Fake/counterfeit bolt used in gyro

[gyroguy]

This is a message from the PRA Safety Guy. Eventually it may end up as an article in Rotorcraft magazine, but that would be months away.

Here's the story. I live outside of Dallas, and a couple of days ago I went over to Air Command International at Caddo Mills, Texas, to borrow a cut-away target drone engine. I'm a Scoutmaster and had been drafted to teach the Aviation merit badge to a group of Boy Scouts.

Red Smith, who owns Air Command International, showed me a rotorhead bearing with a BENT Jesus bolt sticking through it. He told me that someone in a different state had bought a used Air Command gyro, and after crashing it, discovered that someone else (not Air Command) had rebuilt the rotorhead. In the crash, the rotorblades hit the ground, and the Jesus bolt bent. When the rotorhead was sent to Air Command International, they spotted the fake Jesus bolt.

For those of you who don't know, the "Jesus bolt" is the vertically-oriented bolt around which the top of the rotorhead spins. It's nicknamed a "Jesus bolt" because if it breaks... well, you can guess.

The bolt used in the rebuilt rotorhead was a HARDWARE STORE bolt. It was cadmium plated like an AN bolt. But the only letter showing on the head of the bolt was the letter "X" -- while a typical AN bolt has the initials of the bolt manufacturer, such as "C S" or "A F C" in addition to the "X."

Hardware store bolts are typically softer steel which bends easier and may break easier. Their threads are cut instead of rolled, though it takes a loupe and some experience to see the difference. They tend to break off where the threads are, since the bolt is already cut there.

The difference between a REAL AN BOLT and a FAKE may not be limited just to the letter or letters on the head of the bolt. There are also counterfeit bolts. These look just like the real bolts, with the right letters -- but they were not made by the real bolt manufacturer and were not made to AN bolt standards. I've been told that some of these bolts are made cheaply overseas, and once they get into the U.S., there's an excellent profit margin on them because they cost little and sell for as much as the real thing.

An AN bolt has a history that is documented and available from the bolt manufacturer. The documentation shows how bolts from that batch of bolts were made, what tests they passed, and that they met AN bolt standards. The fake bolts have no such history or documentation because they're fake. Same deal with the counterfeit bolts, except there's no easy way to tell they are counterfeit unless you run them through the same tests as the AN bolts.

So how can you tell the difference? Obviously if your rotor blades fly off when the Jesus bolt breaks, you probably had an inferior bolt. The only other suggestion I can give is to carefully examine your rotorhead this winter.

If you purchased your gyro kit directly from the gyro kit manufacturer and you are the first owner, you can assume that the bolts in your rotorhead are REAL.

If your purchased your gyro used, from a second party, carefully examine the rotorhead to see if there are any wrench marks, bending, changes in the amount of dirt/dust/grease that make some parts stand out, or any other quirks that might mean new parts or bolts have been installed. If so, contact the gyro kit manufacturer and arrange to have them inspect your rotorhead.

For the record -- it is probably just a fluke that someone put a cheapo bolt in the rotorhead that Red Smith showed me. The fake bolt was NOT from Air Command International. The cheapo bolt did not cause the accident -- inadequate flight instruction and a macho attitude did. The bolt did not break, it only bent. This is the only instance of a hardware store bolt being used in a rotorhead that's been brought to my attention, so there is no trend.

My personal opinion is that anyone who knowingly deals in fake bolts or counterfeit bolts for use in aircraft is a potential murderer.

That about sums up what I know, but if there are any questions please e-mail me at <gyroguy@ev1.net>

[Brian Jackson]

Thanks, Kerry.

Stories like that get my blood pressure going, as I have little tolerance for those whom produce "disguised" products masquarading as legit., especially something as critical as Army-Navy Standard hardware. The same thing happened during the American Civil War when some cannon manufacturers knowingly used inferior alloys that couldn't handle blast pressures. The cannon barrels themselves thus became huge, localized hand grenades, fragmenting shrapnel that killed many.

Frankly I'm surprised it's taken this long for the forgers (not to be confused with metal forging, though there's a joke lurking there somewhere) to attack that market. Gullible patrons inevitably attract, and even spawn, questionable suppliers. So we can be very thankful that reputable sources maintain histories and certifications of the critical parts we buy.

I'd heard about this fake-AN thing some months ago, and made it a practice to request paper documentation for every nut-&-bolt I buy. It's my "proof" that I can trust my life with a product. Granted, when I'm done my builder's log will stretch several volumes, but I like the assurance of a certified paper trail.

Thanks again for posting that story. Proof-positive forums like this can save lives.

Respectfully,
Brian Jackson

[KenSandyEggo]

O.K., we have a problem here. You say the "Jesus-Bolt" is the vertical bolt. In my circles, it is always the teeter-bolt. Can there be more than one "Jesus-Bolt?" Actually, there are quite a few on a gyro, so check them all. Some are in the control system.

