# Radial vs liquid cooled engines



## NiceShotAustin (Aug 19, 2012)

Was any engine better suited for combat during WW2 than the other? I know radials offered greater durability, but did they offer any other advantages? And did liquid cooled engines have any inherent advantages over radials?


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## Shortround6 (Aug 19, 2012)

Define durability? 

They may have been more resistant to combat damage due to no cooling system but as far as engine life goes ( hours before/between suggested overhaul) those were all over the place for both types depending on particular engine model, country, type of service ( fighter, bomber, transport), conditions of service ( grass field in England, North African sand, Russian steppe dust, Pacific coral rock dust) and how hard the engine was "pushed". WEP settings or water injection/MW-50. 

Liquid cooled engines had less drag for a good part of the war. V-12s can have a gun firing through the prop hub. Liquid cooled engines (again, depending on engine) could usually tolerate more boost.


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## davebender (Aug 19, 2012)

Liquid cooled engines tend to have fewer cooling problems once you get past about 1,000 hp.


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## CobberKane (Aug 19, 2012)

Radial engines have the following advantages:
1.	Because a radial engine cannot be deprived of its coolant (air) it is much more resistant to battle damage than an LC engine, which can be put out of action by a single hit to any part of the liquid cooling system.
2.	Because all cylinders of a radial engine are exposed to similar air flow the engine tends to maintain a universal operating temperature. In contrast the different cylinders of an inline or V liquid-cooled engine receive less progressively less benefit as the coolant moves through the block and heats up.
3.	An radial engine can be installed and removed much more easily than an LC engine as it is not hooked up to a separate cooling system. It is also easier to service as the cylinder heads are simple to access and the radial is effectively restricted to push-rod activated two-valve heads (this last is a disadvantage also – see below – but it does make the service intervals longer )
The liquid cooled engine has the following advantages:
1.	An LC engine does not need to expose all cylinders to the airflow, which greatly reduces drag compared to a radial. 
2.	Water is a much denser medium than air and will therefore remove much more heat from an engine for a given volume. This means that a liquid cooling system can be made to control engine heat at operating levels where an air cooled engine would not be able to cope. 
3.	Because the inline or V configurations enabled by liquid cooling have cylinders aligned in banks, a single camshaft and chain can be used to actuate valves in multiple cylinder heads. This opens up the option of multi-valve heads, increasing the efficiency with which the cylinder imports fuel mix and exports exhaust gasses, leading in turn to fuel savings and/or increased power. As the radial’s cylinder heads are isolated from each other, the same kind system for a radial engine would require separate cam chains and camshafts for each individual cylinder head, a scarily complex proposition.


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## wuzak (Aug 19, 2012)

There are some generalisations in that.

Not all air cooled engines were radials. And not all radials were air cooled. Granted, the major production radials were all air cooled and only a few liquid cooled radial prototypes were made.



CobberKane said:


> Radial engines have the following advantages:
> 1.	Because a radial engine cannot be deprived of its coolant (air) it is much more resistant to battle damage than an LC engine, which can be put out of action by a single hit to any part of the liquid cooling system.



Radial engines are also far more likely to have lose things like cylinder heads. They are also larger targets. Air can be deprived from the cooling system on an air cooled engine.




CobberKane said:


> Radial engines have the following advantages:
> 2.	Because all cylinders of a radial engine are exposed to similar air flow the engine tends to maintain a universal operating temperature. In contrast the different cylinders of an inline or V liquid-cooled engine receive less progressively less benefit as the coolant moves through the block and heats up.



I wouldn't say that is necessarily the case. Rear cylinders in multi-row radials have a harder time, for instance.

As for liquid cooled engines, it depends where the coolant enters and exits, and the coolant path. They were not all the same.




CobberKane said:


> Radial engines have the following advantages:
> 3.	An radial engine can be installed and removed much more easily than an LC engine as it is not hooked up to a separate cooling system. It is also easier to service as the cylinder heads are simple to access and the radial is effectively restricted to push-rod activated two-valve heads (this last is a disadvantage also – see below – but it does make the service intervals longer )



That is a sweeping generalisation. Liquid cooled engines with annular radiators could be changed in the same amount of time as the equivalent air cooled QEC. But you're right, it can take a lot of time to disconnect two hoses, particularly if they have quick disconnect fittings.

Ai rcooled engines were not restricted to 2 OHV. Some Bristol radials had pushrod operated OHV, before they went sleeve valve. The Armstrong Whitworth Deerhound had 3 or 4v per cylinder (can't recall) operated by single overhead camshafts.




CobberKane said:


> The liquid cooled engine has the following advantages:
> 1.	An LC engine does not need to expose all cylinders to the airflow, which greatly reduces drag compared to a radial.



Assuming we are talking V-12s, the LC engine has much less frontal area, which partially explains drag.




CobberKane said:


> Radial engines have the following advantages:
> 2.	Water is a much denser medium than air and will therefore remove much more heat from an engine for a given volume. This means that a liquid cooling system can be made to control engine heat at operating levels where an air cooled engine would not be able to cope.



It also allows tighter fits in piston/bore, reducing tthe amount of oil burned in the engine. Liquid cooling allows better cooling control, IMO.




CobberKane said:


> 3.	Because the inline or V configurations enabled by liquid cooling have cylinders aligned in banks, a single camshaft and chain can be used to actuate valves in multiple cylinder heads. This opens up the option of multi-valve heads, increasing the efficiency with which the cylinder imports fuel mix and exports exhaust gasses, leading in turn to fuel savings and/or increased power. As the radial’s cylinder heads are isolated from each other, the same kind system for a radial engine would require separate cam chains and camshafts for each individual cylinder head, a scarily complex proposition.



No chains involved in (most) aero engines. Most V-12s used geared shaft drive to the cams. Far mor reliable than belts.

As mentioned before, the AS Deerhound had overhead cams driven by geared shafts. So to the Lycoming XR-7755.

Fuel/air mix distribution to cylinders was a problem for both V-12 and radial engines during WW2, and had more to do with the intake side of things rather than the number of valves.

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## Jenisch (Aug 19, 2012)

How was the resistance of annular radiators to battle damage?


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## wuzak (Aug 19, 2012)

Jenisch said:


> How was the resistance of annular radiators to battle damage?


 
Probably no more or less than any other radiator.


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## CobberKane (Aug 19, 2012)

wuzak said:


> There are some generalisations in that.
> 
> Not all air cooled engines were radials. And not all radials were air cooled. Granted, the major production radials were all air cooled and only a few liquid cooled radial prototypes were made.
> 
> ...


 
Hi Wuzak,
I think we are at risk of repeating our discussion in the fighter bomber thread, though we seem to be finding a bit more common ground. 
I’m sorry but no, you can’t deprive an air-cooled engine of air. Either the flaps were open when hit, in which case they might get locked open, or they were closed when hit, in which case the plane was flying with them closed and will continue to do so with them locked closed. In contrast, once a liquid cooled engine lost its coolant there was ZERO cooling and the thing would seize up in short order. I’ve heard of plenty of LC aircraft overheating and going down after being hit in the radiator but I can’t recall any where an air-cooled plane seized up due to damaged cowl flaps. And how likely is the cowl mechanism of an air-cooled motor to be hit compared to a liquid cooling system that encompassed the entire top end of the motor and had a radiator hanging out in the breeze?
Re the cylinder heads of a radial more exposed to being shot off, radial engine fighters can and did sustain such damage and keep on operating. The same damage to a LC engine would result in rapid loss of coolant and inevitable engine failure
How was my observation that radial engines are easy to remove a ‘sweeping generalisation’? You mentioned LC engines with annular radiators as being just as easy to install and uninstall but how many combat aircraft were thus equipped? The Ju88 and Fw190D/Ta152 sure, but the vast majority of LC engine aircraft have had radiators attached to the airframe
Regarding multi valve heads on radial engines I said the radials were EFECTIVELY limited to two valves per cylinder, as were all the widely used radials of WWII I can think of. I didn’t say it was impossible to make a multi valve radial, it was just complex and impractical. How many Armstrong Deerhounds were produced? Ten, I think. And the Lycoming had a production run of two, both of which were extremely unreliable. 
To put it into perspective, a V-12 A Rolls Royce Merlin had two drive shafts driving two cams, one for each bank of six cylinders. A twelve cylinder radial with bevel-drive cam-actuated valves would require twelve drive shafts operating twelve cams – six times as many moving parts as the Merlin for the for the same result. Did any wartime production radial manage this?
Finally, if the number of valves in a head was of little relevance to the breathing of the engine, why did designers bother with multivalve heads at all? Why do they now?


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## wuzak (Aug 19, 2012)

CobberKane said:


> I’m sorry but no, you can’t deprive an air-cooled engine of air. Either the flaps were open when hit, in which case they might get locked open, or they were closed when hit, in which case the plane was flying with them closed and will continue to do so with them locked closed.



No, you can't deprive an air cooled engine of air. You could deprive it of the required mass flow of air. It isn't just the cowl flaps - the cowl at teh entry could be damaged and thus deprive the engine of air.




CobberKane said:


> In contrast, once a liquid cooled engine lost its coolant there was ZERO cooling and the thing would seize up in short order. I’ve heard of plenty of LC aircraft overheating and going down after being hit in the radiator but I can’t recall any where an air-cooled plane seized up due to damaged cowl flaps.



B-29s certainly had issues overheating at takeoff when the cowl flaps were closed.




CobberKane said:


> Re the cylinder heads of a radial more exposed to being shot off, radial engine fighters can and did sustain such damage and keep on operating. The same damage to a LC engine would result in rapid loss of coolant and inevitable engine failure



You provided one example of an air cooled engine losing a cylinder/head and surviving, and I provided one example of a liquid cooled engine that got its pilot home after being shot up.

I still would say that a radial with a cylinder/head missing is unlikely to make it back to base.




CobberKane said:


> How was my observation that radial engines are easy to remove a ‘sweeping generalisation’? You mentioned LC engines with annular radiators as being just as easy to install and uninstall but how many combat aircraft were thus equipped? The Ju88 and Fw190D/Ta152 sure, but the vast majority of LC engine aircraft have had radiators attached to the airframe



What about radials with turbos? How much easier was it to remove an R-2800 from a P-47 than a Merlin from a Spitfire? I mean, disconnecting two water hoses must have been a real chore (4 if it was a 2 stage with intercooler).




CobberKane said:


> Regarding multi valve heads on radial engines I said the radials were EFECTIVELY limited to two valves per cylinder, as were all the widely used radials of WWII I can think of. I didn’t say it was impossible to make a multi valve radial, it was just complex and impractical. How many Armstrong Deerhounds were produced? Ten, I think. And the Lycoming had a production run of two, both of which were extremely unreliable.



Only a handful of Deerhounds, and they had their problems too. Interestingly, Armstrong Whitworth had wanted to make the Deerhound as a liquid cooled engine, but the Air Ministry wanted an air-cooled competitor for Bristol.

Plenty of 4v Pegasus and Mercuries were built before and during the war.




CobberKane said:


> To put it into perspective, a V-12 A Rolls Royce Merlin had two drive shafts driving two cams, one for each bank of six cylinders. A twelve cylinder radial with driven bevel drive cam actuated valves would require twelve drive shafts operating twelve cams – six times as many moving parts as theforo the for the same result. Did any wartime production radial manage this?



The Deerhound had 21 cylinders, yet only 7 camshafts and associated drives. The Wolfhound was to have 28 cylinders, and yets still only 7 camshafts and associated drives. The (liquid cooled) Wright R-2160 Tornado had 42 cylinders and 7 camshafts and associated drives.




CobberKane said:


> Finally, if the number of valves in a head was of little relevance to the breathing of the engine, why did designers bother with multivalve heads at all?



That isn't what I said. I said, or was trying to say, that more issues lay with the distribution of the air/fuel mix into the cylinders - for both radials and in-lines.

There are advantages to 4 valves over 2 valves, other than breathing - such as being lighter and not requiring as heavy a spring to control it.


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## CobberKane (Aug 20, 2012)

wuzak said:


> No, you can't deprive an air cooled engine of air. You could deprive it of the required mass flow of air. It isn't just the cowl flaps - the cowl at teh entry could be damaged and thus deprive the engine of air.
> 
> 
> 
> ...



I refuse to surrender!
1.	Shooting up the cowl of an air cooled plane seems more likely to increase airflow, rather than decrease it. Lots of holes in anything tend to let stuff in, not keep it out. Sorry, I just can’t see how a hail of machine gun fire is going to seal up the cowling over a motor.
2.	If the only extra issue in removing a liquid cooled engine undoing a couple of pipes, I’ve been buying the wrong cars. Or maybe I should give up on routinely flushing radiators, replacing hoses, hooking the whole thing up again and mixing and replacing the coolant. Never worked on a turbo – don’t they come out with the engine in one piece?
3.	The relevance B-29s with closed flaps overheating on take-off to the idea that gunfire could close the flaps on an air-cooled aircraft and thus cripple it in combat is pretty tenuous
4.	I provided an example of an aircooled aircraft that flew across the Channel with a cylinder missing. You provided an example of a liquid cooled aircraft that got ‘shot up’ and made it back to base. Was its cooling system punctured? Did it make it back across the Channel? 
5.	True, Bristol did produce a heap of multi-valve radials during the war. They were used to power such brutes as the Fairey Swordfish and Gloster Gladiator. The top end of the performance envelope belonged to multi valve Liquid cooled designs and two valve air-cooled radials
6.	“The Deerhound had 21 cylinders, yet only 7 camshafts and associated drives. The Wolfhound was to have 28 cylinders, and yet still only 7 camshafts and associated drives. The (liquid cooled) Wright R-2160 Tornado had 42 cylinders and 7 camshafts and associated drives” - Yep, and neither of them got past the prototype stage…
7.	Yes, there are advantages to multi-valve engines over two valve engines aside from breathing – but better breathing means more power and power was at the top of the list for a combat aero-engine


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## wuzak (Aug 20, 2012)

CobberKane said:


> 2.	If the only extra issue in removing a liquid cooled engine undoing a couple of pipes, I’ve been buying the wrong cars. Or maybe I should give up on routinely flushing radiators, replacing hoses, hooking the whole thing up again and mixing and replacing the coolant. Never worked on a turbo – don’t they come out with the engine in one piece?



Not the turbos of WW2. The P-47 turbo, for instance, was in the rear fuselage. 

There were a few Daimler Benz prototypes with turbos that would be removed with the engine.




CobberKane said:


> 3.	The relevance B-29s with closed flaps overheating on take-off to the idea that gunfire could close the flaps on an air-cooled aircraft and thus cripple it in combat is pretty tenuous



It does show that cooling can be quite borderline on air-cooled engines.




CobberKane said:


> 4.	I provided an example of an aircooled aircraft that flew across the Channel with a cylinder missing. You provided an example of a liquid cooled aircraft that got ‘shot up’ and made it back to base. Was its cooling system punctured? Did it make it back across the Channel?



Well, no, because it was in North Africa.




CobberKane said:


> 5.	True, Bristol did produce a heap of multi-valve radials during the war. They were used to power such brutes as the Fairey Swordfish and Gloster Gladiator. The top end of the performance envelope belonged to multi valve Liquid cooled designs and two valve air-cooled radials



Bristol would have made big 4 valve radials had they not moved into sleeve valves. Persues, Hercules and Centaurus would likely have been 4 valve engines had Fedden not persued sleeve valves.





CobberKane said:


> 6.	“The Deerhound had 21 cylinders, yet only 7 camshafts and associated drives. The Wolfhound was to have 28 cylinders, and yet still only 7 camshafts and associated drives. The (liquid cooled) Wright R-2160 Tornado had 42 cylinders and 7 camshafts and associated drives” - Yep, and neither of them got past the prototype stage…



Yes, that is correct. Just pointing outthat you need not use a camshaft for each cylinder.




CobberKane said:


> 7.	Yes, there are advantages to multi-valve engines over two valve engines aside from breathing – but better breathing means more power and power was at the top of the list for a combat aero-engine



All true.


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## wuzak (Aug 20, 2012)

Just remembered another couple of examples of LC QEC modules - one production, one pprototype.

Rolls-Royce developed a Merlin QEC for the Beaufighter. This was used to convert the Manchester into the Lancaster. 

GM's Fisher Body Division developed a QEC for the V-3420 to be used as a replacement for the R-3350 if needed. The QEC contained all coolers and the (experimental) turbo. This was tested in the XB-19 and then used in the XB-39 (without the turbo).


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## CobberKane (Aug 20, 2012)

On the whole I maintain the relative advantages and disadvantages of the air-cooled v liquid cooled engines stand up; resistence to battle damage, and ease of amintenance for the air cooled radial against lower drag and the easier application of multi-valve heads for the V or inline liquid cooled motor. Its interesting that at the comencement of WWII the opinion of most designers of land based fighters was heaviy in favour of the liquid cooled engine, but subsequent experience demonstrated that the death of the air cooled radial had been greatly exaggerated. The radial remained a popular choice for carrier based aircraft, thanks to doubt to its ease of amaintenance and durability, and the arrival of the hugely influentual Fw190 in Europe demonstrated that a carefully installed radial could still trump the liquid-cooled fighters. Some excellent aircfaft also came about when airframes originally intended to house liquid cooled V-s had radials boilted on to see what would happen. The Japanese Ki-100 was derived from the Ki 61 in this way, as was the Lavochkin La-5 from the underwhelming La-3. Even the great Sydney Cramm was equivocal about mating the Hawker Tempest to the Bristol Centaurus, but that version his fighter was clearly superior to its Napier-Sabre equiped predecessor.
As to which was 'better', the air-cooled radial or inline/V liquid cool engine, utimately the arrival of the jet and turbo-prop removed any chance of the question being answered definitively. They both seem to be going well in civilian use today, and only now there is one more option - the Wankel Rotary. Wonder what they might have done with that during WWII?


