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Re: Engine Thrustline

Subject: Re: Engine Thrustline
From: Tom & Cathy Friedland <tfriedland@home.com>
Date: Fri, 16 Mar 2001 08:51:01
Thanks Fred

As usual, you reply quickly with the cogent info.  My motor mount has about a
0.4 degree port offset so I will need to shim the port motor mounts.  The
vertical mounts are pretty square.

Thanks again.

Tom

Fred Fillinger wrote:

> Hi, Tom --
>
> > I have a fwf kit for a Jabiru 3300 for the XS and thus far I have little
> > installation info.  Does the Rotax kit 4 discuss the engine thrust
> > line?  Many aircraft call for a 2 to 3 degree thrust line offset to
> > starboard to compensate for P factor.  What is called for with the Rotax
> > engines?
>
> 914 manual says 1.5 deg. to starboard.  Determined by a straightedge
> on prop flange, with tick marks 20" on either side of centerline
> (total 40").  Distance from marks to firewall should differ by
> 1-1/16".
>
> >  Is there any vertical line offset?
>
> They don't say, but mine came out about zero.  It depends upon
> relationship of your thrust centerline with the vertical position of
> the aircraft's CG, probably still (desirably) above the latter for the
> 3300, unlike a high-wing Cessna where engine's gotta point down.  I'd
> guess as long it's zero or down a hair, you'll not notice anything in
> flight testing (you don't want immediate pitch up on rapid power
> application - horiz tail alone causes a bit of that).  Looks about
> zero on Bob Harrison's, eh Bob?
>
> Enjoy that 3300.
>
> Regards,
> Fred F., A063



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