0
jjudd

Canopy Collapse

Recommended Posts

We can't always see dust devils and erratic winds that cause our canopies to collapse. Sometimes we can. With the recent canopy collapse incident in california I'd like to use this post for everyone to share any near misses they have had and discuss how they reacted during such incidents to expand the knowledge base of our all of our jumpers especially newer jumpers. As we all know its a possible risk that we assume but 90% of the time the weather is telling us that these events may happen, Ie radical changes in winds and direction of the winds, and relative humidity. For the times it doesn't hopefully we can gain some knowledge.

Personally Ive only had one partial collapse and that was in a dust devil but well before approach to final. I was flying in half brakes back from a long spot and as soon as it happened i slowly let up the toggles after a 180ish turn to the right I regained stabilty and the jump was unremarkable after.

Below is a url to a collapse on approach to final from youtube. The pilot is a bit low and coming out on her/his toggles when the collapse happens. My feeling through research books and videos is that the canopy is much more prone to collapse when already flying in a low speed where pressure in the cells is much lower than at full flight. Though it can still happen at full flight the chances are much less likely. Just a reminder as to why we should be able to fly our canopies at full speed while landing as well as in all other conditions when flying before downsizing

http://www.youtube.com/watch?v=DfK5OuurnpY

Share this post


Link to post
Share on other sites
That was fatal. It happened at the Ranch NY a few years ago during a pond swooping competition. I was doing tandems that day, Some people disagreed but I thought it was kinda bumpy and wouldn't want to fun jump in those conditions. Wind was from the south which was coming over the trees toward the pond, probably creating rotors.

Share this post


Link to post
Share on other sites
Aside from unnecessarily using a fatality video to 'prove' a point...I'm not so sure the advice given is correct in all situations.

It's been my experience, at least on the canopies I jump NOT to be in full speed flight when encountering a rotor or shear.










~ If you choke a Smurf, what color does it turn? ~

Share this post


Link to post
Share on other sites
I have never experienced a collapse, partial or otherwise. This is partly due to the fact that I am very cautious about jumping in high or gusty winds. I have had the feeling of "I wish I was on the ground" and I don't want it again.

The canopy education I have had/read all agrees that full flight is the most stable flight mode for turbulence for most modern canopies. Brian Germain recommends just taking up the slack in the brake lines to be ready to give a quick stab of brakes to put more stability back into the system by increasing line tension/wingloading should the canopy start to collapse.
"The ground does not care who you are. It will always be tougher than the human behind the controls."

~ CanuckInUSA

Share this post


Link to post
Share on other sites
First off i'm not a dickhead. I sent you a PM today. Id like to call you a bad name but I wont because its not my standard to do so. Im not on dropzone 24 7 like yourself. And I sent you a kind reply before you posted this which I found after replying to your pm as thats what was what I saw on my account first. I am unable to edit it. Have a moderator remove the link or if you know how to remove it let me know. Its one of the primary videos on youtube under canopy collapse anyhow. Like I said I was unaware it was a fatal incident and would gladly remove the link.

Ive seen you jump to conclusions like this with others, your assuming I knew this, really? If you PM someone give them at least 24 hours to respond and dont assume unless you know someone. It hasnt even been barely 12 hours since I posted this.

I feel very terrible for the family. I have seen alot of death in my job as its part of it and Id think you should know id be the first not to post something unless its valuable for teaching. If you were to have an emergency id treat you just like i would treat a family member even if you were my worst enemy as a respect to you and your family. Do no harm is the moto in paramedicine and firefighting. Try doing the same for others. My ego is aside and I hope you can appologize like a real man in a pm not on here.

You are really a piece of work and I cant wait to meet you someday to shake your hand and tell you that. Thats for all the new people that ive seen you obliterate on forums vs educate properly, there is a time and a place for that, aka a pm or in person away form their peers not on the forums. Theres always time you change views and attitudes. Everyone is constantly evaluating eachother. Ive never met you who do you think you are? Your real tough to everyone online. All i started this post for was for like you said to discuss canoply collapses seriously. Video is only a reference. now like I said in the PM if you know how to remove the link I will gladly. Feel Free to tell me how vs assume and be a hipocrit

Share this post


Link to post
Share on other sites
Quote

I have never experienced a collapse, partial or otherwise. This is partly due to the fact that I am very cautious about jumping in high or gusty winds. I have had the feeling of "I wish I was on the ground" and I don't want it again.

