Small Aircraft Transportation System

At one time NASA promoted SATS – What happened?

In the mid-1990s NASA created a program to revive general aviation and transform piston airplanes into reliable transportation machines that could be safely operated by pilots without thousands of hours of experience. The hope was to create a small aircraft transportation system (SATS) that would allow people to travel with convenience and predictability between the thousands of airports in the country that are not served by scheduled airlines.

The general aviation industry applauded. Richard Collins and I scratched our heads. We, and many thousands of other pilots, had been SATS participants for decades and didn’t even know it. We used our airplanes for transportation and essentially matched the schedule reliability of the major airlines, which was a bit of a challenge then, but not that difficult now. What would SATS do that we didn’t? 

The answer to that question is that SATS would skip over the hundreds, and even thousands of hours pilots like Richard and I had spent slogging through the weather with only basic avionics and hard-earned experience to keep us alive and on time. If SATS were to succeed new pilots needed to move quickly into routine IFR flying in order to use their airplanes for reliable transportation.

SATS promoted benefits such as expanded same-day regional travel.

To make SATS a reality NASA created Advanced General Aviation Transport Experiments (AGATE), which would lead to new aircraft systems that would make the airplane easier and safer to fly in almost any weather. Most of the AGATE focus was on autopilots and cockpit displays, including Highway in the Sky (HITS), that NASA believed could make controlling an airplane under IFR easier.

I won’t say that AGATE contributed nothing, but as is often the case, technology zoomed ahead of the groups meeting to discuss what is possible. Flat glass technology made the PFD available at piston airplane prices before AGATE believed that would be possible. MEMs sensors developed mostly for auto industry skid control systems quickly found their way into aviation in the form of low cost attitude heading reference systems (AHRS) replacing the vacuum pumps and spinning metal gyros.

WAAS GPS made precision type approaches to thousands of runways not served by ILS. And perhaps most useful, extremely powerful satellites were put in orbit that could send down real-time weather to a receiver using nothing more than a GPS-sized antenna. AGATE didn’t see XM coming, and neither did I, nor many others. We were all focused on a ground-based network that would transmit weather up to airplanes, not down from space.

The one company that whole heartedly embraced SATS was Cirrus. Alan and Dale Klapmeier from the beginning intended for their Cirrus airplanes to be traveling machines. The standard equipment autopilot, advanced avionics, and, yes, the parachute, would all make it possible for a pilot to learn to fly and very shortly be using their Cirruses for on-purpose and on-schedule transportation.

The SATS program promised the “radius of action of daily life” would increase by an order of magnitude not seen since “cars displaced horses for intercity travel.” All photos courtesy sats.erau.edu

They also designed a dedicated training system for Cirrus pilots, and continuously emphasized the need for standardized procedures to aid safety. And it worked. After getting past early production and funding challenges, Cirrus built 5,000 piston singles in very few years.

When Cirrus got rolling I started to hear about relatively new Cirrus pilots flying their airplanes 400, 500, or even more hours per year. I found that hard to believe. I have flown more than 400 hours for several years in my life, but that was part of my job. And that is a lot of flying. But it was true. SATS was coming to life for many Cirrus owners.

As general aviation went into its current decline the frequency got awfully quiet out there when I was flying on bad weather days, but when I heard other pilots, they were most often in a Cirrus. Like me, they were going someplace on purpose, using their airplanes for transportation.

 

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49 Responses to Small Aircraft Transportation System

  1. I know of one couple (both pilots who probably read this) that flew their new SR22 enough the first year that they took the engine to TBO. Now that is really a lot of flying.

    If I recall correctly, Cirrus did have some initial safety problems as pilots were flying the planes like fixed gear planes when they perform like high performance, complex, retracts even if the feet are “down and welded”.

    Cirrus put everything together in a nice package and at the right time.

    I have to admit that I do not like the side yoke…half yoke…that they call a stick and much prefer a Bonanza and even more a Bo with a panel like the SR22 even though now retired I have no need and it/they are both outside my budget.

    • Dov Elyada says:

      My airplane is a battered ICP Savannah with a Y-shaped stick between the front seats, intended as a dual control. Despite being a 68-years old 100-hrs novice when starting transition to that type, it took me no effort at all to get used to it.

