The International Cessna^® 170 Association

Does anyone have a parts break down for the installation of the aluminum bushings to mount the engine mount to the firewall for a 52 170B? Will be installing a new engine soon and mounts at the same time.

Does this help? Top hat inserted from front side of firewall, washer slipped over from inside.

I am looking for an IPC the part numbers for the bushings.

That's because its not in any 170 book that I know of. It is actually a 180 part. I believe part number 0751004-1 and 0751004-2 are what you need.

There are a couple threads about these. I just can't find them.

mit wrote:There are a couple threads about these. I just can't find them.

Yea Tim. I started one about two months ago.....It ended with the Al Bushings being about 650.00 dollars as opposed to the rubber bushings at 70.00 dollars. You REALLY NEVER!! want to look at the engine mount bushings at the fire wall, ever again, to pay that much

Lopez wrote:That's because its not in any 170 book that I know of. It is actually a 180 part. I believe part number 0751004-1 and 0751004-2 are what you need.

If they are the same size as the rubber mounts they might be good candidates for owner-produced parts.

n2582d wrote:If they are the same size as the rubber mounts they might be good candidates for owner-produced parts.

I have PMA on a cargo pod for Cessna 185's and I am exploring the idea of expanding. One of the items I was thinking about producing are these bushings. I think I could build them and sell them for somewhere around $225-275/set of 4. Would anyone be interested at that price?

How hard would it be to get a PMA for these bushings if you had them made from polyurethane? The rubber bushings on my Volvo 740 suspension have been replaced with ones made of polyurethane. They would last a lot longer than the original rubber yet are dirt cheap -- $2.00/each from IPD.

n2582d wrote:How hard would it be to get a PMA for these bushings if you had them made from polyurethane? The rubber bushings on my Volvo 740 suspension have been replaced with ones made of polyurethane. They would last a lot longer than the original rubber yet are dirt cheap -- $2.00/each from IPD.

100839-sway-bar-end-link-bushing.jpeg

PMA is a funny thing. It requires that the part be IDENTICAL to the original part. Identical is this case includes material spec and construction/manufacturing methods. If you wanted to manufacture a polyurethane bushing, you would need an STC since it would not be identical to the original bushing. Once you obtained the STC (which is a fascinating and frustrating process), you would also need PMA on your own part. That essentially means that each STC'd part you manufacture will be identical to the original which the FAA approved.

One of my favorite examples of this is the P-Ponk gear box brackets. To be clear, I am referring to the replacement inner and outer brackets, not the gear box modification. These replacement brackets require an STC even though they are identical in terms of fit and function to the original Cessna parts. The reason they require an STC is they are machined from billet aluminum, while the originals are an aluminum extrusion, therefore not IDENTICAL.

The one that I quite frankly don't understand is Macfarlane seat tracks. They are a beefier track than original, but the DON't require an STC. All I can figure is they showed the feds that they were close enough to original (same material and construction process).

All of this, as usual on any forum, may be worth what you paid for it. This information also seems to change slightly depending on which inspector I talk to. Like I said, I have PMA on my own STC'd part. I've been through the process and have explored other potential parts markets. I talk to the FAA WAY MORE than anyone should have to and walk away more confused than when I started some days.

You could bypass all of this under the "owner manufactured parts" umbrella. I believe that wording there states "as good or better" than original. At that point you just can't sell it.

I have only seen a picure of those aluminum engine mount bushings, never the real thing, but they look quite simple to me. Unless there is something that does not show up in pictures of that part, it appears that any half competent machinist with a lathe and a micrometer caliper could make a set in no time at all.

BL-
Bingo!

FAA-PMA parts do not have to be "identical" in every respect to OEM parts.
STC is not necessarily required for installation of PMA parts. The point of PMA'd parts is ...they may be used as replacement parts for OEM parts. If the OEM part is legal for installation, the PMA part is as well.
An STC might be required if an OEM or PMA Cessna 180 part is used on an airplane other than a Cessna 180...or, in certain circumstances, a 170 seaplane part was used on a 170 landplane.
The applicability of PMA and STC differ in that PMA applies to parts manufacturing and sale...while STC would apply to installation of parts in an otherwise unapproved installation.

Does anyone have the dimensions for these bushings so I can get some made?

Yes I have the exact dimensions of these bushings. I removed them from a cessna 180 when the engine mount was off for inspection. It is on my list of things to machine. unfortunately that paper is @ my hangar and will take a day or two to get if you are interested. The urethane bushings also caught my interest, better that the rubber that we use now in my opinion .The last time I changed out the rubber bushings I had to reject 3 of the 8 items as they were poorly cast. so much for certified parts.

Bill CFZXO