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## Shortround6 (Aug 20, 2012)

During the History of the piston engine the air cooled and liquid cooled "sides" traded top honors several times. A lot of it had to do with drag. While the early installations of both engines were high drag, the liquid cooled engine's lower frontal area and ease of cowling was balanced somewhat by the rather inefficient radiators of the day. Also the early liquid (meaning water) systems tended to be leaky even without combat damage. AS the air-cooled engines (meaning radials, high powered air cooled v-12s or H 16/24 cylinder engines were a minority and had a few problems) got better installation, like Townsend rings and early NACA cowlings the liquid cooled camp countered by going to Glycol and/or pressure cooling with higher boiling points which allowed for smaller/lighter radiators. the P-36 with it's aircooled engine had 22% more drag than an early P-40 did. But as has been noted above the air-cooled engine installations got better, if a bit more finicky, until there was little to chose between a liquid cooled installation and an air-cooled one. Since, however, the balance changed during the course of WW II one statement cannot cover the entire war.


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## renrich (Aug 20, 2012)

During the Fighter Conference in 1944, there were pilots from Britain, manufacturers, AAF and USN. THere was a poll taken of the preferred engine for combat. The R2800 won handily over the Merlin, the only two engines that got many votes. Lindberg chose a radial, air cooled engine for the Altlantic trip because it was lighter and more reliable.


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## Grampa (Aug 20, 2012)

if we can simply put it, it whould be radial give strengt, inline give speed in comparelse.


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## davebender (Aug 20, 2012)

Not necessarily true. Me-109s had a radiator in each wing. They could be individually isolated in case of battle damage. As long as one wing remains undamaged you can limp home.

Annular radiators are another way to mitigate damage to liquid cooling systems. Hitting an annular radiator means hitting the prop and/or engine. Even without a radiator leak such damage is likely to seize the engine.


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## Shortround6 (Aug 20, 2012)

davebender said:


> Not necessarily true. Me-109s had a radiator in each wing. They could be individually isolated in case of battle damage. As long as one wing remains undamaged you can limp home.



"They could be individually isolated in case of battle damage"

The *COULD* be but usually were not, only certain models had the isolation valves and not even all of some of those models. Ground crews went to some lengths to salvage the valves from crashed/wrecked aircraft to fit to those aircraft that were not built with them.


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## wuzak (Aug 21, 2012)

CobberKane said:


> On the whole I maintain the relative advantages and disadvantages of the air-cooled v liquid cooled engines stand up; resistence to battle damage, and ease of amintenance for the air cooled radial against lower drag and the easier application of multi-valve heads for the V or inline liquid cooled motor. Its interesting that at the comencement of WWII the opinion of most designers of land based fighters was heaviy in favour of the liquid cooled engine, but subsequent experience demonstrated that the death of the air cooled radial had been greatly exaggerated. The radial remained a popular choice for carrier based aircraft, thanks to doubt to its ease of amaintenance and durability, and the arrival of the hugely influentual Fw190 in Europe demonstrated that a carefully installed radial could still trump the liquid-cooled fighters. Some excellent aircfaft also came about when airframes originally intended to house liquid cooled V-s had radials boilted on to see what would happen. The Japanese Ki-100 was derived from the Ki 61 in this way, as was the Lavochkin La-5 from the underwhelming La-3. Even the great Sydney Cramm was equivocal about mating the Hawker Tempest to the Bristol Centaurus, but that version his fighter was clearly superior to its Napier-Sabre equiped predecessor.
> As to which was 'better', the air-cooled radial or inline/V liquid cool engine, utimately the arrival of the jet and turbo-prop removed any chance of the question being answered definitively. They both seem to be going well in civilian use today, and only now there is one more option - the Wankel Rotary. Wonder what they might have done with that during WWII?



I agree that the liquid cooled engine has another system to maintain and be susceptible to battle damage, so it is more vulnerable to battle damage. I, however, believe that the difference in vulnerability is overexaggerated. It is done in two ways - exaggerating the vulnerability of liquid cooled engines to battle damage ("just one shot from a small calibre gun will do the trick"), and exaggerating the ability of air cooled engines to survive battle damage (using one or two examples of a particular engine having survived after a cylinder was shot off).

Ease of mainetnance is a more difficult sell - because in both categories some are easier to maintain than others.

Also, in what way was the Tempest II superior to the Tempest V?


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## renrich (Aug 21, 2012)

My suspicion is that most members of this forum are not old enough to remember when cooling problems were a major cause of breakdowns in cars with liquid cooled engines, which was most of the cars back in the late forties and early fifties when I started driving. That may be the reason that most don't seem to think that liquid cooled aero engines in WW2 were more problematic than air cooled ones. I can't relate how many times in various cars I have had to stop with steam coming out from under the hood and search for water to put in the radiator. It was mostly because the cooling system had a small leak because the car or truck was elderly( three or four years old) not because a bullet had gone through the radiator or a hose. 

Further, we have debated often that the oil coolers in the Corsair made it more or less more vulnerable, especially to ground fire, than the Hellcat. When you look at the size and location of those oil coolers, compared to the cooling systems of the various liquid cooled engines and some say the Corsair was practically a death trap and on the other hand say liquid cooled engines are no more vulnerable than air cooled ones, I am nonplussed and amused.


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## tyrodtom (Aug 21, 2012)

I didn't start driving till the early 60's, but in some mighty old cars. Most of the problems I had could be blamed on two things, high wear and poor maintenance, not something most aircraft would encounter.

But comparing the mass produced liguid cooled cars of the day with the liguid cooled aircraft of the same time is no different than making the same comparision today with modern cars and modern aircraft, there just is no comparision..


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## renrich (Aug 21, 2012)

Cars during WW2 and afterward were powered mostly by liquid cooled reciprocating engines just like many of the AC of that time. Today most AC are powered by gas turbine engines except for general aviation types which are largely powered by air cooled reciprocating engines. There was a very valid comparison between car engines and AC engines in the 30s and 40s. Packard car engines were mass produced just like Packard RR engines and they were both liquid cooled. A great many of the AC engines used for US AC in WW2 were produced by car companies.


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## tyrodtom (Aug 21, 2012)

Aircraft in 1940's were a quatum leap ahead in technology of the technology in MOST 1940's mass producted cars, just as they are today.
And Packard of the 30's and early 40's was not your usual American car manufactor.

I'm not saying automotive manufactors of the 40's weren't capable keeping precision tolerances, and advanced engineering when it came to producing engines, they were. What they could do, and what they put off the assembly line when it came to cars was just not the best they could do.


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## tyrodtom (Aug 21, 2012)

Let's take for example the flathead Ford V8, built from 1932-53, in various displacements. Like most V8's it's valves were on the inside of the V, and since for economy Ford cast the block in one piece, the exhaust passages from the valves in the block went between the cylinders to the outside of the block to the exhaust manifold. It was noted for it's tendency to overheat from the first to the last, even dual waterpumps couldn't cool it enough. 
Did it have cooling problems because it was a liquid cooled engine ?
No, it had cooling problems because the hot exhaust gasses went from one side of the block to the other, before exiting, transfering a lot of heat to the coolant.
That was state of the art at Ford for a liquid cooled engine in the 30's, but no aircraft manufacture would try such a dumb engineering.


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## FLYBOYJ (Aug 21, 2012)

tyrodtom said:


> That was state of the art at Ford for a liquid cooled engine in the 30's, but no aircraft manufacture would try such a dumb engineering.



Not that simple - many times aircraft manufacturers (engine manufacturers) are restricted to design guidelines either set by the military or civilian aviation authorities. You're actually looking at "dumbing down" a design for either safety or design standardization. In the 30s and 40s it was less restrictive for obvious reasons than it is today, but it did exist.


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## davparlr (Aug 21, 2012)

wuzak said:


> Also, in what way was the Tempest II superior to the Tempest V?


 
Other than being faster and climbing better?


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## CobberKane (Aug 21, 2012)

wuzak said:


> I agree that the liquid cooled engine has another system to maintain and be susceptible to battle damage, so it is more vulnerable to battle damage. I, however, believe that the difference in vulnerability is overexaggerated. It is done in two ways - exaggerating the vulnerability of liquid cooled engines to battle damage ("just one shot from a small calibre gun will do the trick"), and exaggerating the ability of air cooled engines to survive battle damage (using one or two examples of a particular engine having survived after a cylinder was shot off).
> 
> Ease of mainetnance is a more difficult sell - because in both categories some are easier to maintain than others.
> 
> Also, in what way was the Tempest II superior to the Tempest V?


 
It was more restant to battle damage lol.

Seriously, I just back handed a library book on the Hawker Typhoon and Tempest (titled, with dazzling originality 'Hawker Typhoon and Tempest') which went into the developement of the Tempest II in some detail and there was an overall performance and relaibility increase, which I suppose is why the Tempest V was supplanted. I didn't take a note of the figures, sorry.


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## wuzak (Aug 21, 2012)

davparlr said:


> Other than being faster and climbing better?


 
It did climb a little better, still nowhere neear as quickly as a Spitfire, but it was barely faster than the Tempest V, if at all.


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## Jabberwocky (Aug 21, 2012)

wuzak said:


> It did climb a little better, still nowhere neear as quickly as a Spitfire, but it was barely faster than the Tempest V, if at all.


 
RAF didn't seem to think so.

From the Tempest II vs Tempest V tactical trials 



> Speeds
> 
> 45. The Tempest II is 15 m.p.h. faster up to 20,000 ft., dropping to 10 m.p.h. from 4,000 – 7,000 ft., it then increases its advantage to 20 m.p.h. at 12,000 ft., dropping again to 10 m.p.h. at 15,000 ft. and holding this advantage up to its ceiling.
> 
> ...


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## Shortround6 (Aug 21, 2012)

Aircraft were also more subject to vibration than most cars. Aircraft were built as light as possible as were their engines. Some engines were notorious for vibrations, legend has it that you could tell what engines a DC-3 pilot flew ( Cyclones or Twin Wasps) by how long it took his hands to stop shaking after a flight. A huge number of aviation museums have Curtiss Challenger radial piston engines on display, again legend has it that the owners pulled the engines well before they wore out to put in other engines so they would have something, _ANYTHING,_that vibrated less ( it was a two row 6 cylinder radial, never tried again for a production engine). Some of the liquid cooled engines were no better. 
It took a while for engineers to fit loops and bends into fuel, oil and coolant lines just for stress relieve and to provide cushioning for the vibration.
Some early 6, 8 and 12 cylinder engines had *NO COUNTERWEIGHTS* on the crankshaft, and some later ones only had enough weight to keep the vibrations/forces within certain limits up to a certain RPM.

Fatigue cracking was only beginning to be understood at the end of WW I and in the early 20s. They called it "crystallization", they knew it was happening, older parts failing and having a different grain structure than new parts, but they didn't know how or why. 
Radiators were also predominantly soldered, _by hand._ Between human failures ( hundreds of solder joints in a single radiator) corrosion, vibration and dozens if not hundreds of heating cooling cycles the liquid cooling system was one more thing to go wrong. 
The liquid cooled engine was pretty much dead in the commercial market in the 1930s. Jumo Diesels and post war use of the Merlin not withstanding. The extra performance wasn't worth the extra cost of maintenance for a commercial aircraft. For military planes it was another story, at least for another decade or so.


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## CobberKane (Aug 21, 2012)

It seems to me that a good analogy for the air-cooled v liquid cooled aero-engine might be the development of off road motorcycles. Trail bikes, like combat aircraft, are inclined to get used hard and knocked around a bit, and even with the temptation of the extra power that can be wrung from an LC engine air cooled designs persisted quite a bit longer on trail bikes than road bikes. Today trail bikes seem to be mostly liquid cooled, no doubt as the manufacturers chase extra power at a given capacity, but anyone who does serious bush-bashing on a liquid cooled traily will be aware of the effects of a branch through a radiator or coolant hose. The same nasty stick would have been poking holes in thin air if the bike had been air-cooled


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## 61fury (Aug 21, 2012)

A question here, civilian airliners before the Jet Age all seemed to be radials. Was there a reason for this? Were there any liquid cooled airliners? I know fighting and flying and just flying are different goals but the radial engine era seemed to last until jets took over.


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## buffnut453 (Aug 21, 2012)

The reason for in-line engines becoming popular in the mid/late 1930s was to provide a smaller frontal area hence less drag and more speed. Those design drivers continued through the early war years (1939-1940) by which time radial engines started to produce sufficient power to compete against in-line engines in the overall performance stakes. However, by that time development of the jet engine was indicating that the future of high speed effectively sounding the death-knell for piston engines in high-speed implementations.

Radial engines survived in the civilian market because the drivers for those aircraft were long endurance, heavy load-carrying and (consequently) lower speeds. Given wing thickness and generally less aerodynamic designs of transport aircraft and airliners, there is no benefit to having a closely-cowled, in-line piston engine implementation for such applications.


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## wuzak (Aug 22, 2012)

Jabberwocky said:


> RAF didn't seem to think so.
> 
> From the Tempest II vs Tempest V tactical trials



Thanks for clearing that up.

From that sit the Tempest V with Hispano Mk IIs and Sabre IIB at +11psi boost (2400hp) had a top speed of 435mph. A Tempest V with Sabre IIA at +9psi boost (2200hp) and Hispano Mk Vs had a top speed of 236mph, and with Hispano Mk II and Sabre IIA a top speed of 432mph. 

The Tempest II is shown to have a top speed of 447-448mph with the Centaurus using +12psi boost. This probably shows that the Sabre was behind where it should have been in development - at the same time Merlins were being rated at +18, +21 and +25psi boost.

Also of interest to me is that the Tempest I with Sabre IV (2400hp) and leading edge radiators was nearly 20mph faster than the Tempest II and 30mph faster than the Tempest V. The Tempest I flying before the II did.

A later development of the V with an annular radiator and more developed Sabre (c. 3000hp) was also faster than the Tempest II.


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## 61fury (Aug 22, 2012)

thanks Buffnut


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## Ascent (Aug 23, 2012)

One of the troubles is that although we know about radial engine aircraft getting back to base with damaged engines what we don't know, and can't know, is how many crashed due to similar damage. What proportion of damaged engines made it home? Did the extra size of the engine mean that actually they were twice as likely to be hit, so a few getting home shouldn't be too suprising, or did it make no real difference?

Would it be remarked on in the same way if a liquid cooled engine got back to base with a damaged cooling system?

The trouble here is selective reporting, not as a deliberate thing but simply because those stories that come to us are those we find remarkable and we're too far removed in time from what happened to be able to go and collect the data we need.


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## Elmas (Aug 23, 2012)

Did the U.S. Navy ever use a liquid cooled engine on the planes operating from carriers?
I'm not aware of a single one.


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## CobberKane (Aug 23, 2012)

Sure, and if liquid cooled engines were ever getting back to base with a cylinder shot away it would be remarkable and we would know of instances. But we don't know of instances (or at least, no one supplied one) so by this logic its reasonable to believe it didn't happen.
This is about cooling. If you remove a cylinder from an air-cooled engine with a cannon shell you will completely deprive the engine of any cooling and in a matter of minutes it will stop. Even an bullet that will smash cooling fins of a radial will have a good chance of breaching the water jacket of an LC engine, depressurising the cooling system - and it will stop.


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## wuzak (Aug 23, 2012)

CobberKane said:


> Sure, and if liquid cooled engines were ever getting back to base with a cylinder shot away it would be remarkable and we would know of instances. But we don't know of instances (or at least, no one supplied one) so by this logic its reasonable to believe it didn't happen.
> This is about cooling. If you remove a cylinder from an air-cooled engine with a cannon shell you will completely deprive the engine of any cooling and in a matter of minutes it will stop. Even an bullet that will smash cooling fins of a radial will have a good chance of breaching the water jacket of an LC engine, depressurising the cooling system - and it will stop.



Which production liquid cooled engines could have a cylinder shot away without having half the engine missing? Well, I supopose the Vulture could count, DB 606 DB 610, maybe the V-3420, in which case only a quarter of the cylinders were shot away.

Sure the LC engine will stop once it has lost its coolant - but it won't necessarily be immediately.

I reiterate, the very few occasions where pilots have returned to base with parts of their air cooled engines is undoubtedly the exception, rather than the rule. Of course there is little way to prove that since those that didn't return to base were probably dead or unaware as to why their engine stopped. The guys that did return to base would probably have bailed had the known what had happened.


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## Shortround6 (Aug 23, 2012)

It is not only what we think or what we think we know now but what was thought at the time. The US army in the 1930s bought the argument that air-cooled engines were less vulnerable and specified only air cooled engines for "attack" aircraft. Aircraft intended for ground support and more likely to be hit by ground fire. 

