Marc Protacio
MSD : SAE Aero Aircraft Design & Build
Preliminary Wing Design
Parameters:
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Number of Wings
Vertical (z) Position
Horizontal (x) Position(TBD in Horizontal Stabilizer Design)
Planform Shape
Airfoil
Incidence (setting) Angle
Aspect Ratio
Taper Ratio
Sweep Angle
Twist Angle
Dihedral Angle
Overall Wing Geometry
Control Surfaces (TBD in Control Surfaces Design)
Number of Wings: Monoplane (1 Wing)
Justification:
a)
b)
c)
d)
e)
f)
Conventional and is the most simple case
Most aircraft entries in the competition employ a single wing configuration
Lower overall structural weight
Lower overall drag
Lower overall pitching moment
Ease of manufacture
2. Vertical Wing Location: High Wing Configuration
Justification:
a) Majority of cargo-transport aircraft have a high wing configuration
b) Allows for wing box to be assembled as 1 piece and attached (removable) to the top of the
fuselage. Removal of the wing box gives easy access to the payload bay.
c) Allows for strut installation if structurally required.
d) Increases lateral stability through dihedral effect.
e) More wing planar area available, and therefore more lift generation, as opposed to wings whose
halves attach to the fuselage.
f) Allows for fuselage shape to be more aerodynamic as wings do not have to attach to it.
4. Planform Shape: Rectangular -> Double-Tapered (Scheumann Planform)
Justification:
a) Initial rectangular section increases overall planform area and thus lift generation
b) Double taper is used to generate as close to an elliptical lift distribution as possible, resulting in
less lift-induced drag.
c) Overall planform shape resembles that of the “Scheumann Planform,” which experimentally
shows that flow separations do no propagate longitudinally along the wing.
d) Stall occurs at the root first, allowing for a longer duration of aileron control and recovery
e) Relatively lower bending moment due to decreasing structure outboard
5. Airfoil: S1223
All "high-lift, low-Re" airfoils form the UIUC airfoil database were investigated.
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High Stall angle for higher operational angle-of-attack range.
Higher CLmax results in lower stall speed, aircraft can fly slower and still maintain required lift.
Gentle stall characteristics
Lower pitching moment means lower tail size resulting in lower weight and less materials.
Minimize drag coefficient so less thrust is needed to obtain required velocity.
CH10:
E423:
S1210:
S1223:
S1223 RTL:
S1223 Airfoil Comparison:
6. Wing Incidence:
The wing incidence angle should be set to achieve the ideal lift coefficient corresponding to the
minimum drag. Specifically, the incidence angle should occur when (Cl/Cd) is maximum, generating the
maximum overall efficiency. However, because this is a heavy-lift competition, the incidence angle will
be selected such that the wing can lift the maximum payload at cruising flight, while retaining the
fuselage centerline parallel to the flight path.
7. Aspect Ratio: 6-9
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As AR is increased, aerodynamic features of a 3D wing get closer to 2D airfoil.
As AR increases, the wing effective angle of attack is increased (less downwash effect).
As AR is increased wing lift curve slope increases towards airfoil lift curve slope.
As AR is increased, stall angle is decreased towards airfoil stall angle -> choose tail with smaller
aspect ratio so it stalls later for control.
5. As AR is increased, wing CLmax increases towards airfoil Clmax.
6. As AR is increased, the wing will become heavier and have a higher bending moment at the root.
7. As AR is increased, the wing induced drag decreases.
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As AR is increased, the effect of downwash on the horizontal tail is decreased.
As AR increases, the aileron arm will increase resulting in more lateral control.
Lower AR wings are easier to manufacture.
For a low-subsonic transport plane, the AR is recommended to be 6-9.
8. Taper Ratio: 0.4
1. Taper ratio will improve the lift distribution so that it is more elliptical.
2. Taper ratio will reduce bending moment at the root as center of mass is closer to the fuselage
centerline.
3. Taper ratio will result in the tip stalling later than the root because it will have a lower Re, and
therefore a lower Clmax, allowing for lateral control recovery.
4. Wing mass moment of inertia along the x-axis will decrease resulting in more lateral control.
5. A more elliptical lift distribution results in lower lift-induced drag.
6. A more elliptical lift distribution will increase the wing lift curve slope towards the airfoil lift
curve slope.
7. A more elliptical lift distribution will reduce the bending moment at the root because there is a
higher load density closer to the fuselage centerline.
8. It is recommended that a taper ratio of 0.4 is chosen as this will most closely reflect an elliptical
lift distribution.
9. Sweep Angle: N/A
1. For high-subsonic to transonic flight, a leading edge sweep angle delays the critical mach
number to a higher value, thus allowing for higher flight speeds before drag divergence.
2. Wing lift coefficient decreases, and therefore L/D ratio (efficiency) decreases
3. For flight regimes less than Mach 0.3, no sweep angle is recommended
10. Twist Angle (Geometric-angle and Aerodynamic-airfoil): N/A
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Geometric twist utilized to lower the angle-of-attack at the wing-tip to avoid tip stall
Lowering the angle-of-attack however will result in lower overall lift generation
Can use airfoil with higher stalling angle at the tip to avoid geometric twist
Both geometric twist and aerodynamic twist creates manufacturing difficulties
11. Dihedral Angle: N/A
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Improves lateral stability of aircraft
Reduces effective planar area and thus lift generation
Reduces aircraft lateral controllability
Creates additional manufacturing difficulties
Because a high wing configuration is chosen which already provides an inherent dihedral effect,
no additional dihedral angle is chosen to make aircraft more laterally controllable.