2. The Aerofoil And Lift Flashcards
What is an Aerofoil?
Any part of an aircraft designed to produce lift.
Wings
Tail surfaces
Propellers are all examples.
Some designs use the fuselage area too.
What are the various parts of a Aerofoil?
A device which gets a useful reaction from air
moving over its surface.
What is the angle of Incidence?
The Angle of Incidence is the angle between the chord line (the angle wing is attached to the
fuselage), relative to the aircraft’s longitudinal axis.
What is the Angle of Attack? (AoA)
The is the angle formed by the chord line and the relative airflow.
(The angle of attack isn’t necessarily the same as angle of incidence.)
Applying Bernoulli’s Principle
The aerofoil is designed to increase the velocity of the airflow over its top surface.
The air has further to travel over the curved upper surface so accelerates.
Bernoulli’s principle tells us that this acceleration causes a reduction in pressure.
What causes lift?
The reduction of pressure on the top surface produces LIFT.
What is the Boundary Layer and (laminar flow)?
The air directly in contact with the surface of the aerofoil is described as the Boundary Layer.
If the boundary layer remains in contact with the surface, the flow is said to be Laminar.
An aerofoil designed for minimum drag and a smooth flow of the boundary layer is called a laminar aerofoil.
What is turbulent flow?
When does stalling occur?
Stalling occurs when the critical angle of attack is exceeded.
For most aerofoils, this is around 15°.
The angle of attack can be simply described as
the difference between where a wing is pointing and where it is going.
Can an AC stall at any speed?
Yes
How will a pilot recognise a stall?
The aircraft handling will change, often the controls will become ‘heavy’ and the airframe will ‘buffet’.
What can alert a pilot to the AC stalling?
Mechanical stall warner (small metal Vein and buzzer)
Large aircraft have a stick shaker
