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Cabri G2 Weight and Balance Spreadsheet

G2 Cabri weight balance

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#1 supergokougt

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Posted 16 October 2017 - 10:49

Does anyone have one of those handy w and b spreadsheets for the cabri?


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#2 RotaryRish

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Posted 18 October 2017 - 14:22

Can you not just modify one already built for 22 or 44?

#3 supergokougt

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Posted 18 October 2017 - 16:22

Maybe. But I do not know how to do that. I can sum formula and sort. About my length of skill in excel.

#4 Eric Hunt

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Posted 18 October 2017 - 20:04

Column 1: Item

Column 2: Weight

Col 3:  Arm

Col 4: col 2 x col 3 = Moment

 

Each row is a separate item, starting with Right seat, then left seat, fuel, aircraft wt (from wt sheet in flt manual, includes unuseable fuel and full oil), nav bag, portable gps, survival stuff in cargo comptmt, hip flask, bong etc

 

At bottom of Col 2 is total weight, bottom of col 4 is total moment, then Col 4 / Col 2 will give you the cg arm.

 

Simples.


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#5 supergokougt

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Posted 19 October 2017 - 08:13

Can't wait to see what you come up with.



#6 Eric Hunt

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Posted 19 October 2017 - 16:17

 

 

Can't wait to see what you come up with.

 

Actually, I gave YOU the formula, to see what YOU would come up with.

 

It is also fairly simple to include a chart with the CG envelope displayed, and the aircraft cg moving from takeoff weight to empty weight. 


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#7 takefootoff

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Posted 19 October 2017 - 18:39

Doesn't seem that simple.
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#8 Eric Hunt

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Posted 19 October 2017 - 23:55

it is, even for a hellyklopper pilet.

 

Get it to draw the envelope by feeding in the max AUM as the upper limit, and the empty weight as the bottom line, the most forward cg as the left side, and the most aft as the right side.

 

Then make a line between the takeoff weight/cg and the ZFW/cg, the 2 numbers you extract from the previous table, and you have a nice little box with a line that should stay inside the box at all times. For something more tricky, like a 206L where the fuel cg moves a lot, you also feed in the most forward fuel number into your calcs, and the most aft. Most times you will be on the ground before the most aft.



#9 supergokougt

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Posted 20 October 2017 - 04:59

Here is one for the 44: https://drive.google...X0NVSHItSXJFYVE

 

And the 407: https://drive.google...YzNReUdFWDRQMzg

 

I couldn't find my 206L one so sorry I can not give you that file to edit but I think either of those should work right? The 44 one has a lot going on with it so it may not work. 

 

Might have to download and open with excel not the google sheets to edit properly. I really appreciate all the help guys! 



#10 Wally

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Posted 20 October 2017 - 08:27

Written (created?), used and shared W&b spreadsheets for years.  It's as simple as Eric Hunt posted.  I wanted a little more for HEMS in an Astar, as the patient weight limit requires a couple different calculations.  But it's not difficult in Excel at all.

  1. Aircraft basic weight, moment and arm will not change during the flight being planned for, so start with an input of those data. Arm is pretty useless at this point, but...
  2. Your weight, arm and moment next.
  3. Thw 'moment blocks for each seat, fuel, and cargo is weight  times arm equals.., and you can copy down the column as many times as you'll change configuration.
  4. You will be summing weights and MOMENT inputs, so start creating that column.  Simplest to put the summing blocks at the top of the column and "freeze" that row and the row beneath so those b;ocks are always visible.
  5. Fuel, each tank; passengers, each seat; cargo areas- each, weight times the arm.
  6. The sum of weights is your present weight, the total moments divided by present weight is your cg.
  7. If you want quick reference to fore and aft limits, that's easily calculated for the second 'frozen' row at the top of the spreadsheet.  The limits are graphed but also specifically stated, especially if it changes at some point. 

CG limits  are Easy peasey...

  1. Least weight and forward (or aft) limit ARM and moments, blocks arranged and calculated as above.
  2. Maximum weight, forward arm / moment at that point, as above.
  3. Subtract minimum weight of weight and balance entered above from max
  4. Subtract cg moment limit at minimum from max moment (you're gonna do this for the forward limits and the aft limits)
  5. divide the total moment difference by the total weight limits, this is a rate of change with weight change.
  6. Your actual weight less the fore/aft cg limit multiplied by the rate of change, copied to a second row block to refer fore and aft to existing....

If you're smart enough to fly, you're smart enough to do this on Excel.  After you block this out, run scenarios longhand to check your calculations for fidelity to the real world.  I initially crossed blocks, columns, references, plus/minus, etc.  but this 3rd grade math rationally arranged.  Checking it will show errors, once those are fixed, I had a spreadsheet I could put on my smartphone.  And tinker with, adding calculations I might want sometime...

 

P.S. That rate change for cg limits can also be included for irregular fuel arms, like the Bells.


Edited by Wally, 20 October 2017 - 08:34.

Just a pilot (retired, so I have a LOT of time)...


#11 cherminator

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Posted 21 October 2017 - 13:40

Gyronimo has a weight and balance app for the Cabri G2:

https://itunes.apple...52097?ls=1&mt=8



#12 supergokougt

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Posted 21 October 2017 - 13:58

That's a sharp looking app. I downloaded iBal but my iDisappointment there is error in the calculations. Everything too far forward and over max. Edit: I read the faq of the app and have been able to update the specifics and it is working ok but I need to check math.

Don't worry posters I have been trying to build my own using your instructions. I get it. Teach a man to fish blah blah blah. So far 2 hours of work it is getting close.

Edited by supergokougt, 22 October 2017 - 10:41.


#13 r22butters

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Posted 21 October 2017 - 14:25

So tell me Mr. Cabri, how heavy can the pilot plus passenger be before they hit the forward CG line with no gas?
The only dream I have left is to live long enough to see the pilot shortage. Its been about fifteen years since they first told me it was coming, so,...

Aaaaaaaany day now! :D





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