While only a few radials may have made it home with cylinders missing many more made it home with damaged cylinders, dented or broken cylinder fins or damaged cylinder heads. Hits that would have caused leaks on a liquid cooled engine. While a liquid cooled engine won't stop immediately with a cooling hit and may even run at low power settings for 15-20 minutes getting "home" all depends on how far you are from "home" ( friendly air field or friendly farmer's field) when the damage occurs. Some pilots may have nursed an ailing liquid cooled engine even further. 

There is little doubt that the size of the liquid cooling system offers more target area than an equivalent air-cooled engine.


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## CobberKane (Aug 23, 2012)

Shortround6 said:


> It is not only what we think or what we think we know now but what was thought at the time. The US army in the 1930s bought the argument that air-cooled engines were less vulnerable and specified only air cooled engines for "attack" aircraft. Aircraft intended for ground support and more likely to be hit by ground fire.
> 
> While only a few radials may have made it home with cylinders missing many more made it home with damaged cylinders, dented or broken cylinder fins or damaged cylinder heads. Hits that would have caused leaks on a liquid cooled engine. While a liquid cooled engine won't stop immediately with a cooling hit and may even run at low power settings for 15-20 minutes getting "home" all depends on how far you are from "home" ( friendly air field or friendly farmer's field) when the damage occurs. Some pilots may have nursed an ailing liquid cooled engine even further.
> 
> There is little doubt that the size of the liquid cooling system offers more target area than an equivalent air-cooled engine.



Exactly. Examples of radials surviving the kind of damage that deprivers them of a cylinder are rare, but they did happen and serve to illustrate an extreme of the air colled engines resistance to battle damage. At the end of the day the cooling of any given cylinder of a radial is independent of the the others; a hit from, say a .30 or .50 cal round that would smash fins off a radial cylinder or even crack the cylinder itself has no effect on the airflow to the other cylinders. In contrast a similar hit to the cylinder of an LC engine will very probably breach the water jacket, and once this occurs in short order you will loose cooling to the entire engine (yes I know, some designs allowed isolation of half the system, but this still left multiple cylinders vulnerable to a singel hit). How thick is the alloy water jacket of an LC engine? 10mm maybe?
Regarding the length oftime an LC engine will run with a punctured cooling system, I'd suggest we are talking tens of minutes, tops. A cooling system is pressurised and any puncture will depressurise it, lowering the boiling point of the colant and turning it to gas. Gas escapes through holes very quickly. Try this for an experiment: take your car out on to the highway and run it up to operating temperature. Stop and take the radiator cap of. Keep driving (no crawling, if you were in an aircraft you would probably need fifty percent of throttle to stay in the air). How far do you think you will get?


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## gumbyk (Aug 23, 2012)

CobberKane said:


> Try this for an experiment: take your car out on to the highway and run it up to operating temperature. Stop and take the radiator cap of. Keep driving (no crawling, if you were in an aircraft you would probably need fifty percent of throttle to stay in the air). How far do you think you will get?



Now, try this same experiment, but with a hole in the block to an oil gallery.
One thing I haven't seen mentioned here is that you would not be able to sustain significant damage to an air-cooled engine without damaging the oil path, and as the oil is used as a coolant, it would have a significant effect on the cooling and operation of the engine.


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## davparlr (Aug 23, 2012)

CobberKane said:


> Try this for an experiment: take your car out on to the highway and run it up to operating temperature. Stop and take the radiator cap of. Keep driving (no crawling, if you were in an aircraft you would probably need fifty percent of throttle to stay in the air). How far do you think you will get?


 
 *Do not do this!* There is a warning on the cap. Automobile engines operate pressurized and can be at a temperature higher than boiling. Opening a radiator cap when hot can cause immediate boiling of coolant and a violent surge of coolant out the cap scalding any body part it touches.


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## wuzak (Aug 23, 2012)

Losing a cylinder on a radial isn't all about cooling. There is the oil issue, as mentioned by Gumbyk. There is also the small matter of parts flailing about without their normal constraints. Lose the master rod cylinder and you've lost that row - because all timing will be lost.

It's not just oil that will be pumped out - the fuel/air mix will be escaping to atmosphere, and possibly onto hot parts as a potential ignition source. This will also screw up the buddy of the lost cylinder, as for many radials two cylinders shared the same intak pipe (4 cylinders in an R-4360).

So, all is well, we have oil spewing out, bits and pieces flailing about, fuel/air mix being pumped out but hey, we still have cooling to all the other cylinders.


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## fastmongrel (Aug 24, 2012)

So Liquid cooled engines arent quite as fragile as some would have us believe and Radials cant really run properly with a cylinder missing and all its oil disappearing fast. 

My conclusion is getting hit with a supersonic lump of metal is generally a bad thing no matter whats hanging off the front of your plane. 

Does that about sum it up


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## buffnut453 (Aug 24, 2012)

Brilliant! Simply brilliant. Pithiest comment I've seen in a long time!


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## CobberKane (Aug 24, 2012)

wuzak said:


> Losing a cylinder on a radial isn't all about cooling. There is the oil issue, as mentioned by Gumbyk. There is also the small matter of parts flailing about without their normal constraints. Lose the master rod cylinder and you've lost that row - because all timing will be lost.
> 
> It's not just oil that will be pumped out - the fuel/air mix will be escaping to atmosphere, and possibly onto hot parts as a potential ignition source. This will also screw up the buddy of the lost cylinder, as for many radials two cylinders shared the same intak pipe (4 cylinders in an R-4360).
> 
> So, all is well, we have oil spewing out, bits and pieces flailing about, fuel/air mix being pumped out but hey, we still have cooling to all the other cylinders.



Come on Wuzak, you're being selective. As I said, loosing an entire cylinder is an extreme example, and as Shortround pointed out a hit that might dent the fins or knock a couple of valves off a radial' head would probably easily puncture the thin alloy of an LC engine's water jacket - which is the most robust part of the LC system. Regarding oil fuel and air being pumped everywhere, sure - the same thing is just as likely to happen to an LC engine it is no more or less vulnerable in this respect - the achilles heel of the LC engine was always cooling
Gumbyk, the role of oil in cooling a radial engine is very much secondary to that of air, which is why aircooled engines are called air-coled and oiled cooled engines are called oil-cooled. The fastest effect of depriving either type of engine (LC or AC) of oil would be seizure due to lack of lubrication, and in this they are equally vulnerable And oil is a viscous (thick) liquid that will never in an engine whereas water/glycol has vastly lower viscosity and higher volatility - it will escape far more quickly through a hole of a given size, depriving the LV engine of ALL its cooling. 

I guess we could all go on with this forever (which is part of the fun!), and I wouldn't like to try to justify selecting either the AC or LC engine as 'better' overall, but in summary I just can't see any reason to resile from my original view that air cooled radials are significantly more resistant to battle dammage than LC Vs and Inlines. The great preponderance of available experience and commentary seems to support me.


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## wuzak (Aug 24, 2012)

CobberKane said:


> Come on Wuzak, you're being selective. As I said, loosing an entire cylinder is an extreme example,



Am I?

It is an extreme example, but nonetheless it is the example you put forward to prove the air cooled engine's relative invincibility.





CobberKane said:


> a hit that might dent the fins or knock a couple of valves off a radial' head would probably easily puncture the thin alloy of an LC engine's water jacket - which is the most robust part of the LC system.



How do you "knock a couple of valves of a radial's head"? The valves are captive in the head, and if they aren't constrained the only way they can go is into the cylinder and piston, which could potentially cause all sorts of mess inside the engine.




CobberKane said:


> Regarding oil fuel and air being pumped everywhere, sure - the same thing is just as likely to happen to an LC engine it is no more or less vulnerable in this respect



There is truth to that, but it isn't the complete truth. A radial engine expels more heat through oil for a given power level than does a liquid cooled engine. This requires a larger oil cooling system (ie radiator). Radials also burn more oil, so need a larger system overall. 




CobberKane said:


> And oil is a viscous (thick) liquid that will never in an engine



Oil is less viscous at higher temperatures, such as in operating temperatures, than at room temperatures.




CobberKane said:


> whereas water/glycol has vastly lower viscosity and higher volatility - it will escape far more quickly through a hole of a given size, depriving the LV engine of ALL its cooling.



True.




CobberKane said:


> I just can't see any reason to resile from my original view that air cooled radials are *significantly* more resistant to battle dammage than LC Vs and Inlines. The great preponderance of available experience and commentary seems to support me.



Define _significantly_?

How do you explain this:



drgondog said:


> the P-38 had the worst record of a.) destruction of German aircraft per fighter lost in the air, and b.) the destruction of German aircraft on the ground.
> 
> The latter environment was the most hazardous light flak concentration fighter encountered in WWII. Why did the single engine Mustang achieve far superior ratios?
> 
> ...



Sure the P-47 has better ratios than the P-38, but it has worse ratios than the P-51 with its "significantly" more vulnerable liquid cooling system.

Of course we can't know the reasons that the aircraft were lost - and most probably had nothing to do with the engine.


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## Shortround6 (Aug 24, 2012)

Some radials were more "robust" than others and some liquid cooled engines were more "robust" than others. 

I don't think anybody is talking about "relative invincibility"but rather the ability to keep running at 30-50% or so of full power in order to get home, not keep fighting at 90-95% power. 
The R-2800 and some others had three main bearings so a missing cylinder or two would certainly throw the engine out of balance both in firing order ( although not much worse than a couple of bad plugs) and physically due to flopping pistons but in reality the pistons may have gone with the cylinder or been battered to pieces in short order banging against the crankcase. It rather depends on how far down in the cylinder the skirt went at the bottom of the stroke. 
Some radials ( most/all service French engines, the Russian M-88 and a few Italian ones) had two main beings for a two throw crankshaft and were operating at the limits of crankshaft flex to begin with. Throwing them out of balance might have resulted in excessive crankshaft flex and failure (broken crank) in short order. 
Other variables are the type of bearings, ball, roller, plain and of the plain bearings you had a variety of materials. Ball/Roller bearings will actually run for quite a while on little or no oil pressure. 
Differences in radial engine damage can be entire cylinder barrel gone and piston (or remains) flopping about, cylinder head gone but cylinder remaining so piston is riding in the bore ( keeps engine in balance), damage to head causing valves either to stay closed (rockers or push rods shot away) or valve retainers damaged allowing valves to fall inward and hit pistons. Usual result is bent valves and dings in piston top. It is possible to hole the piston. But you can do that by severe knocking or pre-ignition. Worst case in a holed piston is (in addition to loss of power) is pressurizing the crank case and blowing oil (or oil vapor) out the breathers. Small particles in the oil aren't good long term. A large amount of debris can block oil pick up/return tubes. 

Engines of both types can continue to run (obviously not at full power) with miss-firing cylinders or cylinders with damaged valve trains. I once had a timing chain jump on a V-8 engine, 16 bent push rods and 8 bent intake valves, exhaust valves were smaller and if bent slightly could be reground. the engine "ran" but would not make enough power to move the car on any kind of slope.  
Plenty of engines of both types have continued to run with broken valves, valve springs, rocker arms, or followers. 
On the other hand a hit to the carburetor could spell the end of some engines no matter what type they were. Hispanos and their Russian off-spring being a bit better in this regard with 6 carburetors, one for every two cylinders, but then you are much more likely to hit a Hispano carburetor. 

http://www.enginehistory.org/Museums/SNECMA/157 H-S 12Y.jpg

V-12s have larger areas of vulnerability to small arms ( non-cannon)fire . How each particular engine responds to such damage may very well be different but there seems to be little doubt that the radials, in general, were less vulnerable ( but not invulnerable) to combat damage. I _repeat_ *IN GENERAL* as one or two radials were rather notorious for not taking combat damage well.


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## CobberKane (Aug 24, 2012)

wuzak said:


> Am I?
> 
> It is an extreme example, but nonetheless it is the example you put forward to prove the air cooled engine's relative invincibility.
> 
> ...



---Looks like you answered your own question. Probably most of the losses had nothing to do with the engine? Sticking 'probably' in frony of an unsubsttianted opinion is a pretty lazy way of disguising it as a fact.


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## wuzak (Aug 25, 2012)

CobberKane said:


> ---Looks like you answered your own question. Probably most of the losses had nothing to do with the engine? Sticking 'probably' in frony of an unsubsttianted opinion is a pretty lazy way of disguising it as a fact.



Didn't say it was a fact.

From the start of this whole discussion I acknowledged that radial engined aircraft are less susceptible to battle damage than liquid cooled engines. What I disagreed with was the degree of difference.


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## wuzak (Aug 25, 2012)

Didn't notice the other replies:



CobberKane said:


> --I withdraw my assertion that the radial engine is invulnerable. I can't remember saying that, but obviously I must have.



I was being a bit sarcastic. You have portrayed liquid cooled engines as easily damaged and highly susceptible to battle damage, therefore air cooled engines must be _relatively_ invincible.




CobberKane said:


> --Why couldn't a hit destroy or incapacitate valves and cams without damaging the cylinder and piston. The valves and cams are outside the cylinder surely?



The head of the valve is on the piston side of the head.







The rocker and pushrod (on most WW2 radials) could be damaged or shot away, and the retaining collet on the valve may break so that the valve is no longer constrained. But the valve head will not pull through the port.




CobberKane said:


> ---but oil follows a distant second to air in cooling an air cooled motor.



Yes it does. That's not the point. The point is that an air cooled engine has a larger oil system than a liquid cooled engine, and thus is more vulnerable in that area.




CobberKane said:


> I would define 'significantly' as 'to a degree that makes a useful difference in practice'.



So is that 1/1,000,000? 1/100,000? 1/10?


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## CobberKane (Aug 25, 2012)

Spot on with the valve gear, brain fade on my part. Regarding everything else, I just watched the All Blacks do the Haka on top of the Wallabys and none of it seems to matter. To all American contributors, it's an Antipodean thing...


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## wuzak (Aug 25, 2012)

CobberKane said:


> Spot on with the valve gear, brain fade on my part. Regarding everything else, I just watched the All Blacks do the Haka on top of the Wallabys and none of it seems to matter. To all American contributors, it's an Antipodean thing...



Eden Park?

No suprise that the All Blacks beat the Aussies. Two reasons:

1. I undertsand the Aussies have never won there. 
2. The Wallabies are hopeless at the moment, and have been for some time.


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## CobberKane (Aug 25, 2012)

wuzak said:


> Eden Park?
> 
> No suprise that the All Blacks beat the Aussies. Two reasons:
> 
> ...


 
No, the Wallabys have had some good wins there, just not for twenty five years or so. And don't be too hard on them, beating the ABs at home is a big ask for any team. Now, if they'd just had radial engines...


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## Timppa (Aug 25, 2012)

A few anecdotes I could find quickly:

James A Goodson, 4th FG:


> I remember an early mission to Kiel, which brought home to me again the dependability of the P-47. The bombers were hitting the German U-boat base and naval base. As usual, we were giving them close escort over the target area. Suddenly, the heavy flak opened up, and almost immediately there were black woolly clouds with bright flashes in them floating by. One hit my engine, rocking the plane and filling the cockpit with the acrid smell of cordite. I heard the crump. Black oil hit the windscreen and I stated to lose power.
> ...
> [After a forced landing near Martlesham Heath]
> ...
> I climbed out onto the wing and looked at the smoking, stattered engine, covered in oil. The top of the front cowling was torn to bits and two cylinders were completely torn apart!



David McCampbell:


> My wingman, Roy Rushing, came back aboard the _Essex_ one day after being shot up by anti-aircraft fire and you could see the no. 9 piston pumping up and down. Roy sat in the cockpit with the "thumbs up" signal meaning the aircraft was ready in all respects for the next flight.



Ilyich Kardopoltsev:


> I remember the engines on Lavochkins were really good. I got hit by flak in the engine, and two lower cylinders were shattered to pieces… But I made it home. Mech opened cowls, and we saw some bits falling out. And I can’t say that I lost power drastically.


Kardopolysev


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## drgondog (Aug 25, 2012)

wuzak said:


> How do you explain this:
> 
> Sure the P-47 has better ratios than the P-38, but it has worse ratios than the P-51 with its "significantly" more vulnerable liquid cooling system.
> 
> Of course we can't know the reasons that the aircraft were lost - and most probably had nothing to do with the engine.



My theory about P-38 vs P-51 strafing losses (since both have liquid cooled engines) is that the P-38 was a.) a far bigger target, and .b) had twice as much vulnerability to engine fires. The P-38 did have the ability to casually shut down one engine if the problem was a slow coolant leak but a leaky fuel line could flash before the pilot would notice a problem.

But still, just a theory.


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## CobberKane (Aug 25, 2012)

Timppa said:


> A few anecdotes I could find quickly:
> 
> James A Goodson, 4th FG:
> 
> ...



Along with Clayton Gross acount of flying back to base with a cylinder missing that makes four accounts of radial engines surviving this kind of damage in three different models of fighter, all getting home under power. It seems reasonable to expect there were more. Still waiting for an account of a liquid cooled engine getting home with a smashed cylinder and still running.


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## Shortround6 (Aug 25, 2012)

only two different engines though.


