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When a glider ascends, middle ear air pressure may exceed the pressure of the air in the external ear canal, causing the eardrum to bulge outward. This pressure change becomes apparent when you experience alternate sensations of “fullness” and “clearing.” During a descent, the reverse happens. While the pressure of the air in the external ear canal increases, the middle ear cavity, which equalized with the lower pressure at altitude, is at lower pressure than the external ear canal. The result is higher outside pressure, causing the eardrum to bulge inward. 

This condition can be more difficult to relieve due to the fact that air must be introduced into the middle ear through the eustachian tube to equalize the pressure. The inner ear is a partial vacuum and tends to constrict the walls of the eustachian tube. To correct this often painful condition, which causes temporary reduction in hearing sensitivity, pinch your nostrils, close your mouth and lips, and blow slowly and gently in the mouth and nose. This procedure, called the valsalva maneuver, forces air up the eustachian tube into the middle ear. 

## Spatial Disorientation 

For glider pilots, prevention is the best remedy for spatial disorientation. If the glider you are flying is not equipped for instrument flight, and you do not have many hours of training in controlling the glider by reference to instruments, it is best to avoid flight in reduced visibility or at night when the horizon is not visible. Susceptibility to disorienting illusions can be reduced through training, awareness, and learning to rely totally on your flight instruments. [Figure 13-7] 

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## Dehydration 

Dehydration is the term given to a critical loss of water from the body. The first noticeable effect of dehydration is fatigue, which in turn makes top physical and mental performance difficult, if not impossible. Glider pilots often fly for a 

long period of time in hot summer temperatures or at high altitudes. This makes dehydration very likely for two reasons: the gliders clear canopy offers no protection from the sun and, at high altitudes, there are fewer air pollutants to diffuse the sun’s rays. The result is continual exposure to heat that the body attempts to regulate by perspiration. If this fluid is not replaced, fatigue progresses to dizziness, weakness, nausea, tingling of hands and feet, abdominal cramps, and extreme thirst. [Figure 13-8] 

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Water should be taken on every flight to prevent dehydration. The effects of dehydration on a pilot’s performance are subtle, but can be dangerous and are especially a factor in warmer climates. Some glider pilots wear a hat to block the sun from distracting their ability to fly and see the instruments. Pilots should ensure that the brim of the hat is not too large, which can interfere with the ability to scan for other gliders and air traffic. 

## Heatstroke 

Heatstroke is a condition caused by any inability of the body to control its temperature. Onset of this condition may be recognized by the symptoms of dehydration, but also has been known to be recognized only by complete collapse. To prevent these symptoms, it is recommended that you carry an ample supply of water and use it at frequent intervals on any long flight, whether you are thirsty or not. Wearing light colored, porous clothing and a hat provides protection from the sun. It is also helpful to keep the cockpit well ventilated, which aids in dispelling excess heat. 

## Cold Weather 

When flying at higher altitudes, the inside of the glider can get cold. Proper clothing is a must since temperatures of –30° to –60 °C may be encountered at altitude. Proper preparation for the cold is especially difficult since temperatures on the ground 

