Damaged reserve lines - Strong DHT + MR 425

[Zahry 0]

Hi Everyone,

During a few casual reserve repacks I found damage on lines (photos of some photos are attached - I have much more). Because the reserves were due for inspection and porosity testing I've send it to Strong representative. I've been assured by the person the lines are in good condition and all reserves were certified by him as airworthy. Just as a rhetorical question: Does anyone thinks that was a bad call I refused to put the reserves to service until the lines will be replaced?
Because I was concerned about the reasons why the lines has got damaged I've started a little investigation (I found damage on other reserves). I found the damage is repetitive and mostly I found the damage on the same places. After playing around I found the damage is almost always very close to the plastic chokers on the free bag or close to drogue riser. It seems to me the cause of the damage could be the plastic chokers and the lines can be getting the damage during freefall as the rig is "working". It appears to me as the rig vibrates, stretches during drogue deploy and parachute opening and the drogue riser is brushing the reserve wall (the reserve wall is showing a lot of wear after few years in service). It could be the causing enough movement to wear the lines or induce enough movement to allow the chokers to damage/cut the lines (lines seems to me very exposed - Kevlar is sensitive to abrasion and easy to wear as far as I know and if the plastic chokers are not smoothened it could cause even more damage).

The damage is very hard to spot if you try to find when the reserve is hanging. The easiest way how to find it is lay all the lines down on some dark background and run throug the lines.

What is your opinion about this case? Does anyone have similar problem with Dual Hawk Tandem system?

[JustChuteMeNow 0]

I have seen some minor abrasions like you have mentioned on some kevlar lines. However, it is a wear pattern very similar to abrasions on a brake line. Generally speaking on the Strong reserve if the choker is tight like it is supposed to be then I haven't seen any issues. I say this because I have done repacks where the previous rigger did not close the chokers and this for sure allows the line a lot of movement and IMO will cause wear. The bigger issue for me was THE CHOKER wasn't closed and this is dangerous.

FWIW if Strong says the rig is airworthy I'm sure it is. It would obviously be in their best interest to sell you a new line set. I'm equally sure that they wouldn't want an incident on one of their rigs due to a line breaking.

Think of how stupid the average person is and realize that statistically half of them are stupider than that.

[DualHawk 0]

Hi Tomas,

I've spoken to Chuck McHugh, our resident expert on the Master reserve here at Strong Enterprises in Orlando, regarding your post. The Master reserve has been produced since 1986, and Chuck has been inspecting and recertifying them here in Orlando since 1990. He said that over the last 16 years, he has seen very little damage to Kevlar lines on the reserves that he has inspected, so from our perspective, we wouldn't consider it a trend. That said, of course any time a rigger in the field finds any damage to a line, it would be prudent to have it inspected and replaced when necessary.

Strong Enterprises is committed to maintaining the structural integrity of our tandem systems in the field, and that is why we require an 8 year and subsequent 5 year inspections of the Dual Hawk system for airworthyness recertifications. It allows us, (and our designated service reps around the world), to inspect and (when needed) repair gear before any wear poses any potential for critical wear. We believe that our recertification policy is another layer of safety for our instructors in the field.

If you have any questions related to the Master reserve, or anything Dual Hawk tandem related, I would be happy to help. Please feel free to call me at 407-859-9317 or email me at [email protected]

Best Regards,

Tom Noonan
Tandem Director
Strong Enterprises

[riggerrob 563]

That reminds me of Velcro damage that I have seen on several Strong 425 reserves. I believe that the damage is caused by the hook Velcro on the lower corners of the reserve container. Most of that damage has been in the form of weave separations, with broken strands in only the worst cases.
The only solution is to be sure and bend the hook Velcro away from the lines while packing. I suppose that a fanatical rigger might use some sort of 2 inch wide Velcro protectors.

A couple of times, Strong Enterprises insisted on replacing frayed lines when they did 8-year inspections on those reserves.

The other area - where I have noticed fraying - is at the connector links. I suspect that L-bar links are sneaking out of the forging mill with rough edges inside their elbows.

The only difference is that yours is worse and seems to include a few broken lines.

