MEASURING
(Reference Airplane Weighing Form)
1. Obtain measurement “A” by measuring horizontally along the airplane
centerline, from the mid point of a line stretched between the centers
of the main wheels to a plumb bob lowered from the forward side of the
rewall (FS 0.00). This measurement is dimension “A” and is normally
approximately 94 inches.
2. Obtain measurement “B” by measuring horizontally and parallel to the
airplane centerline from the center of the nose wheel axle, on the left side,
to the line stretched between the centers of the main wheels. Repeat
this process on the right side of the nose wheel axel and average the two
measurements. Subtract this averaged measurement from dimension
“A” to obtain the nose wheel weighing point arm. This will be a negative
number since the nose wheel is forward of the rewall datum point.
3. Determine and record the moment for the main and nose gear weighing
points, using the following formula:
Moment = Net Weight x Arm
4. Calculate and record the as-weighed weight and moment by totaling the
appropriate columns.
5. Determine and record the as-weighed Center or Gravity in inches aft of
datum, using the following formula:
C.G. = Total Moment ÷ Total Weight
6. To determine the Empty Weight C.G., add or subtract any items not
included in the as-weighed condition to determine the empty condition.
Application of the above C.G. formula with empty weight and moment
values will determine the Empty Weight C.G.
7. If the airplane was weighed with the oil drained, add the (negative number)
correction for engine oil. Add the correction for undrainable fuel (1.0 lb at
FS 83.4) to determine the Basic Empty Weight and Moment. Calculate and
record the Basic Empty Weight C.G. by applying the above C.G. formula.
8. Record the new weight and C.G. values on the Weight and Balance
Record.
9. The above procedure determines the airplane Basic Empty Weight,
Moment and Center of Gravity, expressed in inches aft of datum. The
Center of Gravity location can also be expressed as a percentage of the
airplane’s Mean Aerodynamic Cord (MAC), using the following formula:
C.G. (%MAC) = 100 x (C.G. Inches – LEMAC) ÷ MAC
• LEMAC = 54.8073
• MAC = 64.919
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