RE: HP vs. Brake HP
Engine manufacturers do "elevate" their numbers and at their rated RPM, they are usually unusable for actual flying purposes.
But what Jeff wrote is also quite wrong. Horsepower is everything!
If a given engine makes a given amount of torque, at a given RPM level and another engine gives a larger amount of torque at the same RPM, it will be just as high on its horsepower level, in respect to the "given" engine.
High horsepower levels are automatically high torque levels also, but high torque levels are not necessarily high horsepower.
If your car is at a certain speed, for which you can select any of three given gear ratios, its acceleration will be the highest with the ratio that will have the engine spinning at the highest HORSEPOWER level, rather than the ratio that will have the engine at the highest TORQUE level.
Torque and RPM will be translated into horsepower, to determine the available thrust. Torque alone is quite worthless.
This is because horsepower is equal to torque times speed. Torque is a static value and therefore:
HORSEPOWER IS KING!
This is why an engine is best propped, so in high speed flight, it will spin at the RPM, at which maximum HP was measured, (not the "rated" RPM).
The best measure of an engine's relative performance, is the RPM at which it can spin various propellers, not the rated HP levels its manufacturer advertises.