config stab

[Ton van Bochove]

Every time I take off in a cargolux aircraft I get until V1 an EICAS message "config stab". Reason for this message is that the stabilizer is not in the green band while on the ground.
On page 370 of the manual my situation is almost the same as the right picture of the stabilizer trim indicator. It looks like I have to enter a CG value in the FMC but what value???, I can't remember it from PS1.3 but probably it says a lot about the condition of my brain ;-)
Furthermore -as far as I know- all CLX planes have a Weight and Balance System. Could this influence the value of the CG?
Please some advice because the WHOOP is rather annoying;-)

[cavaricooper]

Just add the W&B, or better yet, ask Mr. Bell for his files (G-CIVA). The data you need is on a tab (away ATM but where the Aerodynamic info is).

HTH

C

[Ton van Bochove]

Thanks Carl, I have Stephen Bell his files for all the different AC. I look into the tab!

[cavaricooper]

C

[michelvsr]

Furthermore -as far as I know- all CLX planes have a Weight and Balance System. Could this influence the value of the CG?

Hello,

In real life, we use loadsheet figures to insert Takeoff CG in the FMS. Weight and Balance is not accurate enough, its tolerances are +/- 8tons on the weight and +/- 3% on CG... permitting only to detect a big error.

Michel.

[Ton van Bochove]

Thanks Michel for the answer! I was wondering why a (probably) very expensive WBS is less accurate than a commuter or an electronic calculator.

[JohnH]

Hi Ton,

If you use the fine program designed by Gary Oliver it will give you all the info you are looking for!
More info and tutorial videos can be found at this thread.

http://aerowinx.com/board/index.php?topic=4584.0

John

[Ton van Bochove]

Thanks John! I will check it out!

[Jeroen Hoppenbrouwers]

A W&B system is essentially a weight indicator on each gear leg, plus a computer to do the rest of the calculations. It feels the total weight of the aircraft and it theoretically can figure out where in the hull the weight has been placed, roughly, which leads to a % MAC figure for the center of gravity.

The trick is of course: how to exactly determine the weight and balance of a 744, given 5 landing gear struts, the bogeys, the moving things in the hull, the winds working their way on the barn doors, etc.

For smaller aircraft this is a lot easier to do.

So for larger ones it remains largely manual: what cargo, what fuel, did we put where? This is simplified with tables and simple calculations, but still more accurate. Help from heavier algorithms is welcome, but needs the same basic inputs: what weight, where, plus the empty hull. Therefore the load plan becomes input.

When we install 2 kg worth of equipment, we need to adjust the basic hull weight and balance chart of each airframe we touch.

Hoppie

[Ton van Bochove]

Thanks for the explanation! I think it is more complicated with a Freighter than with a pax AC. Weight and balance is more evenly distributed in a pax version while in a freighter the question is: where do I put the elephant, next to the helicopter or next to the flowers.

[cavaricooper]

Ton-

Graphic and perfectly illustrative of the problem - brilliant!

C