Sunday, December 18, 2011

Radian Flying

I didn't get a chance to fly with the GoPro camera yet, but I did do some flying around while my Dad filmed from the ground. Where I am flying is about 5000 feet above sea level, so you would think that they plane would be 'lazy' in the thin air. But it flew much faster, glided longer and climbed better. I did some research and found that there are some very interesting physics causing these counterintuitive  flying characteristics. After searching around some, I found an explanation. First off, thrust from the propeller. At sea level, with the 'thick' air, the motor turning the propeller bogs down quite a bit under the load. As the air gets thinner, at altitude, the propeller gives less thrust at the same RPMs as sea level, but that means it also has less load so it turns faster, increasing the thrust. So basically the motor speeds up under the lesser load and that is enough to compensate. And as far as the gliding, what I read said that as the air gets thinner, the air resistance of the plane reduces with altitude faster than the lift. That means as you get higher in elevation, the drag decreases compared to the lift. So the higher you are the less drag there is at cruising speed. Meaning you can fly faster and glide farther. I got the information from here. In this video, it is the first time I have used the flaps I recently made for the plane. It is very cold out (about 30 degrees Fahrenheit) in the video, but that doesn't seem to affect the plane. Here is the video:
Watch how it just lifts off the ground, and when I am coming in to land I have to push it down with the elevator, otherwise it will just keep going.

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