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Note: These instructions refer to an older version of this calculator. You can still download it from the above link, and view version 3’s features on the Weight and Balance Calculator B3 release page.
Do you run a weight and balance before every flight? Or do you just guesstimate how much fuel you can carry and assume you’ll be close enough to being in CG? I know guys who don’t do a W&B except for check rides. Not good enough for me. Limitations are limitations, and early in my training I developed worksheets for each helicopter so that I had the baseline CG values for every flight. From there it was easy to add a weather check, and HIGE/HOGE calculations into my pre-flight routine.
Now, there are plenty of these already out there. Maybe your flight school has one. I put some real thought into this though to make it user-friendly and packed with features. First, on the Conditions page, you fill in the red boxes with the basic empty weight and arm data. Password protect the worksheet and nobody can inadvertently alter those values. Next, enter all the variable data into the green boxes: pilot and passenger weight, baggage weight, optional equipment (default is installed), and fuel. After the passengers and baggage weights are entered, the Calculator displays the maximum allowable fuel weight (which may be greater than the fuel capacity). The CG graph is updated automatically with the take-off (solid green) and zero-fuel (open white) conditions. Endurance is based on a an editable burn rate (usually 8-10 gph). This is a quick and clean way for students to see how CoG shifts and changes during flight. By unlocking the red cells, they can develop a better understanding of how weight and arm are related to payload capacity.
I thought about hiding the calculations page altogether, but as a learning tool it’s great. Your students can complete calculations by hand and then check their calculations there. For a beta version, this is also a good troubleshooting tool.
The student worksheet is meant to be used day-to-day for manual calculations. The graphs, arms, weights, capacities, and limitations are reproduced from my POH, but you must confirm that they are consistent with your aircraft’s POH. All cells are unlocked and the sheet is unprotected so you can enter the data for your aircraft. The rest of it is simply an intuitive template for doing W&B calculations and gathering pre-flight data. It should also print out very nicely.
A few disclaimers. I have tried it with several helicopters and it works fine. They are all Beta IIs though. I also run Windows Vista and Microsoft Office 2007, so I have no idea how the Calculator will work with your system. I do know–and this one’s important kiddies–that you must enable active content and macros. The ultra-histrionic Office 2007 automatically disables these features unless you tell it to enable them. I also locked the worksheet so that you’d have to read the instructions. Getting the unlock is easy, but it does require an active internet connection.
I’d like to see some ideas for practice problems that force students to develop a working knowledge of CG. The calculations themselves are only tedious, but applying them to real-world scenarios is what I’d like to get at. In the screen shot, for example, I have to take 240-lb Bubba on a 1.25-hour flight. Can I do it without him having to leave his boots behind?