直升機(jī)教員手冊 Helicopter Instructor’s Handbook
時間：2014-11-10 08:35來源：FAA 作者：直升機(jī)翻譯 點(diǎn)擊：次
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To view this page ensure that Adobe Flash Player version 9.0.124 or greater is installed. Eye Anatomy and Physiology The eye is similar to a camera. The cornea, lens, and iris gather and control the amount of light allowed to enter the eye. The image is then focused on the retina, which has two types of cells: cones and rods. [Figure 14-1] Review the anatomy of the eye and discuss the night blind spot. [Figure 14-2] This discussion should focus on vision while in flight to include visual acuity and the eye’s rods and cones. The more a student knows about the eyes and how they function, the easier it is to use vision effectively and compensate for potential problems. Visual Problems There are several visual problems, or conditions, that affect night vision. Discuss with the student the visual deficiencies, such as myopia, night myopia, hyperopia, astigmatism, and presbyopia. Refer the student to the Helicopter Flying Handbook for in-depth definitions of each visual problem and how each can affect night flying. Instructors should be aware of any specific visual problems that the student may have that could affect his or her ability to fly at night. For example, if the student wears glasses, are the glasses reflecting glare from an unnecessary light? Do the glasses have a coating that interferes with night vision? Does the student wear sunglasses during the day to protect night vision? If the student is older, has he or she been screened for cataracts, which could cause night vision problems? The instructor must teach the student about all possible visual problems but also be aware of any that the student may have. Ground Instruction In a classroom environment, review all terms associated with night operations. Explain to the student how to protect night vision, how to recognize self-imposed stress, the negative effects on night vision from smoking, and the various scanning techniques for night flight. It is also important that visual illusions are explained in detail with information regarding how to detect and react to the illusions. Aircraft instruments are easier to read under higher levels of interior illumination. However, this need must be balanced with the ability to see outside and the hazard of interior lights reflecting off the interior surfaces. Minimize interior lighting, whenever possible, without hindering reading of essential instruments. Night Vision Protection Explain to the student that protecting night vision should always be a priority. Discuss some of the steps to take to protect night vision such as the use of sunglasses and oxygen. Repeated exposure to bright sunlight has an increasingly adverse effect on dark adaptation. Point out that this effect is intensified by reflective surfaces, such as sand and snow. Sunglasses aid in filtering the bright sunlight and increase the rate of dark adaptation at night while improving night visual sensitivity. [Figure 14-3] Explain to a student that unaided night vision depends on optimum function and sensitivity of the rods of the retina. Lack of oxygen to the rods significantly reduces their sensitivity and increases the time required for dark adaptation, as well as decreases the ability to see at night. Since most helicopters do not carry oxygen, more practical advice to give a student who smokes is either to quit or at least reduce the amount that they smoke and advise that physical conditioning helps not only the heart, but also assists the body’s ability to increase oxygen intake. If oxygen is available, pilots should use it when flying above a pressure altitude of 4,000 feet. Additional precautions to discuss with the student pertain to the airport or heliport lighting. Any light sources that may impair the student’s dark adaptation should be eliminated. Tell the student to try to select departure routes that avoid highways and residential areas where artificial light can impair night vision. If bright lights are encountered from a specific direction, turn the aircraft away from the light source when able. If this is not possible, instruct the student to preserve dark adaptation by shutting one eye and using the other to observe. Once the light source is no longer visible, the eye that was closed can provide the required night vision. Self-Imposed Stress Night flight is more fatiguing and stressful than day flight because the brain has to work harder in order to make sense of the limited visual cues or the lack of visual acuity. The pilot must scan more in order to gain sufficient visual cues to maintain the desired flight path. Many helicopters are not well equipped for night flight. Most charts and maps are harder to read and interpret in low levels of light. Inform the student of several self-imposed stressors that limit night vision, such as drugs, illness, fatigue, alcohol, and tobacco. For example, if an individual smokes 3 cigarettes in rapid succession or 20 to 40 cigarettes within a 24-hour period, the physiological effect at ground level is the same as flying at 5,000 feet. More importantly, the smoker has lost about 20 percent of night vision capability at sea level. Review the Pilot’s Handbook of Aeronautical Knowledge with the student to ensure a better understanding of these types of stressors and place emphasis on the fact that the student can control this type of stress. Scanning Techniques It is important to teach the student various night vision techniques that enable him or her to overcome many of the physiological limitations of their eyes. These techniques require considerable practice and concerted effort on the part of the student and the instructor as they are important in identifying objects at night. Instruct the student that to scan effectively, looking from right to left or left to right. Tell the student to begin scanning at the greatest distance an object can be perceived (top) and move inward toward the position of the aircraft (bottom). [Figure 14-4] For each stop, an area approximately 30° wide should be scanned. The duration of each stop is based on the degree of detail that is required, but no stop should last longer than two to three seconds. When moving from one viewing point to the next, the student should overlap the previous field of view by 10°. |
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