Are Liquid Cooled Aircraft Engines Possible?

Does anybody remember the nuclear industry saying that their generating stations would make electric power that was going to be too cheap to meter. (Free, with a service charge).

Does anybody remember that the Space Shuttle was to go into orbit every week like a space airliner?

Remember how the prop fan was going to be the next high-efficiency airline engine?

How about how the Wankel rotary was going to make pistons obsolete?

What about satellite relayed telephone calls. Wave of the future. Remember that annoying time delay?

My point is, technology doesn't always work the way we think it will. Inspite of 100 years of developement, liquid-cooled aircraft engines have yet to reach prime time.

You say, what about the P-51! Since they got shot down or crashed on a very regular basis, I'll bet nobody has any real idea of long-term reliability issues with these engines. They were also flown by young, intensively trained men wearing parachutes. When they failed, you would step over the side, and a new one was waiting for you when you got back to base. Merlins and Allisons also had 12 cylinders, so power pulses came much more often,
making power-train vibrations less of an issue. To my knowledge, no liquid cooled aircraft engine has ever been in US commercial service.

With the exception of the 100 hp Rotax 912, which employs a clutch and 2.43gearing, liquid-cooled, reduction-geared aircraft motors seem to be hard to perfect. They too have drive problems. Take a look at the reduction components and you decide it you would want to fly behind one. Looks like Swiss watch components.
http://www.rotax-aircraft-engines.com/pdf/dokus/d01856.pdf

I suppose only time will tell if the aircraft PSRU will go the way of the dirigible. Maybe in another 100 years we will have that flying car they have been promising us!

Liquid cooled aircraft engines are impossible. None have ever been built; let alone flown.

kcameron said:

Liquid cooled aircraft engines are impossible. None have ever been built; let alone flown.

Click to expand...

What? Did you not read the first post or hopefully you are kidding?

kcameron said:

Liquid cooled aircraft engines are impossible. None have ever been built; let alone flown.

Click to expand...

Actually one did fly. It came 300 feets into the air and self detonated in a huge explosion.

Check your history...many of the first aircraft engines were liquid cooled. They switched to air cooled because the Germans kept shooting holes in the radiators.

Water cooled engines are possible for airplanes IF.....

Sure liquid cooling is possible but is it efficient or the right thing to do:

1 - If the engine the right one
2 - If the the airframe is the right one
3 - If the heat exchanger'(s) is/are specifically designed & installed for the application (see item 1 & 2)


The issue is tractor engines on existing airframes are typically designed or optimized for air-cooled engines. Tractor airplanes like the RV have a big challenge fitting a heat exchanger in for good cooling & low drag. Yes it will fly but you either pay the price of drag and less efficiency or less speed. Since water cooled engines are not a quantum leap higher in efficiency, than the "radiators" are a drag, figuratively and literally. Fuel econ in cars comes from electronics that make a car's "mission" more efficient.

Pusher like a Cozy, LongEZE, Velocity have more room to duct & route radiator cooling air. Not saying it can't be done in a RV, just ad hoc installations are not ideal. Ross has the right idea with his RV-10. Make a super slick cowl with no inlets and move the radiator to the belly, aka P-51. Now to be fair the P-51 had bullets and cannons shot at it, which the RV-10 should not (unless he cuts me off in the pattern!).

The engine and airframe must match. Put the Pratt and Whitney R-2000-18W; 2,325 hp on the P-51 and the Packard/Merlin V-1650-7, 1,790 hp in the F4U Corsair, both airplanes would go from awesome to suck. The airframe needs to be made around the engine. Rutan's around the world Voyager had two engines, one of which was a liquid-cooled, a Teledyne Continental IOL-200. It was the aft engine and basically ran the whole time. The forward Teledyne Continental 0-240 was used as needed for 70 hours of the 9 day flight. This seems to be a good marriage of engine and airframe.

WITH SO MUCH AIR available to an aircraft engine, which never STOPS, air cooling makes a LOT OF SENSE. Plus there is less STUFF (to fail) and weight. There are no hoses, radiators, pumps or belts.

AIR + FIN's = HEAT EXCHANGER (with no liquid middle man).

The comments made about water cooling being "Modern" is funny, since the Wright Bros used a water cooled engine. Actually air-cooled is more advance in many ways and harder to do. The US War Dept and NACA spend Billions in today's money to develop and perfect air-cooled engines. The best of the best figured out a R2800 was pretty reliable and powerful. B-17's had their upper jugs blown off by gun or cannon fire, but the engine kept running, while the connecting rod flopped around all the way back to base.

Water cooling use for cars is two fold: One emission's, you can run tighter tolerances; Two noise, air cooled engines have more mechanical noise from valves clacking and so on. Frankly I'm an air-cooled Porsche 911 fan. I love the mechanical clanging. Porsche went to water cooled in 1999 for the reasons above, but its not a better car. In fact the air-cooled 911's are more popular and have higher resale. The new 911 is just another lounge lizard car to me now.

