Canard,tandem wings,three surfaced planes part 1.
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This document discusses the design considerations for canard, tandem, and three-surface wing configurations. Some key points covered include: - Canards provide safety from stall spins at low altitude but have design challenges with longitudinal control and limited directional control due to small tail moment arms. Tandem and three-surface planes have better weight distribution and control surface sizing. - Airfoil selection, wing aspect ratios, and sweep angles must be chosen carefully to ensure the forward wing stalls first and the main wing attains zero lift angle. Downwash effects on lifting surfaces behind also require consideration. - Flaps can reduce stall angles but must be designed strongly and extend simultaneously to maintain lift balance between wings. Control
Canard,tandem wings,three surfaced planes part 1.
- 2. 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
- 3. DISADVANTAGE • Heavily loaded fore plane. • Limited aerobatic capabilities. 3
- 4. AIRFOIL SELECTION • Forewing must stall first. • Main wing must attain Angle of Zero lift first. 4
- 5. E124 is better for forewing. E168 is not good choice for both forewing and mainwing. E197 is good for Main wing. 5
- 6. ADVANTAGES OF SLOTTED FLAPS ON FOREPLANE WING• Stall angle reduced. • CL is increasing. • Reduced Zero Lift angle. 6
- 7. 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 7
- 8. DOWNWASH AND TIP VORTICES •FOR CANARDS •Downwash reduces lift on aftwing at the downwash area of forewing . 8
- 9. • For Tandem Wings • Whole span on the aft wing is similarly affected. 9
- 10. 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
- 11. JOG • Region of main wing which is out of downwash. • Gives adequate lift. 11
- 12. 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
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- 14. Smaller the fore wing farther apart the NP and CG or vice versa. 14
- 15. 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
- 16. TANDEM WINGS • NP and CG should be well forward. • Pusher engine is kept just behind the front wing. 16
- 17. 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
- 18. 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
- 19. 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
- 20. 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
- 21. FLAPS • Flaps needs to be strong as both the aft and front wing provides lift. • Extension must not upset the lift distribution bw wings. • Both side of flaps must be lowered simultaneously . 21
- 22. • Flap deflection reduces the stalling angle for both front and aft spar. 22
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- 24. CERTAIN THINGS WE DISCUSSED EARLIER • Dihedral • Landing gear. • Structural design. 24
- 25. PLOVER. 25