1. Cargo Airplane Challenge
Engineering Design

2. Electric Cargo Airplane
Students design and build an electric cargo airplane that carries the maximum amount of payload
Grade Levels:
6-8 and 9-12
Contact:
Mr. Tom Milnes
JHU Applied Physics Lab

3. Engineering Design Process
Identify the Problem
Identify Criteria and Constraints
Brainstorm Possible Solutions
Generate Ideas
Explore Possibilities
Select an Approach
Build a Model or Prototype
Refine the Design
NASA Engineering Design Process for Secondary Students

4. Identify the Problem
Design and construct an electric powered cargo airplane.
Teams are responsible for building wings, fuselage, landing gear, and cargo.
Airplane will be weighed after flying without cargo and then again after flying with cargo.
Goal is to carry as much cargo as possible.

5. Identify Criteria…
Written Report (20 points)
Oral Report (20 points)
Design & Construction (30 points)
Performance Demonstration (30 points)

6. … and Constraints Length, width, and height all < 3 ft.
Specified motor (Kelvin #850647).
Provided propeller or substitute own.
Power Pole and transformer.
Tether—10 ft. to motor.
No lighter-than-air devices or commercial kits.
Judges may modify as needed to ensure a fair competition

7. Brainstorm, Generate, Explore, Select
STEM involved in this challenge
History of flight
Parts of an airplane (see glossary)
Forces on an airplane (lift, weight, thrust, drag)
Basic airfoils
Angle of attack and stall
Wing geometry (span, chord, area, aspect ratio, taper ratio) for rectangle, ellipse, & trapezoid.

8. The Four Forces on an Airplane
The lift (L) of the wing overcomes the weight (W) of the airplane.
In level flight L=W.
If L>W then climb. If L<W then descend.
Rearward force of drag (D) is a byproduct of lift and is overcome by the thrust (T) of the propeller.
In most airplanes, thrust is much less than weight, i.e.
T/W<<1 and L/D>>1
In our case 1 ounce of thrust can easily power an 6-ounce airplane.

9. STEM—Basic Airfoils

10. STEM—Basic Airfoils

11. STEM—Basic Airfoils

12. STEM—Basic Airfoils

13. STEM—Basic Airfoils

14. STEM—Basic Airfoils

15. STEM—Basic Airfoils

16. STEM—Basic Airfoils

17. STEM—Basic Airfoils

18. STEM—Basic Airfoils

19. STEM—Basic Airfoils

20. STEM—Basic Airfoils

21. STEM—Basic Airfoils

22. STEM—Basic Airfoils

23. STEM—Basic Airfoils

24. STEM—Basic Airfoils

25. STEM—Basic Airfoils

26. STEM—Angle of attack (α) and Stall
α is the angle between the wing and the incoming air.
When the angle of attack is too big (>≈12°) the wing stalls;
Airflow detaches from top surface → eddies
drag increases, lift is lost
airplane slows down and stops flying.

27. STEM—Wing Geometry for Rectangle
On real wings (with roots and tips) air flows around the tip from high pressure to low pressure. As a result, there is no lift at the tip and the most lift at the root.
• Rectangular wings are easy to build, but they are not very efficient since area near the wing tip does little work.

28. STEM—Wing Geometry for Ellipse
Elliptical wings use area in the theoretically most efficient way, but are hardest to build.

29. STEM—Wing Geometry for Trapezoid
Trapezoidal wings are almost as efficient as ellipses but easier to build.

30. Aircraft Controls Rudder controls yaw (right or left)
Ailerons are used to turn
Flaps add lift for takeoff and landing
Throttle controls rate of climb
Elevator controls airspeed
You can also adjust
Balance
Angle of Incidence

31. Build a Model or Prototype
Design Main Wing—You Pick
Span (b) (cannot be more than 36 inches)
Planform shape (rectangle, ellipse, trapezoid, or some combination or other shape)
Chord (c), or Ct and Cr, or Cr and Taper Ratio
Airfoil shape
Material and construction method

32. Build a Model or Prototype
Design, cut, and shape
horizontal stabilizer/elevator
vertical stabilizer/rudder.
Landing gear (wheels, wire, aluminum strip).
Drill hole in fuselage
Attach landing gear and motor mount.
Solder 18 inch leads to motor and add propeller
Construct the main wing.

33. Test it—The Leader Board
Fly M-T.
Balance
Elevator
Fly with Cargo
Add at center of balance
3 laps or 2 minutes

34. Refine the Design Add cargo weight and try to fly with new cargo
Modifying (e.g. reshape or add flaps)
Design and construct an entirely new wing
Modify the fuselage/landing gear/empennage
Try a different propeller
Keep improving and retesting until time runs out

35. Present your Results Oral Report Written Report
I have students sketch each wing and indicate
Span
Chord
And calculate
Area
Aspect ratio
Coefficient of Lift extension activity
Time 3 laps
Weigh plane
Calculate wing area
Calculate CL

36. “The Kit” Doesn’t Exist, But…
Item
Cost
Motor
$ 0.85
Propeller
$ 0.75
Landing Gear Wheels
Fuselage
$ 0.44
18” of Wire
$ 0.45
Tray for Tail
$ 0.07
Motor Clip with 6/32 Machine Screw and Nut
$ 0.70
Thin Wire for Landing Gear
$ 0.22
¾” x 8” 21-Gage Aluminum Strip for Landing Gear
$ 0.56
Coffee Stirrer and Rubber Band
$ 0.02
6” x 36” Pink Foam Blank
$ 0.95
Total
$ 5.76
Add Sand Paper, Weights, More Pink Foam, etc.
$ 9.79