Bolt Kit for a 170

[c170b53]

George I've learned much about corrosion during my career mainly from exposure to numerous specialists and fellow employees But I think I owe more to the many old hands that were willing to put up with someone who needed ah.. direction. Sharing information like this amongst ourselves can only help more owners understand the consequences of ignoring standard practices. I've seen the revolution in aircraft construction techniques and material selection which has diminished the amount of corrosion in a plane but manufacturers have yet to eliminate. Its obvious that how we store, operate and maintain our planes will determine how long the plane will last. Corrosion will be the factor that removes an airplane from service permanently. Replacing hardware that has corroded is a just a common sense approach but more importantly its part of a larger philosophy to maintain aircraft to a planned schedule according to standard practices. Those practices have been learned from the experiences of many others to benefit us, so it might be a good idea to follow them.

[Brad Brady]

Hi Brad,I find these fittings corroded I don't necessarily get alarmed enough to take the entire aircraft apart unless further inspection warrants it. This is because 99% of the aluminum in these planes is 2024 roll formed clad, which is not nearly as susceptible to corrosion (especially innergranular) as the 7075 extruded spar cap angles and wing attach fittings which (1) do not have the protective clad (2) the extrusion manufacture process, in my opinion, wasn't then and still is not a perfected method and allows impurities and sometimes voids which can lead to problems.
Del,

Yea I agree with your ideas....Why I would suggest....(just that)....that I take the aircraft down....is that I need to pull all the flying surfaces, in order to balance them. The Empanage is no more than another ten to fifteen bolts......about two hours disassembly time... The other perk is I can strip every thing on a table.....no working on my head to get something done.....you Know what I'm saying... The other perk is that I can paint EVERYTHING...no missed places...every thing is painted...from stem to Stearn....and it also gives me more inspection avenues....just my thoughts.......Brad

[ginbug92b]

In checking my plane for the correct hardware I see that the correct NAS145 bolts are installed ( IPC figure 13 items #5 and #7 ) however mine are installed what I would consider to be upside down. The bolt heads are on the bottom with the nuts in plain view on top. I cannot tell from the IPC drawing which is the correct way they should be oriented. My questions are 1. am I legal and/or safe with it like this? 2.are there special radiused washers that must be used with these NAS bolts, and if so what is the proper part number so I can get them.

[wingnut]

In checking my plane for the correct hardware I see that the correct NAS145 bolts are installed ( IPC figure 13 items #5 and #7 ) however mine are installed what I would consider to be upside down. The bolt heads are on the bottom with the nuts in plain view on top. I cannot tell from the IPC drawing which is the correct way they should be oriented. My questions are 1. am I legal and/or safe with it like this? 2.are there special radiused washers that must be used with these NAS bolts, and if so what is the proper part number so I can get them.

Both inboard bolts, left and right, can only be installed with heads down. I've never seen the outboard bolts installed heads down. I think the nut being on top, at the outboard locations, would cause the same problem as a standard AN bolt head; the nut being the same size as an AN bolt head does not give adequate clearance on the milled (spotfaced) area around the bolt hole. The internal wrencing bolt head does not have a hex design, it is round and uses MS20002C5 washer with countersink area against the head. FYI The NAS145-14 supercedes to MS20005-5, and the NAS145-18 supercedes to an MS20005-10.

[N4027v]

Clearly my 1948 170 has incorrect bolts in the vert stabilizer if the pics in earlier post have the correct ones. I know this is an old post but wonder if anything ever came of Del's offer to put together a fastener package for 170's? Where can I get the correct bolts for my stabilizer bracket and is there a part number? Also, would the incorrect bolt as in my picture cause damage to the bracket? Does it need to be replaced just because wrong bolt was used?

[GAHorn]

Clearly my 1948 170 has incorrect bolts in the vert stabilizer if the pics in earlier post have the correct ones. I know this is an old post but wonder if anything ever came of Del's offer to put together a fastener package for 170's? Where can I get the correct bolts for my stabilizer bracket and is there a part number? Also, would the incorrect bolt as in my picture cause damage to the bracket? Does it need to be replaced just because wrong bolt was used?

Yes, standard AN bolts can damage the angles and that is what this discussion thread is all about.
You should replace those with NAS bolts and radiussed washers as mentioned in this thread.

[N4027v]

I have searched aircraft spruce and others for the part numbers listed in the thread but cannot find a match. Where can I find the bolt, washer, and nut?

[GAHorn]

MVC-002S.JPG (23.4 KiB) Viewed 26360 times

The NAS145-18 (and it's equivalent the MS20005-9) can be found at the Genuine Aircraft Hardware Company, 888 247 2738 or at
http://www.gen-aircraft-hardware.com/default.asp

They can help you find the associated MS20002C5 washers as well.