The canopy education I have had/read all agrees that full flight is the most stable flight mode for turbulence for most modern canopies. Brian Germain recommends just taking up the slack in the brake lines to be ready to give a quick stab of brakes to put more stability back into the system by increasing line tension/wingloading should the canopy start to collapse.




And I would disagree with him on that, having done literally hundreds of demos into tight areas with buildings, trees, stadium walls etc. I've found that slightly more brakes than just taking up the slack works better in that you hit the turbulence at a bit slower speed and already having about 1/4 brakes on you can adjust by letting up on the opposite brake as opposed to pulling down on one, which if done too aggressively can cause more problems.

In addition, if the canopy collapses and you need to pump it, you already have 'some' feel through the brake lines how fast & hard you need to do that.

I don't know if that is advisable on a highly loaded elliptical, but on my reasonably loaded canopies it has always worked.

The worse spinning rotor I've ever encountered was flying through the St. Louis Arch, the guys that went through in full flight had a much worse time than those of us in 1/4 brakes.










~ If you choke a Smurf, what color does it turn? ~

Share this post


Link to post
Share on other sites
Thanks for sharing your experience. Please share why you feel in partial brakes it was smoother?

I am not standing by one way as being right as every canopy is different under different loadings and sizes in each condition. And im not convinced that full flight is 100% the best option though most material suggests so and that has worked for me

Share this post


Link to post
Share on other sites
>I've found that slightly more brakes than just taking up the slack works better . . .

What size/aspect ratio canopy was that? I've found that, in general, larger/steeper/wider canopies (i.e. 7 cell accuracy canopies) do better in turbulence with more brakes, although all canopies seem to benefit from _slight_ application of brakes (i.e. enough to take tension out of the brake lines.) Whether that's due to actual deflection of the tail or just allowing that additional feel I'm not sure of.

Share this post


Link to post
Share on other sites
Quote

>I've found that slightly more brakes than just taking up the slack works better . . .

What size/aspect ratio canopy was that? I've found that, in general, larger/steeper/wider canopies (i.e. 7 cell accuracy canopies) do better in turbulence with more brakes, although all canopies seem to benefit from _slight_ application of brakes (i.e. enough to take tension out of the brake lines.) Whether that's due to actual deflection of the tail or just allowing that additional feel I'm not sure of.




I would say with a 7 cell accuracy canopy there's no question it's more stable in brakes...to answer your question my Z-po 190's are 8.5 X 23 and are what I have a lot of experience on doing demos in the past 10 years. Loaded at about 1.3:1

Again, maybe it's just me...but I like being able to just let up on the side that's diving or rolling to get it flying again, instead of trying to counter steer with the opposite toggle. And in severe turbulence being able to do both seems to correct the wing that much faster.










~ If you choke a Smurf, what color does it turn? ~

Share this post


Link to post
Share on other sites
in reply to "My feeling through research books and videos is that the canopy is much more prone to collapse when already flying in a low speed where pressure in the cells is much lower than at full flight. Though it can still happen at full flight the chances are much less likely. Just a reminder as to why we should be able to fly our canopies at full speed while landing as well as in all other conditions when flying before downsizing "
......................................

Sure highly loaded canopies flying at high speed cut through turbulence quicker than slower canopies.
However close to the ground the higher speed adds its own dangers.

After watching and flying my share of different canopies for turbulent conditions I'd pick my circa 1990 7cell F111 Maverick over any canopy I've jumped.
While I happily landed at slowish speeds in all sorts of conditions my fellow ZP jumpers were breaking bones left, right and centre....still are.
I couldn't stop them, they thought fast elliptical ZP was better than good old dependable square F111. of course they weren't perfect but were they better?

A partial collapse on a biggish canopy doesn't dump you into the ground as quick or as hard as a partial collapse on a highly loaded canopy.
Your highly loaded ZP pockrock might cut through turbulence quicker only to put you straight into the ground ...nice and fastly.

Share this post


Link to post
Share on other sites
>Sure highly loaded canopies flying at high speed cut through turbulence
>quicker than slower canopies.

"Cutting through turbulence" is a misnomer. There's no "cutting" involved. Aircraft slow down during turbulence to avoid structural failure; a pilot that sped up to "cut through" upcoming severe turbulence would likely not survive the attempt.

Turbulence is moving air. The one advantage that heavily loaded canopies have is that they are faster, and thus are slightly more immune to wind shears that would otherwise cause a stall due to loss of airspeed. That comes at a price; there's much less margin for error when a collapse does come (which they still do.)

