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When stainless isn't stainless

AN23

Well Known Member
I am in the process of an avionics upgrade which requires the installation of the red cube. My installation requires two 1/4 inch NPT to #6 AN straight fittings. I am installing all stainless steel fittings FWF. I found the fittings on Amazon and ordered them. They arrived yesterday and I immediately noticed that they sure seemed light. I pulled the packaging out of the garbage and saw that they are stainless steel "colored" aluminum. The ad clearly states they are stainless steel. They aren't. I just wanted to give everyone a heads up,
 

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Good reason why I don’t buy any parts or materials that go in my airplane from Amazon or any other non-aircraft internet seller. Amazon has especially become a huge source for stuff being sold that is mis-represented, counterfeit, or bait and switched. I have received multiple examples of all three. Definitely buyer be warned.
I do consider local non-aircraft part suppliers (like Lowe’s or Adv Auto) as I can touch and read their packaging before I buy.
 
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misleading ad

The advertisement seems to contradict itself because initially it states that the Material is Aluminum but then further down it says made from 303 stainless??
 
The net is awash in garbage fittings.

If you need to go off the reservation for non-AN stainless steel, I'd suggest Parker or Eaton . Both are reputable manufacturers with a large network of local dealers.

Search "Parker Triple Lok" and "Eaton Flare Twin".

I prefer stainless firewall forward, but have no issue with good plating. Do not use black oxide coated steel fittings for fuel systems; too easy to get internal rust flakes. They are oil and hydraulic only.

Tom, you out there? Does TS Flightlines stock the small selection of common SS fittings we might use firewall forward?
 
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Not only scams- but no way to correct errors in listing.

I wanted a ShopVac high efficiency filter. They are out of business.Only Amazon ad had the right part number, incorrect dimensions, and a correct photo. The customer comments (2 yrs old) had it measured close to correct. I ordered (for free shipping) and they were exactly like the original dimensions but not filter material. I measured and posted with others to let folks know - - then tried to get Amazon to correct the listing. There is not a single place to do that. I tried the chat bot - no joy, real person chat-no joy - - I called and spoke to a person. They sounded just like the bots reading a script - -lots of word dancing - -then they committed to write a trouble ticket and pass to the advertising department.

I won't try to help them again - just bad ratings. The big A remains as my last resort and only non-critical items.
 
Thanks, Dan!

"Do not use black oxide coated steel fittings for fuel systems; too easy to get internal rust flakes. They are oil and hydraulic only."

Another gem from Dan Horton.

Merrill
 
Hi Dan----uhhhhhh yep.
Tom
p/s---Steve and I are thinking about a FWF adapter kit with stainless for the engine fittings and our MIL aluminum fittings for the sender manifold (VA168 and equivalent). Havent determined if we can justify this or not, but maybe some feedback here can sway or thoughts. I was thinking of the stainless with class 3 threads like our MIL aluminum fittings we have or our cabin brake systems that ALOT of you have. MOST stainless that you buy from industrial suppliers have class 2 threads.

Any feedback here?
Tom
 
Tom, I'd say yes. We need a reliable vendor for these things. And I'm happy with the stainless -3 fittings you sold me for my brake system.

Dave
 
"Do not use black oxide coated steel fittings for fuel systems; too easy to get internal rust flakes. They are oil and hydraulic only."

Another gem from Dan Horton.

Merrill

I have these black fittings all over the place in my fuel system. Maybe it's worth to discuss that point in more detail.
 
Local industrial hose fabricators, located in most every area, call aviation 37 degree fittings; 75 degree. Prices and quality of the product are good.
 
I have these black fittings all over the place in my fuel system. Maybe it's worth to discuss that point in more detail.

Wish I had a picture of a black steel -6 bulkhead fitting I removed from an AOG rescue, but it was before cell phones had cameras. The inner bore looked like someone had stuffed it with bits of rusty steel wool. I'm not exaggerating.

