How low can you chop?

[bkoch 0]

Hey folks,

Just been thinking about something lately as I cross the thousand foot mark under canopy. What altitude is too low to cutaway--meaning, at what altitude, if I should have a problem like a collision or lines that break, or canopy collapse, should I just fire the reserve and not cutaway first?
I jump an RSL, but I know back up devices are not to be relied upon.
My personal thought was that under a thousand feet, if I should have a problem, I should just fire the reserve if the situation is unrecoverable. But someone told me this past weekend that if I have an RSL I could cutaway as low as 700 feet if I needed it.

What's your thoughts?
Brad

[billvon 2,464]

Realistically? If you cut away above 300 feet, have the RSL open your reserve, and everything goes perfectly - the reserve will probably be inflating or inflated at impact. A skyhook will open in even less time than that. Since things tend to not go perfectly, and it is nice to be able to do things like unstow your brakes before impact, 1000 feet is a more general never-cut-away-below number.

Whatever altitude you choose will depend on the situation. Did you just collide with someone, and your main is now shredded and providing no drag at all? Then cutting away at 300 feet might be a better idea than doing nothing or just dumping your reserve, especially with a skyhook. Do you have a lineover that you managed to miss until 500 feet? You may want to consider landing it (if it's controllable) or even doing a canopy transfer - pull the reserve handle, wait until the reserve clears the bag, then cut away. This doesn't always work since the reserve PC won't always extract the bag at canopy-flight speeds. If you're at 100 feet and your canopy rips nose to tail? Dumping the reserve might be a better idea.

[LawnDart21 0]

Another consideration is that your altimeter isn't giving you precise altitudes, especially below 1000ft. You could read 800ft and really be at 500ft or vice versa. +or- 500 feet from your reading altitude isn't totally unreasonable.

The best defense is to ensure to the best of your ability, you do not have to consider chopping below 1000ft, which requires opening at an appropriate height to allow time to deal with problems, and then to fly your canopy like your life depends on it (defensively, becuase it does).

Blue skies, Tom

--
My other ride is a RESERVE.

[stuartjl 0]

Good advice Bill. My impulse is to go to reserve under 1000ft irrespective of what is happening above unless the risk of entaglement is too great. This means possibly choosing to land a lineover (very dodgy)

[Amanduh 0]

Quote

Did you just collide with someone, and your main is now shredded and providing no drag at all? Then cutting away at 300 feet might be a better idea than doing nothing or just dumping your reserve, especially with a skyhook.

Are you serious? At 300 feet?

I would dump my reserve and get something out instead of taking the chance of having nothing.

Edited to reword: I would dump my reserve and get MORE out, instead of taking the chance of having nothing.

[JohnRich 4]

Quote

How low can you chop?

As low as you want.

But I think that what you really mean is; "How low can you chop and still live?

[Travman 6]

They showed us a video at our A licence course of a canopy collision when a guy was on final. Another pilot flew straight through his canopy and shredded it, he chopped - RSL deployed reserve and he had line stretch on impact.
Nasty stuff. Not sure how high they were, but he spent the rest of his life waiting for his reserve to come out.

[billvon 2,464]

>Are you serious? At 300 feet?

During rig testing I've seen reserves open in under 200 feet. Racer used to advertise that they would open in 64 feet, but I don't believe that.

>I would dump my reserve and get MORE out, instead of taking the chance
>of having nothing.

That's a perfectly valid decision, and it's what I tell my students i.e. never cut away below 1000 feet. That way, even if their altimeter is off, they take a few seconds to decide, and they misread the needle, they still won't be cutting away at 100 feet.

[mdowling 0]

To specifically answer your question: I cutaway at 600 feet after a canopy collision with no RSL and had a reserve at about 100 feet. It should be noted that the opening after such an event is subterminal and may take longer. I landed without injury in a clump of trees and walked away.

As for what's actually recommended -- I'd go with what Bill said.

[jose 0]

Damn, got video of that? Love to see it.

[Superman32 0]

That's some f'ed up shit

Inveniam Viam aut Faciam
I'm back biatches!

[GoatBoy 0]

I would stick to not performing a cut away below 1000 feet under any circumstances (if not higher). At that point just try to get as much fabric over your head as possible. Too many things can go wrong and you will have very little time to deal with it. If the reserve comes out clean you can do a canopy transfer, but I would rather have two balls of shit over my head than nothing.

Flying Hellfish #31
"I'm not allowed to talk about it till after the trial"
www.SkydiveTecumseh.com

[Frenchy68 0]

Quote

It should be noted that the opening after such an event is subterminal and may take longer.

Not to get confused: time is irrelevant, altitude is what matters. Deployment takes more time but burns less altitude at subterminal that at terminal.

