Thursday, November 30, 2006

My friend Joann sent me this picture today. Amazing, isn't it? It reminded me of a friend of mine taking private pilot lessons that was told by her flight instructor that it was too early in her training to fly at night. I thought this was so tragic when I heard it--flying at night is so amazing! But it made me start thinking(since this phase of my training is WAY far behind me), about all the differences between flying at night and during the day.

First, from personal experience, I can tell you it's amazingly beautiful. I've tried to take pictures of the New York City skyline at night, and there is NO way to hold a camera still enough to get anything but streaks of light. A person does lose their depth perception in the dark, though, making landings a little difficult. Knowing this and compensating for it (by checking your altitude over the ground, using other visual cues) can overcome illusions such as:

A Black-Hole Approach Illusion.

A Black-Hole Approach Illusion can happen during a final approach at night (no stars or moonlight) over water or unlighted terrain to a lighted runway beyond which the horizon is not visible. When peripheral visual cues are not available to help you orient yourself relative to the earth, you may have the illusion of being upright and may perceive the runway to be tilted left and upsloping. However, with the horizon visible, you can easily orient yourself correctly using your central vision.

A particularly hazardous black-hole illusion involves approaching a runway under conditions with no lights before the runway and with city lights or rising terrain beyond the runway. These conditions may produce the visual illusion of a high altitude final approach. If you believe this illusion, you may respnd by lowering your approach slope.

There are a number of visual illusions for day or night that pilots study in their training. A good summary of all of them is in an FAA brochure that you can find here:

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