Howdy,
I've take the following notes from Bob's notes on the Echo;
* CofG moves FWD as Aux Tanks are used.
* Main Tanks are well ahead of the CofG.
* If on the Aft Limit, the Fwd Limit moves forward faster than CofG does as Aux Tanks are burnt.

Having considered all that, confirming the CofG moves Aft as Main Tanks are used/burnt?

Just getting back to this after 6 months of not looking at it post 2 fails and due other commitments.
Any rules of thumb appreciated.

PJ332,

If you review page 14, para 2.4 of the performance supplement, it states that the main tanks are filled first, then auxiliary tanks. So it follows that you must burn all Auxiliary fuel before burning mains fuel.

So if your Echo has a Zero fuel weight C of G on the Aft C of G limit, adding mains fuel moves the C of G forward, and then adding Aux Fuel moves the C of G Aft. So when cruising, burning Aux fuel first moves the C of G forward, and then burning Mains fuel moves it Aft to remain in balance. If this did not happen, the aircraft would not be certified to fly.

I hope that helps.

W

Hi Wayne,
Thanks for the response, makes sense.
I had answered it that way in one of my failed exams and got it incorrect which had me revisit it. But perhaps there was a more correct answer.
Cheers,
PJ

Be aware, though, that Bob's booklet is fine but the CASA booklet carries the day in the exam and the latter doesn't fuss about the order of fuel loading and usage.

John