Winter / Focus / Prop Drag

[White, Chris]

I'm a freelance CFI and I know it works too....  The way I try and think of
this is that any time a propeller is turning there is airflow disturbance
and lift being generated in some fashion. Whether the result is positive
thrust or negative thrust is a function of airspeed/prop/prop rpm.   A
non-turning propeller creates zero-lift and frontal area drag.

I'm sure there is an aerodynamicist (and probably some within the company I
work for....) who could put a formula to the effect we use in the
aero-modeling of our flight simulators, but I've never felt the need to have
that explanation.  Since I'm not an aero-engineer it would probably be
beyond me anyway, I like thinking in laymen's terms:)
Sorry, just couldn't resist adding my 2 cents.

Chris White
Owasso OK.
NSRCA 3601

-----Original Message-----
From: discussion-request at nsrca.org
[mailto:discussion-request at nsrca.org]On Behalf Of Chuck Czarnik
Sent: Thursday, December 04, 2003 8:20 AM
To: discussion at nsrca.org
Subject: RE: Winter / Focus / Prop Drag



Autogyros depend upon a windmilling prop..  They don't fly too well with
a stopped rotor.  I'm not an engineer, but this satisfied me years ago
when this debate came up in some of the GA circles I was in.

Hope this helps, Chuck

-----Original Message-----
From: discussion-request at nsrca.org [mailto:discussion-request at nsrca.org]
On Behalf Of Adam Glatt
Sent: Wednesday, December 03, 2003 10:16 PM
To: discussion at nsrca.org
Subject: Re: Winter / Focus / Fuel/Electric.

John, experimentation or theory, though I have yet to hear anyone 
qualify the statement that a slow turning prop causes more drag than a 
stopped one with an explanation.

John Ferrell wrote:

>As I am sure you are aware, full scale pilots have been taught for many
>years that a windmilling prop creates more drag that a stopped prop.
>
>How do you determine what rpm generates the most drag?
>
>John Ferrell
>6241 Phillippi Rd
>Julian NC 27283
>Phone: (336)685-9606
>johnferrell at earthlink.net
>http://home.sprintmail.com/~johnferrell/dixiecompetitionproducts/
>NSRCA 479 AMA 4190  W8CCW
>"My Competition is Not My Enemy"
>
>
>----- Original Message ----- 
>From: "Doug Cronkhite" <seefo at san.rr.com>
>To: <discussion at nsrca.org>
>Sent: Wednesday, December 03, 2003 4:28 PM
>Subject: RE: Winter / Focus / Fuel/Electric.
>
>
>  
>
>>Well.. you fix that by setting a good idle speed before you take off.
You
>>never let the motor stop in flight for a few reasons.. 1) as you
>>described, it looks weird.. 2) a stopped prop is not the best solution
for
>>downline breaking.. 3) the start/stop is hard on the gears..
>>
>>-Doug
>>    
>>
>
>
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>  
>


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