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.

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.

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.

8-1-4

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 decongestants 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.

Fitness for Flight