If you fly an un-pressurised aircraft, you are almost sure, eventually to encounter the problem of ear discomfort during ascent or descent. To understand why this happens and how to counteract it, a simple grasp of the structure of your ear is helpful.

The external ear canal (the small tube leading to your eardrum) is always at the same pressure as the atmosphere surrounding the body. The middle ear, where pressure problems arise, is a small air-filled cavity situated within the bone of the skull and it is separated from the external ear canal by the eardrum - a thin membrane. The other side of the middle ear is connected to the nasal cavity by the Eustachian tube.

As your aircraft gains altitude, the atmospheric pressure decreases and so does the pressure in the external ear canal. The middle ear, being an enclosed cavity, stays at ground-level pressure. When the pressure in the middle ear exceeds that of the external ear canal, your eardrum starts to bulge outward somewhat. The middle ear is sensitive to this change and requires only a slight excess of pressure to open the Eustachian tube so that gas may pass by this route through the nose or mouth. In this way, pressure is equalized on both sides of the eardrum. You may be aware of this pressure change by alternating sensations of ear fullness and "clearing."

During descent, conditions within the ear are reversed. As the surrounding air pressure increases, the middle ear - which has accommodated itself to the reduced pressure at altitude by the process just described - is at a lower pressure than the external ear canal. consequently, the outside air forces the eardrum to bulge inward. This condition is much more difficult to relieve, since air must be introduced back up the Eustachian tube to equalize the pressure. The partial vacuum in the middle ear also tends to collapse rather than inflate the walls of the Eustachian tube. You can best remedy this by closing your mouth, pinching your nostrils shut, and blowing slowly and gently to build up pressure in your mouth and nose. At some point in this procedure, you will be able to feel air entering the middle ear, and you will notice an immediate improvement in your ability to hear. This will be followed by a relief in the sense of fullness and discomfort.

Should you find that you cannot clear your ears in flight, as just described, consult a physician immediately after landing. It may save you weeks of trouble. The AME can quickly and painlessly solve the problem.