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## drgondog (Aug 25, 2012)

Sumner Wiliiams Scout Force (Experimental) was hit by a B-17 and lost' three cylinders - left bank - over Paris and made it back to Steeple Morden. September Engineering Report 355th FG.


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## CobberKane (Aug 25, 2012)

drgondog said:


> Sumner Wiliiams Scout Force (Experimental) was hit by a B-17 and lost' three cylinders - left bank - over Paris and made it back to Steeple Morden. September Engineering Report 355th FG.



I thought about B-17s, but I imagine thatin most instances a pilot who knew an engine had sustained that kind of damage would have cut it and relied on the other three. Maybe in some cases the pilot might have been unaware how badly hit the engine was or had to keep it running due to other engines being knocked out, though.


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## CobberKane (Aug 25, 2012)

"only two different engines though"

True, Shortround, and the R-2800 does seem to be a stand-out in this respect. I guess it would also help that the engine was so widely used and saw so mauch action, and that Japanese, Russian and German radials might be under-represented because most of the accounts we can sourse come from the english speaking allied nations. Still, if I was in a single engine aircraft listening to bullets hit the engine in front of me, I would hope the engine was a R-2800 above any other, I think...


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## wuzak (Aug 25, 2012)

CobberKane said:


> I thought about B-17s, but I imagine thatin most instances a pilot who knew an engine had sustained that kind of damage would have cut it and relied on the other three. Maybe in some cases the pilot might have been unaware how badly hit the engine was or had to keep it running due to other engines being knocked out, though.



Not a B-17, but _hit by a B-17_ and lost 3 cylinders one one bank - that was a V-12 and I presume a P-51.


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## CobberKane (Aug 26, 2012)

Ah, I missread. A P51 you would assume - if it ahd been a P38 you would think it would have been mentioned. It would be interesting to know the nature of the dammage to the engine and how far he had to go to get back to base.


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## wuzak (Aug 26, 2012)

He was over Paris and had to make it back to England, according to Drgondog. According to Google Maps it is about 300 miles.


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## Timppa (Aug 26, 2012)

> Chief mechanic Unteroffizier Rommer inspects his Fw 190 which returned from ops to Siverskaya in mid- 1943 with two complete cylinder heads shot away from its BMW engine by Soviet groundfire.
> Despite chronic damage to the powerplant, the pilot returned safely and made a perfectly routine three point landing.


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## drgondog (Aug 26, 2012)

CobberKane said:


> I thought about B-17s, but I imagine thatin most instances a pilot who knew an engine had sustained that kind of damage would have cut it and relied on the other three. Maybe in some cases the pilot might have been unaware how badly hit the engine was or had to keep it running due to other engines being knocked out, though.



He didn't knw he had been hit. He stated that the engine (of his P-51D-5) was running rough but temps were only 'high normal'. He was prepared to bail out at first sign of dangerous engine temperatures.


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## stona (Aug 26, 2012)

On 27/4/41 the minutes of a meeting with Milch,specifically in relation to the Bf 110 note.

"Combat experience has shown that 50% of aircraft put out of commission were done so by hits in the cooling system. New developments are therefore planned to include partial armour plating."

No comparison with radial engines and only relevant to one liquid cooled type,but it was obviously something of concern to the RLM.

Steve


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## CobberKane (Aug 26, 2012)

stona said:


> On 27/4/41 the minutes of a meeting with Milch,specifically in relation to the Bf 110 note.
> 
> "Combat experience has shown that 50% of aircraft put out of commission were done so by hits in the cooling system. New developments are therefore planned to include partial armour plating."
> 
> ...



Fifty percent is a pretty powerful indication of the vulnerability of LC engines to battle damage, unless Damlier Benz was prticularly fragile, and I've never heard that before


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## wuzak (Aug 26, 2012)

CobberKane said:


> Fifty percent is a pretty powerful indication of the vulnerability of LC engines to battle damage, unless Damlier Benz was prticularly fragile, and I've never heard that before


 
Or just the vulnerability of the Bf 110.


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## CobberKane (Aug 26, 2012)

wuzak said:


> Or just the vulnerability of the Bf 110.


 
You mean the cooling system of the 110 might have somehow been more vulnerable than that of another aircraft that used the same engine, like the 109? I would have thought that having an extra engine in reserve would have made the 110 less vulnerable - it would require hits to two seperate cooling systems to knock out both engines.

It would seem that:

1. Instances of radial engines continuing to run with one or more cylinders smashed certainly did exist and are not too difficult to find.
2. If instances of liquid cooled engines continuing to run with cylinders smashed exist, for some reason accounts are not easy to find.
3 In the case of the Bf110, which used the DB601 and DB605, two of the most widely produced liquid cooled engines of the war, a whopping fifty percent of combat losses were due to the cooling system being hit. And this in a twin engined aircraft with an extra donk to fall back on if only one was put out of action.

Come on over to the dark side, Wuzak. The water is fine.


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## wuzak (Aug 26, 2012)

1. There are a few instances of radial engines aircraft having cylinders "smashed" and returning, but that doesn't tell us how many didn't return with cylinders being "smashed".
2. It is more difficult to "smash" cylinders in a liquid cooled V-12, because of the monoblock construction.
3. The installation of the cooling system can make a huge difference between its vulnerability. Just because 50% of combat losses are attributed to the cooling system in one aircraft it doesn't necessarily follow that the number would hold for another aircraft with the same engine. Also it may be that only one engine has to be compromised in the Bf 110 to cause its loss, which means that its two cooling systems make it twice as vulnerable as a single.

Looking back at Stona's post, the statement is that _"50% of aircraft put out of commission"_. Does that mean that they are combat losses or merely unavailble due to requiring repair?


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## CobberKane (Aug 26, 2012)

wuzak said:


> 1. There are a few instances of radial engines aircraft having cylinders "smashed" and returning, but that doesn't tell us how many didn't return with cylinders being "smashed".
> 2. It is more difficult to "smash" cylinders in a liquid cooled V-12, because of the monoblock construction.
> 3. The installation of the cooling system can make a huge difference between its vulnerability. Just because 50% of combat losses are attributed to the cooling system in one aircraft it doesn't necessarily follow that the number would hold for another aircraft with the same engine. Also it may be that only one engine has to be compromised in the Bf 110 to cause its loss, which means that its two cooling systems make it twice as vulnerable as a single.
> 
> Looking back at Stona's post, the statement is that _"50% of aircraft put out of commission"_. Does that mean that they are combat losses or merely unavailble due to requiring repair?


 
Wuzak my friend, you are an irredeemable contrarian. About the only point of consensus we share is that the Wallabies can’t play rugby. Now if you will excuse me I hear some Jehovah’s Witnesses coming up the driveway – perhaps they will prove less immune to the ravages of reasoned argument.


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## wuzak (Aug 27, 2012)

CobberKane said:


> Wuzak my friend, you are an irredeemable contrarian. About the only point of consensus we share is that the Wallabies can’t play rugby. Now if you will excuse me I hear some Jehovah’s Witnesses coming up the driveway – perhaps they will prove less immune to the ravages of reasoned argument.



You disagree that the same engine on two different aircraft can have two different levels of vulnerability depending on the details of the installation? That goes for air cooled engines too, btw.


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## Shortround6 (Aug 27, 2012)

There are a couple of things going on here;

1. is the likelihood of a particular airplane or engine installation to suffer a damaging hit ( or any hit).
2. is the likelihood of a particular airplane or engine installation to keep running, at least at low levels, once it has suffered the "hit".

Take for example an Allison powered P-40, an Allison powered P-51 and the P-38. With everything concentrated forward of the fire wall, logic would tell us that the P-40, presenting a smaller target area, would be less likely to suffer a hit to the propulsion system. Some people thought that, given most pilots/AA gunners failure to apply enough lead hits in the front half of the plane were less common that hits in the rear half. Take that as you will, since there was more vital _STUFF_ in the front half of the plane you are not going to find many pictures of planes that made it back with multiple cannon hits to the nose. P-40 radiators/oil cooler were under the engine and the entire powerplant was a compact package. The P-51 was more spread out and the P-38 even more so. P-38 due to size was going to get hit more, effect of the hits is the other part of the question.
Given that all 3 had Allison engines I would guess that given equivalent hits in the radiator/oil cooler/piping that all three would pretty much react the same. Engine would keep running for about the same period of time at about the same power level. Subject to production variation of engines, actual amount of coolant in each system and actual amount of oil available. 

Basically air-cooled engines had one less system to hit. This, from many target aspects, reduced the area of vulnerability. If the engine, fuel and oil systems were not hit few records were kept of hits that "_might have_" hit a radiator/s coolant had they been present. 

Some radial engines did show an ability to run ( at least for a while) with complete cylinders missing, as in totally gone from the engine. Radial engines were a collection of individual cylinders. Pretty much separate or paired intakes, individual valve gear. While a good hit to the front crankcase could screw up the cam ring pushrod system to the entire engine a good hit anywhere along a V-12 head could screw up the valves of the entire bank or at least from the point of the hit to the end of the engine away from the cam/s drive. A V-12 can have some extremely battered cylinder blocks, to the point of seeing into a few cylinders, but the head/s have to stay where they are. Lifting the cylinder head ( assuming the engine has a separate cylinder head) means the cam drive is disconnected meaning 1/2 the engine is now longer producing any power. Maybe the V-12 can make it back on 6 cylinders ???? I don't know.


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## CobberKane (Aug 28, 2012)

Shortround6 said:


> There are a couple of things going on here;
> 
> 1. is the likelihood of a particular airplane or engine installation to suffer a damaging hit ( or any hit).
> 2. is the likelihood of a particular airplane or engine installation to keep running, at least at low levels, once it has suffered the "hit".
> ...


 
Short of setting up a few hundred engines of different types and machine gunning them to see what happens we are never going to know exactly how damage resistant one is compared to another. However, anecdotal evidence is enough to draw some reasonable conclusions – for example the R2800 was a particularly tough engine. That doesn’t mean the various fighters that used it were equally resistant to battle damage of course, although there does seem to have been a philosophy of over-engineering common to most American fighters. Even the relatively svelte P 51 was a fair bit heavier than contemporary spitfires.
The original question posed in this thread was; what were the relative advantages and disadvantages of air-cooled and liquid cooled engines and which was better than the other in WWII. As to the second part of the question, who can say? Many excellent fighters were powered by both types. I think you could say the air cooled motor was better in some roles, as in transport aircraft where drag was not such an issue because of low speed, or heavy daylight bombers where a radials resistance to battle damage could be incorporated into an overall design stressing toughness, like the B-17. But the LC engine also had its advantages and was undoubtedly a better choice in other cases. 
The air-cooled radial design has inherent advantages over the liquid cooled V in terms of its capacity to withstand battle damage. This does not mean every radial was tougher than every inline V, or that every air-cooled fighter was more damage resistant than every liquid-cooled fighter, but its facile to say we should discount the weight of anecdotal evidence concerning these engines because the data cannot be correlated. Who cares if we cannot say whether a radial was on average “ 1.8 times” more resistant to battle damage than an inline V? The practical experience was that radials frequently demonstrated an ability to withstand battle damage that would have incapacitated a contemporary inline V, and did so to a degree that made a useful contribution to the survivability of the aircraft. 
Incidentally, one secondary benefit of the radial – it contributed greatly to the behaviour of the fighter in formation flying. The P 47 in particular had an excellent reputation as a formation aircraft because of the way it would ‘stop’ when throttled back. In contrast aircraft like the P51 were much more streamlined and even when the throttle was closed it took a while for the plane to slow. In effect, the P47 had better brakes, I guess.


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## Rick65 (Aug 28, 2012)

The Tempest is a plane of interest in this discussion because it was designed for both types of engine and was hence changed from in line to radial power with minimal change, certainly with less revisions than required to go the other way with the Fw 190.
As previously stated the performance of the Centaurus powered Tempest II was only marginally improved over the the Sabre IV powered Tempest V.
What is amazing is the difference in capacity of the engines, with the radial Centaurus being a 3270 cu inch engine that delivered 2520hp at 2700 rpm. 
The Sabre IV produced 2240hp from 2240cu inch at a high 4000rpm. The two versions of the plane were similar in terms of performance, dry weight and I seem to remember (but can't find) a quote that the radial engined II was nicer to fly and had slightly better range despite the larger engine.
The Sabre was an idiosynchratic engine that was probably never fully developed (as was the also sleeve valve Centaurus) but the performance of the two engines in the Tempest supports the argument that the watercooled in line is more efficient in producing horsepower from a given capacity but was not necessarily lighter when cooling system etc is taken into account.


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## CobberKane (Aug 28, 2012)

Rick65 said:


> The Tempest is a plane of interest in this discussion because it was designed for both types of engine and was hence changed from in line to radial power with minimal change, certainly with less revisions than required to go the other way with the Fw 190.
> As previously stated the performance of the Centaurus powered Tempest II was only marginally improved over the the Sabre IV powered Tempest V.
> What is amazing is the difference in capacity of the engines, with the radial Centaurus being a 3270 cu inch engine that delivered 2520hp at 2700 rpm.
> The Sabre IV produced 2240hp from 2240cu inch at a high 4000rpm. The two versions of the plane were similar in terms of performance, dry weight and I seem to remember (but can't find) a quote that the radial engined II was nicer to fly and had slightly better range despite the larger engine.
> The Sabre was an idiosynchratic engine that was probably never fully developed (as was the also sleeve valve Centaurus) but the performance of the two engines in the Tempest supports the argument that the watercooled in line is more efficient in producing horsepower from a given capacity but was not necessarily lighter when cooling system etc is taken into account.



I agree - one of the big adavantages of liquid cooling is the ability to more effectively regulate engine temperature. This has benifits in that the engine can be more reliably maintained at optimum temperature, which will maximise engine efficincy and allow finer engineering tolerances than than an air-cooled engine. This will translate into more horsepower for a given capacity, or better fuel economy, or both.
Having said that, if a thirty litre aircooled engine running at a lower state of tune can return similar figures to a more highly tuned twently litre liquid cooled engine, what's the difference? Unlike car or motorcycle manufacturers of today, producers of WWII aero-engines has no incentive to restrict themselves to arbitrary capacity limits


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## wuzak (Aug 28, 2012)

What's the difference? Frontal area, drag? For the same hp, that is.


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## buffnut453 (Aug 28, 2012)

CobberKane said:


> Unlike car or motorcycle manufacturers of today, producers of WWII aero-engines has no incentive to restrict themselves to arbitrary capacity limits



But they still had to fit the engine into the form factor of an aircraft. Look at the late-war "next generation" radials that had 4 rows of cylinders - IIRC all of them had major cooling and reliability issues (although, granted, not many of them saw front-line service). You can't just keep adding capacity like it's a never ending supply of power - at some point, you'll reach some other logical design limit like cooling airflow to rear banks of cylinders or an engine that has too great a diameter to be a practical proposition.


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## Timppa (Aug 28, 2012)

wuzak said:


> What's the difference? Frontal area, drag? For the same hp, that is.



Ultimately, well designed radial engined plane did not have more drag. The most obvious examples are airframes that used both types:
Tempest V - Tempest II
LaGG3 - La7 (in this case the latter had actually less drag)

Of the early war planes you may compare Bf109E and A6M3, both with about the same power and same speed.


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## wuzak (Aug 28, 2012)

Corect me if I'm wrong, but the LaGG 3 had susbtantially less power than the La 7. 

And there were some liquid cooled installations that weren't well designed.

When using leading edge radiators the Tempest I was some 20mph faster than the Tempest II with less power. And a Tempest V with an annular radiator was also about 20mph faster than the Tempest II. One Fury prototype was also fitted with the Sabre with annular radiator, an was about 25mph faster than the Centaurus version. In both those examples the Sabre had a bit more power (about the same difference between Tempest II and standard Tempest V).

I don't know much about the A6M3 to compare. E had a top speed of around 355mph.


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## Shortround6 (Aug 28, 2012)

There are definite limits as to how big you can make a cylinder, either air cooled or liquid cooled without resorting to trickery like triple ignition. There are limits on stroke, both in piston speed and from a fuel burn stand point. This rather restricts engine configurations. 

The DB 603 and the Russian AM-35/38 series were about as big as you could make a V-12. 18 cylinder engines are pretty much limited to radials and triple banked inlines (arrow head engines?). Going to 24 cylinders solves the displacement problem for the inline ( read liquid cooled) but leaves the choice of one crankshaft or two. One didn't seem to work well. The more cylinders the higher the maintenance load. 

The Griffon and the Sabre were almost the same displacement, the Sabre was more powerful (maybe/depending?) but was about 500lbs heavier for a single stage Sabre vs a two stage Griffon. That is without cooling systems. Power available over 20,000 is a lot closer than power down low. 
The Centaurus is about 150-200lbs heavier than the Sabre but has no cooling system (ok a bigger cowl and cowl flap set up) Power at altitude may favor the Sabre, Max cruise may favor the radial. 

When comparing top speeds it is nice to know the altitudes. Changing altitudes by even 2,000ft can mean around a 4% difference in drag. 

Comparing identical or near identical airframes with different engines is hard enough. trying to draw conclusions from different airframes with different engines introduces too many variables.

