I am convinced that "stalled" is the more proper term. You do not say

that your

wing has "slipped" when you fall out of the sky.  At static operation the

angle

of attack on the prop sections is a function of the blade angle, and the

stream

velocity thru the prop. At static that angle on most props is over the

classic 15

degree stall angle, in the inboard steeper part of the prop. With our

props

pitched so we can strive for those nice top speeds near 200 mph, this

represents

quite a large portion of the inner section of the prop. The stalled

portion is

reduced as foward speed is increased, and more of the prop becomes

effective.

This may, or may not be perceptible to the pilot. This same efffect in

marine

props is improperly called "cavitation", and is more pronounced because

the

smaller props are more "twisted" to higher angles. - Vance

Formula racer props are indeed pretty well stalled at static, since they
are small diameter and relatively high pitched. Though the pitch may not
be as high as you would anticipate since their design point is about 4300
rpm at speed. Also, stalled does not equate to no lift (thrust), which is
good since formula planes use a standing start, and initial accelleration
is still important, With the composite props that they are using now, I
would expect that there is a flattening of pitch going on at static for a
little "almost constant speed" effect
Vance

Vance, I was just objecting to the term "stalled", as in a wing being
stalled (air separation and generating little or no lift. I felt that it
was being interpreted as the prop had entered a "dead zone" which I don't
believe is the case. I suspect that it is similar to a cavitating boat prop
in that the fluid (water) is unable to move fast enough to fill the void in
front of the prop, and a vacuum is formed. In this case,it's just very thin
(i.e. high altitude low pres) air in front of the prop and compressed air
behind it. It is still making thrust (lift), or the engine would over-rev.
Just semantics, I think.

Chuck Harbert

 
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