Jabiru J450 Constructors Manual
Testing>Calibrate fuel gauges
Tuesday, April 6, 2010
306 of 343
Testing>Calibrate fuel gauges
Objectives of this task:
To calibrate the fuel gauges so that they show the amount of fuel remaining correctly and to
mark a fuel dipstick at the same time.
In this task you will be working with flammable fuel and you should take precautions such as
having a suitable fuel extinguisher close to hand and no naked lights of any kind nearby.
In the task
Post-Paint>Wings>Prepare wings for fitting
you set the empty indication of the
fuel gauges, now you must check the other indications: ¼, ½, ¾ and full.
To do this you must have the following:
A fuel supply of at least 135 litres of clean aviation fuel (AVGAS)
An accurate means of measuring the fuel as it is dispensed
Clean, sealable fuel container(s) capable of holding around 135 litres
2 metres of fuel grade tubing and a 1 litre container
A length of clean wood or aluminium about 300mm long to use as a fuel dipstick
Some aircraft refuellers may allow you to use a part of their ramp area for this test provided
that you purchase your fuel from them. The calibration process should take less than an hour.
Level the aircraft
Park the aircraft on the level surface and chock the main wheels.
Use a spirit level to check the aircraft for level: laterally level across the bottom of door sills;
longitudinally level along the door sills. Pack under the wheels if and as required to level the
aircraft. If the surface is exactly level you can measure the distance from each wingtip to the
ground as a final check of lateral level, but the spirit level is the best reference.
The rest of this task depends on the aircraft remaining level throughout, so chock it carefully.
Find the zero fuel level
Remove the upper engine cowling.
Disconnect the fuel line in the engine bay at the firewall fitting and run a length of fuel line
from the firewall fitting, down and out of the lower cowling and into a clean fuel container.
Turn the fuel tap on the console to the ON position, with the lever facing forwards.
Remove both fuel caps and pour a small amount of fuel into each wing tank. Allow the fuel
levels to settle until some fuel runs out into the container. When the fuel no longer runs out of
the line the header tank will be full and the wing tanks empty: this is your zero fuel level.
Lock off the fuel lines
Now that you are at the zero fuel level the fuel lines from each wing tank must be locked off
be clamping both the front and back fuel pickup lines. Remove the lock wire around the fuel
sheathing at the rear of the wing root to expose the fuel lines as they enter the cabin.
Clamping of the fuel lines must be done carefully so as not to stress the fuel line, so use a
rounded surface with no sharp edges to bear against the fuel lines and apply just enough
clamp pressure to close the line, no more. Medium size spring clamps will excerpt enough
pressure to clamp the lines shut.