Why did my chute collapse?

[coyote-243]

In April, then again in May I had an incident that I have not yet got satisfactory answers for. I am not a new pilot. I have a BFI and over 700 hours flight time. I would appreciate any experienced advice. I’ll try not to make this to long but give you adequate information.
I purchased a used Six Chuter SR5xp about five years ago. It didn’t have a chute so I bought a new Apco 500 Mark IV/II. It was manufactured in 2002. I flew it over 700 hours and it performed flawless. I’d sometimes get caught in wind gusts or rotors down wind of structures. It was always fully inflated and solid. The chute was starting to look faded so I wanted to replace it with the same make and model of chute. I found an Apco 500 Mark IV with about 15 hours that looked new, so I purchased it. I noticed the steering lines were attached six inches in from the trailing edge where my first chute they were attach on the trailing edge. I didn’t notice until after my incident that it was manufactured in 2000 even though it was still labeled a Mark IV. Since then I looked at a friend’s 1999 Apco IV and it too has the lines attached 6 inches in from the edge. In the meantime I also purchased a Six Chuter Legend.
All my flying is from 6500 to 8500 feet above sea level, and at less than 300 feet above the ground. Yes, I know that is not as safe, but I get nervous much higher.
In April I was using the “new” 2000 chute on the SR5. It was in the evening and the air was unstable. The temperature was about 55 F and the wind was blowing about 5 mph on the ground, 10 mph in the air. It was suppose to calm down as the evening progressed. I flew about 45 minutes and was about 100 feet above the ground. There was a low ridge about 1000 yards in front of me, up wind. I made a S maneuver, turning to my left and then back to the right. It was not a sharp maneuver, but as I straightened out it felt like all the air came out of my chute and dropped my straight to the ground. The plane tipped nose down and impacted on the sloping edge of a sandy wash and rolled forward. The plane took all the impact and damage and I walked away. When I felt the chute collapse I tried to pump the steering tubes like you do to inflate the corners of your chute before take off, but there was no tension on the steering lines. They just flopped forward. I also gave it full throttle thinking that would help, it didn’t. Later I realize it was probably the wrong thing to do because it would have increased the chute angle and reduced the chance of reinflation. However I don’t think I could have done much to recover at just 100 feet. A friend was watching and he said it looked as if the chute lost the air out of it and dropped me straight down. My impact marks showed no forward landing tracks. The chute tangled in the top of a 12 feet tree so I had to climb up it to untangle. At that time there was no felt breeze.
I called everyone I knew that might give me some answers. Their main answer was they never heard of such a thing and it would probably never happen again. Some also said that maybe I just flew into an unexplainable pocket of “no air”. I took reassurance in their comments and figured it would never happen again.
I put the same almost new chute on my Six Chuter Legend. I made about four very nervous flights and every thing seemed fine. Then about the end of May it happened again. I was flying an area that had about 60 large wind mills that take a 4 mph breeze to turn them. At the time of the incident they were still. It was early in the morning, clear skies, 45 degrees, and an elevation of 7200 feet. I was flying along a hillside that was about 400 feet tall at a 45 degree angle. I was about 2/3 the way up the slope and 100 feet above the ground. I wanted to go back the other way so I turned out away from the slope to my left then turned to my right toward the slope. It was not an extreme turn. Just as I was about out of the turn my chute did the same thing as before. It was just like the air went out of the chute and dropped me straight to the ground. Again someone was watching and that is what they also saw. This time I didn’t walk away. I got a helicopter ride and a $200,000 doctor bill. Thank goodness for insurance.
Here are some of my thoughts about what may have contributed to the two collapses. Keep in mind the 2002 chute is the one I wore out, and the “new” chute with 20 hours on it is the 2000 chute.

1. The unstable air may have contributed to the first collapse, but I don’t think so on the second.
2. When I trimmed my 2002 chute I would have just a little slack in the steering lines. With the “new” 2000 chute I took the slack out, then shorten it one more inch at the attachment. It would create a very small wrinkle on the chute.
3. Both planes have compound steering. However I had compound steering with my 2002 chute also.
4. I was flying at a high elevation.
5. Both times the chute collapsed as (I think I did) I came back into my prop-wash at an angle.
6. The “new” 2000 chute’s steering lines attached 6 inches in from the trailing edge.
7. The 2000 chute passed the canopy inspection but not the wire line test.

