Less of a question, just want to confirm my understanding.



Effects of fuel burn off on CoG from main tanks
The main tanks are at 1780mm arm which is forward of the CoG range (2400/2560-2680).
Any decrease in weight would move the CoG towards the rear. See grey graph on the above diagram.

If the aircraft is already loaded towards the forward limit,it will remain within the allowed CoG range.
If the aircraft is already loaded towards the rear limit it will exceed the allowed CoG range.

Effects of fuel burn off on CoG from aux tanks

The auxiliary tanks are at 2800mm arm which is rear of the CoG range (2400/2560-2680).
Any decrease in weight would move the CoG towards the forward. See orange graph on the above diagram.

If the aircraft is already loaded towards the forward limit, it will remain within the allowed CoG range.
If the aircraft is already loaded towards the rear limit, it will remain within the allowed CoG range.

Just want to confirm if this is correct.

Also the fuel policy states that the main tanks should be filled first and the aux tanks should be used only to accommodate fuel that wont fit into the mains, The tanks should be burnt in the reverse order. The designer, of course, has ensured that if you are on the aft limit at ZFW, filling the mains will never take you beyond the forward limit. The main tanks are simply not big enough to let that happen.

Therefore, if you are on or near the aft limit at ZFW, you know that you can safely fill both tanks, If you are on or near the forward limit with full fuel, you know you can safely burn all of the fuel.