Paul wrote:
A fixed pitch prop has only one load for each RPM.
A variable pitch prop and engine dyno has many loads for the same RPM.
What ever is going on I could not get it to run well
on the dyno for what ever reason.

Unconfuse me Paul,

Fixed pitch = I got that, But variable pitch has many loads I don't
understand.

If I start at a steady state cruise and touch nothing, power and load
must be equal.

If I pitch up slightly ( without any throttle position change ) I change
this equibrilum. Prop load would BEGIN TO increase, but SIMULTEANOUSLY
as the RPM began to fall, the flyweights in the prop governor react
allowing oil movement to decrease prop pitch which ( and here's where
the confusion is ) should keep the load on the engine the same.

If this senerio is correct, then for any given power setting the load on
the engine will be as stable as a fixed pitch. The only difference is
that the pilot gets to pick the power/RPM relationship ( within
reason---detonation being one of the reasons )  whereas the fixed pitch
pilot has only one power/RPM relation available at any given RPM and
must decide between cruise performance,ie. buy a cruise prop, or climb
performance, ie buy a climb prop.

None of this will help with your dyno tuning problems, but I'm trying to
get a handle on controllable pitch props when used with Tracy's engine
controller and a standard aircraft prop governor. Please
comment.                                     Thanx,         Dave M


Me too and we are still collecting data.  It is also usual
for the pilot to increase the pitch and load the engine down for cruise.
A fixed pitch prop loads the engine 100% only at maximum speed.
The rest of the time there is potential power in the engine that
is not being used. This has a major effect on the BSFC and the MPG.
See the last attachment. It is a complicated subject.

Paul Lamar ...No rotor no motor.

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