Aces High Bulletin Board
General Forums => Aces High General Discussion => Topic started by: GtoRA2 on May 25, 2004, 11:32:21 AM
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Did real aircraft engines overheat at military power?
I have read a lot about WW2 planes. I have read the Graham White book on the R2800, and Allied aircraft engines. I am reading through Vees for victory, a book on just the V1710, and nothing in any of those books mentions the engines overheating at Military power.
The Vees for Victory book talks about how the V1710 had to run for 100plus hours at military for it to be accepted by the Army Air corp.
I see a lot of guys pushing for engine overheating, and I would like to know if this is a myth and people like it cause of IL2 or was it a real problem? I can see other reasons for not running around at Military all the time, mostly to do with how it would affect the range of the plane.
Does anyone have a source that talks about his stuff? I am more then willing to buy a book to read about it, web sites are good as well, as long as they have some historic data to back the claims up.
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Do you know you have 3 the same threads up?
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if he didnt before he knows now...
as for the question probably not...even if there was a danger of it higher altitudes that planes flew at are usually cold so that would help maintain a lower engine temp.
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I would like to see if there is specific engines that maybe had heat issues. Like maybe the 109 had radiators that were two small etc.
I would also like to hear with the whole thing came from and if it is has any historic background.
Another reason I can think is wear and tear on the Engine, running at military had to cause more?
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You could do a search on the forum, this one and at least the AC forum, there's lots of material there.
Basically there are some real conditions that aren't reproducible in the game, like living only once, ressources shortage etc.
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Moot has there been a thread just talking about engine heat? I do not care about the only dying once stuff etc.
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at least a few yeah.
What I mean is ingame you are just a player taking up a plane that doesn't have any price tag, no ground crew taking care of it, one lifetime (the sortie), not a full physics modeling (not every fuel and oil lines etc is there to be damaged or fail etc), etc etc
Far as I know, anything will overheat in the right conditions, and in AH (all) the conditions aren't really there, at least not the way they were in reality. I could guess that FB models things realistically, but accurately, I'm not sure of.
I can't quantify, but you might be able to, reading those old (for the most part) threads.
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I have a table with range data for the Mosquito with Boost at +14lbs. That seems to indicate to me that it could run at +14lbs (MIL power) for extended times.
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I figured that would be the case for most WW2 planes.
I still can't find anythreads that talk about Engine heat over long periods, I think it is mostly a game compromise I would rather not see.
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Any gasoline engine can over heat.
But i would think the higher you go and the thinner colder air would prolong the heating process.
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Let me clairify that the Mosquito in AH seems to be powered by Merlin 21 or 23 engines that have a MIL boost setting of +9lbs and a WEP boost setting of +14lbs.
The Mosquito in my example was probably powered by Merlin 25s and would have had a WEP boost setting of +18lbs.
I have not seen any extended duration examples for WEP settings.
In AH you can run at MIL power for as long as you have fuel. Only on WEP does the engine overheat.
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The 262's engines needed to be replaced after 24+ flying hours, can we have that modelled? :D
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They also had a tendancy to 'over heat' if you monkeyed around with the throttle too much.
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Like flying on wep all the time
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There are a lot of factors. Some are engine specific others are aircraft specific. Most WEP or MIL restrictions had nothing to do with overheating the engine itself, but rather overheating specific parts in the engine, like piston heads and ball bearings. The 109s had a 30 minute restriction on the "combat and climb" setting (MIL) and a 3 to 10 minute restriction on the "emergency" setting (WEP) depending on model.
One good example of this is the P-38. Early model P-38s in Europe actually had problems with too much cooling at high altitude. They had problems keeping the engines hot enough for effective and reliable operation, while at the same time they had problems with over-revving the turbos, burning out the ball bearings.
So my conclusion is that engine cooling are rarely, if ever, a factor in restrictions on engine power settings.
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No they caught fire
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Just see how fast your engine screams down to the engine walhalla after your radiator has been bashed!
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valhalla?
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Time limits and temp limits are two different things. Games merge them together purely as a gameplay decision. I posted some info regarding the purpose of time limits in an earlier related thread.
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Originally posted by GScholz
There are a lot of factors. Some are engine specific others are aircraft specific. Most WEP or MIL restrictions had nothing to do with overheating the engine itself, but rather overheating specific parts in the engine, like piston heads and ball bearings. The 109s had a 30 minute restriction on the "combat and climb" setting (MIL) and a 3 to 10 minute restriction on the "emergency" setting (WEP) depending on model.
One good example of this is the P-38. Early model P-38s in Europe actually had problems with too much cooling at high altitude. They had problems keeping the engines hot enough for effective and reliable operation, while at the same time they had problems with over-revving the turbos, burning out the ball bearings.