      But there’s a catch: Even after being trimmed to the max, that aircraft still needs a slight constant right stick force to keep it from rolling left. Now just think of what this means for a pilot who wants to note down an ATIS message but is no good in writing with his left hand.

  2. Karl Schneider says:

    I can deal with a ‘joystick’ for chairborne activities but I still want a wheel, yoke or a regular stick in a real airplane. I guess I’m too old to get over that…and hell, I’m still way more comfortable with steam gauges than this fancy breakable glass stuff haha.
    Hey Roger, how do you pronounce your last name?

  3. Herb says:

    Having downsized from B-17′s of an earlier era to ny present Ercoupe 415C and LSA
    flying (along with aging from the roaring 20′s to the present 97) I have no need for the
    grandeur of a glass cockpit, but …. flying is still flying, and all the fancy instrumentation in some of today’s planes doesn’t substitute for common sense, good judgment, respect for the inate dangers involved whenever taking to the air, and trust that your equipment airworthy! ,,,,, plus a few unspoken, but sincere Amens!

  4. derbyrm says:

    My Cessna 172 M, 1974 with steam gauges, has provided me with a fine SATS for the last thirty years. Particularly now, with “security” rampant, I can equal or beat the Part 121 operators from home to motel in most cases. For the really long flights, the stop-over is part of the fun. My schedule is NOT that vital.

    GPS has taken the challenge out of navigation :-( and made keeping the numbers precise much more important than they should be.

    Finding a motel that will tolerate my dog and my smoking is the biggest challenge.

    • I truly love flying behind the glass panels. They are very easy to lean “IF” some idiot company doesn’t insist that you learn the entire system at once. Jumping in and filing IFR right off the bat is not the way to start. Starting out basic and taken in stages, such as just using the basic functions along with weather, then adding simple flight VFR flight plans, then inserting way points, then changing way points and working up to the IFR flight where ATC is rerouting you… and “highway in the sky” …

      I still want/insist on back up steam gauges though. Redundancy and independent back up … which is why I oppose going entirely to GPS. A satellite system needs a ground based back up although I do believer if LightSquared is allowed to go ahead we are going to need more than that.

    • SkyKing says:

      Steam gauges are the way to learn.
      Start with the basics, like crawling before walking before running.
      But once having learned by steam gauges, continue the steep learning curve on glass. Once having learned a new scan, and to process the additional critical information while still flying and enjoying, one shudders at the foolish risks they used to take unwittingly with only steam gauges, and is strongly reluctant to return, although they can.
      Resisting learning glass is parallel to the old codgers who refuse to get or learn a computer, where their real reason is their fear of not being able to keep up and appear stupid in front of younger people. Unfortunately, the longer one waits the more difficult it gets, and the more cemented they become in their intransigence. And the fear of being embarrassed is unwarranted. Just do it.

      • I guess I’m one of the “old guys” but I don’t see any steep learning curve with glass. It all depends on how you approach it. Learn to use the “glass panel” the same way we use steam gauges. The only real difference is every thing, or nearly everything is all on one display so the scan (for IFR) is much simpler than using steam gages. Everything is in your field of view without having to shift where you are looking, at least I don’t. All information is within just a few inches of each other. Just go out and fly VFR with the thing to get used to it. AI is in the center which also includes pitch, Airspeed and altitude are on the sides. Heading is displayed on a graphic representation of a DG, but also in a window.

        I found learning a glass display to be little different than learning the panel when I first started flying. As I was used to flying IFR I found the new glass panel to be easier than steam gauges.

        There are “to me” only two difficult parts to a glass panel. The one is non standardization between companies and when inputting, deleting, and changing waypoints. Most are not really intuitive.

  5. Robin Oldfield says:

    Mac: Was a propulsion initiative also a component of AGATE? I recall the FAA giving Williams International $75M to develop a lower cost turbine and Continental $25M to bring to market a compression-ignition powerplant. Did Williams shelve the entire program after the Eclipse concept got too heavy? What happened to the Continental project?

    • Mac says:

      AGATE awarded competitive contracts to Continental Motors to develop a low cost engine, and to Williams International to develop an advanced small turbine engine.

