P-51D performance

[Yo-Yo]

To liberate the most dedicated users from performing boring tests:

 

http://www.forum.lockon.ru/showpost.php?p=1577405&postcount=7

[Ich666]

Great Work ED!

[Nate--IRL--]

 

Nate

[Echo38]

Loud cheer!

[NineLine]

Nice!

[a.miedlig]

Yo-Yo thanks for clarifying this !!!

 

Last qestion of mine:

does someone achieve the manifold pressure that is mentioned in the Memo Report No. TSCEP5E-1908 ttp://www.wwiiaircraftperformance.org/mustang/p51d-15342.html

or is it only me with less indicated manifold pressure for example by or over the second critical altitude. Or may be, i do something not correct in the sim.

 

But at first am happy for your good simulating the P-51 Power

[Yo-Yo]

Yo-Yo thanks for clarifying this !!!

 

Last qestion of mine:

does someone achieve the manifold pressure that is mentioned in the Memo Report No. TSCEP5E-1908 ttp://www.wwiiaircraftperformance.org/mustang/p51d-15342.html

or is it only me with less indicated manifold pressure for example by or over the second critical altitude. Or may be, i do something not correct in the sim.

 

But at first am happy for your good simulating the P-51 Power

 

Did you measure MP at the speed close to maximal? And, by the way, crytical altitudes can not exactly match because of real test inaccuracy and FM inaccuracy. But due to the speed curve shape 500-700 ft difference has no noticable effect to overqall performance. You can see crytical altitudes on the DCS FM curve.

 

Maximal crytical altitudes can be reached only at the maximal speed using ram pressure.

[a.miedlig]

Here is a 50 seconds long trk.

 

Summer, 6 °C, no wind, diving 36000 ft to 25000 ft, War emergency power,

sim mode, no externals, full speed , near compresabillity limits but

at 25000 ft only 51 " manifold pressure as max value at the end of track.

 

what can i do ?

New Track.trk

[Yo-Yo]

Here is a 50 seconds long trk.

 

Summer, 6 °C, no wind, diving 36000 ft to 25000 ft, War emergency power,

sim mode, no externals, full speed , near compresabillity limits but

at 25000 ft only 51 " manifold pressure as max value at the end of track.

 

what can i do ?

 

Maybe select rammed air?

As you can see at the diagram, the second crytical alt is about 27000 ft. IAS is about 300 mph.

[Yo-Yo]

Next test is for time to climb. Real test is from TSCEP5E - 1908 report.

 

[NineLine]

Next test is for time to climb. Real test is from TSCEP5E - 1908 report.

 

 

Nice!

[Kwiatek]

It looks that DCS have really great FM engine which can reproduce very acccurate performance of P-51 and probalby other planes too :)

 

I think now it is time for other warbirds - Bf109 or Fw190. I think all WW2 community desperadly need them.

 

Dream is to get Europe map with WW2 warbirds with DCS engine - im sure it would be great success even greater then jet era :)

Edited November 2, 2012 by Kwiatek

[Yo-Yo]

It looks that DCS have really great FM engine which can reproduce very acccurate performance of P-51 and probalby other planes too :)

 

 

Any plane we have enough valuable data for. This curves are a result of interaction of several very complicated model having thousands parametres each and I am always really is in the highest grade af astonishment when the resulting curves reauire only minor tweaks of some parametres I do not know exactly... :)

 

Only for info - underwater part of iceberg :

The plane consists of

1. Airframe model including prop and wing downwash interaction

2. Prop model that calculates thrust, moment, transversal thrust and moment for non-axial incoming airflow, downwash stream for the airframe.

3. Engine thermodynamic model that provides shaft moment, exhaust thrust, heat inflow to radiators, fuel consumption.

3a Engine automatic devices such as MP regulator, prop regulator, Bendix-Stromberg automatic carburator.

 

4 Heat sink model that calcualtes 3 radiators drag/thrust reagrding various conditions. Aftercooler circuit provides true calculation of air cooling that has very sufficient effect on engine power.

 

 

 

And a lot things I did not mention... :) like slow engine model for start-up and shut-down conditions dealing with each cylinder separately.

Then they meet each other.

[billeinstein]

Yo-Yo thanks for clarifying this !!!

 

Last qestion of mine:

does someone achieve the manifold pressure that is mentioned in the Memo Report No. TSCEP5E-1908 ttp://www.wwiiaircraftperformance.org/mustang/p51d-15342.html

or is it only me with less indicated manifold pressure for example by or over the second critical altitude. Or may be, i do something not correct in the sim.

 

But at first am happy for your good simulating the P-51 Power

http://www.wwiiaircraftperformance.org/mustang/p51d-15342.html

2. High speed in level flight at 3000 RPM and 67" Hg (War Emergency Power) is as follows for a mixture setting at "run" and coolant flaps in automatic at a take-off gross weight of 9760 pounds.

This table means with low blower, full throttle and WEP, the MP can maintain 67'' no more than 10000ft. With high blower, it will be 26000ft. That "w.o" means full throttle maybe.

