The 2 numbers you are quoting are the TO ratings of the engine not the MGB.
From memory only there is no difference between MCP and TO power in a B or a BA. 83 and 88 % resp i.e you can fly it all day at TO power - other limitations being considered of course. This equals 532 HP on a B and 564 HP on a BA.
Also in a B2 there is a limitation on MCP and TO power versus speed i.e TO power may only be used up to ~ 40 knots. It probably equates to only being able to use the extra power over a BA in the hover.
The other issue you may have is that the Q meter indications i.e. % versus pressure from the torquemeter may be different on a 1B engine and a 1D1.
Also keep in mind Q for a constant RPM versus collective pitch angle is non linear.
If your question is in response to the NZ CAA slingload with pax operations the "power margin" is virtually impossible to work out with the data you have available. You could be Ng limited - how would you work that out? It would have been much easier if they had imposed a weight margin from the published performance data.
Thanks for the reply. Was hoping for an easy answer but guess nothing is ever easy. I was talking about the engines, isn't the MGB the same and rated for much higher power anyway.
You say 88% Ng = 564hp =MCP=TOP for the BA. Where does the 641hp for TO figure come from that is often published?
Can you use Ng (being the most common first limit reached) and compare the performance of the two that way, somehow??.
Nothing to do with human slingloads which I understand to be limited to 80% of the charted HOGE weight limit. Just trying to be able to say that B2 is ??% more powerful than the BA, at the same AUW using max power available, ie. TO power.