Whoa Math

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Stephan
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Whoa Math

Post by Stephan »

I was entering the pattern yesterday when I hit a bug with my windshield just above the cowling, that must have been the size of a beer can. Doing some quick math in my head, I figured that a prop blade passes in front of the wind screen about 100 times per second, and started to wonder how lucky he was not to get hit by the prop.

2000 rpm x 3 blades / 60 seconds = 100 blades per second.

How much distance do you travel in 1/100th of second? 140 knots x 6076 feet / 60 minutes / 60 seconds = 236 feet per second! Or over 28 inches per hundredth. No wonder everything seems to get by the props.
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Rich
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Re: Whoa Math

Post by Rich »

Same result competing in a balloon busting contest long ago at what is now KEIK. :scratch: Balloons bounced right off the windscreen completely intact. :tap:
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CFIDave
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Re: Whoa Math

Post by CFIDave »

Years ago my DA42 hit a bird at night when on final approach to land. It chipped off paint and damaged the carbon fiber cowling just outside the spinner, yet there was no evidence of hitting any of the prop blades as it passed through the propeller.
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chili4way
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Re: Whoa Math

Post by chili4way »

The last thing that passed through that bug's mind after it passed the prop and hit your windshield?
Its butt!
😁
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Davestation
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Re: Whoa Math

Post by Davestation »

Interesting way of looking at it. I would have just figured the blades overall surface area as a ratio to its entire circle area.
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Lou
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Re: Whoa Math

Post by Lou »

Cool.

I have another one that I wonder about.

129 knots IAS x 6076 / 3600 = 218 FPS. 2450 rpm = 40.8333 rp second. So 64” per rotation.

My question is what is the pitch of the prop? I have always wondered how close to the theoretical pitch the aircraft actually travels. Anyone know?
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