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The Principals of Flight. Bronze Theory. Airflow. Bernoulli’s Theorem. Daniel Bernoullli (1700-1782) was a Swiss mathematician. V x P = Constant An increase in the speed of a fluid results in a simultaneous reduction in pressure. Bernoulli’s Theorem. Sir Isaac Newton.
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The Principals of Flight Bronze Theory
Bernoulli’s Theorem • Daniel Bernoullli (1700-1782) was a Swiss mathematician. • V x P = Constant • An increase in the speed of a fluid results in a simultaneous reduction in pressure.
Sir Isaac Newton • Isaac Newton (1643-1727) was an English physicist, mathematician & astronomer. • Newton’s laws of motion. • For every action there is an equal and opposite reaction.
Lift increases with Angle of Attack until the critical angle is reached at which point the airflow can no longer flow smoothly over the wing’s upper surface. The wing has now stalled. When the wing stalls the centre of pressure moves rapidly towards the trailing edge, this creates a nose down pitching movement.The stalled wing also creates a lot of drag.
Stalling / Spinning • We have seen from an earlier slide that when the wing gets to a certain A of A the lift it generates is reduced and that it will stall. • Of course it is entirely possible that one wing will stall before the other, when this occurs if no corrective action is taken a spin is likely to develop. • This process is known as Autorotation, and results from the combination of loss of lift and increased drag on the stalled wing. • The next slide will help to clarify this.
The Boundary layer • Modern sailplanes use laminar flow airfoils, for these to work the wing surface must be smooth and retain the cross section that the designer intended. • Laminar flow sections have a thin boundary layer of air directly in contact with the wings surface which moves in a smooth orderly (i.e. laminar) fashion from the leading edge towards the trailing edge.
The Boundary layer • At some point during this chordwise movement of the air, the flow will become turbulent,thepoint at which this occurs is called the transition point. • The turbulent air is a major source of drag.
The Boundary layer • It has been found that it is more efficient to trip the boundary layer to turbulent flow before it occurs naturally. • This process of tripping the boundary layer is usually achieved by applying a span wise strip of zig - zag plastic tape.
Compass Errors • In the Northern hemisphere the following will happen. • When flying East or West if you accelerate the compass will swing to the North, if you decelerate it will swing to the South. • To help you remember this ANDS = Accelerate North, Decelerate South.
Compass Errors • In the UK the compass will lead by 25 – 30 degrees when turning onto a Northerly heading, it will lag by a similar amount when turning onto a Southerly heading. • To help you remember this SLAG = South Lag.