Liquid Cooled Aircraft Engine

Piloto said:
Well boats have no radiator neither fan but plenty of ocean water to dissipate heat. But have other problems. Unless the engine has a heat exchanger salt water is going to corrode your engine very quickly. And you still need the water pump.

Jose
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Unless you are operating in fresh water (think Great Lakes) no boat of any quality operates with raw water cooling. Salt precipitates out in the water jackets around the cylinders, which develop hot spots, and soon the engine is in need of an overhaul. As we know in the aviation world, engines are too expensive to ruin like this. The fix is fresh water cooling: a heat exchanger as you suggest. The fresh water cools the engine, then the fresh water is cooled by salt water in the heat exchanger. This fix is well know, not very expensive, and reliable.

-Skip
 
Piloto said:
Just when you need max power on take-off and climb over mountain terrain with a fully loaded plane full of gas. Now you convinced me. Thanks for the tip.

Jose
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In 35 years of working on engines both liquid an air cooled I have yet to have a catastrophic cooling system failure that wasn't easily predictable many hours in advance from such simple things to detect as a slow leak from a shaft seal to a blister/bulge/softening of a hose LONG before rupture. The reality is, anything built to last anymore is water cooled, and it's that because it is more reliable, not less.
 
Loss of the cooling system also doesn't turn the engine off, lost the belt tensioner on a jeep wrangler once, still got 20 miles down the road at 60mph before temps started getting too high. And that too a decent amount of power as a lifted jeep takes a bit to fight the drag created by pushing a box thought the air at that speed.
 
Skip Miller said:
Unless you are operating in fresh water (think Great Lakes) no boat of any quality operates with raw water cooling.
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While true, let it be known there are a hell of a lot of crappy boats out there running around in salt water with raw water cooled engines.
 
Henning said:
Yes, but using water to collect the heat from the engine and taking it to a radiator made specifically for the transfer of heat rather than blowing air directly across the engine, the thermal exchange can be accomplished with considerably less drag due to increased efficiency.
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Henning is 100% correct. The radiator is a purpose built heat exchanger and it is super efficient at transferring heat.
 
Henning said:
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While true, let it be known there are a hell of a lot of crappy boats out there running around in salt water with raw water cooled engines.
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My 1974 atomic 4 was running well when I sold it. Salt water all its life. I had some issues with corrosion of other parts of the system (a water manifold, and thermostat housing) in 2010 but the block, head and water jackets were fine. Raw water pump lasted me 5 years.
 
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dell30rb said:
My 1974 atomic 4 was running well when I sold it. Salt water all its life. I had some issues with corrosion of other parts of the system (a water manifold, and thermostat housing) in 2010 but the block, head and water jackets were fine. Raw water pump lasted me 5 years.
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Me too, when I bought it in a 1972 Catalina 27 in 1986 it was raw water cooled as well, never have seen an Atomic 4 on a heat exchanger in real life though I have seen pictures of one lol. I did plugs, points, condenser on principle when I bought it and made a tube crank that I didn't even have to raise the ladder to use. That boat today is behind my buddy from that times current boat back in SD. I laughed when I saw it. Seems the boat is still running just fine on that same engine.

The difference though is mass to power really. It never provides enough heat to work the salt out lol. You're talking a heavy 4 cylinder iron flathead making 20 hp WOT and cooling with the same pump you find pushing the water through a heat exchanger for 260hp Chevy.
 
Henning said:
The difference though is mass to power really. It never provides enough heat to work the salt out lol. You're talking a heavy 4 cylinder iron flathead making 20 hp WOT and cooling with the same pump you find pushing the water through a heat exchanger for 260hp Chevy.
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Yup I always kept the thing at low temperature. IIRC about 130 degrees-140degrees. I installed a manual valve to control the water flow and removed the thermostat.
 
Henning said:
While true, let it be known there are a hell of a lot of crappy boats out there running around in salt water with raw water cooled engines.
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Yep. Most outboard engines do not have a heat exchanger. This is why you have to flush them with fresh water after you pull them out of the water. BTW all the airboats engines I have seen on the Everglades are air cooled. BTW does all those aircraft water cooled engines have freeze plugs. I hated when my old Chevy blew one.

Jose
 
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From Wikipedia:
A true freeze plug is an expansion plug located in the side of an engine block that is supposed to protect the block against freeze damage. Water expands when it turns to ice, and if the coolant does not have enough antifreeze protection it can freeze and crack the engine block. The freeze plugs (there are usually several) are supposed to pop out under such conditions to relieve the pressure on the block.

