Weight & Balance and Microsoft Excel
 

Hey Team,

Does anyone have any information about the use of Microsoft Excel and A/C Weight & Balance Calculations? I can't find information on the FAA site that it can be conducted by using COTS Software, namely Excel.

Any assistance will be much appreciated!

Regards,
Alex

If you can do it on a sheet of paper .. you can do it in Excel .. just be wary of errors in operation. Unless the system is approved for your Authority .. it will hold no more validity than doing it yourself longhand on a bit of paper ..

I can't speak to the formal approval of Excel as the W&B means, but I certainly have seen it used many times, and have used it myself for many different aircraft. It is my opinion that as long as you can demonstrate that you did an accurate and correct W&B, the authority is not going to question how you did it, as long as there is evidence that you did! (Print a copy)

I particularly like that you can condition the cells to give you red text if something is out of limits.

Always do a reality check of the outcome, does it make sense? Particularly if you're having to leave seats empty to make your C of G, does it seem logical? What do other pilots of that type say? I have found many errors in the basic W&B for an aircraft over the years, which resulted from errors at weighing, or calculation errors for small amendments. Most commonly are not weights, but errors in fuselage station locations for calculation, or scale location. If you're finding errors you can't explain, go back a few W&B for that aircraft, and review the results...

kazbak91,

Your location says NZ...It was years and years ago, but when I worked at the Aero Club in Rotorua we used an Excel spreadsheet for W&B calculations on our C172's and PA28's. CAA seemed to think it OK and the regs in NZ paralleled the FAA regs at the time (I'm sure they still do).

IIRC, we did demonstrate to CAA that a simulated Excel calculation came to within a reasonable result of the same calculation done via the POH charts. That was done very informally during one of their routine visits. We spent more time talking about the smell in Rotorua than we did the spreadsheet, which should indicate just how much they cared.

It's too bad I don't have the spreadsheet anymore, or I'd send it to you. I do remember that we had to program the spreadsheet such that Excel did not round - I think it was one or two decimal points. Otherwise it would give us an out-of-balance result where the POH indicated it was (just) inside limits.

It's just that from my regulatory perspective, if an excel spread sheet is used to compute W&B calculations, the failure of the software won't result in a catastrophic event IAW FAA FAR25,27,23 etc..1309 System Safety Assessment. By catastrophic I mean the loss of aircraft and life. However it is the unannounced misleading or incorrect information provided by the excel W&B calculations that can have aircraft level implications.


So if the crew insert the wrong take-off weight and speeds into the Flight Management System, from such erroneous calculations, the aircraft may not be able to take off in time...


Quite the tricky topic indeed.

That's where the reality check that Pilot DAR mentioned needs to come in. Any computer based program can have errors - the old garbage in, garbage out adage applies.

You don't program the spreadsheet and go. You run a lot of different scenarios. Ones that will not cause issues and ones that you know before you even enter the numbers would never work. You then compare all that against the POH or AFM. You get comfortable enough that you know it will work when properly used.

I've used a company approved. specialist spreadsheet on the 74F. But could still do a manual L/S (never ever used), but it meant I could spot an error, as someone previously said GIGO.