ADVANTAGES Provides safety from stall spin at low altitude.

Load Sharing- Reducing Main wing area.

Main wing spar can be Out of the way.

Smaller, Lighter ,more compact airplane.

2

DISADVANTAGE• Heavily loaded fore plane.

• Limited aerobatic capabilities.

3

AIRFOIL SELECTION• Forewing must stall first.

• Main wing must attain

Angle of Zero lift first.

4

E124 is better for forewing.

E168 is not good choice for

both forewing and

mainwing.

E197 is good for Main wing.

5

ADVANTAGES OF

SLOTTED FLAPS ON

FOREPLANE WING• Stall angle reduced.

• CL is increasing.

• Reduced Zero Lift angle.

6

REYNOLDS NUM, ASPECT

RATIO & PLANFORM• High ARs reduces stall angle (needed for

foreplane).

• High ARs results into lower RNs. So also Landing

speed reduces.

• Chords of less than 5 inches are avoided.

• Low ARs increases stalling angle (needed for main

wings).

• Shorter Main wingspan improves roll response.

• Forward sweep on foreplane promotes to that wing

stall first.

• In Three surfaced wing its beneficial for horizontal

tail plane.

• Forward sweep in forewing should not more than 5

degree on the 25% MAC Line.

7

DOWNWASH AND TIP

VORTICES• FOR CANARDS

• Downwash reduces lift

on aftwing at the

downwash area of

forewing .

8

• For Tandem Wings

• Whole span on the aft

wing is similarly

affected.

9

IN 3-SURFACED PLANES• Horizontal Tail is affected by

the downwash or reduced

angle.

• For tandem wings of equal

span the aft wing’s AoA

should be increased by the

down wash angle

generated by fore plane

• For Canard’s and three

surface airplanes

shadowed portions of the

main wing should have an

increase in AoA that’s equal

to the downwash of the

Fore plane.

10

JOG• Region of main

wing which is

out of

downwash.

• Gives

adequate lift.

11

LOGICAL DESIGN STEP• PU and CU selection.

• Weight Estimation from previous Graph.

• Wing loading selection.

• For level-flight speed front and aft wing’s AoA need to be

known.

• The NP and CG location.

• Total wing area must be divided into to part.

12

13

Smaller the fore wing

farther apart the

NP and CG or vice

versa.

14

CANARDS• If flaps are used need some balancing lift. Causes problem in

pitching moment as dive or stall.

• Both sets of flaps must be extended simultaneously for balancing.

• For small canard like 15% aft wing area needs more powerful flap

and also disadvantage is that in shorter tail moment arm.

• This can be solve by sweeping back the aft wing. And placing

vertical surface at the wingtips.

• Sweepback reduces lift.

15

TANDEM WINGS• NP and CG should be

well forward.

• Pusher engine is kept

just behind the front

wing.

16

THREE SURFACED

PLANES.• Effect on front and aft wing will be same.

• NP and CG will be rear ward(compared to

canard).

• Need to be considered-

ARs and Planforms.

Longitudinal and vertical separation.

Airfoil selection.

17

THREE SURFACED

PLANESI. Aft and main wing provides all the lift

needed and elevators control pitch and

trim.

II. Canard wing share most of the lift with

horizontal tail.

18

LONGITUDINAL

CONTROL METHOD• Slotted flap would be better for dominant

pitch control.

• Flap on the forewing and simultaneous up

or down action of aileron.

• For tandem wings partial span of forewing

or plain flap would be better.

• For three surfaced plane tailplane’s

elevator controls the pitching moment.

19

DIRECTIONAL CONTROL

• Vertical tail design and spiral stability.

• Tandem and 3 surfaced planes have enough TMA

for adequate sized surfaces.

• Canard doesn’t have sufficient TMA.

• Recourse is that-

• Larger vertical surfaces.

• Aft wing sweepback

• Wing tip vertical surfaces.

20

FLAPS• Flaps needs to be strong as both the aft

and front wing provides lift.

• Extension must not upset the lift distribution

b\w wings.

• Both side of flaps must be lowered

simultaneously .

21

• Flap

deflection

reduces the

stalling

angle for

both front

and aft spar.

22

23

CERTAIN THINGS WE

DISCUSSED EARLIER• Dihedral

• Landing gear.

• Structural design.

24

PLOVER.

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