      Continental opted to go for a diesel because of the inherent efficiency and more available fuel. The company built a four cylinder two cycle engine because two cycle is more efficient as each cylinder produces power on every stroke. A large fly wheel was included to try to damp “power shocks” to the crankshaft and propeller, and liquid cooling was used. The direct drive engine was rated around 200 hp.

      Continental flew the diesel some on the front end of a Cessna 337 with the standard engine in the rear. The engine met the objectives of the AGATE program, but as of yet, has apparently not met the demands of the market because Continetal has not yet produced a diesel for normal production.

      Mac Mc

      • Darrell Hay says:

        Mac,
        …”two strokes are more efficient.”
        Since when? As both an aviation bum and a diesel enthusiast I must disagree. Old Detroit Diesels sound cool, are two stroke (with a blower), but are inefficient compared to four stroke diesels. The efficiency you may be referring to is because it is diesel, not because it is two stroke diesel. Two stroke gives it better power to weight ratio, but less SFC, less longevity, less reliability, and harder starting. Same is true of two stroke gas engines (check the fuel burn on a two stroke versus four stroke Rotax for example—gimme the four stroke every day). By definition two stroke is less efficient because of inability to burn the fuel as completely as in a four stoke. Inability to engineer a valve overlap, exhaust mixing with fuel, etc etc

        • Pier Dutcher says:

          Darrell, piston-ported 2-stroke GAS ENGINES are less efficient than 4-strokes for the reasons you gave. But a 2-stroke diesel is a different animal. The supercharger does a good job of scavaging the exhaust gasses and since the diesel doesn’t mix air and fuel, you don’t have to worry about some of the fuel charge following the exhaust out the exhaust pipe. See http://auto.howstuffworks.com/diesel-two-stroke1.htm. There are plenty of 2-stroke diesels out there being used for commercial applications; believe me, with today’s fuel costs, you wouldn’t see these engines if they weren’t efficient!

          • Mac says:

            Just to expand on efficient–in this application the two stroke diesel delivers more power per pound of installed engine weight. In aircraft, that is always important. And if you are a boater, you know that two stroke outboards deliver a lot more power per pound of engine weight than do the four strokes.

            Mac Mc

        • Gordon Arnaut says:

          From an engineering perspective a 2-stroke engine will always be more efficient than a 4-stroke engine…

          This is because you have a power stroke for each revolution of the crankshaft, therefore less pumping losses for turning the machinery…also a lot fewer moving parts so you save the power required to drive a valvetrain, which is considerable…

          When you talk about a 2-stroke Rotax versus a 4-stroke, the poor fuel efficiency is due to the fact that it is a carbureted engine…a 2-stroke engine with its fuel injected directly into the cylinder, like on today’s outboard engines, are just as fuel efficient as 4-strokes and in some cases better…

          The technical reason is that a carbureted 2-stroke engine will lose some of the fuel going out the exhaust port…due to the fact that both intake and exhaust ports are uncovered at the same time when the piston is at the bottom of the cylinder…

          With direct injection (like a diesel) the fuel is sprayed when the piston is near the top and both ports are closed so no fuel can escape…

          The most fuel efficient internal combustion engines in the world are large 2-stroke diesels used in container ships and stationary power generation…as manufactured by Sulzer, Wartsila, etc…

          The Junkers Jumo 205 was a 2-stroke diesel from the 1920s that delivered better specific power and specific fuel consumption than today’s best aircraft piston engines…

          A 2-stroke is simply superior in every respect if done correctly…today’s DI outboards are a great example…they outperform their 4-stroke rivals by a wide margin, weigh a lot less and are far more reliable at duty cycles where they are required to run continuously at full power…

          Evinrude ETEC engines can run 5 hours straight at full power without a drop of oil…due to use of ball bearings…

          Plus it can run just as easily on diesel fuel as a spark ignited engine…and even switch back and forth…military is now requesting this type of engine for small drones…

          2-stroke engine technology is very exciting and could be great for light aircraft…

  6. Pingback: Small Aircraft Transportation System | Left Seat | Share My Aircraft News

  7. The jet engine manufacturing appears to be going strong in both production and prototypes. http://www.williams-int.com/information.html in a number of sizes.

