emergency chute

What is best: a round or square chute? Do they differ in time to open? Are
previous experience or training jumps with a square chute mandatory? Is a
static line better - if so why?
(we have a packer at our club that has recommended square chutes, but
apparently two training jumps are mandatory - we are based in South Africa)

Sven
EY

I don't think you will find that there are any emergency
prachutes with square canopies, they are all round.
The criteria for emergency parachutes is that they
should open whatever the attitude of the person using
them. 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.
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.




At 20:30 05 April 2005, Sven Olivier wrote:
What is best: a round or square chute? Do they differ
in time to open? Are
previous experience or training jumps with a square
chute mandatory? Is a
static line better - if so why?
(we have a packer at our club that has recommended
square chutes, but
apparently two training jumps are mandatory - we are
based in South Africa)

Sven
EY

Don Johnstone wrote:
I don't think you will find that there are any emergency
prachutes with square canopies, they are all round.

I know a number of glider pilots who have them, all experienced
skydivers. I believe they use square reserve canopies, which apparently
open every bit as quickly as round ones. When asked, the general
response is that they feel safer under a square 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

Michael, I get your point however like many others
I hope that I will never have to use my parachute and
if I do I will take my chances. The only thing that
I want from it is that it works so how do I judge that?
I look at one of the most sucessful canopies there
is and think to myself, OK that works I want that one.
In my case it is the same canopy that is pressed into
the headbox of every MB ejector seat, an Irvin conical,
an identical canopy to the one in my pack. I am sure
that other canopies are just as good but to my way
of thinking, as I never intend to test it I will go
with something that will save my life even though I
am stupid enough not to get any training in it's use.
How do I know the canopy works, take a look at this.

http://www.joe-ks.com/Multi_Media/HarrierEjection.htm

The pilot was a tad unlucky, he broke his ankle when
he landed on his aircraft. I know that the actions
of the seat contribute but just look at the rate of
descent when the seat clears the cockpit. The seat
was actually outside it's required sucess envelope
but still the canopy deployed and saved the pilots
life.

At 19:30 07 April 2005, Michael wrote:
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