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4 hours ago, grafspee said:

Idea for liquid cooling is, that with cooling radiator you can achieve much much greater cooling surface then any air cooled engine. By the look of P-51 diagram radiator looks pretty large, bigger then 109 both combined, still bf-109 handle temps much better. 

P-51 is capable of doing military power run up on the ground, which is impossible in DCS.

At warm day even with radiator doors w/o 61" take off is not an option, In manuals no a single word about this issue, quite opposite in cold weather additional shutters are installed to prevent over cooling.

Manual states, that radiator controls stays at AUTO position all the time from start up to shut down, manual is used when auto fails, in DCS i have to use manual very often, this definitely says something.

 

If it was so, the most powerful engines would be with liquid cooling. But the late monsters were all air cooled, even if they were 4 rows stars. Sabre, in its turn, required a giant radiator with a frontal area comparable to the radial engines. The main reason of liquid cooling popularity in 30' was the fact that for the early engines liquid cooling gave an opportunity to have less frontal area of the engine itself (and, thus, the airplane as well) comparing to radials. The power was relatively low, and the required radiators were quite compact. And, besides, only liquid cooled engine can be combined with a cannon.
The early Merlins with 800-900 hp had the same frontal area as the late Merlins with 1600-1700 hp but required radiator areas grown proportional to new power, and radials with the same power in comparison did not seem too draggy. 
Air cooling has one big advantage - it heats the cooling air much more than radiator does, so the heat transfer is more effective and the drag is much less due to ram jet or Meredith effect.

Ніщо так сильно не ранить мозок, як уламки скла від розбитих рожевих окулярів

There is nothing so hurtful for the brain as splinters of broken rose-coloured spectacles.

Ничто так сильно не ранит мозг, как осколки стекла от разбитых розовых очков (С) Me

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15 minutes ago, Yo-Yo said:

If it was so, the most powerful engines would be with liquid cooling. But the late monsters were all air cooled, even if they were 4 rows stars. Sabre, in its turn, required a giant radiator with a frontal area comparable to the radial engines. The main reason of liquid cooling popularity in 30' was the fact that for the early engines liquid cooling gave an opportunity to have less frontal area of the engine itself (and, thus, the airplane as well) comparing to radials. The power was relatively low, and the required radiators were quite compact. And, besides, only liquid cooled engine can be combined with a cannon.
The early Merlins with 800-900 hp had the same frontal area as the late Merlins with 1600-1700 hp but required radiator areas grown proportional to new power, and radials with the same power in comparison did not seem too draggy. 
Air cooling has one big advantage - it heats the cooling air much more than radiator does, so the heat transfer is more effective and the drag is much less due to ram jet or Meredith effect.

The question is why don’t other liquid cooled engines in DCS suffer from these same issues if the P-51 is modeled correctly? 
P51 Bf109 Slow Speed overheat comparison

 

https://youtu.be/merlb5souSQ


Edited by pmiceli
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Radial engines when ppl figured out how to do 2 3 row radial become better power package then V-12.

I only hope that waiting for new cooling modeling will end soon.

I recall some P-51 pilot speaking about combat, he escaped from bf-109 going straight up and he kept going like that until bf-109 stalled it was at high altitude. 

 


Edited by grafspee

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On 7/31/2021 at 2:27 AM, grafspee said:

Radial engines when ppl figured out how to do 2 3 row radial become better power package then V-12.

I only hope that waiting for new cooling modeling will end soon.

I recall some P-51 pilot speaking about combat, he escaped from bf-109 going straight up and he kept going like that until bf-109 stalled it was at high altitude. 

 

 

I tried this tactic once. Took a 30mm cannon round straight up the tail pipe.

[sIGPIC][/sIGPIC]

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5 hours ago, _Spad_ said:

I tried this tactic once. Took a 30mm cannon round straight up the tail pipe.

It was G-6 for sure with K-4 different story 🙂

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1 hour ago, pmiceli said:

They would both torque out long before stall. 
 

