Originally Posted by
Nick Thomas
I have been thinking (always dangerous!) about CofG movement.
You got me thinking too... equally dangerous, since it's not my 'subject'
I understand the concept that the CofG must be positioned for the particular phase of flight. What I have been wondering is on shorter charter flights was there a mininium ammount of fuel that had to be loaded just to always have enough fuel for CofG movement ie was it possible to be in a position where trip fuel, fuel to an alternate etc was less than the fuel required for CofG movement after take off?
First simplistic answer...
If the charter flight did not involve a supersonic flight, then of course it wouldn't have been a problem, you would just have loaded enough fuel into that vast collection of tanks to maintain a 'subsonic' CG.
So, second answer, which is what I think you're thinking of: the case of a short charter with a supersonic "loop" over the Bay of Biscay, as both BA and AF did quite a number of times, with less fuel.
This is where I start thinking... and I admit I may be wrong.
Take a normal transatlantic flight, with all the tanks full at take-off.
By the time you started the supersonic acceleration (so with still a lot of fuel forward, only the fuel used in take-off and subsonic climb no longer there) the 10-odd tons in tank 11 (the trim tank in the tail) were already enough to shift the CG backwards to what was needed when supersonic.
So, with a smaller fuel load, getting the CG backwards to the right position would already be easier, even without fully filling tank 11. And of course no problem returning to the 'subsonic' CG.... plenty of space in the already partly empty tanks..
So I think the answer to your question is "no".
CJ