NAS 146A-43 Engine Mount Bolts

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NAS 146A-43 Engine Mount Bolts

Post by 7313 » Fri Jan 04, 2019 7:01 am

Does anyone know of a source for these seemingly hard to find bolts? Internally wrenched to fit inside the "holes" in the motor mount. When we bought our project most everything was there, but apparently not these bolts.

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Re: NAS 146A-43 Engine Mount Bolts

Post by 6643 » Fri Jan 04, 2019 8:15 am

Are these for the mount to engine or mount to firewall? Judging by the size, I'm guessing the former. There's an AD, 46-44-05, on that, which may be why you didn't get the bolts. The problem is the bolt heads were pulling through the mount and the engine coming loose. This can ruin your whole day. See Cessna SLN-18. If the ID of the tubes the bolts to the engine go into is about .600 inches then the AD applies.

If your mount has 3/8" tubes for the bolts then the correct bolts are AN6-46 upper and AN6-34 lower.

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Re: NAS 146A-43 Engine Mount Bolts

Post by 7313 » Fri Jan 04, 2019 5:27 pm

Thank you John. I reviewed AD’s back in 2011 when we started this project but totally forgot about this one. So now instead of looking for those bolts, we are looking for those special washers. I wonder if there is any source for those? My co-owner’s husband has machine tools so we may be looking at some lathe work for him.

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Re: NAS 146A-43 Engine Mount Bolts

Post by 6643 » Fri Jan 04, 2019 8:36 pm

Yeah, good luck ordering them from Cessna! Easy enough to turn on a lathe, though.

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Re: NAS 146A-43 Engine Mount Bolts

Post by 7313 » Sun Jan 06, 2019 1:27 pm

Now that I am on the right track, looking for washers instead of bolts, I will start a new topic with a more accurate Subject. Thank you all for the help.

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Re: NAS 146A-43 Engine Mount Bolts

Post by 7313 » Mon Jan 14, 2019 8:22 pm

Believe it or not, another course reversal. Our serial number, 10038, falls outside the range of the AD. Apparently because Cessna changed the thickness of the four plates on the front of the mount to beef it up and make the AD and SL change, with the shoulder washers, unnessary. So, still looking for the NAS146A-43 bolts. Any help appreciated.

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Re: NAS 146A-43 Engine Mount Bolts

Post by 6643 » Tue Jan 15, 2019 7:57 am

Measure the thickness of the washers welded to the front of each engine attachment point. If they are .049 then the AD applies. It would not be surprising to find that you do not have the same mount the plane rolled off the assembly line with.

NAS146A-43 bolts have been superseded. The (closest) current number is MS20006-32. The MS series is not available with holes in the shank for a cotter pin. So, your options are: find some obsolete bolts, buy the MS part and drill the shank, or follow the procedure in the AD and use cheap, readily available AN6 bolts.

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Re: NAS 146A-43 Engine Mount Bolts

Post by 7313 » Tue Jan 15, 2019 9:38 am

Thanks for the reply. You are confirming the conclusion I have come to. I measured the plates on the front of the tubes and they are about .1 inch, plus or minus a bit of paint. This led me to the conclusion that Cessna beefed up the mount at some point, and that is why the AD does not apply to our airplane. So if I just had the NAS bolts or equivalent, that is the easiest course of action. Thanks again for the clear explanation.
Last edited by 7313 on Thu Jan 17, 2019 7:17 am, edited 1 time in total.

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Re: NAS 146A-43 Engine Mount Bolts

Post by 6643 » Tue Jan 15, 2019 3:00 pm

7313 wrote:
Tue Jan 15, 2019 9:38 am
So if I just had the NAS bolts or equivalent...
Unfortunately, the only equivalent is the MS20006 bolts with custom drilled shanks. Given the likely cost, I'd go for having the stepped washers made and use AN6 bolts per the AD.

Just did a quick search. I found 3, at 3 different places. I'll ask a buddy who has access to a better database.

NAS146A43.jpg
NAS146A43.jpg (48.11 KiB) Viewed 320 times

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Re: NAS 146A-43 Engine Mount Bolts

Post by 6643 » Wed Jan 16, 2019 7:39 am

Jay-Tex Aviation 903 572-3688 Reportedly has 7. $60 minimum order.
Air Cargo Carriers 414 482-1711 x 7188 reporting 11 available.

Both New Surplus.

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