As for the Kevlar lacking latex coating and being easy to snag ... that is the way it was designed. Kevlar was originally designed for high-temperature environments (i.e. dragged through the brutally hot jet blast behind a fighter plane) where latex coatings rapidly burn off.

[RIGGER 0]

Well done.

The lines shows in the photos must be replaced.

No reason to have Tandem Reserve with Kevlar, Spectra or Vectran lines even they were TSO'd.

They do not starch & might damage the canopy or break during deployments - done in the past.

Tandem reserve should be with Dacron lines like the VR360 by PD/RWS/UPT

Safe Rigging !!!

[ZigZagMarquis 8]

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Hi Tomas,

I've spoken to Chuck McHugh, our resident expert on the Master reserve here at Strong Enterprises in Orlando, regarding your post. The Master reserve has been produced since 1986, and Chuck has been inspecting and recertifying them here in Orlando since 1990. He said that over the last 16 years, he has seen very little damage to Kevlar lines on the reserves that he has inspected, so from our perspective, we wouldn't consider it a trend. That said, of course any time a rigger in the field finds any damage to a line, it would be prudent to have it inspected and replaced when necessary.

Strong Enterprises is committed to maintaining the structural integrity of our tandem systems in the field, and that is why we require an 8 year and subsequent 5 year inspections of the Dual Hawk system for airworthyness recertifications. It allows us, (and our designated service reps around the world), to inspect and (when needed) repair gear before any wear poses any potential for critical wear. We believe that our recertification policy is another layer of safety for our instructors in the field.

If you have any questions related to the Master reserve, or anything Dual Hawk tandem related, I would be happy to help. Please feel free to call me at 407-859-9317 or email me at [email protected]

Best Regards,

Tom Noonan
Tandem Director
Strong Enterprises

Tom,

Thanks for the post.

Question... would you care to comment on the photos that Zahry put up in his OP? What level of damage would you or Chuck consider that? ... if y'all would consider it damage at all?

My concern is two fold... first... some call that "minor"... not to start an argument, but I'm not sure I'd use the word minor, having said that though, I'm wouldn't use the word major either... second... it may be a bit hard to tell from the photos, but might there not be broken strands pictured there? ... if this is the case, wouldn't a re-line be in order??


A different system I know, but I once sent a PD Reserve back to their factory for inspection because of a somewhat similar issue. When presented to me for a repack (after a reserve ride), during the "I" part of the "I&R" I found "damage" similar to what's pictured in the OP on some of the reserve line... mainly the steering lines. The "best guess" of myself and the other riggers about the DZ was that during the previous packjob the rigger hadn't been careful keeping the lines out from / off of / away from the hook side of the Velcro on the pocket on the freebag. It wasn't really bad, but it was enough to notice and make you think. The rig's owner and I talked it over and decided to send the reserve back to PD for an inspection & possibly replacing the lines in question. At the time, PD recommended a complete new line kit rather than just replacing the few lines (2) in question... there were some trim issues as well that they found when inspecting the canopy.

[Zahry 0]

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Generally speaking on the Strong reserve if the choker is tight like it is supposed to be then I haven't seen any issues. I say this because I have done repacks where the previous rigger did not close the chokers and this for sure allows the line a lot of movement and IMO will cause wear. The bigger issue for me was THE CHOKER wasn't closed and this is dangerous.

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I'm well aware of the issue you mentioned and in this case it is not the problem. All chokers are tight. I know what's gonna happen if I'll leave the chokers loose

FWIW if Strong says the rig is airworthy I'm sure it is. It would obviously be in their best interest to sell you a new line set. I'm equally sure that they wouldn't want an incident on one of their rigs due to a line breaking.

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I seems to me as like the damage wasn't found at all.

[Zahry 0]

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That reminds me of Velcro damage that I have seen on several Strong 425 reserves. I believe that the damage is caused by the hook Velcro on the lower corners of the reserve container.

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It appears as like velcro damage. Personally I suspected the vecro first time as well. I know it is possible to damage the lines like that but I don't think it is the case. Yesterday and today I did a few repacks and I was checking every thing mentioned in every reply (even if the chokers were tight - I'm just a human as like everyone)

The only places where I found the damage was directly under the loop close to choker (I was pulling the loops out one by one and I was checking the lines immediately) and I found the lines were more worn close on the bottom close to drogue riser

A couple of times, Strong Enterprises insisted on replacing frayed lines when they did 8-year inspections on those reserves.

