As regards tail chutes - I personally would be very
happy indeed if I could get a new glider for my personal
use supplied with a tail chute and I have extolled
their virtues as emergency devices several times previously
on RAS. Unfortunately the fact is that there is a
history practical problems with reliability - especially
in club gliders and syndicates. (When I owned my own
Kestrel I took the chute home after each flight, repacked
it, and kept it in the airing cupboard to make sure
it was dry. The Kestrel also had an excellent spring
loaded actuator and a reliable mini-otfur type of release
for jettisoning. I was very confident in it.) Unfortunately
I just don't see tailchutes being put on to gliders
as emergency speed limiting devices partly because
the manufacturers would likely feel legally exposed
by the inclusion of such hit or miss, owner-maintenance-dependent
items for such a critical application.

I started to think about whether there could be a more
reliable hardware rather than fabric alternative device
tailored more towards emergency speed control than
approach control and the best I could come up with
was what was in in the last posting. BTW I don't think
that what I hand in mind would add anything like 20lbs
a pair to the glider weight.

My main motivation in starting this thread was to guage
and encourage the support for the inclusion of off-wing
emergency speed limiting devices and whatever turns
out to be the best option has my support. As gliders
get slippier and wings get thinner and design margins
get tighter and average pilot ages and reaction times
increase we either have to seek technical help or accept
that numbers over VNE accidents are going to increase.
Nothing will happen without recognition that there
is a need and customer demand for a solution.

John Galloway









At 00:24 29 March 2004, Bill Daniels wrote:
Now I'm second thinking myself.

If the devices proposed added 20 pounds to the glider,
wouldn't those same
20 pounds added as carbon fiber pultrusion rods in
the spar caps increase
both the ultimate load factor and Vne enough to resolve
the problem in a
better way?

Bill Daniels (again)

'Bill Daniels' wrote in message
...
I'd vote for the tail 'chute.

It has been approved before, it has other uses than
in a near Vne
incident,
the modification is relatively easy and it's light
weight.

True, it's not 100% reliable but neither are the personal
'chutes we wear
yet they are deemed very useful.

Bill Daniels

'John Galloway' wrote in message
...
Through the contributions to the avoiding VNE thread
runs the theme of the difficulty of avoiding overspeeding
and/or overstressing some modern designs in accidental
spin recovery. This is made more difficult than
in
older composite gliders because they had a little
more
drag and a little more (fortuitous) margin in the
g
limits.

Is it not blindingly obvious that there is a need
for
an emergency drag device that does not reduce the
G
limits of gliders? Clearly if we all handled the
recovery
from inadvertent spins etc perfectly all would be
well
but equally clearly that does not always happen and
it is a shame to lose pilots in this situation.

As the Phoebus pilot pointed out a tail chute is
ideal
for this - providing that it can be made to actuate
and jettison reliably. (I found the design used
on
the Kestrel particularly good and I never once had
a failure for landing use) On the other hand they
are expensive and inconvenient to replace and there
are several ways that they can fail.

So can anyone think of a better idea than a chute?
The best I can come up with is some sort of flush
fitted rectangular-with the-long-edge-horizontal
rear
hinged airbrakes (like old fashioned automobile suicide
doors) located on the fuselge sides somewhere in
the
region below or below/behind the wings. If they
opened
to about 45 degrees with a spring actuator (and limited
by sliding metal stays that hinge/attach to the front
of the panel and whose inner ends slid along in runners)
then they would provide a lot of drag without any
deep
internal mechanism (such as wing airbrakes have).
Once they have done their job the rear end of the
brakes
could be released by a spring loaded mechanism similar
to the front end so that the brakes would then instantly
spring to as position set out from and parallel to
the fuselage so that there would be very little drag
- only that provided by the stays at both ends and
the brake panels edge on to the wind. That configuration
would be good enough to fly home with. It would
only
be possible to reset these brakes on the ground and
they would not replace conventional wing airbrakes
for approach control - although they could have a
secondary
use for emergency approach control.

I am envisaging something the could be included in
new designs although there does not seem to be any
obvious reason why such a device could not be retrofitted
as a fairly major modification. The contours of
the
brake panels would be specific to the individual
fuselage
type but the mechanism could be generic. The assembly
would be fairly shallow and complete within itself
apart from e.g. a cable release attachment.

I am not advocating a technical solution to this
problem
in place of spin recovery practice but I do think
that
there must be something that the combined intellects
of the gliding community can come up with other than
observing that if we get into that particular overspeeding/steep

attitude condition we are stuffed.

Anyone got any simpler or better ideas? I am definitely
not an engineer.

John Galloway