The ratio found by dividing the maximum weight of the aircraft by the brake horsepower produced by all the engines.

The following two quotations are word for word.

R.W. Prouty [Even More Helicopter Aerodynamics] Glossary;- "Power Loading ~
The ratio of gross weight to the horsepower rating of the engine."

J. Gordon Leishman [Principles of Helicopter Aerodynamics]:- "Power loading
is the ratio of the thrust produced to the power required to hover."

The above two algorithms can result in quite different answers.
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The university web page you mentioned is interesting. You will notice that he refers a
lot to 'Disk Loading', but nowhere does he mention 'Power Loading'. He
refers to 'MTOW/SHP' and to 'ratio of maximum takeoff weight to rated engine
power'

One could assume that he is equating with Prouty's definition. But, as
Prouty expands on [Power Loading] in his book [Helicopter Performance,
Stability, and Control] he moves towards Leishman's definition.

All very interesting, but confusing?????????

Perhaps helicopter aerodynamists use maximum weight / horsepower to hover whereas the helicopter manufacturers use the airplane definition; maximum weight / brake horsepower.

- or perhaps -

Disk loading = gross weight / disk area

Power loading = gross weight / horsepower to hover

Maximum disk loading = maximum thrust / disk area

Maximum power loading = gross weight / maximum break horsepower

The definition that Leishman uses is much closer to that which we use at Sikorsky. The thrust is the weight, and we use the weight divided by the horsepower to hover, so we agree with Leishman. Prouty's engine rating would yield different values for aerodynamically identical aircraft with different ratings on the engine, which would erode the usefulness of the ratio.