Aircraft Technical Manual
J120, J160, J170, J200/J400, J230/J430, J250/J450 Variants
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Figure 13 – Torque Wrench & Crowsfoot Adaptor Setting 2
A good torque wrench is an essential tool for maintaining Jabiru Aircraft. It’s important to realise
however that even the best wrench needs calibrating occasionally. This can be done using a dead
weight on the end of a known arm or – preferably – sending the wrench away to be calibrated. Note
that Civil Aviation Authorities generally require that the tool be calibrated in a way which is traceable
to a NATA-standard laboratory.
A “Crowsfoot” extension as shown in Figure 10 is sometimes necessary – it allows high torque
settings to be used on small nuts without damaging them and access to difficult locations. However,
when using the extension as shown in Figure 12 the extra length will throw off the torque setting of
the wrench. This must be corrected using the following formula:
.
L1 is the distance from the middle of the grip of the handle to the centre of the wrench drive lug
L2 is the distance in the direction of the handle from the centre of the wrench drive lug to the centre
of the nut socket of the adaptor.
For example: a nut needs to be tensioned to 30lb.ft. The torque wrench is 12” long and the
crowsfoot extension is 2” long. The extension is oriented as shown in Figure 12. This means that the
torque wrench must be set to:
If the extension is oriented at 90° to the wrench as shown in Figure 13 then no correction is needed
because L2 is zero.
Figure 14 – Using A Crowsfoot Adaptor
Corrected Torque Setting Required
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