Ch 16 - Lift Augmentation Flashcards
Basic Trailing Edge Flap
Increase local CLmax
Increase local camber
Decrease critical angle (separation happens earlier)
Split Flap
Increases CLmax
Increased critical angle compared to plain flap
Hard for air to overcome the pressure gradient
Separation point is further away
More draggy than plain flap
Might be a good thing for planes landing on AC carriers
Leading Edge Flaps
Greater peak suction which increases the differential pressure
Higher CLmax
Higher critical angle of attack
Kruega Flap
Shape leading edge device
Increases the camber
Encourages separation for the inboard section as the air is working harder, loses energy and separates earlier
Boeing 737 747
Encourages stall at certain part of the wing as it promotes more desirable stall characteristics
Fowler Flaps
Increases surface area
Increased CLmax
Increases area and camber by moving aft and then progressively down
1st 50% of travel increases lift
2nd 50% of travel drag increases rapidly (form)
Has Slots usually
Slots and slats
A slot has a Fixed gap in Aerofoil section which renergises air which means it is better able to resist separation
- Lots of drag
A solar is retractable slot
- Used on motor airlines (hydraulic and electric)
Lift augmentation of TO Drag
T/o drag is highly undesirable
Extra lift is good as it means you can increase the TO mass and stall speed decreases
Effect of flaps on tip vortices
Wing tip vortices decrease but more vortices are created by the flaps themselves
Vortex Generators
Designed to reenergise the air which delays separation
Which leads to a higher AoA and a higher CLmax
But induces a lot of drag
Abnormal operation
Complete flap failure leads to a faster approach, larger landing run and a higher AoA
Failure to retract after TO will reduce lift to drag ratio as well as decreased range and performance,
Flap protection equipment - Flap extension speed (VFE) will alert you to an incorrect flap setting for phase
Asymmetry - sensors will stop flap operation if they detect asymmetric deployment
Flap asymmetry is worse than slat asymmetry