Air-cooled is a little bit of a misnomer. What people don't realize is both "air-cooled" Lyc and Porsche 911 are liquid cooled. They use oil for cooling. The Porsche as 16 qts of oils and two huge coolers under the front bumper. Same with a Lyc. If you have CHT issues and OT issues at the same time, you might need a better/bigger oil cooler or installation or both. If you are running "liquid around" like OIL why not use it to cool as well as lubricate. Air around the head of the Lyc is critical but only part of what carries the heat aways from the exhaust valves.

When it comes to ultimate capacity and better temp control, liquid cooling has it over air-cooling. You want your engine to get warm, the thermostat cuts liquid off, simple and very effective. A water cooled car engine can idle on the ground all day in traffic (well most cars) and drive all winter, while giving you heat for your feet. Not sure a Lyc can do that or you would want it to. A Lyc would suck as a car engine. Frankly if the temps are not high enough in a Lyc's combustion chamber, you don't activate lead scavenging compounds in the fuel, which can fowl the plugs. If oil temps are not hot enough, combustion byproducts and mosture does not burn off, staying in the oil and engine. Liquid cooling is king in temp control, which is important in a car. A plane operates in a limited envelope, WOT at 75% pwr most of the time.


Air-cooled aircraft engines, normally aspirated, are pretty tolerant of temp, but we all know CHT's and/or OT must be watched during climbs on HOT days. It's not near "thermal limits", but during extreme conditions you may have to watch and adjust your climb rate. In cold temps Lycs are over cooled, there's not a lot we can do, close cowl flap (if you have it), cover the oil cooler with a plate. Too cold can cause subtle problems. Turbo-charging can start to strain air-cooled aircraft engines "thermal capacity", necessitating bigger oil coolers, cowl flaps and more operational limits. It's not a big problem operationally but its a factor. It's not soccer Mom, mini-van simple, turn the key and drive with out a care in your head. On the other hand when car engines go into a plane, it no longer is turn key simple operational wise either. Many Wankel's and Subies have temp issues in-flight and need to be watched.

So what, you have to watch CHT and OT sometimes in the summer with a Lyc.

Experimental water cooled planes tend to uses little heat exchangers where they can fit, so temp is an issue, even with the water cooling. For some reason the translation from CAR to PLANE does not cross-over. You can afford a "big-Ol-radiator" on a wheeled vehicle, which travels at 65 mph but not at 200 mph; Does not mean it can't work on a plane, just that it takes things like variable air geometry (aka P-51). The design of engine, airframe, installation and mission need to match. What works on a P-51 (+400 mph) may not work on a 190 mph RV. There's some scale factor there.

I have faith that RV alternative guys will improve their water cooled bred. But it will take a nexus of right engine, right airframe and right heat exchangers. Other wise liquid cooling will just be DIFFERENT not BETTER.

I should make a clarification. Maybe a reliable PSRU will prove technologically impossible, thus rendering the liquid-cooled aircraft engine undesireable. Not all engineering problems have cost-effective solutions.

Interesting question. Technically, water only transfers heat to heat exchangers- water/oil radiators are still air cooled.

Air cooling is efficient because the delta t is so high between ambient air and hot metal surfaces, but, that also assumes cylinder heads and valves stay hot, hopefully below temps where lubricants break down and detonation breaks parts.

Water cooling allows better control of localized hot spots (pistons/cylinder heads) and therefore, closer tolerances and better durability. Water cooling is probably better suited to high power/low drag applications, like the P-51 and most of the later WWII piston driven fighters.

Yukon said:

To my knowledge, no liquid cooled aircraft engine has ever been in US commercial service.

Click to expand...

Curtis Jenny. Probably others, there were a lot of OX-5 engines sold to start up aircraft manufactures after the big war. Lincoln Paige comes to mind.

Current production aircraft--------at least recently produced, not sure if still in production--------Extra 400.

http://www.extraaircraft.com/ea400.asp

Here is a link to the newest version, with a kerosene burner on the nose.

http://www.extraaircraft.com/ea500.asp

Thielert Diesel

The aforementioned diesel is liquid cooled, and in commercial service in Diamond and Cessna aircraft. The reliability is not reputed to be very good yet. I imagine that if they stick around for a few decades it will improve.

Frankly, it's a miracle that any new aircraft engines are being designed. Thielert's was not a scratch design for aircraft, afaik, but an adaptation of a Mercedes design. Honda made a pretty prototype and then decided it was a waste of time.

I can easily imagine an engine similar to a Subaru but with a integral psru in an aviation specific design. Coupled to purpose designed radiators, in a purpose designed airframe, it would do quite well indeed. I just can't imagine any company bothering to do it, given the projected ROI.

Regarding PSRUs, if Tracy Crook can design a reliable one, with resources likely in the low 6 figures, I'd bet the farm that a multi billion dollar firm like Honda (Subaru, etc...) could design one in their sleep. And twice on Sunday.

