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AIM

10/12/17

8−1−4

Fitness for Flight

10,000 feet during the day, and above 5,000 feet at

night. The CFRs require that at the minimum, flight

crew be provided with and use supplemental oxygen

after 30 minutes of exposure to cabin pressure

altitudes between 12,500 and 14,000 feet and

immediately on exposure to cabin pressure altitudes

above 14,000 feet. Every occupant of the aircraft

must be provided with supplemental oxygen at cabin

pressure altitudes above 15,000 feet.

b. Ear Block.

1. As the aircraft cabin pressure decreases

during ascent, the expanding air in the middle ear

pushes the eustachian tube open, and by escaping

down it to the nasal passages, equalizes in pressure

with the cabin pressure. But during descent, the pilot

must periodically open the eustachian tube to

equalize pressure. This can be accomplished by

swallowing, yawning, tensing muscles in the throat,

or if these do not work, by a combination of closing

the mouth, pinching the nose closed, and attempting

to blow through the nostrils (Valsalva maneuver).

2. Either an upper respiratory infection, such as

a cold or sore throat, or a nasal allergic condition can

produce enough congestion around the eustachian

tube to make equalization difficult. Consequently, the

difference in pressure between the middle ear and

aircraft cabin can build up to a level that will hold the

eustachian tube closed, making equalization difficult

if not impossible. The problem is commonly referred

to as an “ear block.”

3. An ear block produces severe ear pain and

loss of hearing that can last from several hours to

several days. Rupture of the ear drum can occur in

flight or after landing. Fluid can accumulate in the

middle ear and become infected.

4. An ear block is prevented by not flying with

an upper respiratory infection or nasal allergic

condition. Adequate protection is usually not

provided by decongestant sprays or drops to reduce

congestion around the eustachian tubes. Oral

decongestants have side effects that can significantly

impair pilot performance.

5. If an ear block does not clear shortly after

landing, a physician should be consulted.

c. Sinus Block.

1. During ascent and descent, air pressure in the

sinuses equalizes with the aircraft cabin pressure

through small openings that connect the sinuses to the

nasal passages. Either an upper respiratory infection,

such as a cold or sinusitis, or a nasal allergic condition

can produce enough congestion around an opening to

slow equalization, and as the difference in pressure

between the sinus and cabin mounts, eventually plug

the opening. This “sinus block” occurs most

frequently during descent.

2. A sinus block can occur in the frontal sinuses,

located above each eyebrow, or in the maxillary

sinuses, located in each upper cheek. It will usually

produce excruciating pain over the sinus area. A

maxillary sinus block can also make the upper teeth

ache. Bloody mucus may discharge from the nasal

passages.

3. A sinus block is prevented by not flying with

an upper respiratory infection or nasal allergic

condition. Adequate protection is usually not

provided by decongestant sprays or drops to reduce

congestion around the sinus openings. Oral decon-

gestants have side effects that can impair pilot

performance.

4. If a sinus block does not clear shortly after

landing, a physician should be consulted.

d. Decompression Sickness After Scuba

Diving.

1. A pilot or passenger who intends to fly after

scuba diving should allow the body sufficient time to

rid itself of excess nitrogen absorbed during diving.

If not, decompression sickness due to evolved gas can

occur during exposure to low altitude and create a

serious inflight emergency.

2. The recommended waiting time before going

to flight altitudes of up to 8,000 feet is at least

12 hours after diving which has not required

controlled ascent (nondecompression stop diving),

and at least 24 hours after diving which has required

controlled ascent (decompression stop diving). The

waiting time before going to flight altitudes above

8,000 feet should be at least 24 hours after any

SCUBA dive. These recommended altitudes are

actual flight altitudes above mean sea level (AMSL)

and not pressurized cabin altitudes. This takes into

consideration the risk of decompression of the

aircraft during flight.