As for the CFM 56 a very accurate rule of thumb is fuel flow (in kilograms per hour) multiplied by 5.3 is current horsepower output. But this only applies to the CFM 56 engine, taking into account the engine efficiency and all that.
I've been given this after lenghty efforts to find out conversions.
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This Airbus is o.k., but why did it come with a RENAULT key ??