|
Introduction to Glider Flying > Introduction to Glider Flying > Medical Factors Associated with Glider Flying > Spatial Disorientation
Spatial disorientation specifically refers
to the lack of orientation with regard to position in space
and to other objects. Orientation is maintained through the
body’s sensory organs in three areas: visual, vestibular,
and postural. The eyes maintain visual orientation; the motion
sensing system in the inner ear maintains vestibular orientation;
and the nerves in the skin, joints, and muscles of the body
maintain postural orientation.
During flight in visual meteorological conditions
(VMC), the eyes are the major orientation source and usually
prevail over false sensations from o t h e r sensory systems.
When these visual cues are taken away, as they are in instrument
meteorolog-ical conditions (IMC), false sensations can cause
the pilot to quickly become disoriented.
The vestibular system in the inner ear allows
you to sense movement and determine your orienta-tion in the
surrounding environment. In both the left and right inner ear,
three semi-circular canals are positioned at approximate right
angles to each other. Each canal is filled with fluid and has
a section full of fine hairs. Acceleration of the inner ear
in any direction causes the tiny hairs to deflect, which in
turn stimulates nerve impulses, sending messages to the brain.
The vestibular nerve transmits the impulses from the utricle,
saccule, and semicircular canals to the brain to interpret motion.
[Figure 1-13]
The postural system sends signals from the
skin, joints, and muscles to the brain that are inter-preted
in relation to the Earth’s gravitational pull. These signals
determine posture. Inputs from each movement update the body’s
position to the brain on a constant basis. “Seat of the
pants” fly-ing is largely dependent upon these signals.
Used in conjunction with visual and vestibular clues, these
sensations can be fairly reliable. However, because of the forces
acting upon the body in cer-tain flight situations, many false
sensations can occur due to acceleration forces overpowering
gravity.
Under normal flight conditions, when you have
reference to the horizon and ground, these sen-sitive hairs
allow you to identify the pitch, roll, and yaw movement of the
glider. When you become disoriented and lose visual reference
to the horizon and ground, the sensory system in your inner
ear is no longer reliable. Lacking visual reference to the ground,
your vestibular system may lead you to believe you are in level
flight, when, in reality, you are in a turn. As the airspeed
increases, you may experience a postural sensation of a level
dive and pull back on the stick. This increased back-pressure
on the control stick tightens the turn and creates ever-increasing
g-loads. If recovery is not initi-ated, a steep spiral will
develop. This is some-times called the graveyard spiral, because
if the pilot fails to recognize that the aircraft is in a spi-ral
and fails to return the aircraft to wings-level flight, the
aircraft will eventually strike the ground. If the horizon becomes
visible again, you will have an opportunity to return the glider
to straight-and-level flight. Continued visual con-tact with
the horizon will allow you to maintain straight-and-level flight.
However, if you lose contact with the horizon again, your inner
ear may fool you into thinking you have started a bank in the
other direction, causing the grave-yard spiral to begin all
over again.
For glider pilots, prevention is the best remedy
for spatial disorientation. If the glider you are fly-ing is
not equipped for instrument flight, and you do not have many
hours of training in controlling the glider by reference to
instruments, you should avoid flight in reduced visibility or
at night when the horizon is not visible. You can reduce your
susceptibility to disorienting illusions through training and
aware-ness, and learning to rely totally on your flight instruments.
|