So my conclusion is that engine cooling are rarely, if ever, a factor in restrictions on engine power settings.
You're half right. Turbochargers didn't use ball bearings, they used a thin film of oil that was circulated between the turbo shaft, turbine bucket wheel, and compressor wheel. If you overheat the oil by over-revving a turbo, the oil becomes almost like glue. As a result you'll freeze the turbo up and possibly melt the shaft or wheels at any contact points. Veeery messy. Sometimes over-revving a turbo would cause the compressor wheel to explode. Several experimental and the odd operational aircraft during WW2 suffered turbo explosions.
Overheating an engine depends on a variety of things. How close the cowl is to the engine, how big the radiators are, what the power output is, how much compression is present in each cylinder, RPM limits, radiator size and location, and a mess of other stuff. If you want a comparison: Bf-109G6 vs. C-47. The 109's DB engine was always overheating for a multitude of reasons that are still being debated today. Messerschmitt said it was because DB couldn't design a proper oil cooling loop, while DB said Messerschmitt had the cowling too close. Either way, the engine would readily cook itself if run at Mil for too long. Now look at a C-47; no power limits. You could run at Mil all day long and hardly put a dent in those bullet-proof radials. It's a combination of many factors that make an engine seize because of over-heating.
Restricting power because of cooling problems was present in the P-38 models built prior to the J. They didn't have enough control over engine temps, or over the air temp entering the engine from the turbo. As a result engine power was restricted to 1240hp. Once the J came along that restriction was lifted, allowing the J to make 1425hp at mil and 1600hp using WEP.
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Flakbait [Delta6]
Delta Six's Flight School (http://www.wa-net.com/~delta6)
Put the P-61B in Aces High
(http://www.wa-net.com/~delta6/sig/page25.gif)
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There are a lot of factors. Some are engine specific others are aircraft specific. Most WEP or MIL restrictions had nothing to do with overheating the engine itself, but rather overheating specific parts in the engine, like piston heads and ball bearings.
Your right there GScholz. The main factor on engine tempature is going to be your rich and lean settings, which are going to be dialed in based on you EGT readings. You are going to be adjusting your the fuel mixture of your engine based on the ALT that you are flying and mainly on what your EGT is telling you for CLY head tempatures. The first thing that is going to burn up in an engine that is running hot, because for lean mixture, (assumeing cooling system is working properly) is the pistons and the valves. These items have no Direct contact with the cooling fluid, but are in direct contact with the hotest gasses. Running an engine too lean is going to burn it up, running an engine to rich will cool CYL temps but also leads to fowling of the combustion chamber, and reduced power. The best running engine, as far as power, is one that is about to burn up.
WEP alone should not lead to an engine overheating (again assumeing the cooling system is working properly). However it will lead to much greater wear and tear on the engine compoents, mainly (but not limited to), pistons, crankshaft bearings, wristpin bearings, and head gaskets. Mixture will cause an engine failure, but this will normaly happen before the cooling system is overheated, to the point of engine failure.
got to go for now, might add more later.
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Originally posted by txmx
Any gasoline engine can over heat.
But i would think the higher you go and the thinner colder air would prolong the heating process.
The thinner the air (less dense) the less heat it can absorb, so the higher you go the harder it is to keep the engine cool.
The colder air is due to the lower density more then any other factor.
The denser the medium the better the cooling it can provide.
Remember in space no-one can hear you scream (no air = no sound)
;)
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Originally posted by SLED
Your right there GScholz. The main factor on engine tempature is going to be your rich and lean settings, which are going to be dialed in based on you EGT readings. You are going to be adjusting your the fuel mixture of your engine based on the ALT that you are flying and mainly on what your EGT is telling you for CLY head tempatures. The first thing that is going to burn up in an engine that is running hot, because for lean mixture, (assumeing cooling system is working properly) is the pistons and the valves. These items have no Direct contact with the cooling fluid, but are in direct contact with the hotest gasses. Running an engine too lean is going to burn it up, running an engine to rich will cool CYL temps but also leads to fowling of the combustion chamber, and reduced power. The best running engine, as far as power, is one that is about to burn up.
WEP alone should not lead to an engine overheating (again assumeing the cooling system is working properly). However it will lead to much greater wear and tear on the engine compoents, mainly (but not limited to), pistons, crankshaft bearings, wristpin bearings, and head gaskets. Mixture will cause an engine failure, but this will normaly happen before the cooling system is overheated, to the point of engine failure.
got to go for now, might add more later.
