Weight and
Balance Calculation for the Sonerai Aircraft.
1.
Drain all oil and
fuel. Remove all items that are not part
of the aircraft. Undrainable fuel and
oil are normally part of empty weight, therefore a dry engine sump, oil cooler,
or fuel tank should be filled and then drained using normal maintenance
procedures.
2.
Positioned the
aircraft on three scales.
3.
Level the
aircraft by adding shims under the
scales. Tail wheel aircraft will require
a stool to raise the scale for the tail wheel.
Place the level on the upper fuselage longeron.
4.
Using a plumb-bob
and a piece of chalk, transfer engine centerline and tail centerline locations
to the floor.
5.
Use a carpenter's
chalk line to connect the engine and tail points creating an AXIAL CENTER LINE
on the floor.
6.
Transfer the
right and left wing leading edges to the floor using the plumb-bob and chalk.
7.
Snap a chalk line
through the leading edge points on the floor and label it DATUM. Write the word
POSITIVE on the axial center line between DATUM and the tail of the
aircraft. Write the word NEGATIVE on the
axial centerline between DATUM and the engine.
8.
Transfer the main
gear axle locations to the floor.
9.
Snap a chalk line
through the axle points and label it MAINS.
If you have a tail wheel Sonerai, the MAINS line will be forward of the
leading edge by about one inch. If you
have a nose wheel Sonerai, the MAINS will be aft of the DATUM by about 19
inches.
10.
Measure the
distance between the intersections of the DATUM line and the MAINS line. This is dimension AM, (arm main).
11.
If the MAINS line
is aft (toward the tail) of the DATUM line, AM is positive. If the MAINS line
is forward of the datum line AM is negative.
Record AM on the work sheet.
12.
Transfer the tail
wheel or nose wheel axle point to the AXIAL CENTER LINE on the floor using a
plumb-bob.
13.
Measure the
distance from the DATUM to the tail or nose wheel position as applicable. This is dimension AX, (arm, tail or nose
X). AX will always be positive for a
conventional gear aircraft and AX will always be negative for a tricycle gear
aircraft.
14.
Perform the
calculations in the examples to assure you arrive at the same empty weight CG
(rounded) before calculating your own numbers.
EXAMPLES
CONVENTIONAL
GEAR
AM =
ARM
WM =
WEIGHT
AX =
TAIL ARM = 168
WX =
WEIGHT TAIL = 30
CGE
= 8.15
TRICYCLE
GEAR
AM =
ARM
WM =
WEIGHT
AX =
ARM NOSE = -32
WX =
WEIGHT NOSE = 137
CGE
= 7.62
15.
Record weights of
the two main scales. Add together and
record as WM, (weight mains).
16.
Record weight on
tail or nose wheel scale. Record as WX,
(weight nose or tail).
17.
Double check that
all arms forward of the leading edge are recorded as negative and all arms aft
of the leading edge are recorded as positive.
Remember that when a positive number is multiplied by a negative number
the resulting product is negative.
18.
Multiply AM by WM
and record moments as MM, (moments mains).
19.
Multiply AX by WX
and record moments as MX, (moments nose or tail).
20.
Add WM and WX to
get WE, (weight empty).
21.
Add MM and MX to
get ME, (moments empty). Remember to
subtract if moments are negative.
22.
Divide ME by WE to get CGE, (empty center of gravity).
SONERAI W&B
WORKSHEET N#______ DATE ______
total moments (MT)
empty center of gravity (CGE) = --------------------------
total weight (WT)
arm main (AM) ___________
weight main (WM) ___________
moments main (MM = AM x WM) ___________
arm tail or nose (AX) ___________
weight tail or nose (WX) ___________
moments tail or nose (MX = AX x WX) ___________
total weight (WT = WM + WX) ___________
total moments (MT = MM + MX) ___________
empty center of gravity (CGE = MT / WT) ___________