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pilot performance. If a sinus block does not clear
shortly after landing, a physician should be consulted.
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 meteorological
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 orientation
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]
1-14
The postural system sends signals from the skin,
joints, and muscles to the brain that are interpreted
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” flying
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 certain
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 sensitive
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 initiated,
a steep spiral will develop. This is sometimes
called the graveyard spiral, because if the
pilot fails to recognize that the aircraft is in a spiral
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 contact
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 graveyard
spiral to begin all over again.
For glider pilots, prevention is the best remedy
for spatial disorientation. If the glider you are flying
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 awareness,
and learning to rely totally on your flight
instruments.
MOTION SICKNESS
Motion sickness, or airsickness, is caused by the
brain receiving conflicting messages about the
state of the body. You may experience motion
sickness during
initial flights, but it generally goes away within the
first 10 lessons. Anxiety and stress, which you
may feel as you begin flight training, can contribute
to motion sickness. Symptoms of motion
sickness include general discomfort, nausea, dizziness,
　
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