The International Cessna^® 170 Association

George,

Sincerest thanks for putting that list together. I am planning to change the brakes very soon and want to take this opportunity to change out the axle bolts. Can you tell me which NAS bolts to use and a source for those bolts?? Do the NAS bolts come in 1/16 inch length increments in the event I add wheel pant mounting plates?? Also, is there a different nut for the NAS bolts?? Looked, but can't find NAS bolts in WAG AERO catalog and don't remember seeing them in A. Spruce. Thanks, chuck

The NAS bolt replacements for the original AN 5-23A (upper bolts)* is NAS145-41. The replacements for the original AN-6-24A (lower) is NAS146-42. The nuts are NAS365-624C and NAS365-524C.* You'll also likely need a few washers, NAS143-5C, and -6C. (see * below)
While NAS hardware is made to a higher standard as regards tension-strength, they are not absolutely necessary, IMHO. Either type hardware will need to be inspected occasionally for corrosion, which is the primary cause of failures.

CAUTION: Be very careful when removing/replacing axles that the axle shim relationships be noted, in order to avoid wheel-alignment problems. A simple way to do this is to mark the forward and upper, or aft/lower edges with a marker before removal...but even then it's still possible to accidentally reverse them inside/outside.

If you have any interest in installing L-19 tow-adaptors, now is also the time to install them. 0641102-1 left, and -641102-2 right. You'll need to add 1/8" length to the upper bolts, or delete the flat washers to accomodate the adaptors.

*HINT: While your bolts/axles are removed is also a good time to spend a little extra time with a magnifying glass inspecting for cracks in the bolt-holes in those lower gear legs. If your replacement axles are set up for 5/16" upper bolts and 3/8" lower bolts, now is the time to drill and radius the edges of the upper bolt holes in your gear legs (to make them both 3/8" holes.) In such case, you'll need to change the upper bolts to NAS146-41 and the upper nuts to NAS365-624C, and the appropriate washers are NAS143-6C.

Aircraft Spruce 877-477-7823 http://www.aircraftspruce.com/ or Genuine Aircraft Hdwr 888-247-2738 http://www.gen-aircraft-hardware.com/ . should be able to assist you.

Fantastic......as always, manny thanks for the info.

Fortunately, the only handling difficulties with this a/c to date have been pilot induced , so you can be sure I will take every precaution to maintain the current alignment.
chuck

gahorn wrote:The NAS bolt replacements for the original AN 5-23A (upper bolts)* is NAS145-41. The replacements for the original AN-6-24A (lower) is NAS146-42. The nuts are NAS365-624C and NAS365-524C.* You'll also likely need a few washers, NAS143-5C, and -6C. (see * below)

The NAS145-41 has been superseded by MS20005-32 (about $7ea) and the NAS146-42 has been superseded by MS20005-31 (about $22ea). I agree with George, unless your putting the aiplane on skis or tundra tires, I'd stick to the AN hardware.

Thanks, Karl. But I don't agree that the NAS have "superceded" to MS numbers... they do have corresponding MS numbers, however.

By the way, folks.... the NAS/MS series have slight radius beneath the bolt head. Therefore the landing gear leg holes should also be confirmed as having been radiused to match. (This radius is also necessary to prevent the sharp edge of the bolt holes from propagating cracks...an important thing to remember should you drill out your old 5/16" upper holes to 3/8" to match later axles.)

gahorn wrote:Thanks, Karl. But I don't agree that the NAS have "superceded" to MS numbers... they do have corresponding MS numbers, however.

While that is true, Genuine Hardware list the NAS numbers mentioned above as "superceded" just as you brought up in a previous thread regarding the washers, ( http://www.cessna170.com/phpBB2/viewtop ... 5473d8ca07 ) you can still find these listed under both numbers. This seems to be how they are listing hardware now, if a MS number exist, thats how they catalog it.

