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Fastener Standards for aircraft components

Fastener Standards for aircraft components

(OP)
Hi all,

1) As far as I concern, the most common fastener standards used in aerospace application are coming from either National Aerospace Standard (NAS), Army-Navy Aeronautical Standard (AN) or Mil-Spec (MS). Is it acceptable to use other fastener standard available out there such as DIN, ISO, ASTM and etc? If yes or no, is there any requirement outline there from CS, FAR or AC that outlined this.

2) Is it a good practices to have multiple fastener standard in one common aircraft component assembly? For example, certain component attachment using NAS and other attachment using AN standard.

3) Let say if I want to stick on one fastener standard (eg: NAS) Where is the best resources online to get fastener geometry specification (diameter, thread size and length). And also is it possible to obtain the fastener mechanical strength properties through online resource without engaging with the manufacturer / supplier at the first place.

Thanks in advance for the responses.


RE: Fastener Standards for aircraft components

Ad Jam... wow... I am head-scratching as-to-where-to start with a response.

You are a new member, I see, so there is work to be done on Your part! So, I'll make a few suggestions where to start... and suggest topics/issues/questions You need to think about... then we'll talk.

First: You have to understand the basics of aerospace fasteners: what they are how they function, where mechanical shear and tension allowables [tables] are located??? NASA RP-1228 Fastener Design Manual [Google-it] is a good start.

Also, suggest searching Eng-Tips aero forums for 'fasteners, rivets, bolts, etc...'. A LOT has already been stated on this subject. there are also many other forum have addressed questions for 'all fastener types' which may/may-not be useful

I suspect that logistics and cost/value will also be a major contributing factor in this answer.

What types of fasteners are You considering?
Shear Bolts/nuts*
Tension bolts/nuts*
tension screws/nuts*
Lock-bolts/collars
Hi-Loks [and all related new generation families] of Pins/collars
Solid rivets
Blind Rivets
Blind Bolts and/or nuts
Blind Rivets
bushes [bushings]
etc
[* and nutplates, threaded inserts, tapped holes, etc

For aircraft type... homebuilt? general aviation? commercial aviation? military? UAV?

For primary airframe structures?

Who is going to do the fastening/joining/inspecting work?

Also, what standards will you be using for everything else, such as: aircraft structures materials/finishes, fastener materials/finishes, hole sizes/tolerances [for both nominal and oversizes], fastening procedures and tooling, use of auxiliary fastener devices [washers, cotter-pins, lock wire, bushes, etc], inspection procedures, parts record-keeping, etc.

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

RE: Fastener Standards for aircraft components

If this is for a 3rd party repairs & modifications for a particular type / model, I would suggest starting with that aircraft's IPC so as to add as few as possible additional hardware part numbers.

RE: Fastener Standards for aircraft components

To answer your question regarding federal regulations, you have not told us what type of aircraft you are concerned with, or if you are dealing with initial design or repair & mods. If I assume you are working transport category aircraft, there are no specific specifications allowed or barred. However, there are several relevant regulations like 25.603 which mandate that all the materials used have suitable durability based on test or industry standard. This is very important and something you should become very familiar with. You need to know the regulations and where to review them.

I'd say honestly the best resource for specs would be from colleagues. As far as strength, the NAS and MS specs will give you the geometry and most usually list the Fsu of the fastener. Some will give general joint strength values but in my experience not always. This is where tests come into play. Stick to your four modes of failure for a mechanically fastened joint which are easy enough to calculate if you know the fastener and sheet materials and geometry. For example, the MMPDS has some joint strength values but these are just based on the material shear strength and shearing area of the fastener. Often times strength is based on transitional strength which comes from testing. SRMs are your friend.

Not sure why you would mix and match types but I have seen OEM drawings calling our MS fasteners and OEM designated fasteners (BAC) in the same structure. Again SRMs are your friend and will usually call out direct acceptable fastener substitutes.

Keep em' Flying
//Fight Corrosion!

RE: Fastener Standards for aircraft components

Here is where I would look up the NASA fastener design manual, referenced above:
https://ntrs.nasa.gov/

One more resource for you:
http://quicksearch.dla.mil/
In the search field, look up "MIL-HDBK-5J"
It's a huge download (about 75 megs) but it's basically the bible of material strength properties.

(PS. I could add a page of other thoughts and opinions about another document called "MMPDS" but I think you should start with the free download, and work your way outward. The MMPDS costs about 900 USD to purchase from the authorities, when you're ready to do so)

STF

RE: Fastener Standards for aircraft components

Ad Jam,

In the modern US aerospace industry everything is done according to controlled procedures (like AS9100) in order to ensure the finished product is reliable, meets all performance requirements, and has consistent quality. When designing your aerospace product you are free to specify any fastener you like, as long as it meets all requirements of the contract spec and your company QA system. Some large OEMs like Boeing have their own internal standards for fasteners. There are also companies like SPS or Alcoa that produce their own standard fasteners that conform to aerospace QA requirements.

Whatever standard fastener you specify, make sure it will be readily available throughout the service life of the product.

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