So how do you drill the new pip pin holes though the outside new tube to
line up with the existing holes in TP4?
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com] On Behalf Of Rman
Sent: 15 July 2007 19:25
Subject: Re: Europa-List: Europa Tailplane - Mod 73
All,
I've read, with great interest, all the suggestions and discussion. I'm
no engineer, but I have a pretty good idea of what I would do, should I
find any evidence of disbonding of the tailplane bushings. And, I
believe it could be done with very little cosmetic damage to the
tailplane. I like the solid tube idea and would build off of that.
Basically, a tube, of the appropriate length, with two 1/4", round,
metal rods welded fore and aft, on centerline. The rods wouldn't have
to run the full length of the tube, but it certainly wouldn't hurt. The
purpose of the rods would be to further stabilize the tube and prevent
it from twisting.
Should the original bushings become disbonded, it should be a fairly
simple task to remove the old bushing (even if it required opening the
wingtip), remove the inner bushing and modify the foam and ribs, to
accomodate the new shape of the tube. Inserting the new tube would be
as simple as applying a thin coat of Redux to the tube and inner walls
of the foam, plugging the outboard end of the new tube and pushing the
assembly in. The new tube would then be drilled to accept the standard
pip pins. Adding covers to the pip pin access holes would further
remove the possibility of a pin becoming dislodged.
Seems to me that the new assembly would be extremely strong and should
remove any further chance of the tailplanes pulling away from the drive
pins.
So, am I way off base, of does this idea hold water?
Jeff - Baby Blue
300 hours and finishing up her 2nd annual...
Karl Heindl wrote:
>
>
> Nigel,
>
> I understand all that and your mod should have been made standard a
> long time ago. But what about older Europas ? We hear reports about
> disbonded TP6s but we don't hear how they were repaired. I really
> would like to know. A suitable retrofit mod should also have been made
> available as soon as this problem was known.
> I still say that there is no way the tailplane can move if the pip pin
> head is firmly against solid material on the inboard side. You say
> there is always a gap, but that gap is filled with floxed epoxy, and
> the head is inside a close fitting plastic pipe in my case. I think
> another builder recently told us about a similar mod he made. The
> remaining space around the pipe is also filled with epoxy. Of course
> all these solutions are based on theory and only a lab test could
> verify the claims.
> When my TP5s disbonded from trailering I was kicking myself for not
> having installed a one-piece pipe, but in those early days I was very
> careful to follow the build instructions precisely. I stll think that
> a retrofit of a one-piece sleeve would be more than strong enough to
> prevent any future disbonding, and would be a relatively easy solution
> where the TP6s have already disbonded.
>
> As far as the accident goes, we still don't have any real conclusive
> evidence about the sequence of events. Only a number of theories. Only
> a wind tunnel test would verify the flutter theory, but who is going
> to pay for that ? Eyewitness reports can be very misleading.
> If the wing trailing edge pin came off first, is it possible that the
> pilot was getting set up for landing and deploying flaps and
> undercarriage ?
>
> I also like the other suggested solutions where a lock is put behind
> the TP12
>
>
> Karl
>
>
>>
>>
>>
>> Karl,
>>
>> I have attached below, an excerpt of a long mail I sent to the PFA that
>> describes a sequence of events that could lead to the tailplain moving
>> outboard. Out of interest, there is always a gap between the pip-pin
>> and the
>> face of the rib.
>>
>> This was sent before the current Mod 73 was issued, but you will see
>> why the
>> temporary remedial action has been to reinforce the pip-pin hole.
>>
>> Nigel
>>
>>
>>
>>
>> -------------------------------
>> Excerpt
>>
>> ...... The only thing preventing each tailplane moving sideways is a
>> single
>> pip-pin that passes through the TP6 bush and into the TP4 torque
>> tube. (See
>> Fig.5 Chap 4)
>> The design relies on a good bond to hold TP6 in place, however only the
>> protruding outer 12mm (just 8mm on TP5) is required to bond to the
>> tailplane
>> rib that will subsequently be laid-up onto it. Epoxy adhesive does
>> not bond
>> well to stainless steel - so the potential for this bondline to fail is
>> great.
>> This tiny bondline is the only "design" load path to prevent the
>> tailplane
>> moving laterally. If the bond failed, the loose TP6 bush would tend
>> to push
>> its way inboard into the soft blue foam, allowing the tailplane to move
>> outboard. The TP5 bush would offer no resistance since it would
>> simply slide
>> along the TP4 torque tube.
>>
>> In some early Europas, this TP6 bush has de-bonded and it is only the
>> laminations into the "PipPin" access hole that prevent any lateral
>> movement
>> of the tail-plane. This lamination was never intended to be
>> structural. If
>> the aircraft is high-time and habitually operated off rough strips,
>> it is
>> logical to predict that the continual fretting would cause the glass
>> around
>> the pip-pin hole to chafe, opening up the hole to a point where the
>> whole
>> tailplane could slide far enough laterally to allow the tail-pane
>> drive pins
>> (TP12) to disengage from their drive bushes (TP13) - The tailplane would
>> then oscillate violently with catastrophic results.
>>
>> Modification 10672) calls for both the Stainless TP5 and TP6 bushes
>> to be
>> laminated into an epoxy/Bi-Directional Glass tube before inserting
>> this into
>> the tailplane TP2 cores and laminating the ribs. This bonds both
>> bushes over
>> their entire surface area, significantly increasing the bond area and
>> more
>> importantly, physically tying TP5 with TP6 and both the inner and
>> outer ribs
>> together. With this structure, the entire bond surface area and both
>> ribs
>> would have to fail before the tailplane could move sideways.
>>
>> The loadpath is through the mod 10672 and not through the outer skin and
>> pip-pin hole - a significantly better engineering solution.
>>
>>
>> -
>>
>>
>>
>>
>>
>
> _________________________________________________________________
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>
>
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