I did find a system low spot which trapped some water, and I can't say the fuel wasn't contaminated with something in addition to water. It ran fine on that fuel after cleaning the Bendix inlet filter, flushing everything, sumping the tanks, etc. The rust was downstream of a AFP line filter, which was neither clogged or harmed. Shortly before, the airplane had been parked at a paint shop for a while. I did not go further with investigation.

May have been a one-time deal, but since then I don't install them in fuel systems.
 
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Hi Dan----uhhhhhh yep.
p/s---Steve and I are thinking about a FWF adapter kit with stainless for the engine fittings ...Any feedback here? Tom

A kit might be nice, but just having a well known go-to for good stainless is the key, one part or kit.

BTW, are Class 2 threads really that big a deal? I'm guessing 90% of the Lycoming powered EAB fleet is flying fuel pump fittings straight from a hydraulic catalog. Here's one from a popular vendor site. Look close. Pretty sure I'd rather have a Class 2 Parker, or something you vetted.
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But most industrial suppliers dont carry Mil Spec fittings with class 3 threads. Although for OUR purposes, class 2 works just fine, if you are going to advertize as a Mil Spec or aviation fitting, it really should be class 3.

Just for giggles:rolleyes: I 'chatted' with tech support of a well known fitting supplier in the Denver area. I asked if the threads were class 2A or 3A and his response was, "I am not familiar with that specification. The AN threads we carry are 37 degree SAE threads with a 37 degree flare". So he answered the question without knowing the answer to the question.

Just because it looks like a REAL AN fitting, and the threads 'do connect', doesnt mean its an AN fitting. Materials, finishing, thread machining are all part of it. Lots of what I call imposter fittings out there. Especially the aluminum ones. GENERALLY for our experimental purposes, industrial steel or stainless is just fine. See if its stamped/etched'engraved AN on part of the fitting. That identifies that it was designed to meet the Aviation MilSpec, which is class 3.

ON the other hand----there are a 'few' manufacturers that DO make a AN grade fitting that is NOT stamped/engraved/etched, but meet the Mil Spec criteria. Generall those are just fine and just havent had the approvals from the FAA/SAE to allow that identification. Tough process. FOR EACH DRAWING AND FITTING.

So check it out --ask questions. Again for experimental applications, its not a big deal. But--consider the investment you have in your plane. Relatively inexpensive insurance.

My $.02 worth

Tom
 
Stainless Steel Galling

I would avoid using stainless steel fitting in a stainless steel housing. Stainless steel will gall.
I thought it would be a good idea to use stainless steel screws and stainless steel locking nuts from the local Ace hardware store for all the adel clamps firewall forward. That was a mistake. I tried to take one apart and it galled, had to scrap two clamps to get it apart. I changed out all the stainless hardware to cad or zinc plated steel self locking nuts and black oxide coated allen screws.

A long time ago, i used to build hypergolic systems for the F16 fighter. there we had a stainless steel housing with stainless steel screws (needed because of the hypergolic fuel used) we always were having trouble with the stainless steel galling. So be careful using stainless.

I am using the blue aluminum fittings firewall forward. The aluminum flare fittings and the stainless steel hose ends should provide a secure leak-proof seal. If it is good enough for WW2 fighters, it is good enough for me. But I have a steel fitting for the fuel pass through the firewall; i think I will change that to aluminum after reading the above.
 
But most industrial suppliers dont carry Mil Spec fittings with class 3 threads. Although for OUR purposes, class 2 works just fine, if you are going to advertize as a Mil Spec or aviation fitting, it really should be class 3.


Just because it looks like a REAL AN fitting, and the threads 'do connect', doesnt mean its an AN fitting. Materials, finishing, thread machining are all part of it. Lots of what I call imposter fittings out there. Especially the aluminum ones. GENERALLY for our experimental purposes, industrial steel or stainless is just fine. See if its stamped/etched'engraved AN on part of the fitting. That identifies that it was designed to meet the Aviation MilSpec, which is class 3.



