Weight & Balance and CG for airplane

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Level 3

727 points

Weight & Balance and CG for airplane

I was wondering, before I start working on this myself, if anyone has has a good template for calculating the weight and balance of an aircraft. I know it's pretty simple math, but I was also hoping to create a CG graph, based on the numbers input into the chart. Since I'm not very good with those formulas and getting them added to a chart, I was hoping someone may already have something similar.

I wanted to do this for our flying clubs' airplanes, and wanted to make them a little nicer than just a plain spreadsheet.

Thanks,

Mike

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Posted on Apr 8, 2011 11:28 AM

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Answer 1

jaxjason

Level 5

5,063 points

Apr 8, 2011 11:43 AM in response to MLadd

you might find it hard to find a numbers specific tempalte for this, but almost any excel file that is just using formulas (i.e. no macros) to do the job should work in numbers.

I googled "airplane CG calculator filetype:xls" and it came up with a whole lot of templates to use.

Jason

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Answer 2

MLadd Author

Level 3

727 points

Apr 8, 2011 1:13 PM in response to jaxjason

Thanks. I have found those. But I was also hoping to turn the answers into a CG Moment Envelope chart also. There are some of these in excel also, but I just don't know how to make the calculations to create the correct slopes on a chart in Numbers (or in Excel). I guess they just used hard coded values to create the original lines to form the "box" or envelope, then plot the CG point on the graph based on the weight and moment.

Similar to this:
http://www.flightlearnings.com/wp-content/uploads/2011/03/9-8.gif

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Answer 3

MLadd Author

Level 3

727 points

Apr 11, 2011 8:12 PM in response to MLadd

I am now able to get the Moment envelope line graph created. Now I need to plot the two points from the Weight & Balance calculation. The problem is, it seems to think it's two different charts. Can I not use one group of data from a table to create a line graph on a chart, then simply plot two points from the Weight & Balance on that same chart?

I can't seem to figure out how to use two different types of data, formatted in a different way, on the same chart.

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Answer 4

Apr 12, 2011 5:46 AM in response to MLadd

Hi M,

Sometimes the easiest way around limitations in a single chart is to combine two charts by overlaying them.

Without seeing specifically what you are working with it's difficult to give you advice. I've been following your posts but don't have anything else I can offer at this point. I checked your example links, but to me they're just pictures, without seeing the formulas and data behind them.

Jerry

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Answer 5

MLadd Author

Level 3

727 points

Apr 12, 2011 6:44 AM in response to Jerrold Green1

I believe overlaying 2 charts is what I would want to do here.

Every plane has a center of gravity which moves based on how much weight is in certain areas. I have been able to plot the line for the envelope (which looks like the image I posted earlier) based on 5 pairs of coordinates on a scatter graph, and connecting them with a line. These numbers will always stay the same for a particular aircraft (but I want to do this for 6 or 7 aircraft) and it only changes if the something physically changes on the airplane (like new instruments). I wanted to be able to change these numbers easily if something does change down the road

Now, based on the user input values for how much weight is at a specific area (front seat, rear baggage area, etc) I can calculate the CG by getting the total weight and the total moment and plotting the intersect of those two points on the Moment envelope chart.

So yes, I suppose I'm looking to overlay the intersect of these two values on the chart I already created that outlines the moment envelope.

If you look at the example I posted earlier, plot a total weight of 2,367 and a moment of 105.2, follow the red lines to the intersect and since that point is within the Moment envelope, the plane is good to fly.

Hope that helps explain.

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Answer 6

Apr 12, 2011 6:57 AM in response to MLadd

You should be able to do that particular chart in one object. The axis labels will probably easiest if done manually, and that allows you to do some scale customization that would be difficult in a combined chart.

All your straight lines can be drawn in a Scatter Chart. If you have any specific questions, just ask.

Jerry

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Answer 7

Jun 19, 2011 5:14 PM in response to MLadd

How's your project coming? I am in the process of purchasing a Cessna 172, and am hoping to calculate weight and balance on my iPad as part of preflight. I've been working the approach you've outlined, but don't have confidence in my math.

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