[Brian Jackson]

O.K., we have a problem here. You say the "Jesus-Bolt" is the vertical bolt. In my circles, it is always the teeter-bolt. Can there be more than one "Jesus-Bolt?" Actually, there are quite a few on a gyro, so check them all. Some are in the control system.
Good point, Ken.

My understanding of the term "Jesus Bolt" refers to those higher on the load "food chain". But I concur that even a seemingly innocent bolt, under adverse conditions, could be the first domino in a catastrophic failure. If memory serves, all aircraft accidents are the culmination of multiple failures in rapid succession, preventable by, say, stopping a domino chain midstream. So I'm guessing that the term "Jesus Bolt" means the fatal failure point where you only need one domino.

Just a thought.

Brian Jackson

[Aussie_Paul]

All aircraft have bolts that if they fail you are dead.!!!!!

Aussie Paul. :)

[Victor Duarte]

I concur that even a seemingly innocent bolt, under adverse conditions, could be the first domino in a catastrophic failure.
I m with you, loose a bolt from he control chain and adios.
I guess every bolt has been dimensionned to endorse a given effort , not more.

Just for the record. i worked in aftemarket spare parts for the Renault net.
we had a lot of problems with fake parts, for example brake pads whitch didn't brake but, instead, filed the discs very fine !
We also found fake/bad alu molded parts (engine supports, damper supports), dirty fake cleaner, plastic clips, and even diluted brake fluid !

anecdotic : a workshop was specialized in rebuild body parts, they took the accidented ones, brought some good metal workers from portugal, sold these parts as new, while the new ones were shipped to other workshops..

In automotive , there's a BIG fake market.
IMHO : buy known brands from shop to hand, not hand to hand.

cheers

[Jazzenjohn]

It would be interesting to test them and see exactly how strong they are.

[Victor Duarte]

John, yes also would be I ;) excuse my frenglish
Jim, have a look on the rotorhead design thread, talking about bolts.. your opinion or warning may be very valuable for us and others.

from the pics i think he fake is the left one (2nd pic), at the risk to look "pedant", i learnt that in an ideal bolt, the lathed chamfer must be tangent to the hexa pans... on the left, it is roughly done.
thanks

[barnstorm2]

O.K., we have a problem here. You say the "Jesus-Bolt" is the vertical bolt. In my circles, it is always the teeter-bolt. Can there be more than one "Jesus-Bolt?" Actually, there are quite a few on a gyro, so check them all. Some are in the control system.

Ken, My experience is the same. The bolt referred to as the Jesus bold is the teeter bolt. I am under the impression the term comes from vietnam air cav crews.

On my Air Command I call the teeter bold the jesus bolt ( and jesus nut ) and the six bolts that hold the blades to the bar the 12 apostles (I am a recovering x-catholic).

[Udi]

Kerry - just FYI, when I rebuilt my old Air Command I replaced most of the hardware with new. Some of the old AN bolts - which I believe were the original bolts that came with the kit - had one X in the center of the head with no other insignia. The fact that the spindle bolt was bent, rather than broken, tells me that it was probably a genuine AN bolt. AN bolts are designed to stretch and bend, while hardware store bolts, to the most part, will break under the same load. I am not so sure that the bolt in question was not the original AC bolt. If you are going to write an article around this incident, it would be a good idea to have this bolt tested by a competent metallurgist. Maybe even the FAA/NTSB would want to help.

There is only one bolt in the gyroplane that is carrying the whole weight of the gyro in tension - the spindle bolt. For me, this is the Jesus bolt. There are three bolts that carry the weight of the gyro in shear - the teeter bolt, the pitch pivot bolt and the roll pivot bolt. In comparison, I think the spindle bolt is much more "Jesusy". :eek:

Udi
p.s. see below some of the old Air Command bolts that I have kept from the rebuild. All the ones with the X are 1/4" AN4.

[gyroguy]

Appreciate the interest in this post!

Thanks for the pix on the Air Command bolts that have an "X" on them. The bolt that I was referring to has an "x" that is slightly smaller than 1/8 inch high, also centered on the bolt head. It looks totally different from the "big X" bolts, some of which I have also seen in use. Sorry for not being as descriptive or explicit as I could have been about the "small x" bolt.

I need to clarify my nomenclature. FYI, the bolt I called the "Jesus bolt" is the bolt with the largest diameter. It goes vertically through the largest bearing. Everything hangs from it. I call the "teeter bolt" the "teeter bolt." Though everything also hangs from it, this bolt has a significantlly smaller diameter. There is not a lot of redundancy in the use of bolts on gyros. As Aussie Paul notes, there are several that if snapped will get you an immediate appointment with Jesus. You can call any bolt whatever you wish. I'm concerned with bolt quality, not parts names. OK, end of my explanation.

