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connect the throat with the middle
ear; their purpose is to equalise air
pressure. When you swallow, the
tubes open, allowing air to enter,
which is why swallowing helps to
clear the ears when changing
altitude. Blocked Eustachian tubes
can be responsible for split
eardrums, due to the inability to
equalise pressure. Since the eardrum
takes around 6 weeks to heal, the
best solution is not to go flying with
a cold, but commercial pressures
don't always allow this. If you have
to, make sure you use a decongestant
with no side effects.
The audible range of the human ear
is 20 Hz to 20 KHz.
Blocked Sinuses
Although associated with the
nose, the sinuses are actually
hollow spaces or cavities inside
the head surrounding the base
of the nose and the eye sockets.
Amongst other things, they act
as sound boxes for the voice.
Being hollow, they provide
structural strength whilst
keeping the head light; there are
normally between 15-20.
Blockages arise from fluid that
can't escape through the narrow
passages—pain results from
fluid pressure. Blocked sinuses
can also be responsible for
severe headaches.
Deafness
This can arise from many
causes; in aviation, high-tone
deafness from sustained
exposure to jet engines is very
common. Hearing actually
depends on the proper working
of the eighth cranial nerve, which
carries signals from the inner
ear to the brain. Obviously, if
this gets damaged, deafness
results. The nerve doesn't have
to be severed, though;
deterioration will occur if you
don't get enough Vitamin BComplex
(deafness is a
symptom of beriberi or pellagra,
for example, from Vitamin B
deficiency).
You can recover from some
deafness, such as that caused by
illness, but not that caused by
damage to the fibres in the fluid.
Disorientation
This refers to a loss of your
bearings in relation to position
or movement. The "leans" is the
classic case, already mentioned.
To combat them, close your
eyes and shake your head
vigorously from side to side for
a couple of seconds, which will
topple the semi-circular canals.
Motion Sickness usually
happens because of a mismatch
between sight, feel and the
semicircular canals, giving
unfamiliar real or apparent
motion (e. g. the leans).
Medication can have
unwelcome side effects,
particularly on performance,
which are normally not
acceptable for flight crews.
During acceleration, it's possible
to get the impression of
pitching up, making you want to
push the nose down (it's more
pronounced at night going into
a black hole from a well-lit
area). You get a pitch-down
illusion from deceleration. The
252 Canadian Private Pilot Studies
danger here is that lowering the
gear or flaps causes the machine
to slow down, which makes you
think you are pitching down and
want to bring the nose up,
which could cause a stall at the
wrong moment on approach.
Respiratory System
Consists of the lungs, oronasal
passage, pharynx, larynx, trachea,
bronchi, bronchioles and alveoli:
Air is drawn into the lungs, from
where oxygen is diffused into the
haemoglobin in the blood under
pressure, which carries it to the
tissues of the body, especially the
brain, the most sensitive to lack of it.
Blood is pumped around by the
heart. Waste products in the form of
carbon dioxide go the other way, via
plasma to the lungs (it is the carbon
dioxide level in the blood that
regulates respiration, which is
monitored by chemical receptors in
the brain that are very sensitive to
CO2). The diffusion of oxygen into
the blood depends on partial pressure
(that is, the pressure in proportion to
the amount of an individual gas in
the mix), so as this falls, oxygen
assimilation is impaired (although
the air gets thinner, the ratio of gases
remains the same). Even if you
increase the proportion of oxygen to
100% as you climb, there is an
altitude (around 33,700 feet) where
the pressure is so low that the partial
pressure is actually less than that at
sea level, so just having oxygen is
not enough.
From 0-10,000 ft you can survive on
normal air; above this, an increasing
amount of oxygen relative to the
other ingredients is required, up to
33,700 feet, at which point you
require pure oxygen to survive
(breathing 100% oxygen at that
　
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