CG Calc

RC Model Aircraft Center of Gravity Calculator v3 (replaces v1.x and v2.x)
This app is COMPLETELY free, no ads and no in-app purchases but please have a look and support me by buying my RC-E Calculator which includes wing loading, flight time, prop thrust, energy density, current draw and many other calculators: Google Play Store Link ► RC E Calc Pro

Please email me if you have a problem or suggestion.
This app was built with MIT App Inventor, the permissions* (see below) required are the defaults. This app has been published on Google Play since 2012 and since it is still here you can be assured that Google Play has no problems with it.
Please see the Privacy Policy if there are any further concerns.
No data is collected from your device guaranteed!


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This may prevent your plane from crashing!

"A nose-heavy airplane may not fly well, but a tail-heavy airplane may fly only once."

This app will calculate the POSITION of the Center of Gravity (CG or CoG or Balance Point) measured back from the leading edge at the wing root in the units of your choice.

Enter your measurements for:
- tip chord length,
- root chord length,
- sweep length and
- required CG percentage (eg 28%)

of your model airplane and then the CG, wing area, geometric mean chord and tip-to-root chord ratio will be calculated automatically.

You can use inches or centimeters and the result will be in the units you used (don't mix units though).

A too rearward CG position can cause unrecoverable (potentially fatal) instability!

25-35% recommended for most conventional wings, 12-18% for pure flying wings, 15-19% for Delta wings.

This calculator uses the Neutral Point, the AIRCRAFT'S aerodynamic center (AC), as a reference point to calculate the CG range. It uses a well known, simple but fairly reliable method of determining the CG of a model aircraft.

Thanks for downloading, comments and ratings welcome.

Version history:

V3.01
- improved layout
- new image
- improved wording

V2.3:
- improved layout
- improved images
- new instruction page
- corrected wording

Version 2.2:
- Resize & refit for tablets
- Refit text flow for large numbers
- Center everything
- Minor layout improvement & bug fixes

Version 2.0+: implemented due to Google licensing changes.
- No longer requires a button tap to calculate, calculates automatically after the all the fields are filled.
- Added wing Area calculation
- Changed layout for ease of use/visibility
- Fixed small bugs

(*This app requires the following default MIT App Inventor permissions:

android.permission.INTERNET - to check for updates and so that the screen's background image property can be set to the URL of an image on the web if there is a background image
android.permission.WRITE_EXTERNAL_STORAGE - to move the app to EXT SD on your phone if necessary.
android.permission.READ_PHONE_STATE - to check for incoming phone calls and then hide the app if necessary.
android.permission.READ_EXTERNAL_STORAGE - access the app on EXT SD if necessary.)