[RESOLVED]P51D's speed underperformance

[GrapeJam]

Currently in game, the P51D's speed in TAS at WEP is not corresponding with the actual TAS in real life test, but correspond with Yo-Yo's chart at military power.

 

Currently the in-game P51D's achieving 363 mph (585 km/h) TAS with auto radiator, 369 mph (595 km/h) with radiator closed, real life test showed that the P51D achieved 375 mph (603.5 km/h) TAS at SL. At 24000 ft the in game P51D achieves only 423mph (680 km/h) TAS, while real life test it achieved 435 mph (700km/h) TAS.

 

P51D's real life speed chart (bear in mind, this plane was tested with bomb racks on):

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

 

Yo-Yo's speed chart at 61 "hg (military power):

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

 

As you can see, the current in-game P51D's speed at WEP correspond to Yo-yo's speed chart at military power, not the actual speed at WEP in the real life test.

Edited February 29, 2016 by BIGNEWY
Title

[KenobiOrder]

Interesting find. Ill do some testing and see if I can validate your findings.

[KenobiOrder]

So after running quite a few tests, I got exactly the same results as you. The plane at WEP is getting the same speeds that Yo-Yo listed for MIL power. Also note that Yo-Yos chart closely corresponds with the MIL power tests....which would make sense. I think there is an issue with power or something on the P-51.

[312_Lobo]

+1

 

I did similar performance tests for MIL power at SL some time ago with the same result (http://forums.eagle.ru/showpost.php?p=2332942&postcount=1).

[Ala13_ManOWar]

And what atmospheric conditions where your test performed? Not the first time somebody thinks ISA charts has to match every temperature and pressure you fly in... and I tell you, no it doesn't match. A clue, SL doesn't means IAS=TAS, that's only true in ISA conditions and even there aircraft matters, weight and so. If you don't fly exact same conditions than chart, aircraft and atmosphere, it'll never ever match.

 

S!

[GrapeJam]

And what atmospheric conditions where your test performed? Not the first time somebody thinks ISA charts has to match every temperature and pressure you fly in... and I tell you, no it doesn't match. A clue, SL doesn't means IAS=TAS, that's only true in ISA conditions and even there aircraft matters, weight and so. If you don't fly exact same conditions than chart, aircraft and atmosphere, it'll never ever match.

 

S!

The speed was read in F2 view so it was TAS, weight was also accordingly.

[KenobiOrder]

And what atmospheric conditions where your test performed? Not the first time somebody thinks ISA charts has to match every temperature and pressure you fly in... and I tell you, no it doesn't match. A clue, SL doesn't means IAS=TAS, that's only true in ISA conditions and even there aircraft matters, weight and so. If you don't fly exact same conditions than chart, aircraft and atmosphere, it'll never ever match.

 

S!

 

To answer your question, I think we are all aware here of the difference these factors make. The tests were conducted in the DCS standard conditions, which is what Yo-Yo most likely did his chart based on. However, I also did tests at 15C and got the same results.

[Ala13_ManOWar]

The speed was read in F2 view so it was TAS, weight was also accordingly.

It doesn't matters, you're reading TAS for a certain conditions, not necessarily same conditions as chart . TAS is far from an absolute reading.

 

 

To answer your question, I think we are all aware here of the difference these factors make. The tests were conducted in the DCS standard conditions, which is what Yo-Yo most likely did his chart based on. However, I also did tests at 15C and got the same results.

15ºc, 1013mb (HPa) or 760mmHg, and less than 100% humidity at least. It isn't only temperature. "DCS standard condition" says nothing if it doesn't match ISA conditions charts shows, and I think DCS models atmosphere quite fine so everything matters. From chart posted I don't know aircraft weight conditions, so you also don't to match them. From Yo-yo chart I can't say his test were in those "DCS standard conditions", I don't know what means or what are "DCS standard conditions". But if he's using real test data to match module that data are ISA conditions for sure.

 

 

Looking closer to posted charts, I see them pretty close, if not the same. Yo-yo uses a test data in his chart to match module, and those data are same I see in posted chart for 61''. Also I don't know if FM has change anything since that old DCS chart was made. Anyway, as said looking closer to first posted chart, Yo-yo chart real data are the same IMHO. You're missing also the first chart uses 67'' boost. And even without knowing your atmosphere condition, at 24000ft you're getting same chart result because maximum speed in chart is @28000ft... so I don't see the problem, it's pretty close to the real thing mate...

 

S!

[GrapeJam]

Yo-yo said currently the plane's slower than it was at release. The problem is he hasn't answered whether this was correct or not.

Edited April 12, 2015 by GrapeJam

[KenobiOrder]

It doesn't matters, you're reading TAS for a certain conditions, not necessarily same conditions as chart . TAS is far from an absolute reading.

 

 

15ºc, 1013mb (HPa) or 760mmHg, and less than 100% humidity at least. It isn't only temperature. "DCS standard condition" says nothing if it doesn't match ISA conditions charts shows, and I think DCS models atmosphere quite fine so everything matters. From chart posted I don't know aircraft weight conditions, so you also don't to match them. From Yo-yo chart I can't say his test were in those "DCS standard conditions", I don't know what means or what are "DCS standard conditions". But if he's using real test data to match module that data are ISA conditions for sure.

