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STC turbocharger for a TB20

I’ve come across this info from 9 years ago, and wonder if anybody here has any knowledge of it.

The company was called RCM (the Commander converter).

Compressions remain the same. It would be an intercooled conversion which takes out 90% of the heat so the turbo IO540 will run even cooler than the stock IO540 (they claim). The engine will maintain full power up to 20000ft. The outrageous overhaul costs of a TIO540 are avoided.

With 10 people funding the STC, the STC would cost about $100k and take between 1.5 and 2 years. The installed conversion would cost about $35k, which is the initial $10k for the STC funding and about $25k for hardware and installation labour. The guys not participating in the funding would have to pay at least $5k more.

The turbo would have its own TBO which is also 2000hrs.

If 10 TB20 owners can get together, this is way cheaper than changing the aircraft.

Any views?

Shoreham EGKA, United Kingdom

$25k for hardware and installation labour.

Never believe a word of that. More like double. SR22 turbonormalizer STC is a good benchmark.

Mainz (EDFZ) & Egelsbach (EDFE), Germany

If the STC by RCM never materialised, another interesting starting point may be found here.

LKBU (near Prague), Czech Republic

You would want non-funders to pay a lot more than that. Otherwise there is no upside to funding and taking the STC risk.

EGTK Oxford

Are there any comparable TN bolt-on kits for IO540 aircraft, and at what prices?

The STC must obviously cover a completely different exhaust system which has to come from somewhere…

The TB GT exhaust is inconel (and has a very long life) whereas the pre-GTs are stainless steel. Turbo installations with a SS exhaust will suffer on exhaust life. It’s possible that a TB20GT with a TN bolt-on would be OK but an inconel exhaust system could be very pricey – anything up to $10k.

Shoreham EGKA, United Kingdom

I think 100k USD will not be enough. I never started such a project but just a rough sum up:

2 engineers working one year on the project
200k USD

Renting a hangar for one year
12k USD

Parts for development
50k USD

Flying 500 test hours at 300 USD each
150k USD

Certification costs, DER, associated travel expenses etc.
30k USD

At least one IO540 engine going bust during the development
50k USD

That is a rough 500k USD and assumes all goes well and you do not have to buy the airframe for the development. I fear the TB20 is just a too small market for such a product and in addition there is the factory TB21 reducing the demand even more.

So as nice as it sounds i would not put my money in it…

Last Edited by Sebastian_G at 29 Jun 22:33

Or how it more typically goes (by my observation)…

Two engineers who have sole proprietor production businesses to pay the bills, and who want the new product for their own plane. They spend 6.5 days a week at the airport anyway and don’t count their hours.

An extra hangar that they rent anyway, which gets used for projects not production. “My wife pays for it” (i.e. covered by the business and written off)

Wholesale parts scrounged from ‘contacts’ plus a few big ticket items, the price of which can be used to amaze and entertain their friends.

DER is a friend with whom they trade favors, test flying is done by one of the engineers in his own plane. Fuel cost is a write-off for the business. Labor cost of employees making CNC parts etc is not tracked and is thereby absorbed by the business.

A small handful of sales follow, then its not worth doing anymore plus the prototype plane got sold to pay for the next exciting project. Every once in a while one of the projects goes into meaningful production to pay for all the fun.


I think typically something like that is how STCs get done ‘in the real world’, I don’t think too many are done as a straight business venture and I’m sure you’d lose money doing it that way.

Last Edited by Silvaire at 30 Jun 03:39

The job is smaller than that, an existing turbocharger design for the IO540 is taken and fitted under the TB20 cowling. Some new exhaust parts will have to be produced to connect the turbocharger. There are plenty of companies that do this kind of work. The manifold mechanism is changed so that it is fully open at ca. 50-75% of the travel and then actuates the waste gate with the remaining travel. That is the simplest way to turbonormalize.

PS: Altitude performance is not the only major benefit. Being able to cruise at low RPM and higher MP makes for a much more comfortable ride. At 23"/2100 I usually fly without headset.

Would the waste gate not be controlled by an MP sensing mechanism?

Shoreham EGKA, United Kingdom

That would make it much more complex and expensive. The Commander STC works the way I described (as does my TR182 which is a Cessna engineered add on, not from Lycoming).

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