Aerodynamics is the study of air in motion and is used to design airplanes.

To get started, you can do the Sailplane Quest. In this activity you will build a hand-thrown glider and learn the basics of airfoil shapes.

Next you can try Cargo Airplane LTD.. In this activity you will design and construct a wing to be used on a fuselage of stock design. The airplane is flown on the Kelvin Power Pole to see who can fly the heaviest airplane.

When you get good at that, enter the Maryland Engineering Challenges Electric Powered Cargo Airplane Challenge. It is like Cargo Airplane LTD. but the planes are bigger and you only get credit for cargo weight.

Or you can try the Historic Aircraft Challenge where you design and build a model of an historic aircraft.

The principles of aerodynamics are also used in other power pole airplane challenges including the Maximum Aircraft Load challege where you try to fly with the highest wind loading and the Maximum Seale challenge where you try and fly with the highest coefficient of lift.

Model rockets are also a study in aerodynamics.

- Adequate lift (L) is required for the amount of weight (W) carried.
- The actual force developed by the wing is up and slightly to the rear so producing lift induces drag (D). This induced drag must be overcome by the thrust (T) of the propeller.
- The fuselage and appendages also create drag.

- Speed (V)
- Angle of Attach (a)
- Wing Area (S)
- Aspect Ratio (A)
- Air Mass Density (r)

The Coefficient of Lift is used to provide efficient scaling from wind tunnel to airplane.

Lift /( V^{2} S) = C_{L}

Similarly for Drag

Drag /( V^{2} S) = C_{D}

Span (b) is the distance from tip to tip.

Chord (c) is the distance from nose to tail.

Area (S) = b · c

Aspect Ratio (A) = b / c

A = b^{2} / S

S = b · (c_{root} + c_{tip}) / 2

A = b^{2} / S

Taper Ratio = c_{tip} / c_{root}

Use geometry to find the area (S).

A = b^{2} / S

- Wings with higher aspect ratios (A) are more efficient because tip loss is minimized.
- For wing operating against a wall, the effective aspect ratio is doubled.

C_{L2D} is the theoretical C_{L} per degree for an infinite airfoil and is ^{2} / 90 or 0.11

Then C_{L} = C_{L2D} / {1 + (2/A)}

And C_{D} = C_{L}^{2} / ( A)

Then L = C_{L} V^{2} S

And D = C_{D} V^{2} S

See properties of air for _{AIR.}

- On real wings, with roots and tips, air flows around the tip from high pressure to low pressure. So there is no lift at the tip and the most lift at the root.
- An elliptical planform is the most efficient, but is difficult to build.
- The same effect can be had with a trapezoidal shape by choosing the correct taper ratio and swept back angle.
- Determine the swept back angle by connecting points of the local chord back from the leading edge.

As the angle of attack is increased beyond a certain point, the flow can no longer remain attached to the top surface. The flow becomes turbulent and lift is lost. This is the stall point. Wings will stall at a C_{L} of between 1.1 and 1.4. With a lower aspect ratio, this will occur at higher angles of attack.

Real Cross Sections have drag at zero angle of attack. Cross-sections with midlines have lift at zero angle of attack.

- The lift on an infinite wing is centered of the way from nose to tail.
- The center of gravity of the airplane must be below the combined center of lift of the wing and the horizontal stabilizer.
- First approximation -- put the CG of the plane about half way back on the wing using balance rig.
- Better approximation --

Balance point is at {S_{WING} Distance of point from origin + SHS Distance of point from origin} / S_{TOTAL}.

- Determine available thrust and estimate possible speed.
- Decide on Trapezoidal or Elliptical wing shape.
- Choose a design angle of attack or CL.
- Shape wing to maximize first estimate of payload from available thrust.
- For Trapezoid

- Choose Chord and Span (cs and
*b*) - Determine aspect ratio (A)
- Calculate CL and CD
- Find ct,, and Area (S)
- Calculate Lift and Drag
- Compare Drag to Thrust
- Iterate on Chord and Span

- Decide on thickness needed for structural strength.
- Decide on Symmetrical or Asymmetrical cross-section. Choose a cross-section (and mid-line).
- Second estimate of payload using Cd that includes fuselage and appendages.
- Refine planform.
- Build and balance.
- Test and adjust.

- Elevator -- pitch down to increase speed
- Angle of incidence -- shim wing up to increase lift
- Balance -- Move payload or wing position to fly level.

cord Swept Back Angle | Taper Ratio |

-20 | 1.0 |

0 | 0.45 |

10 | 0.3 |

20 | 0.2 |

30 | 0.1 |