    I find no mention of their current involvement with piston engines, but I could have overlooked it.

  8. What happened to it? What do you mean, that was obvious as hell, everybody shouted “Hell No We Don’t Want To Spend That Much Money!!!” I bought a beautiful old 310 with low total and engines times and new Top Props but a stock panel for nearly a pittance. So I put a G-500 and 430W in (the GTX 750 was not yet available) it. People told me I was crazy to put that much money into that plane. To this day though I can’t find a cheaper way to get a twin engine three mile a minute personal traveling plane with SVT/HITS. People won’t pay $80k for it and think I’m insane for asking. They set value on resale where as I set value on capability. The real problem is though that not enough people have experienced it. Once you experience SVT, it’s revolutionary in situational awareness and attention time management. There is no “interpreting the istruments”. The knowledge of your spacial situation is instantaneous due to what I term as eVMC display of your condition in the natural format that you have interpreted your presence and position is space-time since birth. It makes autopilots irrelevant.

    That

  9. John Patson says:

    SATS did not grab the public imagination, so was a prime candidate for the chop, when the dotcom bubble burst and times got relatively tough.
    Why it did not grab the public is probably because of cost. Most working people now see them selves owing one or more cars but not an aeroplane, as much as they like the idea of doing so.
    The first hurdle is the cost of training for the licence, before even getting to ownership or renting.
    Apart from that, it would have involved promoting existing airfields, even opening new ones.
    Politically that is something hard to do at a local level, especially as very little research money goes into making aircraft quieter.

  10. Thomas Boyle says:

    The technology isn’t quite there yet. It’s getting there. Synthetic vision, plus semi-auto-pilot technology that allows the “pilot”/driver to say what they want to do, but has the airplane itself figure out how to do it, would make it possible for “regular” people to learn to operate and use small airplanes without needing hundreds of hours of training. Conceptually, you want a system where the operator selects the destination and the airplane flies it, managing its own airspace rules and traffic avoidance. Now modify as needed so that the operator can drive on the ground and request course deviations because of things the airplane might not know about. Design the system and interfaces so a person can learn how to operate it in 20-40 hours of training plus a book knowledge exam.

    If that doesn’t sound like “flying” to you, that’s fine. What flying needs most of all is lower costs, and that comes from volume, and that requires a dramatic reduction in the complexity, and training required to use an airplane as reliable personal transportation.

  11. I’m confused, I though Continental bought rights to SMA’s engine which IIRC is a 4 stroke 230hp that has been flying STC’d on 182s for quite some time. They promised to develop a 6 cylinder 350hp version that I want for my 310D to run on algae oil.

    • Mac says:

      The AGATE engine was a technology demonstration project and was not really intended to be put into production. So, what Continental is now doing with diesel engines is not directly related to the AGATE project.

      Mac Mc

      • Robin Oldfield says:

        Didn’t Continental have versions of their AGATE funded design on display at Oshkosh for a couple years? I thought they were loooking for a airframe launch partner, but I guess it never made it to prime time. However, please comment on the Williams project. their 22 series. If it had delivered as promised, this should have been the real “disruptive” technology: a turbine for a small premium over a large displacement piston engine. My favorite idea was if they developed a turbo-prop version.

        • Mac says:

          The fundamental problem with turbine engines is that they do not scale well. The only way turbine engines can achieve any level of efficiency is by operating at ever higher temperatures and pressures. That places enormous stress on the components, particularly the compressor and turbine blades. Exotic metals are necessary, and to achieve the efficiency of a large turbine engine, the blades must be cooled.

          When you shrink a turbine engine the components become extremely small. Tiny size of a blade gives it less mass to withstand the pressure and temperature, and makes it almost impossible to circulate cooling air inside the blade as large engines do. So the small turbine engine runs at lower temps and pressure and uses more fuel.

          Enormous amounts of money were spent–mostly taxpayer money–in the late 1970s early 1980s in the wake of the oil embargo searching for a multi-fuel engine, a turbine. The research led to ceramic blades as the only way to withstand the necessary heat, but ceramics are so brittle the life was terrible. The best research small turbine couldn’t come close to an ordinary piston engine in terms of fuel efficiency.

