Plane Performance Predictor

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If your browser recognized the applet tag, you would see an applet here.

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This page and this program are very preliminary. All suggestions and comments welcome. Complaints will be ignored. This program was not ment to replace ElectriCalc or MotoCalc but as a programming excersise and to allow more people access to some form of the performance calculations so necessary for successful electric flight.

This program compiles several formulas that I have taken from the net (such as calcul8a.xls, motor.xls (link currently down), Martin Hepperle, and the articles on the Aveox site.), from Bob Kress's article Electric Flight Model Design in Flying Models, and Model Aircraft Aerodynamics by Martin Simons. All formula are approximations - some are better than others. The current, voltages, powers, and RPM are all fairly accurate. Others less so.

Inputs:

• There are a limited number of choices in each section so far. Feel free to type in your own values. However, there is no way at present for you to save values you have entered. Sorry.
• Battery and Prop names are the Garrison Aerodrome part numbers.
• Cell mass does not include the extra weight required to make them into a battery - please include such in the Wire mass entry.
• Resc should include such things as connector, wire, and fusing losses, if known.
• ballast is a placeholder for things like payload or nose (tail?) weight.
• Prop weight should include the spinner/prop adapter.
• Kprop is normally 1.31, but APC props use 1.11, and MA Wood (not electric) should use 1.7.
• All masses for everything except the cells are very approximate. Any 'zeros' are probably due to my not having any information.

Outputs:

• BCS stands for Best Climb Speed and is the speed which produces the best climb angle.
• Climb angle is from the Kress article and seems a bit optimistic. The article claims the formula is only valid for less than about 30 degrees, so it grays out over that number. Also, it will change to orange at a value which feels low for my own plane - your milage may vary. At very low values, it will turn to red indicating a plane which is probably painful to fly, if it's powered.
• CPF stands for Climb Performance Factor and is defined by Kress as a factor that indicates "the best steady climbing ability of the model." He gives the example of a good model having CPF=6.38 and a poor model having CPF=2.10. You might use CPF as an indicator of how well matched the model, prop, motor, and battery are.
• Pitch speed will change color if it is less than the recommended 3x stall speed.
• Watts/pound is based on motor input power. It will change to orange for less than the rule-of-thumb 50 watts/pound and red for less than about 30 watts/pound.
• Run time simply takes the capacity of the cells and divides it by the current. This is overly simplistic, but I do not have a better way of doing this yet.
• Level Flight is the power required to maintain flight.
• L/D max is the maximum Lift to Drag ratio.
• CL(BCS) is the required Lift constant at the best climb speed in order for the plane to support it's own weight.

All suggestions are quite welcome. A source for a good approximation formula for climb angle, climb rate, and drag and/or max speed would be especially welcome.

I do take requests for items to add to the menus. All decisions as to what to include are entirely mine.

This page brought to you by William Sears of
Please address all questions or suggestions to me.

This program is free to use, but you may not copy it, modify it, or sell it in any way. Feel free to link to this page from your own site.

If you wish to support this program, I do web pages, or you can buy Garrison Aerodrome kits (I help make them), or donate any models or modeling items you wish. I mostly do this stuff to support my R/C hobby anyway.