Thunder Mustang

After an RV, that I may actually be able to afford. I always liked the thunder mustang for that ultimate toy fighter, since I know I can't afford the real deal. I think scaling the wing sub 3/4 scale for max speed was a mistake and even should have been 80% scale. I see there are several kits for sale firewall back. Is there a problem with the Falconer liquid cooled V12? Several builders have been switching to a walter turbine instead of the Falconer. I know several of the racers were working on supercharging the engine with limited success. A few years back there was a company trying to sell a liquid cooled V8 conversion as a cheaper replacement for turbine engines. I think it was called Ondaira. Then there is the current crop of diesel engines that are mostly water cooled.

Jenny was a military trainer. There were a number of water-cooled military aircraft, but none in commercial service.

I think it is very telling that after WW2, no commercial aircraft manufacturer elected to power their aircraft with liquid-cooled engines. If this technology was superior, you would think that Boeing and Douglas would rush to it's use.

Yukon said:

Jenny was a military trainer. There were a number of water-cooled military aircraft, but none in commercial service.

Click to expand...

You dont think hundereds of barnstormers flying arround the country selling rides for $5 wasnt commercial???

Also, the Jenny was used for mail delivery.

Yukon said:

I think it is very telling that after WW2, no commercial aircraft manufacturer elected to power their aircraft with liquid-cooled engines. If this technology was superior, you would think that Boeing and Douglas would rush to it's use.

Click to expand...

Never said it was superior, just that there were L/C powered planes used.

As a matter of fact, I tend to agree, that with the current state of things, the air cooled engine is superior for most of the currently available airframes, and flight missions.

From a technology only standpoint, I believe that the L/C engine is vastly superior to the air cooled. More heat rejection allows more HP/CuIn, less wear, closer tolerances, and a host of other benefits.

That said, IMHO, what is standing in the way of a commercially viable L/C engine for certified aviation use, is development cost, and monatery return on investment.

Luckily, we have the homebuilt world to play in.

The Rotax 912 is produced in higher numbers than any other aircraft engine, and it IS watercooled. When looking at the facts, the numbers, watercooled engines clearly are the winners.

When looking at 4 stroke aircraft piston engines produced in the last 20 years, I would guess 80-90% are 912, and every single one of them are water cooled.

I think what is happening is that it takes so much recources to develop an aircraft engine, and the market (GA) is so limited, that the company that is lucky and comes out with something that works well enough to be accepted, will be able to (or be forced to) stick to that design for decades.

I'll bet, right this very minute, that someone is flying behind a Thielert diesel. When the poor SOB lands, he's going to have to pay the FBO and / or the CFI. Seems like a commercial enterprise to me.

Yukon said:

You say, what about the P-51! Since they got shot down or crashed on a very regular basis, I'll bet nobody has any real idea of long-term reliability issues with these engines. They were also flown by young, intensively trained men wearing parachutes. When they failed, you would step over the side, and a new one was waiting for you when you got back to base. Merlins and Allisons also had 12 cylinders, so power pulses came much more often,
making power-train vibrations less of an issue. To my knowledge, no liquid cooled aircraft engine has ever been in US commercial service.

Click to expand...

My good friend Tom Watkins, who at age 21 flew 51's with the 52nd Fighter Group out of Italy, told me his airplane had 400 hours of combat time when maintenance insisted on a mandatory engine change. He protested, even had his CO fly the machine to confirm its smooth operation but to no avail of course - rules is rules.

The point being, your question has no merit. Like it or not, there have been successful liquid cooled aircraft engines. After all, it was an all liquid cooled operation that got Adm. Yamamoto, the Japanese officer responsible for the Pearle Harbor attack. Without those liquid cooled P-38's the war might have gone on for years.

David-aviator said:

My good friend Tom Watkins, who at age 21 flew 51's with the 52nd Fighter Group out of Italy, told me his airplane had 400 hours of combat time when maintenance insisted on a mandatory engine change. He protested, even had his CO fly the machine to confirm its smooth operation but to no avail of course - rules is rules.

The point being, your question has no merit. Like it or not, there have been successful liquid cooled aircraft engines. After all, it was an all liquid cooled operation that got Adm. Yamamoto, the Japanese officer responsible for the Pearle Harbor attack. Without those liquid cooled P-38's the war might have gone on for years.

Click to expand...

There's a good data point, Dave. 400 hr mandatory removal time. Anyone else out there got any Merlin reliability info? They could easily have been suffering from the same torsional vibration issues we see today.

The P-38 was a heck of an airplane, and from what I read the Allisions were more reliable than the Merlins.

Actually, he has a point!

kcameron said:

Liquid cooled aircraft engines are impossible. None have ever been built; let alone flown.

Click to expand...

OK, there has never been a truly liquid cooled aircraft engine. Stay with me here... Because the liquid is only a means to transfer the heat to the air. So, a "liquid cooled" aircraft engine is, in fact, air cooled. Same thing applies to the "oil cooled" argument. The only truly liquid cooled internal combustion engine that I can think of is in a boat. Take the water from the ocean or lake, transfer the heat, and return it to the source a little warmer. The plumbing would be a problem in an airplane.