I am making a second post because there's information from the U.S. Department of Energy on bolts that they have blacklisted as suspect or counterfeit. Batches of bolts from these manufacturers were tested and found to be substandard. The letter in the left column would be found on the bolt, and the right column gives the manufacturer.

A Asahi Mfg. (Japan)

CA Infasco (sizes above 1/2") (Japan)

E Daiei

FM Fastener Co. (Japan)

H Hinomoto Metal (Japan)

J Jinn Her (Taiwan)

JP Infasco (sizes above 1/2") (Japan)

KS Kosaka Kogyo (Japan)

KY Kyoei (Japan)

M Minamida Sieybo (Japan)

MS Minato Kogyo (Japan)

NF Nippon Fasteners (Japan)

RI Takai Ltd. (Japan)

TW Infasco (sizes above 1/2") (Japan)

UNY Unytite (Japan)

YU Infasco (sizes above 1/2") (Japan)

? Infasco (hollow triangle) (Japan)

Bolts that have letters DIFFERENT FROM those on this list are not considered suspect or counterfeit. For examples, check the bolts on a Rotax engine or your gyro kit. An "AFC" bolt in an Air Command International kit, for example, is not on the list -- so it is unlikely to be a suspect bolt.

Bolts of foreign origin without any manufacturer's headmarks are automatically suspect.

The information above covers Metric and SAE ("American") bolts. Some of the same manufacturers also make AN bolts.

The most common metric bolts are Grade 8.8, and their manufacturer's marks are on the head or stamped on one of the flats on the side of the bolt head. Sometimes the marks on the flats are marred by tool marks when the bolt is tightened. Look at the bolts before you install them.

SAE bolts have six radial lines at 60-degree intervals to identify a Grade 8 bolt. There are three radial lines on the bolt head, at 120-degree intervals, to identify a Grade 5 bolt. Bolts without these identifying radial lines are not as strong as Grade 5 or the stronger Grade 8. Typical hardware store bolts are Grade 2 or 3 and are unmarked.

I don't have the capability to scan such bolts, send the pix, or draw them. So I hope you have a good imagination RE the SAE bolts.

I went down to the hardware stores in Canton, Texas. Using the bolt list, I found several bolts that matched the letters on this list. These bolts would be suspect for aircraft use, but they'd work fine on my riding lawn mower.

I'd appreciate any comments on this list, especially additions/deletions as the source of my information is a couple of years old. I am sure that other bolt manufacturers worldwide should be added to the list. And who knows? Maybe some should be deleted from the list after making a better product.

[scottessex]

Any problems with NAS bolts? Most NAS have the part # on the head, like 6604-xx (length)
I know there have been many problems with alot of things since de-regulation.

[Udi]

See attached document on the US patent office (trademarks) for a list of bolt manufacturers and their respective insignia:
http://www.uspto.gov/web/offices/tac/fqa/active.pdf

Udi

[Cobra Doc]

Want to hear something REALLY scary? Experimental aircraft are not required to use AN or NAS parts, nor do they have to be traceable. I know several "distributors" that specialize in buying parts from legitimate aircraft parts companies that have misplaced their traceability. With old stock, it happens. These distributors can usually be found at any major fly-in selling nuts and bolts out of a big trailer. I've looked at the parst they are selling and for the most part they seem to be legitimate AN and NAS parts, but there is no way to guarantee that. If you buy a used experimental aircraft, you are on your own. Every week I get to see what we refer to as "the funny papers", a report of all the claims from the previous week. I would never buy a used amateur built aircraft. But that's just me and I realize that not everyone can build an airplane or even a square picture frame. ;)

[gyroguy]

Want to hear something REALLY scary? Experimental aircraft are not required to use AN or NAS parts, nor do they have to be traceable... If you buy a used experimental aircraft, you are on your own.

Right on, Don. Let me add a note on Ultralight and Experimental aircraft.

I bought the remains of a Bensen-type gyro that had hardware store bolts, coated clothesline wire for rudder cables, non-aircraft pulleys with no keepers, screen door hardware to connect rudder cables, and no lock nuts (or even hardware store lock washers) to hold the bolts on. I bought it so it wouldn't get rebuilt as a "flyable gyro."

Would it have flown? Sure! ONCE. Then engine vibration would have vibrated the nuts off the motor mount, and the motor would have fallen off... if something else didn't fall off first. It was a true deathtrap, and the worst aircraft construction I have ever seen. IT WAS A LEGAL ULTRALIGHT AIRCRAFT (EMPHASIS!).

