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XL
Step 8 - Calculating the various ARMs
It will be necessary for you to calculate the ARM for each of
the following:
• “Pilot/co-pilot” ARM
• “Rear passenger” ARM
• “Header sump tank fuel” ARM
• “Fuel” ARM
• “Baggage” ARM
Here is an example using the factory Velocity N81VA to calcu-
late the “Pilot/co-pilot” ARM:
Nosewheel Axle ARM = 31”
Nosewheel weight = 146 lbs
Main gear axle ARM = 144.6
Main wheels (L+R) combined weight = 1600 lbs
Pilot Weight = 185 lbs
• First, find the CG of the aircraft with pilot:
(146 x 31) + (1678 x 144.6) 24716664.8 Inch lbs
_______________________ = ________________
= 135.5”
1640 + 1825 1825 lbs
• Second, subtract the moment of the empty aircraft (247164.8
inch lbs) from the moment of the aircraft when loaded with the
pilot (232280 inch lbs)
247164.8 - 232280 = 14884.8 inch lbs
• Third, verify that the weight difference between the aircraft
with pilot (1825 lbs) and the weight of the empty aircraft (1640
lbs) equals the pilots weight (185 lbs).
• Fourth, divide the difference of the moments by the difference
of the weights (the pilot weight), and the result will be the
“Pilot/co-pilot” ARM:
14884.8 inch lbs
_______________ = 80.45” aft of datum
185 lbs
Repeat this procedure for all the various ARMs and
record the results below:
• “Pilot/co-pilot” ARM =
• “Rear passenger” ARM =
• “Header sump tank fuel” ARM =
• “Fuel” ARM =
• “Baggage” ARM =
• “Ballast/Nose” ARM =
Note: For the fuel ARM, add the two Fuel ARMs (15 gal + Full),
divide by 2 to get an average Fuel ARM
Here are some sample ARMs for N97XL:
• “Pilot/co-pilot” ARM =80.0
• “Rear passenger” ARM =124
• “Header sump tank fuel” ARM =145
• “Average Fuel” ARM = 132
• “Wing Strake Storage” ARM = 115
• “Ballast in nose” ARM = 24”
Step 9 - Calculating the CG now that you known the
ARMs for your aircraft:
Ok, now we have all the data we need to set up a weight &
balance worksheet. You can set up a worksheet using a computer
with spreadsheet software (eg. Excel, Lotus, etc.) or simply make
photocopies of the worksheet (OM-WB) and do it longhand.
Refer to the “sample only” weight & balance spreadsheet for a
“standard” Velocity.
It is pretty much self explanatory after all that you have been
through to get this far, but to be safe, let’s run through it. First, if
Summary of Contents for XL RG
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