          There is a floor for turbine engine power that is difficult to break through, and the Williams 22 engines didn’t do it. What makes sense for a one-shot cruise missile that blows itself up just doesn’t work for an engine that we want to fly for thousands of hours.

          Mac Mc

          • Gordon Arnaut says:

            For the most part turbine engines do lose efficiency as you scale down…due in large part because area increases by square while volume increases by cube…

            So your area to volume ratio becomes bigger as you scale down, which means more friction losses which are the result of wetted area on the compressor and turbine blades and wall surfaces…

            The large turbofan engines are very efficient, approaching thermal efficiency of 40 percent on the latest generation, which is better than the best diesel piston engines…

            But in order to get this great efficiency, the large turbines use very high pressures and temps as Mac pointed out…This means expensive metallurgy like single-crystal turbine blades, plus bleeding off air from the compressor and routing that through the turbine blades for cooling…

            All of this is very complex and expensive…

            This is what Williams tried to do with its FJX program that Nasa funded…a miniature turbofan trying to get close to the efficiency of the big machinery…

            It’s not going to work…

            However, there is hope for small turbine engines that ARE very fuel efficient AND very inexpensive…

            This is already proven in the microturbine industry for stationary power generation and heating…

            The key technology here is recuperation, which differs from the simple turbine engine cycle in a key way…the hot exhaust gas is routed through a heat exchanger (recuperator) which transfers the heat energy to the intake stream coming off the compressor and going into the burner…

            Result is you get free energy…and you need to burn less fuel in order to raise the working temperature to where it needs to be…

            These microturbines are getting about 30 percent efficiency right now which is about as good as your EFI car engine…The heat exchanger basically cuts fuel consumption in half or more…

            And they are doing this with idiot simple turbomachinery…basically a compressor and turbine wheel like you will find in your ordinary turbocharger…

            That’s all there is to it…in fact you could build such an engine using an off the shelf turbo…

            Only problem is that the recuperated cycle has not been made to work well in aircraft engines because the heat exchangers are quite big and can be heavy too…

            There is a long history of research going back to the 1950s…and many engines running on test stands but only one has ever flown…a recuperated Allison 250 engine in a military helo…the dual heat exchangers dwarfed the engine itself…not great for aircraft where space and weight is at a premium…

            The car companies including Chrysler, Ford and Rover had recuperated turbine engines decades ago and they got them fairly compact…the Chrysler turbine car beat the gas mileage of the piston counterpart quite handily…

            Look for some big developments coming very soon in new heat exchanger technology which promises to shrink down the size to a workable level…even the big turbofans of the future will be recuperated…

            We are very close…I happen to be involved in one such project as we speak…

            It will be a revolution in small aircraft propulsion because we will have turbine engines (turbofan and turboprop) that cost no more than today’s pistons, get better fuel efficiency at all altitudes (huge advantage up high), and have a big advantage in specific power (power to weight)…

  12. Dave Schwartz says:

    One of the biggest problems with all of these “light aircraft as a transportation appliance” programs is that they forget to include the passengers. While a true enthusiast pilot may enjoy several hours of bouncing through IMC in a cramped, noisy, poorly heated small craft with headphones clamped over the ears, no bathroom, and no easy way to make a quick stop if you need one, non pilot passengers hate it. And all it takes is one or two nights stuck in some podunk airport, or missed important dates, due to weather to convince them thoroughly that traveling by small plane is not for them. And despite all the fancy electronic bells and whistles this is still a very real possibility for aircraft without full de-ice and the capabilities to operate regularly at altitudes above 20,000 feet. These translate into an aircraft a order of magnitude outside the range of affordability, especially when you include maintenance and currency, for most of us mere mortals.

  13. Eugene says:

    Thank a chance for being me able to present at the discussion. As always, it is a mine of information to learn or to refresh. The especial enjoy is for me,Russian,you are speaking in colorful aviation language that does not get me sleep at the computer and add a great bit to my poor English. As for local SATS alike program,I don’t think , I’ll live that long in my 66 now.

