CPL performance echo question
Was wondering if someone could help me with this. In a Bob Tait practice exams I keep getting a similar question which I keep getting wrong and I am getting very frustrated
as I recall the question gives the information of an echo aircraft with a weight of 2655kg (main tanks full) and a moment of 666 then askes what is the max fuel that can be added to the auxiliary tanks. The way I have approached it is to work out the CG which comes to 2508, and as that is within the forward limit range (2400-2560), and it is adding weight, I believe that it can only be solved by using the loading sheet/graph. I am sure I am doing this correctly by plotting the weight, and moment, then adding another point for a moment derived from a hypothetical weight (100kg) and aux tank arm, then joining two points and marking the weight where the line crosses the forward limit of the envelope. Am I missing something? or am I just getting the wrong answer due to inaccuracies in plotting of the graph?