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AIM 

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, altitude decompression sickness due to evolved nitrogen 

gas can occur during exposure to reduced barometric pressure (i.e., low cabin pressure) associated with increased 

altitude and may lead to a serious inflight emergency. 

2. 

The recommended wait time before going to flight altitudes up to 8,000 feet is at least 12 hours after 

diving that did not require a controlled ascent (i.e., non

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decompression stop diving), and at least 24 hours after 

diving that required a controlled ascent (i.e., decompression stop diving). The recommended wait time before 

going to flight altitudes above 8,000 feet is 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 aircraft decompression during flight. 

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3.  Hyperventilation in Flight 

a. 

Hyperventilation, or an abnormal increase in the volume of air breathed in and out of the lungs, can occur 

subconsciously when a stressful situation is encountered in flight. As hyperventilation “blows off” excessive 

carbon dioxide from the body, a pilot can experience symptoms of lightheadedness, suffocation, drowsiness, 

tingling in the extremities, and coolness and react to them with even greater hyperventilation. Incapacitation can 

eventually result from incoordination, disorientation, and painful muscle spasms. Finally, unconsciousness can 

occur. 

b. 

The symptoms of hyperventilation subside within a few minutes after the rate and depth of breathing are 

consciously brought back under control. The buildup of carbon dioxide in the body can be hastened by controlled 

breathing in and out of a paper bag held over the nose and mouth. 

c. 

Early symptoms of hyperventilation and hypoxia are similar. Moreover, hyperventilation and hypoxia can 

occur at the same time. Therefore, if a pilot is using an oxygen system when symptoms are experienced, the 

oxygen regulator should immediately be set to deliver 100 percent oxygen, and then the system checked to assure 

that it has been functioning effectively before giving attention to rate and depth of breathing. 

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4.  Carbon Monoxide Poisoning in Flight 

a. 

Carbon monoxide is a colorless, odorless, and tasteless gas contained in exhaust fumes. When breathed 

even in minute quantities over a period of time, it can significantly reduce the ability of the blood to carry oxygen. 

Consequently, effects of hypoxia occur. 

b. 

Most heaters in light aircraft work by air flowing over the manifold. Use of these heaters while exhaust 

fumes are escaping through manifold cracks and seals is responsible every year for several nonfatal and fatal 

aircraft accidents from carbon monoxide poisoning. 

c. 

A pilot who detects the odor of exhaust or experiences symptoms of headache, drowsiness, or dizziness 

while using the heater should suspect carbon monoxide poisoning, and immediately shut off the heater and open 

air vents. If symptoms are severe or continue after landing, medical treatment should be sought. 

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5.  Illusions in Flight 

a.  Introduction. 

Many different illusions can be experienced in flight. Some can lead to spatial 

disorientation. Others can lead to landing errors. Illusions rank among the most common factors cited as 

contributing to fatal aircraft accidents. 

Fitness for Flight 

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