To a point, if you keep leaning, things get cool again (less fuel to make heat) power falls off and depending on the intake system and fuel distrubution the engine may get rough.
http://www.avweb.com/news/columns/182135-1.html#engine
http://www.avweb.com/news/columns/182084-1.html
If you want to learn how to run an aircraft engine look here folks..
This guy is an AIRCRAFT GOD IMHO
http://www.avweb.com/news/columns/182146-1.html
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Originally posted by Scootter
The thinner the air (less dense) the less heat it can absorb, so the higher you go the harder it is to keep the engine cool.
The colder air is due to the lower density more then any other factor.
The denser the medium the better the cooling it can provide.
Remember in space no-one can hear you scream (no air = no sound)
;)
This is wrong. The air is cooler at altitude because the only thing heating the air is the earth and particles in low altitudes. Ambient temperature more than anything dictates how well the air can cool your engine. At 30K and -50C the air has much a better cooling effect than at SL and +20C, even if the air is denser at SL.
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Flakbait, I stand corrected on the P-38 turbo.
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Originally posted by GScholz
This is wrong. The air is cooler at altitude because the only thing heating the air is the earth and particles in low altitudes. Ambient temperature more than anything dictates how well the air can cool your engine. At 30K and -50C the air has much a better cooling effect than at SL and +20C, even if the air is denser at SL.
Sorry I don't agree
Airplanes engines (not turbine) run hot at high alt. due to less air flow (less dense air) just like a wing looses lift.
Read the operating man. on a Turbo Charged air-cooled sometime.
DRY ADIABATIC LAPSE RATE.? If a par-cel of air is lifted, its pressure is DECREASED, since pressure decreases with height, and its temperature falls due to the expansion. If the air is dry and the process is adiabatic, the rate of temperature fall is 1?C per 100 meters of lift (10?C per Km), or 5 1/2?F per 1,000 feet of lift. If that parcel descends again to higher pressure, its temperature then INCREASES at the rate of 1?C
http://www.infodotinc.com/weather2/2-18.htm
Regards:
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P-38s ran too cool at high alts, while they didn't have any difficulty at low alts.
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To a point, if you keep leaning, things get cool again (less fuel to make heat) power falls off and depending on the intake system and fuel distrubution the engine may get rough.
Well yes of course, if you turn your mixture down far enough, the engine quits. no fuel means no go.
I was only speaking of mixture rates where the engine will run and produce usable power.
Also keep in mind I am being VERY general here, I am not trying to tell people how to run their engine on their plane. I was just speaking basic therory, on engine operations, and the effect of mixture.
Sled
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Originally posted by SLED
Well yes of course, if you turn your mixture down far enough, the engine quits. no fuel means no go.
I was only speaking of mixture rates where the engine will run and produce usable power.
Also keep in mind I am being VERY general here, I am not trying to tell people how to run their engine on their plane. I was just speaking basic therory, on engine operations, and the effect of mixture.
Sled
True, but Lean of Peak LOP operation will produce usable power and quite a fuel savings.
You can have your cake and eat it too.:)
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Originally posted by GScholz
P-38s ran too cool at high alts, while they didn't have any difficulty at low alts.
I have read that the pilots of 38 froze there butts off, using an electrical heater or some such. But not that the engines ran too cold, if true it may have a lot to due with the hi alt interceptor design and liquid cooling with large coolers (but they should have been fine at lower alt then).
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You're not consistent. If the cooling effect is better at low alts than high alts the P-38 should have had even more difficulty keeping the engines warm at low alts.
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If we use the standard atmosphere as reference the temperature at SL is 15C and the air density is 1.26 Kg/m. At 25,000 feet the temperature is -35C and the air density is 0.55Kg/m. While the amount of air passing through the radiator is about halved the temperature of that air has dropped 50C (100C is the boiling point of water, 0C is the freezing point of water). While I could easily stand naked in a light breeze at 15C I would quickly become an ice popsicle at -35C even at half the air density and even without wind.
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Originally posted by GScholz
You're not consistent. If the cooling effect is better at low alts than high alts the P-38 should have had even more difficulty keeping the engines warm at low alts.
