Light jet GA aircraft

Vega ECM

Many thanks for the info and the link

After a bit of digging around, I’ve sourced a small turbine delivering about 50 pounds of thrust for a price of about £5,000. Fuel consumption at cruise rpm is said to be about 7 – 8 Imp. galls. per hour, which doesn’t seem too bad considering the price of Avtur compared with Avgas. The weight of the engine is a slender 25 -30 pounds.

Early indications are that two of these units would be needed to adequately lift an aircraft with an MAUW of about 3,000 lbs. I’m thinking that a PA38 airframe with a bit of life left in the spar would, as an airframe stressed for limited aerobatics lend itself to the engineering of two hard points – one under each wing, to carry the engine pods.

Apart from a final examination and verification of the aerodynamic stresses, can anyone think of any reason why this project should not be attempted ?

No where near enough installed thrust. It will barely self sustain at max ld. To match the prop performance you will need somewhere between 5 -10 times the installed thrust.

For more information on the numerous attempts to realise a practical jet GA check out the website minijets.org

Didn’t the French do something similar with a twin-jet engined Cri-Cri? I believe it appeared at a few French airshows.

After a bit of digging around, I’ve sourced a small turbine delivering about 50 pounds of thrust for a price of about £5,000. Fuel consumption at cruise rpm is said to be about 7 – 8 Imp. galls. per hour, which doesn’t seem too bad considering the price of Avtur compared with Avgas. The weight of the engine is a slender 25 -30 pounds.

Early indications are that two of these units would be needed to adequately lift an aircraft with an MAUW of about 3,000 lbs. I’m thinking that a PA38 airframe with a bit of life left in the spar would, as an airframe stressed for limited aerobatics lend itself to the engineering of two hard points – one under each wing, to carry the engine pods.

Apart from a final examination and verification of the aerodynamic stresses, can anyone think of any reason why this project should not be attempted ?

Didn’t Rover produce a turbine that they fitted in a Currie Wot of all things? Probably about the time they had a turbine car at Le Mans. 1962-ish perhaps?

Yes.
Like Chrysler’s advanced turbine car of the 60s, and the turbine car that raced at, and almost won, the 1967 Indianapolis race it eventually met its demise over costs, temperatures and fuel rate concerns.

The racer, backed by the well known racer/race team manager/businessman Andy Granatelli and driven by Parnelli Jones, was designed by Ken Wallis (a very distant relative of Barnes). The STP-Paxton Turbocar was built around an aluminum box-shaped backbone and powered by a PWC ST6B-62 and drove a Ferguson 4-wheel drive system.
The heat was so intense, it warped the first aluminum tub.

Didn’t Rover produce a turbine that they fitted in a Currie Wot of all things? Probably about the time they had a turbine car at Le Mans. 1962-ish perhaps?

Most of the types you mention were more likely converted to turbine power for use in places where Avgas is a limited commodity. In some countries Jet A1 is the only fuel available at the majority of airports.

Many of those airframes pre-date that concern, but that is one reason for the change…as is the obvious: more power, longer TBOs and the lack of suitable piston powerplants over a certain size/h.p. rating.
Certainly the fuel availability issue applies to the bush types, much less so for the average GA types like the King Air and the Bonanza/Duke conversions.

Speaking of bush types, to my list I’d add the Helio Stallion which added a PT-6 to the proven airframe, and the turbine Beech 18 conversions.

They have been plenty of piston types converted to turbine power, so the issue isn’t THAT bad.
Beech King Air
Beech Mentor
and Bonanza and Duke conversions
Piper Malibu
Turbo Commander
DC-3
DHC Beaver & Otter
Cessna L-19
The new SB 47 with RR300 power
S-58T/Wessex
Islander
Not to mention specialized applications like crop sprayers…they’re limited by chemical payload more than range, but they still get the job done.

Also consider turbine might be faster so any range penalty may not be that great

They’ve been making the PT-6 and Allison 250/RR300 practically forever and they’re still not exactly cheap.

