Oil temp threshhold for engine breakage? (Mainly Merlin engines)
 

Hi!

Has anyone tested the exact oil temperature at which the engine will break?
Or perhaps too much boost in combo with RPM, regardless of oil temp?
The radiator always breaks at 120 Celsius, 10/10 times, however, the oil temp is a bit more elusive.
(I don't give a rats ass about the pilot notes)

Thanks in advance :)

Taking all aircraft but the Spit IIA over 98 degrees is a mistake, the Merlin III might not break immediately, but there will be consequences.

The Spit IIA Merlin XII can run at temps below 105 degrees below 5000 ft, but as you get higher, the temperature limitation threshold drops. Over 10,000 ft, not a good idea to go over 95 degrees.

I imagine the temp threshold drops for the other engines as well. That explains why the engine broke after a while at 91 degrees oil temp at 14k feet.

Yes, temp max. for the Merlin III, (all aircraft but the Spit IIA) is 98 degrees below approx. 5,000, but as you go over that, temp limit gradually drops. And it is different for different aircraft, ie. the Spit IA 100 octane is different from the standard Spit IA.

This is major bug in the game. The higher you go, the cooler the engines should run, and less likely the chance of damage.

If you want to do comprehensive testing that would be nice... :) Ivan and I have already done testing for the engine misfiring bug for the British aircraft, but not on the overheating yet.

109 engines do not have any oil temp problems as long as you keep the oil at approx. 25% and radiator open to 3/4 mark. AFAIK! ;)

That is wrong.

The higher you go, the less effective the cooling due to pressure and density reduction despite the cooler temperatures.

So while the temperature does get cooler IAW the lapse rate, the density is reduced so we end up with less molecules to transfer heat away from our engine.

I can't say I am an expert on this matter. I made the assumption there is enough flow with the higher speeds at altitude and the cooler temps to cool the aircraft faster. Ie. IAS at sea level and 6000 meters may read the same, but TAS is much higher at altitude, and therefore airflow is much higher.

Anyone else want to comment?

Airflow is not much higher because of True Airspeed.

Indicated airspeed is what matters, if indicated is high enough then cooling will be sufficient.

Bingo!

Nothing changes here, does it?

Oil temp. Whatever settings people tell you to fly at, fly at less, apart from airspeed. Whether it be RPM or boost. Most people in a game fly at max poss everything all the time. Total rubbish.

What is the oil temp at which your engine blows? Find out. Run your mouse over the oil temp gauge and wait for it. Try it at different rpms. Try it at different boost settings. Just fly. Offline until you find out. Then you'll know.

Everything is there for you to find this out for yourself. Go to it.

Edit: 97 degrees. If memory serves correctly........

:rolleyes:

Why don't you take the time to explain the relationship of Indicated airspeed, True airspeed, and altitude?

Then take some to explain the general behavior of a altitude effects on thrust production at constant power setting and indicated airspeed.

After you have done that, you can sum it all up as:

Annoying, isn't it? I don't think this is the best subject to make generalisations, because temperature over altitude characteristics depend on aircraft, engine, engine settings, flying regime. So I suggest to find a different excuse for being rude to each other.

OK then:

if you climb at constant airspeed then true airspeed increases with altitude, at constant indicated airspeed the 'mass' of air flowing through the cooling system remains constant with the added effect of reduced ambient temperatures.
penalties of high altitude on performance are not really a factor, bottom line is if you keep the same amount of air mollecules passing through the cooling system then you won't have problems cooling, I'm not entirely sure where crumpp gets the theory that maintaining constant indicated airspeeds is not possible but everyone else understands that a constant reading on the airspeed indicator means constant indicated airspeed and we also know how to achieve it.
To some extent engine temperatures will also fall off with the natural reduction of power with altitude also.


Oh and :rolleyes:

Looking forward to the next installment from the Nonsensical Administration of Crumpp Aeronautics

p.s. I'll post you a picture of what high altitude shows on the Learjet PFD tonight as I have an empty sector back from Denmark tonight.

I suggest that no-one argue with Crumpp because it is patently obvious that he is THE undisputed expert on everything. :rolleyes:

It's not a Crumpp problem here. The generalizations are pointless.

