Is everybody afraid of World Class?

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.

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

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.



Thanks, and best regards

Bob K.

Bob Kuykendall wrote:

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.

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

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.

On my ASH 26 E, the gas spring and the weight of the canopy supply a
noticeable closing force when the canopy is held open a few inches. I
think this would be plenty to engage a simple latch that would keep the
canopy from opening in flight. By "opening", I mean it might allow the
rear edge of the canopy to rise an inch or two, but no more. The usual
latches would still be used to secure it closed.

In fact, the "Roeger hook" mechanism it has already works like this.
It's two small springs in the fuslage that the spike on the canopy
engage as it is lowered the last 10 mm or so. I don't think the canopy
needs to be totally self-latching, as a partial latch that keeps the
canopy from flying completely open would be a big improvement. It would
pop up and inch or two during tow, alerting the pilot to the situation
without causing him a problem. He could release and land, or perhaps
simply push it closed after releasing from a normal tow.


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Eric Greenwell
Washington State
USA

"Eric Greenwell" wrote in message
...
...a simple latch that would keep the
canopy from opening in flight. By "opening", I mean it might allow the
rear edge of the canopy to rise an inch or two, but no more. The usual
latches would still be used to secure it closed.

Sure! You mean like the safety latch on the hood of a car. A good idea,
but it would have to be incorporated into the design of the latch/handle so that
the canopy could be raised in one operation (so as not to trap someone inside
who urgently wants to depart). Again, this dual function would operate just
like the hood latch on many (older) cars! When was the last time you saw an
accident caused by the hood of a car opening accidently?

... I don't think the canopy
needs to be totally self-latching, as a partial latch that keeps the
canopy from flying completely open would be a big improvement. It would
pop up and inch or two during tow, alerting the pilot to the situation
without causing him a problem. He could release and land, or perhaps
simply push it closed after releasing from a normal tow.

I agree.

Vaughn

Eric Greenwell wrote in message ...

On my ASH 26 E, the gas spring and the weight of the canopy supply a
noticeable closing force when the canopy is held open a few inches. I
think this would be plenty to engage a simple latch that would keep the
canopy from opening in flight. By "opening", I mean it might allow the
rear edge of the canopy to rise an inch or two, but no more. The usual
latches would still be used to secure it closed.


I suppose there is a first time for everything and at Parowan I manged
to launch with my P tube trapped under the instrument panel of my
ASW-28. Didn't notice the problem until well out on course so my
options were don't pee, or open the canopy to free it.

I very carefully held the canopy frame on one side and released the
latch on that side. Nothing happened. I then repeated the procedure
on the other side holding on even more strongly. Again nothing
happened. I was very surprised that I had to strongly push up on the
canopy to get it to open the half inch I need to free the P tube. I
was trimmed for about 60kts I think. It may behave differently at
different speeds.


Andy

Andy Durbin wrote:
Eric Greenwell wrote in message ...

On my ASH 26 E, the gas spring and the weight of the canopy supply a
noticeable closing force when the canopy is held open a few inches. I
think this would be plenty to engage a simple latch that would keep the
canopy from opening in flight. By "opening", I mean it might allow the
rear edge of the canopy to rise an inch or two, but no more. The usual
latches would still be used to secure it closed.



I suppose there is a first time for everything and at Parowan I manged
to launch with my P tube trapped under the instrument panel of my
ASW-28. Didn't notice the problem until well out on course so my
options were don't pee, or open the canopy to free it.

I very carefully held the canopy frame on one side and released the
latch on that side. Nothing happened. I then repeated the procedure
on the other side holding on even more strongly. Again nothing
happened. I was very surprised that I had to strongly push up on the
canopy to get it to open the half inch I need to free the P tube. I
was trimmed for about 60kts I think. It may behave differently at
different speeds.

I am curious about how different canopies will react to being unlatched.
The Schleicher design appears to have air pressure holding it down, at
least in the closed position. I don't know what happens if turbulence
were to bounce it up a few inches.

A friend had his DG 400 canopy open in flight, and stay open, so he had
to pull it closed. His headphones and various things flew out of the
cockpit. Fortunately, he was quite high at the time, and dealt with it
successively, but (as I recall) could not retrieve the headphones, so
the cord kept the canopy from latching after he pulled it back down.

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Eric Greenwell
Washington State
USA

In an RV-3, recently an unlatched side opening canopy
ripped off with a loud bang in flight and a friend of mine
lost his glasses with it. 100 knots in the open air
isn't fun.

He landed safely, but said it was exciting.

Katana canopies (clamshell) and side opening canopies
don't sound so great to me. Yep, the L-13 canopy
with self-latch seems pretty good, but for one seaters,
the rear-opening canopy seems like the best.
Besides, I like the vis a lot better than with
bars in the way...

I am curious about how different canopies will react to being unlatched.
The Schleicher design appears to have air pressure holding it down, at
least in the closed position. I don't know what happens if turbulence
were to bounce it up a few inches.

A friend had his DG 400 canopy open in flight, and stay open, so he had
to pull it closed. His headphones and various things flew out of the
cockpit. Fortunately, he was quite high at the time, and dealt with it
successively, but (as I recall) could not retrieve the headphones, so
the cord kept the canopy from latching after he pulled it back down.

--
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Eric Greenwell
Washington State
USA



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Mark Boyd
Avenal, California, USA

"Mark James Boyd" wrote in message
news:412d0013$1@darkstar...
In an RV-3, recently an unlatched side opening canopy
ripped off with a loud bang in flight and a friend of mine
lost his glasses with it. 100 knots in the open air
isn't fun.

He landed safely, but said it was exciting.

Katana canopies (clamshell) and side opening canopies
don't sound so great to me.

Yes, they open in front and can not maintain level flight with them open.
I think about three Katanas have been shot down by their canopies. I notice
they turned the canopy around on the 4-seater.

Yep, the L-13 canopy
with self-latch seems pretty good, but for one seaters,
the rear-opening canopy seems like the best.

Without a doubt!

Vaughn

"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.