Strut Airworthiness Directive (AD) (merged VI)

[cpirrmann]

Re: Strut Airworthiness Directive (AD)

If the factory convinces the FAA to issue an AD and the only method of compliance is to buy a new fuselage from Harry, I can no longer guarantee his personal safety !

If the revised AD let's us get our struts from an alternative source and Harry gets few or no orders, then his scheme wil have been pulled out from under him and it'll probably be his next step. Drude showed the math...as they say, follow the money trail.

[cpirrmann]

Re: Strut Airworthiness Directive (AD)

As I understand, Eddy current or Ultra sound inspection will only detect cracks and wiil not tell you any thing about internal corrosion.. any experts out there ?? Also if it passes inspection I would like to see a longer interval for inspections like three to five years.

I'm not an expert, but doesn't it also detect wall thickness ?

[VictorBravo]

Re: Strut Airworthiness Directive (AD)

I just got off the phone with an aviation certified NDT lab here in Los Angeles.

I was told by the tech that Eddy Current is great at finding surface cracks but WILL NOT easily find corrosion inside a tube. There is a difference between low frequency and high frequency Eddy Current as well.

I was told that Ultrasound WILL find corrosion inside a tube or welded structure.

Can anyone verify that these two statements are or are not true?

If the AD is only concerned about cracked struts (bad thinking), there are many different types of FAA approved inspection to find surface cracks, even spray-on dye penetrant, magnetic particle, etc.

So someone please explain to me how the Eddy Current inspection that is referenced in the AD will find an internally corroded wing strut, assuming that corrosion is the primary gremlin we're looking for?

Someone with a metallurgy or structures degree needs to get in this mess and separate the wheat from the chaff before we all get so confused that safety is compromised, as well as losing money to P. T. Barnum.

[1938BF50]

Re: Strut Airworthiness Directive (AD)

I just got off the phone with Univair. Had a nice conversation with Dave. He informed me that Univair has a verbal OK from the Texas FSDO on approval of their struts. They are working with local FSDO to get official approval.

I asked of their manufacturing methods and how he thought the "Factory" would manufacture/provide these struts. He had not a a clue. I asked if he thought that the "factory" would purchase a lot run from Univair. Dave implied that that was probably not an option. If anyone knows how/where the factory is making/procuring these struts, I would be interested to know. I personally am very familliar with the pitfalls of manipulating 4130 steel and aluminum tubes, as I deal with it on a daily basis. In my mind it would take months or even a year(s) to work the nasty's out of something as complex as the metallurgical issues involved in the streamlined tubing we call struts. Based on my daily experiences with Asian tubing vendors, If I found out that the tubes are sourced overseas, I would not put one on my ship if it were FREE.

Back when, and as any reputable manufacturing entity would do, Univair invested heavily in a tube forming machine to make the Piper struts. I asked what would be involved in making the "correct" dimension Taylorcraft struts. It amounts to sourcing the correct round tube and investing in a set of dies. I asked that he forward my request to proper management channels as I thought there might be a lot of interest amongst Taylorcraft owners to get the "right" struts. I suggested that now might be the time to look closely at this issue internally.

According to Dave, they make runs of (50) strut/size when they set up for a run of Piper struts. They will do the same for Taylorcrafts. Processing thru the shop takes about 3-4 weeks. They are currently out of stock but are right on top of this issue.

[robbie]

Re: Strut Airworthiness Directive (AD)

question
Will we have to remove the paint to have these test done??

[VictorBravo]

Re: Strut Airworthiness Directive (AD)

Based on my daily experiences with Asian tubing vendors, If I found out that the tubes are sourced overseas, I would not put one on my ship if it were FREE.

And there you have it! The wheels that have been spinning in Brownsville might have been spinning in this direction for a while... Create a demand for, oh, say about five million dollars worth of wing struts, and then find a way to buy them for eight dollars and seventy four cents apiece from some company off the map. If, and I say if, this is what's going on, I think I'm about to vomit.

