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P-51 too slow.


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Q07Zha3.jpg

 

 

Nothing too fancy here, just comparing test speeds in-game with available documentation.

 

In-game numbers:

 

P-51 D-15, 150oct, 10 000ft, standard atmospheric conditions (Kuban Autumn).

3000 RPM, full throttle (70"Hg) - 355-360MPH IAS (409 - 414 MPH TAS) 

 

P-51 D-15, 100 oct, 10 000ft,  standard atmospheric conditions (Kuban Autumn)

3000 RPM, full throttle (67"Hg) - 350 MPH IAS (405 MPH TAS) 

 

 

Compare it with the charts presented here:

(providing several tests of various configurations  for cross reference)

 

image.thumb.png.b2233613030b7c8f127d023d034c728d.png

 

P-51D at 3000 RPM and 67"Hg at 10 000ft - 418 TAS (13 MPH faster than in-game)

 

 

 

 

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P-51B, 3000 RPM, (originally 75"Hg, matches with 67"Hg at 10 000ft) - 420 MPH TAS, 17 MPH FASTER THAN IN-GAME

 

 

 

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Lastly, calculated performance for the P-51D at 67" - also states approx. 420 MPH TAS, SO ABOUT 17 MPH FASTER THAN IN GAME

 

I do realize that these errors might be due to the methods of calculating airspeed (not sure how the pitot tube errors are modeled in-game), but 10+ mph is quite of a staggering difference so I'd love if someone could clear this up. I haven't tested other altitudes yet because I can't be bothered, but I might when I have more time.

 

edit: just tested FTH at 7700ft at 75"Hg, ended up with 364 MPH IAS and 404 MPH TAS which leaves us with the same result of aproximately X-teen MPH missing in action. 

 

Thanks. 

Edited by ACG_Onebad
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Yeah alright that's exactly what I though which futher strengthens my point.

Additionally, the top speed of 382 MPH at sea level at 75"Hg is also at the low end of all tests performed with that engine power with some tests stating 390 MPH and even more. 

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2 hours ago, ACG_Onebad said:

Additionally, the top speed of 382 MPH at sea level at 75"Hg is also at the low end of all tests performed with that engine power with some tests stating 390 MPH and even more. 

At SL Kuban Autumn, set rpm to 86% (2750 rpm) and close oil rad manually with 150 octane : you'll get 629kph which is 391mph.

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I tested the P-51 and compared it to the 44-15342 test, at the same weight of 4427 Kg (9760 pounds) that the real test and with wing racks as indicated in the report. With radiators in automatic.

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The speed at high altitudes and top speed look good, the speeds in the first supercharger gear a bit too slow though, around 20 km/h at most altitudes, and this shrinks down to 13 km/h too slow at sea level.

Edited by -=PHX=-SuperEtendard
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5 hours ago, =FSB=HandyNasty said:

At SL Kuban Autumn, set rpm to 86% (2750 rpm) and close oil rad manually with 150 octane : you'll get 629kph which is 391mph.

 

Okay, but that still doesn't mean my point is invalid - you should be reaching that sort of speed with the oil radiator controlled automatically and 3000 RPM as per source material. There is no documentation that states that reducing RPM increases top speed. 

2 hours ago, Mitthrawnuruodo said:

@ACG_Onebad What weights (fuel and weapon loads) and radiator shutter settings did you use for these tests?

 

Wing tanks full or so, standard 6 ,.50 armament. Radiators all controlled automatically. 

There's a stability report for the P-51B also saying that putting the 85 gal tank in the fuselage and additional weight '... has no measurable effect on the maximum speed of the airplane', and if tweaking the rads or weight can give you all the missing MPH the problem is more serious than just tweaking the top speeds since it would imply that the AoA is significantly impacted by weight where it shouldn't be.

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11 hours ago, ACG_Onebad said:

Okay, but that still doesn't mean my point is invalid - you should be reaching that sort of speed with the oil radiator controlled automatically and 3000 RPM as per source material. There is no documentation that states that reducing RPM increases top speed

I didn't say it in my original post, but I actually do agree with you on those points.

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Hello gentlemen !

Here is my contribution for this topic. Well, in this message, it's not about top speed but more on the acceleration of the plane itself.
In the following video, a TF-51 Mustang pilot describes the differences between the real one, the DCS Mustang module and the Mustang in IL-2 Great Battles.


He chose 3 sequences : taxiing, take-off and landing.

 

I let you see the sequences

 

 


 

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