C-90 in Taylorcraft

[Dano"T"]

Is there a field approval out there for a C-90 in a BC-12D?

[Acroeric]

Re: C-90 in Taylorcraft

There have been several field approvals over the years for C90's and 0-200 engines in the past but with the latest FAA Inspector Handbook order 8300.10 volume 2 chapter 1 release we are limited to a 10% increase in horsepower for field approvals. I am not at all happy about it but it is the rule- however, if one were to accomplish the Harer STC then apply for a field approval for a C90 (85 HP + 10% = 93.5 hp) it should be possible. Another option is to apply for a one time STC. These are not easy but not impossible. I think a fellow member just got one for an 0-200 installation.

[VictorBravo]

Re: C-90 in Taylorcraft

But the basic Taylorcraft design and engineering is ALREADY approved up to 100 HP (F-19 Sportsman 100). One can argue that the basic airframe structure is identical or nearly so.

Also that the engine design is nearly identical, and that the C-90/O-200 was designed specifically to be a bolt-in replacement for the 65-75-90 engines

ALSO, the Taylorcraft is kind of approved for (almost) 100 HP because the Harer STC allows a C-85 and another new STC allows the O-200 crankshaft to be installed in an 85.

Perhaps it can be positioned as a change from one approved model to another approved model, rather than "going 10% past the original design limit".

In FAA terms, the 100 HP Sportsman is "PREVIOUSLY APPROVED DATA"... (with an excellent safety record and no in-flight breakups) which is exactly what the inspectors are looking to see.

I also humbly suggest that you make a point of saying that the original certified flight loads, airspeeds and weights (either original or STC'd weight increase) will not be changed.

Sounds to me like it's a case of how it's written rather than how it's modified That being said, our airport does have a few T-crafts (no STC or 337 paperwork) with A-65's and C-85's that seem... particularly healthy

[Acroeric]

Re: C-90 in Taylorcraft

All good points that make common sense and ones that I tried in the past- it all comes down to the TCDS and serial numbers affected. Unfortunately the F-19 is on a different TCDS, this is also why one can not legally install a C-85 on a BC12-D and why "almost" etc doesn't work. If you look at serial number eligibility for the BC12-D-85 it rules out all the 65 hp Tcrafts for installation of a C85 except by STC. In the TC it says minor structural and fuel system changes but doesn't identify what they are- I do not like it either. As for trying to submit it to the FAA in different forms - I am an inspector with the FSDO- with our new guidance our hands are tied. Am I saying that all BC12-D, BC, BL, etc Tcrafts with C85's installed and no STC or field approval are illegal. . . . . . yep.

Now if Harry came out with some data as the manufacturer to say that is was structurally ok and maybe a parts kit for the change then it could be done.

[Carl Ellis]

Re: C-90 in Taylorcraft

Harry who?

[jgerard]

Re: C-90 in Taylorcraft

Just a quick reminder to any of those thinking about bolting a larger engine on a short mount. You must use a -8 style case with the conical mounts, not the later c90 and 0-200 style with the lord mounts. The lord style mounts do not provide the necessary structure to work properly with the taylorcraft "short" mount. The -19 "long" mount has the required extra bracing between the mounting points tying the whole thing together.

Just because it fits does not mean it's right!

Jason
N43643

[Acroeric]

Re: C-90 in Taylorcraft

All is not lost- I was looking through my 8300.10 and if you submit a field approval for a C90 or 0-200 I (at the FSDO level) I can not approve it but I can go to the Aircraft Certification Office and get engineering assistance/ approval. The 10% rule only applies to FSDO level field approvals. AS for the mount with the -14 series C90 and all the 0-200's, you can mod the existing mount fairly easily. I chose to use a C90-12 so the existing mount would not need the mod. There are many folks that believe that the C90 is stronger than the 0-200 (myself included) and they can be purchased for less than an 0-200 usually. They are also a bit lighter.

[jgerard]

Re: C-90 in Taylorcraft

Best case is the c90 with the through bolts in the center bearing web, and I think? they only came on the later versions of the-12. Someone told me the -14 lord mount cases were supposed to be the same as the 0-200 ones (which also have through bolts). My source could be wrong, not sure.

Jason
N43643

[Grant S. Bailey]

Re: C-90 in Taylorcraft

I am putting a C-90-12F in my 1951 Model 19 which originally had a C-85-12F. The airplane is being put into the special "Owner Maintenance" category in Canada which allows me to do this engine install with minimal hastle.

I just finished my last wing so now the covering and painting is essentially complete with the exception of the two elevators.

I am catching you Robert Lees!!

[VictorBravo]

Re: C-90 in Taylorcraft

For what it's worth, I also recommend the through-bolts for anyone rebuilding a C-85 or C-90. I am NOT an experienced engine builder or engine expert.

But I had a little Formula 1 racer once, and the IF1 organization specifically requires the thru-bolt modification on all C series engines. The center main bearing takes a beating on those engines normally, and it is made far worse in racing conditions (4000+ RPM with 8 inch prop extensions on the front!)

Even at 2500 RPM, anything that extends the life of these engines and makes them not wear out as fast is a good thing.

But the thru-bolt mod is NOT something an average backyard mechanic should do. There are machining operations that are done, and important oil passageways are affected if I am not mistaken. Amateur level fooling around on this will lead to metal shavings in your oil at BEST, and a clogged oil galley/engine failure in the worst case.

Bill