Principles of Flight EUGC Training Talk Wednesday 28 th September 2005

It's all about wings ● How they work ● What else we need to use them – Stabilisers, control surfaces... and a cockpit ● How we control them – Primary and secondary effects of controls. ● When they won't work – Stalls, spins and stresses ● How to make the best of them – Speed, sink and polar curves

What is a wing? ● Ask a five year old... – What does it look like? ● “it's big and flat” – large surface area – What does it do? ● “it keeps the plane up” – must produce some anti-gravity force – When does it work? ● “when it goes forward” – requires horizontal speed

A first guess ● A wing is big and flat, and converts horizontal speed to an anti-gravity force. Aha! ● “No, that doesn't look right!” – Why? Lift Drag Force

A better wing ● It works better if it's a bit more streamlined – Smoother airflow; generates less drag. ● The shape can also give us some extra lift. – Called the Bernoulli Effect.

Varying the angle ● Lift and drag increase as the angle between the wing and the airflow increases. – This is called the angle of attack. ● At a critical angle of around 17°, the airflow stops being smooth. The drag increases and the lift collapses. The wing has stalled.

What else do we need? ● Can we go flying with just a wing? – Yes, but it's a bit of an awkward design... ● A wing on its own is not particularly stable.

How can we stabilise a wing? ● Use a small wing, and some leverage. – Feedback mechanism opposes tilting. ● Could be either in front or behind! ● Also gives us pitch control with an elevator.

How can we stabilise a wing? ● Use two wings, tilted upwards. – This is called dihedral. ● Another feedback mechanism. ● Add ailerons for roll control.

How can we stabilise a wing? ● We can still swing from side to side. – Add a fin – just like a boat's keel. – Feedback again! ● Add a rudder to give yaw control.

The finished result ● We have invented the aeroplane! ● Now, how do we fly it?

Using the controls ● We can use the elevator to control pitch. ● This also sets our speed. Why? `

Using the controls ● We can use the rudder to control yaw. ● At low speeds this can also induce roll. Why?

Using the controls ● We can use the ailerons to control roll. ● This causes adverse (opposite) yaw. Why?

Co-ordinated turns ● Turning efficiently requires all three controls. ● Where should the string be?

When it stops working ● We can pitch the nose up temporarily. – We can even go all the way around (a loop). ● If the nose stays high, we lose speed. ● At low speeds our wings have a greater angle of attack. Too slow and the wings will stall. – Put the nose down to regain safe flying speed. ● What happens if we're yawing when we stall? – Spinning! – How do we recover from this?

Discussion (and beer)