John Clark
RV8 N18U "Sunshine"
KSBA

liquid vs air cooled

If I recall, during the 1930's and 1940's when aircraft development was racing ahead and the various branches of the armed force was driving much of it, the Navy was favoring aircooled engines (or the companies that designed them), and the airforce favored aircooled. I always wondered why. It may have been that Navy and Air Force planes were designed by different companies and therefore used different technologies for competetive or business reasons. Or maybe it's just that the engineers there had different opinions as to which was best. If so, this thread proves that nothing has changed. I think that the environment in which they were to be used was a factor. Navy planes operate in relatively moderate climates and Airforce, operates in deserts to northern climates. In other words, more extreme and varied climates. Bottom line is, there were very successful aircraft represented by both the liquid and air cooled camps BUT as George said (and as I say has been the norm throughout aviation), the aircraft is designed around a particular engine, not the other way around. The demand has always been for bigger more powerful engines so that the airplane can do more, but the airframe must wait for the engine.

Bevan
RV7A wiring
air/oil/spit cooled IO-360

I researched and posted this a few months back on VAF:

This is a follow up to the discussion a couple weeks ago on the liquid cooled vs. air cooled - small vs. big after a bit of research.

I got in touch with several people who flew or worked on the R3350 in both military and civil service and was lucky enough to talk to a pilot/ engineer who still flies the Martin Mars water bombers up here.

OK TBO of 3500 hours in civil service. Well depends what you mean by TBO. The R3350 started out in 1944 with about a 30 hour lifespan in the severe duty on the B29 hauling heavy bomb loads to Japan. This was very hard on them at high power settings and in high blower for hours. Steady improvements were made post war to these engines. It appears as though Wright set the TBO at 2000 hours initially in the early '50s and increased this to 3500 hours in the early '60s when they started a SOAP program. My sources said few if any R3350s remained on wing for this period as the oil analysis showed problems well before this time and many jugs were replaced along the way. The jugs were often damaged by the sodium cooled exhaust valves disintegrating. All the people I contacted said that when operated in high blower, engine life plummeted by about 50%.

The US Forest Service sets the TBO on their R3350s in the Neptune at 1600 hours today and say they routinely make it there with no jugs replaced. Locked in low blower and limited to 51 inches dry.

The Martin Mars water bombers have their TBOs set at 800 hours. They are not turbo compound models. Steve Wall said only 2 engines ever made it that far with no jugs replaced. They have a problem with master rod thrust bushings disintegrating. The overhaul costs on these engines is over $200,000! Again this is a hard life with heavy loads but they limit manifold pressure and high blower is locked out.

In military service on the ASW mission and C-121 intelligence gathering at low altitude, the lifespan was pretty good due to low power settings and most of the time in low blower.

In civil use on the Super Connie, experiences seem at both ends of the spectrum and maybe time has made some forget the facts a bit. One quote stuck out: "... I don't remember ever having a flight of more than six hours that I landed with all four running. With the TC engines, the Connie became known as the Worlds Fastest Tri-motor".

The following link should provide a few chuckles. This is from a line mechanic with Quantas on the Connie: http://www.lockheed.adastron.com/constellation/da3.htm

Airline use was a hard life in high blower most of the time. The man hours per flight hour going into a four engined airplane were staggering and why the jet was such a leap forward despite the very high fuel consumption.

My piece of personal trivia on these engines involves living on an RCAF base in the '60s and having a four engined Argus take off over the house with full wet power-3700hp X 4. What a noise. The ground shook!

Now the 1650 cubic inch Merlin in airline service in the same era- Canadair Northstar (4 engines). Used by TCA, CPA and BOAC. Again life started out grim. TCA had 20 in flight shutdowns in one month! With takeoff power set at 1660hp at a staggering 71 inches. Cruise power was initially set at 40 inches and 1100hp. Engine life on wing was 200-450 hours in most cases. With a lowering of cruise power to 950hp, life picked up considerably. Over a one year period and 957 ocean crossings, 2 engines made it past 2000 hours, 7 made it to 1750 and the average life on wing was 654 hours (no jug changes on the Merlin). TBO was set at 1250 hours although this was just as meaningless as with the Wrights.

Initial problems were with the intercooler pump seals, compressor surging, coolant leaks and erroneous fire warning lights. Rolls Royce offered TCA a "won't be sorry" warranty on their Merlins- 6000 hours or 3 years. They would pick up the tab on any unreasonable wear or failures. RR probably lost money on this one! The Merlins on the North Stars were in a power egg which had rads and almost all parts attached in one piece for quick removal and replacement. Good idea. They needed it. It appears that very few Merlins had catastrophic failures- indeed, one was held at full takeoff power for 5 hours in a flight test until the oil supply ran low- pretty tough. Coolant leaks caused most of the shutdowns.

