Mick
2011-06-06, 08:59 PM
Just came across this nice graphic to explain and old trick to determine if you have the CoG right or not.
http://img89.imageshack.us/img89/4492/cgtrim.pdf
This works as follows:
1) if the CoG is too far forward then you need lots of up-trim to achieve a nice slow level flight, then putting it in a 45deg dive increases speed and the up-trim causes the plane to pitch up.
2) conversely if the CoG is too far to the rear, not only is the plane difficult to fly but speed increase causes pitch down.
As the diagram says a gentle pitch up is ideal, just enough up-trim to cause pitch up but not wasting energy on holding the nose up and when you increase or decrease power no nasty pitch changes.
Great for gliders and powered aircraft alike, just set the trim for a slow steady speed if under power, always take the power off in the dive.
Try it.
http://img89.imageshack.us/img89/4492/cgtrim.pdf
This works as follows:
1) if the CoG is too far forward then you need lots of up-trim to achieve a nice slow level flight, then putting it in a 45deg dive increases speed and the up-trim causes the plane to pitch up.
2) conversely if the CoG is too far to the rear, not only is the plane difficult to fly but speed increase causes pitch down.
As the diagram says a gentle pitch up is ideal, just enough up-trim to cause pitch up but not wasting energy on holding the nose up and when you increase or decrease power no nasty pitch changes.
Great for gliders and powered aircraft alike, just set the trim for a slow steady speed if under power, always take the power off in the dive.
Try it.