Share this post


Link to post
Share on other sites
I had a full canopy collapse of my new Pilot the very next jump after I got my A-License. Was my 60th jump or so. This happened July 19th, 2006 at Perris Valley. My instructor said I went straight down from about 30 feet but he said I did everything right. Had a very bruised tail bone and fracture of a vertebrae. It was very hot that day and was landing in the student area. Suspected dust devil. Went straight down.

I went back up about 6 weeks later after the doctor's ok and have not jumped since 2006. Not sure whether to go back or not. Used to be financial, but now that I am nearly 40, just dunno any more. Stuck at 100 jumps and want to be a POPS jumper on my 40th in August. Just not ready yet I suppose.

David

Share this post


Link to post
Share on other sites
Quote


The canopy education I have had/read all agrees that full flight is the most stable flight mode for turbulence for most modern canopies.



We can fix that by broadening your reading list:

http://www.jumpshack.com/default.asp?CategoryID=TECH&PageID=Turbulence&SortBy=DATE_D
The choices we make have consequences, for us & for others!

Share this post


Link to post
Share on other sites
Quote

Quote


The canopy education I have had/read all agrees that full flight is the most stable flight mode for turbulence for most modern canopies.



We can fix that by broadening your reading list:

http://www.jumpshack.com/default.asp?CategoryID=TECH&PageID=Turbulence&SortBy=DATE_D



Very interesting read, I always knew THAT it worked...now I know WHY.










~ If you choke a Smurf, what color does it turn? ~

Share this post


Link to post
Share on other sites
Quote


Sorry, but yuk! That's not a good document.

I agree that we don't have an absolutely clear consensus on what the best practices are, even if we have concepts that are reasonable to follow.

But Sherman's document that is quoted has serious errors.

Some of the aerodynamics is correct, but things like the following are wrong:

Quote

“The moment of greatest lift on an airfoil is just prior to an impending stall”, which is taught to every student pilot, tells us that the boundary layer gets stronger as we approach a stall. Why is this? It is because the air flowing over the top must go further and necessarily faster to meet with the air passing on the other side of the wing. Therefore the pressure differential is greater, and the boundary layer is stronger, making it harder to blow off.



It is totally wrong to say that the air on top needs to be faster to meet the air below. Molecules next to each other at the nose of an airfoil don't meet up again at the tail.

For a plane slowing towards the stall in level flight, the lift stays essentially the same. The lift coefficient, however, increases. Sherman misses that distinction, muddying his explanation.

The pressure difference top to bottom on the airfoil has nothing directly to do with the strength of the boundary layer on top of the airfoil. That varies from nose to tail.

And the boundary layer is in no way "strong" close to the stall -- that's where the airflow is about to separate from the top of the airfoil, decreasing lift, increasing drag, and creating a sharp nose down pitch moment -- you know, a stall.

And it isn't the boundary layer itself that "blows off" or separates from the airfoil in a stall. It's the division of the airflow between the boundary layer and faster moving air that moves away from the airfoil. It's a very imprecise use of the term.

So with his amateur understanding of aerodynamics the first section of the document isn't of much use. As for later parts of the document dealing with flying in turbulence:


Overall, Sherman recommends flying near the brakes-set position in turbulence. I think that is too deep on typical canopies, where the brake setting might be 1/3rd brakes (Clearly brake settings vary a lot by canopy, from zero brakes to the edge of stall, but most are, what, maybe in the 1/4 to 1/3 brake range these days.)

If there is debate, it should be between flying at say "1/4 brakes" and flying with "zero brakes except all slack taken out of the lines and just a little pressure applied to maintain a feel for the brakes".

And there can be debates about how flying in one way might reduce the chance of a collapse (e.g., full speed, or in a turn with added g loading), but if there is a partial collapse, such flight may make it more difficult to recover in the altitude available. Tradeoffs!

John Sherman's idea of brake set position may not be a bad one for actually recovering from a collapse or stall, but even then one could debate between that and a traditional stall recovery position with brakes not far above the stall point.

Share this post


Link to post
Share on other sites
Quote

Quote


The canopy education I have had/read all agrees that full flight is the most stable flight mode for turbulence for most modern canopies.



We can fix that by broadening your reading list:

http://www.jumpshack.com/default.asp?CategoryID=TCH&PageID=Turbulence&SortBy=DATE_D



"The air going over the top is accelerated, ‘cause it has to go further, to keep up with the air going under the bottom" is simply INCORRECT.
...

The only sure way to survive a canopy collision is not to have one.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

0