Friction
You know when your automobile begins and stops a turn. If you turn to the right your body moves toward the left and you sense pressure caused by centrifugal force. The brain tells you that a turn is in progress. The force stops when you stop turning. Your brain tells you the turn has stopped. Your vision corroborates the information.
You know when your automobile begins and stops a turn. If you turn to the right your body moves toward the left and you sense pressure caused by centrifugal force. The brain tells you that a turn is in progress. The force stops when you stop turning. Your brain tells you the turn has stopped. Your vision corroborates the information.
In flying you sense you have stopped because of friction. A little background on the structures involved before we discuss friction and its role in a coordinated turn in flight.
Sensory information of balance and position is provided by the 'vestibular system' . Tiny structures deep within our ears called 'semicircular canals' and 'otolith organs' sense changes in head position. The semicircular canals and otolith organs provide position and movement information to assist with maintenance of balance and fixation of the eyes on objects.
This connection between the inner ear and the eyes helps us keep our eyes on an object while we move our head.
These connections also have the potential to cause illusions such as the 'vection illusion' that occurs when you are stopped at traffic lights and the car next to you edges forward. The forward movement of the car next to you, if viewed in your peripheral (ambient) vision, your brain interprets as a rearward movement of your car. So strong is the illusion that you are momentarily convinced that you will roll back into the car behind you and respond by braking. In instrument conditions where visual reference is missing the visual illusion below can happen to an inexperienced pilot.
The semicircular canals contain a fluid called endolymph. The solid walls of the semicircular canals come into contact with the endolymph. There are hair-like structures that extend into the semicircular canals. When you are in straight and level flight the fluid, endolymph, and the semicircular canals are nor stimulated. If you begin a standard rate turn the endolymph lags behind the semicircular canals because of friction. The hairs extending down into the endolymph from the semicircular canals lag behind too. This stimulates the brain to detect a turn. The friction, on the endolymph, from the walls of the semicircular canals soon (20 seconds into the turn) brings the semicircular canals and the endolymph into synch (both moving at the same rate as the turn). Now the tiny hairs also are moving at the same rate and the brain interprets this as "no turn!" This causes the pilot to exit the turn. (Assume this is a non-instrument rated person) When he exits the turn the semicircular canals stop moving but the momentum of the endolymph continues for about 20 seconds. Here is where the illusion (graveyard spiral) begins. The endolymph now pushes the tiny hairs in the opposite direction. This sends a message to the pilot that he is turning in the opposite direction even though he is straight and level. He may, at this point, lean back in the direction of the original turn he was in to "feel" better or he re-enters the turn to his original bank. This illusion is so strong even ATC people can talk the pilot out of the increasingly steep bank.
Now you can understand the role of friction in flight. In a perfectly executed aircraft turn the effect of centrifugal force does not cause the brain to tell you that you are in a turn. In a car it does tell you a turn is in progress.
In the semicircular canals the friction between endolymph and the bony canals sets you up for the illusion.
Instrument training and your trust in what your instruments are telling you about the attitude of the plane will prevent you from entering the "death spiral."
Sensory information of balance and position is provided by the 'vestibular system' . Tiny structures deep within our ears called 'semicircular canals' and 'otolith organs' sense changes in head position. The semicircular canals and otolith organs provide position and movement information to assist with maintenance of balance and fixation of the eyes on objects.
This connection between the inner ear and the eyes helps us keep our eyes on an object while we move our head.
These connections also have the potential to cause illusions such as the 'vection illusion' that occurs when you are stopped at traffic lights and the car next to you edges forward. The forward movement of the car next to you, if viewed in your peripheral (ambient) vision, your brain interprets as a rearward movement of your car. So strong is the illusion that you are momentarily convinced that you will roll back into the car behind you and respond by braking. In instrument conditions where visual reference is missing the visual illusion below can happen to an inexperienced pilot.
The semicircular canals contain a fluid called endolymph. The solid walls of the semicircular canals come into contact with the endolymph. There are hair-like structures that extend into the semicircular canals. When you are in straight and level flight the fluid, endolymph, and the semicircular canals are nor stimulated. If you begin a standard rate turn the endolymph lags behind the semicircular canals because of friction. The hairs extending down into the endolymph from the semicircular canals lag behind too. This stimulates the brain to detect a turn. The friction, on the endolymph, from the walls of the semicircular canals soon (20 seconds into the turn) brings the semicircular canals and the endolymph into synch (both moving at the same rate as the turn). Now the tiny hairs also are moving at the same rate and the brain interprets this as "no turn!" This causes the pilot to exit the turn. (Assume this is a non-instrument rated person) When he exits the turn the semicircular canals stop moving but the momentum of the endolymph continues for about 20 seconds. Here is where the illusion (graveyard spiral) begins. The endolymph now pushes the tiny hairs in the opposite direction. This sends a message to the pilot that he is turning in the opposite direction even though he is straight and level. He may, at this point, lean back in the direction of the original turn he was in to "feel" better or he re-enters the turn to his original bank. This illusion is so strong even ATC people can talk the pilot out of the increasingly steep bank.
Now you can understand the role of friction in flight. In a perfectly executed aircraft turn the effect of centrifugal force does not cause the brain to tell you that you are in a turn. In a car it does tell you a turn is in progress.
In the semicircular canals the friction between endolymph and the bony canals sets you up for the illusion.
Instrument training and your trust in what your instruments are telling you about the attitude of the plane will prevent you from entering the "death spiral."