On a small scale the Fairchild 24 cabin monoplane was available for a number of years with either the inline 6 air cooled Ranger engine and the Warner radials. over the years the HP of the engines did vary but in general given engines of the same power the Rangers were faster but the Warner radial powered planes, being lighter, climbed better.


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## gjs238 (Aug 28, 2012)

61fury said:


> A question here, civilian airliners before the Jet Age all seemed to be radials. Was there a reason for this? Were there any liquid cooled airliners? I know fighting and flying and just flying are different goals but the radial engine era seemed to last until jets took over.


 Didn't blimps and Zeppelins use water cooled engines?


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## gjs238 (Aug 28, 2012)

Elmas said:


> Did the U.S. Navy ever use a liquid cooled engine on the planes operating from carriers?
> I'm not aware of a single one.


 Didn't that have something to do with storing ethleyne glycol on ships?


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## stona (Aug 28, 2012)

gjs238 said:


> Didn't that have something to do with storing ethleyne glycol on ships?



Why would that be? It's not particularly flammable,certainly when compared to aircraft fuels,nor is it difficult to store. Typical flash point of petrol (gasoline)is around -40 C whereas ethylene glycol is over 100 C.

I'm just wondering,it maybe the US Navy had a good reason I'm unaware of. You wouldn't want your matelots drinking the stuff 

Steve


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## Shortround6 (Aug 28, 2012)

61fury said:


> A question here, civilian airliners before the Jet Age all seemed to be radials. Was there a reason for this? Were there any liquid cooled airliners? I know fighting and flying and just flying are different goals but the radial engine era seemed to last until jets took over.



The only liquid cooled airliners were a Few Canadian and British plane using Merlins. At the time the British (including the Commonwealth) had one heck of a trade deficit problem and _foreign_ (meaning US) engines simple could not be afforded. That left the Merlin, Griffon, Sabre, Hercules and Centaurus engines. The Sabre and Griffon found no takers at all in the commercial field and Rolls, by expending a fair amount of effort and trading a bit on the Merlin reputation did make the above mentioned sales. Commercial Hercules ( even licence built in France) and Centaurus engines filled the British commercial aircraft until the jet and turbo prop. 
The Americans, for a variety of reasons, dominated the post war commercial aircraft market and so did American engines, which after the Allison stopped production, meant air cooled radials. 
One less system to fool with and maintain and with acceptably low operating costs ( and airline owners are a hard headed tight fisted bunch) the air cooled radial did the job.


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## Shortround6 (Aug 28, 2012)

Some, but the US Navy had a lot of bad experiences with water cooled engines in the 20s, Liberties, Curtiss and Packard engines and decided enough was enough. A broken water pipe over land is bad enough, a broken water pipe or leaky radiator over water is a lost aircraft and probably a lost pilot/crew. The Navy was not adverse to looking at or even funding an occasional water/liquid cooled project in order to keep abreast of the state of the art or even move for adoption should the gap between liquid and air cooled become to great. 
It didn't.


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## CobberKane (Aug 28, 2012)

Timppa said:


> Ultimately, well designed radial engined plane did not have more drag. The most obvious examples are airframes that used both types:
> Tempest V - Tempest II
> LaGG3 - La7 (in this case the latter had actually less drag)
> 
> Of the early war planes you may compare Bf109E and A6M3, both with about the same power and same speed.



The 109 had about 17% more power and 20mph more speed than the zero, so hard to draw conclusions from that. The Tempest is a good example though - I think they pinched the idea of the contra-rotating fan behind the prop from the Fw190. The 190 was probably the most influentual fighter of the war in terms of demonstrating that the radial was still right up there with LC engines.


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## cimmex (Aug 29, 2012)

CobberKane said:


> I think they pinched the idea of the contra-rotating fan behind the prop from the Fw190. The 190 was probably the most influentual fighter of the war in terms of demonstrating that the radial was still right up there with LC engines.



The fan behind the prop of the Fw190 has the same turning direction as the propeller but around three time the speed. 
Cimmex


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## CobberKane (Aug 29, 2012)

cimmex said:


> The fan behind the prop of the Fw190 has the same turning direction as the propeller but around three time the speed.
> Cimmex


 
Sorry, I was thinking 'counter-rotating props'.


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## CobberKane (Aug 29, 2012)

Sorry, created in error


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## CobberKane (Aug 29, 2012)

wuzak said:


> What's the difference? Frontal area, drag? For the same hp, that is.


 
Yes, by saying 'for the same horsepower' you are restricting yourself artificially in the same way a motorcyle manufacturor is by saying 'we must not go beyond 750cc'. In practice the designer of the figher aircraft is going to use the engine that gives the best balance of performance, fuel consumption etc, irrespective of whether it is defficient in one particular area like drag. The fact that radial engine fighters were matching the performance of the best inline engines right up to the end of the war indicates that their disadvantage in terms of drag was not enough to place the radial engine at a disadvantage compared to the inline V in practise .
I guess in theory it would be possible to build a mile-long V-100000 with no more frontal area than a V-12, whereas a radial of increasing capacity would have to get wider and wider. In practice all that was laid aside by the jet engine, and even if for some hypothetical reason the jet could not be made to work other alternatives eventually came along for driving airscrews.

Oh, I note that someone posted yet another 'urban myth' example of a radial engine fighter gettin home with smashed cylinders (plural). Still waiting for a similar account of an LC engine doing that...


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## gjs238 (Aug 29, 2012)

CobberKane said:


> ...whereas a radial of increasing capacity would have to get wider and wider.


 The radials grew in length as well as rows were added.


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## wuzak (Aug 29, 2012)

CobberKane said:


> Oh, I note that someone posted yet another 'urban myth' example of a radial engine fighter gettin home with smashed cylinders (plural). Still waiting for a similar account of an LC engine doing that...



I never said it was an urban myth - I said those who managed it were extremely lucky.

Drgondog already gave you an account of a P-51 which returned to base with 3 "smashed cylinders".


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## wuzak (Aug 29, 2012)

CobberKane said:


> Yes, by saying 'for the same horsepower' you are restricting yourself artificially in the same way a motorcyle manufacturor is by saying 'we must not go beyond 750cc'. In practice the designer of the figher aircraft is going to use the engine that gives the best balance of performance, fuel consumption etc, irrespective of whether it is defficient in one particular area like drag. The fact that radial engine fighters were matching the performance of the best inline engines right up to the end of the war indicates that their disadvantage in terms of drag was not enough to place the radial engine at a disadvantage compared to the inline V in practise .



There are practical limits to anything.

Adding length to a V engine will lead to diminishing returns because of crankshaft flexibility, and other associated issues. Adding cylinders to air-cooled radials can increase the diameter (more cylinders per row) and/or length (more rows). After a cerain number of rows it will be getting very difficult to cool the rear cylinders.

Note that liquid cooled engines can be radials too - R-2160 Tornado, Lycoming, XR-7755, BMW 803, for example. Granted, these never went beyond prototype stage.

You will notice that the air cooled engine powered fighters late in the war which matched liquid cooled ones were generally more powerful.


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## wuzak (Aug 29, 2012)

CobberKane said:


> Yes, by saying 'for the same horsepower' you are restricting yourself artificially in the same way a motorcyle manufacturor is by saying 'we must not go beyond 750cc'.



Thought I had better look to see what my post was in response to. And there it was - you were the one that introduced the same power level stipulation.




CobberKane said:


> Having said that, if a thirty litre aircooled engine running at a lower state of tune can return similar figures to a more highly tuned twently litre liquid cooled engine, what's the difference? Unlike car or motorcycle manufacturers of today, producers of WWII aero-engines has no incentive to restrict themselves to arbitrary capacity limits


 


wuzak said:


> What's the difference? Frontal area, drag? For the same hp, that is.


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## tyrodtom (Aug 29, 2012)

cimmex said:


> The fan behind the prop of the Fw190 has the same turning direction as the propeller but around three time the speed.
> Cimmex


How much power was consumed by that cooling fan ?
If it was so successful in cooling the engine, why did no one else copy it?


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## Shortround6 (Aug 29, 2012)

tyrodtom said:


> How much power was consumed by that cooling fan ?
> If it was so successful in cooling the engine, why did no one else copy it?



It was "copied". Some Martin Mariner patrol bombers used fan cooled R-2600s. The P-47J used a fan cooled R-2800 ( dropped for the P-47M&N) I am not Sure if the Russians had a few fan cooled installations of the Ash-82. At least one Bristol Hercules commercial installation post war used fan cooling. I am not sure about the Hawker tempest II or Fury. 

That is off the top of my head, there may certainly well be others without getting into buried or pusher installations.


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## cimmex (Aug 29, 2012)

Power needed to drive the fan was 80 to 100hp depends on 12 or14 blades.
Cimmex


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## RCAFson (Aug 29, 2012)

Shortround6 said:


> The only liquid cooled airliners were a Few Canadian and British plane using Merlins. At the time the British (including the Commonwealth) had one heck of a trade deficit problem and _foreign_ (meaning US) engines simple could not be afforded. That left the Merlin, Griffon, Sabre, Hercules and Centaurus engines. The Sabre and Griffon found no takers at all in the commercial field and Rolls, by expending a fair amount of effort and trading a bit on the Merlin reputation did make the above mentioned sales. Commercial Hercules ( even licence built in France) and Centaurus engines filled the British commercial aircraft until the jet and turbo prop.
> The Americans, for a variety of reasons, dominated the post war commercial aircraft market and so did American engines, which after the Allison stopped production, meant air cooled radials.
> One less system to fool with and maintain and with acceptably low operating costs ( and airline owners are a hard headed tight fisted bunch) the air cooled radial did the job.



The other factor was the incredibly low price of avgas in those days. I suspect that if ICE were still used today for airliners, that they would all be liquid cooled because of the lower specific consumption.


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## tyrodtom (Aug 29, 2012)

Shortround6 said:


> It was "copied". Some Martin Mariner patrol bombers used fan cooled R-2600s. The P-47J used a fan cooled R-2800 ( dropped for the P-47M&N) I am not Sure if the Russians had a few fan cooled installations of the Ash-82. At least one Bristol Hercules commercial installation post war used fan cooling. I am not sure about the Hawker tempest II or Fury.
> 
> That is off the top of my head, there may certainly well be others without getting into buried or pusher installations.



What looks like a cooling fan in the cowling of the La-5 and La-7 is a controllable cooling veturi louvers, needed to limit cooling air during Russia's extreme cold.

I know helicopters powered by radials had a cooling boost, but wasn't aware of any other fixed wing aircraft using the FW solution.


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## Shortround6 (Aug 29, 2012)

CobberKane said:


> Yes, by saying 'for the same horsepower' you are restricting yourself artificially in the same way a motorcyle manufacturor is by saying 'we must not go beyond 750cc'. In practice the designer of the figher aircraft is going to use the engine that gives the best balance of performance, fuel consumption etc, irrespective of whether it is defficient in one particular area like drag. The fact that radial engine fighters were matching the performance of the best inline engines right up to the end of the war indicates that their disadvantage in terms of drag was not enough to place the radial engine at a disadvantage compared to the inline V in practise .
> I guess in theory it would be possible to build a mile-long V-100000 with no more frontal area than a V-12, whereas a radial of increasing capacity would have to get wider and wider. In practice all that was laid aside by the jet engine, and even if for some hypothetical reason the jet could not be made to work other alternatives eventually came along for driving airscrews.



Basically the air cooled and liquid cooled engines stayed pretty much neck and neck power wise for most of their history. One or the other would have an advantage for a few months or even a year or two but the pendulum usually swung back. 

In the world of fighters I can think of only 3 examples that offer a good comparison. The P-36/P-40 combination. The Hawker Tempest and the FW 190. 

Most other engine "swaps" entailed too much of a power change to make valid comparisons. Since these are generalizations I am doing some rounding up/down. 
Italians replaced 900-1000hp radials with 1200hp German V-12s. gaining 20-33% in power makes it hard to access the change in drag alone.
Japanese replaced a 1200hp (or 1400 very unreliable hp) V-12 with a 1500hp radial. Again making it hard to figure out actual benefit/cost.
Russians replaced 1200hp V-12 with 1500-1700hp radial. This radial wasn't even a gleam in the designers eye when the particular V-12 was already several years old. 

The P-36/40 offers the best possibilities for looking at the situation. It used 2 different radials (one in two different configurations) and two different liquid cooled engines and spanned 7-8 years in time. There are even a few more experimental/prototype engine installations. ALL of the engines varied in "nominal" output from 1000 to 1300hp with the more common spread being even closer. The American engines also had pretty much access to the same quality fuel at the same time. 

The Wright Cyclone 9 and the P&W Twin Wasp 14 battled for top dog in the US since 1933-34 starting at around 800-850hp. by the late 30s they were over 1000hp (if not 1100hp) and while the P&W (R-1830) was a little smaller in diameter it was a little heavier than the Wright R-1820. Allison comes on the scene with the V-1710, it splits the difference weight wise (not including cooling system) but is a bit down on power. Things do get a bit confusing as Wright is the first to offer a two speed supercharger which improves power at both low altitude (take-off) and _HIGH_ altitude. High at this point in time being anything much over 10,000ft. Allison offers an "altitude" rated engine, max power at around 11,000ft with it's single speed supercharger. P&W is working on a two stage supercharger. 

Getting back to the nitty-gritty. During flight tests of the early P-40 with it's 1040hp engine at 11,000ft or so they figure that the P-36 with it's 1200hp (take-off) R-1830 had 22% more drag than the V-12 powered plane. Speeds for the Hawk 75 ( commercial P-36) were between 310-326 mph depending on source, engine fitted ( which particular r-1830 or R-1820) and armament fit. The Early P-40 went from 357 down to 345mph as more guns, armor and self sealing tanks were fitted. These speeds are between 10,000-15,000ft. A Hawk 75 demonstrator (P&W R-1830) with 2 stage supercharger was flown at the 1939 army fighter trials, performance is so far unpublished. Later P-40s got a lot heavier but also got more powerful V-1710 engines. The P-40F with the Merlin was supposed to be good for 364mph at 20,000ft where the air was thinner (less drag). P&W was battling back with things like the XP-42 







Which was also flown at the 1939 trials. it was slower than the XP-40 and had cooling problems. Later a P-40 airframe was bailed back to P&W for engine development and in late 1942 P&W got this aircraft up to 386mph with an R-1830 engine making it one of the fastest P-40s ever. P&W had learned a lot in 3 1/2 years about two stage superchargers and radial engine installations. Please not that this aircraft may have done it's high speed more in the 20,000ft area than down lower with benefit of thinner air for less drag. It was also unarmed I believe for less drag and weight. It is this gain in knowledge than makes comparing planes built even a few years apart difficult in deciding which "engine" or plane was best. In about 4 years P&W using the same basic engine but a different supercharger set up improved the speed of the same basic airframe by by around 60mph. This is better than Rolls Royce managed to do with the Merlin and Spitfire but then the 1938/39 Spitfire was a lot further ahead of the 1938 P-36 to begin with 
I would also note that in 1942 the R-1830 was strictly a 2nd class engine and the big effort was going into the R-2800 and R-4360. Still, what was learned about baffling, cowl design and scoops could be applied to the big engines.


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## Shortround6 (Aug 29, 2012)

RCAFson said:


> The other factor was the incredibly low price of avgas in those days. I suspect that if ICE were still used today for airliners, that they would all be liquid cooled because of the lower specific consumption.



Some of those radials didn't do to bad for fuel consumption while cruising. Some of them were well within 10% or so of the contemporary liquid cooled engines if not even closer. Maybe the cost difference today would out-way the increased maintenance costs. The Wright turbo compound was noted for it's low fuel consumption but was unpopular for all but the longest range routes because of it's maintenance costs. The Candair North Star used two stage Merlins with inter-coolers that could also be used as charge heaters when cruising ( to prevent fuel puddling in the intakes.) An interesting comparison is the North Star 5 with P&W R-2800s which didn't use much more fuel for the same range. I will try to post numbers from the 1954-55 issue of Jane's later ( assuming that they are accurate)


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## CobberKane (Aug 29, 2012)

wuzak said:


> There are practical limits to anything.
> 
> Adding length to a V engine will lead to diminishing returns because of crankshaft flexibility, and other associated issues. Adding cylinders to air-cooled radials can increase the diameter (more cylinders per row) and/or length (more rows). After a cerain number of rows it will be getting very difficult to cool the rear cylinders.
> 
> ...


 
Yes, in practice six cylinders seems to have been the about where designers stopped making engines 'longer' and added another bank. And after they got to two banks of six they added another couple. These four bank engines seem to have been the way things were heading but I can only think of the RR Vulture and Napier Sabre that made it into production before the Jets came along. Any others?


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## wuzak (Aug 29, 2012)

Not sure if you would call the small number of Eagle 22s prodction, or not, but that would be the closest.

The (air-cooled) Rolls-Royce Pennine was only at the prototype stage when cancelled infavour of jets. The same capacity as the R-2800 and max power about the same as the best, most developed, versions of the R-2800.

There was a French H-24 based on Jumo 213 components - but that wasn't production.

There were a couple of prototype V-16s - the Chrysler IV-2220, which had the power and accesories take off from the centre of the crank and the Daimler-Benz DB 609, a V-16 version of the DB 603. The DB 609 had the power take-off from the end of teh crank, like the DB 603. The Chryler IV-2220 was more than 120in (3048mm) long!