With an Ultralight aircraft it is possible to be perfectly legal and perfectly dead. No one officially inspects ultralights. You're on your own.

Experimental aircraft must pass an airworthiness inspection done by an FAA employee or an FAA designee. I can guarantee that the Bensen-type gyro mentioned above would never have made it through such an inspection. With Experimental aircraft, there IS an intelligent human being (besides yourself) looking at the machine before it is allowed to fly. This is not a complete fail-safe, because the builder may make changes later on. But at least an Experimental aircraft starts off airworthy.

Don is correct in saying that AN or NAS bolts are not required on Experimental aircraft. The FAA inspector can, however, require the builder to change bolts if he wants to pass the inspection. I doubt that you'd get an airworthiness certificate if you had Grade 2 hardware store fasteners in your control system, for example.

Continuing to use Air Command Internal as an example, they have shelves and shelves of AN hardware. It's trackable and documented AN parts (since Red Smith bought Air Command in 1992, anyway). I'd have no qualms about buying an Experimental Air Command International gyro kit. (To be fair, I can say that about the Dominator, Butterfly, and several other gyro kits.)

However, Don makes a good point. Some people can't square a picture (or replace a light bulb)... but they think they can build a gyro. So if you're considering the purchase of a used gyro and don't know what to look for, bring someone along that does (like an Airframe and Powerplant Mechanic).

Just because AN or NAS hardware is used does NOT mean every fastener will be installed correctly. You have to check them all. Bring the list of suspect or counterfeit bolts, too. (Thanks, Udi, for the Patent Office URL with bolt manufacturers.)

The topic of this thread is suspect or counterfeit AN bolts. Let's expand it to include other suspicious aircraft hardware. No automotive hardware or garden tractor parts, plez.

The question was asked whether there are suspect or counterfeit Mil-Spec bolts. I don't know. If anyone does, please post here. (I probably won't be able to post for a week or so. Enjoy!)

[GyroRon]

The Dominator for the most part is assembled using plain jane hardware store Grade 8 hardware. The rotorhead and teeter bolt and even the Jesus bolt I believe is all Grade 8 hardware store stuff. What do you guys think of that?

Mine has AN bolts in place of the Grade 8's in certain areas but like I said the bulk of the machine is held together with hardware store grade 8 with no paper trail other than maybe a True Value reciept!

[GyroRon]

Kerry, I have read your article in a recent Rotorcraft mag, about your used gyro death trap. I understand why you wrote the article and for the most part I agree with the point your trying to make by the article and your " don't buy a used gyro " attitude.

But I do disagree of course with that train of thinking, that a person should not buy a used machine period.

I ask you this..... Don't you have a gyro? Isn't it built properly? Isn't it a safe machine? Okay if you said yes, then what are you saying.... is it built right and safe for only you to fly? No one else could fly it and be equally as safe?

all I am saying is it might be better to educate people on what to look for when buying a used machine, and what to do when you get it home to insure it is safe and ready to go. I know there are many good gyros out there flying around, and if one of them comes up for sale, and it is a good machine, then there is no reason just cause it is used that people should NOT consider buying it.

I agree that there are many old junkyard gyros out there, some for sale. Really old and or really cheap is usually clues that something isn't right. But with some education and help from fellow chapter members, a person CAN find a good used machine and can learn to avoid the junk.

But telling us that we should not ever buy a used gyro is also saying under the same breath that we should keep in mind while building a new more expensive kit that we are building something that has no resale value since no one wants to buy our junk!

[gyroguy]

...I understand and for the most part I agree with the point your trying to make by your " don't buy a used gyro " attitude. But I do disagree of course with that train of thinking, that a person should not buy a used machine period. all I am saying is it might be better to educate people on what to look for when buying a used machine, and what to do when you get it home to insure it is safe and ready to go. I know there are many good gyros out there flying around, and if one of them comes up for sale, and it is a good machine, then there is no reason just cause it is used that people should NOT consider buying it.
But telling us that we should not ever buy a used gyro is also saying under the same breath that we should keep in mind while building a new more expensive kit that we are building something that has no resale value since no one wants to buy our junk!

Ron, here's my take on buying used gyros. Again, we're digressing from the point about suspicious aircraft hardware. But it's fair to respond to your comments.

First off, I feel that someone new to the sport will get into the air faster and with less frustration by buying a new gyro kit. More money? Lots! This statement comes from the frustration of watching people spend years trying to get into the air with used gyros, not because the gyro kit manufacturers pay me to say it.

Should someone new to the sport buy a used gyro? Sure. But it would be like me buying a used Aqualung. I don't have a clue what to look for. So if you're new to the gyro sport, bring along someone with much more experience in gyros so you don't get stuck with a lemon. Pay that person to give you an expert opinion about the condition of the gyro before you buy it, and have the expert tell you if the price is right. Next, watch the gyro fly before you put your cash in its owner's hands.