The RAF and SAAF also used the Rolls Royce Griffin in the Avro Shackleton ASW patrol aircraft. I was not able to contact anyone with experience on these 4 engined aircraft but they were in use many years over the oceans.

Research showed that the Pratt R-2800 was the engine to have in this era. Better reliability and fuel consumption than either the Merlin or the Wright. The Pratt 4360 was horrible by all accounts I found. In any case, the jet quickly replaced them all.

Well a lot has changed in 50 years. Subarus appear to hold their coolant more reliably than Merlins and don't require much maintenance. If they need work, they need to come out of the airframe like the Merlin. The Sube is about half the size of the Lycoming just like the Merlin was half the size of the radials.

The O-320/360 Lycoming could be compared to the R-2800 perhaps and generally reaches its TBO with few problems. Major work like jug replacements can be done while still mounted in the airframe. Where the radials used barrels of oil (literally) and the Merlin was topped up with 2 quart tins, the Lyco uses the occasional quart and the Sube nothing between changes.

Some similarities here. Hope you found this interesting. Remember that something over 350,000 liquid cooled engines (all with reduction gears) were produced by the combatants in WW2 alone. Must have worked ok or they would have switched.


__________________

Great post, Ross. You are now in George's league for detailed posts.

Did you by chance gather any info on gearbox reliability? The radials all have planetary gearboxes, and I know they are very sensitive to being backdriven by the prop. The R-2800 was definitely the "sweet spot" in radial developement.

It's the Merlin and Allison spur gear reliability that interests me. Any info?

The Merlin appeared to have very good reliability from its reduction gear. The early Allison used epicyclic gearing which proved unreliable as power crept up over 1200hp. A later gear design solved this and I could find few reports of gearbox failures.

In operational use, the Allison suffered from inadequate intercooling initially using surface conduction types in the P38. This contributed to detonation at high altitude and piston failures. Also contributing was the lower octane fuel available initially in the ETO. Many changes in the intercooler and radiator setups were made to the P38 airframe during the war years. They finally got it right with the J model in 1944 and reliability on all fronts as well as sustained power above 25,000 feet was excellent.

I've read a lot of books on WW2 and engines in particular and other than the early weakness in the Allison gearbox there are almost no references to gearbox troubles. Almost all liquid cooled engines used straight cut spur gearing. This includes the DB601-603 engines and the RR Merlin- about 160,000 of each of these were produced. V12s are more friendly when it comes to torsional vibration due to the close power pulses.

Most aero engines went through considerable development during the war. The liquid cooled ones about doubled in hp in 5 years while sustaining initial levels of reliability. Much of this was due to supercharger development, higher octane fuels, intercooling improvements, and technologies such as water/methanol and nitrous oxide injection. Cubic displacement remained unchanged during this period on the 3 most popular V12s.

Here is a concise link on the DB600 engines used by many German aircraft during WW2. It had direct injection (now back in use today) and a clever, variable drive single stage supercharger. http://www.aviation-history.com/engines/db605.htm

Is an uncooled engine possible?

Something I've been wondering about lately is whether it might be possible with the right materials (perhaps not yet invented) to make a piston engine that requires no cooling. I have no engineering knowledge whatsoever (obviously) but figure that perhaps the internals could be made of something that doesn't so readily soak up heat. Maybe?

szicree said:

Something I've been wondering about lately is whether it might be possible with the right materials (perhaps not yet invented) to make a piston engine that requires no cooling...

Click to expand...

Others have wondered about that. One of the better known names is the late Smokey Yunick http://en.wikipedia.org/wiki/Smokey_Yunick
who was reputed to be working on engines with ceramic parts that would not need additional cooling.

john kelley said:

After an RV, that I may actually be able to afford. I always liked the thunder mustang for that ultimate toy fighter, since I know I can't afford the real deal. I think scaling the wing sub 3/4 scale for max speed was a mistake and even should have been 80% scale. I see there are several kits for sale firewall back. Is there a problem with the Falconer liquid cooled V12? Several builders have been switching to a walter turbine instead of the Falconer. I know several of the racers were working on supercharging the engine with limited success. A few years back there was a company trying to sell a liquid cooled V8 conversion as a cheaper replacement for turbine engines. I think it was called Ondaira. Then there is the current crop of diesel engines that are mostly water cooled.

Click to expand...

The Thunder Mustang is a very cool plane. It is blasphemy to put a turbine is this airframe. Surely the sound of the V12 is as important as the airplane! The supercharged Falconer V12 has been shown to be very powerful and the basic engine reliable. A small problem with the belt slipping cost it the win in Sport Class at Reno in 2006 after setting the qualifying record and fastest lap that year.

Orenda developed the very expensive V8 and that project was sold to a company in Texas who says it will rise from the ashes again. http://www.traceengines.com/

BTW Titan aircraft announced that they are planning to offer a full size P51 replica kit to be powered by a Chevrolet LS7 conversion.

