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Thread: Turbine Super Cub

  1. #41
    Bugs66's Avatar
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    Quote Originally Posted by Bill Rusk
    When I went to get the wings I saw the turbine. Looks good. Nick Smith Sr was also involved in the prop design. The warp drive unit did not work. He says the first turbine cub should fly before Oshkosh. They were going to try to get it to the show but don't think all the paper work will be done by then. He does not think stability will be a problem.
    Should be interesting.

    Bill
    Anyone have an update on this? My friend who is building an RV is pretty excited about development on their end. I have to admit salivating over a turbine Cub possibility. My own personal Porter would be very cool.

    Bugs

  2. #42

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    Stephen,

    I'm also very interested in this engine. I've spoken a bit to the owner - charlie - at Innodyn. He says the engine will and does have reverse. If there is any question in your mind, check out the following link. It's a video of the RV on landing.

    http://www.innodyn.com/aviation/action.html

    The direct drive turbine is a great design for quick response. There is no reason it can't have reverse. The propeller changes pitch into a fine (or negative) pitch while the engine keeps turning at its high rpm. NSI will be offering a 79" 2 blade prop. There are several different reductions available: here is a cut from their webpage...

    ...Our Turbines are designed for output speeds of 2,000; 2,250; 2,500; 2,750; 3,000; and 3,600 RPM. We recommend the use of 2,750 RPM for fixed-wing aircraft applications....

    The controls that will be used for the NSI CAP200 prop are electric. You control the prop blade angle while the FADEC fuel control unit meters fuel to keep the engine speed a constant. There are two engine speeds, and thus prop speed settings. High and low. The low setting is for ground operations and will keep the noise level down.

    One thing to consider is the prop material. I think the NSI is a composite. Is a composite prop acceptable for back country use? Since the prop has to be a variable pitch & reverse capable to work with a turbine engine, I don't know if there are any good alternatives. I'd be curious to see what you've heard

    G.

  3. #43
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    Quote Originally Posted by geoffmeyer
    I've spoken a bit to the owner - charlie - at Innodyn. He says the engine will and does have reverse.
    I wrote to Innodyn asking these sorts of questions but never got a reply so this information is especially welcome. Thank you!

    The videos also look quite impressive. I hadn't seen them before.

    I really like your description of how the system operates. It really does seem idiot proof. That sort of meets some of the questions raised at the beginning of this thread about how difficult it would be to operate under the stress of STOL conditions. Sounds like it will be almost impossible to damage the engine.

    What problems do you see in using a composite material prop?

    One thought that comes to mind is the sound. I personally find it an enjoyable sound. But I wonder how loud it will be in real life and whether this sound will be appreciated? Ditto the smell.

    I'm also wondering what the criteria might be for choosing different engine RPM's and why 2750 is recommended as ideal.

    Stephen

  4. #44

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    I'm not too sure it would be that idiot proof. Innodyn says the FADEC will control the fuel flow so that the engine won't exceed temperature limits. That will help from toasting the turbine. I'm not really sure how it would work if you dialed in too much of a prop pitch though. From what I understand, as you add prop pitch to a coarse setting, the prop & engine rpm will want to slow. The fuel control unit will add fuel to counter this action....what if you add too much pitch? Will the engine just slow down once its maxed out on fuel flow, or maybe the turbine temp will begin to rise & consequently, the FADEC will reduce fuel...? That's a question Innodyn could answer, but I haven't asked them yet.

    I agree with the Pilatus PC6 guy - turbine operation is not something to be intimidated about. I think operating & learning the in's & out's of a turbo-charged or even normally aspirated piston is more difficult.

    I hope someone else answers about the composite prop. I know nothing about props. I've heard that the best is an aluminum one because it can take abuse & then re-shaped -where the composite prop has a protective metal leading edge that is not so reshape-able?? - just a guess though.

    I've operated the garrett engines & know how loud they can be on the ground & in the air. The reason is the prop is always spinning at a very high speed. Even when sitting still. I've asked Innodyn about this & they say the engine will run at a lower 1400rpm speed for ground operations. At that prop speed, there shouldn't be much noise.

