blanik life limits, and new AD

It looks like there is a new (US) AD for the L13 comming, cracks
where the control sticks attach to the "control bridge".
My biggest question is the life limits for the L13. We do a lot
of structural work here, and I cannot find anything on our L13 that
looks questionable. I am not at the limit, but will be eventually,
Have there been any problems or failures? What is being done to
address this limit, and how far have operators gone . and what did
they do to stretch this limit. This is for US based planes mostly,
but other countries would certainly interest me. I hear all sorts of
things about 10,000 hours on L13s, but have no real information.
thanks a bunch, John Barron 573 565 2819

Hi John,

We just went through the exercise of completely overhauling our Blanik
L-13 here in Colombia since we had questionable historic maintenance
records in addition of a complete lack of documentation for the first
4 years before the glider was brought to Colombia. Since we are about
to start using the Blanik extensively again for training on a brand
new winch as well as possibly for acro I did some more extensive
research of what has been done to address the metal fatigue issues
etc.

The most detailed information is published by the Australians, since
our Blanik is registered as an Ultralight (similar to the US
Experimental certification) I decided to use their maintenance and
life time extension regime as the basis for our maintenance schedule
and the tasks to be performed during the overhaul. Here the link for
the Australian documentation based on some excellent research they
have done down under to properly address the known metal fatigue
issues:

http://www.gfa.org.au/airworth/blanik.php

IIRC the US gave the L-13 originally 3750 hours, the UK and Australia
set the initial limit at 5000h and let you extend the lifetime limit
under certain conditions to 10,000/12,000h but the US might only allow
an extension to 4500h.

We have a documented 1650h on the glider while in the club plus the
first 4 years of which we know nothing (except that the glider was
initially sold to the US and probably got to Colombia from there, no
accident reports for our Serial # in the NTSB database). We then used
2000h as a base line (adding 350h for the first 4 years) and performed
a combined 2000h 20/+10 year inspection as outlined by the Australians
including the eddy current checks on the wing spars just to be sure.
We will from now on stick to the inspection regime recommended by the
Australians based on 2000h plus accumulated hours since the 2000h
inspection (The next 20/+10 year inspection will be in 2015 based on
the original manufacturing year - 1975).

The standard AD's can be found on Blanik America's site here (you
probably know that):

http://www.nwi.net/~blanikam/ba/serv01.htm

Vitek is always very helpful to address any issues you might have, I
had frequent conversations with him while trying to figure out what we
needed to do. He concurred that the Australian regime is probably the
most detailed around.

I hope this helps a bit, let me know if you have any questions,

Markus Graeber