[consumer451]

This is a tangent, but you are well informed in the space, and I would love to read your opinion.

There is a new heli player trying to start from clean-sheet, called Hill Helicopters.[0] They are building a sleek new carbon fiber fuselage, but what I am wondering about is the fact that they are also making their own turbine engine.[1]

I have assumed that their new turbine is the hardest part of their plan, am I correct in that assumption? Is it crazy, or not crazy, that they are trying to do this themselves?

[0] https://www.hillhelicopters.com/

[1] https://www.hillhelicopters.com/gt50-engine

[buildsjets]

I would say it is not impossible for them to do it themselves if they are adequately funded, but I question the wisdom of choosing to do so rather than buying an existing certified turboshaft engine off the shelf, of which there are many in that power range. Also, that seems like an excessive amount of power for that size helicopter. A similar horsepower engine is the Pratt-Whitney PW206B, used in the Eurocopter EC135. But the EC135 is a much larger helicopter and has twice the payload capacity of this design.

The engine itself is a fairly standard centrifugal compressor design, not particularly challenging from an engineering, or material science standpoint. But with no new technology being brought to the table, there is no performance reason roll your own engine, and you are going to have to beat existing engines that have decades of refinement behind them.

I know of two other companies developing microturbines that are considerably smaller than this in an market where there is no real competition, with some cool new technologies like regenerative microtube recuperating heat exchangers. One of them is in development, one is flying their turboprop and developing their turboshaft.

https://www.turbotech-aero.com/

https://turb.aero/

There is a design/prototyping/manufacturing company called ConceptsNREC https://www.conceptsnrec.com/home that specializes in turbine engine and pump design. They do analysis work for basically every jet engine manufacturer and automotive turbocharger manufacturer, have manufacturing facilities to prototype just about every part of a jet engine, and an extensive testing facility. I would just about bet that Hill has used their services in the design and prototyping of their engine. It's a great place to work if you have a PhD in aerodynamics but want to live in rural Vermont. They also sell a CAD design and CFD analysis software package specific to turbomachinery.

If you like industrial stuff, here's a video of their prototype shop, showing some of the parts they make. My favorite is a tiny titanium impeller for a jet fuel starter system on the F-22, at 3:35. It's about the size of a quarter, and took 40 hours to machine with an 0.020" / 0.5mm diameter ball end mill. I've met both the guys in the video, they are brilliant machinists, but definitely not well polished youtube influencers, lol. https://www.youtube.com/watch?v=6v98_oxqY7E