An interesting idea that cropped up in my mind is a new carbon fiber material called Graphlite. It's the stuff that was originally developed for the V-22 Osprey. Ten 1/8" diameter carbon rods would have over 35,000 pounds of tensile strength (as much as what a 2.5" tube x .049" 4130 would have), over 20,000 pounds compressive strength, weigh a couple of pounds (less strut fittings and outer fairings), and cost about $100 (for the rods). The strut could be a thinner airfoil that was asymmetrical (lifting), less drag, more strength, no corrosion, less weight, less cost.... need I go on?

Mike, what about Titanium? I understand it is highly corrosion resistant, and comes in various tubes, and is weldable, and there is plenty of engineering on it to make the feds happy. Forget forming the tubes to a new shape, just have two 1.5" square Titanium tubes, one behind the other, with an airfoil shaped non-structural fairing around it???

[astjp2]

Re: Strut Airworthiness Directive (AD)

Ultrasound will tell you wall thickness, its like a sonar within the metal, eddy current will detect the corrosion because it is a different chemical composition than the base metal.

here is the AC on corrosion and I remember it give some of the limitations for the different NDI methods. Tim

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/A7FFC0F8B6216A43862569B5005081ED?OpenDocument&Highlight=corrosion

[Dano"T"]

Re: Strut Airworthiness Directive (AD)

http://www.ndt-ed.org/EducationResou...inspection.htm Here is a link with some good info

[Dano"T"]

Re: Strut Airworthiness Directive (AD)

http://www.ndt.net/article/ecndt02/251/251.htm

tHIS ONE IS REALLY INFORMATIVE....WITH THIS YOU SHOULD BE ABLE TO DO A TEST WITHOUT REMOVING THE STRUTS.

[lfries]

Re: Strut Airworthiness Directive (AD)

Other than the SB/AD does anyone know why the struts need to be removed to do the testing. I spoke with a local IA today and he brings in a company to do NDT testing on Cessna Citations without removing the parts. It would seem that our struts are much more accessible than internal parts on a Span Can.

[Winston L.]

Re: Strut Airworthiness Directive (AD)

I think it is so the end plate can be inspected.

[crispy critter]

Re: Strut Airworthiness Directive (AD)

The Eddy Current should be able to be be done without removing the paint or the struts. I had a could of props done with eddy current and they didn't even pull the prop,just the spinner.
Also...under the rule of owner produced parts,if someone decided to open up there struts,inspect,treat,and reweld them up solid(sealed)...would this make the AD complied?

[Guest]

Re: Strut Airworthiness Directive (AD)

The way the instructions in the SB and AD read it makes me think that they also want you to check for debris inside.

I have 2 dozen struts in my shed from various planes and when you pick one up you can tell immediately which have corrosion debris inside by the sound.

The debris slides down that strut and makes a noise. If the strut has been installed on a plane, ie no open bolt holes for bees, then its very likley corrosion. That's what I think they are trying to make you detect. I think it actually says that in fewer words.

But in reality they are not giving you a choice, you have to follow the AD or get an AMOC approved.

[Ed O'Brien]

Re: Strut Airworthiness Directive (AD)

If they can run a camera and light through your gut and arteries... why not use it on an open strut? Why not have the same unit inspect spars? How could that take more than 30 minutes? Do it at every annual and charge $50.00? Personally, I'd feel better if I could see the issue for myself. A camera would allow for this. That way I know what I'm dealing with...

I would then also offer that we send through the strut a fat mouse heavily coated in petroleum jelly... but maybe I'm building a "less than better mouse trap" with that suggestion. Although this seems akin to cleaning a rifle barrel. A big damn swab on a string makes sense... or am I now officially losing it. I can supply the mice once the first freeze chases all of them indoors. I'm not looking for the cheapest fix... but I'd like a real fix that made sense and gave me a feeling of security. I hate flying along and being jumpier than say, a vaselined mouse on a string.
With regards;
ED OBRIEN

[DannyDot]

Re: Strut Airworthiness Directive (AD)

I just talked to my mechanic and have good news. He can pull the struts, take to the shop for NDT, and replace in a day. Total cost about $350 dollars.

I do plan to wait to see what AD might come out on the fitting so I can get it all done at the same time. Anybody contact the FAA on the possibility of a fitting AD coming out?

Danny Deger