<<I discussed this movement with Andy and he said that the weight moves even
with the cables.>>
That's the sort of comment that worries me. Because in that situation the
lateral stresses at the attachment point of the counterbalance arm
completely different (i.e. compressive and not bending, and not constantly
reversing). I accept that there is a small bending component, but as the
counterbalance weight is forward of the cable attachment points, much of the
bending is cancelled out.
Not so much commercial pressure I smell, as engineering arrogance.
Its also TP09 that I fear for and the constantly reversing loads being fed
into an area that is probably hardened from the heat haze of the weld. No
doubt these issues have been considered and be very happy to see the
calculations.
Duncan McF.
----- Original Message -----
From: "MICHAEL PARKIN" <mikenjulie.parkin@btopenworld.com>
Subject: Re: Europa-List: Mod 70
<mikenjulie.parkin@btopenworld.com>
>
> Jeremy,
>
> I have been away on business and so have not been around to join the
> discussion about MOD 70 but I have to say I am very unhappy about the Mod
> and its possible implications. I appreciate that being a non current
> engineer makes my opinion of little value to Europa 2004 or Francis
> Donaldson, but that never stopped me before.
>
> Firstly, the installation of the cables on the Mass Balance arm during the
> build struck me as very much hit or miss procedure at best. Page 20-2 of
the
> builders manual- quote- " Make the cable as tight as possible before
swaging
> the sleeve. This operation is almost certainly a two person job, holding
the
> cable and swaging tool at the same time." When I came to that, it seemed
to
> me that obtaining a reasonable cable tension and getting the the mass
> balance arm normal to the tailplane torque tube was almost mutually
> exclusive. It was for that reason that I installed a turnbuckle in each
> cable - this enabled precise measurement of the mass balance arm and
> allowed for a predictable tension to be set. I don't know how many
builders
> adopted the same approach, but I know I am not alone with this idea.
>
> The requirement for a stronger mass balance arm was decided following the
> failure of one classic that had suffered ' a number of landing incidents'.
> OK, I can accept that without a problem.
>
> Last monday I drove up to Kirbymoorside to speak to Andy about the Mod and
> my misgivings about it. Andy has done a lot of testing on the setup and
he
> showed me the new balance arm. It is made of thicker wall tubing and has
a
> considerably more substantial adjuster assembly replacing the original
TP18A
> adjuster. Andy also conducted some load tests on the original arm (in the
> vertical plane) he found that the test arm initialy twisted and then the
> lower tube buckled - he showed me the failed item. I am not sure whether
> the arm was installed in the aircraft, with cables attached, or whether it
> was just a straightforward bench test - if it was a bench test I doubt
> whether any cables were installed - perhaps if cables had been attached
the
> inital twist prior to failure might have been delayed. However, the new
arm
> is much stronger and should do the job nicely - but there are no cable
> attachment lugs.
>
> I asked Andy why he had discarded the cables? His reason was purely to
make
> the installation easier for owners. I explained my turnbuckle
arrangement.
> to which he replied that it was not a problem and Europa could easily put
> the cable attachment lugs on the new arm. Remember that the identified
> weakness is in the vertical plane of the mass balance arm not in the cable
> system. I asked if he would contact Francis Donaldson, but he said that
he
> would be happy for me to do it - as the new arm would be fitted with the
> existing, proven engineering - it should require no flight testing. As it
> happens my aircraft is in the workshop for its' permit renewal so I
removed
> the D panel and the fuselage access panels and had a good look around.
The
> fitting of the turnbuckles to install the new balance arm would actually
be
> quite easy. After carefully measuring and marking the cables so that the
> end of the turnbuckle can be fitted in the correct place, the cables can
be
> cut as far forward as possible, that is just short of the cable lugs. Now
> if the fuselage access panel, on the right side by the tail is in the
> standard position, the cut end of the cables can be brought outside the
> fuselage and the turnbuckle end swaged in comfort. The other end of the
> turnbuckle can be fitted to the attachment lug on the arm using a standard
> fork fitting, cotter pin and split pin. The new arm is then installed
onto
> the torque tube and with minimal time in the rear fuselage, the barrels of
> the turnbuckle are fitted, the arm is adjusted to the centre of the
pushrod
> containment assembly, the tension set on the cables and finally locking
> wires fitted to the turnbuckles. It may be necessary to drill a little
out
> of the mass balance weights to reset the balance.
> Now the point is that if some europas, because arranging the mass balance
> arm normal to the torque shaft is not a given, and the containment
assemble
> was built around the already installed mass balance arm. It is quite
likely
> that the resting place of the new uncabled arm is not going to be in the
> same place. This means that the pitch tube containment attachment
brackets
> will have to be moved, and quite likely the fit of the ply around the
pitch
> tube itself may need adjusting. How much time will be required down the
> black hole to do that!!! Using the existing cables would avoid all those
> problems. I asked Andy why he hadn't considered using turnbuckles, his
> comment - - "Well people might not have any turnbuckles."
