SHOCK FAILURE ON SUPERSTOL

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SHOCK FAILURE ON SUPERSTOL

Postby Jeremy » Fri Jun 05, 2015 1:19 pm

I flew up the coast with my wife and landed at a place I’ve been to 3-4 times
before. It’s basically a steep road that leads up to a grassy plateau (where I park the plane): After spending a couple great hours enjoying the view, we decided to head for home. A tailwind had come up (7-9 mph) but it didn’t mean much, given the fact that the road pitches down at such a steep angle.

My wife Wendy said, “you take off and land first and then I’ll get in.” Everything went normally as I accelerated down the hill. There’s a small bump in the road which I’m used to, but as I hit it at perhaps 30 mph, the plane suddenly started sliding and veered to my right. Then it started to spin and slide down
the hill. I sat there trying to figure out what had just happened. The motor quit immediately and the whole event seemed surreal. When the plane stopped I got out and discovered the that right shock had separated at the midpoint (the black/silver junction

Frankly I’m puzzled, because I’ve seen what these shocks can take in the way of a beating on landing and this was nowhere near that limit during a take-off roll. Now that this has happened, I wonder why the shock designer doesn’t just stay with one solid tube for the entire length? The junction appears to be a problem (very thin walled tubing that is compromised further by threads cut into either end of the strut. And that is exactly where the shock failed.

Acme, the shock manufacturer concluded:
Since the actual cause of failure cannot be determined, several steps have been taken to improve the design of the strut:
1. The internal piston nut has been changed to a stover lock nut and a higher grade of
steel. The torque value has also been increased.
2. The internal piston base has been changed to a thicker, higher grade of steel.
3. The upper extension tube has been changed to a thicker wall while maintaining the
same outer diameter dimensions to keep the aesthetics of the shocks the same.
My conclusion. If you’re running the stock Acme shocks, don’t . They need to be modified, or replaced with something more durable, like the Monster Shocks. I feel lucky to have walked away from this incident. It could have been a lot worse based on some of the crazy places that I’ve landed.
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Re: SHOCK FAILURE ON SUPERSTOL

Postby SuperFly » Fri Jun 05, 2015 9:19 pm

Jeremy,

First, I am glad you are okay after your incident. That is always primary.

Can you provide us with any more information about how exactly it failed. Did it shear, twist, etc... was there any sign of early fatigue that could have weakened it? Post pictures of the failed area? (I don't ask that to stir problems for the manufacturer, but to inform those of us with that shock as to what to look for.
Also, what other damage it caused.
Best,
Ben Schneider
Highlander #263 converted to SuperSTOL
N45FT Now Flying!
http://www.stolairplane.com
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Re: SHOCK FAILURE ON SUPERSTOL

Postby HS-JAT » Sat Jun 06, 2015 7:51 am

SuperFly wrote:Jeremy,

(I don't ask that to stir problems for the manufacturer, but to inform those of us with that shock as to what to look for.
Also, what other damage it caused.


Call it like it is.

As an aircraft company there is a moral and professional responsibility to investigate and diseminate Safety of Flight Information on your product. Lives are at stake. I don't see much of that ever from JA (or a process to do that), or anything negative ever uttered on this forum about JA. Just a lot of fan club ra ra!
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Re: SHOCK FAILURE ON SUPERSTOL

Postby SuperFly » Sat Jun 06, 2015 10:52 am

Intentions with that statement are not to cheer anyone, nor tear down anyone. It is simply to find out facts. Degrading any person, any business, or any companies business policy is non productive on both ends. I am concerned with exactly what you offered up, safety of flight, and conservation of everyones well being. Perhaps it was not worded the best way possible, but that is the how it is intended. Again not looking for trouble, just clarifying my position.
Best,
Ben Schneider
Highlander #263 converted to SuperSTOL
N45FT Now Flying!
http://www.stolairplane.com
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Re: SHOCK FAILURE ON SUPERSTOL

Postby HS-JAT » Sat Jun 06, 2015 1:25 pm

Aviation is based on identifying defects/faults, investigating, and finding improvements. It is the responsibility that comes with the territory of owning an Aviation business, and where reputations are made or broken. Either you lead your business, and the required changes, or let a message board of hacks do so.
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Re: SHOCK FAILURE ON SUPERSTOL

Postby SheepdogRD » Sat Jun 06, 2015 2:13 pm

HS-JAT wrote:Aviation is based on identifying defects/faults, investigating, and finding improvements. It is the responsibility that comes with the territory of owning an Aviation business, and where reputations are made or broken. Either you lead your business, and the required changes, or let a message board of hacks do so.