Indicated air speed is not equivalent to mass flow, because there's a square root over density in the IAS calculation. At a constant IAS, mass flow goes down with altitude. WW2 aircraft generally achieved lower IAS's with altitude, so mass flow goes down even more. This is countered by the reduced temperatures at altitude.

Now you can argue all day about the net effect, but unless you come up with a statistically significant number of test results, it will remain pointless. What remains is an unnecessary exchange of rudeness, which I think this forum has seen enough.

JtD,

It is a basic principle of heat exchanger efficiency. It is not really open to much discussion and the fact so much is made of such a simple thing is telling.

:rolleyes:

Bongodriver, by all means post your findings. You might learn something.

Take a guess what the p is in the formula??

Don't let that stop you from posting the findings from a turbojet. We can then change the subject to some basic properties of thrust producers! Like I said, you will learn something!

The basic principle of heat exchangers seems to be clear to everyone, including bongodriver.

But:
- basic principles of heat exchangers don't fully explain general aircraft engine oil temperatures
- general aircraft engine oil temperature characteristics don't fully explain Spitfire specific oil temperatures
- detailed Spitfire oil temperature info won't change a thing in game, because development is dead

The idea in CLOD was to recognise the differences between the Merlin II & III, which were cooled by 100% glycol, and the Merlin XII which was cooled by a 70-30% water-glycol mix. As a rule the earlier Merlins ran at higher temperatures and were more likely to have oil seals fail - unfortunately the CLOD engines are still too sensitive and too prone to failure but, as JTD said, there will be no more development so that's the best that we can expect

The basic physics and principles of heat exchangers explain ALL aircraft heat exchanger behavior.

;)

Yes. I totally agree with that, heat exchanger physics explain heat exchange.

Learn something from you?......I doubt it.

I'm not posting pics for means of making revelations other than gratuitous 'look at me here at FL400 taking pics for my forum buddies', I couldn't post yesterday because I didn't make it back to home base before they closed and diverted to Luton, hotel had crappy wifi and I only had my phone, still it meant I got to take some more pics of todays sectors to Stuttgart and Sion, the latter being very Christmassy so I thought they'd go nice.

pics 1,2 on way back from Aalborg yesterday, pic 3,4 on ramp at Luton this morning, pic 5 on ramp at Stuttgart.

Heres the Christmassy ones, the amazing view approaching the Swiss Alps and the descent on the 'IGS' approach to Sion.

Merry Christmas everyone, maybe we'll be nicer to each other next year....;)

Nice photos, particularly like the first 2:cool:

what height were you over the alps?

probably around 23000' in a descent to 17000' by the time I started taking the Sion pics.

Nice to see a commercial pilot that actually puts his commercial license to use. ;)

Good, then what the heck is all the other nonsense about it does not apply to certain airplanes under certain conditions!!?


I thought you were going to post some pictures on the temperatures differences for us. I see you backed off that one.

When are you going to list the 16 squadrons that were the only squadrons to use 100 octane fuel during the BoB?

Must be like the Fw190s that were at Stalingrad in the late fall of 1942.

:rolleyes:

Never said that. Physics always apply. I said:
- basic principles of heat exchangers don't fully explain general aircraft engine oil temperatures
- general aircraft engine oil temperature characteristics don't fully explain Spitfire specific oil temperatures

That means, while it is comparatively easy to estimate the heat exchange in the radiator for a given set of conditions, this is just one piece of the puzzle of oil temperature calculation.

Did they know about the counterflow multiplier in WW2?

http://en.wikipedia.org/wiki/Countercurrent_exchange

It makes a huge difference to efficiency.

http://en.wikipedia.org/wiki/Werner_Kuhn

So, perhaps not?

Other aspects to be considered: coolant used; efficiency of coolant flow; thermal efficiency of engine/engine components, mechanical efficiency of same, etc etc

http://www.freestudy.co.uk/thermodynamics/t4201.pdf

Ahhh, Spitfire physics!! Maybe research at the LHC will one day be able to explain it?

That is all considered in the math.

Ahhh, crumpp troll! Maybe research at the Trolling Academy will one day be able to explain crumpp?

Congratulate yourselves on the closure of another thread.

I'm sure your making everyone happy here with your continued personal attacks resulting in thread closures.

Or perhaps infractions leading to banning is your preference.



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