"Bob Kuykendall" wrote in message
om...
The problem as I see it with self-latching canopies on modern
sailplanes has several quite thorny aspects, and I have no intention
of going there.

It may not qualify as a "modern sailplane" but the L-13 has such a latch.
Have you ever heard of an L-13 having a canopy accident? I haven't, (though
someone probably will dredge one up); the G-103 is a different matter!


The key to the problem is the activation impulse required to activate
self engaging latches: the slam.

It is a matter of design and training. First, no slam should be necessary.
The mechanism should be designed so that the canopy always latches with gravity,
so that the canopy will always be latched when closed. An inadvertant slam
could also be damped with padding or mechanical dampers. Furthermore, slams can
(and should) be minimized with training. Every student of mine comes away from
his/her first lesson having heard the "canopy lecture", which includes
instructions to not slam or stress the canopy in any way, to always check that
the canopy is latched when it is closed (particularly if you are going flying),
and to never walk away from an open canopy, and the "checklist lecture" (the
canopy is on the checklist).

As a first experiment, I'd suggest you go buy an ASW-27, remove the
gas spring from the canopy pivot mechanism, and then spam the canopy
closed several hundred times. Please report your findings in this
forum.

Though I respectfully disagree with you that canopy cracks must result from
self-latching mechanisms, how many cracked canopies would it be worth to prevent
an accident like this one below which (as I recall) killed a young girl taking
her first glider ride?

Aircraft: Burkhart Grob G 103C, registration: N103VT
Injuries: 1 Fatal, 1 Serious, 1 Minor.
During takeoff for a glider tow operation, the towplane and the glider both
became airborne. An FAA Inspector witnessed the takeoff and said his attention
was drawn to the 'erratic pitch changes' of the glider. The glider pilot's
canopy was open, and the pilot repeatedly attempted to close the canopy. Pitch
changes and climbs above the tow plane accompanied each attempt to close the
canopy. As the towrope reached a vertical position, the towplane struck the
ground, nosed over, and came to rest inverted. The towrope separated, and the
glider continued past the towplane, rolled left to an inverted position and
impacted the ground.
http://www2.ntsb.gov/ntsb/brief.asp?...11X11267&key=2



Vaughn





Thanks, and best regards

Bob K.