The International Cessna^® 170 Association

This is likely a "can of worms" but I believe that a -A engine with a 6-bolt cranks is no longer a -A...but is a -C engine and should have it's datatag restruct "ACC" per the TCM bulletin already mentioned. (By specification a -A has an 8-bolt crank, and if a 6-bolt is installed it no longer meets it's TC.) Of course, this requires a prop change and those matters both require a new basis of approval for intallation, hence the need for the TIC170A STC.

Hello - I just joined and was wondering if there was an update on the STC for the 0-300 6 bolt crank in the A&B model.

This is the scenario - I just overhauled my O-300B and get a call from the mechanic as he was working on the paperwork. Essentially he is telling me that the crank we installed is technically not approved. Sooo I need to find an STC.

Can someone provide some light on this issue for me? Also if the association offers an STC how do I purchase it?

Thanks,

Simon

Simon,

If I understand correctly you installed a 6 bolt crank in a 0-300B. And then you want to install that and a different prop and spinner on your A or B model. You are actually making two modifications. One to the engine and then to the airframe.

In effect you are changing that engine to a 0-300C. There is no STC to do this but it can be done by following the procedures outlined by Continental to change the engine to a C.

Then you can buy the Associations STC to install that 0-300C and the different prop and the spinner onto your airplane.

BTW joining this forum is not the same as joining the TIC170A in which there are dues involved. Get your mechanic to agree he can make that engine a C model then join the Association and buy the STC to hang the engine on your airframe. Cost of STC is $75 to members.

Bruce/Simon, what Bruce just said is not exactly right. The 0-300-B had the prop adjustment deal on it and the C does not. I'd have to go thru notes but if you lock the adjustment out you'd be legal. The E engine has controls (if I remember right) for a variable pitch control not like the B engine but thru the hub assembly. I also think you can remove/blank the adjustment lever off??? Bruce correct me if I am wrong here. The C-145-2H and the B are the only 2 with that prop deal (for the 2 position prop). So you would not be converting it to a C unless you either locked it out or blanked it off- Right Bruce??? Ron

I think Ron the lever is lock wired to the fine pitch position. That's what mine had and I think the crank would have had the oil passage and plug.

Ron, techically I'd think you have to remove the lever and install the blank plate to make the engine a true C model. Wiring it, does defeat the control but does not remove it.

One thing I did not bother to mention is that there is an STC to install a 6 bolt into a 0-300-A. I do not know if the owner is still living or not but at one time I think it was Ron who got a verbal from the owner that the STC was free to use by anyone. We may even have a letter to that effect I can't remember. I can't find anything right know and if we don't find a letter which very specifically states the STC is open for public use and it is signed and witnessed, I doubt the FAA would allow it.

Good thing I didn't bother to mention it as i remember wrong. This STC was to replace a 6 bolt with an 8 bolt in a 0-300-D. So disregard this info for this discussion.

The conversion from one engine model to another... such as a B to a C.... is NOT an STC. It is a TCM Service bulletin/letter.
It is a very simple matter as far as TCM is concerned. (Make the changeout, strike the dataplate, record it. Form 337, No Block 3 approval req'd.)

The STC which we own is merely to make the installation of a different model engine and prop (than an originals approved in the Type Certificate) into a Cessna 170.

As to whether or not it is necessary to wire the prop control lever to make it inop.... or if it's necessary to completely remove it... is likely a matter of the TCM SB for conversion. The other considerations (for practicality) are Prop/Spinner/Cowl-clearance issues.

Bruce's comments regarding conversion from a B to a C are predominantly correct.... the only major difference is the crankshaft/prop-flange. (Ron, an argument could be made for an infinite number of detail differences, but they are merely muddy-water, for instance, technically a "C" engine also requires Slick magnetos.... clearly a foolish distinction. (Little-known-detail: A "C" engine can also include the angle-drive starter motor which most folks incorrectly believe first occurred in the "D" model.)

One must be extremely careful with this mod/job. The FUZZ is known for checking the engine data plates and then pulling the spinners to count the prop bolts.

Bruce once pointed out (while acting as convention judge) that one does not need to pull the spinner to check the number of prop bolts. (All one has to do is look behind the spinner just exactly as one should do during every pre-flight and inspect them for security and count the lock-nuts if it's a 6-bolt.)

Thanks everyone. I will pay to join the association and then buy the STC to allow for the installation of the C in the 172.