The only variable I can see is the 2000 chute and the trim was a little tighter. I don’t think the trim was much of a factor because I have friends that set their trim much tighter. I have also talked to pilots that collapsed their chutes intentionally. They had to push the steering tubes all the way out, reach up as far as they could and pull the steering lines down and across their chest to get the chute to collapse.
I think the “new” 2000 chute was the biggest factor and variable because the other items of concern: air conditions, turning, crossing prop wash, elevation and compound steering I had used or done it many times with my 2002 chute.
A couple of months ago I sent the “new” 2000 chute in for inspection. It passed the canopy tests with flying colors. It was like new. So I asked for a wire line test, which is to measure and see if the cords are the right length. Here are the results:

“We have performed a 'wire' measurement of the lines on the canopy, under 5KG of pressure. This means that we measured the line from the metal link to the attachment point. Using the line specifications from PW.500.MK4.BC, we determined that most of the lines are short, some as much as 45mm. I have included the results below. For example, the A-2 line is 35mm short; The A2 line is 30mm short; The B6 line is 10mm short, etc.”
A B C D
() -2 -35 -15 -30 -25
() 2 -30 -20 -20 -20
() 6 -25 -10 -15 -20
() 10 -25 -10 10 10
() 14 -30 -15 -20 -20
() 18 -35 -20 -20 -20
() 22 -40 -25 -20 -20
() ST -45 -15 -25 -20

I don’t know if the lines being out of specs by less than 2 inches could have caused the chute failure. Maybe with the other factors it was the straw that broke the camel's back. If you have any insights about this please let me know.

Something I learned that I should pass on is sometimes companies outside the good old USA don’t stand behind their product like I think they should. I’ve never considered trying to sue Apco for compensation because the PPC dealer that found this chute for me is a good friend and I didn’t want to cause him any problems. However I wanted some answers from Apco. I’ve tried to call Apco, and I emailed them a number of times, but they will not answer. I talked to one of Apco’s larger distributors and he was not surprised. He said don’t think for a minute they will give you answers and definitely not compensate. He said he’d be very shocked if they would even consider exchanging the chute for a new one.

[mignazito]

Wake turbulence.

Marty

[Weaver]

There was a low ridge about 1000 yards in front of me, up wind.

http://www.paragliding.gr/cd-rom/pictures/meteo-rotor.jpg

PPG frontal closure because of a ridge up wind : http://www.mission-montblanc.be/video/frontstall.wmv

Paul

[coyote-243]

I am really appreciating the replies about my chute collapsing because it is something I've thought through my mind over and over for about 6 months. There are a number of possibilities, but the one fact that keeps coming back is why didn't my first chute collapse when it was in the same situations or even more severe circumstances. I have easily crossed my prop wash thousands of times and have friends that have more than that without a collapse. I have also got caught in sever rotors. Once I tried to cross a steep ridge and was not high enough and got stopped at a very rough 0 mph air speed on top. When it got to rough I turned out. The wind and rotor caught me pushing the chute down and away severe enough and long enough that my engine sucked air off the bottom of the tank and died. Then it pendulumed up right in time to do a clean dead stick landing. The chute never came close to collapsing. Then to have this second chute collapse twice in less than 20 hours of flight in much milder conditions.

[Skypilot]

Have you checked (compared) the angle of attack of the two wings? If you reduce the angle of attack the wing will fly faster (higher airspeed) but it will make it more succeptable to turblence collapsing the leading edge resulting in deflation of the wing (at least partially). Extra links are sometimes added to the rear risers to increase the airspeed but it also makes the wing more suceptable to collapses. Or it may be that the manufacturer set the angle different to make it go faster. If I were you I would measure every thing on both wings and try to find what is different between them. I think your altitude probably makes recovery a lot slower than it would be at lower altitudes.

[kilowatt]

Coyote,

Wake turbulence could certainly be suspect here. Your aircraft is a high drag design and and one should never underestimate the amount of air being displaced and moved around by our thick, high drag and slow flying wings. Your turn (increased angle of attack) into the wake turbulence at high altitude (thinner air) could spell a recipe for problems.

It could also be mechanical turbulence. Paul's picture illustrates this turbulence very well. It is caused when large air masses encounter the contours or objects along the earth.

If you're flying over an area that is significantly lower in elevation than the windward side of a hill, then you can also expect large downdrafts to occur as the airmass heats up on the windward side, blows over the top; then cools from atmospheric conditions and moves down the slope to settle in the lower area of land. This would be similar to pouring a huge amount of cooler water down the hill next to your flying area. This condition may also occur during very mild flying conditions.

