Duo Discus canopy problems

[David Starer]

I recently had the alarming experience of the canopy coming nearly fully
open on a Duo Discus shortly after take-off on aerotow. Both my student (who
was flying the glider at the time) and I grabbed the handles when the canopy
was about 45 degrees open and managed to close it. However all efforts to
lock it failed, probably because the airflow was distorting the Perspex and
preventing the frame from seating correctly, so we resorted to holding it
closed. The canopy catch has had a SH mod. kit fitted which is supposed to
apply some spring pressure to keep the catch in the closed position.

The takeoff in question was a relight after landing at another airfield, and
after discussion with my student, we decided to continue the launch and had
an otherwise uneventful glide home, holding the canopy shut till we landed.

Both my student and I clearly recalled doing our pre-takeoff checks,
including confirming that the canopy was locked closed. The most likely
cause of the incident seems to be vibration during the slightly bumpy
takeoff run, which probably caused the catch to move towards the open
position.

I subsequently discovered that this has happened before. The mod. kit is
pretty ineffective as the spring isn't even strong enough to pull the catch
into the closed position when the canopy is open, let alone when the
mechanism has to engage at three points along the canopy's length.

The following day I wrapped a single turn of PVC wing tape around the catch;
enough to hold it closed, but easy to break if the canopy needed to be
opened in an emergency. The worst aspect of the whole incident was losing my
favourite gliding hat which blew off my head when the canopy opened!

Has anyone had a similar experience or advice on improving the Duo's canopy
catch?

David Starer

[John Galloway]

I was a partner in a 2001 Duo that came with the canopy
latch mod already fitted. The canopy never came open
spontaneously and I never found any tendency for the
latch to gradually open itself. BUT - several times
I found that in the front cockpit my left hand would
catch on the latch - the distal end of which projects
a bit - and several times I found that I slightly caught
the latch in the open part behind the button of long
sleeved cotton shirts. I was surprised how easily
the latch would move in flight with a gentle catch
and on one ocasion I accidentally pulled the latch
open on my shirt but was able to shut it quickly before
the canopy moved.

I would doubt that the latch of our glider would have
opened by vibration on the ground run. I do think
that the shape of the Duo latches makes them particularly
liable to be accidentally caught. It would be better
if the latch was shaped like LS latches - curved in
from the canopy frame and then back towards it so that
it is easy to get hold of but has no projecting forward
facing end.

John Galloway

[Ruud]

You wrote that you and your student were sure that the canopy was
properly locked before take-off.
The cockpit handle has to come a long way back before it unlocks the
canopy.
Probably the canopy on your duo has a rather loose fit?
It also seems that the spring pressure needs to be readjusted.

On my duo the canopy still has a tight fit after 300+ hours and lots
of tows from bumpy fields.

I think that your modification with the pvc tape is an excellent short
term solution.

[David reilly]

WANTED PIK 20b rudder

Also Pawnee Rudder and Starboard aileron

(don't ask)

--
David Reilly

[David Starer]

I hope the correspondent who sent me a private e-mail response to my earlier
post won't mind me quoting it as it gave me a good laugh:

Dear Dave,

What a problem.

Next time, Ducktape an ELT onto your hat
so that you may recover it
in due course.

David Starer

"David Starer" <Da...@DONOTSPAMMEStarer.co.uk> wrote in message
news:xPqdnbetua2...@nildram.net...