Under "Tech Info" it states the following for the NAS144-158 bolts: "INACTIVE FOR NEW DESIGN AFTER OCTOBER 1, 1986, USE MS20004 THRU MS20024".As best as I can tell the NAS146 bolts are not made anymore or made in very small numbers, thus the high price. Which brings up a question. Why not use the NAS6205 (superceded from the NAS1105) bolt which is the hex head version of the "internal wrenching" MS20005/NAS146? These are much cheaper.

lowNslow wrote:

gahorn wrote:Thanks, Karl. But I don't agree that the NAS have "superceded" to MS numbers... they do have corresponding MS numbers, however.

While that is true, Genuine Hardware list the NAS numbers mentioned above as "superceded" just as you brought up in a previous thread regarding the washers, ( http://www.cessna170.com/phpBB2/viewtop ... 5473d8ca07 ) you can still find these listed under both numbers. This seems to be how they are listing hardware now, if a MS number exist, thats how they catalog it.

Under "Tech Info" it states the following for the NAS144-158 bolts: "INACTIVE FOR NEW DESIGN AFTER OCTOBER 1, 1986, USE MS20004 THRU MS20024".As best as I can tell the NAS146 bolts are not made anymore or made in very small numbers, thus the high price. Which brings up a question. Why not use the NAS6205 (superceded from the NAS1105) bolt which is the hex head version of the "internal wrenching" MS20005/NAS146? These are much cheaper.

In that post I was specific in mentioning that certain hardware mfr's use the term "superceded" when suggesting an MS part to be substituted for an NAS part. I'm not trying to be argumentive... I'm only trying to be correct in terminology useage. (which sometimes can be misleading if incorrectly used...example: "superceded" implies that a part number has fallen into obsolescence due to a better/improved part mfr'g process. In the case of the hdw mfr's claiming that a certain NAS part has been "superceded"...in fact what they are saying is that they do not carry the NAS part and are offering a possibly corresponding MS part as a substitute.... the MS part they are suggesting has NOT been "superceded" in the specifications of the OEM at all. IF...and WHEN.... Cessna declares the NAS bolts to be obsolete and then changes their specifications to MS parts.... only THEN may the MS part no. be properly referred to as having "superceded" the NAS part.)
This can be a critical distinction in certain applications. As, for example, with the "hex head" difference in the MS part you questioned versus the originally specified NAS part which has an internal-wrenching head. There are very real reasons a mfr such as Cessna might specify the internal wrenching NAS bolt. It may be that the hex-head MS part cannot be properly torqued using a hex head due to adjacent structure. A possible example I can give is the NAS internal wrenching bolts used to hold the vertical stabilizer angle attaches. That angle has a radius to it which precludes putting a socket onto a hex head....only an internal wrenching NAS bolt will be capable of being properly torqued in that critical application. It would be a mistake to take some hardware mfr's word that the NAS bolt had been "superceded" by some hex-head MS bolt.
(In this case it may not be why they specified it...I'm just offering one example of why such a substitution may not be applicable.)

Again, this is not an attempt to be argumentive. It's only an attempt to keep us all as correct as possible.

N170CT wrote:George,

Sincerest thanks for putting that list together. I am planning to change the brakes very soon and want to take this opportunity to change out the axle bolts. Can you tell me which NAS bolts to use and a source for those bolts?? Do the NAS bolts come in 1/16 inch length increments in the event I add wheel pant mounting plates?? Also, is there a different nut for the NAS bolts?? Looked, but can't find NAS bolts in WAG AERO catalog and don't remember seeing them in A. Spruce. Thanks, chuck

By the way, Chuck... did you happen to notice in the TradeMart that one of our fellow members has a set of these NAS bolts for sale?

gahorn wrote: IF...and WHEN.... Cessna declares the NAS bolts to be obsolete and then changes their specifications to MS parts.... only THEN may the MS part no. be properly referred to as having "superceded" the NAS part.)
Again, this is not an attempt to be argumentive. It's only an attempt to keep us all as correct as possible.

