Airport buddies say it should climb out at redline, 2575 rpm's.

 

Simple answer;  "Wrong".

 

The angle of incidence with the relative wind decreases on a fixed pitch
prop as airspeed increases, hence the load on the engine gets less the
fastyer you go. If your climb RPM is redline you could not cruise any faster
than your climb speed without overspeeding the engine.

 

There's been a lot of talk recently about prop pitch numbers.  Here's my
soapbox take on the subject.

 

There are a number of different type aircraft with C85 engines and similar
speed and drag characteristics. Ercoupes, Cessna 120/140, Luscombe,
Taylorcraft, the list goes on.  With the exception of the Ercoupe, they all
call for a 7148 as the standard prop.  There is no reason why the Ercoupe
would be any different.  Ed often refers to his "extreme climb prop", a
7146.  For any other type, this is simply a climb prop. 7144 is extreme, or
a seaplane prop.  The 7150, Ercoupe's "standard" prop is a cruise prop in
anyone else's world.  Now, if the Ercoupe had significantly less drag (and
consequently higher cruise speed) then a higher pitch might be warranted,
but.

 

My take is that someone at Erco was very optimistic, maybe a marketing type.


 

This explains the common complaint of anemic climb performance.  What do you
expect with a cruise prop?  (Calling is "standard" doesn't alter the laws of
physics.)

 

Climbing down off the soap box.

 

John Cooper

Skyport Services

4996 Delaware Tnpk

Rensselaerville, NY 12147

518 797-3064

www.skyportservices.net

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