  14. Pete Zaitcev says:

    Hours are gated purely by two things: money and desire. There’s a guy, well known at Pilots of America and PBP forums, David White, who’s put 227 hours at his 172 last year. He is 17 years old and is instrument rated. If he didn’t need to attend school and his pocket money were limitless enough to support a Cirrus, he’d be putting 400 hours a year on that airplane. As it is, his parents denied him permission to fly to Amelia Landing grand opening party due to bad weather.

  15. Bill Berson says:

    Dave Schwartz is exactly right about passenger travel by air. This applies to many pilots also. (including myself) It takes time to get over the fear and unkowns and most prefer to go by airline.

    Gordon-
    What about cogeneration with an additional steam turbine attached to the gas turbine to recover the waste heat? Or inject the steam onto the gas turbine itself for more power and blade cooling.
    I think modern gas turbine utilities are going with cogeneration.
    For aviation, the water condenser is the problem, I think.
    What about total water loss and forget condensation. Might work for short boost like an afterburner.
    I saw a video last week of a twin jet powered ultralight using two RC model jet turbines. Seemed to work with 104 lbs total thrust(52 each). Why don’t they make a small turbofan for models instead of just turbo-jets?

  16. Gordon Arnaut says:

    Believe it or not, there are people looking into steam power to drive a turbofan…

    Here is how it would work…the steam boiler and condenser would be mounted within the fuselage near the CG…the steam would be routed through high pressure lines to drive turbine wheels to which propulsion fans are attached on a common shaft…

    The advantage is you could place a number of fans in an advantageous location, such as at the aft end of a lifting body wing-fuselage where you could take advantage of boundary layer ingestion to increase propulsive efficiency…the steam lines could be routed anywhere like “power” lines…

    The key to making steam work is also heat exchanger (HX) technology…both the boiler and the condenser are heat exchangers…current technology is too big and heavy to be practical in an aircraft application…by a long shot…

    But similar HX technology to what is about to make recuperated aero turbines a reality could well make steam more doable…

    Steam (Rankine Cycle) is a very efficient turbine cycle…not a huge amount of water is needed because it would be in a closed loop and could be condensed in an HX that uses fuel as the cooling medium, thereby also heating up the fuel before combustion which is advantageous…

    Combined cycle is something else altogether… used in large power plants which means they use a gas turbine like the GE LM2500 (land version of the ubiquitous CF6 turbofan) to generate power and then use the “waste” heat from the exhaust to heat the steam in the boiler…so you need less fuel to get your steam…which in turn runs steam turbines to make more power…Total efficiency is now about 60 percent…

    But combined cycle in aircraft is a non-starter because of the weight and complexity…

    Cogeneration means you use the waste heat from a gas turbine for water or space heating…

    Microturbines claims up to 80 percent efficiency in this way, but we have no use for heat or hot water in an airplane…

    However the HX in a microturbine is used to increase core engine thermal efficiency to about 35 percent…and that is as good as a diesel engine…not bad for a turbocharger with a burner can and HX added…

    This is the future of aero turbines…but current HX technology is not going to cut it…that’s the whole key…

  17. Gordon Arnaut says:

    Just to add here that nuclear reactors generate electric power by heating steam and then turning turbines…

    With an energy density 500,000 times greater than oil fuels…just one pound of uranium could provide as much fuel energy as the A380 can carry which is over 500,000 lb of JetA…

    A few hundred pounds of U235, the weight of a couple of pax could keep the plane flying for a year without refueling…

    Think what that would do for performance, range, payload…

    Not likely to happen for political reasons of course…

  18. Bill Berson says:

    Your right, cogeneration is not the correct word for my scheme. But combined cycle might not be what I am talking about either, I think.
    Perhaps turbo-compounding is the word I want here.
    Like the large piston engines that used turbo-compounding to capture waste energy and put the turbine power back into the crankshaft.
    This is what I had in mind: a small gas turbine with its waste heat used to make steam and put the energy back into the same shaft using an additional steam turbine stage.

    In effect, the gas turbine is a steam generator for the steam turbine on the same shaft.
    Combined cycle, from what I see now on wikipedia, separates the steam turbine from the gas turbine on a different shaft.

