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Consistently those of us attempting to fly realistic missions at prototypical lengths and attempting to use prototypical recommended* engine settings (low RPM, "high" boost) in order to (a) eek out some semblance of the range that these aircraft were capable of flying and (b) fly in a prototypical manner, we are experiencing coolant temperatures of sub-60° for long periods of flight and this seems to consistently be resulting in engine failure due to overcooling. Even long periods at max continuous settings, 2650 RPM @ +7 lb/sqin boost, temperatures seem suspiciously low.

 

If there was some documentary warning or evidence that this was an issue for the Spitfire IX in particular or Merlins in general, then fair enough, but we cannot find a single warning in any period documentation, including the Pilots Notes, that covers this fallibility. 

 

Given the following attached documentation shows that these settings were RECOMMENDED for operations, it would seem a critical omission not to warn pilots of the risks of operating at them, if overcooling was actually an issue. Hence we believe this behaviour in DCS is inaccurate.

 

IMG_1282.JPG

IMG_1284.JPG

IMG_1285.JPG

 

 

We've been told there was supposed to be a revision to the thermodynamic/coolant models some time ago. We hope that this is imminent and that it sorts this issue.

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I’ve observed this behavior as well on Normandy and Channel maps the last few flights, in Summer months and Summer temps at all altitudes up to 25K’. The temps drop, oil pressure rises, and the choice is usually to fly at max continuous or higher. 

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I'm fairly certain this has been a long-standing issue. I remember trying The Big Show campaign back on 2.5.6 and my engine would always die from overcooling on my descent while RTB. I had to run max continuous but doing so guzzled gas and I overshot all my other assets in the package because they were going so slow.

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Posted (edited)

Spitfire's cooling modeling isn't complete.

It is copy pasted from P-51, but spitfire oil and coolant system consist thermostatic valves to cut off oil and coolant radiators when temps drops below 80C.

DCS is missing that feature.

In P-51 temps are regulated by controling air flow through radiators, in case of spitfire air flow is constant, only amount of oil/coolant flowing through radiators is controlled via thermostatic valves.

Thermostatic valves aren't modeled so full flow through radiators is allowed. This makes very difficulty to warm up engine in winter time, or sometimes make it impossible to warm up engine if temp is very low, another issue is low power cruise at high alt where. I've seen oil temp going to 0 C.

 


Edited by grafspee
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Posted (edited)

That's a major modeling shortcoming. Can't fly at alt or cold weather.


Edited by -0303-

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To get traction on this issue we might have to prove that the RR Merlin engine isn’t supposed to freeze in operations under normal conditions. But how? Hard to find such archival evidence from so long ago. 🤔

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Posted (edited)
5 hours ago, Moriarty said:

To get traction on this issue we might have to prove that the RR Merlin engine isn’t supposed to freeze in operations under normal conditions. But how? Hard to find such archival evidence from so long ago. 🤔

You don't need to prove anything, straight from DCS spitmanual.

JPvQAdy.png


Edited by grafspee

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Work on cooling is on the to do list,

 

I will pass on your feedback to the team 

 

thanks

smallCATPILOT.PNG.04bbece1b27ff1b2c193b174ec410fc0.PNG

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On 5/3/2021 at 7:39 AM, grafspee said:

You don't need to prove anything, straight from DCS spitmanual.

Referring to figure. Essentially (4) is the thermostatic valve that directs coolant straight to pump (7) bypassing the radiators (6) as long as coolant temp is below 80'C. If that isn't modeled, that's a shortcoming.

 

"Tunnel dampers" must refer top the flap opening if coolant temp exceeds 115'C or if radiator switch is flipped to ON.

 

"...that regulate the
coolant temperature and oil."

 

Bit of a word salad. It's a combined coolant / oil radiator? Original manual probably clearer.

 

 

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Posted (edited)

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And I could not find anything about oil thermostat, so my error, oil system does not have any temp regulation.

But coolant system does have thermostat which diverts coolant in to headed instead of radiator, when droping power.

 


Edited by grafspee

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Oil system has a viscosity valve, obviously oil viscosity relating directly to its temperature. Exactly the same idea, when viscosity is too high it’ll remain closed and oil will bypass the radiator. This clearly isn’t modelled in DCS currently either as the oil temp is remaining way too cool. 

 

There’s a pressure relief valve in the oil system which is pretty self-explanatory. Spring pressure is calibrated to open at 80psi. Again, this certainly isn’t modelled in DCS. At the moment I’m hitting 130+psi at max. cruise at altitude. 90-100 in level flight even at low altitude. It should be regulated between ~45-80psi. 
 

It’s all a bit of a mess at the moment unfortunately. For those of us running longer missions and more realistic profiles it is having a more noticeable impact, running the engine so far out of whack for longer periods is causing engine failure/total seizure. 

 

Mustang is also affected it seems. 
 

My thoughts are this new cooling model needs upping on the priority list. 

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