G.. I'm sure you have heard of cowl flaps, they are used to control the amount of air flowing into and out of the cooling system and I am sure the cooling system in a liq. cooled engine also had a thermostat much like a car.
at slow air speeds the lower air flow is a greater problem and some warbirds now have water spray bars added
Here read up on a Hurricane it has a liq. cooled inline
part one
http://www.avweb.com/news/columns/185674-1.html
part two
http://www.avweb.com/news/columns/185849-1.html
I hope to be consistent if nothing else
;)
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Originally posted by GScholz
If we use the standard atmosphere as reference the temperature at SL is 15C and the air density is 1.26 Kg/m. At 25,000 feet the temperature is -35C and the air density is 0.55Kg/m. While the amount of air passing through the radiator is about halved the temperature of that air has dropped 50C (100C is the boiling point of water, 0C is the freezing point of water). While I could easily stand naked in a light breeze at 15C I would quickly become an ice popsicle at -35C even at half the air density and even without wind.
ahhh but you are not making 1200 hp
if you were fine and comfortable and properly clothed and running a long distance and I reduced your cooling system by half by adding clothing to you, what would happen
and you have just reduced the cooling system by 50% by your own math
you need to understand it is air molecules that carry away heat, in space an air cooled engine would overheat and is real cold out there
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The powerplant problems were not entirely the Allison engine's fault. Many of the reliability problems were actually due to the inadequate cooling system, in particular the cumbersome plumbing of the turbosupercharger intercooler ducting which directed air all way from the supercharger out to the wingtips and back. In addition, the lack of cowl flaps were a problem. In the European theatre of operation, temperatures at altitude were often less than 40 degrees below zero and the Lightning's engines would never get warmed up enough for the oil to be able to flow adequately. Octane and lead would separate out of the fuel at these low temperatures, causing the Allisons to eat valves with regularity, to backfire through the intercooler ducts, and to throw rods, sometimes causing the engine to catch fire.
These problems bedeviled the Lightnings until the advent of the J version with its simplified intercooler ducting and the relocation of the oil cooler to a chin position underneath the propeller spinner. When the P-38J reached the field, the Allison engine was finally able to attain its full rated power at altitude, and the engine failure rate began to go down.
http://home.att.net/~jbaugher1/p38_17.html
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While I could easily stand naked in a light breeze at 15C
Hey now! No one needs to be taking thier clothes off!
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*lol*
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added to last post please reread
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*LOL* What you need to understand is that you are not in space at 25K feet. You have 50% of the air molecules, but those molecules are considerably cooler than at SL and carry away a greater amount of heat than the 100% amount of hotter molecules at SL.
The P-38 did not have any problems with keeping the engines warm at low and medium altitudes, but at high altitudes it did. QED.
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This whole post is generally asking Pyro to code into the sim engine overheating/overcooling depending on several factors:
a) Altitude
b) Aircraft type
c) speed
Let's throw in the fact you'll need to add cowl flaps to address heat issues.
Hmmm, I'm with Pyro on this, KISS - keep it simple stupid. WEP works just great - it's simpler and easy to manage.
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Originally posted by Scootter
you need to understand it is air molecules that carry away heat, in space an air cooled engine would overheat and is real cold out there
Not necessarily. It would depend on how much of the heat is radiated out into space. If the engine was in a shadow (not in the sunlight), the engine might very well freeze solid.
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An engine wouldn't work in space ;p
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Originally posted by GScholz
*LOL* What you need to understand is that you are not in space at 25K feet. You have 50% of the air molecules, but those molecules are considerably cooler than at SL and carry away a greater amount of heat than the 100% amount of hotter molecules at SL.
The P-38 did not have any problems with keeping the engines warm at low and medium altitudes, but at high altitudes it did. QED.
You describe a cooling system that was poorly designed and had a problem with allowing the oil to warm up, yet you insist on using that to somehow convince me as to the laws of thermal dynamics and to the lower cooling ability of lower air density (by the way it is less then half the air density at 30k feet more like 80% less).
I have first hand knowledge of this and have flown as pilot in command many times in the low 20's and have seen both higher EGT and CHT levels higher with altitude as well as TIT rise on the turbo. I have opened the cowl flaps a bit and added mixture as well as lowering MP to help keep them in limits.
I will say it has been fun playing, have a good day and regards friend:)
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With oxygenated fuel and a bit of modification it would. ;)
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Someone say TITs???
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Well I'm still not convinced, but you have a good day too Sir. :)
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wow, it took you two almost 5 hours to agree to disagree!
lol
Go to bed you two. (just kidding) Neither one of you have ever worked on a P38 anyway!:lol
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Originally posted by Mister Fork
This whole post is generally asking Pyro to code into the sim engine overheating/overcooling depending on several factors:
a) Altitude
b) Aircraft type
c) speed
Let's throw in the fact you'll need to add cowl flaps to address heat issues.
Hmmm, I'm with Pyro on this, KISS - keep it simple stupid. WEP works just great - it's simpler and easy to manage.
I beg to difer.
I'd love to see some more engine management (cowl flaps, radiator opening, mixture, compressor stages, etc...) in the appropriate planes, modelled like the task was historically. (Cowl flaps or open radiator: cool engine, more drag usually, etc.)
If I have to live with KISS concept, I will. But I think this concept is contrary to accurate simulation.