There are actually FOUR such bolts which attach the vert stab., so you will need TWO each of the NAS145 -18's and TWO each of NAS145-14's (or the MS20005-9 and MS20005-6 equivalents)

See: http://www.cessna170.org/forums/viewtop ... 45+#p68259

If you contact Del I'll bet he can send what you need. Here's what he posted in the above thread (note that he feels a slightly different length is better):

Aft spar vertical fin attach hardware. NAS145-14 supercedes to MS20005-5 and installs in the inboard holes heads down. NAS145-18 supercedes to MS20005-10 and installs in the outboard holes heads up. MS20002C5 washers install under bolt heads with chamfer
toward bolt head. AN960-516 washer under nut. Torque nuts to 100-150 in/lbs.
Forward spar vertical fin attach hardware. Bolt heads aft, washer under nut, torque nut to 50-70 in/lbs
NOTE#5A: The aft spar attach bolts are among the most critical on the
aircraft with respect to hardware orientation and torque. Much damage
can be done, and structural integrity compromised if done improperly.
I recommend removing all four bolts, clean and inspect fittings and bolt
bores with a strong light. Make sure holes appear round, not oblong, and
fittings are free from rough edge and burrs.
NOTE#5B: When satisfied all is good, install all 4 bolts, washers and nuts,
and then tighten so there is still slight movement of the attach point. Now,
replace the forward spar attach bolts, paying attention to the shim
arrangement in case one falls out. After forward spar hardware has been
replaced and torqued, come back and torque the aft spar using a step
torque method. I recommend snugging them all, then torque in 20-25 lb
increments until specified torque is reached. These are very high strength
bolts and is very easy to over torque, so make sure you have a good
calibrated torque wrench. The fittings will fail before the bolts if damaged
from over torque.
NOTE#5C: After old hardware is removed, inspect bolt holes with a good light source. Cleaning is desirable, using either MEK, Acetone or mineral spirits with a bore brush that has either nylon or brass bristles.
NOTE#5D: New hardware and bolt holes should be coated with a
corrosion preventative such as LPS-3, Corrosion-X, ACF-50 etc. I
prefer LPS-3 because it is a thicker viscosity.
NOTE#5E: Torque values given are from Cessna 100 Series Service Manual, and are for oil-free (non-lubricated) threads. Try to keep the threads dry, however if corrosion preventative is used and gets on threads, use the lower figures of the torque range listed.

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[lowNslow]

George, it looks like you and Del disagree as to the correct MS equivalent in the above post?

[GAHorn]

I used an "conversion chart" from Gen Av Hardware. Del probably used the next size longer which doesn't make much difference since it's only 1/8" and is taken up by washers anyway.

[wingnut]

The conversion charts you might see published by a hardware store are not always correct. I recall that the lengths that George posted did not satisfy the grip requirement. It's been awhile. I will double check tomorrow on these particular bolts. It seems the NAS to MS conversion provided by most sources did provide a bolt with the same, or very near, overall length. However the grip length was not correct, and in this particular installation grip length would be the criteria to go with.

And yes I did get very near offering a structural bolt kit for these planes. Because of supercedures in part numbers, and the lack of available OEM data for installation instruction, it was necessary for me to provide instruction with my kit. I talked to my attorney and he suggested I was taking on to much liability. The OEM publications are not 100% correct. If you notice there are not many correct call outs for washers. It's obvious that 60 years ago the manufacturers took the position that assumed a mechanic had common sense, and this is still true 95% of the time. Its the other 5% that would concern me. It is possible to get confused no matter how good instructions are, and it is possible to incorrectly install, sequence torque and cause a potentially catastrophic failure. It is my opinion that these 4 bolts that fasten the vertical stab and the fittings they go thru are the most critical on the entire plane. My kit and instructions went far beyond any other available data, and in fact was contradictory in some cases. If anyone needs help with specific hardware and/or installation in a specific area, I will be happy to discuss but I can't sell a complete structural hardware kit/instructions.

If you have a plane that has had incorrect hardware installed at these vertical to horizontal stab attachment fittings, I recommend a very good inspection of the fittings before installing the correct hardware.

[Poncho73]

I did a search before I asked the question regarding alternate aft vertical stabilizer hardware, that is why Im replying to this older post. Installation of the original NAS145-14 (2) inboard location is not possible due to the way the original attachment was assembled. Upon disassembly last month different hardware, I traced it back to when the vert stab was reinstalled back in the 70’s, the mechanic used AN5-6A bolts (bolt head down or inverted). Here is a picture of the issue and why the inboards are heads down. Also the inboard side doesn’t have the same radius as the outboard so AN960 washer will be fine and won’t cut into the angles. The pic shows only the outboard NAS in place, untorqued. It’s about 0 degrees F today and the hangar is reluctant to warm up. Finish another day.

[Poncho73]

View of the aft stab attachment showing why there is no way to install the original inboard bolts head up,. NOTE: the stabilizer is positioned upside down for the picture.

[GAHorn]

Although not “approved”…the IPC illustration appears to indicate the AN365-524 nut is UP in that inboard position. If you look at it closely you can see that there is no way to insert a tool into the head of the NAS bolt in that inboard position …UNLESS the bolt is installed upside-down. That is also how mine is installed (not that that proves anything… but it was installed by a Cessna-Textron group of employees if that carries any weight.)

It is good that you’re installing the correct hardware…that is an especially important and highly stressed area…and should be regularly inspected for cracks and any indication of impending failure…including EACH PRE-FLIGHT inspection.

[Poncho73]

Yes and it’s impossible to install any bolt regardless of type back into the inboard position with the head on the top surface. I have new NAS145-14 and -18.