Piedmont Aviation News - Page 2#
Friday, October 5, 1945
WEIGHT Am BALANCE
by F. H. Ponish
Before proceeding, it is necessary for
you to understand the law of multipli
cation of positive and negative numbers.
Vifhen two nmbers having the same sign
are multiplied, the product is positive.
Ylhen two numbers having a different sign
are multiplied, the product is negative,
/ 3 X / 5 = / 15.
- 3 X - 5 s / 15.
/ 3 X - 5 = - 15.
All items installed from the datum
line tov;ard the propeller are considered
to have a negative arm, and all items
installed from the datum line toward
the tail of the airplane are considered
to have a positive arm. If you install
an item on an airplane, the weight is
added to the AEIV, and such weight will
be "positive," The vjeight of any re
moved item is "negative," because such
weight would have to be subtracted from
the AEV/. Therefore, the removal or in
stallation of any item which tends to
lower the nose of the plane will create
a negative mccient, and the removal or
installation of any item which tends to
lower the tail of the plane will create
a positive moment•
You should now be able to find the
new CG location of an airplane when
negative quantities are involved. The
following example will serve as an
Find the new CG location of an air
plane having an aEVJ of 1050 lbs*, a
CG location of 12,5# and from which the
following items were removed:
Battery; 25 lbs., arm -4
Radio Receiver: 10 lbs,, arm /40,
AEW 1050 12,5
Battery - 25 - 4.0
Radio 10 40,0
New CG Location « 12825
AEW: 690 lbs,
CG location: 15.00,
The following equipment was installed
Air filter-^ 2,5 lbs,, arm -33#
Power pack— 7 lbs,, arm / 9,
Radio Receiver— 4.5 lbs,, am A2,.
The fire extinguisher 7 lbs,, arm
/ 30 — was removed.
Find new CG location.