There's the real issue. Plus only 6 seats. Better to put a single TP on a KA 200 AF from a comfort standpoint. However, if they could bring it in at a cost below the KA 90, it might might sense in the 510 AF.

RM

I would be EXTREMELY surprised if there isn't quite a lot of lead ballast in the tail of this airplane to make the CG work out. You can't remove two jet engines behind the wing and put a big PT6 in front of it and have a reasonable CG.

Thus any real SETP product from Textron would not look what you see in the picture. At best, the wing has to be pushed forward, which affects the cabin door location, which affects lots of other things.

My take on this project is that it is an engine test platform and not much else. Any real SETP will be close to a clean sheet design and not look like a Mustang.

The test airplane can tolerate a huge ballast to make it work since they can run with low fuel and cabin loads to gather the data they need. A production airplane can't.

Mike C.

Mike you think Cessna does the new project with some turboprop aircraft ? Also please your opinion , why turboprop and the turbofan engine cost so much money ? They use gold inside ?

They do use exotic alloys.

There are significant barriers to entry and minimal competition

The parts are very intricately designed and manufactured to very tight tolerances in small lots.

I took a tpe-331 engine operation course and was amazed at the intricacy of the parts. For example the igniters are basic spark plugs but have multiple, complex air channels machined through them for cooking airflow.

I would be EXTREMELY surprised if there isn't quite a lot of lead ballast in the tail of this airplane to make the CG work out. You can't remove two jet engines behind the wing and put a big PT6 in front of it and have a reasonable CG.

Thus any real SETP product from Textron would not look what you see in the picture. At best, the wing has to be pushed forward, which affects the cabin door location, which affects lots of other things.

My take on this project is that it is an engine test platform and not much else. Any real SETP will be close to a clean sheet design and not look like a Mustang.

The test airplane can tolerate a huge ballast to make it work since they can run with low fuel and cabin loads to gather the data they need. A production airplane can't.

Mike C.

Significant barriers to entry. Correct? Exotic alloys. Total BS. You can get more exotic alloys these days in a hiking stove that you will get in a PT6. And it will cost much less than a single turbine blade. Next thing everyone will tell me is that Garmin uses better grade of resistors in their avionics vs their marine gear at 10% the price.

Maybe exotic was an overstatement. They dont sell anything to make turbine blades in the aviation aisle at lowes.

The PT6 is probably a great example of near monopoly pricing/behavior. Just not a lot of competition in the sub-1000 hp turboprop market.

Yes there is certainly some exotic metallurgy in the jet and turboprop engines. There are also manufacturing tolerances that are almost unimaginable. The internal aerodynamics are pretty well mature, so most of the efficiency gains that remain to be realized are going to be in materials and tolerances. Neither of those roads to improvement are cheap.

Are you sure? GE, Rolls Royce and Pratt continue to make turbofans more and more efficient. And the fundamental materials and tolerances have not changed. Just the designs are getting more and more sophisticated. just look at the changes in blade shapes for the first compressor fan over the years. New ones look almost like a sine wave; older ones were straight, in between they were curved....
None of these type advancements are being applied to turboprops. Probably because the market is not big enough.

Tim

You need an airframe that can withstand the power, altitude, and airspeed you want to test at. The Mustang airframe provided that. A 208 doesn't.

Mike C.

Maybe. It seems like a viable product, something about the size of a TBM that costs less than a TBM. I am somewhat surprised Cessna/Textron has not done a SETP yet.


An OEM like Textron gets sweet deals on engines, so they actually don't cost as much as people think to them. The engine maker is looking at the long term residual revenue from engine parts and support going forward.

The cost of the engines is in two places mostly, the machining of the compressor and hot section parts in the airflow, and the control system be it mechanical or FADEC.

Typical T4 (inlet temperature) of a TPE331 is 1100C, or 2000F. That is glowing bright yellow hot (not quite "white hot"). The turbine wheel is going over 40,000 RPM. The blade is under tremendous forces. So, yes, it is hard to make.

Mike C.

You need an airframe that can withstand the power, altitude, and airspeed you want to test at. The Mustang airframe provided that. A 208 doesn't.

Mike C.

Part of their business is engine selection and evaluation.


It can. The Mustang airframe represents the closest thing Cessna has to an SETP in terms of fuselage and wing design.

The closer you get to the real thing, the more reliable any extrapolations will be.


Engine HP, altitude, and true airspeed play a far more significant role in prop tuning than the airframe. They can hang the same prop as the PC12 and be pretty darn close to optimum.

In the end, only Cessna knows why they did it. All I know is that the final SETP product can't look exactly like the picture due to CG issues.

Mike C.

It can, just requires a lot of downforce on the tail. Very likely this would be inefficient; so not practical.

Tim

On a TPE331 going 41,730 RPM (100% RPM), the 1st stage turbine wheel blade is experiencing a centripetal force of 9,665 pounds. The blade only weighs 1 ounce, so this is about 150,000 Gs. If a human could be placed on the blade, they would be crushed by a force of 25 million pounds.

The stress on the root of the blade is over 50,000 PSI.

Plenty of materials can withstand 50,000 PSI. Plenty of materials can withstand 2000F. Not many can do it simultaneously and reliably.

Mike C.