Aerodynamik KAP 8 + 9 High lift devices + contamination Flashcards
What effect does increased camber have on CL and CLMAX ?
Increased CL for a given AOA
& increased CLMAX
When extending Plain flap - what happens to the critical AOA & CLMAX
Critical AOA ( stalling angle ) is lower
but with an increased CLMAX
Why does a high speed aerofoil need flaps ?
So it can fly slow enough to land + It needs the drag
What happens to the CP when selecting trailing edge flaps ?
(Effect on nose pitch moment ?)
The CP moves rearwards
Results in a nose pitch down moment
Why does flaps increase pilot visibility on landing ?
Because to maintain airspeed and not climb when selecting flaps - nose must be lowered ( AOA lowered )
What does slats do ?
Reenergize the boundary layer with kinetic energy fromt the high pressure region below the wing
= Prolong lift curve = higher CLMAX at higher AOA
What does reenergizing the boundary layer do ?
Delays boundary layer separation to a much higher AOA
(When the adverse pressure gradient again overwhelms the kinetic airflow)
What is the disadvantage of the slot ?
At low speeds the nose will have a higher attitude = visibility restricted
When flaps are lowered, stalling speed:
Decreases
What happens to the spanwise flow when flaps are lowered ?
Increases towards the root
“Lift concentrated inboard”
What happens to maximum L/D ratio and stall speed when flaps are fully extended ?
Both decreases
Why do we need high lift devices ?
- Slower flying speeds T/O + Landing
- Greater weights T/O + Landing
- Reduced AOA at min flying speed on approach
- Increased drag on approach
When flaps are extended - what should be done to maintain the same lift ?
Reduce AOA
What does vortex generators do ?
Create a vortex and reenergizes the boundary layer = delay separation = delayed stall
Higher AOA for CLMAX
What does flaps before T/O do ?
Shorter take-off run + margin above stall speed
