Max speed at sea level

Rolfey · January 15, 2015

Hi guys

This might have been brought up before. Been looking at some test data for the P51 and the maximum speed at sea level for the Packard Merlin 1650-7 engine.

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

If you look at this document it states the following:

Maximum speed at sea level

War Emergency power (3000 RPM and 67") 375 MPH

Military power (3000 RPM and 61") 364 MPH

Normal Rated power (2700 RPM and 46") 323 MPH

It may be just me and my flying style but I have never been able to get the aircraft over 328mph in level flight at sea level.

In that situation I had to run the aircraft at 2700rpm at 67" . 3000rpm actually caused airspeed to drop below 320mph. This is on a completely clean and trimmed aircraft.

Is this an error in the flight model?

Thanks

Rolfey

USARStarkey · January 15, 2015

Hi guys

This might have been brought up before. Been looking at some test data for the P51 and the maximum speed at sea level for the Packard Merlin 1650-7 engine.

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

If you look at this document it states the following:

Maximum speed at sea level

War Emergency power (3000 RPM and 67") 375 MPH
Military power (3000 RPM and 61") 364 MPH
Normal Rated power (2700 RPM and 46") 323 MPH

It may be just me and my flying style but I have never been able to get the aircraft over 328mph in level flight at sea level.

In that situation I had to run the aircraft at 2700rpm at 67" . 3000rpm actually caused airspeed to drop below 320mph. This is on a completely clean and trimmed aircraft.

Is this an error in the flight model?

Thanks

Rolfey

you sure you werent looking at knots? 328 knots is 377mph.

gavagai · January 15, 2015

I got:

max sustained: 513km/h (319mph)

military power: 553km/h (344mph)

WEP: 566km/h (352mph)

and then using your trick of 67" MP and 2700rpm, 572km/h (356mph)

This was looking at the F2 view airspeed and in the free flight batumi quick mission.

Rolfey · January 15, 2015

you sure you werent looking at knots? 328 knots is 377mph.

Il have to double check.

Solty · January 15, 2015

I got:

max sustained: 513km/h (319mph)
military power: 553km/h (344mph)
WEP: 566km/h (352mph)

and then using your trick of 67" MP and 2700rpm, 572km/h (356mph)

This was looking at the F2 view airspeed and in the free flight batumi quick mission.

It should be:

Max speed at SL:

War Emergency power (3000RPM and 67HG) 375MPH

Military power (3000 RPM and 61") 364MPH

Normal Rated power (2700 RPM and 46") 323MPH.

Also, Mustang P-51D should have 1720hp at WEP with 67HG

Why then DCS manual states it has 1595hp with WEP :huh:

http://www.wwiiaircraftperformance.org/mustang/mustangtest.html

It seems like the Mustang is too slow and too weak. (if what you say with the speed at SL is correct) I am writiing my thesis and can't check it.

Also, what is the Mustang we have in game? P-51D20? D25? D30? I know it is not D5 for sure. It has the tail fin

Edited January 15, 2015 by Solty

gavagai · January 16, 2015

Has the P-51D airspeed always been in the same in DCS or was this an unintended change that happened recently?

Shahdoh · January 16, 2015

It has been this way since 2013 at least as far as I have seen.

Solty · January 16, 2015

It has been this way since 2013 at least as far as I have seen.

As we saw with DCS Bf109K4 it took a month for somebody to notice huge overclimbing issue. Just because something wasn't looked at for a long time should not be ignored.

I have all 3 planes now, and I have to say... I took too many things for granted because of the reputation that the game has. It is seen as the god of simulation. Which is harmful to it's development because people do not question what they are given.

If it is a masterpeice as portrayed, it will defend itself and a little bit of community investigation is always a good thing. It helps games grow and ensure everything is within working order.

That is why this thread is not a bug report, but just a place to check the data and perform tests. If any problems or discrepancies are to be discovered the new bug report thread will appear. :book:

Shahdoh · January 16, 2015

Just curious, are there any charts showing speeds at different RPM settings at max manifold pressure? I always just thought of it as finding the mechanical sweet spot of getting more bite from the prop at the given mp. /shrug

Solty · January 16, 2015

Check here:

http://www.wwiiaircraftperformance.org/mustang/mustangtest.html

Talisman_VR · January 16, 2015

As we saw with DCS Bf109K4 it took a month for somebody to notice huge overclimbing issue. Just because something wasn't looked at for a long time should not be ignored.

I have all 3 planes now, and I have to say... I took too many things for granted because of the reputation that the game has. It is seen as the god of simulation. Which is harmful to it's development because people do not question what they are given.

If it is a masterpeice as portrayed, it will defend itself and a little bit of community investigation is always a good thing. It helps games grow and ensure everything is within working order.

