rpetersson

20th Nov 2011, 16:28

Ok - struggeling to understand what i have done wrong here, hopefully any kind souls can enlighten me...

-------------------------------------------------------------------------------------------

Q: An aeroplane has a zero fuel mass of 47800 and a performance limited take-off mass of 62600kg. The distances of the leading edge and trailing edge of the MAC from the daturm are 16m and 19.5m respectivly. What quantity of fuel in Imperial gallons , must be taken up to move the CG from 30% to 23% MAC if the tank arm is 16m aft of the datum and the fuel SG is 0.72?

-------------------------------------------------------------------------------------

I caluclated the CG at 30% MAC to 17.05m and at 23% to 16.805m.

So the formula should be:

New Total Mass = Old total Mass + Change in mass

(47 800+m)*16.805 = 47800*17.05 + (16*m)

Answer= 14 547.8kg

And converting this to Imperial gallons gives 4444

But the right answer should be 4455..

What on earth am i doing wrong??

-------------------------------------------------------------------------------------------

Q: An aeroplane has a zero fuel mass of 47800 and a performance limited take-off mass of 62600kg. The distances of the leading edge and trailing edge of the MAC from the daturm are 16m and 19.5m respectivly. What quantity of fuel in Imperial gallons , must be taken up to move the CG from 30% to 23% MAC if the tank arm is 16m aft of the datum and the fuel SG is 0.72?

-------------------------------------------------------------------------------------

I caluclated the CG at 30% MAC to 17.05m and at 23% to 16.805m.

So the formula should be:

New Total Mass = Old total Mass + Change in mass

(47 800+m)*16.805 = 47800*17.05 + (16*m)

Answer= 14 547.8kg

And converting this to Imperial gallons gives 4444

But the right answer should be 4455..

What on earth am i doing wrong??