    I'd try to pick the lowest turning engine option, and put the largest diameter prop possible (with reasonable clearance). As of now, the largest prop they have for this engine is the 79" CAP200. At an engine rpm of 2750, the prop tip speed would be .86mach at 2000'msl & 50kts.

    Sounds like you & I are interested in the same application of this engine. The majority of their interest is in the RV crowd. I'd be really thrilled to fly this engine if its what they say it is. Lets hope their supercub project proves to be a good performer!

    G

  5. #45
    mvivion's Avatar
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    Ernie,

    Not sure about the French powered Porters, but the PT-6 Porter is flat rated at 550 hp, not 650. I suspect the Astazou engine is as well in that application.

    As to the larger fins on the Turbine Beaver, note that the Wipaire Turbine Beaver uses the standard Beaver tail. The original deHavilland Turbo Beaver had a 30 inch long fuselage plug inserted into the fuselage to increase cabin volume, and get the engine out front for W & B purposes. With the longer fuselage forward of the center of lift, they then had to increase the size of the vertical tail to compensate. Wip didn't extend the forward fuselage, so increasing the tail wasn't required, and they used a 715 hp engine, I believe.

    All this is to say that the size of the vertical tail on these airplanes was dictated by yaw stability, rather than power.

    MTV

  6. #46
    AlaskaAV's Avatar
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    Quote Originally Posted by mvivion
    Ernie,

    Not sure about the French powered Porters, but the PT-6 Porter is flat rated at 550 hp, not 650. I suspect the Astazou engine is as well in that application.

    As to the larger fins on the Turbine Beaver, note that the Wipaire Turbine Beaver uses the standard Beaver tail. The original deHavilland Turbo Beaver had a 30 inch long fuselage plug inserted into the fuselage to increase cabin volume, and get the engine out front for W & B purposes. With the longer fuselage forward of the center of lift, they then had to increase the size of the vertical tail to compensate. Wip didn't extend the forward fuselage, so increasing the tail wasn't required, and they used a 715 hp engine, I believe.

    All this is to say that the size of the vertical tail on these airplanes was dictated by yaw stability, rather than power.

    MTV
    Needless to say I could be wrong and usually am but as I recall, the PC-6 Porters that we ordered with the PT-6 engines was a model that produced 650 shp but it has been almost 40 years. Side by side with the same load, the PT-6 powered Porters would out perform the Astazou hands down. Forget the one recip we had.
    The performance of the turbine Beavers and Otters I have no personal knowledge about other than they are one heck of an aircraft.
    One thing about a Porter: do not touch down tail wheel first or you will get several wrinkles in the fuselage just forward of the tail wheel.

  7. #47

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    The last thing I heard....

    Guys,
    The last thing I heard was that the ATP Turbine was going to be over $30.000, but could be $50000. The cost of the engine doesn't include the prop or spinner either. In order to get one, somebody's going to have to shell out a small fortune. My question is, is it worth it?

    Mike

  8. #48
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    Re: The last thing I heard....

    Quote Originally Posted by CptKelly
    Guys,
    The last thing I heard was that the ATP Turbine was going to be over $30.000, but could be $50000. The cost of the engine doesn't include the prop or spinner either. In order to get one, somebody's going to have to shell out a small fortune. My question is, is it worth it?

    Mike
    The 185hp Innodyne is $28,500. True, you need to add prop, spinner but you also need to do this for Lyco-saurs. One thing to keep in mind is TBO is 5K. So you get two engines essentially, right?

    It still begs the question of whether it's worth it. If I go Lycosaur for my experimental - with initial savings over turbine I can go buy a float kit probably. Of course if you have a love for turbines in general, who can put a price on that?

    Bugs

  9. #49
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    Cost & time

    Quote Originally Posted by CptKelly
    My question is, is it worth it?
    In general, if it fulfills all of their promises then there is no question it is worth it.

    But on some of the specifics I do have a cost issue. Innodyn has appointed Firewall Forward as their provider for mounting kits:

    Rivers Aeronautical

    The cost of this product seems to me to be quite high (their estimated price is US$12,500 on an RV aircraft). This significantly increases the cost of the engine and I am not sure what is really in these kits that justifies the price.

