PPRuNe Forums - Center of Gravity

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david15

29th Aug 2019 07:35

Center of Gravity

I would like to know for take off we calculate two CGs basically all speeds settings are decided on Take off CG . The zero Fuel CG is also calculated
What is the purpose of Calculating the Zero Fuel CG
Can any one can educate me

weasil

4th Sep 2019 00:13

What airplane type?
Some aircraft with swept wings can encounter an change in CG as fuel is burned. Obviously the ZFW CG is not helpful but there will be a forward most CG location encountered at ZFW + XXXlbs of fuel remaining. IOW you are determining that the CG remains inside the aircraft operating envelope while airborne.

rudestuff

4th Sep 2019 04:13

Because it has to be within CG limits for all possible situations. So in the worst case scenario where you blow through all your reserve fuel, at least it'll fly. Or glide.

david15

4th Sep 2019 07:18

Dear SIr,
Thank you for your reply, but i need some more clarity. what is the importance of Zero fuel CG. Because TO CG is required for the take off, but ZF CG what is the importance

bulldog89

4th Sep 2019 14:03

To be sure you'll be inside the envelope no matter how much fuel you use.
So even if you'll burn every single drop of fuel on board you'll be able to control the aircraft.

JRK	5th Sep 2019 14:39

Quote:

Originally Posted by david15 (Post 10561453)

Dear SIr,
Thank you for your reply, but i need some more clarity. what is the importance of Zero fuel CG. Because TO CG is required for the take off, but ZF CG what is the importance

If you are zero fuel you still need to be properly balanced to glide safely, recover from stall, etc.
So, this metric checks whether on zero fuel you are still within the CG envelope and not out of whack.

Genghis the Engineer

5th Sep 2019 15:57

In light aeroplanes, almost always there's a straight line of CG versus weight in any given configuration.

In airliners, and even more so with military aeroplanes, it's a lot more complex. I used to work with a military aircraft that had a 19 tank system, emptying on an automatic schedule - be thankful it's as simple as it is in light aircraft!

G

david15

7th Sep 2019 12:27

Thank you for your reply

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