In addition to the principles previously discussed, the following  actions aid in increasing night vision effectiveness: • Adapt the eyes to darkness prior to flight, and keep  them adapted. About 30 minutes is needed to adjust  the eyes to maximum efficiency after exposure to a  bright light. • Use oxygen during night flying, if available. Keep in  mind that a significant deterioration in night vision  can occur at altitudes as low as 5,000 feet. • Close one eye when exposed to bright light to help  avoid the blinding effect. • Avoid wearing sunglasses after sunset. • Move the eyes more slowly than in daylight. • Blink the eyes if vision becomes blurred. • Concentrate on seeing objects. • Force the eyes to view off center. • Maintain good physical condition. • Avoid smoking, drinking, and using drugs that may  be harmful.  Unique WSC Flight Characteristics If the WSC aircraft is trimmed properly and the pilot is  proficient in the basic flight maneuvers of climbs, cruise,  and descent procedures, the WSC aircraft speed is easily  determined with control bar pressure and position for normal  flight conditions. A pilot can also determine basic climbs and  descents through the feel of the aircraft with the airspeed and  throttle positions. Therefore, basic pitch control can be done  by a proficient pilot with his or her eyes closed. As discussed in Chapter 2, Aerodynamics, WSC aircraft  are generally not designed to be roll stable, and any engine  turning effect or movement of the air can put the WSC aircraft  into a roll, which it maintains unless corrected by the pilot.  In other words, releasing the control bar in a WSC aircraft  will not level a bank back to straight flight. The pilot must  continually provide input to fly a constant heading even if this  control is small corrections. In other words, the pilot cannot  level the wings or fly a straight heading for very long with  his or her eyes closed. To maintain a constant heading or ground track, one of  three instruments can be used: magnetic compass, global  positioning system (GPS), and aircraft heading indicator.  Without a visual reference, these can be used to fl y straight.  An attitude indicator can be used on WSC aircraft providing  additional instrument reference. These instruments and others  are discussed later in this chapter.  Night Illusions In addition to night vision limitations, pilots should be aware  that night illusions could cause confusion and concerns  during night flying. The following discussion covers some  of the common situations that cause illusions associated with  night fl ying. A false horizon can occur when the natural horizon is obscured  or not readily apparent. It can be generated by confusing  bright stars and city lights. It can also occur while fl ying  toward the shore of an ocean or a large lake. Because of the  relative darkness of the water, the lights along the shoreline  can be mistaken for stars in the sky.  [Figure 12-7] Figure 12-7.  At night, the horizon may be hard to discern due to dark  terrain and misleading light patterns on the ground. On a clear night, distant stationary lights can be mistaken for  stars or other aircraft. Even the northern lights can confuse a  pilot and indicate a false horizon. Certain geometrical patterns  of ground lights, such as a freeway, runway, approach, or  even lights on a moving train can cause confusion. Dark  nights tend to eliminate reference to a visual horizon. As a  result, pilots need to rely less on outside references at night  and more on flight and navigation instruments. Visual autokinesis can occur when a pilot stares at a single  light source for several seconds on a dark night. The result  is that the light appears to be moving. The autokinesis effect  does not occur if the pilot expands the visual field. It is a  good procedure to vary visual focus and not become fi xed  on one source of light. 12-7