Like it was not enough to have a broken water pump or leak. Now you can have a cracked cylinder if there are no freeze plugs in the engine. BTW radiators also crack in cold weather and you will not know until you start the engine. So make sure you have the right mix of antifreeze. Too much antifreeze and it will not cool as well. To much water and it will crack or at least corrode your engine. Check with your local Pep Boys guys.

Jose
 
Piloto said:
From Wikipedia:
A true freeze plug is an expansion plug located in the side of an engine block that is supposed to protect the block against freeze damage. Water expands when it turns to ice, and if the coolant does not have enough antifreeze protection it can freeze and crack the engine block. The freeze plugs (there are usually several) are supposed to pop out under such conditions to relieve the pressure on the block.

Like it was not enough to have a broken water pump or leak. Now you can have a cracked cylinder if there are no freeze plugs in the engine. BTW radiators also crack in cold weather and you will not know until you start the engine. So make sure you have the right mix of antifreeze. Too much antifreeze and it will not cool as well. To much water and it will crack or at least corrode your engine. Check with your local Pep Boys guys.

Jose
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I call bull**** and Wikipedia isn't always right. "Freeze plugs" are plugs put in the round holes put in the casting for the purpose of allowing the cleanout of casting material from the block. If you do in fact freeze the coolant in your engine you will crack the block. Freeze plugs won't save it.
 
Sac Arrow said:
I call bull**** and Wikipedia isn't always right. "Freeze plugs" are plugs put in the round holes put in the casting for the purpose of allowing the cleanout of casting material from the block. If you do in fact freeze the coolant in your engine you will crack the block. Freeze plugs won't save it.
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Perhaps not always, but I have personally seen blocks freeze, pop the freeze plugs, and survive intact. Once you get it thawed you drive in new freeze plugs (common parts found at any auto parts store), clean up the mess, add some antifreeze and off you go.

Buddy of mine in high school bought a barely-subsonic '69 Javelin AMX. THe previous owner had run straight antifreeze. He was doing about 110 or so when one of the plugs spring a leak. It was pretty impressive, the amount of thick steam that thing would produce. He dropped me off at my place, we took the radiator cap off and filled the cooling system from the hose so he could limp the few miles home with the cooling system unpressurized.
 
Sac Arrow said:
I call bull**** and Wikipedia isn't always right. "Freeze plugs" are plugs put in the round holes put in the casting for the purpose of allowing the cleanout of casting material from the block. If you do in fact freeze the coolant in your engine you will crack the block. Freeze plugs won't save it.
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Ohh....sh%$#*&t. Thanks for the advice. One more reason to keep my air cooled IO-360.

Jose
 
Piloto said:
Yep. Most outboard engines do not have a heat exchanger. This is why you have to flush them with fresh water after you pull them out of the water. BTW all the airboats engines I have seen on the Everglades are air cooled. BTW does all those aircraft water cooled engines have freeze plugs. I hated when my old Chevy blew one.

Jose
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If you blew a freeze plug on a Chevy you either hard froze the engine in which case if all you replaced was the plug, it did its job admirably, or you had an engine well beyond TBO.

I can show you a fleet of air boats that run BB Chevys too. It doesn't matter.

The technology of the systems for water cooling is sufficiently mature such that it is not a significant reliability factor even with the blatantly negligent maintenance routines we subject our cars to. Under the maintenance and inspections regimes as we are used to in aviation there is well enough notice of impending failure at those points inclined to do so, even the factors remaining are greatly ameliorated in their hazard towards catastrophic failure.

The greatest benefit to water cooling is we get to decide what we want to do with an entire energy source. We can run it through a lower drag/higher efficiency heat exchanger system in a performance enhancing duct. We can tap some of that off in the cabin for heat and I can get that damned bomb heater out of my nose. We can also bond a hot water capillary system to the inside of the skins for de/anti ice systems.
 
Piloto said:
Ohh....sh%$#*&t. Thanks for the advice. One more reason to keep my air cooled IO-360.

Jose
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Dear god, you are like the little kid that just keeps running from what they think is a scary monster in the closet, when there is nothing there.

What kind of car do you drive with an air cooled engine, since you are so against a liquid cooled engine?
 
KSCessnaDriver said:
Dear god, you are like the little kid that just keeps running from what they think is a scary monster in the closet, when there is nothing there.