>
> What worries me is that this big lump of steel is going to be free to move
> left and right at will, perhaps hundreds of times in an hour in opposition
> to the slightest yaw of the aircraft. How much could it move? I noted
that
> a value of 4mm was mentioned on this forum. In fact, Para 5 of step 3 of
> the modification leaflet states - "The diameter of the mass balance
weights
> is 50mm, and the nominal clearance is 2mm each side - check that the
> clearance achieved is between 1mm and 4mm each side". I interpret that to
> mean that the lateral movement of the arm could be 8 mm. Such a movement
> does not take into account the flexing of the plywood of the pitch
> containment assembly - not the sturdiest of structures. In real terms
this
> new arrangement could have these not insignificant balance weights
> 'clonking' left and right by maybe 12mm. Is this movement likely to cause
> any fatigue problems at the attachment points on the torque shaft -
perhaps
> one of the forum metallurgists could advise.
>
> I discussed this movement with Andy and he said that the weight moves even
> with the cables. If they are fitted in the manner described in the build
> manual I can see that there might be some movement. With properly
tensioned
> cables, there is negligible movement.
>
> Actually, it is not outside the realms of possibility that a fracture of
> the original TP18A could be accellerated because of lateral movement
caused
> by slack cables.
>
> The bottom line is that, the history of why the cables were originally
> fitted to the mass balance arm is irrelevant. Many Europas have done may
> thousands of hours flying with he current mass balance arm configuration
> without a problem. Now following the fracture of one TP18A on an aircraft
> that has suffered 1 or more landing incidents we are all to fit stronger
> mass balance arms. Changing the arm is the right thing to do. But I
> totally disagree that discarding the cables is the right thing to do. It
is
> one aircraft modified and tested at the factory for a few hours against
the
> experience of the whole fleet.
>
> I understand from Bob Harrison that since I spoke to Andy Draper he has
been
> told by his boss that he cannot put the lugs on the new arms as he
promised
> me. It seems that the only way we can incorporate this modified component
> is the way Europa 2004 say, because that is what they have worked out and
> tested. I smell commercial pressure here.
>
> I fear we are in danger of throwing the baby out with the bath water!!!!
>
> I have sent this email to the forum in the hope that someone can allay my
> fears about MOD 70 - perhaps it might generate some positive comment.
>
>
> regards,
>
> Mike Parkin (G-JULZ - hiding in the corner of the workshop with cables a
> quivering.)
>
>
> ----- Original Message -----
> From: "Jeremy Davey" <EuropaFlyer_3@msn.com>
> To: <europa-list@matronics.com>
> Subject: RE: Europa-List: Mod 70
>
>
<EuropaFlyer_3@msn.com>
> >
> > Fred,
> >
> > It wasn't stripped threads - the threaded portion sheared in two.
> >
> > Tim,
> >
> > I offered and you declined. OK, I'm 6' and 220lbs, but I still contend
> > you're being fussy! :-)
> >
> > Cheers,
> > Jeremy
> >
> > Jeremy Davey
> > Europa Monowheel 537M G-EZZA
> > Europa Club Vice-Chairman, Webmaster, PFA NC Representative
> > PFA EC Member
> > If you can keep your head when all about you are losing theirs, then it
is
> > possible you haven't grasped the severity of the situation.
> > Tail done
> > Standard XS wings with mods underway
> > CM installed in fuse (with airbrakes fittings)
> > 1390 build hours to date
> > Intended fit:
> > Rotax 914 turbo, Airmaster CS fully-feathering prop
> > Lots of lights, buttons, switches, gizmos, and alarms
> >
> >
> > -----Original Message-----
> > From: owner-europa-list-server@matronics.com
> > [mailto:owner-europa-list-server@matronics.com] On Behalf Of Fred
> > Fillinger
> > To: europa-list@matronics.com
> > Subject: Re: Europa-List: Mod 70
> >
> >
> > "R.C.Harrison" <ptag.dev@tiscali.co.uk> wrote:
> >> ...
> >> I understand that the part that broke ( Having been previously under
> >> extraneous circumstances!) was actually the adjuster screw thread,
> >
> > I think I'm beginning to understand. There is considerable inertia in
> > the counterweight, and a few good whacks to the tail in occasional
> > hard landings would put the lower arm components in compression once
> > too often, stripping threads? The rebound may not help either. I
> > know this is amateur engineering, but perhaps the trigear doesn't
> > suffer as badly in ungraceful handling, because the force exerted on
> > the counterweight will be less abrupt. Hope so.
> >
> > Reg,
> > Fred F.
> >
> >
> >
>
>
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