Project Autorotation Drag coefficient Rotor acts as a parachute with drag coefficient of order 1 The...
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Project • Autorotation Rotor R r Body Tail T l T w B l R w PaperClip
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
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 C D as function of geometry would
be more accurate than approximating fall time, but this was not
borne out.
Slide 4
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!
Slide 5
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.