Hi all,

In the second revision test, question 7, it gives an Echo with gross weight 2550kg and moment index of 620. It asks what the least weight is that can be added to place the aeroplane withing CoG limits, however if I calculate (2550-2360)*0.27 + 2400, it gives an answer for the forward limit being 2419, placing the plane within both forward and aft limits (the CoG is at 2431mm)

My question is, how come when I plot 2550kg and moment index of 629 on the CoG graph, it does not fit in the envelope??

I hope I'm not missing something too fundamental

Thanks a lot

The graph plots Gross Weight against Total Moment Index.

If you plot gross weight (2550) and total moment index (620) on the graph, the point where the two lines intersect is just outside the envelope (the forward limit)

The current CoG is: (620*10000)/2550 = 2431 mm
The current forward limit: (2550-2360)*.27+2400 = 2451 mm

So the aircraft with current gross weight and moment index is not within the CoG limit.

Since the problem relates to the forward limit AND you are adding weight, you can only work out the answer using the graph not the flow chart. As the 'least weight to be added' is requested, the most aft position in the aircraft (the rear locker) would produce the greatest effect with minimum weight.

Hope this helps.