Remember, I'm talking about HUGE masses of air. If conditions are just right and you're flying close to that ridge, you can easily be caught in this draft.

Hazard avoidance if the key to a safe flight in these areas.

I also recommend you send the chute in to a reputable manufacturer approved inspection station such as Mojo's for a total inspection. Place some correspondence in your package indicating your past experience and that you would like to have the lines inspected for stretching.

Don't fly that wing until you've done some more research and had the wing inspected.

Check those risers out, too. You're looking for anything that may have changed the incidence of the wing from what it is designed to fly at.

Please keep us informed of your findings. Your information is vital and very important to the safety of our sport.

One question: Is the Mark IV the hybrid wing?

Kilowatt

[coyote-243]

The Apco Mark IV is not a hybrid. The measurements and quote is from Mojos.

[mignazito]

Well if it isn't what everyone is suggesting, it's rigged just like your old wing, nothing what so ever has changed except the wing and your old wing went thru the "same or worse", we can only conclude by deduction that you have a bad wing for some unfathomable reason.

Marty

[MikeRevier]

Apco went through several versions of the "standard" 500 S.F. wing. I have flown three different versions, all had different flying traits (same PPC). My favorite was the Mark II, followed by the Mark IV/II, then the ill handling Mark III (I think, it may have been Mark I). One of the differences between this wings (other than the steering line locations) is line lengths. This would explain your differences in your lines from the manual.

Flying a lighter 2-place plane (or solo) with light wing loading (500sf or larger) is really asking for stall problems in less than perfect conditions you would normally see at the low altitude you prefer to fly at. Several things you can do to help, Add weight (100 lbs = 2 1/2 mph), add an extra C/D link (2-3 MPH) buy an elliptical wing for higher wing loading (trimmed correctly). Bottom line is you MUST increase your air speed to allow for turblance (air speed changes) to maintain internal air pressure of your wing.

Don't try to over analyze your wing differences ,as it is not that unusal to see different flight characteristics, from wing to wing. In this case, just give the wing the trim adjustments it is asking for (more air speed).

Mike Revier

[mignazito]

Mike:

Do you have anything more specific other than "handled differently"? For me one late model 500 is about like the other with only very small differences noted. e.g. The old Apcos were slow to inflate at the wing tips and that was a definite noticable attribute.

Your pretty much right on with the ellips as to turbulence, etc. One thing of note is very high turn rates for ellips. At full normal deflection mine will turn 360 degrees in 6 seconds.

I have not flown a square other than on occassion in some 150-200 hours now. What I do remember I would just as soon forget. "Ponderous" would be an apt recallection.

Marty

[MikeRevier]

Marty,

I did not see a big difference in kiting on the "standard" 500 Apco's. The Apco Hybrid on the other hand is one of the worst, with lazy end cell inflation and staggering as it comes overhead. The difference I see is, in-flight steering response (Mark II was best), cruise RPM's (varied by about 200RPM's) , air speed (that can greatly influence steering response). The best Apco actually felt more like an elliptical (in smooth air only) than the other Apco's. I believe the wing cut on the Mark IV is very similar to the Mark II, but the original Mark IV was not as good a flyer and Apco went to the line set off the Mark II, hence the Apco Model Mark IV/II.

Too many pilots have the idea very slow flight in a PPC is safe, and that is far from true. If you expect your parachute to act like a wing you must have adequate air speed (under 30mph in a dual PPC can be trouble) to maintain internal air pressure (wing shape) and correct air flow over the top of the wing. Take that away and your wing turns into a true parachute and you will need more than double your square footage for a proper descent. The side benefit I have noticed is, improved steering response with the airspeed increase on any wing. This has been most notable with P.D. wings. Adding the extra link on the C/D line set will improve several things , such as easier kiting, but it can cost a slight decrease in climb (usually less than 50 FPM) and 100-200 RPM's in cruise.



Mike Revier

[mignazito]

Mike:

As you say: Too many pilots have the idea very slow flight in a PPC is safe, and that is far from true. If you expect your parachute to act like a wing you must have adequate air speed (under 30mph in a dual PPC can be trouble) to maintain internal air pressure (wing shape) and correct air flow over the top of the wing.

