PPRuNe Forums - View Single Post - CG formula anyone ?

1st Mar 2009, 08:48

#45 (permalink)

QAYS

Join Date: Feb 2009

Location: France

Age: 51

Posts: 12

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hello I am back with more explanation :

Note : two different index formulae can be used depending on the unit of item H-arm : length (mor in) or %MAC.

Code:

Index = Weigth *( HarmItem-H25)/C + K = Weigth*(%Mac - 25)*C' +K
With C' = Length of RC/(100*C)

So,

Code:

Index = Weigth*(%Mac - 25)*Length of RC/(100*C) + K
%Mac = 100*C*(I-K)/Weigth*Length of RC + 25

In my first message I have given some information, here new value:

for A320

Quote:

Chord :4,1935
ZFI on loadsheet: 27,6
ZFW on loadsheet: 47930
K :50
C :1000
Harm :17,8015
H25 :18,85
Mac by my equation : 13,85
Mac give by loadsheet : 28,3

For A330

Quote:

Chord :7,27
ZFI on loadsheet :112,8
ZFWon loadsheet :158263
K :100
C :2500
Harm :31,34
H25 :33,16
Mac by my equation : 27,81
Mac give by loadsheet : 27,8

As you can see it for A330 my equation give a good result but for A320 give a wrong result, have you an explanation

I hope my new message in more comprehensible
Best regards

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