How to measure power in a simple single?

[GayTangle]

Hi, I fly a PA28-180D, with a Lycoming 0-360. It has a non-standard 'climb' pitch prop. I was reading up about leaning the mixture in the cruise in the POH and it cautions against leaning at power settings above 75% power.

Any idea how I work out what 75% power represents so that I know that I can lean the mixture safely ?

Many thanks,
Andy

[Tinstaafl]

The POH will have power tables in it. These specify various altitude/temperature/RPM combinations for different power settings.

[john_tullamarine]

The prop really is not much different to a Prony brake ...

so the figures ought to be fine ..... but ... as a generalisation ... depending on the engine and prop combination, conceivably they might not cover the range of power settings you can achieve and, potentially, you could over boost the thing trying to make RPM for the cruise prop installation .. or overspeed for the climb.

This is why the certification addresses the range of props approved for installation ....

I guess for the flea power engine indicated there won't be much of a problem here .... presuming that the aircraft is not used much for other than circuit and similar local work.

My own experience of climb and cruise props installed in lieu of the "standard" unit is that they are very much a two-edged sword .... you never get a free lunch ...

[john_tullamarine]

BIK,

Are we in disagreement at all ? .. you appear just to be restating my point in different words ?

Of course the load and power will be different in the two cases you describe .. that is the crux of the matter. A different prop provides a different load for the engine ... the problem then is the degree to which the prop torque loads are matched to the engine's capabilities to drive it.

Are you only concerned with the obvious fact that the engine and flight performance numbers are not going to be achieved or have I missed whatever point you are making here ?

[ILS30]

Of course the scenario 2 gets more power;
we should remember that power is defined as the rate of doing work; the rate in this case is the rpm (the same in both cases) and the work is the Force multiplied by the distance.
In the scenario 2 concerned the force needed for getting up both the car and the boat i think is bery much larger that the force for rotating the propeller.
Anybody agree/disagree???:)

[Tinstaafl]

I had in mind props from the manufacturer which would have appropriate tables if there was significant difference

Didn't consider aftermarket STC fittments. Even so, they too should have a supplement if they cause suffiencient deviation away from manufacturer supplied data.

[john_tullamarine]

Some of the installations I have seen, regretably, have had no additional AFM or POH data .....

[Tinstaafl]

Maybe those installations don't have a significant difference from the factory equipment?

Which begs the question: Why bother changing at all if there isn't a significant gain?