This is exactly correct, which is part of the reason that smaller turbines cannot be as efficient as larger turbines.

Without advanced cooling technology in the turbine blades, the gas temperatures have to be lower, which limits efficiency and limited efficiency reduces power output per mass of engine and increases fuel flow, and all in all, makes the small turbine cost more to run.

Given all the complexities, I don't think we'll see inexpensive aero turbine engines anytime soon. It's just not a thing that lends itself well to personal-sized airplanes.

With all honesty, in the under 350hp range and especially for intermittent use, a reciprocating engine fueled with gasoline makes more sense than anything else. I'd think certain changes would be reasonable and allow the use of ordinary unleaded gasoline with little penalty. Liquid cooling, electronic controls for ignition and fuel control, possibly reduction gear drive, all would likely contribute to making that happen.

On the turbine side, it makes sense when the capital cost, operating costs and payloads balance out against the utilization.

Flying is expensive, but flying is valuable. Every hour flown is a lot of money spent, but at least in a business environment, that's justified by the excess value created by the flight.

High utilization means the ROI comes faster, because capital costs are time-based. The longer the capital is tied up, the more it costs. A $500,000 small turbine makes sense if it is generating value well in excess of its capital costs and the uptime and increased payload available produce more excess value.

I have to admit, my airplane isn't earning a living or generating any excess value. It is there because I like it. I don't use it enough to justify it economically. Keeping the capital costs low are important for me.

The only turbines I could consider are those as discussed in this thread. Realistically, on the tail-end of their capital/value curve, where running them until no longer airworthy and disposing of them is the plan. There's a spot on the depreciation curve where that happens, aka, "the disposable jet". Fly it to the boneyard. It works if there's a supply of engines and other parts readily available for the type.

There are no cheap airplanes.

The thing I don't understand is why there are no experimental turbines? We've had them in the RC world for decades. Yes, they're inefficient, but obviously not hard to make as the prices of those clearly show. Scaled up and made to a slightly higher standard, they would provide some alternatives for the homebuilt crowd. Yes, not great fuel efficiency, but at least better reliability and access to cheaper fuel.

The TPE331-10 and later has cooling holes and passages in the first stage turbine wheel.

Mike C.

That's funny! I have a bunch of model airplanes and if I had to make a bet that one would 100% start, I'd pick the $2,000 turbojet that burns a gallon of gas in 10 minutes but is 10000% reliable. I think you are definitely on to something.

I thought the Walther engines were experimental only? I thought other non-certified turbines have been used in EAB aircraft.

Turbine powered experimental amateur built are required to have the same approved inspection program, schedule and compliance as certified turbine aircraft. (Order 8130.2 references specifically FAR 91.409(e) through (h). ). Maybe that has something to do with it? I don't know.

The Walter engines have been installed on both experimental aircraft, like the Lancair IV-P and on certified aircraft like the King Air C90, first with the Walter 601 and now with the GE H80

evolution lancair is experimental and has a PT-6 135 and there are about 80 flying around

I'm pretty sure Adam meant turbin engines that were experimental, not experimental designated aircract flying certified turbine engines.

Maybe I missed something, but I saw this a few weeks ago and meant to ask (got sidetracked and finally back to it )

https://www.trade-a-plane.com/search?ca ... e=aircraft

@Adam S Frisch : "State Intentions"

viewtopic.php?f=43&t=164343

search button is your friend

Yes, I put that on there before I decided to keep her.

"Roger".



Yes, I put that on there before I decided to keep her.

Think for a bit about how many copies are going to be sold. Each market has to dilute the engineering/development costs by the number of units sold.

Its why drones used to be expensive and now aren't. Same for aircraft engines. Add to that; what the market will bear for something that will/will not return a profit when used.

RC turbines can be cranked out by the thousands and dont have to be certified and unless you hit someone in the head, the maker wont be sued for wrongful death.

But the primary factor in cost is the abundance factor. (economy of scale in production).

What's the update Adam? Any closer to being fully finished?

Unless the plane is in the junkyard, airplanes and finished is an oxymoron.

Tim