    I also see a second, and maybe bigger problem. Rivers Aero is obviously going to concentrate on the RV series first. That will leave people such as us who are probably viewed as a niche part of the market out in the cold.

    What I'm wondering is how many people can reasonably be expected to mate the Innodyn turbine to a Supercub? I am specifically wondering if it might make sense for us to form a group to develop a mounting kit for ourselves? This might be the cheapest and quickest alternative.

    My personal feeling is that I want to actually have a Supercub in the air and get some sort of pilot report on how it flies before I commit to going the turbine route. But I am hoping that this will happen very soon.

    Stephen

  10. #50
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    Wasn't it noted by the developer or someone on this site this spring that there was a Cub with the turbine on it either flying, or "imminently" flying? I remember making the gaffe on here of suggesting that the same turbine cub was at S N F this year as last, and the answer was that this was a different cub.

    What happened to the one that had the engine mounted last year (2003) at Sun N Fun? Or is this a different engine conversion?

    Just curious.

    MTV

  11. #51
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    Yeah a turbine engine can burn almost anything, even that expensive bottle of Scotch you have in with your fishing gear, but that doesn't mean you should burn just anything in one. If you burn fuel other than those approved for normal use (Jet A, A-1, B) they fall into the emergency fuel category, you might be able to get home, but start saving for a new engine.

    This guy builds Yukons with a 120 hp turboprop option. Fuels ? Diesel, Bio Diesel, Jet A, JP5, JP8 and Heating Kerosene.


    http://www.watsongroup.ca

    In idea is always good, back when it was an idea.

  12. #52
    highroads's Avatar
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    In my prior life I worked on the certification of the Garrett engines for Ag operations using Diesel fuels. We found little difference in performance, function and turbine life. Turned out that the jet fuels and diesel fuels were almost indistinguishable chemically, the only cancerns were quality controls for diesel were not regulated by law as were the jet fuels.

  13. #53
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    The arctic grade diesel fuel produced by a small refinery owed by ARCO on the north slope of Alaska at Prudhoe Bay was tested by both Boeing and P&W and found to be the same as Jet A-50 with just a little more sulfur. It was certified for use in all of our turbine powered aircraft.
    At 50 degrees below zero on the ground, there were no gelling problems when being used for vehicles and generators and needless to say, none in our aircraft either. There was no limit on the amount we could burn but normally for our 737s, we ran round trip fuel and at times, even defueled into our storage tanks when we could.

  14. #54
    Crash's Avatar
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    Turbine

    I still would question the ability of a turbine engine on a Cub to work as good as a recip in a tight situation where you need to "blip" the power to get over an obstacle. All the turbine engined aircraft I have ever flown in seemed slow to respond and every thing was done smoothly with long approaches and no jockeying around. Crash

  15. #55
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    Re: Turbine

    Quote Originally Posted by Crash
    I still would question the ability of a turbine engine on a Cub to work as good as a recip in a tight situation where you need to "blip" the power to get over an obstacle. All the turbine engined aircraft I have ever flown in seemed slow to respond and every thing was done smoothly with long approaches and no jockeying around. Crash
    This is true for jet aircraft. But when you are working with a turbo prop, and I will use our PC-6 Porters as an example, they are flown different.

    On approach when there is a sudden need for power for an abort or whatever, you are already at say N1 of 83% and with just a little prop cranked in to keep speed where you want it. Go into ground fine and you have a big airbrake out front. When you need that extra power, there is no spool up time, only the time it takes to change the prop configuration and that starts almost immediately.

    Having been around our Porters for several years, recip and turbine, I have to believe the Cubs with a recip and turbine comparison would be the same as our Porters with a recip against a turbine powerplant.
    A person has to fly them totally different but there should really be a great gain if performance. Needless to say, a loss of weight but the difference in fuel weight takes most of that away.

    Something else to consider about a turbine powered Cub. Fit the aircraft with long legs to keep the prop higher and away from the gravel or other foreign items. A person will be turning the prop at high RPM far longer than with a recip engine.