A word about price. Generally you get no more than you pay for. If you pay $2,500 for a 1960s era Bensen, IMHO it's doubtful that you will have a machine that can actually fly. Ron, if you sold your gyro, you'd want a nice piece of cash for it. Why? It flies. It's maintained. It cost you a bunch of money to build. So I try to steer people away from a cheap gyro. By the time they fix it up into flying condition, they could have spent their money for a machine like yours, Ron--and be flying much, much sooner.

Let me throw in one last thing--about buying used gyros off eBay or from nationwide classified ads. Gyros for sale may be junk or they may be perfect, and I'm not slamming the honesty of the sellers. My question is, how do you know the difference unless you go INSPECT the gyro? Never buy a gyro unless you have inspected it. If you know as much about gyros as I do Aqualungs, don't buy it unless someone expert in gyro construction has inspected it for you. Even then, ask to see it fly.

The only possible exception I can think of to the above would be buying a used gyro from someone like Ron. I believe he has enough integrity that a potential buyer could take his word about the condition of his used gyro. And if there were any questions, Ron could fly his gyro when the buyer comes to pick it up and give Ron a certified bank check or cash money.

Good ideas, Ron. Tim O'Connor, if you read this, would you please add some words of wisdom?

[automan1223]

Guys,

I have bought a lot of (crap) off of ebay, some of my aviation stuff was really old 1 & 2nd gen ultralight hardware. I got an engine mount off of a rotec rally 2pl with a rotax. All the hardware had the chessy look and feel to it. I was suspicious.

since I had little background with an hardware, my new hardware I got from spruce was the real deal, however, every once in a while I get a bogus or miss stamped an bolt from spruce so it can happen from even the good places.
thanks for the heads up.

[automan1223]

I have a problem with that Ron,

80% of the hardware grade 8 is trash, made overseas and good for lawn chair uses. Only a good made in usa hwd mfg would get my dollars.

Lawson, Rockford, etc. are the ONLY off the shelf hardware I would use. Stuff at lowes and home despot is made in china crap.

Jonathan







The Dominator for the most part is assembled using plain jane hardware store Grade 8 hardware. The rotorhead and teeter bolt and even the Jesus bolt I believe is all Grade 8 hardware store stuff. What do you guys think of that?

Mine has AN bolts in place of the Grade 8's in certain areas but like I said the bulk of the machine is held together with hardware store grade 8 with no paper trail other than maybe a True Value reciept!

[automan1223]

Yeah, I wonder how many builders here are drilling holes with 1/4" drill bits from sears.

Jonathan

Counterfit parts, are rampant in the auto industry.

I have 3 jobs to redo because of defective sub standard parts.
It is criminal.......

[Jonvee]

Experimental aircraft must pass an airworthiness inspection done by an FAA employee or an FAA designee. I can guarantee that the Bensen-type gyro mentioned above would never have made it through such an inspection. With Experimental aircraft, there IS an intelligent human being (besides yourself) looking at the machine before it is allowed to fly. This is not a complete fail-safe, because the builder may make changes later on. But at least an Experimental aircraft starts off airworthy.


I would have to disagree Kerry. The FAA inspectors do not always know or care what you used to build your aircraft. You can build it from Swiss Cheese or Home Depot metal. I have never had an inspector try to trace my materials. If the inspector would have to sign off for the aircraft being airworthy then if it did fail the inspector could be held liable. It is up to the builder everytime. My inspectors have looked for obvious safety items such as sharp corners that could get the pilot and nuts that are not locked. Then they check your paper work. Total time looking at the gyro has been 10 minutes at the most. It would be easy to get an FAA inspected aircraft in the air that was not airworthy.

[Doug Riley]

A couple thoughts.

First, I have an older Air Command (a Fetters version). My experience is the same as Udi's -- it's loaded with "plain X" hardware as shown in the posted photos. AN bolts should have a symbol or initials indicating the manufacturer, so these are highly suspect. Over the years, I've replaced them all.

Air Command has had three owners. Only the current owners are really professional and competent. You have to be wary of older A.C. stuff from the "Florida guys" who owned the brand in the early 90's or from Fetters.

Second, as far as I've seen, Ernie at RFD uses only solid-triangle INFASCO Grade 8 bolts on Dominators. I believe these bolts to be reputable. I smacked a 28-foot set of DW's at full RPM a few years ago and the solid-triangle spindle bolt stretched and bent a bit. They must not be confused with the hollow-triangle bolts that are blacklisted.

Grade 8's, even the good ones, have long threads that are very inconvenient on an aircraft. You end up cutting them off in some cases, which leaves a naked end to rust on you. NAS bolts, OTOH, have extremely short threads that also are inconvenient. Like the Three Bears' beds, sometimes the one in between the extremes is just right.

