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

[Crumpp]

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

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:

Crumpp says:

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

[JtD]

Originally Posted by ATAG_Dutch

Nothing changes here, does it?

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.

[bongodriver]

Originally Posted by Crumpp

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:

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

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.

[NZtyphoon]

Originally Posted by JtD

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.

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

[JtD]

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.

[Crumpp]

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.



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!

[JtD]

Originally Posted by Crumpp

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.

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

[NZtyphoon]

Originally Posted by *Buzzsaw*

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.

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

[Crumpp]

- 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

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

[JtD]

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