  16. #56
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    A single shaft turbine such as the ATP or Garrett are typically running at or near 100% RPM during landing and take off. Thus no spool up time is required. On the Garrett engine, for a power lever slam, the time from minimum power to full power was under .5sec. or in other words just the time to move the Power lever and slew the prop. The time was dictated by the propeller slew rate as the turbine is already at speed. A PT6 or similar free turbine engine will take a little more time because of the gas generator spool up time. A reciprocating engine with a constant speed prop will also be controlled by the propeller slew rate. The propeller slew rate is going to be insignificant in most cases as the average pilot is going to move the power level (throttle) deliberately with haste but not in a slam fashion even in an emergency situation.

  17. #57
    AlaskaAV's Avatar
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    Quote Originally Posted by highroads
    A single shaft turbine such as the ATP or Garrett are typically running at or near 100% RPM during landing and take off. Thus no spool up time is required. On the Garrett engine, for a power lever slam, the time from minimum power to full power was under .5sec. or in other words just the time to move the Power lever and slew the prop. The time was dictated by the propeller slew rate as the turbine is already at speed. A PT6 or similar free turbine engine will take a little more time because of the gas generator spool up time. A reciprocating engine with a constant speed prop will also be controlled by the propeller slew rate. The propeller slew rate is going to be insignificant in most cases as the average pilot is going to move the power level (throttle) deliberately with haste but not in a slam fashion even in an emergency situation.
    Pretty close to my thoughts although I was not around the Garretts that much even though we ran them in our Skyvans. I was not aware the Garretts could move the prop that fast and our drivers really didn't like them. Not enough power they kept saying. I did miss being able to go into feather when shutting the Garretts down as with the P&Ws since it was so much safer for our passengers. For some reason I remember the PT-6s and props that we ran on our Porters could change the prop positions much faster than what was able to be done on our Twin Otters with a different model of the PT-6 but of course, I could be wrong. Something, maybe knowledge, keeps reminding me that we ordered our P&W powered Porters with a different PT-6 engine model than normally used at the time back in the 60s. As I recall at the time we ordered our Porters, there were something like 4 different models of the PT6 engine available at the time but than again, that was 40 years ago and I sure hate to start an arguement over an engine and prop setup on new special order aircraft we purchased so better back out of this one. But after flying them, I suspect I might have some idea of what we were flying.

  18. #58
    highroads's Avatar
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    The Skyvans had the Garrett "Century" engines installed which were thermodynamically rated at 715 shaft horsepower. The Skyvan could have used a bigger engine but shorts never went for the larger engine. Later Shorts created the SD360 with the PT6 and dropped the Skyvan. Many Skyvan's remain in service today because that large box with loading ramp could carry oversized cargo and the airplane had a lot of versatility. There was a version of the Porter which had the Garrett engine in it. It was rated at 575 hp and had inflight Beta mode capability. The engine installation was done in Phoenix by Garrett and was produced in production by Fairchild for the CIA for Vietnam operation. It had spectacular performance, able to get into and out of postage stamp sized strips.

  19. #59

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    Stephen - I think you are correct. The cub is on the back-burner at Innodyn and Rivers Aeronautical. Can't blame them. The RV is such a big market. If you want to do this installation yourself, or have someone do it, they will sell the engine and allow you to bypass Rivers Aeronautical. They don't advertise this, but I think they are starting to change their attitude. If you call Innodyn & ask for Charlie, he can tell you more.

    This may interest you - all the engines they sell - from 160-255hp are the same weight (188lbs dry). What they are doing is de-rating them, like P&W, GE, CFM...etc. The 255hp engine has a $34,500 price (although they claim the TBO will be the same on all of their engine models, I don't know if I believe that yet. One of the reasons the engines on airliners are purchased de-rated is for improved engine life). The prop, spinner & controls are roughly $6000. You could then spend another $12000 with Rivers, or take it to someone else (which is what I'm doing). The plenum (air flow control) is something else that will probably have to be purchased from Innodyn - they don't have a price on it yet.

