DG-300/303 owners...

On 17 Apr 2007 00:33:55 -0700, "
wrote:


So what is different here?

Boeing is still in business.

manufacturer of the DG-300/303 was Glaser Dirks which has been out of
business for several years now.
The current company DG Flugzeugbau merely does the service for all the
former Glaser Dirks aircraft prior to the DG-800.


It will only take one crusty in his DG flying the old placard speeds,
making it clap hands and they are in a whole heap of trouble.

The fact that no DG-300 ever loast its wings clearly proves that the
structure is strong enough to handle the flight loads.


This is a nightmare for DG300/303 owners, I almost became an owner
last summer as I was looking at a DG303 acro.

if you want to do aerobatocs in a 303, you're screwed.
99.9 percent of all other DG-300 pilots won't even notice the
restrictions.


Bye
Andreas

The wings are reparable so they shouldn't have to
provide free replacements. Since it is a fiberglass
spar cap and the problem seems to be limited to the
wing root it MIGHT be possible to cut a slot into the

rovings and embed some Graphlite carbon fiber rods
into the spar cap. If this is doable the result could
be a far stronger spar than the original design. I

don't think you could do this with a carbon fiber spar
cap but i'm not sure about fiberglass.

http://www.marskeaircraft.com/carbonrod.html


It is inexcusable for these wings to still be allowed
to fly at lower
placarded limits as DG has no knowledge of the condition
of the entire
fleet.
DG should sue Elan for screwing up and DG owners should
get a free
set
of wings to replace the bad ones they bought in good
faith.
Its not like you can glue a new spar in the place where
its bad!!

Regards

Al



On Apr 16, 11:39 am, Steve Davis
wrote:
At 17:36 16 April 2007, Marc Ramsey wrote:

Alan Montague wrote:
Is there any scope for non-destructive testing by
industrial
radiology?

X-rays are sensitive in showing up minor ripples
in
children's bones? Would they work for the ripples
in
my spar?

I would think that an ultrasonic inspection method

could be developed for much less cost than radiography.
Ultrasonic might be able to look into the layers of
rovings
and see how deep the undulations are. You might want

to check with some companies which make composite
aircraft and composite spars. Cirrus Design, Scaled

Composites, Adam Aircraft etc..., and find out how
they
do NDT on their designs.I again look at the Duo spar
inspections as
an example,
the original
protocol involved cutting holes in the wing skin and
visually inspecting
the spars, in short order SH evolved to using a borescope
through the
existing inspection ports and a few holes drilled
in
the root rib and
aileron cutouts, eventually someone figured how to
do it with
inexpensive lipstick cameras and long rods.

Mark

On Apr 16, 5:09 pm, Steve Davis
wrote:
The wings are reparable so they shouldn't have to
provide free replacements. Since it is a fiberglass
spar cap and the problem seems to be limited to the
wing root it MIGHT be possible to cut a slot into the

rovings and embed some Graphlite carbon fiber rods
into the spar cap. If this is doable the result could
be a far stronger spar than the original design. I


Cutting into a spar there is no good, you only move the problem
further out on the wing where the glue joint is!!

That will not work.

Carbon fibre and glass fibre do not have the same stiffness. The carbon
which is stiffer would have to carry the complete load and would break
unless being designed/dimensioned to replace the complete spar. It makes no
sense to mix the two in a spar like that.

Best regards,
Ola Røer Thorsen


Steve Davis wrote:

The wings are reparable so they shouldn't have to
provide free replacements. Since it is a fiberglass
spar cap and the problem seems to be limited to the
wing root it MIGHT be possible to cut a slot into the

rovings and embed some Graphlite carbon fiber rods
into the spar cap. If this is doable the result could
be a far stronger spar than the original design. I

don't think you could do this with a carbon fiber spar
cap but i'm not sure about fiberglass.

http://www.marskeaircraft.com/carbonrod.html

At 07:36 17 April 2007, wrote:
On Apr 16, 3:48 pm, 'Dan G' wrote:
On Apr 16, 9:26 pm, '
wrote:

Such a major flaw in a wing spar should be replaced
at the
manufacturers expense IMHO.
If Boeing shipped a plane that was discovered to have
a flaw in it
because their sub contractor failed to adhere to manufacturing
specs
or QA procedures, Boeing would fix the problem then
deal with the
sub. After all Boeing owns the paper for the sales
contract.

So what is different here?

What is different is that the manufacturing company
(Glaser-Dirks) no longer exists, would you expect DG
to be responsible for a manufacturing problem in, e.g.,
an LS3 also? Yes they could come up with a better
solution than they have so far but expecting them to
pay for it just because they sell the spare parts is
a fantasy.

On Apr 17, 1:11 am, Ann O'Rack wrote:
At 07:36 17 April 2007, wrote:

On Apr 16, 3:48 pm, 'Dan G' wrote:
On Apr 16, 9:26 pm, '
wrote:

Such a major flaw in a wing spar should be replaced
at the
manufacturers expense IMHO.
If Boeing shipped a plane that was discovered to have
a flaw in it
because their sub contractor failed to adhere to manufacturing
specs
or QA procedures, Boeing would fix the problem then
deal with the
sub. After all Boeing owns the paper for the sales
contract.

So what is different here?

What is different is that the manufacturing company
(Glaser-Dirks) no longer exists, would you expect DG
to be responsible for a manufacturing problem in, e.g.,
an LS3 also? Yes they could come up with a better
solution than they have so far but expecting them to
pay for it just because they sell the spare parts is
a fantasy.

