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RR M250 Powered PA-18 Super Cub

mdautry

Registered User
Hello All,

Looking for some information from everyone on a controversial modification to a PA-18 Super Cub...

I would like to know if anyone has ever successfully placed turbine on a super cub and if there is an STC available. I am interested in putting a Rolls Royce M250 turbine on a PA-18.

I have a significant amount of experience with modified piston cubs but no experience with turbines.

P.S. This mod is in no way targeted to land or take off in a shorter distance; takeoff, landing, and max gross are irrelevant to this modification.

Many Thanks,
mdautry

Rolls Royce M250

 
Once upon a time there was a small turboprop engine under development in Pennsylvania (I think). An arrangement was made to install in a Super Cub with the idea of producing the combination by Turbine Cubs of Wyoming (now Backcountry Super Cubs). http://www.supercub.com/ It did not work out and the project was dropped.

As I recall, it was the engine rather than the combination which was the reason for canceling the project.
 
I saw an -18 in Douglas, Wy that had an engine mount for a turbine but no engine. Havnt heard anything on that one. I have a few hours behind pratts and my personal opinion is I wouldnt like the lag in response on a cub.
 
Once upon a time there was a small turboprop engine under development in Pennsylvania (I think). An arrangement was made to install in a Super Cub with the idea of producing the combination by Turbine Cubs of Wyoming (now Backcountry Super Cubs). http://www.supercub.com/ It did not work out and the project was dropped.

As I recall, it was the engine rather than the combination which was the reason for canceling the project.

Pete, I thought the issue was more the reduction system than the engine itself.

But the the biggest issue with any turbine, and certainly a RR 250 would be fuel requirements. Fuel flow of what...... 25 gph? Where are you going to carry enough fuel to provide a useful endurance?

MTV
 
10 years or so ago there was a bare Cub fus on gear with a small turbine mounted on the front on display at the seaplane flyin in Greenville. Might have been Turbine Cubs display?

Glenn
 
Pete, I thought the issue was more the reduction system than the engine itself.

But the the biggest issue with any turbine, and certainly a RR 250 would be fuel requirements. Fuel flow of what...... 25 gph? Where are you going to carry enough fuel to provide a useful endurance?

MTV

I spent some time with Joe Soloy in the early 80's. Brilliant guy, just the design of the single power lever was something. At the time I was with him he was working on an auxiliary fuel system for the Cessna's that would have been large aerodynamic replacement wing struts that held fuel. They would gravity feed right to the fuel selector so in theory a very simple design. Don't know where that got derailed but he was always thinking.. maybe couldn't make them large enough to be practical..
 
I have been around the Allison/RollsRoyce 250 engines in a couple different Cessna 207's on floats operated by my employer. It is the Soloy conversion at 420 Horsepower with a big Hartzell 3- blade prop.

I cannot imagine this engine and also a reduction gearbox to handle it placed on a SuperCub.

However, I can imagine this engine and a hydrostatic drive to power a BadaSS long track mountain snowmachine!!!!
 
A number of years ago, Doug Combs converted a Luscombe 8E to a 150shp Apex turbine.
Dunno the fuel burn or anything else, but the sound of it starting up was pretty cool.
The frosting on the cake was throwing it into beta and backing up into a parking place.

https://www.youtube.com/watch?v=e3jyhhFUrgM

The long nose wasn't too bad looking-
not as bad as the nose on this turbine-powered C185 anyway.

turbine C185.jpg
 

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  • turbine C185.jpg
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A number of years ago, Doug Combs converted a Luscombe 8E to a 150shp Apex turbine.
Dunno the fuel burn or anything else, but the sound of it starting up was pretty cool.
The frosting on the cake was throwing it into beta and backing up into a parking place.

https://www.youtube.com/watch?v=e3jyhhFUrgM

The long nose wasn't too bad looking-
not as bad as the nose on this turbine-powered C185 anyway.

View attachment 30555

I was at the Planeview dinner/gas station getting gas and they had just opened landing on 36 at Kosh one evening. Base was about 200' over the top of the pumps I was using. Every 10 seconds a new plane would fly right over me and after about the 10th one came a new different noise and a silver gray Luscombe with a whistle flew over me. My first thought was no way was that Luscombe a turbine. Took me half the next day to find it parked, very very cool.

Glenn
 
Turbine_Super_Cub.jpg


Turbine_Super_Cub_panel.jpg
 
I spent some time with Joe Soloy in the early 80's. Brilliant guy, just the design of the single power lever was something. At the time I was with him he was working on an auxiliary fuel system for the Cessna's that would have been large aerodynamic replacement wing struts that held fuel. They would gravity feed right to the fuel selector so in theory a very simple design. Don't know where that got derailed but he was always thinking.. maybe couldn't make them large enough to be practical..

Joe was nothing short of brilliant, no doubt about that. The gearbox he designed for those helicopter engines is pure genius.

But the engine on that Turbine Cubs plane was a converted ground power unit, I think.

MTV
 
Pete, I thought the issue was more the reduction system than the engine itself.

But the the biggest issue with any turbine, and certainly a RR 250 would be fuel requirements. Fuel flow of what...... 25 gph? Where are you going to carry enough fuel to provide a useful endurance?

