Saunders Roe SRA1

When I was working on the RC-3 I found a very interesting looking plane and thought that someday I would also create it for FlightGear.  I'm talking about the Saro SRA1, it is a jet powered seaplane developed by the British shortly after WWII.  They were inspired by some Japanese seaplanes.  3 prototypes were built, but two of them were lost.  Here's a shot of the model as it is now.  It flies pretty good and the mooring system is working.  No cockpit yet and lot's of issues to work out but it's pretty neat.  You can download it here if you want to try it out.  https://dl.dropboxusercontent.com/u/84585372/SRA1_20140808.zip

Aerodynamics Calculator

Way way back when I first started with FlightGear I found it useful to record information for an aircraft in development.  After some research I decided to use the JSBSIM FDM instead of YASIM.  They both do what they do well, JSBSIM just seemed a better fit for me at the time.  Back to my point.  When creating a model there is a whole bunch of information to record.  For example: aircraft length, wingspan, height, empty weight etc.  It requires a lot of patience and research, but sometimes you just can't find the information you are looking for.  In the JSBSIM manual they suggest using a good paint program and using the pixel locations to make measurements for various purposes.  You have to make a bunch of measurements.  What is my solution you ask?

I made a spreadsheet to help keep it all together.  What I do is get the best to scale and highest resolution 3 view drawings of a plane.  Usually you have some known distances so using the paint program (I use Paint.net for its power and simplicity)  you record those pixel locations and then create a scale factor.  Once you have that you can make accurate (pretty good) measurements.  I have found by taking out all measurements to 2 places I can get good results.

Through time the spreadsheet has expanded to include much more.  I wanted to calculate the center of gravity so through the RC Aircraft Proving Grounds CG Calculator I found a way to do it.  I copied a lot of their work (I give them full credit) just in case the website went down and put it into the spreadsheet.  I was going to put a link here but the site seems to have an issue at the moment.  I hope it is not down permanently

I also found a moment of inertia calculator and have also incorporated it in the spreadsheet.  Information for this came from http://www.aircraftdesign.com/.  I also went to a library and checked out Dr. Raymers book.

The whole point is that my Aerodynamics calculator can be used to setup an aircraft JSBSIM FDM with good results.  I have found by tweaking an FDM after using Aeromatic to initially get things going with my calculator that aircraft fly well.  It usually requires quite a bit of work and for each aircraft the spreadsheet may need customizing, but for me I think it works well.  Here a link to the calculator https://dl.dropboxusercontent.com/u/84585372/Calculators.zip.  This is a zipped file with the calculator for 3 different aircraft so you can see how it is used for different aircraft.  Enjoy!    


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