DG acquired the IP and remains of the old Glaser-Dirks.
When acquiring the rights and user base to a company like that you
cant just pick and choose what you take responsibility for.
Also the 303's have been built by the new company so where do you draw
the line?

Plus DG also retained the original manufacturer (Elan/AMS).

'....and the pilots who fly them regard' might need
to be changed to 'the
pilots who flew them regard' unless an inexpensive
method of inspecting
and repairing them is developed by someone.

Thank you for your kind offer, but I (respectively
my club) already
own 2 DG-300...

.... and the pilots who fly them regard stories about
18.000 ft cloud
base and difficulties of staying below Vne as science
fiction.

ELAN seems to be the responsible party here. Are they
still the same
company? My understanding is they only split off the
aviation
division to form AMS but the original ELAN company
is still the same.
Please correct me if I'm wrong.

I have no idea about the situation of ELAN - but I'm
pretty sure that
their product liability has expired.
Bye
Andreas

On Apr 18, 12:30 pm, Steve Davis
wrote:
'....and the pilots who fly them regard' might need
to be changed to 'the
pilots who flew them regard' unless an inexpensive
method of inspecting
and repairing them is developed by someone.

Hmmm... I wonder who that "someone" might be. Whoever they are,
they're pretty brave to get wrapped up in this mess.

On the topic of inexpensive, that will have to be relative at best.

From correspondence and conversation with various engineers and
composites technicians, it appears that the scarf ratio for composite
repairs is determined by the ratio of the shear strength of the epoxy
to the tensile strength of the fibers. For a spar repair in E-glass,
it seems to come out on the order of 40:1, and perhaps 15% greater for
S-glass, let's say conservatively around 60:1.

My guess, based on my experience with wet fiberglass layups, is that
the degree of fiber "ondulation" will vary linearly through the depth
of the spar cap. That is, the worst "ondulation" will be at the
extreme outer fibers of the spar cap, and that there will be no
ondulation at the inner (last laid) fibers, and half way through that
depth the ondulation will be half as bad as the worst. The shame of
that is that the extreme outer fibers of a cantilever beam are the
ones with the greatest stress.

Anyhow, if the "ondulation" varies as I guess, part of the inspection
and repair process will be to assess what degree of "ondulation" is
acceptable, and how much spar cap has to be ground away to get to
acceptable fiber.

Suppose, for example, that the "Ondulated" fiber were to extend down
through 8mm of spar cap. Then you (or, more likely, the repair tech)
would have to grind out a scarf that extends spanwise through
8*60=480mm, call it a half a meter of span plus probably the full
length of the spar butt, call it a full meter. After grinding that
out, you'd have to build up the material removed by laying in new
straight rovings.

After executing the spar scarf, you'd have to repair all the
collateral damage inflicted on the wing skin when trenching down to
the spar. Probably the easiest way to do that would be with a
prefabricated patch panel, made in the original wing mold, that
encompasses the sandwich directly over the first half-meter of spar
plus 50mm or so chordwise fore and aft of the spar. The repair tech
would fit this patch panel, splice the inner skin, and execute an
outer skin scarf around the perimeter of the patch panel. After that,
gelcoat, sand, and polish to hide.

That is just my own half-informed guess at what the spar repair
entails. Your actual mileage has already varied. The response to my
own emails to DG has been on what I would call the chilly side. Their
position on this matter seems to be holding firm as follows:

* Supplementary explanations of the problem and surrounding issues
(such as the one I posted earlier) are unhelpful, since the
explanation posted on the DG Web site clearly addresses all aspects of
the issue. Beyond that, only "experts" are qualified to understand the
problem.

* Photos of affected spars are unhelpful because only "experts" are
qualified to read them, for everyone else they are just frightening.

* The inspection must be performed by DG-trained workers.

Regarding some of the repairs I've seen suggested, such as splinting
the spar with Graphlite rod, I think that those are non-starters at
best. I think that the only reasonable repair schemes are those that
restore the structure to its as-designed strength and stiffness.
Repairs that substantially alter the stress distribution through the
structure could well cause other unknown and unexpected problems.

Thanks, and best regards to all

Bob K.
Disclaimer: I'm the guy behind:
http://www.hpaircraft.com/hp-24

I'm an amateur - don't try this at work!

On 18 Apr 2007 19:30:12 GMT, Steve Davis
wrote:

'....and the pilots who fly them regard' might need
to be changed to 'the
pilots who flew them regard' unless an inexpensive
method of inspecting
and repairing them is developed by someone.

LOL... noone in my club is considering to stop flying our DG-300's...


Bye
Andreas

You have described a $20K repair on a product
which might not be worth $20K right after the
repair. My suggestion for the rods was to try
a $2K or less repair which would allow current
users the peace of mind to continue flying their
gliders.
My understanding of the DG 300 is that
it has a very stiff wing, presumably even with
undulations in the spar caps. Since Graphlite
ships in two and three ft. dia. spools it must be
plenty flexible and it is far stronger than the
equivalent amount of fiberglass rovings. My
suggestion would be to saw several kerfs of
varying lengths and depths through the undulation
area extending for some length on either side of
the area possibly to the end of the spar stubs.
Graphlite rods could be epoxied into the kerfs,
like rebar in concrete, and they would take the
load from the rovings they butt up against.
I suppose fiberglass cloth could be wrapped and
epoxied around the spar butt to prevent the rods
from popping out, if that could happen, but I think
you would have a much stronger than designed spar
with a very stiff wing. I have heard of someone cutting
a kerf in wooden spars and putting in the Graphlite
rods
to improve the strength.