schleicher wing faults.

Any one with information on how many KA series gliders have failed when
inspected. Our club has a 100% fail rate - one Ask-8 four ribs bad.

Only know of one other failure in the country though (a K7) so 2/24. Still not a
particularly good number, so I would like to do an informal test. How many
tested, of each type, and how many problems.

Bruce Greeff wrote:
Any one with information on how many KA series gliders have failed
when inspected. Our club has a 100% fail rate - one Ask-8 four ribs
bad.

Only know of one other failure in the country though (a K7) so 2/24.
Still not a particularly good number, so I would like to do an
informal test. How many tested, of each type, and how many problems.

Bruce,
A bit more information is needed. "Four ribs bad" doesn't tell me
much.
Were they broken, delaminated from the skin, individual parts unglued
from each other, etc.
Also, the average weather conditions in which the glider(s) is/are
stored, and how stored: Assembled in a weatherproof hangar, packed in
a trailer, tied down outside etc.
There are a number of factors which need careful assessment for wooden
structures, the type of glue used being paramount, but the careful
storage of the glider is a big factor too. Over here in Oz there are
intense inspections of wooden gliders (and metal also) at 10 year
intervals throughout their lives, and I am sure there have been
numerous repairs carried out as a result of these inspections. The
details would be written up in the logbook for each aircraft, and a
summary would be lodged with the Gliding Federation airworthiness
group. I don't know of any statistical analysis of these reports, but
the general trend is enshrined in the "glider engineering" notes and
instructions for carrying out the 10 year surveys issued by the GFA.
In fact when a particular glider is due for a survey, the GFA issues
directives on particular aspects of the airfame it needs to be
particularly checked, and these would include known glue problems for
the type as well as past damage repair etc. for the particular glider.
I don't know the system of control of gliding in South Africa, but
such data may also be available there ?
Cheers, John G.

Hi John

No big deal, we have been flying and maintaining wood and fabric for years. I
was just wondering if this is a time related thing. This would be indicated by a
large cohort of failures around the same duration from build.

As for the specific Ka-8b it has been in South Africa for seven years as far as
I could ascertain. Storage here has been good, in a dry hangar, although in one
of the damper parts of the country. (That does not say much by the rest of the
world's standards)Unfortunately the previous maintenance and care is unknown to
us as a new club member purchased it a month ago. We only got to see it two
weeks ago for the first time.

There are annual checks for airworthy condition, and I would have expected these
problems to be picked up then. That was about six months ago in this aircraft,
so iether the inspection was inadequate, or there has been significant and
fairly rapid deterioration - hence the question.

Just for information, we have two Scheibe Bergfalkes of similar constructon and
have not, to my knowledge, had a glue failure so far. A little like the 2-33 I
suppose it is built so strong it never breaks, but performance suffers.

The failures we- (counting the root rib as #1).

Port wing -

Rib 2 partial failure of the rib glue on at least one biscuit. Audible
movement (about 1mm free) of the rib cap was possible with light pressure from
above.
Rib 3 partial failure of the rib glue, apparently on the majority of the
rib. The top rib cap moves freely approximately 2-3mm.


Starboard wing -

Rib 3 partial failure of the rib glue on at least one biscuit.
Approximately 2mm movement of the rib cap was possible with light pressure from
above.
Delamination was found in the area around the aileron drive bell-crank.

The rest of the structure appears to be in good condition externally with no
wrinkles in the fabric and no delamination detected.

In general we consider finding a loose cap or a single glue failure an expected
problem, and a normal maintenance issue, but four at once is cause for concern.

Bruce



Bruce Greeff wrote:

Any one with information on how many KA series gliders have failed
when inspected. Our club has a 100% fail rate - one Ask-8 four ribs
bad.

Only know of one other failure in the country though (a K7) so 2/24.
Still not a particularly good number, so I would like to do an
informal test. How many tested, of each type, and how many problems.


Bruce,
A bit more information is needed. "Four ribs bad" doesn't tell me
much.
Were they broken, delaminated from the skin, individual parts unglued
from each other, etc.
Also, the average weather conditions in which the glider(s) is/are
stored, and how stored: Assembled in a weatherproof hangar, packed in
a trailer, tied down outside etc.
There are a number of factors which need careful assessment for wooden
structures, the type of glue used being paramount, but the careful
storage of the glider is a big factor too. Over here in Oz there are
intense inspections of wooden gliders (and metal also) at 10 year
intervals throughout their lives, and I am sure there have been
numerous repairs carried out as a result of these inspections. The
details would be written up in the logbook for each aircraft, and a
summary would be lodged with the Gliding Federation airworthiness
group. I don't know of any statistical analysis of these reports, but
the general trend is enshrined in the "glider engineering" notes and
instructions for carrying out the 10 year surveys issued by the GFA.
In fact when a particular glider is due for a survey, the GFA issues
directives on particular aspects of the airfame it needs to be
particularly checked, and these would include known glue problems for
the type as well as past damage repair etc. for the particular glider.
I don't know the system of control of gliding in South Africa, but
such data may also be available there ?
Cheers, John G.

I think that Bruce is referring to the checks being carried out
following the procedure that the BGA put out following the grounding
of wooden Schleicher gliders in the UK. In South Africa - we follow
the BGA guidelines when it comes to technical issues and thus all the
KA gliders are being inspected - even though they were not grounded as
in Britain.

At Goldfields Gliding Club - two of our K-7's and our K13 were
inspected and found to be acceptable. Our third K-7 is not flying
presently (only recently imported from Germany) and will be inspected
in due course.

Clinton
LAK 12

On Sun, 15 Aug 2004 19:28:53 UTC, Bruce Greeff
wrote:

: Any one with information on how many KA series gliders have failed when
: inspected. Our club has a 100% fail rate - one Ask-8 four ribs bad.

Happens all the time when hangaring is careless, or where people thing
that violent flexing of the trailing edge is the way to discover
broken ribs.

Ian


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