MTV
Mike, I never knew the real reason other than it turned out not to be a viable mod.

I can't imagine getting the fuel flow as low as ndill suggests. The best I could do in the Soloy 206 was just under 20 gph.
 
Joe was nothing short of brilliant, no doubt about that. The gearbox he designed for those helicopter engines is pure genius.

But the engine on that Turbine Cubs plane was a converted ground power unit, I think.

MTV

Yep, this thread just brought back memories of Joe and led to some drift - thread and mind.....
 
First off, thank you to all who replied!

I do recall the Innodyne/ATP - APU style turbine that was in development back in the early 2000s... Unfortunately, it appears that not much has materialized throughout that development.

@ndill, I do remember seeing the sonex jet and going to their website a while back, thank you very much that is a brilliant recommendation. Does anyone know if the TP100 Turboprop engine is FAA approved?

When you give a little you get a whole lot more, so here goes...

Fuel; yes fuel; obviously an issue when you are burning through 25 ish gallons per hour at cruise... The basic configuration would be 4 wing tanks with a belly pod for about 100 gallons usable. For my purposes that is more than enough loiter.

I have seen numerous posts regarding the new state of 337 field approvals, as in they are much harder to come by. Is there any encouraging information regarding a possible field approval on a turbine cub using an FAA approved turbine: I.E. RR M250?

Thank you to all and your wealth of knowledge is greatly appreciated!

Mike
FSDO cannot issue a field approval for more than a 10 hp increase. Has to go to engineering.

Sent from my SM-N900V using SuperCub.Org mobile app
 
I had two different Siai Marchetti 1019's,one B15 Allison (Rolls Royce now) and one B17 420 HP, B 15's no longer supported by Rolls. they are great, but just not really made for short field work like a cub. And fuel burn is about 20 gph, so need big tanks, They have 80 gallons in the wings, 20 in each drop tank and drop tanks to really go anywhere without needing fuel, just would not work in a cub unless big tanks could be carried, then gross would be a factor.
John
 
FSDO cannot issue a field approval for more than a 10 hp increase. Has to go to engineering.

Sent from my SM-N900V using SuperCub.Org mobile app
And the fact that it is a turbine, the certification rises to another higher level.

Also it might be a better decision to go to a home built Cub which has the beef ups required to get the gross weight up high enough to carry the fuel, crew and baggage (passenger). Then certification is not a worry. You likely will save money.
[/QUOTE]"The basic configuration would be 4 wing tanks with a belly pod for about 100 gallons usable. For my purposes that is more than enough loiter.[/QUOTE]
Also if this is for some for hire operation you could consider a special purpose (Restricted) airworthiness certificate.

Steve, where did you find the post which you replied to? It didn't show up on my computer.
 
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This is like putting a Chrysler Hemi in a Smart car. Yes you can do it but should you do it ?
 
Getting a little of topic but I always thought a small diesel would be nice on a cub. Cheap fuel, good gph, and high torque for great climb performance and haulin those heavy loads.
 
Getting a little of topic but I always thought a small diesel would be nice on a cub. Cheap fuel, good gph, and high torque for great climb performance and haulin those heavy loads.
Diesels generally have a high pounds per horsepower ratio when compared to an air-cooled gasoline engine or turbine. A cub with it's light weight may not want the weight which a diesel would place ahead of the firewall.
 
Very true. Id like to see the weight of a small 4 cyl liquid cooled diesel vs 180 hp lyc. Diesels need no ignition system, but the fuel system is finiky. A pin hole in a line can cause probs. Im sure if it were feasable, someone prob would have done it already.
 
10%??????? Rather than 10 HP

Major Repair and Alteration Data Approval

B. Structural Strength.
(1) Changing primary structures (structure that carries flight, ground, or pressure loads as defined in
AC 25.571-1, Damage Tolerance and Fatigue Evaluation of Structure, as amended).
ENG(Engineering)
(2) Substituting airframe primary structural materials. STC
(3) Substituting an engine or propeller (such as replacing a reciprocating engine with a turbine
engine).
STC
(4) Substituting or altering a reciprocating engine such that the net result is an increase of more than
10 percent greater horsepower. STC

See page 11 and 12.
http://fsims.faa.gov/wdocs/other/Major_Repair_Alteration_Job-Aid.pdf
 
This is the part which applies to this thread.
(3) Substituting an engine or propeller (such as replacing a reciprocating engine with a turbine
engine). STC

This part can be worked around by limiting the maximum hp to no more than 10% more than the current engine through placards or a red line on the tach/manifold press. Even though the engine itself may be approved to a much higher hp.
(4) Substituting or altering a reciprocating engine such that the net result is an increase of more than
10 percent greater horsepower. STC
 
I have spoken with a local FSDO maintenance guy and he has informed me that anything is possible given time/money... The experimental route would be the least hassle to accomplish the modification, we all knew that. That brings us back to the use of an experimental aircraft for hire.

After seeing all of the STC's available for Cubs I am somewhat surprised that a Turbine hasn't been done so far... Maybe I will be the first one to do it but I know it will not be in the near future.

This brings me to a compromise...

Essentially I am trying to get as much thrust as possible out of this modification. I have heard of an IO-520 Super Cub that exists, does anyone have any more info on that?

Many thanks to everyone,

Mike
 
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