L13 Blanik Mandatory Bulletin

On Jun 23, 9:31*pm, harold wrote:
On Wed, 23 Jun 2010 16:35:56 -0700 (PDT), Judah Milgram

wrote:

snip





Most modern gliders are stressed to take at least +5.3/-2 g without
damage. A winch launch comes nowhere near this as long as the correct
weak link is fitted, which will break well before the glider does. I
believe that the glider that failed had being doing aerobatics
immediately before, which is a more likely cause of any
overstressing.

Derek C

If I recall correctly, the concern was with fatigue damage
accumulating at loads below the limit load. If fatigue cracks do form,
you could get a static failure below limit load - and not necessarily
during a winch launch. How serious this concern should be in the case
of the L-13 I couldn't say but given that they think it might have
been a fatigue crack, the AD seems pretty reasonable.

JM.

Actually and AD has not been issued by the FAA. *A mandatory bulletin
from the manufacture has been issued. *There is a huge difference. *An
AD is mandatory in the US. *A mandatory bulletin by the manufacture is
optional.

You're right, the subject AD was issued by EASA, not FAA. But given
that a wing just failed due to a possible fatigue crack, most US
owners will probably want to comply anyway (just guessing here).

Judah Milgram

On Jun 23, 9:23*pm, Judah Milgram wrote:
On Jun 23, 9:31*pm, harold wrote:





On Wed, 23 Jun 2010 16:35:56 -0700 (PDT), Judah Milgram

wrote:

snip

Most modern gliders are stressed to take at least +5.3/-2 g without
damage. A winch launch comes nowhere near this as long as the correct
weak link is fitted, which will break well before the glider does. I
believe that the glider that failed had being doing aerobatics
immediately before, which is a more likely cause of any
overstressing.

Derek C

If I recall correctly, the concern was with fatigue damage
accumulating at loads below the limit load. If fatigue cracks do form,
you could get a static failure below limit load - and not necessarily
during a winch launch. How serious this concern should be in the case
of the L-13 I couldn't say but given that they think it might have
been a fatigue crack, the AD seems pretty reasonable.

JM.

Actually and AD has not been issued by the FAA. *A mandatory bulletin
from the manufacture has been issued. *There is a huge difference. *An
AD is mandatory in the US. *A mandatory bulletin by the manufacture is
optional.

You're right, the subject AD was issued by EASA, not FAA. But given
that a wing just failed due to a possible fatigue crack, most US
owners will probably want to comply anyway (just guessing here).

Judah Milgram
- Hide quoted text -

- Show quoted text -

You may be right for the U.S., but I don't believe you are correct for
Canada.
I haven't had a chance to check the precise regulation, but a
mandatory bulletin from a
manufacturer or EASA becomes mandatory in Canada due to cooperation
agreements.
Canadian L-13's are therefore grounded until the AD is complied with.