Though pitot pressure (internal wing pressure) varies as the square of speed and higher speed does result in a more rigid wing, there is more to the story. As fighter pilots know well, ENERGY (kinetic energy or energy of motion) is a major issue in flight. Energy with mass being fixed (same gross weight) comes with speed. This is one of the reasons that ellips have such strong flare authority. Higher speed means you have more energy to trade for altitude in the landing round out. Of course the ellips also have more control authority due to larger control surface area, but that is only part of the story. More kinetic energy is the main issue.

Higher speed also gives more control authority in general due to it's increased effect on control surfaces.

Obviously there are limits. Very high speeds introduce a whole new set of problems, but in the case of PPCs slightly higher speeds actually have a beneficial effect. e.g. I love to fly me E280 at 900 lbs or so. Handling is crisp and clean, turbulence is absorbed almost unnoticed and landings are smooth and even though speed is high. You can also cover some ground in a hurry. Great for cross country flight. At 900 lbs I'm into the low to mid 40 mph range with this wing.

[coyote-243]

Mike and Marty:
I really appreciate your information. I don’t have the technical knowledge you guys have, but I am learning a lot from your conversation.
When I was first introduced to powered parachutes I was lead to believe the chutes would not stall or collapse. Now I’m starting to get a much different picture. My type of flying here in Wyoming is low level. I fly along fences looking for damage or open gates. I check for stray livestock, then read their brands or ear tags from the air. I move horses from one large pasture to another. And I chase away unwanted predators. Many times I turn and go back through my prop wash.
My SR5xp weighs about 300 pounds and the Legend weighs 340 pounds. I weigh about 190 pounds. Both machines have two seats, but I usually fly by myself. I had decided to purchase a PD 500 Sunriser. I‘m sure it flies slower than the 30 mph that you mentioned. Would you recommend a PD Sunriser 500, an Apco Mark IV/II 500 or something else?

[mignazito]

My preference would be an E340 or E310 Thunderbolt elliptical. That's me though. I no longer even own a square. The main danger with PPCs wings is possible wing collapse rather than a true stall from too high an AOA. Turbulence form a wing wake or wind effects from objects on the ground can cause a momentary wing collapse. Though the most PPC wings will reinflate "automatically" it takes some time for this and if you are close to the ground there may not be enough time. Lightly loaded, slow flying wings are more susceptable to such collapse though more or less unlikely in general.

[MikeRevier]

I like Apco MarkIV/II wings better than the P.D. as the P.D. fly's a little slower (when rigged same). Th P.D. is a great wing, but I prefer the material and the lines of the Apco. That said , if I were you I would either stay with your Apco (add the extra link on the C/D line set) or buy a Thunderbolt . I think the E-340 would be a better match for dual flying at your altitude. For best performance solo , the E-310 is better. Ellipticals do require a more constant wing loading on kiting and a fairly smooth runway also helps. Your initial wing trimming is also more important, but Marty or me can walk you through the steps and you could make a seamless transition.

Mike Revier

[luckyorwhat]

So increasing weight gives you more speed? Cool.

[Boback]

Yeah, it can really increase the speed. I have a friend that flies a Pegasus, just like me, with the same model chute, yet he is 100 pounds lighter to me. I run 3-4 mph faster than him. When we fly I have to do a couple of circles every mile or so to allow him to catch up.

[mignazito]

I have actually used sandbags in the back seat even adding 300 lbs once for a test program. I put 180 lbs in the back seat to keep up with Steve Thomas at about 42 mph with my Buckeye 582DM and Thunderbolt E280.

[johnbaum]