Given that we're usually bolting through soft aluminum, the bolt isn't the weak link all that often on a gyro. AN bolts aren't expensive, however, they're nicely made and the threads are just right for what we're doing. It seems pointless to me to use anything else, except maybe for a field repair -- done cautiously and then re-done properly when you get home.

As for FAA inspections, Jonathan Vaghy is right. During the first inspection I had, the inspector said "I'm not here to protect you. If you want to strap yourself to a rocket and fire it off in the desert, I'll give you a certificate as long as you won't hurt the public."

[gyroguy]

I would have to disagree Kerry. The FAA inspectors do not always know or care what you used to build your aircraft...I have never had an inspector try to trace my materials. ...My inspectors have looked for obvious safety items such as sharp corners that could get the pilot and nuts that are not locked. ...Total time looking at the gyro has been 10 minutes at the most. It would be easy to get an FAA inspected aircraft in the air that was not airworthy.

Johathan, just a note. Agree, no FAA inspector is going to try to trace your materials OR check AN bolt heads for suspicious or counterfeit bolts. But put a shiny steel Grade 2 hardware bolt in your control system, tighten it with a split washer, and my FAA inspector would not let it get by.

When you say, "It would be easy to get an FAA inspected aircraft in the air that was not airworthy." -- that does not sum up my experience. Last FAA inspection I had took about 40 minutes looking at the gyro and added about 30 more items to my fix-before-flying list. I have nothing but good words to say about those FAA inspectors in Ft Worth. I think it depends on the luck of the draw--which FAA inspector you get. So far I have been lucky. Maybe you were not.

For those who have not seen Jonathan Vaghy's gyro, it's an award winner. Jonathan is probably too humble to say this, so I'll say it on his behalf. It is one of the best-built and most innovative custom designs around. He has a plywood tail that looks like fiberglass, it's so smoothly finished. Many little things, too, show great attention to detail.

Sure would be nice if you posted some pix, Jonathan.

Again, appreciate all the comments. This is a thread where lurkers can ask questions or share their knowledge. Enjoy the thread, try to stick to nut-and-bolts issues, and I'll be back to this thread in a week or two.

[gyroplanes]

The statement of "Airworthiness" is made by the applicant, not the DAR. The DAR function is to see that the aircraft meets the requirements for the issuance of the certificate.

I have been to several SUP (suspect unapproved parts) meetings and seminars by the FAA. I have not heard of SUP hardware. I suspect that counterfeiting hardware would be much like counterfeiting one dollar bills.

I have been purchasing aircraft hardware since before some of you were born and I can tell you that aircraft bolts vary in construction, plating and markings. Often from the same manufacturer.

I have a collection of hardware, from known sources, that have defects such as threads rolled on only one side of the bolt shank or no threads at all (the last was in a KB joystick kit)

My advise, "Know your source" and "Visually check your hardware before installation"

[Jazzenjohn]

I've never built an airplane but,
I think I would personally be far more concerned about the use of hardware store aluminum than grade 5 or 8 bolts. In most instances I've seen the steel bolt is likely to be far stronger than the aluminum it is bolted to. Ungraded hardware store aluminum is very weak. If someone was building and screwed up a part and went to the nearest Home Depot just for 1 little piece of Al instead of waiting for good stuff....

[GyroRon]

Kerry I understand your point and I agree.

1. Don't buy a old junker! If it is old and or cheap it probably has a problem or many problems

2. If you can't see it fly when you go to buy it, then don't assume your buying a flying aircraft, all you are buying is old used parts that may never fly. This is my approach to buying any aircraft I have ever bought. Alot of my friends are the same way, if the seller won't fly it, then walk away from the deal.

3. Never EVER buy off Ebay or anywhere else sight unseen, unless you know the seller and you have a chance to see the machine and see it fly before the sale becomes final.

4. If you don't really understand a gyro, then buy a new one or make sure you got a true expert there to help you look it over, and that goes for ANY used gyro, not just the old cheap ones.

5. Remember if you didn't see it fly, for any reason whatsoever, you are only buying a collection of parts and pay accordingly and plan to be busy making those parts fly - which may never happen!

Buying a old worn out 1965 Bensen that the builder had stored in a barn for the last 20 years and has since passed away and your dealing with his son in law.... Well it is not the same as buying a late model, modern gyro with a modern engine and blades and so on. Either way you need to have someone help you if your not very experienced yourself. If you got the money to buy new and still pay for lessons then that is the best way to go. If you just can't afford it, you CAN find a good safe used gyro for sale. Just gotta use your smarts when shopping for the right one.