Engines like the DB 604 and Vulture could have worked had there been time to properly develop them. The Vulture was in production and in service before it was ready. The DB 604 was cancelled before it got to production - still not sure why.


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## wuzak (Aug 29, 2012)

Forgot about the Allison V-3420. That was in some sort of limited production. Then it wasn't. Then it was. Then it wasn't....

And the Jumo 222.


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## model299 (Aug 29, 2012)

stona said:


> I'm just wondering,it maybe the US Navy had a good reason I'm unaware of. You wouldn't want your matelots drinking the stuff
> 
> Steve



As big as carriers are, they still grapple with the problem of space for "stuff" to this day. By choosing to rely on air cooled engines, they eliminated the problem of tankage, plumbing and such in the handling of glycol. They also eliminated the neccessity of having to keep a stock of spare parts for the cooling systems, the need to set up repair shops for the radiator assemblies, all of the associated hoses, clamps, fittings, etc, and all the tools associated with liquid cooling.

In 2004, I had the priviledge of spending some time aboard the Abraham Lincoln, and the Ronald Reagan (Which had just home ported, still have the t-shirt.) and learned some things about storing "stuff" on a carrier.

All vehicles aboard ship used jetfuel, there is no deisel fuel onboard. We had to make sure our machine (A self propeled deck surface scrubber.) would run on it, as there would be nothing else available. For all of our tests, both at the factory, and on the ship, we ran the vehicle on jet fuel. (and it ran just fine.) 

While on board, I noticed the conspicuous lack of trash recepticals. I asked a Petty Officer about that. He told me that if they have them out, they get filled, and then they have to deal with it. That makes life difficult when you're at sea. That's why I noticed that whilst various crewmember came onboard, they carried no "bags of stuff." The "stuff" they did have was already out of any boxes or bags. Boomboxes, books and whatnot were all carried onboard without any packaging.


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## johnbr (Aug 29, 2012)

On why the db-604 got the axe the designer of it said the RLM said it cost a little more to make then the JU-222.So it and the BMW 802 got killed.


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## wuzak (Aug 29, 2012)

johnbr said:


> On why the db-604 got the axe the designer of it said the RLM said it cost a little more to make then the JU-222.So it and the BMW 802 got killed.



Kind ainteresting if it got axed for costing too much - considering it (probably) worked and the one it was axed for didn't!


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## krieghund (Aug 29, 2012)

davebender said:


> Not necessarily true. Me-109s had a radiator in each wing. They could be individually isolated in case of battle damage. As long as one wing remains undamaged you can limp home.
> 
> Annular radiators are another way to mitigate damage to liquid cooling systems. Hitting an annular radiator means hitting the prop and/or engine. Even without a radiator leak such damage is likely to seize the engine.



It appears to be difficult to isolate one radiator from the other. Another thought is you would be overtaking the plumbing and what would the chance be that a valve failure under normal operating conditions would knock you out as well? From automotive experience why does the bloody thermostat always fail in the closed position? (Ok the car companies need to sell parts)

Another issue with the radiator system is that it is pressurized which helps to evacuate the contents all the faster.


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## krieghund (Aug 30, 2012)

CobberKane said:


> (_Of the early war planes you may compare Bf109E and A6M3, both with about the same power and same speed._ ) The 109 had about 17% more power and 20mph more speed than the zero, so hard to draw conclusions from that.



Actually the better comparison would be the Bf109E (DB601A) to the A6M5 (Sakae 21). Both had similar speeds at critical altitude and horsepower (DB601A = 1005 HP) (Sakae21 = 985 HP)


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## fastmongrel (Aug 30, 2012)

krieghund said:


> From automotive experience why does the bloody thermostat always fail in the closed position? (Ok the car companies need to sell parts)



From my experience Thermostats fail more often in the open position. We often get people coming into the garage at the start of the cold weather saying my heating isnt working, a classic sign of an open thermo. I always ask if they noticed the temp gauge wasnt going up to normal running temp and most people dont even know where the temp needle should be on the dial. Waste of time fitting temp gauges to cars which is probably why some new cars just have a warning light. Even then lots of people keep on driving with the dash flashing like a Xmas tree. Then when the ECU decides its time to shut down the engine and the car gets towed to the garage the owner starts ranting about modern cars having too many electronics despite the fact if it was an older car they would have kept on driving till the engine seized.


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## CobberKane (Aug 30, 2012)

fastmongrel said:


> From my experience Thermostats fail more often in the open position. We often get people coming into the garage at the start of the cold weather saying my heating isnt working, a classic sign of an open thermo. I always ask if they noticed the temp gauge wasnt going up to normal running temp and most people dont even know where the temp needle should be on the dial. Waste of time fitting temp gauges to cars which is probably why some new cars just have a warning light. Even then lots of people keep on driving with the dash flashing like a Xmas tree. Then when the ECU decides its time to shut down the engine and the car gets towed to the garage the owner starts ranting about modern cars having too many electronics despite the fact if it was an older car they would have kept on driving till the engine seized.


 
I'm all for old Cars. I absolutely gaurantee that no pre 1998 Porsche 911 EVER had problems with thermostats radiators or any of that stuff


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## CobberKane (Aug 30, 2012)

Great diagram Krieghung. Illustrates both the vulnerability of a liquid cooled engine and the way in which it allows the designer to pruduce a sleek, low drag profile


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## krieghund (Aug 30, 2012)

CobberKane said:


> Great diagram Krieghung. Illustrates both the vulnerability of a liquid cooled engine and the way in which it allows the designer to pruduce a sleek, low drag profile



I was trying to find a drawing of a late 'G' model but no use.

Anyway all my thermostat problems were seized in the closed position (Two in Fords, One in a Chevy, One in a Mercedes straight 6 and one in a Toyota land cruiser)


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## Timppa (Aug 30, 2012)

wuzak said:


> Corect me if I'm wrong, but the LaGG 3 had susbtantially less power than the La 7.
> 
> And there were some liquid cooled installations that weren't well designed.
> 
> When using leading edge radiators the Tempest I was some 20mph faster than the Tempest II with less power. And a Tempest V with an annular radiator was also about 20mph faster than the Tempest II. One Fury prototype was also fitted with the Sabre with annular radiator, an was about 25mph faster than the Centaurus version. In both those examples the Sabre had a bit more power (about the same difference between Tempest II and standard Tempest V).



Ratio of speed is roughly the ratio of the cubic root of the power, so you can make estimates.

Do you have power and speed curves for Tempest I and this Fury prototype ?


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## stona (Aug 30, 2012)

CobberKane said:


> a sleek, low drag profile



Not words I'd normally assocciate with the Bf 109. I guess the F was about as good as it got 

Cheers

Steve


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## wuzak (Aug 30, 2012)

Timppa said:


> Ratio of speed is roughly the ratio of the cubic root of the power, so you can make estimates.
> 
> Do you have power and speed curves for Tempest I and this Fury prototype ?



No, I do not. 

Just maximum speeds. I believe they are bboth on Wiki.



> LA610 was eventually fitted with a Napier Sabre VII, which was capable of developing 3,400-4,000 hp (2,535-2,983 kW). As a result it became the fastest piston-engined Hawker aircraft, reaching a speed of around 485 mph (780 km/h)



Hawker Sea Fury - Wikipedia, the free encyclopedia



> Elimination of the "chin" radiator did much to improve performance and the Tempest Mark I was the fastest aircraft Hawker had built to that time, attaining a speed of 466 mph (750 km/h).



Hawker Tempest - Wikipedia, the free encyclopedia

I have the Tempest Mk I's speed referenced in on eof my books, power said to be 2400hp from the Sabre IV. Lumsden has the Sabre IV with 2240hp _normal_ power. Can't recall the altitude, but I think it was below 10,000ft. Max in FS gear was 1960hp _normal_ at around 15,000ft, IIRC. Will check when I get home.

Also have a Flight Global document detailing Napier's work on the annular radiator. From memory after a quick glance this morning, the figures were:

Typical radial installation (presumably the Centaurus in the Tempest): 11.5
Standard Chin Radiator: 11.7
Leading Edge Radiator: 11.0
Annular radiator: 6.3

The lower the better. Can't recall what units were being used.

In the breakdown the Leading edge and chin radiator figures included the oil cooler drag, since it was incorporated with the coolant radiator, and extra was added for the radial install. None was added for the annualr installation, but I believe the oil radiator was in the same position as on the radial.

I think it would be fair to say that during the war more effort was expended trying to reduce drag for air-cooled engine than for liquid cooled engines.


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## wuzak (Aug 30, 2012)

napier sabre | tempest | 1948 | 1659 | Flight Archive

And here is the Flight article with the drag table: tempest | 1946 | 1441 | Flight Archive (Not the first page of the article.)


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## buffnut453 (Aug 30, 2012)

renrich said:


> Lindberg chose a radial, air cooled engine for the Altlantic trip because it was lighter and more reliable.



And because he wasn't trying to set a speed record.


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## 61fury (Aug 30, 2012)

wuzak said:


> napier sabre | tempest | 1948 | 1659 | Flight Archive
> 
> And here is the Flight article with the drag table: tempest | 1946 | 1441 | Flight Archive (Not the first page of the article.)



Re that first link Wasn't the FW190 prototype set up like that?


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## krieghund (Aug 31, 2012)

This one?


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## wuzak (Aug 31, 2012)

wuzak said:


> I have the Tempest Mk I's speed referenced in one of my books, power said to be 2400hp from the Sabre IV. Lumsden has the Sabre IV with 2240hp _normal_ power. Can't recall the altitude, but I think it was below 10,000ft. Max in FS gear was 1960hp _normal_ at around 15,000ft, IIRC. Will check when I get home.



Napier Sabre IV: 2240hp @ 8000ft, 4000rpm, +9psi boost, normal power.

Lumsden doesn't have a figure for FS gear. The Sabre V had 1930hp @ 15,750ft, 3650rpm, boost not listed.


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## stona (Sep 10, 2012)

krieghund said:


> It appears to be difficult to isolate one radiator from the other. Another thought is you would be overtaking the plumbing and what would the chance be that a valve failure under normal operating conditions would knock you out as well? From automotive experience why does the bloody thermostat always fail in the closed position? (Ok the car companies need to sell parts)
> 
> Another issue with the radiator system is that it is pressurized which helps to evacuate the contents all the faster.



On the F series exactly such a valve was installed enabling one half of the cooling system to be isolated from the other,hopefully to enable a damaged aircraft to return safely to base. The valves were not installed at the factory but delivered as kits to be fitted by the units.
According to Prien the system worked well but the number of available kits was limited.
The valves were not fitted as standard on the G series,neither were post production kits supplied.
Cheers
Steve


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## Aaron Brooks Wolters (Sep 11, 2012)

Here's one for the air cooled crowd. And a picture.............is worth a thousand words. Oh, and I realize I just kinda stuck this in here so I apologize for that but a friend asked me to post this here so......I did.


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## buffnut453 (Sep 11, 2012)

Was the engine pleased to see you or something?


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## rednev (Sep 12, 2012)

Aaron Brooks Wolters said:


> Here's one for the air cooled crowd. And a picture.............is worth a thousand words.
> In less than a thousand words how prone are monobloc v engines to having a single cylinder fall off compared to radial engines with each cylinder individual bolted to the crankcase ?


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## Shortround6 (Sep 12, 2012)

To get a failure like that you need to have had one of several things happen. Poor maintenance with reused or faulty or over stressed bolts ( how many out of 12-16 of them?). Which in a mono block engine would cause the cylinder block or head to lift depending on location of the bad bolts. Having one end lift a bit may cause several cylinders to stop running properly. 

And/or the cylinder suffered detonation, this can happen even to a properly maintained/built engine. Engine is over boosted for gas/mixture being used and/or over heated. The fuel/air will burn all at once instead of a flame front traveling across the cylinder. This _can_ happen in lean cruise condition. In a mono-block engine instead of the cylinder going up (away from crankcase) the pistons usually went down, in pieces, into the crankcase along with a bent or broken connecting rod. Wither or not the flailing rod punches a hole in the side of the block is up to luck. 

The mono bloc engine is much less prone to having a block come off but but that doesn't mean the mono-block cannot suffer some catastrophic failures.


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## Aaron Brooks Wolters (Sep 18, 2012)

The thing is, if this happens in a mono block, the engine quits. Radials for the most part have a habbit of continuing to run for quite a while after this happens.


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## wuzak (Sep 18, 2012)

Aaron Brooks Wolters said:


> The thing is, if this happens in a mono block, the engine quits. Radials for the most part have a habbit of continuing to run for quite a while after this happens.



Would be extremely unusual for that to happen to a monoblock. Would think that it is still unusual in a radial.


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## Aaron Brooks Wolters (Sep 18, 2012)

I agree.


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## PWR4360-59B (Sep 29, 2012)

I like them all no favorites. But I do like simple logic. A radial is potentially easier to work on in the field. You can blow off a cylinder like the photo and keep running, but it can't be a master cylinder. And cutting the rod off would be recomended as well as blocking off that inlet pipe. Way more involved in working on a bad hole in the LC jobs. Then there is the leak thing, oil is bad enough, don't need something else to leak.


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## stona (Sep 29, 2012)

There is a proposal for a fighter dated 27 July 1938 in Baubeschreibung 187,it was known within the company as Projekt I. This would become the Fw 190. It states that maximum reliability was to be achieved by the avoidance of complicated liquid cooling or hydraulic systems,which experience had shown were often a source of problems.
There was at least a perception that air cooled systems were more reliable,if not less vulnerable.

In October 1939 Heinrich Beauvais came from Rechlin to Bremen to fly the Fw 190 V1. The third sentence of the summary of his report shows what the Luftwaffe thought about the vulnerability of various engine types.

"The view to the rear is superior,and its BMW radial engine is less vulnerable to enemy fire." [compared to Bf 109]

Steve


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## Bizrock (Aug 25, 2018)

Do you guys know which one consume less fuel?


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## swampyankee (Aug 25, 2018)

Bizrock said:


> Do you guys know which one consume less fuel?



The answer is “it depends.”


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## Bizrock (Aug 25, 2018)

swampyankee said:


> The answer is “it depends.”


Depends on what? Horsepower? Design?


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## Shortround6 (Aug 25, 2018)

You have to compare like to like.
Rather obviously a 2000hp air cooled radial needs more fuel than a 1400-1500hp liquid cooled V-12. 

When at cruising speeds the engines are usually within 10% or so of each other in fuel consumed per HP per hour. 
Engines needing a lot of boost use more power to drive the supercharger. 
But even internal friction can play a part at cruising speeds. very roughly 80% of the internal friction comes from the pistons and piston rings sliding in the cylinders. So you have the number, type, and tension of the piston rings and the number of sq ft of cylinder wall scrubbed per unit of time at a given rpm.
Friction also increases with the square of the speed. 

So yeah, there are a LOT of “it depends.”

Too many to pick one type of engine over the other in all (or even most) cases.


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## fastmongrel (Aug 26, 2018)

Post war there were several attempts to improve economy. The CW R3350 turbo compound and the Napier Nomad turbo compound showed how complicated and heavy piston engines become when you try to improve economy without losing power.


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## davparlr (Aug 26, 2018)

Its really difficult to do a comparison without considering the installation. A pretty close comparison can be made with the air cooled P-36(Curtiss Hawk) and the liquid cooled P-40. The Hawk 75A-4 had 1000 hp at 10k and a top speed of 313 mph at 10k, cruised at 262 mph, and weighed 4541lbs empty. The very similar P-40 (no alpha character) had 1040 hp at 10k and a top speed of 357 mph at 10k, cruised at 277 mph, and weighed 5376 lbs. (note: load carried on on gross weight was about 100 lbs more for the P-40). It is apparent that the cleaner liquid fueled P-40 was much faster than the Hawk, but was also 800 heavier, which would have affected climb, though not verifiable. P-40 had no armor, Hawk may have had some.

The verdict of history? Air cooled radial wins. Almost all of the post war heavy hitters, DC-7, Stratocrusiers, Constellation, C-124, Brabazon, used air cooled radials. The Merlins, Griffons, Allisons, all went to collector planes and racers and record setters; autos, boats, planes. In1969, the Navy flew me to New Orleans for a flight physical in an R5D with, you guessed it, air cooled radials.


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## swampyankee (Aug 27, 2018)

Bizrock said:


> Depends on what? Horsepower? Design?



Power, design, installation, operation. Engines for commercial and civil aircraft were mostly air-cooled; cost of operation, including cruise fuel consumption would be highly important. These factors would be less important to air forces, which were the main customers for liquid-cooled engines. 

A complicating factor is that a large portion of the large radials were in multi-engine aircraft, which frequently had a flight engineer, whose job involved monitoring and tweaking engine performance.


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## Clayton Magnet (Aug 27, 2018)

davparlr said:


> The verdict of history? Air cooled radial wins. Almost all of the post war heavy hitters, DC-7, Stratocrusiers, Constellation, C-124, Brabazon, used air cooled radials.


Wouldn't this be better explained by the fact that post war aviation was almost exclusively dominated by American types, and they for the most part stopped developing in-line aero engines after the Allison? Aircraft piston engine development kinda leveled off and stopped in the 1950's, so whatever was popular then is what tended to stick. The vast majority of aircraft with piston engines today use American air-cooled designs, without any real advancements since the 40's or 50's. A O-360 in a brand new Piper or Cessna today is about the same thing as an O-360 from 1955.

