Looking For W&B Using Arm Instead of Moment

"John T" wrote in message ws.com...


For instance, every W&B graph I've seen (Skyhawks, Skylanes, C150s,
Warriors, Katanas, Tomahawks - all under 35 years old) have shown this graph
using only weight/moment. All the sample loading problems I've seen have
all used moment instead of arm, too.

Which graph are you talking about? The CG envelope itself is almost always
the CG position (arm) versus weight. The other graphs (where you follow the
weight out various lines for the different positions) are just computing the moment
(multiplying the arm for you). The cessna books give you the arms you can use
in lieu of these charts if you really want.

Recent readings revealed folks referencing balance by arm instead of
moment - something I'm not used to doing or reading.

I'm sure you're confused. The CG point is always an arm. A moment tells
you NOTHING about the CG. A moment of 1000 could be 1000 pounds at the
datum or 1 pound 1000 units away from the datum. If you've computed the
moment, you divide that by the weight to get the arm.

It raised the question
in my mind whether there are charts that use weight/arm instead of
weight/moment.

They all do. Googling for cg graph yeilds this page, which is quite representative
of just about every plane I've ever come accross...

http://www.eaa838.org/wtbal.htm

Ron Natalie wrote:


I'm sure you're confused. The CG point is always an arm. A moment tells
you NOTHING about the CG. A moment of 1000 could be 1000 pounds at the
datum or 1 pound 1000 units away from the datum. If you've computed the
moment, you divide that by the weight to get the arm.


The 1986 Cessna Skyhawk manual presents the W&B data in both Weight vs
Moment and Weight vs CG.

John Roncallo