Jabiru J450 Constructors Manual
Testing>Weight and balance
Tuesday, April 6, 2010
301 of 343
Weigh the aircraft
The weighing part of this procedure should be conducted in a closed hangar with a level floor.
Because the aircraft is very light any wind will adversely affect the weights, so a closed
building, without any doors being opened during the procedure, is required.
Place a set of scales under each wheel and level the aircraft: use a builders level across the
lower door sills to check for lateral level, and along each lower door sill to check for
longitudinal level. Pack under wheels as required to level the aircraft.
Record the weight of each wheel under the “Weight” column in the chart below.
Note: if you have access to only 1 set of scales you may weigh each wheel individually,
however you will need to pack under the other wheels to level the aircraft before each weight
is recorded.
Calculate the Empty Weight and Centre of Gravity
Sum all of the items in the
Weight
column and put the total at the bottom of the column.
All distances aft of the
Datum
are considered positive and all distances forward of the
Datum
are considered negative in the calculation that we are about to do in this step.
Calculate the
Moment
of each wheel: starting with the nose wheel, multiply the
Weight
by the
Distance to Datum
and record the result in the
Moment
column. Note that the
Distance to
Datum
value for the nose wheel will be a negative value and the result will also be negative.
Multiply the
Weight
by the
Distance to Datum
and record the result in the
Moment
column for
each main wheel. These results will both be positive values.
Sum all of the items in the
Moment
column and put the total at the bottom of the column.
Divide the total
Moment
by the total
Weight
and record the result in the red box at the bottom
of the chart – this is the distance aft of the leading edge where the empty aircraft will balance
and is referred to as the
Empty Aircraft Arm
.
Item
Weight
(kg)
Distance to Datum
(mm)
Moment
(kg/mm)
Nose wheel
(A+B)/2 -
-
Left main wheel
(C) +
+
Right main wheel
(D) +
+
Column totals:
Moment / Weight
Empty Aircraft Arm:
mm aft of
Datum
Calculate the Empty Weight Trim Index
Multiply the
Empty Aircraft Weight
by the
Empty Aircraft Arm
and divide the result by 1000
to arrive at the
Empty Weight Trim Index
.
This value can be used in the
Load and Balance Worksheets
in Section 6 of the Owners
Manual.
X
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