emergency chute

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

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

I'd consider installing a ballastic parachute and riding the damaged
glider to the ground surrounded by the cockpit.

Charlie "Lite"

I'd consider installing a ballastic parachute and riding the damaged
glider to the ground surrounded by the cockpit.

Charlie "Lite"

Thanks for that.

You're welcome.

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.

If by that you mean that you won't train to use your emergency
equipment, then you are correct. Stick with the round. Just don't be
surprised if it lands you in the hospital. Remember - those maximum
loadings are based on a fit man in his 20's wearing boots with ankle
support. For a middle aged man wearing tennis shoes, they really ought
to be reduced by 30% or so. Not so the weights on squares - they are,
if anything, conservative if you know how to land one.

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. :-)

As opposed to the spectacular good sense exhibited by those who fly
airplanes that don't even have engines
Glass houses, stones, etc.

Michael

Michael wrote:

If by that you mean that you won't train to use your emergency
equipment, then you are correct. Stick with the round. Just don't be
surprised if it lands you in the hospital. Remember - those maximum
loadings are based on a fit man in his 20's wearing boots with ankle
support. For a middle aged man wearing tennis shoes, they really ought
to be reduced by 30% or so.

I personally know two pilots who had to jump. One broke a leg on
landing, the other sprayed an ankle. But believe it or not: Neither of
them complained.

Stefan

I personally know two pilots who had to jump. One broke a leg on
landing, the other sprayed an ankle.

My informal survey suggests that about a quarter of those who make
emergency bailouts on round parachutes go to the hospital afterwards,
so I'm not surprised. I've never heard of anyone bailing out on a
square parachute and getting hurt, but that doesn't mean much because
(a) they are still new, expensive, and relatively rare and (b) are
generally used by trained parachutists (everyone I know who uses one at
least went through some ground school and made a training jump) so how
much of this is gear and how much is training is hard to determine.

But believe it or not: Neither of them complained.

It's a matter of perspective. If a power pilot has to land off airport
and he walks away, even needing stitches, he feels great about the
experience because it's something he will do only in a dire emergency,
and probably never. If a glider pilot walks away from an off airport
landing with a trashed aircraft and stitches, he feels it was a pretty
bad outcome, and wonders what he should have done differently. This is
more of the same.

Sport parachute jumpers pretty much accept that they will eventually
use that emergency parachute they wear as a backup. Therefore, they
expect a certain level of performance. That's why when they wear a
bailout rig, they want a square. Glider pilots don't see it that way.

It's not right or wrong. It's your choice to accept an emergency
parachute that has a high probability of putting you in the hospital if
you use it. I simply feel it should be an informed choice.

Michael

Michael wrote:

My informal survey suggests that about a
quarter of those who make emergency
bailouts on round parachutes go to
the hospital afterwards....

It's your choice to accept an emergency
parachute that has a high probability of
putting you in the hospital if you use it.

One in four is no kind of "probability" at all, let alone a high one.

I'd be much more interested in seeing even an informal analysis of
unsuccessful attempts to bail out.


Jack

Jack wrote:
One in four is no kind of "probability" at all, let alone a high one.

Actuqally, it's 3 of 11. But that's not exactly a statistical
powerhouse either. That's why I said "informal survey suggests" rather
than "study shows."

I'd be much more interested in seeing even an informal analysis of
unsuccessful attempts to bail out.

The attempts were not unsuccessful. These people all bailed out and
saved their lives. The injuries were sustained on landing. They were
not life-threatening. In every case, the parachute loading was more
than I would recommend for a middle aged person wearing shoes with no
ankle protection, and the training was less than what I would recommend
for anyone (none, actually). But that was the case for the other 8 as
well. They got by with bumps and bruises.

I think the informal analysis reads like this:

Round parachute loadings are based on the old military tables. These
presuppose several factors, none of which are true for the average
glider pilot bailing out:
Healthy, strong, conditioned soldiers, usually in their 20's.
Jump boots providing ankle protection.
Very intense, very regular training in parachute landing falls.

Maximum allowable TSO loadings are even higher - they're based on the
ability to sustain opening shock at maximum altitude/airspeed, and
descent rate doesn't figure into it at all.

For the average middle aged (or older) glider pilot wearing typical
soaring footwear, using a round parachute at anything close to the
manufacturer's recommended maximum loading is asking for a landing
injury. That weight should be derated by at least 30%. Note that the
weight includes the weight of the rig.

For those who are light in weight, a 26 or 28 ft diameter canopy is
adequate. Round emergency parachutes are not made in sizes larger than
28 ft. In fact, I wouldn't know where to get a 28' rig anymore. For
those who are over 200 lbs (including the rig), there are no
appropriately sized round rigs. Their options include using a reserve
that is likely to put them in the hospital, or getting a square rig and
the training required to use it.

Michael

Jack wrote:

Michael wrote:

My informal survey suggests that about a

quarter of those who make emergency
bailouts on round parachutes go to
the hospital afterwards....

It's your choice to accept an emergency
parachute that has a high probability of

putting you in the hospital if you use it.

One in four is no kind of "probability" at all, let alone a high one.

I'd be much more interested in seeing even an informal analysis of
unsuccessful attempts to bail out.

I think this is the bigger problem. Those that don't get out of the
glider usually die. Once most pilots have Roeger hooks on their gliders
and the muscle strength to lift themselves out of the cockpit easily,
then it might be worthwhile trying to minimize the landing injuries.

Even better is to avoid the collision in the first place. The Europeans
now have an additional choice beyond "see and avoid": the "Flight Alarm"
device from www.flarm.com. Over 450 of these devices have been
delivered, and 2000 more are scheduled for delivery this year.

However, if a couple of jumps appeal to a pilot, it sounds like learning
to use a square reserve would be enjoyable and, in addition, provide
some slight additional safety for soaring.

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA