Trivia Question

Lance F

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Lance F
Ok, at what RPM does does a windmilling prop turn flying best glide speed (say 90 kts)?

I know this is type specific, engine condition specific and prop specific, but before I had hard engine analyzer data to look at this condition I wouldn't have had the slightest idea.

Prize for closest answer...let's see...how about first in line at Gaston's for Sue's hors d'oeuvres?
 
Lance F said:
Ok, at what RPM does does a windmilling prop turn flying best glide speed (say 90 kts)?

I know this is type specific, engine condition specific and prop specific, but before I had hard engine analyzer data to look at this condition I wouldn't have had the slightest idea.

Prize for closest answer...let's see...how about first in line at Gaston's for Sue's hors d'oeuvres?

At the RPM that generates the least drag on the prop blades.
 
Lance F said:
Prize for closest answer...let's see...how about first in line at Gaston's for Sue's hors d'oeuvres?

500rpm
 
1350?
Which plane are you talking about that has a best glide of 90kts?

EDIT: 1350-1400. my final answer.
 
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More details if you want them. Mooney M20J; Lycoming IO360-A3B6D compressions 76, 76, 77, 75 all /80; McCauley 2 blade prop B2D34C214-B/G90DHB-16E (no feathering...I wish); engine developing 0 power; prop governor knob fully forward). Anybody that's already weighed in is free to try again if this info changes anything.

Answer will be posted in 24 hours.
 
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Lance F said:
More details if you want them. Mooney M20J; Lycoming IO360-A3B6D compressions 76, 76, 77, 75 all /80; McCauley 2 blade prop B2D34C214-B/G90DHB-16E (no feathering...I wish); engine developing 0 power; prop governor knob fully forward). Anybody that's already weighed in is free to try again if this info changes anything.

Answer will be posted in 24 hours.

I'll go 1225 +/- 50.
 
Is this a pick-a-number lottery? I'll go with 1234 RPM.
 
I would go with...hmmm....750.
Yes Regis that's my final answer.
 
I don't think it's very fast so I'm guessing 499. :dunno:

Probably way off.
 
After putting my limited engineering and diagnostics skills to use, taking into consideration that the prop is 2 bladed and the cylinder compressions are in the normal range, I'm inclined to say that the windmilling is between 600 and 700 rpm.

In other words, this was a SWAG. :D
 
What... is the air-speed velocity of an unladen swallow?

What do you mean? An African or European swallow?

:dunno:
 
I know someone who turned off his engine in a viking (io520) to test glide range in various configurations of prop and throttle setting, should I cheat and ask him?
 
and the winner is.....David Westner who guessed 1350 - 1400. Our esteemed Chip Gibbons gets second with his "about 1400."

The average rpm of the 91 data points was 1354 and the mean was 1360. There was a fair amount of scatter giving a standard deviation of 78.6. Maximum was 1559 and minimum 1160.

Methodology: The "event" lasted 11 minutes. I threw out the data points right at the beginning where the engine was slowing down from normal and at the end when I was slowing down on final.

Knowing this number has no useful value that I know of, but that's why we have Hanger Talk.
 
Wow! I won something!:yes:

I probably won't be at gastons, so the second place winner should get the prize.

I cheated anyway. Thank you MSFS2004.
 
deafsound said:
Wow! I won something!:yes:
I cheated anyway. Thank you MSFS2004.

Clever lad.

Man, Bill Gates knows EVERYTHING.
 
Michael said:
You don't turn 2200 to fly L/D max. It'll be whatever you need to turn to fly L/D max minus a bit for prop slippage.
 
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