[GyroRon]

Doug, so are you saying I should not have any worries about my butt being held up there by Grade 8's? I am not sure if all of them are from Ernie, some I bought myself from Lowes. What do I need to look at as far as markings go?

[Jazzenjohn]

Gr. 2 min 74,000 psi tensile str.
Gr. 5 min 120,000 psi tensile
Gr. 8 min 150,000 psi tensile
AN standard 125,000-145,000 psi
NAS high Str. 160,000 psi tensile
Gr. 10.9 (metric) 150,000 tensile
Grade 5 hex head cap screws have 3 radial lines
Grade 8 hex head cap screws have 5 radial lines

[Jazzenjohn]

6061-t6 ultimate tensile str 42,000 psi, yield tensile 37,000, shear 27,000
7075-t6 is 83,000, 73,000, 48,000
2024-t3 is 65,000, 45,000, 40,000
7075 and 2024 are stronger but more brittle and both have poor weldability.
Amazing that 7075 Aluminum is actually stronger than some steels!!

[KenSandyEggo]

As told by me many times here, my first DAR, who also inspected my gyro years later, was inspecting my Avid Flyer. When he was done, I mentioned that I thought he was going to do a safety inspection instead of just paperwork and placards. He told me, while pointing to the washer and dryer in my garage, "If you want to take the crate that one of those came in and attach wings, a motor and prop on it, I would have to sign it off. It's experimental." I don't believe they have any obligation to even mention a galvanized nut on a grade 2 bolt if they see it. Or if they do and say something about it, you can insist that's what you want to use. The Inspectors that do look it over well and make helpful suggestions are going beyond the call of duty and they're help is commendable.

[Jazzenjohn]

Do you think that's a personal decision by that inspector or a policy decision by the FAA?

[Cobra Doc]

The few FAA inspectors I know do try to help as much as possible. They pretty much know what they are doing. It's up to the builder to take their advice.
To clarify one other point, I'm the one that said I would not buy a used experimental aircraft. If want to take my chances with an experiment, I want it to be my experiment, not somebody elses. There are too many opportunites in the building process to take short-cuts or make changes "because it looks better". The A-10 is the perfect example that things don't have to be pretty to be the best! What is right for me may not be right for someone else. This is just the opinion of me and my freshly calibrated torque wrench.

[Allantat]

All you need to know...and then some...about Aircraft hardware.

http://exp-aircraft.com/library/alexande/hardware.html

Allan Tatarian
Fresno,Ca.

[Cobra Doc]

Can't get much more expert than Ron!

[John_Read]

Someone said earlier that "there is not much redundancy" in a gyroplane. I don't think that can be fairly said about the fasteners.

As for the bent spindle bolt: I trashed a set of rotor blades in an accident, I am ashamed to say. When the aircraft was repaired the inspector passed the rotor head as undamaged. When - some time later - I had to replace the rotor-head bearing, I found the spindle bolt - a genuine AN part - to be bent.

I would say an impact with the turf while your rotor is spinning is quite likely to bend the AN spindle bolt, even though the double redundant mast is bent into a graceful curve which must have absorbed most of the forces involved.

[Michael Stump]

One thing I'd like to add after I apologize for shoehorning myself into your conversation. Sorry. Now that I've said that, here's a great rule of thumb. All (non AN-type from reputable manufacturers) bolts, including Grade 8's, are dangerous in aircraft applications, except for those from the reputable places that can be traced. Why? Because their threads are cut with a cutter, not rolled, as on the real McCoy.

The cutting action leaves stress risers at the threads and this is where they tend to break. It doesn't matter what grade it is, because eventaully, breakage should be a concern not do to alloy strength as much as fatigue cycles with stress risers. A great example of what might seem like an insignificant stress riser is a scratch on a piece of glass. If you stress it, guess where it breaks! It doesn't take much of a scratch to make this happen (not unlike scoring and breaking bricks, too.).

If in doubt, simply use the real deal. You can inspect the threads under magnification and clearly see the difference once you know what to look for.

And by the way, Kerry mentioned that you can assume that if the hardware came from a reputable gyro manufacturer that it will be the real stuff. Not true. RAF is a great example. Ken, I know you can vouch for that, as I can because my RAF redrive had ZERO AN bolts in it when I received it from them. It was cheap, cut threaded crap. Especially scary are the non-AN rod ends they use on the pushrods....deadly!

Rolled threads eliminate stress risers and is precisely why you must always use aircraft bolts (they teach you all kinds of great stuff like this in A&P school). Yeah, they are a bit more expensive, but then what is your life worth to your family when you never make it back home from the airport next Saturday cuz you wanted to save $2.68?

[Brian Jackson]

Thanks, Michael. Do you know of or have any close-up photos that show the difference between the two (cut vs. rolled)? I'd like to know what to look for, as I do not posess any AN hardware for my gyro project as of yet.