    It will be hard to beat the power to weight ratio of the 255hp version of this engine, and if it runs as advertised, it should save money in the long run....If you show interest by calling Charlie, I think it will help push their cub project along.

    G

  20. #60
    AlaskaAV's Avatar
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    Interesting Don. I was not aware of the Garrett mod. I knew they were using the Astazou powered Porters in Vietnam. We had a couple and they didn't perform anywhere near our P&Ws and forget the one recip we had, 09Z. It was almost useless for us due to lack of power.

  21. #61

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    First, the idea is great. Second, you damn know this game :P Certainly it has to be with CS prop (to eliminate your worries, which are true). My comment; you will have to place the engine almost two times further ahead, and the inertial forces acting on the engine mounts will be too much, compared with the reciprocating engine (too many high rev. parts like turbine, gear train and all that). So be carefull with the engine seperation danger.

  22. #62
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    Quote Originally Posted by Ahmet Kamil
    you will have to place the engine almost two times further ahead, and the inertial forces acting on the engine mounts will be too much, compared with the reciprocating engine (too many high rev. parts like turbine, gear train and all that). So be carefull with the engine seperation danger.
    I wonder if this is true. I would expect vibrations to be less on a turbine engine than a reciprocating engine. So I would expect less fatigue problems and not more. Is engine seperation really a risk? I don't hear of many accidents of that nature.

    Also, if the aircraft is being engineered from the beginning for a turbine engine, surely it would be possible to adjust the design to take advantage of the lower engine weight? At the least, I would expect that more components could be moved forward. Though maybe there is a limit to what can be moved forward...

    Stephen

  23. #63
    AlaskaAV's Avatar
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    Quote Originally Posted by FixedWing
    Quote Originally Posted by Ahmet Kamil
    you will have to place the engine almost two times further ahead, and the inertial forces acting on the engine mounts will be too much, compared with the reciprocating engine (too many high rev. parts like turbine, gear train and all that). So be carefull with the engine seperation danger.
    I wonder if this is true. I would expect vibrations to be less on a turbine engine than a reciprocating engine. So I would expect less fatigue problems and not more. Is engine seperation really a risk? I don't hear of many accidents of that nature.

    Also, if the aircraft is being engineered from the beginning for a turbine engine, surely it would be possible to adjust the design to take advantage of the lower engine weight? At the least, I would expect that more components could be moved forward. Though maybe there is a limit to what can be moved forward...

    Stephen
    Stephen
    I will stay away from the Super Cub Turbines since I am only learning about them but will pass on what knowledge I have about our Porters but the principals have to be the same.

    We had both the recip and two different models of turbines. Needless to say, the recip was mounted close to the fire wall and the turbines really stuck out much the same as a modified Beaver and Otter and other older aircraft modified to take turbine engines, even the DC-3s. We never had any problems with the extended nose and engine mounts, mainly because of the lack of the torque problem, only the strength of the fuselage just forward of the tail wheel was a major problem so we, in a way, had to rebuild that area.

    Remember, with a turbine, you have almost no torque to worry about during takeoff and in flight as there is with a recip. Very little vibration as mentioned before and any vibration usually comes from a nicked prop durring take off. Just consider the number of moving parts in a turbine as compared to a recip. As I recall, every one of our Porters carried a file just in case.

    An interesting thing about a turbine Porter is that a person can stand in front of the prop and hold it with a hand, maybe two, while the engine is lit up and all that happens is that the prop bends a little if it is in feather as is the usual shutdown procedure with the P&Ws. At somewhere near N1 45%, the person has to let go though. There is no direct gear box from engine to prop, only to the generator/starter, the same unit using reverse current power, and that is on the back side of the PT-6 model we used. The Porters carry a couple of very heavy deep cycle batteries in the nose behind the engine so that helps with W&B. I suspect each battery weighs close to 90 pounds each.

  24. #64

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    Here are the numbers I have for the weights. If they look off, please correct them. They are estimates, as I have not weighed any of these items myself.

