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Project

Project. Autorotation. Drag coefficient. Rotor acts as a parachute with drag coefficient of order 1 The helicopter starts by falling like a stone, and then (around 1/3 of the way)reaches steady state velocity. At steady state drag is equal to weight, W=D, to calculate CD need to know V.

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Project

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  1. Project • Autorotation

  2. Drag coefficient • Rotor acts as a parachute with drag coefficient of order 1 • The helicopter starts by falling like a stone, and then (around 1/3 of the way)reaches steady state velocity. • At steady state drag is equal to weight, W=D, to calculate CD need to know V. • Crude approximation neglects initial transient using V=fall-time/height. Need to estimate error. • I hypothesized that approximating CD as function of geometry would be more accurate than approximating fall time, but this was not borne out.

  3. Uncertainties • Flying uncertainties include the way you hold the helicopter when you drop it, measurement uncertainty, and ambient conditions like wind and temperature. • Possible important uncertainty is the helicopter getting beat up after each drop • Manufacturing uncertainties include variability in materials, dimension and rigidity • The larger the uncertainty the tougher your job and the more helicopters you will need!

  4. Two project report mantras • Document for future you: Five years from now, if you pick your own project report, you should be able to understand everything without having to go elsewhere for information. • Make it easy for me: 30% of your grade will be based on completeness and ease of understanding of your report. Most important, if your results are wrong, make it easy for me to spot why they are. Otherwise you force me to assume that you made a very serious mistake.

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