What kind of car do you drive with an air cooled engine, since you are so against a liquid cooled engine?
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Well, in my younger days I used to have an air cooled 1957 VW Bettle. Never had a freeze plug blown, neither a broken water pump or a leaky hose. I only replaced the clutch once. Mine had no fuel gauge but a reserve tank with enough gas just to make it to the next gas station. No A/C and no heat. Had a lot of fun with that car.

The Chevy Corvair engine was also air cooled but for me was underpower.

These days I have a Ford Explorer. But have to admit that the road environment is different from air. On the road you will survive an engine out failure but not necessarily in the air. So aircraft engine reliability is critical for your safety.

Jose
 
Didn't the Cessna 421 have liquid cooled engines?
 
BrianNC said:
Didn't the Cessna 421 have liquid cooled engines?
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No, I don't think they ever did a GTSIOL engine, RAM IIRC had a TSIOL 550 conversion for the 414 that went into a lot of them back then, hardly see any anymore.
 
Piloto said:
Well, in my younger days I used to have an air cooled 1957 VW Bettle. Never had a freeze plug blown, neither a broken water pump or a leaky hose.
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At the same time you poured a fair amount of fuel down the carburetor relative to the anemic performance provided.

I have changed a couple of water pumps over the years, never did they leave me stranded. Hoses are a time-limited item, just like oil hoses (and oil coolers) are on aircraft engines.
 
Personally, I am enjoying my Liquid Cooled Aircraft Engine... And the heater works great when it's -30 F outside...:)
 
Old thread but interesting topic. Water cooling would be a large improvement to our current powerplants. No one mentioned the main advantages of water cooling with regards to efficiency an power output: Compression and boost. You can run much higher compression and /or boost with water cooling which allows higher efficiency and power from the same cubic inches with minimal modifications.

As to the drag issue many mentioned, cooling drag is easily the highest single source of form drag on most GA aircraft. Reduction in form drag from cooling has a huge potential for lowering Cd and therefore increasing efficiency. Form drag from cooling is the low hanging fruit that gives the biggest gains to efficiency. As mentioned several times, a properly designed duct and radiator can actually be a source of thrust. In addition cowl flaps could be regulated much more easily and efficiently to meet cooling demand. If that's feasible or cost efficient on most GA aircraft is another question, but the advantages of water cooling ,when taken, together are large.

An example of a relatively simple drag reducing system: Radiators that exhaust out through a cowl in front of the windshield would do double duty as they would increase pressure in that low pressure, drag producing area and the duct and radiator supplying the cooling air could be much more efficiently designed as well. This is currently avoided because of the possibility of oil from the engine compartment or oil cooler getting on the windscreen in case of a leak, but a water based system, if leaking, would not significantly inhibit visibility would and alert the pilot to the leak at the same time.

As for reliability and safety of the system, There is no inherently unreliable system in properly maintained water cooling. It's tried and tested. It also enhances safety in some ways by reducing the possibility of cracked and separated jugs from shock cooling and reducing the chance of detonation leading to thermal runaway, melting pistons and catastrophic engine failure.

Tighter tolerances and their advantages were mentioned earlier.

Another advantage would be corrosion resistance. The higher thermal mass and insulating property of a cooling jacket would much reduce the possibility of condensation and thus, corrosion on steel cylinder walls.

Another bonus is that oil life would be extended as peak oil temps would be reduced possibly leading to longer oil change intervals.

All of this would have to be subject to testing and regulatory approvals though and that's the real stumbling block considering the small market served. It would be expensive up front, no doubt, but almost certainly pay for itself in efficiency, and longevity. A miracle large investment and wide adaptation could bring the up front cost down considerably. That's highly unlikely though.
 
Marcus said:
Water cooling would be a large improvement to our current powerplants
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It has been tried a few times but hasn't really seemed to catch on. It's just not that critical, and does add a lot of complexity, and this is coming from someone who welcomes advances in GA engines

The Extra 400 had a bad ass liquid cooled absolute monster of a Conti in it, a liquid cooled TSIOL-550-C

https://en.wikipedia.org/wiki/Extra_EA-400

The Extra 400 was really an absolute boss of a plane (200 KTAS typical 75% cruise at mid teens and 22 knots high flight levels, pressurized to 6,000.. 25,000 ceiling, 1,400 ft/min climb, 6 seats) but they built extremely few of them. I think the goofy looks, high price tag, somewhat obscure manufacturer, and namely the liquid cooled engine turned off many potential buyers. Plus it's a high wing, so that's an automatic fail in my book. BUT... if you had $1M to spend and were thinking between this and the Cirrus SR22T I think you'd have some serious pros and cons to each

 
The SMA aerodiesel currently being STCed by Soloy for the C182 is liquid cooled, as are many other aerodiesels (I believe!)