    188lbs: Engine (power head, gear reduction unit, prop flange, starter, alternator, fuel system, fuel computer)
    47lbs: Prop (NSI CAP200):
    10lbs: Engine mount
    4lbs: Exhaust
    50lbs: 2 Batteries
    2lbs: Battery cables & fittings
    4lbs: Fuel Pumps (2)
    12lbs: Cowling
    8lbs: Header tank
    8lbs?: Plenum

    So approximately 333lbs firewall forward. Anyone have numbers on an O-360 (firewall forward weights - apples to apples comparison)?

    Geoff

  25. #65
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    Quote Originally Posted by geoffmeyer
    Here are the numbers I have for the weights. If they look off, please correct them. They are estimates, as I have not weighed any of these items myself.

    188lbs: Engine (power head, gear reduction unit, prop flange, starter, alternator, fuel system, fuel computer)
    47lbs: Prop (NSI CAP200):
    10lbs: Engine mount
    4lbs: Exhaust
    50lbs: 2 Batteries
    2lbs: Battery cables & fittings
    4lbs: Fuel Pumps (2)
    12lbs: Cowling
    8lbs: Header tank
    8lbs?: Plenum

    So approximately 333lbs firewall forward. Anyone have numbers on how much an O-360 firewall forward weighs? (Apples to Apples comparison)

    Geoff
    Geoff
    Numbers look good except for maybe the batteries. I know pretty well what the Porters carried but have no idea what the APU engine will need for the Super Cubs.
    Although I am not aware of what will go into the Super Cubs, I have an idea of the weight of the APU in say a 737. I have a feeling your weight of the engine is very close to accurate.

  26. #66
    Flying Dave's Avatar
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    I could have sworn I saw a SC at OSH this year that appeared to have a turbine installed and looked to be in flying condition. I did not get a chance to see it up close so I can not confirm the engine installation. Anybody else see it or was I seeing things??

    Dave

  27. #67
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    An analogy might be the Maule piston vs the Maule turbine (Allison)

    ..................................Piston.......... .................Turbine
    GW.............................2500............... ..............2500
    Emp Wt.......................1665..................... ........1570
    T.O. pilot,1/2 fuel.........250...............................200 ft
    T.O. ovr 50ft. obst........600...............................600
    Fuel flow cruise............11gph........................... .25.9gph
    Cruise speed................160mph....................... .190mpH

    Some of the weight gain of the turbine is offset by a heavier (3bld) prop. required to handle the extra power. heavier mount system, fire protection, etc. On big turbine engines vs big piston engines the weight improvement is far more significant. With little turbines the percentage of the total powerplant that is turbine is smaller thus weight gain smaller.
    More info can be gained from the Maule website
    http://www.mauleairinc.com/Our_Planes/index.html

  28. #68
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    Battery power & gross weight

    Ernie pretty much confirms my own thinking on this ? that there shouldn?t be any particularly big problem with mounting a turbine engine verses a reciprocating engine and in many way, it might be simpler.

    I am wondering if the Innodyn engine is going to need the same level of battery power to crank that engines in aircraft such as the Porter do? Surely the smaller engine would require less? Also, since this is an Experimental catagory aircraft, are there better batteries out there that might be used for this purpose?

    The component weights that Geoff and Highroads list pretty much suggest that there isn?t going to be a massive difference in the weight distribution of the aircraft and probably moving a few items forward would make a big difference. Query, if the airframe is being built from scratch, what is to stop someone from actually moving the windshield and firewall slightly forward?

    But one thing Highroads points to really makes me think. He lists the gross weight of the Maule as the same for both piston and reciprocating versions. But the Turbine Supercub will be certificated in the Experimental category and the Innodyn engine is available up to 255 hp. This additional power comes with no weight penalty. Query, with so much power available, is there any reason why the builder shouldn?t certify the aircraft to a higher gross weight? And if so, what is possible with a Supercub with so much power? Is it possible that we could end up with a Supercub weighing almost 100 lbs less and with a new higher gross weight?

    Stephen

  29. #69

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    I believe gross weight is a function of several things, including wing & strut structure.

  30. #70
    FixedWing's Avatar
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    Gross weight

    Quote Originally Posted by geoffmeyer
    I believe gross weight is a function of several things, including wing & strut structure.
    So what I'm wondering is, what is the limiting factor on a Supercub? Is it available power? Or is it something else?

