Discus CS grounded in France

As I write this, I am looking at a cross-section of an ASW-22 wing, taken from
a ship that has met with misfortune, It has styrofoam dams at the leading edge,
on both sides of the upper spar cap and at the forward edge of the drag spar.
These styrofoam dams were set just high enough to allow for a 10% excess of
glue (epoxy resin, chopped fibers, micro-balloons) that were trawled in from
the edge of one dam to the edge of the other dam. In this way, the construction
crew was 100% sure that the proper amount of glue had been spread along the
spar cap. When the upper skin was mated, all voids were filled and the excess
10% of resin was forced out each side into the styrofoam dams.
The inside of this wing is a work of art. I would expect nothing less from all
sailplane manufactures.
JJ Sinclair

(JJ Sinclair) wrote in message ...
As I write this, I am looking at a cross-section of an ASW-22 wing, taken from
a ship that has met with misfortune, It has styrofoam dams at the leading edge,
on both sides of the upper spar cap and at the forward edge of the drag spar.
These styrofoam dams were set just high enough to allow for a 10% excess of
glue (epoxy resin, chopped fibers, micro-balloons) that were trawled in from
the edge of one dam to the edge of the other dam. In this way, the construction
crew was 100% sure that the proper amount of glue had been spread along the
spar cap. When the upper skin was mated, all voids were filled and the excess
10% of resin was forced out each side into the styrofoam dams.
The inside of this wing is a work of art. I would expect nothing less from all
sailplane manufactures.
JJ Sinclair

It is interesting that you mention dams on BOTH sides of the upper
spar cap, as the AD for the Duo Discus had an inspection of the rear
side of the upper spar cap only. There must be an assumption that if
epoxy resin oozed out the back it equally oozed out the front side.
How good is that assumption? If it is possible to have voids where
there is no bonding of the cap to the shear web it must also be
possible to have a partial bonding of the upper aft corner of the web
but not the top and front side. How strong would this spar be? Would
it fail after 1000 hours and only in "extreme turbulance"? Why
wouldn't they have checked both sides of the spar?

In article ,
(Slingsby) writes:

the AD for the Duo Discus had an inspection of the rear
side of the upper spar cap only. There must be an assumption that if
epoxy resin oozed out the back it equally oozed out the front side.
How good is that assumption?

I think SH has you inspect the aft face of the spar because the front side has
a foam dam to help keep the bonding paste from squeezing out. So if there is a
void at the aft side then the void may or may not go through to the front side.
If there is no void it highly likely that there is enough bonding paste all
across the bonding area.

Now I if you don't like the word "likely" when applied to this particular
process then you should not fly any composite glider because such assumptions,
based on tests and real world experience, are used through the construction
process. 100% inspection of every bonded joint is impossible given the
constraints of manufacturing of gliders as it is done now. Perhaps these
incidents will cause the LBA and manufactures to re-think the inspection
standards. And likely raise the price of an already costly toy.

Robert Mudd

Now I if you don't like the word "likely" when applied to this particular
process then you should not fly any composite glider because such assumptions,
based on tests and real world experience, are used through the construction
process. 100% inspection of every bonded joint is impossible given the
constraints of manufacturing of gliders as it is done now. Perhaps these
incidents will cause the LBA and manufactures to re-think the inspection
standards. And likely raise the price of an already costly toy.
Robert Mudd
************************************************** *********************************
W. Edwards Deming the father of statistical process control showed
that a 100% inspection system will regularly miss 20% of the defects.
The goal of manufacturing and design should be to develop a process
which minimizes the likelyhood of defects, especially catastrophic
defects.
The DG website has a very detailed explanation of how a wing is
constructed and I assume the technique is similar for all German
designed gliders. Spar CAPS are formed with carbon fibre rovings and
are inspected in minute detail for voids and any cap which fails
inspection is immediately cut in half to preclude its inadvertant use.
As the upper and lower wing skins are moulded, the spar caps are
glued in place so that they are well bonded to the skin. So far so
good, the top and bottom of an I-beam shaped spar are well built and
in place. Next the shear web, which is also well built and inspected
is glued into the bottom part of the spar cap. Gravity holds the glue
in place and the surface is well lighted and clean so the craftsmen
and inspectors can see what is happening. The wing spar is now an
upside down T shape. Later on in the process the top surface of the
wing is glued to the bottom half forming both a wing and a complete
spar. It can be SEEN that the exterior surfaces of the wing are well
mated because epoxy oozes out of the joints. It can only be ASSUMED
that the upper spar cap is well bonded to the shear web because the
glue joints cannot be seen. Assuming you have a good spar because of
German craftmanship works because German craftsmen are quite good, but
it is not a well designed manufacturing process. Building a complete
spar outside of the wing and then bonding it to the upper and lower
surfaces strikes me as a process much less likely to lead to a
catastrophic failure. In the case of the Duo Discus and probably the
Discus CS, failure of the spar is more of a process defect than an
inspection defect.
The price of these costly toys may indeed go up but something bad has
just happened to the value of Shemp Hirth products.

