The aerofoil is a cross-section shape of a wing taken at right angles to the wing span. Also known as the wing section or rib section.

An aerofoil is shaped so that air flows faster over the top than under the bottom. There is, therefore, a greater pressure below the aerofoil than above it. This difference in pressure produces the lift.

wing-section lift

The lift generated by a wing is based on the principle that the pressure in a fluid decreases as its velocity increases (Bernoulli′s Principle):

Aileron – Movable control surfaces, usually mounted in the trailing edge of a wing adjacent to the wingtips, to control an aircraft′s rolling movements.

Angle of Attack

angle of attack

The angle at which a wing strikes the air stream.

zero angle of attack
The ability to create lift is dependent on the airflow remaining smooth around the airfoil. At zero degrees angle of attack there is just a small turbulent wake.
small angle of attach
As the angle of attack is increased the lift increase and the point at which the airflow separates from the upper surface of the wing moves slightly forward.
high angle of attach
Just before the wing stalls maximum lift is generated and the separation has moved further forward.
wing about to stall
At very high angles of attack the separated flow region expands and the lift is reduced and drag increases. There will be a large turbulent wake.

Camber – The curvature, convex or concave, of an airfoil surface.

Chord – The distance measured from the leading-to trailing-edge of an airfoil.


Hinged surfaces attached to the trailing edge of a wing, either to increase maneuverability (as on a control line aerobatic model) or to increase lift at the expense of drag (as on most full size aircraft and some radio control aeroplanes). The simplest is the plain flap.

graphic of the plain flap
plain flap

The effectiveness of the flap at increasing lift may be improved by going to a more complicated design, although the mechanism to control the flap will become more complicated. An example is the venetian blind flap.

graphic of the venetian blind flap
venetian blind flap

An alternative to having separate flaps is to mix the flaps with the ailerons producing flaperons. However, the effectiveness of the ailerons will be lost to some extent. Also, the amount of flap that is introduced should be checked to ensure that it can be accommodated along with the aileron control.

Leading Edge – The edge of an airfoil which first meets the airstream in normal flight.

Slats – Used on the leading edge of a wing to improve lift. They help the formation of a smooth boundary layer over the leading edge allowing the wing to operate at a higher angle of attack before separation occurs.

Spars – Spanwise load-carrying members of a wing or tail.

Stability – The tendency of an aeroplane to return to level flight, after having been disturbed by an upsetting force.

Stall – The complete loss of lift resulting from too steep an angle of attack.

Stalling Angle – The particular angle at which a wing abruptly loses lift; usually expressed in degrees.

Trailing Edge – The rear edge of an aerofoil.

Wing Loading

The aircraft mass divided by the wing area.

This is normally the gross take-off weight of an aircraft divided by its wing area.

Buzz Z33.9
Fun 1606.3
Bleriot XI9
ASK 2133
Nieuport 1738
Ikarus C4238
Cessna 15251
Vans RV-467
Eurofighter Typhoon311
Boeing Dreamliner702
Wing Loading in kgm-2

Wing Warping

Bleriot Monoplane

The earliest form of roll control was produced by warping the whole wing.

Raising the trailing edge of the right hand wing and lowering the trailing edge of the left hand wing will result in the aircraft rolling to the right.

The problem is if the wing is too stiff it is difficult to warp, if the wing is not very stiff it is easy to warp but is prone to flutter at speed.

Zero-Lift Chord – A chord taken through the trailing edge of an airfoil in the direction of the relative wind when the airfoil is at a zero-lift angle of attack.

Read more about Fluid Dynamics on our main pages.

About Nigel 336 Articles
I've been making models since I was around 7 years old and using a lathe from the age of 11, a self taught engineer with a passion for making model engines.

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