Have you called or emailed the factory to get their response? Seems like that would be a good way to put the issue to bed.

I'd agree that information should be coming from JA to every owner who may have a potential shock failure... or any other kind of failure. I don't know of a system in place to do that, but the operative term here is "I don't know". I remember at least one other Service Bulletin -- a nosewheel issue -- so there is a precedent.

I wouldn't expect this forum to be the place for the factory's response, because no one from the factory officially monitors it. It's a user forum, and one of the pleasures of it is the consistently good attitude of its members. We are cheerleaders. Part of that civility probably stems from our collective experience with the factory. I haven't seen JA simply avoid issues. Since I'm not an SS owner or builder, I don't know what the factory is doing with this one.

I appreciate that this is NOT a factory forum, because it lets us do exactly what you recommend:
HS-JAT wrote:Call it like it is.

That's what Jeremy did. From what he wrote, it appears that Jeremy talked to the factory and then to the shock manufacturer. If this was the Viking Engines forum, the Sonex forum, or any other factory forum, a post like Jeremy's probably wouldn't have made it it through the moderator until the factory had a response prepared -- if, in fact, it ever appeared.

If I had a finished or nearly-finished SS with Acme shocks -- or if I didn't know which shocks it has -- I'd call the factory. If I were still building an SS and wasn't close to finishing, I'd wait a while and see how JA responds.

I don't expect they're ignoring the issue.
Richard Holtz
Highlander N7340Z -- Ms. Tonka -- in gestation

If just enough is really good, then too much ought to be perfect.
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Re: SHOCK FAILURE ON SUPERSTOL

Postby danerazz » Sat Jun 06, 2015 6:42 pm

My observation is the factory is not particularly good at communication, but if you call them about something you usually end up taking to Troy or somebody else with intimate knowledge of the aircraft and they actually listen and respond; a trait that I have seen lacking from much more "refined" kit makers.

I seem to remember a fuel/tank issue the factory put info out on a couple years back.

It is true, though, that most official info starts with someone calling the factory then posting their response here. Unfortunately it is usually preceded by a couple of weeks of complaining, guessing, and conjecture before a REAL answer is requested from the appropriate source.

With an issue like this the factory should be notified first, a cautionary post here is not totally unwarranted, and the official response then can be divulged as appropriate.
Dane

Paralysis by analysis
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Re: SHOCK FAILURE ON SUPERSTOL

Postby scubarider2 » Sun Jun 07, 2015 9:01 am

Call the factory and speak with Troy. Get his advice and counsel. Go from there.
Dennis
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Re: SHOCK FAILURE ON SUPERSTOL

Postby kenryan » Sun Jun 07, 2015 2:17 pm

I don't have specific information, but a little birdie told me that this is not the first Acme brand shock failure. I would like to know the extent of the problem, and would also like to know if any of the two previous brands had any failures.
Super Stol Kit #299
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Re: SHOCK FAILURE ON SUPERSTOL

Postby bluemax » Sun Jun 07, 2015 8:23 pm

ACME tools and parts always fail. . . That's why the coyote never gets the road runner . . . . :wink:
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Re: SHOCK FAILURE ON SUPERSTOL

Postby jak » Wed Jun 10, 2015 2:02 pm

Hey guys its Jak we are aware of the shock problem and as we speak are working with the manufacture to correct this problem. All of those who are affected with this issue will be notified shortly of the proper way to correct the problem.
Pick up a rifle and you instantly change from a subject to a citizen.
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Re: SHOCK FAILURE ON SUPERSTOL

Postby Jeremy » Tue Jun 16, 2015 12:37 pm

I haven't monitored this forum since I posted my story about the Acme shock, so it was interesting to catch up on everyone's comments.

In Acme's defense, their design was well thought out and tested. And they have since taken appropriate steps to beef it up and make it a much safer unit. Unfortunately in my case, it cost ($55,000) to fix the damage. They are confident that they've addressed the inherent weakness, which surprisingly, wasn't caused by the shock being compressed (which is typical on landing). On take-off I was running over some rough stuff and apparently, the nut that holds the shock together on EXTENSION failed. They've changed this nut and the column that connects the shock to the airplane. Hopefully this will go a long way towards improving the shock for all of us.

My goal was never to cast blame, nor to be an alarmist. Both Just and Acme are excellent companies. I simply wanted to send out a 'heads up,' so that with this knowledge, owners of Superstols could make their own decisions. Keeping it quiet was not an option. And that's what the forum is all about, sharing information so that we can safely enjoy our passion.
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