Im working on my ATP written and im actually trying to learn how to do these these questions rather then just memorizing everything. There are a bunch of weight and balance problems that talk about index arms. I understand MAC and LEMAC and %MAC but i cant figure out how index arms factor into all of it.
just an example question:
What is the new CG if the weight is shifted from the forward to the aft compartment under loading conditions W-5?
The table provides this info for W-5:
Loaded weight = 88,300
Loaded CG(%MAC) = 25.5%
Weight change(lbs) = 3,300
Forward compartment centroid - STA 352.1 and -227.1 index arm
Aft compartment centroid - STA 724.9 and +144.9 index arm
MAC 141.5 inches, LEMAC STA 549.13, and -30.87 index arm
the answer choices are
A. +19.15 index arm
B. +13.93 index arm
C. -97.92 index arm
Since im using gleim to study they tell you the formulas and such to get the answer but i just dont understand what index arms are. The answer is A by the way.
just an example question:
What is the new CG if the weight is shifted from the forward to the aft compartment under loading conditions W-5?
The table provides this info for W-5:
Loaded weight = 88,300
Loaded CG(%MAC) = 25.5%
Weight change(lbs) = 3,300
Forward compartment centroid - STA 352.1 and -227.1 index arm
Aft compartment centroid - STA 724.9 and +144.9 index arm
MAC 141.5 inches, LEMAC STA 549.13, and -30.87 index arm
the answer choices are
A. +19.15 index arm
B. +13.93 index arm
C. -97.92 index arm
Since im using gleim to study they tell you the formulas and such to get the answer but i just dont understand what index arms are. The answer is A by the way.