TWIN
COMANCHE CIR
WEIGHT AND BALANCE - VISUAL PLOTTER
The chart showing
the approved Weight vs. Center of Gravity envelope and the Visual Plotter
contained in the following pages will enable the pilot to graphically determine whether or not his proposed
loading will fall within the allowable envelope. They will also allow him to easil!. determine the necessary
adjustments to make if his first proposed loading is not within this envelope.
When plotting successive points. the pilot is graphically adding weights and corresponding moments.
As the weight increases. through the addition of various items of disposable load. rhe pilot will see the shift
in the center of gravity.
Going clockwise around the envelope, the heavy lines represent allowable weight at the forward C.G.
limit (81 in.). the maximum allowable weight as the C.G. shifts rearward, the
gross
weight (3600 lbs.). and
the maximum rearward C.G. limit (92 in.).
The sample problem which follows, will demonstrate the use of the Visual Plotter included with this
manual. The pilot is not restricted to adding the items in the same succession as outlined, since the sample
problem illustrates only one of many possible loadings. When plotting successive items of disposable load.
the items most important to the mission under consideration (range or payload) may be added first.
SAMPLE PROBLEM
Assume (for demonstration purposes only) a Basic Weight and C.G. of 2330 pounds at 83.6 inches.
Assume the disposable load to consist of pilot and 3 passengers (170, 170, 180. 160 pounds) 86 pounds
baggage and maximum allowable fuel.
(1)
(2)
(3)
(4)
(5)
I
(6)
On the Weight vs. C.G. Envelope opposite 2330 pounds locate the C.G. at 83.6 inches (Point 1).
This point represents the-Basic empty airplane with oil and 6 gallons of unusable fuel included.
Lay the transparent Visual Plotter over the envelope (always keep BASE LINES parallel to
horizontal or Weight ordinates) and plot along the proper scale the combined weight of the front
seat occupants (340 pounds - Point 2).
From Point 2, following the proper scaie of the Visual Plotter, plot the combined weights of the
rear seat occupants (340 pounds) and mark Point 3.
..i
From Point 3 plot the proper distance (use correct scale of Visual Plotter for each) which
represent addition of baggage and fmally fuel. (Points 4, 5 and 6.)
When the final step of adding fuel is plotted, the point falls within the envelope at 3600 pounds.
and 89.8 inches aft of datum. (The fuel graduations on the plotter run from 0 to 54 gallons. 0 to
30 gallons. The inboard tanks will always contain 6 gallons of unusable fuel, and these three
figures total to the listed tank capacity of 90 gallons.)
Fuel of 30 gallons is included for the optional tip tanks on the visual plotter.
ISSUED: November 28,1969
REISSUED: June 1,197O
REVISED: March 30,1973
REPORT: 1605 PART II PAGE 3
MODEL: PA-39
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