 

With high speed level flight at 10000ft and TAS 417mph, MP can reach 67''. But when climbing at same altitude with IAS 165mph, MP can only reach 56.3. That's maybe because the ram effect.

Edited November 2, 2012 by billeinstein

[Echo38]

Only for info - underwater part of iceberg :

The plane consists of

1. Airframe model including prop and wing downwash interaction

2. Prop model that calculates thrust, moment, transversal thrust and moment for non-axial incoming airflow, downwash stream for the airframe.

3. Engine thermodynamic model that provides shaft moment, exhaust thrust, heat inflow to radiators, fuel consumption.

3a Engine automatic devices such as MP regulator, prop regulator, Bendix-Stromberg automatic carburator.

 

4 Heat sink model that calcualtes 3 radiators drag/thrust reagrding various conditions. Aftercooler circuit provides true calculation of air cooling that has very sufficient effect on engine power.

 

And a lot things I did not mention...

 

Did I ever mention that I freakin' love you guys?

[WildBillKelsoe]

Any plane we have enough valuable data for. This curves are a result of interaction of several very complicated model having thousands parametres each and I am always really is in the highest grade af astonishment when the resulting curves reauire only minor tweaks of some parametres I do not know exactly... :)

 

Only for info - underwater part of iceberg :

The plane consists of

1. Airframe model including prop and wing downwash interaction

2. Prop model that calculates thrust, moment, transversal thrust and moment for non-axial incoming airflow, downwash stream for the airframe.

3. Engine thermodynamic model that provides shaft moment, exhaust thrust, heat inflow to radiators, fuel consumption.

3a Engine automatic devices such as MP regulator, prop regulator, Bendix-Stromberg automatic carburator.

 

4 Heat sink model that calcualtes 3 radiators drag/thrust reagrding various conditions. Aftercooler circuit provides true calculation of air cooling that has very sufficient effect on engine power.

 

 

 

And a lot things I did not mention... :) like slow engine model for start-up and shut-down conditions dealing with each cylinder separately.

Then they meet each other.

the mere thoughts about this makes me wanna puke!! puke from fear of rape by those who understand!!! :megalol:

[billeinstein]

http://www.wwiiaircraftperformance.org/mustang/p51d-15342.html

2. High speed in level flight at 3000 RPM and 67" Hg (War Emergency Power) is as follows for a mixture setting at "run" and coolant flaps in automatic at a take-off gross weight of 9760 pounds.

This table means with low blower, full throttle and WEP, the MP can maintain 67'' no more than 10000ft. With high blower, it will be 26000ft. That "w.o" means full throttle maybe.

 

With high speed level flight at 10000ft and TAS 417mph, MP can reach 67''. But when climbing at same altitude with IAS 165mph, MP can only reach 56.3. That's maybe because the ram effect.

I just tested the low blower critical altitude:

 

W.E.P(67",3000RPM):5000ft(10000ft for historical)

Military power(61",3000RPM):7500ft(13200ft for historical)

Max Cont.(46",2700RPM):11000ft(16200ft for historical)

 

If above those altitude, the MP will drop even with full throttle. And moving the ramming air lever doesn't change the MP.

In the W.E.P climbing test, the supercharger shift from low to high at 14800ft. In the historical test it was 16000ft.

Edited November 3, 2012 by billeinstein

[Yo-Yo]

I just tested the low blower critical altitude:

 

W.E.P(67",3000RPM):5000ft(10000ft for historical)

Military power(61",3000RPM):7500ft(13200ft for historical)

Max Cont.(46",2700RPM):11000ft(16200ft for historical)

 

If above those altitude, the MP will drop even with full throttle. And moving the ramming air lever doesn't change the MP.

In the W.E.P climbing test, the supercharger shift from low to high at 14800ft. In the historical test it was 16000ft.

 

What IAS did you provide the test at? I guess you mixe climb and maximal speed tests data.

Dynamic pressure changes these altitudes significantly.

If you take a look for maximal speed chart you will see that the first critical altitude is about 13000 ft (it's the alt where speed begins to drop.

But to get it you must sweat a little... :)

 

And, by the way, the supercharger aneroid in DCS is calibrated EXACTLY as it should be according to the maintenance manual... the key point is that it uses FULL pressure before the blower. IAS and only IAS...

Edited November 3, 2012 by Yo-Yo

[billeinstein]

In the CLOD, for the Merlin engine of Spitfire IIa, to change the RPM without moving the throttle, you will find the MP will increase if decrease the RPM.

The DCS:P-51D is different. MP will drop if you decrease the RPM.

Which shall be the correct one? Or is this the real difference between these two types of Merlin engine?

[billeinstein]

What IAS did you provide the test at? I guess you mixe climb and maximal speed tests data.

Dynamic pressure changes these altitudes significantly.

If you take a look for maximal speed chart you will see that the first critical altitude is about 13000 ft (it's the alt where speed begins to drop.