That is why this thread is not a bug report, but just a place to check the data and perform tests. If any problems or discrepancies are to be discovered the new bug report thread will appear. :book:

Very much agree with what you say about reputation and taking things for granted. I am a WW2 combat flight sim fan and have only dipped my toe in with DCS with the P51 to see if they are likely to meet the grade with the WW2 project. I will only purchase more aircraft if improvements are made and am waiting for Edge, Normandy map and better damage model for WW2 aircraft, etc. If DCS delivers the goods then I (and probably the rest of my squad mates) will be a long term and avid customer. If not, then I shall not continue with DCS for the future.

Solty · January 16, 2015

OK... I flew at SL with some different setings:

35%fuel.

Radiator auto

WEP 67' 3000RPM

585kph=363mph

81%fuel 4427kg

Radiator auto

WEP 67' 3000RPM

588kph=365mph

81%of fuel 4427kg

Radiator closed manually.

WEP 67' 3000RPM

594kph=369mph.

Edited January 16, 2015 by Solty

Yo-Yo · January 16, 2015

http://forums.eagle.ru/showpost.php?p=1577405&postcount=7

gavagai · January 16, 2015

So, why is my P-51D so much slower than that?

I had the aircraft perfectly trimmed....:dontgetit:

USARStarkey · January 16, 2015

So, why is my P-51D so much slower than that?

I had the aircraft perfectly trimmed....:dontgetit:

Its slower because its not as fast as it should be in the game. Ive posted about this before and there is something funny going on with the speed, perhaps even the wep. Oddly enough, if you look at Yo-Yos chart there and then go in game and test, you get the speeds he indicated with 67inches not 61. I did extensive flying to see how fast you could go at 24000ft, and I got the same speed in multiple runs and I could go any faster at wep than he puts on that chart...which is at military power.

GrapeJam · January 17, 2015

Hi guys

This might have been brought up before. Been looking at some test data for the P51 and the maximum speed at sea level for the Packard Merlin 1650-7 engine.

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

If you look at this document it states the following:

Maximum speed at sea level

War Emergency power (3000 RPM and 67") 375 MPH
Military power (3000 RPM and 61") 364 MPH
Normal Rated power (2700 RPM and 46") 323 MPH

Also keep in mind that the plane in the test had bomb racks, and the radiator was set to automatic mode.

Solty · January 17, 2015

So wep IRL has a quite noticible effect on the P51s speed at SL.

My tests with WEP are similar to the value given under military power.

It is a discrepancy of 10mph when we take the test with radiator set to auto and 6mph with manual radiator closed.

That is a noticible difference that may decide of life or death in a combat situation.

Anatoli-Kagari9 · January 17, 2015

I love this threads... Makes me feel so basic when it comes to aircraft performance, and combat aircraft, that I usually end up going for a flight in my 744 being able to master all of those complex systems and saying to myself - you're a great v-pilot José, nevermind... Then I go online at one of the servers, gavagai's being a good example, and am canon fodder in a couple of minutes and think - well, that's probably because of that "bug" in the K4 pr P51 perfromance... I could have done better otherwise :-)

I love this sim! Really! But it makes me feel so short sighted, visually and brainly....

Kwiatek · January 17, 2015

It should be:

Also, Mustang P-51D should have 1720hp at WEP with 67HG
Why then DCS manual states it has 1595hp with WEP :huh:

http://www.wwiiaircraftperformance.org/mustang/mustangtest.html

It seems like the Mustang is too slow and too weak. (if what you say with the speed at SL is correct) I am writiing my thesis and can't check it.

Also, what is the Mustang we have in game? P-51D20? D25? D30? I know it is not D5 for sure. It has the tail fin

I think it is bug in DCS P-51 manual where they put data from Packard V-1650-3 engine instead of Packard V-1650-7.

Looking at performance of DCS P-51 there is clearly modeling V-7 version ( lower altitude version - Merlin 66)

USARStarkey · January 18, 2015

So wep IRL has a quite noticible effect on the P51s speed at SL.
My tests with WEP are similar to the value given under military power.

It is a discrepancy of 10mph when we take the test with radiator set to auto and 6mph with manual radiator closed.

That is a noticible difference that may decide of life or death in a combat situation.

Indeed. If you run WEP, you get the speeds on Yo-Yo's cahrt for military power. If you run military power, you get even less.

Crumpp · January 19, 2015

For Solty....

Here is that spreadsheet.

Yo-Yo · January 19, 2015

Seems to be proven - max speed is not it was during release.

USARStarkey · January 19, 2015

Seems to be proven - max speed is not it was during release.

Could you clarify this please.

Yo-Yo · January 20, 2015

Could you clarify this please.

Could somebody clarify this for me...

USARStarkey · January 20, 2015

Could somebody clarify this for me...

I dont understand what your trying to say.......could you reword it? How was that hard to understand. FYI: your English was a bit broken there and I wanted to get a better understanding of what you meant......no offense

Are you saying that the speed has changed since you made those charts?

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Max speed at sea level

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