"I assume the technique is similar for all German designed gliders."

Very bad assumption. Not even the same for all products from each mfg.

"Dave Nadler \"YO\"" wrote in message .. .
"I assume the technique is similar for all German designed gliders."

Very bad assumption. Not even the same for all products from each mfg.
Could you please explain some of the different spar construction
methods used by the different German manufacturers? Which ones use a
spar which is constructed outside of the wing assembly process?

Earlier, Slingsby wrote:

I assume the technique is similar
for all German designed gliders."

And Dave Nadler replied:

Very bad assumption...

And Slingsby responded:

Could you please explain some of
the different spar construction
methods used by the different
German manufacturers? Which ones
use a spar which is constructed
outside of the wing assembly process?

To which I say:

Slingsby, I think you kind of slipped a groove back there. You started
off by talking about "German designed gliders," but after Dave
responded you changed the topic to German manufactured gliders.

Design and manufacture are two different things.

A survey of the Akaflieg Web pages might show a couple of examples of
German designs with the characteristics you are talking about. What
then?

Bob K.

At 14:12 19 September 2003, Nick Hill wrote:
John Galloway wrote:
At 22:48 18 September 2003, Slingsby wrote:

The price of these costly toys may indeed go up but

something bad has
just happened to the value of Shemp Hirth products.


snip...


Firstly, only spars built at the Czech factory were
built incorrectly using an simple error in the technique
which has been identified and we can be pretty sure
it has been eliminated.

Secondly, therefore, the bulk of the German built
SH
fleet are unnaffected and I think the glider buying
public are informed enough to be able to figure that
out.

Thirdly, all the SH gliders that could possible be
affected (i.e. Discus and Duo with Czech wings) have
been or will be inspected and, if necessary, repaired
and brought up to full airworthiness.


Maybe a better statement is the reputatation of Schempp
Hirth products
and procedures. It is fine to say the Czech built ones
are at fault but
you buy them from Schempp Hirth who therefore carry
the responsibility
for the production and quality control.

Nick Hill


Better than this.

When our club ordered its Discus B they specifically
asked for a German built glider and payed more for
the privilege, they were told that 'some components
would come from the Czech republic in accordance with
normal manufacturing' it turns out that 'some components'
are the sodding wings, the glider was grounded (during
a competition!) and the club is still losing revenue.

At 17:42 19 September 2003, Marc Ramsey wrote:

I believe some recent Ventus 2 wings were also constructed
in the Czech factory,
I would hope they have plans to inspect those, as well.

Marc,

Agreed.

However, according to what we were told the construction
technique error on the Duos, at least, was so simple
and specific that they might be able to positively
identify some Czech spars that are not under suspicion.


IMHO it would be in Schempp-Hirth's best interests
to publish a full account of the production problem,
the rationale behind the inspection and repair procedure,
and the actions taken to ensure future quality standards.

John Galloway

At 22:06 19 September 2003, Slingsby wrote:
John Galloway wrote in message news:...
At 22:48 18 September 2003, Slingsby wrote:

The price of these costly toys may indeed go up but
something bad has
just happened to the value of Shemp Hirth products.


This is unlikely to happen as glider buyers and sellers
are not fools. Buyers are unlikey to avoid gliders
that are perfectly airworthy and sellers are unlikely
to give them away. If they aren'r aware already bofore
long they will be that:

The opinion that 'Safety doesn't sell' which is discussed
on the DG
website might provide an argument to your statement
that buyers and
sellers are not fools. The concept of a Czech manufactured
Duo Discus
or Discus being 'perfectly airworthy' is in the eye
of the beholder.
As I ponder whether or not to buy a used Discus, which
is the better
log book entry, 'AD complied with and no voids in the
wing spars were
found,' or 'AD complied with and a sufficient amount
glue was squirted
into the wing spar so that they can never fall apart.
Wings are now
perfectly airworthy.'