I’d imagine RR could answer your question about cost of turbine production vs. piston.

Most of the types you mention were more likely converted to turbine power for use in places where Avgas is a limited commodity. In some countries Jet A1 is the only fuel available at the majority of airports.

Sf260tp performance and range

http://www.aleniaaermacchi.it/en-US/Media/Lists/ProductFactSheets-Fact%20Sheets/SF-260TP.pdf

There is a turboprop Cessna 206, it’s about the smallest turboprop I know of although there might be smaller. http://www.soloy.com/files/Products/Documents/206%20Specs-Price.pdf

You can see the price of the conversion in the document.

I’ve found a site in America called Scaled Jet Engine Technologies. I’ve sent an e-mail outlining some ideas and asking for feedback.

There’s a few economical jet powered self sustainer gliders about now, none as self-launchers as far as I’m aware so perhaps there’s light at the end of the tunnel. You just need the will (& pots of money) to make something worthwhile work – sadly there’s neither in the UK aviation industry.
Blue skies
R2

I find it difficult to believe that we lack the ingenuity to come up with a workable and practical turbine powered light aircraft or VLA combination.

We now – thanks to some degree of de-regulation – enjoy a wide variety of recreational aircraft all mainly powered by piston engines of one kind or another. The problem seems to be attached to little practical gain when switching from piston to turbine.

The principle drawback to the use of turbine – as someone has mentioned – is excessive fuel consumption by comparison with piston. Although any increase in fuel consumption would be offset by the cheaper price of avtur. Reliability of performance is probably about the same for both methods of propulsion.

I don’t know much about aero modelling except that tiny turbines are in common use. My guess is, that when scaled up the size of the turbine required for recreational flight in light aircraft would be quite small in comparison with the average, same power output, piston engine. This scaling down would, presumably, be reflected in the cost of production ?

Does anyone on the forum know of any papers published or reading matter available on this subject. I’d certainly like to have a closer look at the feasibility and potential.

Talking those kind of figures the turbine seems like overkill. Also the propensity for a turbine engine to consume far more fuel than a reciprocating engine would drastically reduce the range of the aircraft unless you added more fuel tankage or came up with a totally new airframe design.

They have been plenty of piston types converted to turbine power, so the issue isn’t THAT bad.
Beech King Air
Beech Mentor
and Bonanza and Duke conversions
Piper Malibu
Turbo Commander
DC-3
DHC Beaver & Otter
Cessna L-19
The new SB 47 with RR300 power
S-58T/Wessex
Islander
Not to mention specialized applications like crop sprayers…they’re limited by chemical payload more than range, but they still get the job done.

Also consider turbine might be faster so any range penalty may not be that great

They’ve been making the PT-6 and Allison 250/RR300 practically forever and they’re still not exactly cheap.

I’d imagine RR could answer your question about cost of turbine production vs. piston.

Talking those kind of figures the turbine seems like overkill. Also the propensity for a turbine engine to consume far more fuel than a reciprocating engine would drastically reduce the range of the aircraft unless you added more fuel tankage or came up with a totally new airframe design.

Tony,

About how much is ‘not cheap’ ? For a turbine that will, say at MAUW lift about one ton and propel it at about 150 kts ?

Simply because of cost, turbine engines are not cheap, no matter how small, there are some, the Sf260 comes in both versions

I’m not talking about small business jets. Is there, apart from something obvious, some underlying reason for the lack?

Thirty years ago the aviation media asked the same question….
The cost of the engine. Turbines are never going to be “cheap and cheerful”.
Also, to make use of turbine speeds, you sometimes need to fly high…so then you need to pressurize the thing…and if you’re going to do that, might as well add a couple of seats….and more avionics.
And so it goes.
You start out with a 172 replacement and it turns into a 6 seat bizjet.

Here’s the closest thing I know of…
http://cirrusaircraft.com/vision/