    Have any Supercubs been certified at higher gross weights?

    Stephen

  31. #71

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    Can't be certified for higher gross weights I think, because the specific fuel consumption of recip, sweeps away the weight advantage gained by turbine (11GPH versus 26 GPH). Nobody has any objection if you will be happy with 1 hour range

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    Turbine super cub

    Ernie, why does a turbine have "almost no torque to worry about"? Yer still twisting a prop that makes gobs of thrust. Don

  33. #73
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    Re: Turbine super cub

    Quote Originally Posted by puttputt
    Ernie, why does a turbine have "almost no torque to worry about"? Yer still twisting a prop that makes gobs of thrust. Don
    Don, I believe I stated as compared to a recip engine configuration. You do not have all the moving parts to create the torque.
    Flying a turbine is so smooth that it can get a person into trouble until the person gets used to it. In a recip, say on departure, you have to always keep ahead of the heading and in a turbine, a person can concentrate more on performance.

    I may not be saying this correct but it is unbelievable what the difference is.

  34. #74
    Bob Breeden's Avatar
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    Smith Turbine Cub

    Has anyone in contact with the Smith father and son team in Ontario heard about the current status of the nearly complete Innodyn powered Smith Cub that was at Oshkosh in Olive Drab paint? Many SuperCub.org members saw that Cub at the Innodyn booth. It sure stood proud on extended gear and tall tires with that long nose!

    My recollection was that this was being built for or by Mr. Smith.

    Is it flying yet?

    What has the flying experience with this aircraft been like?

    Thanks,
    Bob Breeden

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    I spoke with Innodyn yesterday. The Turbine cub is not flying, or finished. They say it is close & will possibly be flying within a month...lets hope!

  36. #76
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    So, what happened to the turbine Super Cub which was at Sun N Fun in 2003? It was assembled and on floats, but uncovered. When I noted that it appeared the same airplane, in the same condition, was at Sun N Fun in 2004 with no apparent progress, someone noted that this was a different airplane.

    So, again, where is the airplane that was at Sun N Fun 2003? Seems like if it was this close to completion then, and experimental, it should at least be about ready to fly.

    It appears that there are at least two Cubs with these little turbines on them somewhere. Just curious where.

    Note that there is an RV currently FLYING with one of these engines on it. Considering that the RV is a much shorter aircraft, it appears that they figured out the W & B issues adequately on it. Doesn't seem like the Cub would be that much more difficult.

    Fuel burn will be a big issue.

    Ernie, turboprops still make massive amounts of torque and p-factor, related to the prop, not the engine, though there may be some difference in engine torque.

    Note that the military, when they designed their new turbo prop trainer, made by Raytheon, (I believe) specified that the airplane had to have an on ground yaw damper to counteract the effects of p-factor and torque TO BETTER SIMULATE PURE JET powered aircraft.

    You are correct in that turbojet powered aircraft exhibit no left turning tendency on the ground, but turboprops sure do.

    MTV

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    The Innodyn engine is advertised to burn roughly 7gph per 100hp below 10,000' (this figure improves at higher altitudes). That makes sense, especially when you compare with other turbo-props. The Allison 250-B17C engine burns about 20gph at a cruise power setting of 310hp (6.45gph per 100hp). The Walter M601D burns 65gph at 657hp (9.9gph per 100hp). The innodyn falls somewhere inbetween these two. So power back the 255hp Innodyn to 150hp in cruise. You should burn roughly 10.5gph. I don't know much about the pistons - how does that compare to an O-360?

    Geoff

  38. #78
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    Thanks, Geoff.

    Hi, Mike.

    I sure am comfortable flying behind a trusty Lycoming when crossing the Inlet exploring western Alaska, but nonetheless, there may well be a time and place for a Turboprop Cub.

    Especially in the drama/performance department. I have thought alot about the turboprop aerobatic aircraft that flamed out while doing square loops at a constant airspeed, and couldn't be safely deadsticked from low altitude because of the drag of the windmilling prop, the prone-to-stall wing, and the light weight of the aircraft. That pilot suffered permanent backbone compression related injuries.