The first generation SMA engine cooling underperformed, but hopefully Soloy will fix it.
 
Tantalum said:
It has been tried a few times but hasn't really seemed to catch on.
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Yeah. It would take so much work to really take advantage of the benefits that it's probably never going to catch on as a replacement to existing powerplants. It's just a gearhead fantasy at this point.

Thanks for the link to that plane. Very interesting.

Katamarino,

I wonder if the diesels will fare any better in the long run. They are, at least, supported by the big players. Interesting developments.
 
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zaitcev said:
Rotax 912
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My favorites! This is true, but Rotax is paving the way in a whole different light. As far as something like "Cool Jugs" or Lycoming / Conti being able to do this mass scale I don't think we'll see it.. they've clearly abandoned all efforts at any kind of modernization since the 1950s

But yes, maybe in EA or with totally clean sheet designs that aren't just taking an already huge and heavy engine and adding more weight and components to it
 
Tantalum said:
As far as something like "Cool Jugs" or Lycoming / Conti being able to do this mass scale I don't think we'll see it.. they've clearly abandoned all efforts at any kind of modernization since the 1950s
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Yeah, well... Lyc made noises about FAA certification of DEL-120, but apparently nothing came out of it. It was 3 years since they mentioned it last time. Instead they just crank them out for drones (seen a video with Paul Bertorelli visiting the factory). The refuse to sell those engines on EX-AB market too. Conti is no better - only offer Titan, but none of the CD-135/155, CD-200, or CD-300. The price would probably be absurd for any of them anyway. {Update: I realize that CD-200 is air-cooled.}

https://www.lycoming.com/engines/del-120
 
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zaitcev said:
Yeah, well... Lyc made noises about FAA certification of DEL-120, but apparently nothing came out of it. It was 3 years since they mentioned it last time. Instead they just crank them out for drones (seen a video with Paul Bertorelli visiting the factory). The refuse to sell those engines on EX-AB market too. Conti is no better - only offer Titan, but none of the CD-135/155, CD-200, or CD-300. The price would probably be absurd for any of them anyway. {Update: I realize that CD-200 is air-cooled.}
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There is also, admittedly, not much reason for Lyco/Conti to really do much more than just crank out the same old engines. The only people buying piston engines in any meaningful volume are Piper, Cessna, and Cirrus.. and these planes have had the same powerplants for decades. So why would they go through the hassle of a total new clean sheet design. It's a catch-22 type situation really. Rotax gets to have a lot of wiggle room in the EA world and eventually mature a product, like what they did with the certified version that's on the Tecnam twins. For Lyco/Conti there's simply not much business case
 
In an aircraft engine, I don't think you really need complete liquid cooling. The Rotax 9xx series has liquid cooled heads, with air cooled cylinders. Harley-Davidson has done the same thing; it lets you control head temperatures better, so you can run higher compression, leaner mixture, and/or more spark advance for better performance and lower emissions. My 2007 model car uses the spark plugs themselves to sense pre-ignition and detonation to control mixture and timing. I can't think of any real reason those things could not be used in aircraft engines, other than regulation-induced inertia.
 
Tantalum said:
There is also, admittedly, not much reason for Lyco/Conti to really do much more than just crank out the same old engines. The only people buying piston engines in any meaningful volume are Piper, Cessna, and Cirrus.. and these planes have had the same powerplants for decades. So why would they go through the hassle of a total new clean sheet design. It's a catch-22 type situation really. Rotax gets to have a lot of wiggle room in the EA world and eventually mature a product, like what they did with the certified version that's on the Tecnam twins. For Lyco/Conti there's simply not much business case
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Just as a point of comparison, Lycoming DEL-120 is used in large, MALE-class drones, of which U.S. ordered 19 in 2017. So, let's say 30 engines in a couple of years, just to be generous. Meanwhile Rotax cranked out 50,000 912 engines over 25 years, which comes to about 2000 engines per year. This is about 2 orders of magnitude difference from new, clean sheet, liquid cooled designs by the American engine majors.
 
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