Not so much in DCS. 

This pilot used stall in wider meaning, this mean "until bf-109 lost control" remember pilots speaking in interviews are nor reporting to NACA supervisor so language is not strictly technical.

And planes in DCS does lose control due to engine torque when speed is very low in vertical flight.

It happens to me very often when i do loops in Dora. In case P-51 coolant boils off at 100mph so not often happens to me.


Edited by grafspee

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On 7/30/2021 at 6:56 AM, grafspee said:

By the look of P-51 diagram radiator looks pretty large, bigger then 109 both combined, still bf-109 handle temps much better. 

The Merlin and Packard engines ran there coolant at much higher pressure and therefore temperature than the Daimler Benz - due to much better metallurgy and casting. The higher temperature results in a much higher radiator LMTD which improves efficiency. 

 

An excellent summary of the development of the respective engines. And as per the presentation the fastest piston engine plane ever was a specially tuned Mustang. The video also shows how large the Bf-109 radiators really were and the low quality compared to the Spitfire radiators. At the end of the war the quality of manufacturing in Germany must have been terrible. The same was the case in Japan where metallurgy and quality as well as palm fuel had a terrible effect on the IJAF/IJN 

 

The anecdote about the Mustang outclimbing the Bf-109 is Bud Anderson on Dogfights I am sure 


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7 hours ago, grafspee said:

This pilot used stall in wider meaning, this mean "until bf-109 lost control" remember pilots speaking in interviews are nor reporting to NACA supervisor so language is not strictly technical.

And planes in DCS does lose control due to engine torque when speed is very low in vertical flight.

It happens to me very often when i do loops in Dora. In case P-51 coolant boils off at 100mph so not often happens to me.

 

I don't think you understand me. 

 

DCS props have enough control authority to overcome torque up to aerodynamic stall. Either torque is too low/not properly modeled or the controls are too effective/modeled to lose effectiveness at the stall.

 

 You can go from throttle stop to throttle stop quickly in the P-51 without any real need for control input at any speed above aerodynamic stall. The 109 isn't quite that docile but it's torque is pretty underwhelming as well.

 

No matter, it is not going to change.

 

However, the behavior of the Merlin radiators gives a whole new meaning to "Go Up, Blow Up"

 

Its getting pretty obvious that all the LW MP regulars are now very familiar with this. The vertical defense, which should get them killed, is in widespread use and extremely effective.

 

I hope it gets fixed someday.

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The Bf 109K-4 is more efficient in low speed cooling because of how the system is designed, and there for can cool better than say the P-51 or Spitfire, but as I have told everyone, the new cooling system is coming, and when its introduced we will revisit how it functions and how damage and abuse is calculated.

 

@pmicelithis is in reference to your tracks as well.

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7 hours ago, pmiceli said:

I don't think you understand me. 

 

DCS props have enough control authority to overcome torque up to aerodynamic stall. Either torque is too low/not properly modeled or the controls are too effective/modeled to lose effectiveness at the stall.

 

 You can go from throttle stop to throttle stop quickly in the P-51 without any real need for control input at any speed above aerodynamic stall. The 109 isn't quite that docile but it's torque is pretty underwhelming as well.

 

No matter, it is not going to change.

 

However, the behavior of the Merlin radiators gives a whole new meaning to "Go Up, Blow Up"

 

Its getting pretty obvious that all the LW MP regulars are now very familiar with this. The vertical defense, which should get them killed, is in widespread use and extremely effective.

 

I hope it gets fixed someday.

No one in RL do that so there is no proof of your statement. I know only one thing that in P-51 torque effect on the airframe is much lower then most ppl expect. 