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Unfortunately the reserves hasn't been inspected in Strong Enterprises US, but by their representative outside US.

The other area - where I have noticed fraying - is at the connector links. I suspect that L-bar links are sneaking out of the forging mill with rough edges inside their elbows.

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Good point, I've noticed that as well, sometimes there is a little sharp edge in the joint. Nothing much what we can do about except keeping those things tight and the lines away from the joint.

The only difference is that yours is worse and seems to include a few broken lines.

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The damage is always worst on rigs with the most jumps per repacking cycle (doesn't matter if the gear is new or old). The rigs with those reserves inside has done roughly 600 - 800 jumps within 6 months. We have 2 rigs which are not popular to jump (100 -200 jumps per 6 months) and the reserve lines never showed a wear or damage

[Zahry 0]

Thanks Tom,

Mail with more details will be on the way soon.

[DualHawk 0]

Hi Shlomo,

The first Master 425 reserves with Kelvar lines were produced in 1984. Strong Enteprises has 23 years of data on this canopy, and we continue to be satisfied with our line choice. I understand that you do not agree with our decision to use Kelvar lines on the Master 425, suffice to say, we are comfortable to simply disagree with your statement regarding Kevlar lines versus Dacron lines.

It was a pleasure to meet you at PIA in Reno this year. Ted Strong and I are planning to attend the PIA International Symposium in Barcelona in 2008, if you are able to attend, we'd look forward to seeing you at the Strong Enterprises booth. I'd be happy to bring some of the historical data that we have on the kevlar lines and the Master 425 for you.

Best Regards,

Tom Noonan
Tandem Director
Strong Enterprises

[DualHawk 0]

Hi Tim,

Chuck and I looked over the pictures, and we agree with replacing those lines. Some lines were definitely worse than others, but it's never a bad decision to replace a line your not comfortable with.

One of the pictures showed the lines laid out on what looked to be a beige polypropylene surface. Just as a side bar to this issue, the Belgian Army Parachute School issued a letter at PIA in '99, that showed the results of some research they did on packing surfaces, and polypropylene was found to be a very abbrasive surface for packing. It was found to be just above packing on asphalt in terms of abbrasion factor. So, my 1st recommendation would be to pack the reserves on a carpet and see if you notice any change in the wear of the lines.

While I'm here, I thought it might not be a bad idea to give some general background information on the Master 425 reserve:

Anyone that has met or spent any time talking to Ted Strong about tandems knows that his philosophy and approach to tandem jumping is very conservative. When it came to building the Master 425, he wanted a canopy that would protect our instructors and passengers against all possible reserve ride scenarios, including the "no drogue" tandem terminal deployment, so the Master 425 was designed and built to handle the opening shock of a no drogue tandem terminal deployment. (The Master 425 was TSO drop tested at 600 lbs, at 210 kias.)

The 1st defense against a tandem terminal deployment is the flat pack. This is to prevent the "instant canopy" result that a propacked reserve can generate at that high of a speed.

Second line of defense is the bungee chokers for line stows, as they are designed to prevent line dump. The bungee chokers MUST be tightened on each line stow.

Third line of defense is the 750lb kelvar lines with kevlar reinforcing tapes. Kevlar has a much lower friction coefficient than Dacron, meaning that in a high speed deployment, Kevlar lines are much less likely to cause burns to the canopy than Dacron. Kevlar lines, due to their slipperiness (if that is even a word...) , are also much less prone to tension knots than Dacron lines. The trade off of Kelvar lines is of course that they are more sensative to damage during normal handling, but we feel that it is a worthwhile trade off for all of the benefits that kevlar lines offer.

If anyone has any specific questions, please feel free to call me at 407-859-9317 or email me at [email protected].

Best Regards,

Tom Noonan
Tandem Director
Strong Enterprises

[RIGGER 0]

I know SE likes the Kevlar - they still use it.

I'll not open the history data here maybe if we will meet at Sym.08

Take care & keep doing the great work.

Safe Jumps !!!