My $.02 worth

Tom

Funny, i bought a firewall forward kit from Vans. One of the fuel hose had fittings stamped "AN". One hose had fittings that were not marked. Turns out the unmarked hose end fitting had a big burr inside and I had to carefully dress the threads to get it together nicely. Seems even Vans is suffering from inferior hose end fittings.
 
Yes John, correct----but we normally dont have alot of stainless housings that we deal with. Also true on Aluminum AN grade fittings FWF. There are some component manufacturers, like AirFLow Systems that specify steel for their coolers.

Tom
 
Earl's still great

Earl's is still a top shop. Very good service and very good quality hardware. But you should state it is for aircraft and he will make sure you get the good stuff. He has stuff for the car guys who are too cheap for the aviation quality stuff.
 
I would avoid using stainless steel fitting in a stainless steel housing. Stainless steel will gall.
I thought it would be a good idea to use stainless steel screws and stainless steel locking nuts from the local Ace hardware store for all the adel clamps firewall forward. That was a mistake. I tried to take one apart and it galled, had to scrap two clamps to get it apart. I changed out all the stainless hardware to cad or zinc plated steel self locking nuts and black oxide coated allen screws.

A long time ago, i used to build hypergolic systems for the F16 fighter. there we had a stainless steel housing with stainless steel screws (needed because of the hypergolic fuel used) we always were having trouble with the stainless steel galling. So be careful using stainless.

I am using the blue aluminum fittings firewall forward. The aluminum flare fittings and the stainless steel hose ends should provide a secure leak-proof seal. If it is good enough for WW2 fighters, it is good enough for me. But I have a steel fitting for the fuel pass through the firewall; i think I will change that to aluminum after reading the above.

I have exactly the same experience with stainless-on-stainless galling. Both with screws and threaded fluid fittings. At work, had a project assembling stainless AN fittings for an oxygen system. Of course, you can't use petroleum lubricants on that, but after destroying several fittings, we discovered Krytox which eliminated the galling. Great stuff, but a bit expensive.
 
It's out there. A machining grade.

Allan Aircraft Supply used to be a good source for stainless flared fittings. You cannot place an online order with them, however.

Regarding Earl’s: Back in the day (30 years ago) they used to produce all of their fittings in-house in Long Beach and and they had a lot of company pride for manufacturing quality products domestically (I once dated the company founder’s granddaughter). However, since that time Earl’s has been sold to the Holley conglomerate and they claim their manufacturing headquarters is in Ky but I would be very surprised if their hardware isn’t actually manufactured over seas these days.

Skylor
 
303 Stainless

It's out there. A machining grade.

303 has selenium or sulphur in it for ease of machining, but it makes the alloy highly susceptible to stress corrosion cracking. It should not be used for stressed applications.
Personally, I would not use anything made from 303 in an airplane. Why take an unnecessary and unknown chance? Vibration is a stresser.
 
303 has selenium or sulphur in it for ease of machining, but it makes the alloy highly susceptible to stress corrosion cracking. It should not be used for stressed applications.
Personally, I would not use anything made from 303 in an airplane. Why take an unnecessary and unknown chance? Vibration is a stresser.

Well I learned something today…been spending too much time around sail boats
 
Fuel system fittings from Amazon?!!!

I will never buy an RV built by someone else, or at least would not unless I knew them really well.

In that case, I guess you will limit potential buyers to a small circle of friends when you sell? I doubt it.

As usual, you try to post something to help others and some "expert" tries to assert their knowledge. I've learned there's just a personality that enjoys acting in this way. So be it.

In the end, no matter where the parts come from, it is our responsibility to inspect them and ensure they are airworthy. That's exactly what happened here and the part was rejected. Just because you buy it from XYZ certainly doesn't guarantee the part won't have a defect or be unsuitable. Recently, I purchased AN bolts from one of the MAJOR suppliers we all use and one of the bolts had no threads!

So, in the end, my RV will have ALL correct parts from AFP, T&S Flightlines and Dynon AND real, correct and safe stainless fittings. All is well .
 