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If you want to push the P-51 to the edge you cannot leave either of the radiators in the “AUTO” settings. AUTO has been porked for a long time. If you plan to be aggressive in the vertical you must open both doors fully before engaging in the action. Opening the doors after or while going to the vertical will result in the cooling not being able to recover. Take manual control of the radiators and life will be much better for you. Check the gauges often! After a while it will become second nature of knowing how many seconds to hold the switch to open or close the doors. Keep in mind that the doors move very slowly a full 14-17 seconds to open all the way.

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8 hours ago, grafspee said:

No one in RL do that so there is no proof of your statement. I know only one thing that in P-51 torque effect on the airframe is much lower then most ppl expect. 

One of the more well known demonstrations of the effect of torque in the P-51 was to have the new P-51 pilot climb to a safe altitude, set the power to 15 inches, slow to 140 with gear and flaps down and quickly advance the power to 61 inches.

 

The aircraft would end up inverted.

 

Nothing remotely like this is possible in the DCS P-51.

 

And I don't need "proof". It is basic physics. At a given power setting, torque is at T magnitude. The force required to counter T is of the same magnitude in the opposite direction, let's call it X.

 

Force X comes from the control deflection of the aileron and rudder. X varies with airspeed for a given control deflection.

 

So for every change in airspeed at a given T, the control deflection must change to maintain X. At some airspeed, there is not enough control deflection available to create enough X to counter T.

 

Equally true is that for every change in T there is a corresponding change in X, requiring a change in control deflection.

 

At present, you can pretty much change power or airspeed (above aerodynamic stall) without any real need to change control inputs to counter the constantly changing torque/control deflection relationship in the P-51.

 

Basically, it flies like a jet.

 

However, it isn't going to change. 

 

7 minutes ago, Rebel28 said:

If you want to push the P-51 to the edge you cannot leave either of the radiators in the “AUTO” settings. AUTO has been porked for a long time. If you plan to be aggressive in the vertical you must open both doors fully before engaging in the action. Opening the doors after or while going to the vertical will result in the cooling not being able to recover. Take manual control of the radiators and life will be much better for you. Check the gauges often! After a while it will become second nature of knowing how many seconds to hold the switch to open or close the doors. Keep in mind that the doors move very slowly a full 14-17 seconds to open all the way.

My demonstration video of this issue is with the radiators wide open in manual. My autostart script opens the radiators wide open in manual and I rarely ever change them from that setting.


Edited by pmiceli

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@pmiceli If on your end, you don't need to adjust aileron or rudder while airspeed is changing or power is changed then you must have some thing broken, on my end even slight change of speed required to adjust rudder trim to keep plane flying level.

You must have activated auto rudder or something.

If you saying that you don't need to change anything at all, while changing speed or power then you definitely must have something wrong. 

P-51's vertical stabilizator is very large, rudder is so effective that counter acting trim tab was installed to prevent excessive forces being induced on airframe.

140 mph is sufficient speed to mitigate all prop effects on airplane, since plane can take off at full power at lower speed w/o instantly snap rolling 🙂

And torque is only 1 of 4 aspects which contribute how prop driven plena behave, and torque effect shows at very low speed. 


Edited by grafspee

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  • 1 month later...

Йо-йо я обращаюсь к тебе лично!

Вопрос!

Я купил модуль Р-51 в 2013 году. Это было откровение! Это было за гранью  рукожопов которые летали на дельтапланах...и пытались делать симуляторы.

Что случилось спустя 8 лет с модулем ?  Почему передовые технологии на тот момент времени.. бездарно греются  даже с открытыми радиаторами?

Ты сломал модуль?

 

 

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2 hours ago, BELKA_ said:

Йо-йо я обращаюсь к тебе лично!

Вопрос!

Я купил модуль Р-51 в 2013 году. Это было откровение! Это было за гранью  рукожопов которые летали на дельтапланах...и пытались делать симуляторы.

Что случилось спустя 8 лет с модулем ?  Почему передовые технологии на тот момент времени.. бездарно греются  даже с открытыми радиаторами?

Ты сломал модуль?

A new cooling system is coming, also please keep to English in the English section. Thanks.

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