Jeff,
I think that the TP5 and TP6 can be removed with heat without cutting any
holes. Also, it would be easier to pre-drill the pip-pin holes, as you can
then do a trial fit before bonding. To get the position exactly right I
would attach a template (using double-sided tape) with a 1/4 inch hole over
the top of the recess, first lining up all 3 holes with a 1/4 inch shaft or
bolt, before removing the TP6. Just one of my crazy ideas.
Karl
>From: Rman <topglock@cox.net>
>Reply-To: europa-list@matronics.com
>To: europa-list@matronics.com
>Subject: Re: Europa-List: Europa Tailplane - Mod 73
>Date: Sun, 15 Jul 2007 13:25:12 -0500
>
>
>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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