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# Apache Helicopter

Posted on 2003-10-25
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I don't know if this is the right Topic, but I think it is, it has something to do with science.

I was curious if anyone knows how fast the propellers of an Apache helicopter go, like RPM's a minute or whatever, and how long are they, I guess if you could tell me the total (wingspan?) that would be okay.

I asked my parents this and they said just write on your homework, "Really damn fast and pretty damn big.", so if you think the same thing I am going to tell you the samething I told them.

This is not a homework problem!  I am just curious, I had an idea.  If this is not good enough for you, then I will come up with an excuse.  I am coming up with a very hard Calculus problem that I am trying to stump my friend with.  How's that?

Mark
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Question by:simpsons17371
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SethHoyt earned 150 total points
The rotor speed is 4.86 Hz according to http://www.vibrationdata.com/Newsletters/April2003_NL.pdf

This translates to 292 RPM, consistent with the 289 RPM used in this simulation of the Apache's rotor system:

http://www.lions.odu.edu/~dkunz/conf/2001ApacheRotorRSC.pdf

The rotor diameter is 14.63 m, according to http://www.zap16.com/mil%20fact/ah-64%20apache.htm

That gives a rotor tip speed of about 4.86 * (2 * 3.14 * 14.63) = 447 m/s = 1000 mph

-Seth
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The last bit should be:

That gives a rotor tip speed of about 4.86 * (3.14 * 14.63) = 223 m/s = 500 mph

-Seth
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You have to add 273 MPH if it's going at full speed forwards, so the leading edge is going 773 MPH, just below the speed of sound at its operating height.
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