A story of an old bold pilot. Recognizing that you just experienced an accident because of a multitude of poor judgements is a humbling moment. Then recognizing that you are completely unhurt when by all rights you should be at least banged up pretty bad adds to that mentioned moment. It is with two main objectives that I share this story, one to recognize the Hand of my Father in preserving my life and two with hope that someone will not have to endure an accident because of reading this. I am a high time powered pilot with about 300 hrs. in PPCs and 65 years old this month, therefore the beginning statement.
Yesterday started like a day that I left the DM in the trailer. But about 3PM I looked out the window and noticed the windsock hanging straight down. 70 degrees, no wind and a heavy overcast at maybe 30,000 feet. Every PPC pilot knows that equals a delightfully smooth flight! I told my wife I was going to go up and snap some pictures with our new camera and see how they come out. I will be gone for 2 hours but will not be more than 15 miles from home. All went just as could be hoped for in the first hour of flight. Changing direction of flight didn’t change my 30 mph ground speed at all. I spotted two ground fires about 10 miles to the SE of my home and decided to investigate. As I neared the fires, I noticed that my ground speed had fallen to about 25, then 20 and finally 15. Wow, the smoke indicated a strong SW wind and turning into the wind, I noticed a ground speed of 10. I set a course for home and was making about 15 mph when I noticed sand being blown up from several fields. I guessed that the winds had already hit my home field so I decided to run down wind and hoped to get to a friends farm ahead of the wind storm. Now traveling 53 mph, I was fearful that the wind had already arrived at his farm also, but about a mile before I got there the ground speed dropped to 45 and I made the poor choice of proceeding with the landing. I made a 180 to come into the wind and noticed a barbed wire fence that concerned me greatly because my ground speed varied from 5 to 10 mph. With the fence finally cleared, I throttled back for the touchdown. The next part I do not understand, but suddenly the plane pitched down at about a 70-degree angle and the nose wheel hit and the DM rolled forward. Upside down, engine still running, fumbling for the kill switch, THUMP, THUMP. Well the engine isn’t running anymore! I crawled out from under the parachute, which had completely covered the overturned DM. I was finally able to right the DM and get the tire on top of the parachute so the wind would not pull it back into the fence. I will not be making the same mistakes again soon as the DM has a modified front wheel now resting firmly against the frame and several holes in a beautiful Chiron.
I am sure that you can see many errors causing this accident. ALWAYS check weather! Expect the unexpected, a column of smoke suddenly turns into a nearly horizontal column should tell you something. I noticed the roll cloud on my way back, a lot higher that I’d seen before, but it was there. I had plenty of gas and many places to land down wind, but was concerned that my wife would have to drive farther to pick me up, but I would have a flyable airplane now.
The pictures came out great. I don’t even have a bruise. BTW, the roll bars look great on the newer machines, but this DM has rolled several times with out any damage to the owner or machine. Yes, that was me too. No, my machine is not for sale!
John

[mignazito]

I suspect your wing collapsed due to a sudden slackening or reversal of the wind. At altitude this is not an issue since the PPC will respond and regain normal flight with some altitude loss. With no altitude in hand, you get what you got. SPLAT

[texasbagpiper]

I found an almost new 1999 model APCO chute for sale, but after reading this thread I'm not so sure an Apco would be my best bet. I don't want one that the ends open up slowly and surely don't want one that is prone to collapse. Anyways I need to find out what the model is. Are Apco chutes ok or is it just certian models of Apco that are prone to collapse and other problems. I'm starting to get tired of my old quantum chute because the end cells take extra time to open up and I have to pump and flare to get them to open up. Cheers, Seth

[woodyking]

ANY newer chute will surpass your early Quantum in kiting inflation I promise you. None have a problem of collapse either, though as you know, any could under the right conditions. You would never regret getting a Sunriser if you want simple easy everything. You might want the higher performance of a elliptical even. Newer Quantums like the Advantage are great also, APCO is fine. All in all, I love the silky smooth lines of a PD, so easy to lay out and shake out compared to the others. And, if a million stiff lines don't bother you, don't rule out a Quantum SkyBolt, unreal flare authority and not quirky, while able to carry weight with the best. Anything you get will have you smiling. Woody

[mignazito]

Seth:

If at all possible, try to fly it before you buy it. As Woody suggests the later models inflate better, but that one is 9 years ago and that is an eternity nowdays. Unless you are saving a bundle and are sure it will do what you want, you might just invest in a brand new one or at least a later model.

I also suggest in any case you pay for an inspection BEFORE you buy a used wing with any age on it. Good insurance in the event it needs repairs or is too porous to fly.

[Woober]

Hey Weaver, in that video you have linked; did the guy make his parachute do that on purpose?

Scott

[Weaver]

I have never heard anything about a frontal closure done by purpose.
This one is said to have been caused by an helicopter wake turbulence.
Maybe something like that: http://www.youtube.com/watch?v=E1ESmvyAmOs&NR=1

[jumper]

I have never heard anything about a frontal closure done by purpose.
This one is said to have been caused by an helicopter wake turbulence.
Maybe something like that: http://www.youtube.com/watch?v=E1ESmvyAmOs&NR=1

At Sun-n-Fun two years ago we flew over helicopters that were refueling but had blades turning. At 500 ft we got thrown pretty good. They had a trooper shot the night before and several copters were used for the man hunt and were in for refueling. No warnings were given and they landed in our pattern. Gave them a wide birth next time around.