Jabiru J450 Constructors Manual
Pre-Paint>Fuselage>Firewall forward>Fit engine mount and engine
Tuesday, April 6, 2010
64 of 343
Set the engine angle of incidence
In this step the engine will be adjusted until a level or digital protractor (pictured below)
placed on the top of the crankcase reads completely level fore and aft, which indicates an
angle of incidence of 0° (zero degrees).
In our factory we usually find that the angle of incidence is correct with the standard mount,
however the following procedure should still be followed.
Recheck that the aircraft is completely level and then measure the angle of incidence and use
a hydraulic jack under the crankcase to lift the front of the engine to a point where the engine
has a very slight (0.5° if using a digital protractor) nose-up attitude then drill the bottom
engine mount holes through the firewall and fit the AN4-20A bolts, backing plates, washers
and Nyloc nuts. Now release the jack and recheck the angle of incidence. If the engine is
slightly down at the front you can fit up to a maximum of 3 penny washers under each bottom
engine mount to adjust the angle of incidence. Bear in mind that a small adjustment at the
firewall will result in a large change at the propeller flange.
Check the lateral angle of the engine while the aircraft is completely level: it should be very
close to level.
Once you‟re happy with the alignment you can permanently install the lower engine mount
bolts, taking care to remember the backing plate (pictured on the first page of this task), and
tightening the Nyloc nuts enough to hold firmly but without crushing the plywood firewall.
If penny washer spacers were used on the lower engine mounts then equivalent thickness
spacers will need to be used behind the bottom bar on the mount. Drill these mounting holes
at 3/16”
,
fit the appropriate spacers if required, and finally fit 2 x AN3 bolts through the
bottom bar and the firewall and fit washers and Nyloc nuts.
This completes the
Pre-Paint>Fuselage>Firewall forward>Fit engine mount and engine
task.