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## Clayton Magnet (Aug 27, 2018)

I don't think anyone would argue that in general, air cooled engines are more damage tolerant, but the degree of which gets blown out of proportion. Was the Corsair not known to have a "glass jaw", in the form of oil cooler placement? And what kind of blow-torch effect would a punctured component in a P-47's elaborate turbo ducting cause?


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## swampyankee (Aug 27, 2018)

Clayton Magnet said:


> Wouldn't this be better explained by the fact that post war aviation was almost exclusively dominated by American types, and they for the most part stopped developing in-line aero engines after the Allison? Aircraft piston engine development kinda leveled off and stopped in the 1950's, so whatever was popular then is what tended to stick. The vast majority of aircraft with piston engines today use American air-cooled designs, without any real advancements since the 40's or 50's. A O-360 in a brand new Piper or Cessna today is about the same thing as an O-360 from 1955.



US dominance, especially in transport aircraft, is certainly one factor, but the USSR followed the same trend.


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## KiwiBiggles (Aug 27, 2018)

With all the anecdotes in this thread about P-47s, F6Fs etc making it home having lost a pot in combat, it has to be asked, was the R2800 especially prone to losing cylinders due to combat damage? Maybe the lack of stories about Spitfires coming home with pistons hanging out the top of the engine just reflects that the Merlin didn't lose cylinders.


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## BiffF15 (Aug 27, 2018)

Or that they didn’t make it home when they did.

I have a bud who used to fly at Stallion 51. He lost a cylinder and ended up landing immediately at Avon Park. Obviously the prudent thing to do due to fear of losing the engine and or the aircraft.

Cheers,
Biff


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## Shortround6 (Aug 27, 2018)

An air cooled engine, the vast majority of the time, used separate cylinders. You can have one shot off or blow one off with detonation (or crappy maintenance?
and the rest of the engine is relatively unaffected (valve trains, intake and exhaust manifolds, cooling for the most part). Granted you are losing oil by the bucket and the engine is hardly running smooth/even which does not bode well for long term (15-20 minutes?) life.

Liquid cooled V-12s used 6 cylinders to a block, you aren't going to lose *one* cylinder. A "Hit" that takes out one cylinder on a radial is going to put a really big hole in the cooling system, it may take out part of the oil system, If it hits in the valve area it may take out the camshaft which can stop several cylinders (up to six) or maybe just a few rockers on adjacent cylinders (they are closer together than on a radial). IF the cylinder head starts to lift for any reason you may lose compression in several cylinders. 

One wonders at the resistance to combat damage of _other_ radials. Excluding the French Hispano Suiza radials (which were known to lose their propellers with absolutely no help from the enemy.) did the Wright R-2600 have a reputation for getting back with missing cylinders? Or the Hercules? 
Please note that the Armstrong Siddeley Tiger in early Whitleys was banned from overwater flights before the shooting even started. Gnome Rhone engines and their derivatives (Russian M-88 and Italian Piaggio ) had no center bearing on the two throw crank so their ability to run for very long with a cylinder and piston gone is rather suspect. 

I am also sure that plenty of R-2800s didn't make it home after taking hits to the engine.

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## fastmongrel (Aug 28, 2018)

The Fairey Swordfish was also known for coming back with its Bristol Pegasus missing a pot. Mind the Peggy made such a noisy clatter I bet sometimes the crew didnt notice they had an 8 cylinder

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## RCAFson (Aug 31, 2018)

Some PR for RR:

_View: https://www.bbc.com/news/av/uk-england-derbyshire-45220185/how-ernest-hives-merlin-engine-powered-the-spitfire_

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## Reluctant Poster (Sep 9, 2018)

The USN did a study of "aircraft loss and damage in relation to components affected by Japanese fire". The table I have attached is from the Rand Corporation Study "Aircraft Vulnerability in World War II" dated 12 July 1950. 
There is a lot of fascinating reading in this document. I was surprised to learn, as Clayton Magnet mentioned, that the Corsair did have a "glass jaw" with a higher loss to hit ratio than any other single engine navy aircraft.
A lot of it is as expected 
The B-24 was more vulnerable than the B-17
Don't get hit by 20 mm cannon
Aircraft are deadlier than AA
Bombing Germany was much more dangerous than bombing France
The P-47 was much more resistant to AA than the other 2 but the P-51 is only a bit worse than the P-38
The P-47 was somewhat better than the P-51 in air to air but the P-38 was significantly worse
The B-26 was a lot tougher than the B-25
The most vulnerable part of a heavy bomber was the engines. Sadly a lot of B-17s were lost because the emergency prop feathering oil reserve was deleted to save weight
" With only 10% of P-38's returning after one engine was disabled , it is evident that in most cases the disablement of either engine led to the loss of the aircraft. Thus contrary to what might be expected , the second engine of the P-38 probably increased the vulnerability of the airplane."

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## swampyankee (Sep 9, 2018)

I think it's likely that a twin-engined fighter that loses one engine in combat is going to be _extremely _vulnerable, as the aircraft's performance is severely degraded. In addition, since early P-38s also only had a generator on one engine, losing that engine means that little things like radios and radio navigation equipment are running off battery, which may not last quite long enough.

Even with aircraft with liquid-cooled engines, details of the cooling system design can make a huge difference. An aircraft with a nose-mounted radiator, like the V-12 FW190s and the P-40, are less likely to suffer damage to the cooling system from fighters, at least, than an aircraft with a radiator mounted in the wings or in the rear fuselage, first simply because fighters are going to be attacked by other fighters most often from behind, and secondly, because the nose-mounted radiator will have much shorter coolant lines.


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## Shortround6 (Sep 10, 2018)

On the P-38s the propellers were electric which means on the early ones (and early means somewhere into the 'J's) if the battery failed after the engine with generator was lost you could no longer adjust the pitch of the prop on the remaining engine. A long flight home could mean turning off the radios and other stuff (panel lights?) and only turning them back on periodically to save the battery. Electricity was also needed for the aux fuel pumps, turbo regulators, oil cooler and intercooler exit flaps (on the later P-38s) pitot tube heating, and instruments. 

There were instances in the CBI theater of P-38s making return flights of 600 miles on one engine. However there were only a few squadrons in the theater using P-38s so perhaps the number of times this was done is not statistically significant ?


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## Clayton Magnet (Sep 10, 2018)

I used to work on pipeline monitoring aircraft, specifically Piper Navajo's, and it was known that losing an engine at that altitude meant that the other one would just carry you to the crash site. So having two engines just meant we were twice as likely to crash


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## PWR4360-59B (Sep 11, 2018)

Clayton Magnet said:


> I used to work on pipeline monitoring aircraft, specifically Piper Navajo's, and it was known that losing an engine at that altitude meant that the other one would just carry you to the crash site. So having two engines just meant we were twice as likely to crash


Sure glad the FAA doesn't agree with you, if they did all the jet passenger aircraft would have 4 engines again.


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## swampyankee (Sep 11, 2018)

PWR4360-59B said:


> Sure glad the FAA doesn't agree with you, if they did all the jet passenger aircraft would have 4 engines again.



Or one 

The single engine rate of climb rules for light twins are quite a bit laxer than those for largish jet commercial aircraft.

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## Clayton Magnet (Sep 11, 2018)

PWR4360-59B said:


> if they did all the jet passenger aircraft would have 4 engines again.


Jet passenger aircraft generally don't operate below the tops of trees, looking for gas leaks in pipelines. A Navajo that loses an engine at that altitude, while in a 30 degree bank is going to crash.


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## PWR4360-59B (Sep 13, 2018)

So would almost any plane. In a 30 degree bank at 50 feet off the ground. And besides that sounds like a job for a Cessna 150 not a fast twin.


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## Clayton Magnet (Sep 13, 2018)

Agreed. That's why the company reverted to modified 172's for the role. Far better downward visibility, and far lower maintenance costs, even with the extra fuel tank STC's. But somebody had the brilliant revelation that a twin would be safer. And they then selected an aircraft with props swinging in the same direction, so if you lose the right engine, you lose rudder authority.

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## swampyankee (Sep 13, 2018)

Clayton Magnet said:


> Agreed. That's why the company reverted to modified 172's for the role. Far better downward visibility, and far lower maintenance costs, even with the extra fuel tank STC's. But somebody had the brilliant revelation that a twin would be safer. And they then selected an aircraft with props swinging in the same direction, so if you lose the right engine, you lose rudder authority.




Quite few modern twins have handed propellers. Lack of rudder authority is because the fin and rudder were too small.


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## PWR4360-59B (Sep 13, 2018)

I have flown only single engine stuff, but I do know when you have an engine out on a twin you also pull out the running engine as well, back to low to no power and recover then slowly add the power. And not doing so is why an engine out on a twin can bring it down.


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## swampyankee (Sep 13, 2018)

PWR4360-59B said:


> I have flown only single engine stuff, but I do know when you have an engine out on a twin you also pull out the running engine as well, back to low to no power and recover then slowly add the power. And not doing so is why an engine out on a twin can bring it down.




Some time ago, when I was trying to get a PPL (and before I found that migraines are disqualifying), I found it written that light twins had higher accident rates than comparable singles.

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## gumbyk (Sep 13, 2018)

PWR4360-59B said:


> Sure glad the FAA doesn't agree with you, if they did all the jet passenger aircraft would have 4 engines again.


You don't seem to understand the difference in reliability between turbines and piston engines...


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## gumbyk (Sep 13, 2018)

Clayton Magnet said:


> Agreed. That's why the company reverted to modified 172's for the role. Far better downward visibility, and far lower maintenance costs, even with the extra fuel tank STC's. But somebody had the brilliant revelation that a twin would be safer. And they then selected an aircraft with props swinging in the same direction, so if you lose the right engine, you lose rudder authority.


That's what Vmca is for; above this you have enough rudder authority, below it you don't. You may not have enough power available to maintain height, and if you're low, the natural instinct is to try to maintain height, and the speed washes off.


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## PWR4360-59B (Sep 14, 2018)

gumbyk said:


> You don't seem to understand the difference in reliability between turbines and piston engines...


I just find it so funny that just because I won't agree with something, I am then told I don't understand something. What makes a turbine and a piston engine different is one of them can be assembled by complete idiots and work just fine where the other needs someone with more technical abilities to assemble it. And that is one of the main reasons for the reliability issues. Actually the turbine parts are under way more stress than the recip parts and if they were not replaced on a certain schedule then turbine reliability would not be so good. I've heard the turbines have high TBO's because the critical parts changes are just considered normal maintenance.


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## Shortround6 (Sep 14, 2018)

PWR4360-59B said:


> I just find it so funny that just because I won't agree with something, I am then told I don't understand something. What makes a turbine and a piston engine different is one of them can be assembled by complete idiots and work just fine where the other needs someone with more technical abilities to assemble it. And that is one of the main reasons for the reliability issues. Actually the turbine parts are under way more stress than the recip parts and if they were not replaced on a certain schedule then turbine reliability would not be so good. _I've heard the turbines have high TBO's because the critical parts changes are just considered normal maintenance_.



A lot of what you _seem_ to believe sounds like it is based off of things you "heard". 
Not read or to found in maintenance manuals or factory maintenance publications /notices. People are objecting because a lot of what you "heard" runs counter to what most everybody else is hearing. 

A generic manual for the P & W PT6 engine can be found here: http://www.caijets.com/pdf/KnowYourPT6A.pdf
specific manuals for individual engine models may be harder to come by but this seems to have some decent information. 

I would note that a some Lycoming and Continental flat fours and sixes only make to their suggested engine lives because "_critical parts changes are just considered normal maintenance". _Like changing cylinders on an individual basis if they develop cracks before (hundreds of hours before) the lower end reaches it's overhaul life limit. Since large radials have been out of normal service for decades getting information on engine life may be a bit difficult leaving us with what was done in the 40s/50s/60s.

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## Clayton Magnet (Sep 15, 2018)

Shortround6 said:


> A generic manual for the P & W PT6 engine can be found here:


Don't forget the "C" in P&WC, its the most important part

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## gumbyk (Sep 18, 2018)

Shortround6 said:


> I would note that a some Lycoming and Continental flat fours and sixes only make to their suggested engine lives because "_critical parts changes are just considered normal maintenance". _Like changing cylinders on an individual basis if they develop cracks before (hundreds of hours before) the lower end reaches it's overhaul life limit.


The Lycoming IO-360 platform is fairly bomb-proof now - 4,000 hrs TBO isn't uncommon (without cylinder changes) if its de-rated to 160-180 hp.

There isn't a modern piston engine (that I'm aware of) that is able to be run 'on condition' like turbo-shaft type engines are. The Honeywell LTS series of engines had the lowest component life of 5,600 hours from memory, it was all higher than that for everything else.



PWR4360-59B said:


> What makes a turbine and a piston engine different is one of them can be assembled by complete idiots and work just fine where the other needs someone with more technical abilities to assemble it.


 Have you ever been to or worked in an engine overhaul shop? I know a lot of people who would disagree with that insult you just threw out there.

Please, back up 'what you heard' with some figures, even of they're from memory.

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## PWR4360-59B (Sep 18, 2018)

The recip needs technical people to assemble it. Turbines are simple assembly, just tons of repetitive parts to install, like turbine blades and such.
Non tech types can assemble the turbines much easier than complicated old radial engines. My young grand kids could assemble the blades in a turbine, and probably better than the assembly line workers. 
Engine shop? Yes not aircraft though.


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## wuzak (Sep 18, 2018)

PWR4360-59B said:


> The recip needs technical people to assemble it. Turbines are simple assembly, just tons of repetitive parts to install, like turbine blades and such.



So, piston engines are better because they are more complicated and harder to put together?




PWR4360-59B said:


> Non tech types can assemble the turbines much easier than complicated old radial engines. My young grand kids could assemble the blades in a turbine, and probably better than the assembly line workers.



Ignoring the many thousands of people who have built up engines in their back yards, many of whom have done so with good instruction manuals rather than deep technical understanding.

Ease of assembly is a result of good engineering.


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## gumbyk (Sep 18, 2018)

PWR4360-59B said:


> The recip needs technical people to assemble it. Turbines are simple assembly, just tons of repetitive parts to install, like turbine blades and such.
> Non tech types can assemble the turbines much easier than complicated old radial engines. My young grand kids could assemble the blades in a turbine, and probably better than the assembly line workers.
> Engine shop? Yes not aircraft though.


BWAHAHAHAHAAA!!!!

REALLY?

Sorry, you just showed your ignorance....

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## Ascent (Sep 19, 2018)

I spent five years in the engine bay at RAF Marham doing engine strip and build, nice to know that the RAF could have saved a fortune on mine and my colleagues training.

Gas turbine maintenance is a very technical job despite what you may think.

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## fastmongrel (Sep 19, 2018)

Ascent said:


> I spent five years in the engine bay at RAF Marham doing engine strip and build, nice to know that the RAF could have saved a fortune on mine and my colleagues training.
> 
> Gas turbine maintenance is a very technical job despite what you may think.



But all you need is a child to assemble a turbine. It's just like building Lego but with bigger hammers

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## soulezoo (Sep 19, 2018)

PWR4360-59B said:


> The recip needs technical people to assemble it. Turbines are simple assembly, just tons of repetitive parts to install, like turbine blades and such.
> Non tech types can assemble the turbines much easier than complicated old radial engines. My young grand kids could assemble the blades in a turbine, and probably better than the assembly line workers.
> Engine shop? Yes not aircraft though.



Having worked on both Turbines (TF-33, CF6-50C2, J69) as well as light aircraft recip (A & P licensed mech), I know what it takes for both. I find this post insulting and ignorant. (On edit, I am thinking he probably thinks blade blending is what you do to add wheat grass to your margarita)

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## soulezoo (Sep 19, 2018)

fastmongrel said:


> But all you need is a child to assemble a turbine. It's just like building Lego but with bigger hammers


You may appreciate this...
On the CF6-50C2, there is a part colloquially referred to as the "motorcycle engine" (resembles a cylinder from an old Triumph or Norton) amongst other things. This "motorcycle engine" is an integral part of the operation of the thrust reversers. In another parallel universe, a looong time ago, when in a hostile environment a long way from home, I had to resort to a hammer to unstick this damned thing so we could get the hell out of Dodge. Definitely not a tech manual moment I was proud of. But we got out.


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## Ascent (Sep 19, 2018)

fastmongrel said:


> But all you need is a child to assemble a turbine. It's just like building Lego but with bigger hammers



To be fair children with hammers is probably a good description of half the lineys I worked with.

(For the non RAF types, lineys is the nickname for the flight line mechanics)


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## soulezoo (Sep 19, 2018)

Ascent said:


> To be fair children with hammers is probably a good description of half the lineys I worked with.
> 
> (For the non RAF types, lineys is the nickname for the flight line mechanics)



Glad you spelled that out. I first read that as "Limeys". I was thinking, "well who else would you expect to be there aside from Limeys?" LOL sorry, no disrespect intended.


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## PWR4360-59B (Sep 20, 2018)

Truth always hurts.