 

 

Looking closer to posted charts, I see them pretty close, if not the same. Yo-yo uses a test data in his chart to match module, and those data are same I see in posted chart for 61''. Also I don't know if FM has change anything since that old DCS chart was made. Anyway, as said looking closer to first posted chart, Yo-yo chart real data are the same IMHO. You're missing also the first chart uses 67'' boost. And even without knowing your atmosphere condition, at 24000ft you're getting same chart result because maximum speed in chart is @28000ft... so I don't see the problem, it's pretty close to the real thing mate...

 

S!

 

Well for starters, pretty much all American flight tests are corrected to standard conditions. So we know the conditions. It is presumable that DCS uses these same conditions as a baseline since everyone uses these conditions as a baseline. DCS standard conditions fyi, are the default conditions in the game. I would hope that would be obvious....

 

Secondly, noone is missing that the chart uses 67inches of boost. That is the whole point actually. IN DCS, at 67inches in level flight you will get the same speeds listed in Yo-Yo's chart for MILITARY POWER. IE: In game WEP = the speeds he gives for MILITARY. You are correct that his chart syncs with the test he compares it to (which btw is the same test grapejam posted....) BUT IT IS SUPPOSED TO BE FOR MILITARY POWER.

 

SO TO SUM: The in game plane IS achieving the speeds Yo-Yo posted for MIL------BUT AT WEP. It goes even slower at MIL.

[gavagai]

Yo-yo said currently the plane's slower than it was at release. The problem is he hasn't answered whether this was correct or not.

 

Yes, this issue has already been reported.

 

I think we can be confident that it will be fixed, hopefully sooner than later.

[KenobiOrder]

Yes, this issue has already been reported.

 

I think we can be confident that it will be fixed, hopefully sooner than later.

 

It doesnt seem like it was reported to me. The original thread was only about SL speed from what I can tell and Yo-Yo never specified what was meant by the "changes" or as grapejam stated: whether or not the current state is as intended or not. So we cannot be confident that anything is being fixed when it was never acknowledged as a bug.

[HeadHunter52]

K4 wings get fixed, Dora gets a WP50 correction but still flies like a kite, and the 'Stang?

 

lumbers along....

[Solty]

Mods, can we have this thread moved to bug report section?

 

It realy seems to prove the point. It would be easier to track that way.

[gavagai]

http://forums.eagle.ru/showpost.php?p=2295776&postcount=22

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

 

Maybe an ED tester can confirm for us that this has been reported as a bug?

[KenobiOrder]

http://forums.eagle.ru/showpost.php?p=2295776&postcount=22

 

 

Maybe an ED tester can confirm for us that this has been reported as a bug?

 

If it had been reported I think there would be a reported tag on that SL speed thread. Also this appears to be a speed issue at all heights, and if it has indeed changes then I find it quite weird that the same speeds are popping up.

[GrapeJam]

So new patch and I've done another round of test, with both coolant and radiator fully closed I managed to reach slightly more than 375mph (605km/h) at SL and 435 mph (700 km/h) at 24k feet. The engine died very quickly and couldn't maintain more than 2 minutes of level flight. Temperature was standard, 20"c.

 

Still, the P51D in my RL test had the radiator set to automatic mode to keep the coolant at 104 "c and oil at 70"c, I'm not sure what the temperature was in that test thought.

Edited April 14, 2015 by GrapeJam

[OutOnTheOP]

So new patch and I've done another round of test, with both coolant and radiator fully closed I managed to reach slightly more than 375mph (605km/h) at SL and 435 mph (700 km/h) at 24k feet. The engine died very quickly and couldn't maintain more than 2 minutes of level flight. Temperature was standard, 20"c.

 

Still, the P51D in my RL test had the radiator set to automatic mode to keep the coolant at 104 "c and oil at 70"c, I'm not sure what the temperature was in that test thought.

 

Good news!

 

Though the engine dying so quickly and suddenly is a pain in the ass still

[GrapeJam]

Bear in mind thought, the P51D in the test had bomb racks on so clean it should be even faster, as bomb racks shave off around 8 mph at SL.

[ArkRoyal]

Reaching the correct speeds with the radiator closed doesnt do us much good however, even if there is an improvement. It should be going that fast or faster with with radiator in auto, as was already stated :)

[GrapeJam]

Also, the P51D's reaching 575km/h at SL with auto-radiator now, it seems there's an overheating problem across the board with all planes, this cause the radiator to opens more and degrade speed further.

 

I'm actually now not so sure if there was any speed increase as I got that speed out of a 5 degrees slight dive, leveled up then throttled back then increased throttle again and was able to get around 605km/h for some time, the engine just dies too quickly with radiator closed to test speed in pure level flight.

Edited April 14, 2015 by GrapeJam

[312_Lobo]

Tested it just quickly yesterday but I haven't noticed any performance change when compared to prev version. For MIL ~560km/h is still max TAS at SL with radiator set to auto. BTW RL tests we are all referring to (TSCEP5E-1908 - http://www.wwiiaircraftperformance.org/mustang/p51d-15342.html) are with radiator set to auto as well.

[Solty]

After some time has passed, the issue was not yet resolved. Can this thread be moved to bug report section?

 

I have checked the P-51D at SL. At WEP 67'hg I was able to achieve what YoYo has marked at 61'hg MIL power.

 

The P-51D is underperforming and is too slow. Still.

Edited February 29, 2016 by Solty

[BIGNEWY]

moved to bugs section

[Yo-Yo]

This issue was corrected. I have checked it and MIL/WEP is 361/375 mph.

 

The test must be perfromed at MSA conditions and be sure that the throttle is calibrated properly.