"For once you have tasted Absinthe you will walk the earth with your eyes turned towards the gutter, for there you have been and there you will long to return."

[GaryP 0]

Frenchy68 hits it on the nose - "parachutes" (p/c, bridle, canopy, lines, risers) open over a given altitude - not time. With that said - it takes more altitude to get bottom-skin inflation when deployed at or near terminal than it does when deployed from low-speed (such as a chop).

The 1000' reference that a lot of ppl give is accounting for chopping, possible delay b4 reserve dump, RSL vs no RSL, need time to set up for landing, experience etc. Given all these variables you will commonly get this figure of 1000' quoted when you ask this question. It's a coverall and certainly has it's place in instruction as a generalization.

My opinion is, with some exceptions, that most reserve-setups have similar p/c and deployment specs and that you'll find most systems will give bottom-skin inflation at about 200' from the p/c leaving the jumper on a low speed deployment and about 300' from a p/c deployment at terminal. All reserves have to be configured for high speed deployment (bag, slider up, small p/c) and that's why the low-speed performance isn't that great (F'falling from 150' with BASE gear isn't that uncommon).

With that said you can add height for the variable needs such as setting up to land, etc. Also, note that you asked "How low can you chop?" and these figures don't take the chop or any delay into account, you gotta add that too. I wrote this today 'cause I think that the advice of 1000' is too high and may even work against you one day by preventing you carrying out a neccesary procedure because you've been scared into believing that if you chop under 1000' you'll die.

Just make sure you have a plan and drill yourself thouroughly. Think the jump all the way to the ground and not just to dump-time. Be on the ball as time thinking is a big waster of altitude. Someone somewhere said "Never let your canopy take you anywhere your brain hasn't already been" (or something like that).

Have fun - stay safe

g.
OzBASE86

"Altitude is birthright to any individual who seeks it"

.

[mjosparky 3]

Quote

Frenchy68 hits it on the nose - "parachutes" (p/c, bridle, canopy, lines, risers) open over a given altitude - not time.

If that is true why are TSO'd canopies test to a time standard with a distance standard as an alternative..

From AS-8015B

4.3.6 Functional Test (Normal Pack All Types): For all 4.3.6 tests the maximum allowable opening time for
parachute canopies with a maximum operating weight of 250 lb (113.4 kg) or less, is 3 s from the
moment of pack opening. For parachutes with a maximum operating weight of greater than 250 lb
(113.4 kg) the maximum allowable opening time shall be increased by 0.01 s for every pound of
maximum operating weight in excess of 250 lb (113.4 kg).

Sparky

My idea of a fair fight is clubbing baby seals

[BillyVance 34]

Quote

Damn, got video of that? Love to see it.

I think I saw it on a Michael McGowan video... or maybe it was a different incident. guy's canopy is hung up on another guy's leg. He cuts away low, too low, reserve was just about at line stretch when he hits, just below the crest of a low hill. Didn't survive that either.

"Mediocre people don't like high achievers, and high achievers don't like mediocre people." - SIX TIME National Champion coach Nick Saban

[GaryP 0]

Quote

If that is true why are TSO'd canopies test to a time standard with a distance standard as an alternative..

Well, it IS true. Both distance fallen and time taken are related to each other and either can be used as a standard of measure. This is only so when the airspeed is constant though. The reason they use the measure of TIME in AS-8015B is because that's the only unit that can readily be measured "in situ" for a falling canopy/jumper assy.

You can't measure the distance fallen as readily for that particular test but you can easily measure the time taken.

Also, the variable of what speed the jumper is deploying adds too much complexity to the test if figures were used for the distance fallen over different deployment speeds. The test needs a simple standard to measure deployment efficiancy.

THAT'S why they use time as a preferable unit in AB-8015B.

g.

"Altitude is birthright to any individual who seeks it"

.

[Frenchy68 0]

Quote

If that is true why are TSO'd canopies test to a time standard with a distance standard as an alternative..

From AS-8015B

4.3.6 Functional Test (Normal Pack All Types): For all 4.3.6 tests the maximum allowable opening time for
parachute canopies with a maximum operating weight of 250 lb (113.4 kg) or less, is 3 s from the
moment of pack opening. For parachutes with a maximum operating weight of greater than 250 lb
(113.4 kg) the maximum allowable opening time shall be increased by 0.01 s for every pound of
maximum operating weight in excess of 250 lb (113.4 kg).

This is an uneducated guess, but I'll give it a try:
Time is a uniform value. Whether you are falling at 40mph or 150mph, 1 second = 1 second. However, the vertical distance covered within that 1 second will vary depending on the fall rate. As GaryP mentioned, it is much easier to measure time than altitude, especially when falling at terminal.
As Billvon stated, chopping above 300ft with an RSL may have a positive result, as we are talking about sub-terminal deployment of the reserve. I doubt the chances are survival are any decent if going silver at 350ft while falling at terminal.

