Planes Careers. Colin Cutler Colin is a Boldmethod co-founder, pilot and graphic artist. The brain interprets the movement of the hairs to be a turn in the same direction as the canal wall.
The body correctly senses that a clockwise turn is being made. The hairs are no longer bent, and the brain receives the false impression that turning has stopped. The position of the hair cells and the resulting false sensation during a prolonged, constant clockwise turn is shown in [the figure].
A prolonged constant turn in either direction will result in the false sensation of no turn. This sends a signal to the brain that is falsely interpreted as body movement in the opposite direction.
In an attempt to correct the falsely perceived counterclockwise turn, the pilot may turn the aircraft in the original clockwise direction. It is closely associated with the vestibular system and, to a lesser degree, the visual system. Forces act upon the seated pilot in flight.
With training and experience, the pilot can easily distinguish the most distinct movements of the aircraft by the pressures of the aircraft seat against the body. The recognition of these movements has led to the term "seat-of-the-pants" flying. The book I've used for reference here, Basic Flight Physiology , is quite good. Don't let the illustrations of the light aircraft throw you. The effects are more pronounced in faster aircraft. Photo: The leans, Reinhart , Figure Click photo for a larger image.
The most common illusion, this occurs when the pilot senses a bank angle when the aircraft is actually in level flight. If she maintains the level attitude of the aircraft as she should , she will still feel compelled to align her body with the perceived vertical. In doing so, she actually leans in the opposite direction of the perceived turn Fig. For example, if during this distraction the aircraft begins to turn slowly to the right, undetected by the pilot, the canals will respond accordingly.
If she reacts to her senses rather than to the instruments, she will roll the aircraft to the right. Photo: Coriolis illusion, Reinhart , Figure Click photo for a larger image. Photo: Oculogravic illusion, Reinhart , Figure Click photo for a larger image. If that sensation is acted upon by the pilot without cross-checking instruments, he might pitch the aircraft down.
Deceleration causes a similar sensation of a nose-low attitude. During the recovery to level flight, the pilot will experience the sensation of turning in the opposite direction. The disoriented pilot may return the aircraft to its original turn. Because an aircraft tends to lose altitude in turns unless the pilot compensates for the loss in lift, the pilot may notice a loss of altitude. The absence of any sensation of turning creates the illusion of being in a level descent.
The pilot may pull back on the controls in an attempt to climb or stop the descent. This action tightens the spiral and increases the loss of altitude; hence, this illusion is referred to as a graveyard spiral. At some point, this could lead to a loss of control by the pilot.
This action creates the somatogravic illusion of being in a nose-up attitude, especially in situations without good visual references.
The disoriented pilot may push the aircraft into a nose-low or dive attitude. A rapid deceleration by quick reduction of the throttle s can have the opposite effect, with the disoriented pilot pulling the aircraft into a nose-up or stall attitude. I believe pilots who spend a lot of time in the "smooth mode" trying very hard to keep the airplane experience un-airplane like are especially susceptible to this illusion. Especially if very tired and distracted, the powerful acceleration given by many modern aircraft can cause senses to tumble.
There has been a lot of historical research verifying that this is true, but not enough thought given to survival strategies.
That is starting to change. See: Somatogravic Illusion Mitigation Strategies , below. The disoriented pilot may push the aircraft abruptly into a nose-low attitude, possibly intensifying this illusion. This is called elevator illusion. The disoriented pilot may push the aircraft into a nose-low attitude. An abrupt downward vertical acceleration, usually in a downdraft, has the opposite effect, with the disoriented pilot pulling the aircraft into a nose-up attitude.
The disoriented pilot may place the aircraft in a dangerous attitude. Photo: Autokinesis, Reinhart , Figure Click photo for a larger image. This moving reference point an illusion could lead the pilot to visually follow it. Prevention is a combination of realizing the eyes must focus on other objects at varying distances, not fixating on one target, and basic scanning.
Somatogravic illusions -- the sense that you are pitched up in a climb because of acceleration forces, or pitched down in a descent because of deceleration forces -- have been cited on at least seven large tranport aircraft accidents since January 1, , and several before then.
The problem is we sometimes lose aircraft for unknown reasons and the lack of tangible evidence places the crash in the "cause unknown" category. Photo: Somatogravic illusion, www.
Click photo for a larger image. The captain appeared to enter a descending left turn righ after takeoff, right into the ocean. Of 79 people on board, only one survived. Simply flying into a cloud renders our visual sense useless. Various G-forces during turns and climbs are confusing to our kinesthetic senses. The FAA specifically lists six illusions that can affect the vestibular sense during flight. These are common flight scenarios that will cause spatial disorientation for any kind of pilot.
Many illusions begin with the simple act of putting the aircraft into a turn. Unlike a car, when an aircraft turns, the forces remain relatively constant. But they pull the pilot down towards the ground instead of towards the outside of the turn. If a turn is entered very gradually, it is possible for the fluid in the ears to not move inside the semicircular canals. Any roll entered suddenly after that will reference the first turn as what feels like level flight to the pilot.
The result is a pilot who believes they are flying straight and level, but are actually in a turn. A turn also causes this illusion. If in a steady turn, any head movement is easily perceived by the body as a dramatic change in flight attitude. This can be a dangerous setup. If the need to move their heads to get something out of the back seat or get something off the floor, they should do so slowly and deliberately.
The foreboding name of this illusion should indicate just how deadly this particular illusion can be. If a pilot relies on their vestibular senses to get out of the turn, they may find that they unknowingly return the plane to the original turn. Since turns result in a loss of vertical lift, the aircraft will begin to descend. Not realizing that the plane is turning as well as descending, the unsuspecting pilot will pull back to control the altitude loss.
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