Certified Flight Instructor - Flight Instructor Airplane Practice Exam

What physical change is likely for occupants of an unpressurized aircraft flying above 15,000 feet?

1. Gases trapped in the body contract and prevent nitrogen from escaping.

2. The pressure in the middle ear becomes equal to atmospheric pressure.

3. A blue coloration of the lips and fingernails develops along with tunnel vision.

4. Increased body temperature due to decreased pressure.

The correct answer is: A blue coloration of the lips and fingernails develops along with tunnel vision.

At altitudes above 15,000 feet in an unpressurized aircraft, occupants are likely to experience hypoxia due to reduced atmospheric pressure and availability of oxygen. As altitude increases, the partial pressure of oxygen decreases, and the body's ability to absorb sufficient oxygen can diminish. This can lead to symptoms including a blue coloration of the lips and fingernails, known as cyanosis, which occurs because of insufficient oxygen in the blood. Additionally, tunnel vision can result from the effects of low oxygen levels on the brain. Thus, the correct answer indicates significant physiological responses to inadequate oxygen levels at high altitudes. The other options presented focus on different aspects of human physiology that do not accurately describe the effects experienced at high altitudes. For instance, gases in the body do not contract in a way that would prevent nitrogen from escaping, and the pressure in the middle ear does not always equalize with atmospheric pressure during rapid climbs or descents. Also, decreased pressure does not directly increase body temperature; rather, thermoregulation and other factors can come into play that do not lead to a direct increase in body temperature due to altitude.