Thanks,
Brian Jackson

[KDOG]

Man, thats scary. I only buy my AN hardware from either Aircraft Spruce or Wicks. I can't imagine putting parts from unknown sources on my bird... yikes.

[Jazzenjohn]

I disagree with your assertion that anything other than aircraft hardware is cut thread. virtually ALL hardware is rolled thread. It is not only better but it's cheaper to do and requires less metal on the capscrew. you can easily check whether a fastener has rolled threads or not by measuring the diameter of the unthreaded shank and the diameter of the crests of the threads. If the crests of the threads are larger it was rolled. As far as I know only all thread is cut.

[Doug Riley]

Most threads on even cheap hardware-store bolts LOOK rolled, in any event. There are persistent rumors that somewhere in the poorest countries of the world it's cheaper to bang out cut-thread bolts on a lathe than to make them properly. The story goes that these junkers make their way into the U.S. through the multinational companies that buy worldwide.

[Jazzenjohn]

I have cut many threads on lathes and I absolutely don't believe it. I'll believe poor quality steel or heat treating but not cut threads. I personally think that their is far more danger in using hardware store aluminum than using grade8 or even grade 5 bolts.
For instance

6061-t6 ultimate tensile str 42,000 psi, yield tensile 37,000, shear 27,000

Hardware store aluminum can be 3000 series

3003-h13 ultimate tensile str 19,000, yield tensile 18,000, shear 11,000

BIG difference!!!

[Doug Riley]

Cut threads certainly are weaker than turned ones, as I bet Jazzenjohn would agree. Even if the cut surfaces are perfectly smooth, you've chopped right across the grain of the metal, creating a thread that strips more easily (like the one on a wooden broomstick). In contrast, the thread-rolling process squishes into the grain lines so that they follow the contours of the threads without being cut.

An interesting side note is that the original Bensen gyro rotor head (pre-gimbal) used a machined rotor spindle instead of the simple 1/2" AN bolt that we see in today's heads. The bottom end of the spindle had 1/2" fine threads -- that were, naturally, cut on a lathe! The 1/2" "Jesus nut" engaged these cut threads just as the same size nut does today on spindle bolts. I never heard of one stripping and releasing the rotor from a gyro -- though some did fracture at the turned shoulders. A forging is better than a turned piece for this kind of item.

Yes, hardware-store aluminum is rotten stuff for anything other than decoration.

[gyroguy]

Regarding hardware store aluminum...
Or junk yard aluminum...
Or ANY aluminum that doesn't have mill marks on it...

Don't buy it for your airplane or gyro!

Several years ago I got some 1" x 1-1/2" x 1/8" wall aluminum tubing that was supposed to be 6061-T6, but had no mill markings. As soon as I drilled it, I knew it was too soft to be that alloy. As a result, it became the outer guide rails on my gyro trailer instead of airplane parts.

Aluminum tubing from a mill has "mill marks" down the length of the tube. These give manufacturer, alloy number, and temper. Typically in aircraft construction, 6061-T6 is the most common alloy. I have seen 2024-T3 used, and in areas where hardness is needed and brittleness is not a concern, 7075-T6.

As I recollect (but may be wrong) much hardware store alloy is 5052, with a low "T" number. This is the stuff of aluminum door frames, etc. Not mill marked in the hardware store, not for aircraft use. The 90-degree angle makes nice wheel chocks, and I have found some used for braces on older Bensen gyros.

One danger in using too-soft aluminum (i.e., hardware store aluminum) is bolt-hole elongation. This is the result of a steel bolt vibrating in an aluminum hole. Guess which wins, everytime? The softer the aluminum, the quicker the bolt hole elongates... and may eventually crack.

Kerry mentioned you can assume that if the hardware came from a reputable gyro manufacturer that it will be the real stuff. Not true. RAF is a great example. My RAF redrive had ZERO AN bolts in it when I received it from them...

Well, Michael, so much for "hardware from reputable gyro manufacturers"! What about aluminum parts? I am suspicious of any painted/ powder-painted/ anodized aluminum unless I know their source. The finish hides or removes the mill markings. I've seen parts that go into Air Command International, Dominator, and Butterfly gyros before they were anodized/painted... all I saw was good stuff. No personal experience with RAF or other kits.

I'll finish with three things. First, every hole made in aluminum must be deburred to prevent hairline cracks from forming. Second, a pencil should not be used to mark aluminum because of the carbon (graphite) in the "lead." Third, while aluminum does not rust, it does corrode. Moisture, dirt, and contact with dissimilar metals gives corrosion a place to start.

Will others please comment on alloys, temper, etc. of aluminum tubing, sheet, plate, etc.? I don't have my Alcoa book handy that has all the answers!