Understood, I consider it more of a debate.
Cessna does not determine AN/MS/NAS standards. And I doubt Cessna reviews their parts manuals to determine if the hardware specs have been superceded. They still list AN O-rings which are only available under a MS spec is an example. Also 43.13 states:

7-46. INTERNAL WRENCHING BOLTS
(MS20004 THROUGH MS20024) AND SIX
HOLE, DRILLED SOCKET HEAD BOLTS
(AN148551 THROUGH AN149350). These
are very similar to the bolts in paragraph 7-45,
except these bolts are made from different alloys.
The NAS144 through NAS158 and
NAS172 through NAS176 are interchangeable
with MS20004 through MS20024 in the same
thread configuration and grip lengths. The
AN148551 through AN149350 have been superseded
by MS9088 through MS9094 with
the exception of AN149251 through 149350,
which has no superseding MS standard.

So why pay $44 for that NAS when you can use a $22 MS?

While you make a good point about the hex head NAS, I'm not sure it applies here where Cessna has also listed hex head AN hardware as a option.

lowNslow wrote:

gahorn wrote: IF...and WHEN.... Cessna declares the NAS bolts to be obsolete and then changes their specifications to MS parts.... only THEN may the MS part no. be properly referred to as having "superceded" the NAS part.)
Again, this is not an attempt to be argumentive. It's only an attempt to keep us all as correct as possible.

Understood, I consider it more of a debate.
Cessna does not determine AN/MS/NAS standards. And I doubt Cessna reviews their parts manuals to determine if the hardware specs have been superceded. They still list AN O-rings which are only available under a MS spec is an example. Also 43.13 states:

7-46. INTERNAL WRENCHING BOLTS
(MS20004 THROUGH MS20024) AND SIX
HOLE, DRILLED SOCKET HEAD BOLTS
(AN148551 THROUGH AN149350). These
are very similar to the bolts in paragraph 7-45,
except these bolts are made from different alloys.
The NAS144 through NAS158 and
NAS172 through NAS176 are interchangeable
with MS20004 through MS20024 in the same
thread configuration and grip lengths. The
AN148551 through AN149350 have been superseded
by MS9088 through MS9094 with
the exception of AN149251 through 149350,
which has no superseding MS standard.

So why pay $44 for that NAS when you can use a $22 MS?

While you make a good point about the hex head NAS, I'm not sure it applies here where Cessna has also listed hex head AN hardware as a option.

Quite right, Cessna does not determine AN/NAS/MS standards.... they only determine WHICH of those are the correct part numbers to use on their products. Some hdwr maker somewhere does not have that luxury and therefore should not make claims that the OEM's specified part number has "superceded" to something else simply because that's what the hdwr mkr happens to have "in stock".
Also,...it might surprise some of us to know this, but.... even the GOV"T makes mistakes. Simply because the GOV'T has approved an MS part as a replacement for a previously mfr'd NAS part... does NOT make it a "superceded" part in the eyes of the OEM. That determination is likely...but not necessarily the case, until the OEM is consulted or other approval basis is provided. (It may be as simple as meeting the "equal to" provision of FAR 43,... but that does not automatically qualify it as a superceded part.) Once again...the correct term to use (IMHO) is "substitute part", etc. ... at least until the OEM revises their documentation.

Also, notice that the para. 7-46 referred to only discusses internal wrenching bolts. They do not offer or suggest a corresponding hex head is a replacement for those bolts.
We are in agreement as regards hex head bolts in this application. As I previously stated, I can't imagine that a hex head bolt wouldn't be applicable here in any case. Both the NAS and the MS standards exceed the AN standards for tensile strength and, as you noted, AN hex heads already fit this application.

Thanks George. If nothing else these discussions get me back into the books which as an A&P, I must admit, I don't do often enough.

By the way the NAS standard is not a government stantard but an industry standard overseen by the Aerospace Industries Association (AIA). They will sell you the hardware specs for a hefty price if you wish to manufacture them. The tech specs which Genuine Aircraft Hardware list are copies of these to which they have attached their letterhead.

George,
Yes, I did see that ad in our Marketplace. Just felt that was a little too much for me right now. May have to stick to the AN series hardware if the NAS is that expensive. Of course, the gentleman is in Nova Scotia and perhaps his price is in $Cdn. but that was not specified.
Thanks for the heads up.
chuck