Just hope they get someone like EPI or the fellow who designed the drive for the Falconer V12 ( he worked on the RR Merlin gearbox!) to do their drive.

szicree said:

Something I've been wondering about lately is whether it might be possible with the right materials (perhaps not yet invented) to make a piston engine that requires no cooling. I have no engineering knowledge whatsoever (obviously) but figure that perhaps the internals could be made of something that doesn't so readily soak up heat. Maybe?

Click to expand...

Or can absorb heat without melting down. This is what makes modern turbine engines so reliable and efficient.

Such metal technology may have been looked at with internal combustion engines and probably does make sense in terms of efficiency. At the cost it would make more sense to go straight turbine, why have all those moving parts?

rv6ejguy said:

Orenda developed the very expensive V8 and that project was sold to a company in Texas who says it will rise from the ashes again. http://www.traceengines.com/

Click to expand...

And they appear to be headed in the right direction. They are located just a couple miles from my house, and I've seen several advertisements for open positions in the local paper, and there are many vehicles parked at their building everyday. It certainly does not appear as if they are steady-state or even declining.

I don't have anything to add to this discussion at this point, but I do want to commend everyone for the civility of this thread thru three pages. Great job, and a very interesting topic! Keep it up, and these threads can be very informative, and FUN to follow!

That's good news on the Orenda V8 Greg. The price is the killer I think though and the PT6 replacement idea might make sense- or not. I'd love to hear this engine flying in something. I recommend they install in a Sport Class entry at Reno and show it's stuff. That might attract some interest.

Chad, quit fooling around. Are you installing an air or liquid cooled engine in your RV? Nice flap system there BTW.

szicree said:

Something I've been wondering about lately is whether it might be possible with the right materials (perhaps not yet invented) to make a piston engine that requires no cooling. I have no engineering knowledge whatsoever (obviously) but figure that perhaps the internals could be made of something that doesn't so readily soak up heat. Maybe?

Click to expand...

In a diesel that could be almost possible by increasing the compression to insane numbers. In fact, high efficiency in modern diesel engines in cars cause some peculiar problems already today. The heat in the cabin is made by the a radiator using warm cooling water from the engine. A modern diesel has so high efficiency that there is not enough waste heat from the engine to even warm up the cabin in the winter. VW have for several years now used additional electric heating for their larger saloons and vans/buses, and I guess others are doing this also now. This means larger battery, larger alternator, added complexity of electric heating elements, so high efficiency is not always only a good thing. The cooling needed for a modern diesel is very little on other words. A lot of heat goes out with the exhaust also.

In an otto engine with a restricted compression ratio the thermodynamic efficiency will never be better than 40-50% or something (don't remember the exact numbers), so about 50% will be lost in heat energy no matter what you do.


Have to correct some numbers I presented. Did a search on the internet, and there are "only" produced 15,000 units of Rotax 912, but most of them during the last 10 years. Of other noteworthy liquid cooled engines:
DB 601: 20,000 units
DB 605: 42,000 units
Junker-Jumo 211: 70,000 units
Allison V-1710: more than 70,000 units
RR Merlin: 100-200k ? Packard alone built more than 60,000 units.

SvingenB said:

Actually one did fly. It came 300 feets into the air and self detonated in a huge explosion.

Click to expand...

I'll try and remember that when I fire up the Rotax 912S today

TODR

Aaaand...

David-aviator said:

Or can absorb heat without melting down. This is what makes modern turbine engines so reliable and efficient.

Click to expand...

.......is also what makes a PT-6 680 SHP engine cost near $300,000 The exhaust gives around 110 lbs. of thrust on my Air Tractor but the voluminous airflow through the engine is what keeps it cool.......if you consider ITT (Inter-turbine-temp) of 620-650 C cool. It moves so much air, that we use two huge Peterbilt diesel engine intake filters to allow the flow.

The compressor turbine is bathed in fire all day long, glowing, and the joke is that it's made of unobtainium at $15,000 for just the single disc, 8" in diameter, spinning up to 37,500!

I don't think that most "Experimenters" even want to think in terms of those dollars. Then again, I've watched Lancairs screaming by with the Walters at Sun 'n Fun.

Regards,

Ain't no problem here that money can't solve....

Speed is measured in horsepower, and horsepower is measured in cubic dollars. How fast you wanna go?

SvingenB said:

Have to correct some numbers I presented. Did a search on the internet, and there are "only" produced 15,000 units of Rotax 912, but most of them during the last 10 years. Of other noteworthy liquid cooled engines:
DB 601: 20,000 units
DB 605: 42,000 units
Junker-Jumo 211: 70,000 units
Allison V-1710: more than 70,000 units
RR Merlin: 100-200k ? Packard alone built more than 60,000 units.

Click to expand...

Over 33,000 ME 109s were produced, 7000 HE111 and 15,000 ME110s these alone would require 80,000 DB600 engines plus spares, plus license built versions by the Italians and Japanese. The DO17 and Me 210 also were powered by these. Given the hard wartime use and short service life, lots of spares were required. There is little doubt that well over 120,000 DB 601 engines were produced, second only possibly to the Merlin with 160,000 units.