Yeah, sorry it came off that way. You made a good call. What I worry about is all of those builders who don't pay the same attention to detail. Having built myself I know there are too many places where compromises could be made. Figuring out which builders pay consistent attention to detail and those who might make the periodic (but serious) compromise are the challenge.
Again, no insult intended to you though.

In that case, I guess you will limit potential buyers to a small circle of friends when you sell? I doubt it.

As usual, you try to post something to help others and some "expert" tries to assert their knowledge. I've learned there's just a personality that enjoys acting in this way. So be it.

In the end, no matter where the parts come from, it is our responsibility to inspect them and ensure they are airworthy. That's exactly what happened here and the part was rejected. Just because you buy it from XYZ certainly doesn't guarantee the part won't have a defect or be unsuitable. Recently, I purchased AN bolts from one of the MAJOR suppliers we all use and one of the bolts had no threads!

So, in the end, my RV will have ALL correct parts from AFP, T&S Flightlines and Dynon AND real, correct and safe stainless fittings. All is well .
 
From Earls, "This is the most comprehensive assembly of Adapters in the industry. All items have passed our engineering inspection to make it into selection. The differences in the various brands are as follows: XRP adapters are 100% machined in the USA from North American alloys. AN Plumbing brand adapters are made in the USA to AS / MS & AN specs and are commonly used in the experimental aircraft. Earls & Goodridge Adapters are globally sourced."

Tom
 
Some years back I inherited a stash of new aluminium fittings from an RV builder mate who built and promptly sold his aircraft. They were Earl's. They were not AN. On my aircraft I only used AN fittings. However down the track I had a friend who needed a couple of 90 degree fittings for his project and I toyed with the idea of giving him a couple of the Earl's fittings.

To the naked eye the Earl's fittings looked just fine. They were blue coated aluminium and they looked every bit the equivalent of my other AN fittings.

But I decided to throw them under my high powered Olympus stereo microscope and have a really good look at them first....particularly inside with proper illumination. Certainly glad I did.

The bores inside did not meet concentrically, there was protective blue coating missing intermittently in the interior, and worst of all, there were shards of swarf still precariously attached to the interior bore intersection.

The microscopic examination revealed serious flaws. And Earl's have a reasonably good name, but in the end you get what you pay for. If it's cheap there's a reason....and inconsistent quality control is a big part of that reason.

Now I would not ever entertain using fittings that were not AN quality. There's too much on the line with fuel, oil and hydraulic systems in aircraft. It's just not the area where you want to be penny pinching.
 
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bob, and the AN fittings you looked at all passed this scrutiny?


Yes they did....no problems. The closer I looked the more I could see it was like chalk and cheese. And it gave me a greater appreciation of what AN actually means.

Intrinsically everyone wants to believe that they can buy cheap and yet get high quality. It's a delusion but we've all been guilty of it. But with aircraft it can be a very dangerous delusion.
 
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I did get an AN832-6D one time that wasnt threaded on either end. Yep, stamped AN and D for aluminum, correct blue anodizing. And---it passed whomevers inspections.
Wish I had kept it----I think I hit it with a LARGE hammer and tossed it. Yes it came from an aviation source.

Tom
 
I did get an AN832-6D one time that wasnt threaded on either end.

And I don't doubt for a minute Tom that what you say is true. An AN spec is certainly no guarantee that the item is defect free. What it does guarantee however is that the item is CONSIDERABLY less likely to have a defect than a cheap Chinese knock-off with no pedigree.
 
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Most of the parts and fittings on my project come from either Vans or one of our glorious sponsors (<----see left hand side of VAF). For a few hard-to-find items, I've had pretty good luck on eBay. Almost all my tools come from there, but also a few fittings, air hose stuff, and weird sized nutplates and so on. You can generally find great deals on milspec wire there, too.

Amazon, on the other hand, no way no how. Too many counterfeits and junk. The only thing I recall actually buying there and using were some marine LED lights for overhead my baggage compartment. No safety of flight consideration.
 
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