  19. Gordon Arnaut says:

    Using waste heat to heat up steam is still combined cycle, only difference is you are putting the steam power back into the gas turbine shaft to drive a fan or prop or rotor…

    Simply using a recuperator accomplishes the same thing, but much more efficiently…again you are using the waste heat after it has passed through all turbine stages (driving the compressor, fan, etc…)…but that heat is transferred directly into the air exiting the compressor and going to the burner…

    The steam cycle would just be a middleman that would extract penalties due to less than 100 percent efficiencies of the steam turbine etc…not to mention all the weight…

  20. Gordon Arnaut says:

    Btw, recuperated gas turbines are used in ships…

    Rolls WR-21 is a good example…derived from aero engine and used on British destroyers…puts out 25 megawatts which is 33,500 hp, about the same as the GE LM2500 (marine version of CF6 turbofan)…

    Fuel consumption is only 190 grams/kWh, which is about 0.31 lb/hp-hr…our piston engines burn more than half again as much at about 0.5 lb/hp-hr…

  21. Bill Berson says:

    I seem to recall that Chrysler (or GM ) put a turbine with a recuperator in an experimental car decades ago. It was a rotary heat exchanger.

    • I’m not sure about the recuperator in the Chrysler and I’m not sure how many versions there were. As I understand it, the thing suffered from poor acceleration and poor fuel economy. If the latter is true it probably didn’t have a recuperator, or the technology was no were near as advanced as it is now. Then again, wasn’t the Chrysler engine a centrifugal, rather than axial? We worked on some experimental bearings for it in our shop because of a specific material they wanted to try as that would normally been way outside our realm. That was what, 40 years ago or so?

      I’m not sure that the LM2500 would be a good comparison as we are again comparing a system that does not scale well. IE over 33,000 HP to 150 or 200 HP or over 2 orders of magnitude difference.

      It seems I remember that high pressure/high temp steam is highly corrosive and would present a different set of problems as far as the blades are concerned.

    • Found this in Wiki: “The power turbine was connected, without a torque converter, through a gear reduction unit to an otherwise ordinary TorqueFlite automatic transmission. The flow of the combustion gases between the gas generator and free power turbine provided the same functionality as a torque converter but without using a conventional liquid medium. Twin rotating recuperators transferred exhaust heat to the inlet air, greatly improving fuel economy. Varying stator blades prevented excessive top end speeds, and provided engine braking on deceleration.”

      As to the actual engine evolution, “While Chrysler’s work with turbine engines never paid off in the retail automobile sector, the experiments proved fruitful with the incorporation of a Honeywell AGT1500 into a slightly different product, the M1 Abrams Main Battle Tank, developed in the late 1970′s by Chrysler Defense (which was later sold to General Dynamics).”

  22. Gordon Arnaut says:

    Roger, there is a good history here of the Chrysler turbine car…

    http://www.turbinecar.com/misc/History.pdf

    The later version worked quite well…the design used variable stator blades in the turbine to get the engine to spool up quickly…this is a characteristic of all turbine engines of course and it does not a problem with airplanes because we operate steady state for the most part…

    But when you transition to turbines you find that you can’t let the engine spool down on descent to landing…otherwise you will keep sinking if you have to go around…

    The variable nozzle greatly improve engine response because they decrease the nozzle area and thus keep the momentum of the flow high even when the mass flow is small…the Chrysler engineers were able to get response time down to about 1 second, from about 7 seconds in the first version…

    Yes the Chrysler engine used radial turbomachinery as do most small turbines…and the recuperator was a rotating wheel through which both hot and cold gases flowed…technically called a regenerator…this scheme can be compact but it has other problems like gas sealing etc…

    Axial turbomachinery is more efficient but not generally worth it in small engines as it is more complex and more costly…

    The Chrysler achieved very good fuel efficiency getting SFC of under 0.5, as good or better than piston engines of equal power…The Rover turbine used intercooling and higher temps and fancier metallurgy and they got down to about 0.4 SFC…

    Of course this is at sea level…as soon as you start climbing into colder temps turbine engines really get an efficiency boost, due to the fact that it takes less work to compress air when you start with colder temps…

    Even today’s simple cycle turboprops like the PT6 will be close to piston SFC at upwards of FL200…a recuperated engine would be downright awesome and would easily beat piston SFC…as the big turbofans do already…

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