How much info do you want?

Each aircraft has a Datum Point which is an arbitrary point along the Longditudinal axis which is used as a basis for all the calculations.

The Longditudinal axis is a line from the front to the rear of the aircraft (the other two axes are the Vertical and the Lateral, this way, three dimensional motion and control input can be referenced to an axis)

Generally in Single Engined Cessna aircraft, the Datum point is the very front of the aircraft. Other manufacturers use other points, the fiewall, wherever, it really makes no difference.

Each station has what's called an Arm which is the distance between the "centre" of the station and the datum.

Any cargo, fuel or pax at each station creates a force relative to the Datum in proportion to its weights and to its Arm. This force is called the Moment. Remember a seesaw (teetertotter in the US) where the fat kid sitting closer to the fulcrum balanced the skinny kid all the way at the end?)

Any station forward of the Datum Point will have a negative Moment, those aft of the DP will have a positive Moment.

So all you have to do is to multiply out the different weights by their arms to create a series of moments, add the moments up and divide by the total weight to find the CG of the aircraft (relative to the Datum of course)

Consider this example:

Code:

```
Item Weight(lbs) Arm(ft) Moment(ft/lbs)
Empty wt 3000 0.5 1500
Pilot 170 2 340
Fuel 200 1 200
Baggage 50 4 200
----- ------ ------
3420 2240
```

the CG of the aircraft can be seen to be at 2240 / 3420 = 0.65

If the aircraft has CG range of say 0.62 to 0.66, This calculation shows it to be within range for CG.

There are formulas for what happens if you take some cargo out of one section and place it in another, but that's all just simple trignometry.

Generally a person is considered to be 170 lbs, though I think they just increased that. Fuel is 6lb a gallon, but I'm not sure about jet fuel. Jets typically quote their fuel in pounds not gallons anyway.

HTH

Liam