Back to Basics: Engine Power vs Propeller Power

[roadrabbit]

I am researching piston engine operation with constant speed propellers. I have before me a book "Pooley's Multi-Engine Course" by Mike Woodgate and appear to have come across an anomaly.

On page 19, Exercise 22 Part 4B it states:

"when (air) density is greater than the ISA an excess of engine power available to propeller power required will occur. Conversely when density is less than ISA then insufficient engine power will be available compared to propeller power required as illustrated in Figure 4."

However, from my reading, Figure 4 appears to show the opposite. At densities above ISA the dotted line showing propeller power required is clearly drawn showing higher power than the solid line showing engine power available.

Can anyone please clarify?

[A Squared]

Without seeing the diagram you're referring to it's kind of tough to tell what you're asking, or what the book is describing. What is "propeller power required"? Propulsive power required to maintain a certain True Airspeed at a certain altitude?

Start with the basics, all else being equal the engine will develop more power with a higher density than ISA than it will at a a lower than a density lower than ISA .density.

[oggers]

...seems too obvious but this isn't a simple mix up between density and density altitude is it?

[roadrabbit]

I should have posted the image of the page when I asked the question, so here it is.

I gather from the text that 'propeller power required' is that power needed to maintain the propeller rpm from that which is produced for a given throttle setting in ISA conditions, when moving into non-ISA conditions.

Thanks for your interest

[Goldenrivett]

Hi roadrabbit,
I agree that the diagram and text say opposite things.
I think the diagram is mislabeled and you should swap the names of the two sloping plots.