I'd love to hear this engine flying in something.

Click to expand...

Go here http://www.mrrpm.com/ and click on "see and hear the 1200 Hp...."

It is a short video of a 685 Twin Commander with 2 geared, watercooled V8s.
Near the end of the video is a short clip of the first plane with a water cooled engine.

rv6ejguy said:

Over 33,000 ME 109s were produced, 7000 HE111 and 15,000 ME110s these alone would require 80,000 DB600 engines plus spares, plus license built versions by the Italians and Japanese. The DO17 and Me 210 also were powered by these. Given the hard wartime use and short service life, lots of spares were required. There is little doubt that well over 120,000 DB 601 engines were produced, second only possibly to the Merlin with 160,000 units.

Click to expand...

Yes indeed Ross. All war time use, all short service life, (most) all technology
abandoned after the war in favor of air cooling and turbines.

Yukon said:

Yes indeed Ross. All war time use, all short service life, (most) all technology
abandoned after the war in favor of air cooling and turbines.

Click to expand...

John, in time of war technology prevails. In peace time the bean counters take over. Your question still is without merit.

Memories, warm and fuzzy.

N395V said:

Go here http://www.mrrpm.com/ and click on "see and hear the 1200 Hp...."

It is a short video of a 685 Twin Commander with 2 geared, watercooled V8s.
Near the end of the video is a short clip of the first plane with a water cooled engine.

Click to expand...

Web site has not been updated in 6 or 7 years. Circa 2000: "Cheaper to buy, use less fuel and they sound great."

Too bad the program was canceled or died. Doha!

Sorry could not resist. Pretty cool. Too bad they could not finish what they started. I know weight was a real issue.

Wikipidia:
"Unfortunately the events of 9/11 required Orenda to re-focus entirely on their military projects (or so they claimed), and the OE600 project was canceled. The design was later purchased by a group of investors who intend to sell the engine under the Texas Recip brand, but it is unclear if this project is continuing. On August 29, 2006 the president of Texas Recip, Paul Thorpe was sentenced to 3 years and five months for defrauding investors."......."However, financial difficulties led to the project being abandoned after a reported investment of some $5 to $10 million."

I suppose with 600hp/500hp continuous they where going for the turbine replacement market? Most of the Garrett's where making 800hp but the early ones first out in 1967 where rated at 605HP. The last Turbine Commanders had about 940hp.

As for the piston Aero Commanders, how much would overhauling two Lyc 540's cost verses the conversion? How many old Commanders are there. Most of the piston Commanders where made from 1960 to the 70's, so they're older airframes, probably not worth massive investment.

FLUSH...NEXT!....Next, new, better, greater, super duper engine...Aero Commanders many piston engines. Early ones had GSO&IGSO-480's. The latter ones had TIO540's and some GSIO540's (geared and supercharged). They even made a few with 435hp Continental GTSIO-520K. Imagine, turbo+supercharged and geared! Ouch.

Mr. RPM's plane N60QR is a 1974 Aero Commander 685 redesignated as 685A, which originally had the 435HP Continental GTSIO-520K.

All I can say after firing up my engine last night for the first time with a prop on it is: water cooled engines rock! Mine is quieter and has a lot less vibrations than a Lyco! I could actually talk to a person without screaming with the doors open! Yes these are just baby steps before the first flight but quiet is nice but silence might be deadly!

Yukon said:

I think it is very telling that after WW2, no commercial aircraft manufacturer elected to power their aircraft with liquid-cooled engines. If this technology was superior, you would think that Boeing and Douglas would rush to it's use.

Click to expand...

Not so. There is whole bunch of the world outside the US borders. The Canadair North Star was a post WWII commercial airliner powered by RR Merlins.

gmcjetpilot said:

They even made a few with 435hp Continental GTSIO-520K. Imagine, turbo+supercharged and geared! Ouch.

Click to expand...

Wouldn't the be "turbo-supercharged", as opposed to "turbo-normalized"? Meaning the turbo is being used to produce power above sea level rated power for the same engine, naturally aspirated, not that it was dual charged?

I was hoping someone read my big post (page 2) earlier about Merlins in use on passenger aircraft. Evidently not.

The Orenda concept of high speed at altitude was sound. Turbines lose a large portion of power at altitude. The turbo piston engine does not until it reaches critical altitude hence a 600hp turbo (500 hp MCP) easily beats a 650hp turbine unless the turbine is flat rated from a much higher power core. They were targeting -20/-28 PT6s that were rated at 550SHP.

Other than the TU95 (60,000 shp), the fastest operational propeller driven aircraft have been piston powered and supercharged or turbocharged. The turbine stuff will do the speeds all day though I admit.

Their test aircraft was 40-50 knots faster than the turbine version if I remember at altitude and handily out climbed it as well. The installation was something like 400 pounds heavier but this was offset by being able to carry 400 pounds less fuel for the same mission. Con was that TBO would probably never match a PT6. Pro, no hot sections. Pro, cost was high but nowhere near that of a PT6.

