Lift Augmentation

Question 1

Why do we need lift augmentation devices

Answer 1

Slower flying speeds
Reduced AoA near min flying speed on aprch
Increased drag on aprch
Higher power setting, for safety

Question 2

Trailing edge flap

Answer 2

Increases camber and CL max
Cp moves Aft increasing the overall production of lift
Reduces stalling AoA due to a steeper adverse pressure gradient

Provides a pitching up pitch moment

Question 3

Spilt flap

Answer 3

Reduces flow separation
Increases CL and CLmax
Increases stalling AoA, due to the adverse pressure gradient being blocked
High drag

Question 4

Leading edge flap

Answer 4

Increases camber by lowering the leading edge
Provides modest additional lift with no movement of CP so it produces no pitching moments
Stagnation point remains on the leading edge
Leading edge radius is increased so airflow remains attached for longer
Delays stalling angle

Question 5

Droop nose

Answer 5

Leading edge flap used by airbus

The whole leading edge goes down

Question 6

Krueger flap

Answer 6

Ensures root stalls before the tip so it provides a natural stall warning
Extends downwards but keeps a relatively small radius
More distinctive stall speed

Question 7

Fowler flap

Answer 7

Increases aerofoil camber and surface area
Massive increase in CL and min increase in drag
Slots are in the gaps which extend

Question 8

Slot

Answer 8

Re energises the airflow over the wing and increases camber

Higher CL and CLmax and stalling angle

Question 9

Slat

Answer 9

Leading edge device which extends to create a slot
Reduces the suction peak to spread it over a greater area thus delays the onset of separation and increases the stalling AoA.

Question 10

Why not we use loads of flap for t/o

Answer 10

High drag impedes the t/o run, leading to a longer t/o

Question 11

The L/D ratio

Answer 11

Measure of the wings efficiency

Question 12

Effect of flaps on climb and gliding

Answer 12

steeper descent and reduced gliding range

It will also reduce the climb angle.

Question 13

The aerodynamic effect of deploying flaps

Answer 13

Will cause the nose to pitch down

Question 14

The downwash effect of deploying flaps

Answer 14

Will cause the a/c nose to pitch up due the effect of downwash on the tail plane

Question 15

What happens to vortices when flaps are delayed in straight and level

Answer 15

Induced drag will remain the same due to straight and level
Vortices around the flaps will increase due to more lift being produced
Vortices at the tip decrease due to less lift being produced in those areas

Question 16

Vortex generators

Answer 16

Re energise the airflow over control surfaces

Airflow remains in contact with them

Question 17

Streaks

Answer 17

Produce vortices at high AoA and direct airflow over the wing

Reduces interference drag
Reduces disturbed airflow over the wing

Question 18

FES

Answer 18

Flap extension speed

Question 19

With no flap landing distance increases by what

Answer 19

10% faster = 20% longer landing distance

Question 20

Flap asymmetry

Answer 20

Will flip a/c

Question 21

The effect of trailing edge flaps on the angle of glide

Answer 21

They will degrade it

Question 22

Effect of sweepback angle on high lift devices

Answer 22

They will become less effective with an increasing sweepback angle