Has anyone ever looked into the Type Certificate engine options for the 260C, and whether the turbo and non-turbo version of our extended hub engines are interchangable without an STC?

It appears that the TCDS clearly shows the IO-540-R1A5 as an option, with the only stipulations being:

-you must install with Rajay Turbos
-you must install per Piper Drawing 27137(basically all the turbo stuff)

If this is true, then you would in theory be legal to swap out an IO-540-R1A5 with all the normalizing of a 260TC, for the IO-540-N1A5 with all the aspiration of a 260C. With only a 337 and a signature in the log book.

Of course, this means you have to find a firewall forward to purchase. Then you would have to either overhaul that R1A5, or get a shop to convert your N1A5 to that dash(oil cooling for pistons, compensation in injectors for slight boost).

Just think, assuming you had all the plumbing and wallet, you could have a TC without the STC... turbo conversion without the conversion.

Any thoughts?

The bigger question is why? You would be destroying one of only a couple of dozen turbo C's made at significant cost. I think if you want a normally aspirated C, why not sell yours and buy one? I think that would be cheaper. Aside from the engine swap, you will have to change gauges and markings, removing the wastegate control lever, leaving a space there for all to see. If you hired me to do such a job I would estimate at least 10 hours of billable shop time chasing parts which are no longer readily available, if at all. When you are done, you will end up with a C model that is worth less than a normal C model because it will have been converted.

What do you think would constitute enough information in the TCDS, and what is the gauge change you refer to?

I'm mostly concerned with my read on the Type Certificate. I'm not as wise as the lawyer guys(or ladies).

The gauge I was referring to are the manifold pressure gauge and perhaps some of the other engine gauges if any of the limitations have changes. It might be possible just to have those remarked.

I haven't studied the TCDS so I don't really have an opinion on this particular installation. I was speaking generically.

I figure since the rajay for the TC is designed to normalize to a 27" limit, the stock gauge in the C would do the job. All the other gauges are the same I believe.

Maybe someone else can confirm or correct that.