What is Drag?
The air resistance experienced by aircraft as it moves relative to the air
Which direction does it act in?
Opposite to the direction of thrust (motion through the air)
What force does drag oppose?
Thrust?
What are the 2 groups of drag?
1) Parasite Drag
2) Induced Drag
What is induced Drag?
Unavoidable by product of lift and increases as the angle of attack increases.
The lower the ______, the less______ required to balance it
Drag
Thrust
Is parasite Drag associated with the development of lift?
No
What are the 2 sub groups of parasite drag?
1) Profile drag
2) Interference Drag
What does Form drag result from?
Results from the airflow separating from the surface.
What is the separation point?
The point at which the streamline flow separates from the surface and becomes turbulent.
When is a wing said to be stalled?
A very high angle of attack, the boundary layer cannot follow the upper surface and breaks away from the wing at the critical angle of attack
To delay the separation of the boundary layer from the surface, reduce form drag.
True or False?
True.
What helps to delay the separation if the boundary layer?
Streamlining
What is skin friction?
Results from the friction forces existing between an object and the air through which it moving.
An increase in airspeed increases skin friction drag. True or False?
True.
What 5 factors effect skin drag?
1) Surface of A/C
2) boundary layer airflow near surface is laminar or turbulent
3) Roughness on a surface.
4) increases in airspeed
5) Thickness of Aerofoil
Where does Interference Drag occur?
At the junction of aircraft surface (wings joining fuselage)
How can Interference drag be reduced?
With Filleting/ fairings
What is Induced Drag?
A by-product of the production of lift
What is an example of induced drag?
Vortices at the end of wing tips
What is a spillover?
Where the high and low pressure Air meet to create a vortex
When is the pressure differential/ vortices at their strongest?
Approach phase
High AoA and low speed
Which wing is less affected by induced drag?
Long narrow wings (high aspect ratio wings)
Flaps and undercarriage act to reduce the effect of induced drag. True or False?
True
When are vortexes greatest (induced drag)
When heavy, clean configuration and flying slowly.
What are another means of reducing wing tip vortices?
Wing lets
An aircraft accelerated along the runway with zero angle of attack. What drag exists?
Parasite drag
When is induced drag at its greatest?
During high angles of a attack (climbing)
What are the two types of profile drag?
Form drag
Skin drag
What is a consequence of form drag?
Eddies are formed and streamlined flow is disturbed
