Wow, outside of Karl Grove's water cooled Lancair at Reno, I'm really curious to see other examples of AC Aero's cylinders are being adopted in the aviation community. Seeing that these guys are applying this technology to their project was encouraging. Looking forward to see how they work all this out.

Their website:

https://www.helioak.com

AC Aero's US based support facility:

https://team-asap.com/liquid-cooled

I sure like the idea of bringing back the Helio, but it just seems like project suicide to use an un-proven engine design. Air cooled engines run over square just fine all the time.

My SR22T runs about 12 inches "over square" (37 inches and 2500RPM) on takeoff and climb every flight without issue.

Square is a stupid rule of thumb anyways, what does one inch of mercury have to do with one hundred RPM's anyway. What if we used PSI or Millibars to measure manifold pressure instead of inches?

I agree going with an unusual configuration right off could be problematic. There’s also a good chance that liquid cooling will add more weight than they’re planning.

They seem convinced they need to turn a 96” prop to get the desired performance.

My totally uneducated WAG is they could get the thrust they need with a 580 turning a modern wide cord 3 or 4 blade prop with 86” diameter. Add charged induction for bonus points.

How about a GTSIO-520 from a 421? Too heavy I suppose.

Here's an interesting article from Flying magazine 1984, about a (short-lived) re-start of Helio production.
You have to scroll down quite a ways to find the Helio article.

https://books.google.tt/books?id=O91_Zk ... &q&f=false

Back then, they used the 350hp TSIO-0540 & 400hp IO-720 Lycomings.
Seems like these days, if you're gonna think out of the box,
maybe a diesel engine or even a small turboprop might be the way to go.

A small turboprop would, but the engine costs $800k.

Diesel’s aren’t competitive yet.

Would a turboprop allow for the quick power changes often used in the type of flying airplanes like this are used for? I’ve never flown one so just asking.

How about a Lyc 580 that is in the 206? Simple and proven.

Ross4289 wrote:A small turboprop would, but the engine costs $800k.

Diesel’s aren’t competitive yet.

M601E-11A would be my engine of choice.
Half the cost of the turbines in the same cat, equal HP/TQ, (750hp) better prop, no fuel nozzles, and no HSI's...

No Brainerd for an ac in this weight class.

Cons... poor iron curtain stigma, poor support from GE in subsequent GE /Walter acquisition, and years of bandits running them way past their limits. But none of that faults the engine.

If this was my journey, I'd be on the phone with Prague.

As for the questions re throttle control on the T-Props in the short stuff... the prop still moves amazingly quick. It's just a new skill set to aquire. One viewing of a herc landing short should squelch that question.

Take care,
Rob

my plane has a RR250 in it. that little 420hp turbine is small, has a whopping 1100ft lb of shaft torque, its light, easy to use and reasonable fuel burn.. I'm pretty happy with it below 10,000 ft. run into temp issues above that..

sadly a new unit is over $700k USD.. hence why people dont buy and convert to em. would be nice to see one in a Helio.

Cam,

I want to see it sold as a kit. The FAA will likely make certification as difficult and expensive as possible. I get that bush charter operations cant use EABs for hire, but they probably wont buy too many million dollar certified machines either. What do I know, Ive never even been to Alaska. Maybe these guys have tons of dough?


At the very least, a kit box full of new parts could make restoration of a certified data plate feasible.

The new engine is amazing im sure, but what are the odds of a financially viable certification process?

Maybe a builder assist program with a fly-off that explores Alaska, if that's the point of assembly. I think suitably sized turbine power under the hood, maybe an Allison C20 via an overhaul program might be one option. The benefits, in fuel, operating costs, empty weight and useful load are worth considering.

With all that said this is a concept that's well above my snack bracket, I can watch in awe and ponder on the what if !!

this unit is 150-200 usd. not sure the times
https://www.barnstormers.com/classified ... atid=18315

Somebody bolt it up!

Around 35 years ago JAARS had blueprints developed to installl the Zoche diesel in their H-295s. It seemed like a great engine at the time. Anyone know why this diesel never made it to market?

I think Continental announced at Kosh this year a the Diesel from the DA50 Diamond will be available in a couple years in the Cessna 206 as a conversion.

Ive got 40 hours in a DA40 Diesel and it worked good. kinda heavy and slow tho..

I've always liked the the concept behind the Deltahawk diesel. I don't know if I believe all of their fuel economy claims, but they're planning a 300hp 6 banger that could be a good fit. Could be a little less risky than the AC 540, but I'm sure they've done their homework. I've seen the AC cylinder castings, and they're beautiful things to behold.

Halestorm wrote:My totally uneducated WAG is they could get the thrust they need with a 580 turning a modern wide cord 3 or 4 blade prop with 86” diameter. Add charged induction for bonus points.

There's a pretty good analog for that performance in the Helio H-250, which is an O-540 turning an 88" prop (although not a modern one). It doesn't pull like a GO-480/96" prop, but performs pretty well in its own right.

There is a huge difference between a 250 HP O-540 and a fuel injected 320HP IO580

Even going from a 250 hp O-540 to a 260 Hp IO 540 seems more like 50+ more HP than the 10 HP difference in rating.

Without a doubt the 580 would have been the simple straight forward way to go.

The issue with over square has more to do with Prop Harmonics than the engine not being able to handle the combustion pressure.

There are a few Lycomings with limitations to not run below 2300 rpm for extended periods for that reason.

Did anyone here see it fly at the Airmen's Show this spring? What engine did they have in it there?

Flew for the first time with last month. It had the new water cooled engine and was impressive. https://www.facebook.com/watch/?v=792845563453272
DENNY