3 Rs




Monday, February 7, 2011

Aircraft Lift - How Planes Really Fly

In Canada and the United States of America, books on how planes fly use Bernoulli's Theorm to explain lift. There is nothing wrong with Bernoulli's Theorm. It has been incorrectly applied to lift in most published books and flight manuals for the past 72 years.

The Province of Ontario, Canada has correctly removed any mention of Bernoulli from its Revised Science Curriculum on "Flight" for Grade 6, published in 2007. The revised curriculum was to be implemented in 2008 by all schools in the Province of Ontario.

Airflow over a wing

Air passing over a wing is broken down into streamlines. Streamline 1 sticks to the upper surface of the wing due to viscosity. Streamline 2 wants to go in a straight line (Newton’s 1st Law). As the streamlines separate, it creates a vacuum between the streamlines. This vacuum causes the pressure to drop. The lower pressure increases the speed of the streamline. Since streamlines communicate with each other, streamline 2 follows the curve of the upper wing and goes off the trailing edge. The same applies to streamlines 3, 4, and all subsequent streamlines. From the pilot’s perspective where the wing is still and the air is moving (and if he could see the streamlines) the streamlines go off the trailing edge of the wing = to the angle of attack of the wing. From a person’s perspective standing on the ground where the wing is moving and the air is originally still (assuming the person could see the air) the air is coming straight down. The acceleration of the air down by the wing is called “downwash.” Air goes straight down to produce a force straight up(Presto! Newton’s 3rd Law). This is really how planes fly.

The shape of the wing only contributes to the efficiency of lift, but even a flat board  will also create significant lift.

No comments:

Post a Comment