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## MiTasol (Sep 20, 2018)

Aaron Brooks Wolters said:


> Here's one for the air cooled crowd. And a picture.............is worth a thousand words. Oh, and I realize I just kinda stuck this in here so I apologize for that but a friend asked me to post this here so......I did.



Good photoshop job. It is a spare cylinder still with the transport blank and desiccant plugs in it


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## MiTasol (Sep 20, 2018)

Aaron Brooks Wolters said:


> The thing is, if this happens in a mono block, the engine quits. Radials for the most part have a habbit of continuing to run for quite a while after this happens.



Except that on a radial when an articulating rod breaks the end attached to the crank often flails around and beats the sh*t out of the inside of the crankcase and the disconnected induction tube allows large volumes of fuel air mixture to vent to atmosphere totally disrupting the mixture ratio -- one or both causing the engine to stop instantly. And yes I do know from first hand experience.


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## MiTasol (Sep 20, 2018)

KiwiBiggles said:


> With all the anecdotes in this thread about P-47s, F6Fs etc making it home having lost a pot in combat, it has to be asked, was the R2800 especially prone to losing cylinders due to combat damage? Maybe the lack of stories about Spitfires coming home with pistons hanging out the top of the engine just reflects that the Merlin didn't lose cylinders.



Losing a pot does not mean it became totally disconnected like shown in the Photoshop picture. Usually it means the head disconnected from the barrel due to damage or cracking or one of the pushrod ears broke off through the rocker arm pivot bolt holes due due to damage, cracking or over-torquing the rocker shaft bolt.


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## MiTasol (Sep 20, 2018)

PWR4360-59B said:


> The recip needs technical people to assemble it. Turbines are simple assembly, just tons of repetitive parts to install, like turbine blades and such.
> Non tech types can assemble the turbines much easier than complicated old radial engines. My young grand kids could assemble the blades in a turbine, and probably better than the assembly line workers.
> Engine shop? Yes not aircraft though.



Are your grand kids watchmakers then?

Turbines depend on extremely close tolerances both dimensionally and mass wise (to obtain the dynamic balance needed). Far tighter tolerances than on piston engines.

On any of the variable stator angle engines just one stator off angle will cause the engine to self destruct within seconds. Clearances are so critical that many of the bigger engines have manifolds around the outside of the turbine spraying "cold" (as in 200-400C) compressor air over the outside of the turbine case to shrink it to maintain blade tip clearances at the required dimensions.

On piston engines the connecting, master and articulating rods and the piston weights can vary considerably inside any single engine. The weight of the cylinders and all their mechanisms have no weight limits.

For many years the Australian Civil Aviation Safety Authority allowed the PT-6 turbine engines to run 12,000 hours between overhauls - well beyond what Pratt and Whitney recommended and far beyond what any piston engine is capable of. I am not aware of any failing but the overhaul cost would have been horrendous as erosion and cracking of internal parts would have put many of those parts outside repairable limits.


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## gumbyk (Sep 20, 2018)

PWR4360-59B said:


> Truth always hurts.


Huh?


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## KiwiBiggles (Sep 20, 2018)

MiTasol said:


> Losing a pot does not mean it became totally disconnected like shown in the Photoshop picture. Usually it means the head disconnected from the barrel due to damage or cracking or one of the pushrod ears broke off through the rocker arm pivot bolt holes due due to damage, cracking or over-torquing the rocker shaft bolt.


I was indulging in a little hyperbole. I didn't really visualise anything like the Photoshopped image of the cylinder poking out the top of the cowling.

But I think my facetious point might have a bit of unexpected depth to it: the anecdotes about R-2800-powered fighters dragging themselves home with a cylinder or two missing in action might well reflect that that radials in general, with their distinct cylinders, are more prone to this kind of damage than monobloc V12s. Maybe we don't get the same heroic stories about Spitfires, P-51s, P-38s etc because that kind of damage just didn't happen to their engines.


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## gumbyk (Sep 20, 2018)

KiwiBiggles said:


> I was indulging in a little hyperbole. I didn't really visualise anything like the Photoshopped image of the cylinder poking out the top of the cowling.
> 
> But I think my facetious point might have a bit of unexpected depth to it: the anecdotes about R-2800-powered fighters dragging themselves home with a cylinder or two missing in action might well reflect that that radials in general, with their distinct cylinders, are more prone to this kind of damage than monobloc V12s. Maybe we don't get the same heroic stories about Spitfires, P-51s, P-38s etc because that kind of damage just didn't happen to their engines.


Yeah, its kind of hard to lose one cylinder when they're all solidly connected together...


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## KiwiBiggles (Sep 20, 2018)

gumbyk said:


> Yeah, its kind of hard to lose one cylinder when they're all solidly connected together...


And this should be considered one of the advantages of a inline.


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## Shortround6 (Sep 20, 2018)

Or disadvantage. If one cylinder lets go does it take one or more adjacent cylinders with it?

Granted it is less likely but if the detontaion forces (not combat damage) are enough to blow a cylinder off a crankcase (or head off a cylinder) on the radial what happens to the bolts holding down the head or cylinder block on the inline? The cylinder head (or parts) might not depart the airplane but head gasket (or equivalent) may no longer seal well enough to get any useable power from the affected cylinder and/or one or two adjacent ones? 
A flailing rod on a a radial may very well chew up the crankcase. On an inline a flailing rod can punch holes in the cooling jacket, or bottom cover/dry sump. 
The radial _might_ last as long as the oil (losing quarts per minute). but the Inline is not going very far either if the coolant is leaking out and/or it is losing oil in large quantities. 

I am fully willing to accept that many radials did NOT make it home with cylinders missing. But inlines had a few problems of their own.

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## Clayton Magnet (Sep 21, 2018)

How long would an R-2800 oil system hold out with a jug missing? The large drop in oil pressure and continuous flow overboard must have locked up the engine quite quickly. Radials being more dependent on oil for cooling than a liquid cooled counterpart


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## BAGTIC (Sep 21, 2018)

I have read that radials leaked more oil, were slower to start up and warm up.
Liquid cooled engines with ebullient cooling systems could save several horsepower by eliminating water pumps while providing more uniform engine cooling.


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## gumbyk (Sep 21, 2018)

BAGTIC said:


> I have read that radials leaked more oil, were slower to start up and warm up.
> Liquid cooled engines with ebullient cooling systems could save several horsepower by eliminating water pumps while providing more uniform engine cooling.


The oil is because half of their cylinders are upside down. The inline Gipsy series engines (in-line, inverted) always have oil under them. Not sure what an inverted liquid-cooled engine is like.
The warming up issue is due to having air-cooling. Close the cowl flaps and they seem to warm up reasonably quickly.


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## jetcal1 (Sep 21, 2018)

PWR4360-59B said:


> Truth always hurts.


People used to think the earth was flat too.


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## Shortround6 (Sep 21, 2018)

Clayton Magnet said:


> How long would an R-2800 oil system hold out with a jug missing? The large drop in oil pressure and continuous flow overboard must have locked up the engine quite quickly. Radials being more dependent on oil for cooling than a liquid cooled counterpart



That may depend on where in the mission the damage occured. It may depend on how much oil they put in to begin with. A P-47 could hold up to 28 gallons of oil. oil was used during the flight.
Early B-26s could hold 42.5 gallons per engine. F4us held either 20 gal or 24 gal and F6Fs held 19 gal max. 

Coming back after a long flight and a fair amount of the oil could be gone. Getting hit early and you could loose a few quarts a minute from a P-47 and still fly for 20 minutes or more before the bearings were in any danger. At a low power setting (about as low as the plane would stay in the air to minimize the vibration?) the engine might last a number of minutes at below normal oil pressure before it seized. 

It was done a few times. How many more times I don't know, but even the R-1830s had a reputation for taking abuse and lasting, several B-24s made it home with one or more engines dead and the remainder running in the red for hours.

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## PWR4360-59B (Sep 22, 2018)

Oil pressure ? In the old days recip engines ran with zero oil pressure, and you'd be surprised how long even the more modern ones can. Oh and there are still many piston engines built today that don't even have an oil pump or a pressurized lube system.


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## Shortround6 (Sep 22, 2018)

PWR4360-59B said:


> Oil pressure ? In the old days recip engines ran with zero oil pressure, and you'd be surprised how long even the more modern ones can. Oh and there are still many piston engines built today that don't even have an oil pump or a pressurized lube system.



Ok, list the ones that don't use oil pumps or pressurised lube systems that are not used in lawn equipment or model airplanes.
Ford gave up on splash lubrication with the Model T in 1927.


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## PWR4360-59B (Sep 22, 2018)

Shortround6 said:


> Ok, list the ones that don't use oil pumps or pressurised lube systems that are not used in lawn equipment or model airplanes.
> Ford gave up on splash lubrication with the Model T in 1927.


Engines are engines. I did not specify a certain application.


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## PWR4360-59B (Sep 22, 2018)

jetcal1 said:


> People used to think the earth was flat too.


So what? If your a person or entity that was only about 10 microns in size it would look that way, everything is relative, besides what does this have to do with engines?


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## Shortround6 (Sep 22, 2018)

PWR4360-59B said:


> Engines are engines. I did not specify a certain application.


No you didn't.
Like a lot of your posts. Vague references that you want us to look up or puzzle out rather than give links. 
And applications do matter in order to do that "proper engineering" you talk about. A low stress, low rpm engine can get away without pressure lubrication much easier than a high stress and/or high rpm engine. 
Type of bearing material can make a difference too. 
Engines are not engines unless you think you can stick 12 Briggs and Stratton lawn mower cylinders/pistons on a common crankshaft/crankcase and beat a Ferrari.

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## DerAdlerIstGelandet (Sep 23, 2018)

PWR4360-59B said:


> The recip needs technical people to assemble it. Turbines are simple assembly, just tons of repetitive parts to install, like turbine blades and such.
> Non tech types can assemble the turbines much easier than complicated old radial engines. My young grand kids could assemble the blades in a turbine, and probably better than the assembly line workers.
> Engine shop? Yes not aircraft though.



Have you ever worked a turbine? Put one back together? It too takes someone with technical expertise. Tolerances are very precise. Not putting something exactly as it should can be catastropic.

It’s not as simple as you pretend it is. What do I know though? I’m just an A&P who has worked on hundreds of PT6’s and T700’s. No skill required at all...

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## DerAdlerIstGelandet (Sep 23, 2018)

gumbyk said:


> Huh?



I think he is referring to the fact he stumbled into something he is not getting out of.


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## MiTasol (Sep 23, 2018)

PWR4360-59B said:


> Oil pressure ? In the old days recip engines ran with zero oil pressure, and you'd be surprised how long even the more modern ones can. Oh and there are still many piston engines built today that don't even have an oil pump or a pressurized lube system.



I am aware of any AIRCRAFT engines with no pressure lube systems although most rotary engines used piston pumps and the lubrication was total loss. Many older engines had pressure lube for the crank-case but grease (Bristol Mercury and Pegasus) or splash (some deH engines) for the valve gear. Interestingly the Bristol Pegasus IIM3 manual requires the valve gear to be greased every three hours yet the Sunderland operated on 14 hour patrols.

Non aircraft engines are not of interest to the majority on this site.


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## fastmongrel (Sep 23, 2018)

Strange that all those engine designers wasted so much time on oil pumps when all they had to do was fill the crankcase with Whale oil.


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## fastmongrel (Sep 23, 2018)

DerAdlerIstGelandet said:


> Have you ever worked a turbine? Put one back together? It too takes someone with technical expertise. Tolerances are very precise. Not putting something exactly as it should can be catastropic.
> 
> It’s not as simple as you pretend it is. What do I know though? I’m just an A&P who has worked on hundreds of PT6’s and T700’s. No skill required at all...



I bet your tool cabinet only has three things in it. A big hammer a medium hammer and a small precision hammer.


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## DerAdlerIstGelandet (Sep 23, 2018)

fastmongrel said:


> I bet your tool cabinet only has three things in it. A big hammer a medium hammer and a small precision hammer.



And a big orange rubber mallet.

It’s a good thing I no longer work on the floor, and now work in safety. No skills and all, you know...

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## Ascent (Sep 23, 2018)

PWR4360-59B said:


> Oil pressure ? In the old days recip engines ran with zero oil pressure, and you'd be surprised how long even the more modern ones can. Oh and there are still many piston engines built today that don't even have an oil pump or a pressurized lube system.



I shall consider this statement, think about what you said about gas turbines and how that compares to my personal experience and give it as much credence as it deserves.

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## jetcal1 (Sep 23, 2018)

PWR4360-59B said:


> So what? If your a person or entity that was only about 10 microns in size it would look that way, everything is relative, besides what does this have to do with engines?



With an extensive background on both turbine and recip engines and over 45 years experience of wrenching, testcell operations and test-set development. I just can't help but find your comments amusing.

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## PWR4360-59B (Sep 24, 2018)

jetcal1 said:


> With an extensive background on both turbine and recip engines and over 45 years experience of wrenching, testcell operations and test-set development. I just can't help but find your comments amusing.


Yeah thats what happens when a guy that is not a huge fan of jets joins in, sorry, I know playing with the various rotating blades is a tedious thing and that is why my simplification of it. I have worked on jets in a limited sort of way.


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## jetcal1 (Sep 24, 2018)

PWR4360-59B said:


> Yeah thats what happens when a guy that is not a huge fan of jets joins in, sorry, I know playing with the various rotating blades is a tedious thing and that is why my simplification of it. I have worked on jets in a limited sort of way.



Turbines are actually far more fun to troubleshoot when they're ailing than a piston engine. (Especially hot-streak ignition afterburner problems.)


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## gumbyk (Sep 25, 2018)

PWR4360-59B said:


> Oil pressure ? In the old days recip engines ran with zero oil pressure, and you'd be surprised how long even the more modern ones can. Oh and there are still many piston engines built today that don't even have an oil pump or a pressurized lube system.


Maybe, but there were very few propellers that ran without oil pressure...


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## jetcal1 (Sep 25, 2018)

fastmongrel said:


> Strange that all those engine designers wasted so much time on oil pumps when all they had to do was fill the crankcase with Whale oil.



R4360 must be referring to one of the new automotive engines. In fact some engines can even be adapted to run this Engine Oil Bypass Kit:
"Modern synthetic oil is very expensive - so why run the risk of getting it dirty by running it through your motor block? KaleCoAuto bypass kit comes with everything you need to run the oil around your motor block where it will do more good. Oil runs cooler, and as a result, there may be horsepower gains!"
Engine Oil Bypass Kit - $93.60 : KaleCoAuto.com, Your home for the rare, unusual, and hard to find auto parts.

Source: Kalecoauto.com

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## gumbyk (Sep 25, 2018)

jetcal1 said:


> R4360 must be referring to one of the new automotive engines. In fact some engines can even be adapted to run this Engine Oil Bypass Kit:
> "Modern synthetic oil is very expensive - so why run the risk of getting it dirty by running it through your motor block? KaleCoAuto bypass kit comes with everything you need to run the oil around your motor block where it will do more good. Oil runs cooler, and as a result, there may be horsepower gains!"
> Engine Oil Bypass Kit - $93.60 : KaleCoAuto.com, Your home for the rare, unusual, and hard to find auto parts.
> 
> Source: Kalecoauto.com


I see they have left handed screw drivers and sky hooks as well...


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## jetcal1 (Sep 26, 2018)

gumbyk said:


> I see they have left handed screw drivers and sky hooks as well...


Yes, did you notice that the driver was metric as well?
We had a Beech 65 with rather weak strobes, but we were able to get a STC to use the KaleCo synthetic blinker fluid after the customer's SMS Manager approved it for installation. (We had to go from a aluminum reservoir to a composite set-up since the KaleCo fluid is corrosive.)
We're now getting faster, stronger, harder blinks from the previously marginal strobes. The whole upgrade was less expensive then a LED conversion.

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## DerAdlerIstGelandet (Nov 30, 2018)

I needed a good laugh this morning, so I came to this thread.


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## fliger747 (Dec 1, 2018)

Years ago I worked on Alaska's North slow blowing things up with an explosives guy. He has been a P-47 pilot in the ETO. Based in France they would go on search and destroy missions, a favorite was trains. Hitting an engine gave a very satisfying steam explosion. However the Germans had FLAK on the flatcars and would shoot back. The R2800 was a comforting bit of metal to have in front when the teens ball sized tracers were going by. 

Returning from a Mission it was running a bit rough. Pulling up to the hard stand and climbing out he is met by the crew chief, she's missing Sarge, I'll be over at the mess tent. Sarge comes by 5 mins later, yep she's miss'n, miss'n a jug... 

I have a lot of time behind R985's, I have several friends come back with an eight banger...

I this part of the world one can still hear the musical rumble of the R2800 on a regular basis. Leave the radiator flaps closed on a radiator and it will overheat too!


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## fliger747 (Dec 5, 2018)

In 10,000 hours as a 747 Captain I puked 4 engines. None was a catastrophic failure, though the "fire" on climb out from JFK on a rainy night did catch our attention. Haven't puked any of the supposedly less reliable piston pounders yet. 

Interesting to note that in the post war commercial environment, the radial soon edged out any competition. I have friends who still fly DC6 and C46 in commercial operation! Handy you can just change out that jug that you blew the top off of.

Cheers!


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