Thanks for that. It would seem therefore that the standard
conical chute is the only choice for the majority of
glider pilots on the grounds that it is likely that
we will only ever use it if we have to.As I have already
said, if it is good enough for Martin Baker it's good
enough for me.
I am firmly of the opinion that people who jump out
of perfectly serviceable aeroplanes are .........how
can I put it.......... lacking in some way. :-)



At 21:30 06 April 2005, Michael wrote:
I don't think you will find that there are any emergency
prachutes with square canopies, they are all round.

Not true. Both Relative Workshop and Strong make emergency
rigs that
will accept square reserve canopies, and will sell
them to you if you
convince them you know what you are talking about when
you ask for one.
They're the only kind I use.

Square parachutes while offering more control
when open require the wearer to be in a stable position
when the chute is deployed, they are therefore less
reliable when deployed in anything other than a stable
attitude.

Not true. Square emergency parachutes are used with
freebags (they
won't even have a bridle attach point), which allow
deployment even if
the pilot chute or bridle entangles with the body of
the jumper due to
an unstable opening. The same is not true of rounds,
which are thus
more prone to 'horseshoe' malfunctions. Picture what
that looks like -
if you really want to.

The Irvin EB** series were reputed to be the fastest
opening chutes in the world at one time and they certainly
use round canopies (I24). Maybe they still are, I
hope
so cos that is what I have.

The primary factor affecting the speed of opening (assuming
such
variables as airspeed, altitude, etc. are kept constant)
is the volume
of air required to inflate the canopy. Square canopies
need less air
to inflate, as they are smaller. The can be made smaller
since they
generate lift, not just drag. Because of this, squares
inflate much
quicker than rounds designed to carry the same loads
- so quickly in
fact that all modern squares (other than those used
for BASE jumping
from VERY low altitude - about 600 ft or less) are
equipped with
sliders to slow the opening to something only a little
faster than
rounds. Square sport canopies often have sliders that
slow the opening
enough to make it 'comfortable' but the emergency parachutes
have just
enough slider to keep you from breaking your back in
a terminal
velocity opening.

There are actually only two advantages to rounds.

The first is cost - old obsolete technology is always
cheaper. You can
pick up a serviceable round rig for a couple hundred
dollars US; a
square rig will be newer and more expensive.

The second is the reduced need for training. The square
parachute is a
wing. It must be flown and flared for a landing.
Further, for various
reasons I will be happy to go into if anyone is interested,
it doesn't
really fly and flare like a rigid wing. Finding yourself
under one
with 30 seconds to figure out its flight characteristics
and land it in
a suboptimal landing area is NOT the hot tip. Much
as I dislike rules,
I would still recommend a training jump or two for
anyone planning to
use a square rig without prior experience, as well
as briefing from
someone who understands both ram-air wing and rigid
wing aerodynamics
and can prepare you for the differences.

Michael