"For once you have tasted Absinthe you will walk the earth with your eyes turned towards the gutter, for there you have been and there you will long to return."

[j3zz 0]

Something to consider, what are you over.

Chopping really low over a building, may have far worse consequences than over a nice open field.

I figure I might chop as low as 500' over a clear landing area assume the PLF postion and hope for the best. This being if my main it totally wrecked.

In my opinion if I was to choose to just dump the reserve into the mess I would leave that till about 500ft assuming I was not about to pass out from a spin.

My guess and I mean guess, is that if you have a ball of washing deploy your reserve into it there is a time were it will create more drag before the 2 start to wrap each other nice and tight. Like I say this is a personal theory which I hope to never try.

So if you do choose to not chop below 1000 I would wait till a bit lower before dumping the reserve.

But that is just me ask an instructor.

"Now I know why the birds fly"
Hinton Skydivers

[mjosparky 3]

But distance can be used instead of time.

4.3.6 (Continued):
Alternatively altitude loss instead of time may be measured and the maximum allowable altitude loss
may be calculated as follows.
For all 4.3.6 tests the maximum allowable altitude loss for parachutes with a maximum operating
weight of 250 lb (113.4 kg) or less is 300 ft (91.5 m) from the altitude at pack opening. For parachutes
with a maximum operating weight of greater than 250 lb (113.4 kg) the maximum allowable altitude loss
shall be increased by 1 ft for every pound of maximum operating weight in excess of 250 lb (113.4 kg).
NOTE: Altitude loss measurements must be measured along a vertical trajectory only. However, the
deviation from the vertical produced by a gliding main parachute descending with a vertical
velocity of less than 20 FPS (6.1 m/s) shall be acceptable.

But 3 seconds is always going to be 3 seconds. 300 feet in relation to time can vary greatly.

Frenchy,

Any guess, educated or not is not a good idea in this sport. When in doubt, find out.
The 300 foot opening requirement is done with a cutaway form an open main and at terminal.

Sparky

My idea of a fair fight is clubbing baby seals

[Frenchy68 0]

Quote

Any guess, educated or not is not a good idea in this sport. When in doubt, find out.
The 300 foot opening requirement is done with a cutaway form an open main and at terminal.

Thanks for the info. Does it then mean that initiating reserve deployement at 400ft AGL while falling at terminal should result in the reserve being fully deployed about 100ft AGL? That's quite amazing.

"For once you have tasted Absinthe you will walk the earth with your eyes turned towards the gutter, for there you have been and there you will long to return."

[mjosparky 3]

Quote

Quote

Any guess, educated or not is not a good idea in this sport. When in doubt, find out.
The 300 foot opening requirement is done with a cutaway form an open main and at terminal.

Thanks for the info. Does it then mean that initiating reserve deployement at 400ft AGL while falling at terminal should result in the reserve being fully deployed about 100ft AGL? That's quite amazing.

You can try it if you want. If you are sharp enough to clear the pin exactly at 400, you might might make it. When I have been the one doing the live jumps for a TSO I try to do them at a higher altitude. It give the video jumper a little more room to open after filming my deployment.

Now go back and read all the posts and you will see that the most common standard that is tested to is 3 seconds.

Sparky

My idea of a fair fight is clubbing baby seals

[Frenchy68 0]

Quote

You can try it if you want.

I wasn't trying to be a smart ass, and apologize if my post came accross as such. I am truly amazed that a reserve deploys this quickly at terminal. Somewhat a comforting thought.

"For once you have tasted Absinthe you will walk the earth with your eyes turned towards the gutter, for there you have been and there you will long to return."

[mjosparky 3]

Quote

Quote

You can try it if you want.

I wasn't trying to be a smart ass, and apologize if my post came accross as such. I am truly amazed that a reserve deploys this quickly at terminal. Somewhat a comforting thought.

No problem.

It also has to open in 4 seconds at 60 KEAS with 3 line twist packed in it. Your reserve is a pretty neat piece of equipment. But its worthless if not pulled.

Sparky

My idea of a fair fight is clubbing baby seals

[tbrown 26]

Mike, about 20 or so years ago Dave Schulz had a bunch of "one thing leads to another" happen to him, with the net effect of his having a bagloc at 500 ft. He peeled and punched both handles simultaneously and had about a 5 second reserve ride under his old Pioneer 22 ft round. This was definitely a high speed malfunction and there was no RSL, or Cypres. Square reserves are supposed to open faster than the old rounds. So his experience may help to answer the question, but I assure you he most certainly didn't think anyone else should try it, he was very lucky to come out of it alive.

Your humble servant.....Professor Gravity !