Trying to locate correct part

[iflyvfr]

With all new seat rails installed I want to replace the floor fasteners for the seat belts in my Cessna 172G. The parts manual shows the assembly and the appropriate part numbers. I ordered them from A/C Spruce and the nut comes back not as NAS679A4 but as NAS679A4W. Took a chance and lost - it's not the right part.

I searched Cessnaparts[.]com and a couple other sites and called Spruce yesterday. Told me the W stands for 'internally wrenching' whatever that means. They are supposedly calling around to their suppliers for me. Any suggestions on where else I can look?

 

[Bell206]

NAS679A4 but as NAS679A4W

FYI: It's the same nut with the "W" version providing a feature to allow the nut to be driven at the internal hex edges as well as the external hex edges. The "w" actually costs more, so if you got it for the straight A4 price your ahead a few nickels.

 

[iflyvfr]

FYI: It's the same nut with the "W" version providing a feature to allow the nut to be driven at the internal hex edges as well as the external hex edges. The "w" actually costs more, so if you got it for the straight A4 price your ahead a few nickels.

I think you are saying, you can put them on either way? I cannot get them to thread by hand using the hollowed out side. But they will thread on the other way with the solid face toward the bolt head. This is correct then?

 

[iflyvfr]

If yes, then I'm headed to the hangar! Are they reusable in this manner? Cessnaparts says NAS679A4W NLA THRU CESSNA PRICE VALID UNTIL STOCK DEPLETED. A/C Spruce charged .79 each, the other site $2.08 per.

 

[Bell206]

I think you are saying, you can put them on either way?

No. One way only, solid side toward bolt head. Don't work too hard.

 

[Stewartb]

Odd question for a private owner doing supervised maintenance.

 

[iflyvfr]

Odd question for a private owner doing supervised maintenance.

Odd comment for a pilot in AK to post.

 

[kontiki]

The flat side threads on. The way this nut works, the top of the threaded bore is slightly distorted at the top end which is what makes it self locking. W or no W will not affect the strength. It is not a nut designed for strength when the bolt is in a tension load. It carries the load in shear. I think it's fine. Sometimes you see nuts just like this and the recessed area is filled.

 

[Bell206]

It is not a nut designed for strength when the bolt is in a tension load.

FYI: I think you'll find most NAS spec nuts are used mainly in tension/torsion applications as in the seatbelt mounts above.

 

[kontiki]

FYI: I think you'll find most NAS spec nuts are used mainly in tension/torsion applications as in the seatbelt mounts above.

I'd say no and no. Seat track in a Cessna rests on a floor. Weight tends to press down on track. Biggest load is shear. We used to call those nuts jap nuts years ago. Strictly low strength. I'm not a structures guy or a ME though. If you were in the neighborhood, I'd bet you a cold six pack. I work with structures engineers, but I don't know how familiar they would be with the Cessna seat track. Just saying.

 

[bluerooster]

With all new seat rails installed I want to replace the floor fasteners for the seat belts in my Cessna 172G. The parts manual shows the assembly and the appropriate part numbers. I ordered them from A/C Spruce and the nut comes back not as NAS679A4 but as NAS679A4W. Took a chance and lost - it's not the right part.

I searched Cessnaparts[.]com and a couple other sites and called Spruce yesterday. Told me the W stands for 'internally wrenching' whatever that means. They are supposedly calling around to their suppliers for me. Any suggestions on where else I can look?

View attachment 83806 View attachment 83805 View attachment 83804

Just for clarification, are you talking about bolt 57, and nut 59, or bolt 53, and nut 55? One is a tension load, and the other is shear load. Based upon the kit in the pic, I would suppose you are talking about 53 and 55. which is a shear load, where the bolt takes the load, and the nut simply keeps the bolt in place.

 

[iflyvfr]

It's bolt 53 and nut 55 with spacer 54 that is for the right seat belt bracket. I consulted with my mechanic and he did some additional checking and says the nut is appropriate. That's him pointing out the diagram and the part numbers in the manual so I could go order them. I've installed and removed the old style nut at least 2 dozen times under his supervision during annuals but this wrenching nut caught me by surprise when I went to order.

 

[Bell206]

Seat track in a Cessna rests on a floor. Weight tends to press down on track. Biggest load is shear.

OP is talking about the seatbelt hardware not the seat track. As for loads, most are tested in 4 axis not one pressing down, especially for seats and restraints. I think you'll find the biggest load for the seatbelt hdw is torsion/tension.

We used to call those nuts jap nuts years ago. Strictly low strength.

Call them what you want, but you'll find those NAS nuts are considered tension nuts vs shear nuts (low strength) which is why they're used for the seatbelt hardware. Matter of fact NAS nuts can be used as alternates to MS nut is certain cases. Just because the nuts are "hollow" doesn't mean they're low strength.

I'm not a structures guy or a ME though. If you were in the neighborhood, I'd bet you a cold six pack.

Perhaps you might check with your structural buddies first next time. And since your buying any nut-brown ale will work.

 

[Tom-D]

Call them what you want, but you'll find those NAS nuts are considered tension nuts vs shear nuts (low strength) which is why they're used for the seatbelt hardware. Matter of fact NAS nuts can be used as alternates to MS nut is certain cases. Just because the nuts are "hollow" doesn't mean they're low strength.

Be careful which nut you substitute. the track is close.

 

[Bell206]

Be careful which nut you substitute. the track is close.

???

 

[Tom-D]

???

The Cessna seat track doesn't clear the lap belt by much. I see the fat type often.

 

[iflyvfr]

The Cessna seat track doesn't clear the lap belt by much. I see the fat type often.

Yes, they are but manageable. As I was preflighting today I noticed those same style nuts are what's used on my aileron hinges. Funny the things you notice once the veil has been pulled back. Good God it felt good to think about aviation instead of you know what today.

Here's the installed part. This is the copilot's outboard attachment point with the new hardware.
Here's the pilot's inboard attachment point with the original hardware just to give you a different view. (Mostly I'm showing off $1200 worth of seat rails that no less that 6 people had a part in installing, there's a reason they are painted gold.)