CG in %MAC = (Fuselage Station - 387.7) / 1.6622
Weight and balance in the G450 is pretty close to being a no brainer, so long as you don't carry any particularly heavy baggage loaded in unusual places. You need to consider weight and balance to compute takeoff trim, and of course you will need to have the numbers if you are flying under 14 CFR 135. For a primer on how to do all this, see: Flight Engineering / Weight and Balance Principles.
[G450 AFM 1-03-70]: Zero fuel gross weight CG must be within the allowable zero fuel gross weight CG envelope. The fueled airplane CG will then be within limits for all fuel loads.
G450 Cabin Layout (Example)
G450 Weight and Balance Envelope
G450 Baggage Compartment Limits
The baggage compartment is limited to 65 lbs per square foot. (If you stand with your feet together, you actually exceed that limit!) The total limit is based on the space available after outfitting and will be placarded, for example:
- Compute the moment for each seat and the baggage by multiplying the weight by the arm and dividing by 10,000. For example, Seats 1 - 2: 200 x 180 / 10,000 = 3.6
- Add all the payload weights to get 2,100 lbs and that to the BOW to get 45,902.
- Add all the payload moments to the BOW moment to get 2084.63
- Divide the ZFW moment by weight (2084.63 / 45,902), multiply that by 10,000 to get 454.1
- Using the formula in the weight and balance book, extract shown below, compute the ZFW %MAC (454.1 - 387.7) / 1.6622 = 39.94
- Using the envelope chart in the weight and balance book, extract shown below, determine the forward (36.2) and aft (43.0) limits. Ignore the T/O %MAC as it has no meaning in this airplane. (G450 W&B Manual §2.4: "If the ZFGW C.G. is within the envelope, the fueled aircraft will be within FAA approved limits for all fuel loadings.")
- Using the elevator trim tab chart in the QRH, NC-7, determine the trim setting of 8 units.
- Ignore the Max Takeoff Gross Weight, since they didn't provide the en route fuel burn and you need that to know how heavy you takeoff.