Weight & Bal Calc ASK-21

If you do your own calculations, please be aware of a very common error. Some manuals use a formula for C/G which uses the distance between the main wheel and the tail wheel. Others use a formula that use the distant to the tail wheel from the datum. Either one will work, but if you use the wrong distance to the tail wheel it creates a 3-5% error in the final C/G. It usually goes unnoticed as it is small, but I have seen this even from official W&B sheets.

Matt H

On Sunday, October 25, 2015 at 3:34:21 PM UTC+1, Matt Herron Jr. wrote:
If you do your own calculations, please be aware of a very common error. Some manuals use a formula for C/G which uses the distance between the main wheel and the tail wheel. Others use a formula that use the distant to the tail wheel from the datum. Either one will work, but if you use the wrong distance to the tail wheel it creates a 3-5% error in the final C/G. It usually goes unnoticed as it is small, but I have seen this even from official W&B sheets.

Matt H

And do NOT trust an old and unkown W&B. I have seen to many of them that has been wrong, both in mass and distance and therefore in CG, even the original factory W&B can not be trusted as it sometimes is pre-made prior to finishing of the glider.
Do it your self properly once. Any change in instruments, ballast, trim weights, etc can later on be calculated.

/Per