Ch 16 - Lift Augmentation

Question 1

Basic Trailing Edge Flap

Answer 1

Increase local CLmax
Increase local camber
Decrease critical angle (separation happens earlier)

Question 2

Split Flap

Answer 2

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

Question 3

Leading Edge Flaps

Answer 3

Greater peak suction which increases the differential pressure

Higher CLmax
Higher critical angle of attack

Question 4

Kruega Flap

Answer 4

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

Question 5

Fowler Flaps

Answer 5

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

Question 6

Slots and slats

Answer 6

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)

Question 7

Lift augmentation of TO Drag

Answer 7

T/o drag is highly undesirable

Extra lift is good as it means you can increase the TO mass and stall speed decreases

Question 8

Effect of flaps on tip vortices

Answer 8

Wing tip vortices decrease but more vortices are created by the flaps themselves

Question 9

Vortex Generators

Answer 9

Designed to reenergise the air which delays separation

Which leads to a higher AoA and a higher CLmax

But induces a lot of drag

Question 10

Abnormal operation

Answer 10

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