If the reliability and longevity was there (unproven), it could work. Trouble is, most people with the $$ to buy a King Air probably can afford the turbines and wants them too. Saving 100-200 lbs. hr. probably is not too important when the airplane is $2-5M.

Still love to see it flying in something.

TSwezey said:

All I can say after firing up my engine last night for the first time with a prop on it is: water cooled engines rock! Mine is quieter and has a lot less vibrations than a Lyco! I could actually talk to a person without screaming with the doors open! Yes these are just baby steps before the first flight but quiet is nice but silence might be deadly!

Click to expand...

Right on Todd, big step.

Yukon said:

Jenny was a military trainer. There were a number of water-cooled military aircraft, but none in commercial service.

Click to expand...

Both the Douglas C-1 and the DeHavilland DH4 were used in commmercial service. Both of which were powered by the water cooled Liberty V12 engine.

Yea?

1:1 Scale said:

Wouldn't the be "turbo-supercharged", as opposed to "turbo-normalized"? Meaning the turbo is being used to produce power above sea level rated power for the same engine, naturally aspirated, not that it was dual charged?

Click to expand...

You got me. I was just going off the nomenclature, from mr lycoming: GTSIO =

G - Geared
T - Turbocharged
S - Supercharged
I - Fuel Injected
O - Opposed Cylinders

I flew (or flew in) an Aero Commander 500S a few times. Most of the piston models where normally aspirated. It was not till the 680 models did they get into turbo or supercharged (or both) piston engines.

If you never seen this, this is Bob Hoover putting a 500S through its paces: http://www.youtube.com/watch?v=9ZBcapxGHjE

(There's a bunch of vids on YouTube of the Rockwell Commander doing their thing and earning a living)

rv6ejguy said:

I was hoping someone read my big post (page 2) earlier about Merlins in use on passenger aircraft. Evidently not. ( I read it Ross and it was fantastic!)

Their test aircraft was 40-50 knots faster than the turbine version if I remember at altitude and handily out climbed it as well. The installation was something like 400 pounds heavier but this was offset by being able to carry 400 pounds less fuel for the same mission. Con was that TBO would probably never match a PT6. Pro, no hot sections. Pro, cost was high but nowhere near that of a PT6.

If the reliability and longevity was there (unproven), it could work. Trouble is, most people with the $$ to buy a King Air probably can afford the turbines and wants them too. Saving 100-200 lbs. hr. probably is not too important when the airplane is $2-5M.

Still love to see it flying in something.

Click to expand...

Me to, I'd like to see them. I have some doubts about performance specs, but I guess we'll never really know? 40-50 kts faster than what model? May be verses the piston models. Seems a little exaggerated, but if it really did 271kt Cruise, it would be 20 kts faster than the Econ cruise speed of early Turbine 680's (600-700 shp Garrett's) and 10 kts faster than later models with larger Garrett's. The later models also had 308 kt top speed, 35,000 service ceiling and 1,400 nm range (carried more gas no doubt), so they're not slow. Even the piston version, like the 685's would cruise @ 222 kt (242kt max), with econ range of 1,200 nm with reserves at FL200.

Orenda too good to be true? May be not. I think you're right about rich people and saving a few nickles on gas. Also TBO of 1,500 verses 10,000 hours was a negative to operators. Just like RV'ers have turbine envy, rich probably want to have a "prop jet".

rv6ejguy said:

I was hoping someone read my big post (page 2) earlier about Merlins in use on passenger aircraft. Evidently not.

Click to expand...

I just read it now, and it was very interesting. Thanks for the info.

I have to ration the amount of time I spend reading forum posts - otherwise I wouldn't get any work done.

Kevin Horton said:

I just read it now, and it was very interesting. Thanks for the info.

I have to ration the amount of time I spend reading forum posts - otherwise I wouldn't get any work done.

Click to expand...

Kevin, I was hoping John maybe read that part. I'm waiting for parts from Van's and JE right now so I have a bit more time to spend on the forums right now but I know what you mean- work on the plane or sit in front of the PC...

It has finally warmed up here so I'm taking the -6A up today to get some rust out.

Thanks for posting the Wiki link Kevin. Many of our American friends would be unfamiliar with this aircraft. As a footnote, my dad who was in the RCAF (Vampire, T33, F86 etc.) was a passenger on a North Star that made a forced landing up north. No major injuries.

Ross,

I read your post and congratulated you on it's depth. Is there something in particular you want to discusss?

Just the part about the Merlins in passenger use.

Well Ross, my post said " none in US commercial use" so I am not sure what your point is. I don't know what a Canadair airliner looks like, so I can't really speak to foreign applications.

As far as the Orinda goes, replacing a turbine with a V-8 would be like replacing a refrigerator with an icebox. You could do it, but why would you?
I can't believe anybody with any technical savy would fund such a business plan.