Aeronautics Bulletin

When the darkness comes


Dan McDowell

Eyes adapt to lighting situations, daylight, night, or even wearing sunglasses.

The cool, still air of the evening tempts you like a siren to take flight. Then the rising moon acts like a beacon, adding to the temptation to fly. While flying at night is beautiful to some pilots, it is intimidating to many others. Though it is about the same as daylight flying in many ways, night flying comes with some important differences. One of these differences is night vision and its unique challenges.

It is easier to understand night vision and its associated challenges if you first understand basically how the eye works. There are millions of light sensitive nerves called rods and cones in the back of the eye (the retina). These rods and cones are in large part responsible for our ability to see. The rods form a ring around the cones in the center of the eye and can detect moving objects, shades of gray, and give us peripheral vision. Detail, color, and distant objects are detected by the cones.

In normal daylight, the best way to see an object is to look directly at it. While at night, the best way to see an object is to look to the side of it. This will allow the rods to better detect an object, it's movement, and the subtle shades of reflected light. So to see better at night, it is recommended to slowly scan an area to maximize your night vision.

When preparing for night flying, it is strongly suggested that you begin by adapting your eyes to the darkness. As an example, if you walk from the brightly lit terminal lobby to the darkened pilots' lounge, it takes your eyes (the cones) from 5 10 minutes to adjust to the very dimly lit room. Once adjusted, the cones become 100 times more sensitive to light. It takes nearly 30 minutes for the rods to fully adjust to the darkness. When they do adjust, they become about 100,000 times more sensitive to light!

At many of today's well-lit airports, it is almost impossible to maintain complete darkness adaptation. You should bear in mind that exposure to bright lights will require that you redo the adaptation process.

Also, before you begin the night adaptation process it is important to conduct a thorough preflight inspection including internal and external aircraft lights. Check the spare fuses and bulbs to be sure none are missing.

Here are some suggested ways to improve your night flying vision:

1. Do not wear sunglasses after sunset.

2. Do all possible to adapt your eyes to the darkness prior to flight.

3. Remember that it takes approximately 30 minutes to adjust your eyes after exposure to bright light.

4. Concentrate on seeing objects.

5. Move your eyes more slowly than in daylight.

6. Force your eyes to view off center.

7. Adjust cockpit lighting to the optimum night vision level for viewing inside and outside the aircraft.

8. If you still use paper charts, avoid using yellow or pink highlighters on them. These colors do not show up at night with the red cockpit lighting on. If you use the white light, you may see your highlighted lines but you will lose your night vision. Use blue instead. In red cockpit lighting it shows up as a purple toned blue.

9. If you use an electronic pad, be sure to adjust the brightness so that it does not destroy your night vision.

Dan McDowell

Eyes take in the all important information for safe flying.

Always carry a quality flashlight with a red night vision filter, a spare set of batteries and a spare bulb, or a spare high quality flashlight with fresh batteries. Make sure these items are within easy and immediate reach. Should the need suddenly arise, there may not be time to search for them in a dark cockpit, and seeing in the darkness may not be possible for a time.

Have your eyes checked regularly and practice adjusting your night vision so you are ready when the darkness comes.


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