Jabiru J450 Constructors Manual
Testing>Weight and balance
Tuesday, April 6, 2010
299 of 343
Testing>Weight and balance
Objectives of this task:
To calculate the
Empty Weight
and the balance point or
Centre of Gravity
of the aircraft.
The
Empty Weight Trim Index
is calculated from these values and then various loading
scenarios are be tested to see if any rebalancing of the aircraft is required. Finally all values
are entered into the
Aircraft Empty Weight Record
in Section 6.2 of the Owners Manual.
Equipment required:
3 bathroom scales capable of weighing up to 150Kg
Plumb bob and string line, set square
Builders type spirit level
Chalk and a builders chalk line to mark the reference positions onto the hangar floor
Prepare the equipment
Before you do anything else, check your scales for accuracy: use some objects of a known
weight, such as a few 20Kg bags of cement to see if your scales are reading correctly at
around the 100Kg range of the scale.
If there is a problem then either adjust the scale or, if this is not possible, note how much the
scale over/under reads and apply this as a correction to the weight displayed.
Prepare the aircraft
Remove all surplus items from the cockpit: tools, clothing, etc. and clean the interior of the
aircraft with a vacuum cleaner. Clean the exterior of the aircraft: remove all dust and dirt with
a damp cloth. Check that the engine oil is full to the bottom of the hatched marking on the
dipstick. Turn the fuel tap on the console to the OFF position (lever facing up).
Fill the header tank with fuel but leave zero fuel remaining in the wing tanks.
The aircraft should contain everything required for flight except fuel in the wing tanks.
Reference points
In this task you will be measuring the horizontal distances from the
Datum
, which is the
leading edge of the wing, to the main wheel axles and the front wheel axle.
Each reference point will be marked onto the hangar floor and then measured.
Mark and measure
Refer to the drawing on the next page for colour-coded details of the line markings.
Use a chalk line to mark 2 lines at least as long as the aircraft on the hangar floor in a right
angle cross. Roll the aircraft directly along one line (coloured
blue
in the drawing) until the
main wheels are directly over the second line (coloured
green
in the drawing).
The main wheel axles must be
directly
over the second (
green
) line: use a square or a plumb
line from the axle bolt centres in the main wheel spats to check this and move the aircraft as
required. Leave the brakes off and chock the main wheels when the position is correct.
Mark the
Datum
line (coloured
purple
in the drawing) on the floor by means of a plumb line
hung from the leading edge of each wing, using a point about 300mm outboard of each main
wheel. Join both
Datum
line marks and mark a line across the floor with your chalk line.