Balance and Hearing Ear, System, Nervous The 4

•Blocked eustachian tubes.

•Sudden pressure changes in the inner ear (sneezing or strong blowing of the nose).

•Accelerations or high g-loadings.

Alcohol intoxication provokes vertigo.

Coriolis Effect

If a steady turn is being maintained then a sudden movement (greater than about 3° a second) of the head will be detected as a change in the turn rate. This phenomenon is referred to as a cross-coupled stimulation of the semicircular canals (coriolis effect).

It cannot be overemphasized that where there is a conflict between the two senses, the visual reference will provide the more accurate picture of orientation. Pilots are urged to always remember that the most important sense for spatial orientation is sight.

Alcohol and Flying

Alcohol has a lower specific gravity than water. Alcohol in the fluid of the inner ear will change the specific gravity and cause erroneous results for certain movements, leading to disorientation. Alcohol in the fleshy stalk of the otoliths may persist for days after all traces of alcohol have vanished from the blood. It is not unusual for even small movements of the head to cause disorientation or motion sickness up to three days after alcohol was last consumed.

Motion Sickness

Motion sickness is a misnomer since it is a normal and direct manifestation of sensory functions. It is probable that no one with a normal vestibular apparatus is completely immune and motion sickness has been referred to since the times of Hippocrates. It arises when man is exposed to real or apparent motion of an unfamiliar kind. It occurs not only in normal flying but also in space or at sea. Some individuals experience it in a car or on a train. Motion sickness is caused by a mismatch between the visual and vestibular signals. The symptoms of motion sickness are:

•Nausea.

•Hyperventilation.

•Vomiting.

•Pallor.

•Cold sweating.

•Headache.

•Depression.

It can be severely incapacitating but is a normal response to perceived stimuli.

Anyone with a normal sense of balance will suffer motion sickness if stimulated enough. Its symptoms are observed in up to 8% of passengers on board modern aircraft. Motion sickness can be generated without any real motion even, for example, in a simulator when an expected movement does not occur. Motion sickness can cause problems with flying training programmes and, to avoid the problem, all progress should be gradual. For example gradual progress from gentle to steep turns and avoidance of aerobatics during early training. Any prolonged break from training may lead to a recurrence of the problem.

Many pilots experience motion sickness when they fly but most can adjust or be conditioned to avoid symptoms. For a pilot suffering from chronic motion sickness it is most important that his/her organization’s aviation specialist is consulted.

The Nervous System, Ear, Hearing and Balance 4

Balance and Hearing Ear, System, Nervous The 4

Coping with Motion Sickness

If motion sickness is experienced there are a number of strategies to give relief:

•Keep the head still if possible, as movement aggravates the vestibular system.

•Visual mismatching can be reduced by closing the eyes but this is obviously not acceptable for aircrew. Being relieved of lookout duty, with its continuous head movements will help, as will concentrating on flying the aircraft.

•Go for steady progress in aircraft manoeuvres. Opening the air vents will help in the majority of cases.

•Medication may help but always consult an aviation doctor before taking any drugs before flying. Hyoscine is the normal drug prescribed for air sickness.

Questions

1.The outer, middle and inner ear are filled with:

2.What is the purpose of the Eustachian tube?

a.To pass sound waves across the middle ear to the auditory nerve

b.To allow ambient pressure to equalize on both sides of the ear drum

c.To allow ambient pressure to equalize on the middle ear side of the ear drum

d.To allow ambient pressure to equalize on both sides of the vestibular apparatus

3.What causes conductive deafness?

a.Damage to the outer ear

b.Damage to the pinna

c.Damage to the ossicles or the eardrum

d.Damage to the middle ear

4.What is noise induced hearing loss (NIHL)?

a.Loss of hearing due to damage to the ossicles

b.Loss of hearing due to damage to the vestibular apparatus

c.Loss of hearing due to damage to the middle ear

d.Loss of hearing due to damage to the cochlea

5.On what does NIHL depend?

a.Both the intensity and duration of the noise above 100 dB

b.The duration of the noise above 100 dB

c.The duration of the noise above 110 dB

d.Both the intensity and duration of the noise above 90 dB

6.What is the most important sense for spatial orientation?

a.Hearing and balance

b.Sight

c.“Seat of the pants”

d.All senses play their part in situation awareness

7.If an aircraft accelerates, what do the otoliths indicate to the brain?

a.That the aircraft nose is pitching down; this feeling will be reinforced by an air driven artificial horizon

b.That the aircraft is turning; this feeling will be reinforced by an air driven artificial horizon

c.That the aircraft is climbing and turning; this feeling will be reinforced by an air driven artificial horizon

d.That the aircraft is pitching up; this feeling will be reinforced by an air driven artificial horizon

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