Required performance increase with added weight, AS350B3
In reference to performance planning in an AS350 B3; Let's say you arrive over your LZ and it is a "Hover Hole" in and out. You conduct a HOGE power check 500 feet above the LZ and determine you have enough power, at your current weight, to conduct the operation. This, however, is not taking into account how much of a load you are going to pick up(let's say 200 lbs). My question is, how do you account for the increase in power that will be required and by how much? For example, how much more %Ng and %Torque will be required for HOGE with the addition of 200 pounds. I've heard some use the formula that 1% Ng is equal to 200 lbs and 1%Torque is 70 lbs. So in the case presented, it would require 1% additional NG and almost 3% additional torque.
Yes, I know that is what charts are for and I know the B3 has a VEMD screen that lets you performance plan, but I'm curious for impromptu planning, etc. Such as, I'm just out of the yellow on the gauges during the HOGE power check, but how much further will I be into the yellow on take off with the additional weight?
So, I would like to hear your experiences and how you determine the needed power increase. If you can back it up mathmatically, even better. Thanks