Helicopter Flight Time

1
Helicopter Flight Time

• In teams of 4/5
• Experiment with the design of a helicopter to
  result in maximum flight time
• Money is only available for only10 prototype
  helicopters
• What changes will you test to determine the best
  design?
• Time 60 Minutes

2
Helicopter Design
35 or 45 mm
Paper clip

• Target Maximise flight time
• Y (seconds)
• Changes allowed (Design Parameters)
• Xs (below)
• X1 Wing length 90mm 115mm
• X2 Wing Chord 55mm 65mm
• X3 Weight 1 clip 2 clips
• X4 Stiffness card paper
• X5 Body length 85mm 100mm
• X6 Body width 35mm 45mm
• X7 Wing joint tape no yes

85 or 100 mm
Standard
Maximum
35 mm
90 or 115 mm
110 or 130 mm
3
Helicopter
Wing Joint Tape
4
Strategy and Results
Proto Paper No.
Taped Body Body Wing Wing
FlightType Type
Clips Wing Width
Length Chord Length
Test
Result
1 2 3 4 5 6 7 8 Confirm
5
You have 60 minutes

• You only have 10 attempts
• How do you choose which experiments to run?
• Go !

6
Who had the best time ?

• Did The winner only use 10 prototype helicopters?
• How do they do this in the real world?
• The helicopters cost real money to build
• They cost real time to build
• You cant just keep building new helicopters to
  find the best one

7
One Factor at a Time
8
One Factor at a Time Strategy
Body width
No. Clips
Body Length
Wing Length
Paper type
Wing Chord
Experiment
Tape







1. Standard







2. Paper Trial
3. Clip Trial







4. Taped Wing Trial














5. Wide Body Trial







6. long Body Trial
7. Wide Chord Trial







8. Long Wing Trial







9
Stick With a Winner Strategy
Body Width
Paper type
No. Clips
Body Length
Wing Chord
Wing Length
Experiment
Result
Tape







2.0
1. Standard







2.4
2. Paper Trial
3. Clip Trial







2.2
4. Taped Wing Trial







2.2
5. Wide Body Trial







2.4
6. Long Body Trial







2.6
7. Wide Chord Trial







2.7







3.0
8. Long Wing Trial
10
One Factor at a Time

• The results from changing one factor at a time
  could be plotted as the changes in the output Y
  against the change in a particular factor X
• The One Factor at a Time approach can help to
  find the best design
• But do the settings of the other Xs affect the
  amount of change in Y due to change in the
  selected factor?

Y
Y
Y
Y
Paper type X1
Wing Chord X3
Body length X2
Wing Span X4
11
Will these approaches always work?

• Interactions between factors can and often exist.
  
• Indeed, interactions can have a greater effect on
  the output than changes in individual factors
• One factor at a time experiments cannot identify
  interactions between the Xs
• If the optimum performance depends on
  interactions one factor at a time experiments
  will not find the optimum
• Results can depend on the order of the
  experiments!
• So One Factor at a Time or Stick with a
  Winner do not always work !

12
How do you find the best design ?

• One Factor at a Time and Stick with a Winner
  approaches are good
• They can reduce the number of experiments you
  need to perform
• ie reduces cost
• However they do not always work
• If the factors are inter-related
• Result can depend no the order you carry out the
  tests

13
Test them All

• The best approach may be to test all possible
  combinations
• How many prototypes would this need for our
  helicopter?
• If you assume that each factor can only take on 2
  values
• ie Body width 35mm or 45mm (not 40mm)
• We need 128 prototypes to test every combination
• That is way too many way to expensive

14
How do you find the best design?

• How do you find the best design?
• every time?
• With minimum number of prototypes?
• Lowest cost?
• Look up Design of Experiments on the web
• you might find a way