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1. 09:35 AM - Re: Lighter tailwheel (D McFadyean)
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| Subject: | Re: Lighter tailwheel |
I'm exploring options for losing some weight from behind the CG, because my payload
is limited by balance rather than all-up weight. A few pounds at the tail
should do it.
Has anyone fitted a light(er) tailwheel, and what make was it/how did it perform?
There's a standard mod for RVs that achieves the same, but I'm hoping for cheaper
options.
Any leads?
Duncan McF
> On 05 October 2020 at 11:40 JohnFrance <77alembert@gmail.com> wrote:
>
>
>
> Hi Erik, I am following the evolution of the play in my tailplane and this is
what I have observed.
> In my case the play is between TP5 and TP4 almost certainly due to play in the
clevis pin on the starboard side.
> You can check this by marking the junction between TP5/TP4 with a marker pen.
> The edge of TP5 is just visible in your photo exiting the nylon bush TP10. The
movement will be very small but should be visible. Check both sides and the
same thing for the junction TP4/TP9.
>
> The good news is there are several modifications available to fix this, one being
to use Loctite between TP4/5/9 and various clamping methods are available
too which are fine.
> As Pete pointed out however, the bolts in yours (appear to) clamp directly on
the Nylon TP10 and that is not good.
>
> If Loctite has already been used but failed to hold on one of the components
you will have to find a way to dis-bond the others to remove TP4 from the aircraft
to carry out the mod!
> I have a theory on that but not yet put it into practice! If anyone has done
that please share your experience?
>
> Here is a text written by the late Nigel Graham on the subject.
>
> Firstly, please find attached, the details of the tailplane clamp arrangement
I developed (and you requested) ...... it could be relevant to your problem.
I have also attached another mod that I developed to prevent the possibility of
a dis-bonded TP5 or TP6 bush (these are built into the tailpanes refer to the
online manual for details)
>
> . and on that note
>
> There are two possible reasons for slop in the tailplanes, one is benign and
relatively easy to fix and the other is a lot more serious and could kill you
if not addressed immediately.
>
> First, an overview of the pitch drive train; the pitch pushrod transfers pitch
linear motion into the TP9 arm, this rotates the TP4 (torque tube) via the TP14C
pins.
>
> The rotating shaft transmits the motion back out to the TP12 drive plates via
the TP14D pins and hence to the tailplanes.
>
> The first thing to check is the cumulative play in the TP14 drive pins.
>
> This is a well-documented issue and was addressed by the factory by increasing
the diameter of the pins. This was not a good engineering solution as it only
delayed the eventual re-occurrence of the problem.
>
> Pat Tunneys clamp block mode (that you commented on), my clamp mod (attached)
and squirting Locktite into the gap were all far better solutions designed to
solve the problem of relative movement.
>
> You can test if this is your problem by sliding the tailplanes off the torque
tube and placing two long lever bars (gently) against each drive plate (TP12)
pin and the torque tube and trying to rotate port and starboard in opposite directions.
There should be NO movement. If there is, this is your problem. This
is non-critical and can be solved by any of the above mentioned solutions.
>
> If you detect no movement here, then the problem lies in the tailplanes and
this IS serious and the A/C should be grounded immediately until repairs are made.
>
> The problem lies in the way the tailplanes were built. The build instructions
called for the two supporting stainless steel bushes to be bonded into the soft
blue foam of the TP cores. If you read the attached mod document 070625 Tail-plane
drive pin mod there is a fuller description of the problem and solution.
>
> Very little supports these bushes laterally, and if they should become dis-bonded,
the tailplane can slide laterally until, in extreme cases, it disengages
from the two drive pins on the TP12 plate. At this point one tailplane will rotate/flutter
with ferocious force and the back of the fuselage will most likely
break away the aircraft will break up in flight.
>
> This happened to G-HOFC in 2007, I passed my information on to the LAA and who
subsequently issued mandatory Mod 73 (attached).
>
> --------
> Europa mono Nr 192
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=498675#498675
>
>
>
>
> Attachments:
>
> http://forums.matronics.com//files/tail_plane_drive_pin_mod_196.pdf
>
>
>
>
>
>
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