    Safe drama/performance for the Super Cub would include what others have thought of, which is even more stellar takeoff performance. And, as others have mentioned, safe drama in the landing phase will also require some quick, smooth, reliable, controllable and intuitive use of beta.

    There is nothing like the millions of hours in nearly every wise (and otherwise human) use of the certified piston powered cubs to establish a refinement in safety we now utilize daily.

    It will be interesting to see how smoothly, and utimately successful, the accomodation of and transition to Turbines can be. I certainly applaud those who think this endeavor through and do so successfully.

    Bob Breeden

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    Bob,

    The Salinas Airshow turboprop crash you refered to, at least according to the NTSB, was pilot error. The Pratt & Whitney said the teardown showed the engine developing middle to high power at impact. I've talked to Wayne a couple of times since the accident and he would beg to differ!

    He was landing out of a loop (a vertical eight I believe), descending at 50 to 60 degrees nose down, something that required very precise airspeed and drag control, and he said it didn't power up immediately when he brought the prop out of beta, so he couldn't get up the speed necessary to round out at the bottom to land.

    It's probably related to spool-up time. It doesn't take long to go 800' down at that kind of deck angle, and it's probably not the kind of flying anyone would consider in a Super Cub, turboprop or not!

    The factual report is here: http://www.ntsb.gov/ntsb/GenPDF.asp?...00LA003&rpt=fa

    The probable cause report is here: http://www.ntsb.gov/ntsb/GenPDF.asp?...00LA003&rpt=fi

    Tom

  40. #80
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    Tom,

    Thanks for the links. Having now read both, I can see that, from the NTSB perspective, this was pilot error. And you are right, descending 800 feet at a 50 or 60 degree angle at 80-90 knots only takes about 9 seconds, (figuring the vertical component to be 60 mph). I figure that changing from Beta to forward thrust would have been in the last 200 vertical feet, which only gives 2 seconds to obtain forward thrust and flare.

    If it is pilot error, as the NTSB asserts, check out that Wayne Handley had 25,000 hours, and 200 plus in this airplane, and that didn't save his landing. Yes, as an aside, he had the pressure of the crowd, and the extra enthusiasm that comes from that (not good) but he was used to that.

    It is imperitive, to my way of thinking, to read about this accident and look at how that could be waiting to trap a turboprop Super Cub.

    First, we land our Cubs as short as we can, over obstacles. Idle thrust, full slips at full flaps, at stall plus one knot, with a touch of power to round out at the bottom. A short dive at the bottom to get the necessary airspeed to flare is safer, but still we use power to flare sometimes. Or even drag it in, working way out on the backside, hanging on the prop. This is routine stuff to muster the best performance out of our Cubs. It is not a stretch to suggest that we would not learn to use beta, to descend even steeper, and if our timing is not spot on, incur a similar event as described in this accident report. The report states that the turbine and prop were pulling hard at the time of impact. That power was just called for a second too late, which could have been affected by gusts or other variables as well.

    The Super Cub is such a fine machine to learn to fly well, and safely, in the full range of its performance. I hope that the turboprop can be incorporated, with all it additional capabilities, just as safely. A Cubs inherent stability, high lift wing, powerful tail and slow flying capabilities which give us long times to react will make this kind of accident less likely than on the aerobatic plane. But such a Cub, flown in this manner, will become dependent on the engine and prop both operating, and being operated perfectly, every time. So much for landings.

    Takeoffs with 255 hp at 35 mph will have a deck angle of over 60 degrees as well - and may even be vertical in gusts. The time required for pitchdown in the event of engine failure, or to break a stall, will be even longer that that of a light cub climbing at 35 mph under an 8241 prop. Fuel systems will have to be be designed to carry fuel the 3 vertical feet up to the engine.

    Ernie, how did the Porter get fuel to the engine, and how much time did your crack pilots take to master flying it the way you have described in your writings? Were there accidents with the Porter related to max performance takeoffs and landings?

    Bob Breeden

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