But to get it you must sweat a little... :)

 

And, by the way, the supercharger aneroid in DCS is calibrated EXACTLY as it should be according to the maintenance manual... the key point is that it uses FULL pressure before the blower. IAS and only IAS...

I just build a mission, the P-51 was set air born with max speed above those altitude. I found the MP cannot reach those value(67",61" and 46"). So I just decent smoothly and tried to find the alititude the MP can reach those value. Then paused the game and read the altitude from F2 view.

 

In the W.E.P climbing test I used W.E.P and keep the IAS near 165mph as possible. I believe the time of climb is accurate in the sim. I mostly care about the engine and MP gauge, there should be some bugs, maybe are realted to the death of engine in the high alt. cruise.

 

This is the picture at 10000ft for W.E.P high speed test. IAS is 350mph, and the MP can only reach 57.5".

Edited November 3, 2012 by billeinstein

[Yo-Yo]

In the CLOD, for the Merlin engine of Spitfire IIa, to change the RPM without moving the throttle, you will find the MP will increase if decrease the RPM.

The DCS:P-51D is different. MP will drop if you decrease the RPM.

Which shall be the correct one? Or is this the real difference between these two types of Merlin engine?

 

I do not think the things in CloD is correct. So it's not a difference between Merlins but physical models. Rpm affects MP in two different ways: first of all, rpm affects blower pressure ratio close to rpm^2. The second effect is that if the throttle is significantly closed increased rpm causes pressure drop after it. This effect is very non-linear and has very different curve shape depending on rpm and throttle position. The combination of these two counteracting effects gives very complicated MP behaviour.

 

In DCS you can see MP drop under certain conditons. For example, running engine from idle to 1500-2000 at the ground you can notice that as rpm goes up initially set MP goes down. The same thing presents at 30"-40" in the air at the altitudes are lower than critical.

 

 

Concerning the ram in DCS, I am in doubt if your version works correctly with rammed air. Try to conduct the test: having IAS 300+ at the altitude higher than critical then move the left lever (RAMMED-UNRAMMED) back and forward watching MP gauge.

Edited November 3, 2012 by Yo-Yo

[billeinstein]

Concerning the ram in DCS, I am in doubt if your version works correctly with rammed air. Try to conduct the test: having IAS 300+ at the altitude higher than critical then move the left lever (RAMMED-UNRAMMED) back and forward watching MP gauge.

My version is 1.2.1.6288. I tried ,and the MP gauge has no noticable change. Even when enabled W.E.P, the MP increased no more than 1" from full military power(MP below 60"). It just likes a MP limiter, not a booster.

 

I also confirm that the MP behavior with RPM change are similar between DCS and CloD at high altitude and high speed. Both sims are good at this part.

That old spitfire has the critical alt. near 18000ft.

Edited November 3, 2012 by billeinstein

[Ala13_ManOWar]

Just a question, what atmospheric settings are you using for testing? You're talking about MP values not matching test but, are you using same atmospheric pressure and day temperature as test? If not MP can change from day to day with different pressure and temperature. And of course, altitudes will change with different pressure altitude. You have to compare Density Altitude not gauge altitude.

 

S!

[billeinstein]

The weather in DCS test is the default setting: at sea level 20C degrees and 760mmHg QNH, so the altitude in F2 is the same of the pressure altitude. I believe the historical test is based on the standard pressure altitude, otherwise the results are meaningless. And the difference can't be 5000ft.

 

One other thing is about Carburetor Air Temperature Indicator. It is never in the green when fly high enough, and just becomes a Outside Temperature Indicator. Pressurized air shall have a certain temperature rise.

Edited November 3, 2012 by billeinstein

[Yo-Yo]

My version is 1.2.1.6288. I tried ,and the MP gauge has no noticable change. Even when enabled W.E.P, the MP increased no more than 1" from full military power(MP below 60"). It just likes a MP limiter, not a booster.

 

I also confirm that the MP behavior with RPM change are similar between DCS and CloD at high altitude and high speed. Both sims are good at this part.

That old spitfire has the critical alt. near 18000ft.

 

Automatic boost control works exactly as you described - as a limiter. It can not boost anything - it only can limit MP. Throttle lever only set this limit value. In the range 55-67" it has absolute authority. It means that if you set 61", for example, at sea level it will gradually open the batterfly valve to maintain 61 exactly to the altitude wher the blower can provide 61. And there will be no changes in MP regardless rammed/unrammed position because the regulator maintains 61".

 

If you set 46" at SL you have to agvance the throttle as you gain the altitude because of regulator's limited authority.

 

The things you claimed about rammed/unrammed effect are very strange... first of all, even in earlier public beta's before we made both levers functional the air was RAMMED. In other case the tests for maximal speed could not be conducted at all.

 

Concerning carburettor air temperature: there are no means to control it if RAM is used. This gauge is mostly a warning if the temperature is in the range where icing is usually possible (+5...-15C). The only way to warm it is to use unrammed warm air coming from engine cowling. AND THIS FEATURE WAS NOT IN TIME TILL CURRENT PUBLIC VERSION so it does not work.