An archaic definition of
disorientation literally meant "difficulty in facing the east." To the
pilot, it more often means "Which way is up?" Disorientation, or
vertigo, is actually a state of temporary spatial confusion resulting
from misleading information sent to the brain by various sensory organs.
The body's elaborate navigational system was superbly designed for
locomotion on the ground at a normal gait, but in an aircraft, during
sudden acceleration or radial flight, it can trick you.
The most difficult
adjustment that you must make as you acquire flying skill is a
willingness to believe that, under certain conditions, your senses can
be wrong. When you are seated on an unstable moving platform at altitude
(and your vision is cut off from the earth, horizon, or other fixed
reference) and you are exposed to certain angular accelerations or
centrifugal forces (which you cannot distinguish from gravity forces),
you are susceptible to innumerable confusing, disorienting experiences.
In a level turn, you may
think you are in straight flight or climbing. In a coordinated, banked
turn you may believe yourself to be in straight and level flight. In
recovery from a level turn, you may feel as though you are diving. In a
left turn - if you suddenly bend your head forward - you may think you
are falling to the left.
sensations are due primarily to misinterpretation of messages sent to
the brain by the two primary sensory organs: (1) the semicircular canals
of the inner ear, and (2) groups of pressure-sensitive nerve endings
located mainly in the muscles and tendons. These organs tell you where
you are in relation to the ground, your normal environment. When your
eyes are open and your feet are on the ground, they serve you well. You
have little trouble deciding which direction is up or down. In an
airplane, though, these organs may send your brain inaccurate reports.
The semicircular canals
in each inner ear consist of tiny hollow tubes bent to form a
half-circle. Each tube (canal) is positioned approximately at a right
angle to the other two canals and each is filled with a fluid. At the
outer end of each there is an expended portion containing a mass of fine
hairs. Acceleration of the inner ear assembly in any direction sets the
fluid in motion within the appropriate canal causing the hairs to
deflect. This, in turn, stimulates nerve endings and sends directional
messages to the brain. Operating as a unit, this detection system forms
a device by which we can readily identify "yaw," "pitch," and "roll."
With this perfect
arrangement, it appears that you should never have the least bit of
difficulty ascertaining your direction and attitude. However, as in all
complex systems, there is a certain amount of built-in error. In
aviation, we sometimes refer to this type of a problem as "instrument
lag." If the rate of directional change is quite small - and not
confirmed by the eyes - the change will be virtually undetectable and
you probably will not sense any motion whatsoever.
In straight and level
flight the fluid in the semicircular canals is resting and the little
hair detectors alert and ready for action. Any directional change of
your airplane will cause a reaction in the proper canal and signal to
the brain which direction the aircraft has moved.
As you enter a
constant-rate turn (such as a standard rate 3 degree/second turn), the
system goes to work; the hairs bend over and the proper signal travels
to the brain indicating the direction of turning. Continuing the same
turn for about 30 to 45 seconds will allow the fluid in the canal to
catch up with the pilot and aircraft and the hairs will be pushed back
to their upright position.
Here's where trouble
begins! Inside the airplane, if you are unable to see the ground and
establish visual reference you are just seconds away from the famous
graveyard spiral. You're in a turn but your inner ear machinery tells
you that you're straight and level. Now, as the airspeed builds up in
the turn you may think you are in a level dive and pull back on the
control column. Increased back pressure on the controls will only
tighten the turn and cause structural failure or a curving flight path
into the ground. But suppose, by either a glimpse of the horizon or a
recall of some "needle-ball-airspeed" technique, you are able to get the
airplane squared away again to straight and level flight.
The fluid, which
continues to turn while you are returning to level flight, begins to
creep back to neutral after you level the airplane. Because of its
momentum, the fluid continues to flow after the canal has come to rest -
bending the hairs along with it. You really are straight now, but you
have the sensation of turning in the OPPOSITE direction from which you
have just recovered. You instinctively bank away from the imaginary turn
- and the cycle starts all over again.
training, the chances of maintaining normal aircraft attitude in limited
visibility are extremely rare. Repeated small control movements may
eventually create a sensation of gradual turning. You may misinterpret
the degree of bank and have a false impression of tilting when in a skid
or a slip.
occurs most often in instrument conditions created by rain, fog, clouds,
smoke or dark nights. It is aggravated by other factors such as lack of
recent instrument experience or training, attempts to mix VFR and IFR,
unfamiliarity with the aircraft or flight situation, fear or worry, and
excessive head movements.
You can overcome the
effects of vertigo by relying upon your aircraft's instruments. Read
your instruments! They are the best insurance you will ever have.
Remember, though, that the time required to shift from VFR to IFR may be
long enough for the aircraft to enter a dangerous attitude.
Bear in mind that
vertigo can occur ANYTIME that the outside visual reference is
temporarily lost - during map reading, changing a radio channel,
searching for an approach plate, fuel managing, computing a navigational
problem or whatever else you might need to do inside the cockpit. Nearly
all experienced pilots have had a brush with vertigo, usually minor and
of short duration. It CAN be disastrous, however, "Pilot error,"
resulting from vertigo, has been identified beyond any doubt as the
direct contributing cause of many accidents.
To become familiar with
disorientation symptoms, ask your AME or nearest GADO (General Aviation
District Office) specialist to arrange a brief demonstration in a Barany
(rotating) chair. This will quickly and safely show you how overwhelming
vertigo can be. It would be to your advantage to attend any of the FAA
Accident Prevention Programs which are presented frequently throughout
the country. You GADO inspector can advise you of the time and location
of the next program in your vicinity. Disorientation is also included in
the FAA-coordinated Physiological Training Course. Complete information
regarding this training may be obtained by contacting any of the
addresses listed in the back of this handbook.
The danger of vertigo
may be reduced by:
1. Understanding the nature and causes of the condition.
2. Avoiding, if possible, the flight conditions which tend to
3. Obtaining instrument flight instruction and maintaining
4. Having faith in the instruments rather than taking a chance on
the sensory organs.
5. Remembering that it can happen to ANYONE!
Finally, you should be
constantly aware of the danger in shifting between the instrument panel
and the exterior visual field when the later is poorly structured or
obscured. Avoid sudden head movements, particularly when the aircraft is
changing attitude. Don't fixate too long on the instruments. And, most
important, when your senses seem to disagree with the instruments, trust
the instruments - they may save your life.