# The Effect Of Lift On Aerofoil: Misconceptions Of Flight

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The Effect Of Lift On Aerofoil: Misconceptions Of Flight
Abstract
The problem discussed in this report is how lift is truly generated on an aerofoil and also explaining the misconceptions of lift and why they are not correct. Further topics discussed are the

Lift is a force that directly opposes the weight of an aircraft and holds the object in air. Since lift is a result of the thrust or motion of the aircraft it is therefore a force (vector) because it has a magnitude and a direction. But lift cannot be achieved without thrust. This is the mechanical force generated by the aircraft (engines) to overcome the drag and the weight of the aircraft. If the magnitude of thrust is lesser than the magnitude of weight, no motion is achieved thus no lift is produced.

Various factors affect lift.
Camber line is at equal distance from the upper and lower surface of the wing. Camber is the curvature of the mean camber line. Source: http://www.skybrary.aero/index.php/Aerofoil

Effects of size of an aircraft on lift and drag are roughly the same. Lift and Drag are both aerodynamic forces hence they depend on the pressure variation around the body. Both lift and drag are directly proportional to the area of the body thus doubling the area would double lift and drag. Choosing to increase lift is down solely to the wing area because this the part that generates most of the lift.

POPULAR MISCONCEPTIONS ON THE THEORY OF LIFT
Before we fully explain lift and how it is generated on an aerofoil we must first discredit the common misconceptions or explanations of lift that are still found in some textbooks and journals from around the
Imagine sliding the bottom magnet across the bottom half of the aerofoil. Since they attract each other the top magnet will also follow its path and speed up over the curve edge to be directly over the bottom magnet by the time it reaches the trailing edge! Wind tunnel experiments have shown that air particles over the top actually speeds up over the top but does not rejoin with the air particles flowing underneath the aerofoil.

Another misconception is the ‘Venturi theory’. This relies on Bernoulli’s principle (it states that for an inviscid flow of a nonconducting fluid, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure), although the Bernoulli’s principle is correct it is used incorrectly in this theory. The theory goes to say that the leading edge of an aerofoil is viewed as a nozzle, since it is curved air flow is restricted therefore velocity over the top is increased so pressure decreases on the upper surface. But an aerofoil has flat surfaces, so there is no nozzle formed. It also only takes into account the pressure and velocity on the upper half of the foil and not both parts that is incorrect because the bottom does produce

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