That's not the full repair . I agree that I would
prefer one that didn't need a repair - but mainly because
it didn't have holes cut in the wing skins to do the
work. I was also very pleased that ours were OK.


The airworthiness of passed or repaired wings is not
in the eye of the beholder - unless you have some technical
information to show otherwise - or perhaps you think
the factory, the LBA and the local airworthiness organisations
are incompetent or part of a conspiracy?


Firstly, only spars built at the Czech factory were
built incorrectly using an simple error in the technique
which has been identified and we can be pretty sure
it has been eliminated.

Right, a 'simple error in the technique' lead to wings
breaking off in
normal flight. We can be 'pretty sure' it has been
eliminated because
we sent our best German craftsmen to the Czech factory
to, once again,
show them how to spread glue on a spar cap. The problem
is eliminated,
Murphys Law will not rear its ugly head around here
again.

I am not sure what point is being made in the above.
As far as I am aware Murphy's Law is spread evenly
throughout human activity. I thought that's what it
was about. And are you suggesting that retraining
cannot possibly correct a production error?

Secondly, therefore, the bulk of the German built
SH
fleet are unnaffected and I think the glider buying
public are informed enough to be able to figure that
out.
The glider buying public will also be informed whenever
a Shemp-Hirth
glider breaks apart in flight.


How could it be otherwise?



Thirdly, all the SH gliders that could possible be
affected (i.e. Discus and Duo with Czech wings) have
been or will be inspected and, if necessary, repaired
and brought up to full airworthiness.

Right, and the German built gliders couldn't possibly
be affected because
none of them have broken apart, yet. Until then, they
are fully airworthy.

Are you accusing Schemmp-Hirth of lying when they say
that only Czech wings were built by the faulty technique?
Or are you suggesting that properly built spars are
not airworthy? If so back it up - and remember that
this is a public forum.


As an inspected Duo owner I have made it my business
to be certain in my own mind that an inspected or
repaired
glider will be at full design spar strength - for
example
that there have been no post manufacturing new delaminations
in the Czech wings, that wings that pass the visual
inspection actually are strong.

I have no particular sentimental attachment to Schemmp-Hirth
and no business relationship with them. Like most
affected owners I was pretty upset but now I know
the
facts I feel no need to be concerned about the strength
or value of our Duo. I have also just ordered a new
Schempp-Hirth glider.

Lastly, there is no reason to think that the cost
of
new gliders will go up. There is nothing wrong in
principle with the way that they are built - as long
as they are built as intended.

John Galloway

They weren't built as intended, and the blind method
of assembling
the spar as the wing is being assembled is wrong in
principle. You
should be pretty upset, THEY DIDN'T GLUE THE SPAR TOGETHER.
Not just
one, THEY DIDN'T GLUE THE SPAR TOGETHER ON A WHOLE
BUNCH OF WINGS. Oops!!!

This is simply stating what we already know. That
is the starting point of the whole problem. Things
have moved on from there and the wings are being checked
and repaired if needed. It is self evident that this
is the biggest manufacturing error in modern gliding
history but it is being sorted - not without a lot
of inconvenience and irritation for the owners but
it is happening.

As regards the 'blind' construction method for the
spars - if you have knowledge to suggest that passed
or repaired Czech wings, or German built wings, or
any SH wings built from now on are not airworthy please
state it. This is, as you are shouting out, a pretty
serious matter and would benefit from information rather
than assertion or insinuation.

'now I know the facts I feel no need to be concerned
about the
strength or value of our Duo. I have also just ordered
a new Shemp-Hirth
glider' Nice sales pitch, how much are you asking
for your Duo?

It would not have been proper for me not to have declared
my relevant interests in this matter and why it has
been important to me to be sure of the situation.
Weather permitting, tomorrow (like all the other inspected
owners) I will be betting my life that our Duo spar
is sound and then, in the future, I will also be betting
a bigger chunk of the value of my house than I like
to think about that the next glider will also be sound.


Our confidence in the structural integrity of a composite
aircraft comes from our confidence in the integrity
of of the constructor. That isn't a complete defence
against a mistake being made and when it does we then
have to judge whether the constructor has shown the
integrity to learn from the problem, make good the
consequences of it, make sure it can't happen again,
and then extend the audit process to prevent other
types of error occuring in the future.

Your feelings about this problem are much milder than
mine were a few weeks ago. As far as I was concerned
I had to get all the facts I could and then judge whether
(as said before) I was being told the truth or whether
several agencies were being simultaneously incompetent
and/or dishonest because that would be the only other
logical conclusion.


John Galloway