Lift Augmentation

Question 1

Geometry Limited

Answer 1

Long A/C limit rotation angle therefore AOA

Question 2

Trailing edge flaps - Plain flap

Answer 2

Increases peak suction on the upper surface of aerofoil - Increase in CL - Overall Lift increases
Lower critical AOA (reduce stalling angle - early seperation at boundary layer

Question 3

Split Flap

Answer 3

Strip along the top and hinged below TE

Produces a greater CL max than a plain flap
Produces less turbulence than plain = higher stalling AOA
Has the worst L/D ratio so not used in CAT

Question 4

Slotted Flap

Answer 4

Reenergise boundary layer
Keeps boundary flowing reducing the adverse pressure gradient
Increase in clmax and stalling angle

Question 5

Variable camber leading edge flap

Answer 5

Peak suction increases towards original position
Additional lift without change in CP (no trim change needed)

Lift increases
Delays stall angle
Used in conjunction with TE FLAPS
Preserves stalling angle

Increases LE Radius to encourage airflow along upper surface delaying the separation point.

Question 6

Droop nose

Answer 6

Leading edge flap designed by airbus involving moving the whole leading edge

Question 7

Krueger flap

Answer 7

Leading edge flap that extends outwards and downwards
Increases camber but not leading edge radius
Used inboard to increase lift and ensure wings roots stall first

Question 8

Fowler flap - Camber/Surface Area

Answer 8

Increase in camber and surface area of trailing edge
Addresses issues with peak suction and the increase in APG
Slotted to reenergise boundary layer
Used in most airliners

First stage extends outwards but not so far downwards - more lift for little drag

Question 9

Slat - What does it do

Answer 9

A slot at the leading edge
Reduce size of suction peak (reenergise the flow)
Delayed separation greater stalling angle and greater clmax

Question 10

Summary of all lift devices

Answer 10

TE FLAPS - Greatest CL increase
LE FLAPS - CL increases/no reduction in critical AOA
Slats - Increase the critical AOA

Question 11

Extension of fowler TE FLAP initially on pitch

Answer 11

Nose down pitching moment

Cl increases for minimal drag due to outwards extension but not much downwards movement

Question 12

Auto slat system

Answer 12

Extends automatically when a certain value of AOA is exceeded

Question 13

Leading edge flaps effects on pressure

Answer 13

Peak suction increases without changing CP
Less adverse pressure gradient
Therefore high clmax

Question 14

Trailing Edge and Leading Edge Flaps Working Together

Answer 14

TE provide most increase in CL
LE preserves the stalling angle

Question 15

Slats - Peak Pressure modification

Answer 15

Reduces peak suction by spreading low pressure over upper surface to reduce adverse pressure gradient

Wing can reach greater stalling angle of attack and greater CLMAX

Question 16

Why drag is good on final approach

Answer 16

Improves speed stability
Permit ac to run at higher rpm on approach for a go around

Question 17

Drag created from high lift devices ranked from lowest drag to highest drag

Answer 17

Fowler Flaps - Lowest
Slotted
Plain
Split

Question 18

Effect of flaps on tailplane

Answer 18

Increase in CL from lowering flaps increasing downwash on tailplane
EAOA increases on tailplane resulting in more downforce
Results in a pitch up moment

Question 19

Effect of flaps on tip vortices

Answer 19

Flap extension creates more lift inboard away from tips
Inner part of wing working harder meaning decreased tip vortices

Question 20

A/C Config for worst wake turbulence

Answer 20

Clean/slow heavy a/c

Question 21

Vortex Generators

Answer 21

Thin fins on surface of wing generate small vortices to create turbulent boundary layer

Help keep airflow attached to upper surface for longer
Placed closed to wing tip to delay the stall

Question 22

Flap asymmetrical extension will yaw where

Answer 22

Yaw to the wing with flaps deployed

Question 23

Flaps asymmetry - uncommanded roll where

Answer 23

Roll towards the wing flaps retracted as flap extended wing generating more lift

Question 24

Failure of the slats to extend will….

Answer 24

Affects stalling angle
Fly faster on approach

Question 25

What flap setting would have the greatest affect on CL/CD ratio?

Answer 25

The higher the flap setting the affected CL/CD ratio

Question 26

Slats and AOA

Answer 26

Slat requires a much increase angle of attack to give its CLMAX. Restricted in landing visibility for pilot

Question 27

Asymmetric operation of a slat will lead to a

Answer 27

Yaw moment due to increase in drag

Question 28

Flap asymmetry will lead to

Answer 28

Large rolling moment