Acceleration comparisons

[horseback]

Originally Posted by gaunt1

Please... Check the ACCELERATION chart made by HORSEBACK. (page 6, post # 44) It clearly shows the insane advantage of the FN over the F. For example, 270 to 500 km/h takes 56 seconds for F, and 36 seconds for FN. Thats 55.5% better performance.

I'd say that it's more like 55.5% better time. The lead one develops through each 10kph interval is added to the next one, and the next, sort of like compounded interest. If you have a power advantage of 20%, it is applied in each interval, and that advantage increases with every subsequent interval.

Acceleration is usually expressed in terms of both time and distance: some many meters per second per second (or per second squared). It is an ongoing process, and the primary limitation is air resistance, or drag, which increases as a cube of the velocity, if I remember correctly. In any case, you need exponentially more power to overcome drag as speed increases, which is why my charts depict curves instead of straight lines.

cheers

horseback

[MaxGunz]

There's 2 main kinds of drag operating here. A total drag graph is U shaped.

At lower speed **for the plane with wing loading a big factor** is induced drag. This is a real killer for the FW's until maybe 340-360 kph.

From middle speed on up, parasite drag goes up by squares, twice the speed is 4x the parasite drag even as induced drag falls due to lift squaring with increased speed allowing the nose to drop while keeping level flight. (trim)

Ps is excess thrust, total thrust minus drag. The faster a prop plane goes, the less thrust it has which is where the steepness of Ps curve at high speed sets in. It's not a constant minus the drag U but a downward slanted line minus the drag U.

I just had a look at La5F vs La5FN (IL2C 4.07m) and the La5F Ps curve looks the same as the La5 Ps curve when switching back and forth.

What's the difference between a Spit VB and a Spit LFVB besides supercharger?

At 240 kph, Spit VB = 13.5 -- Spit LFVB = 17.3 --- 128%
At 320 kph, Spit VB = 10.5 -- Spit LFVB = 15.5 --- 148%
At 400 kph, Spit VB = 3.8 -- Spit LFVB = 9.9 ------ 260%
At 430 kph, Spit VB = 0 -- Spit LFVB = 7 ----------- PWNED!
What % longer will the Spit VB take to reach 440 kph in level flight? If 50% longer is insane then what is forever?

[horseback]

What's the difference between a Spit VB and a Spit LFVB besides supercharger?

At 240 kph, Spit VB = 13.5 -- Spit LFVB = 17.3 --- 128%
At 320 kph, Spit VB = 10.5 -- Spit LFVB = 15.5 --- 148%
At 400 kph, Spit VB = 3.8 -- Spit LFVB = 9.9 ------ 260%
At 430 kph, Spit VB = 0 -- Spit LFVB = 7 ----------- PWNED!
What % longer will the Spit VB take to reach 440 kph in level flight? If 50% longer is insane then what is forever?

Depends on the flavor of Mk Vb we're talking about; the early ('41) version has a bit less 'oomph' over all, the late ('42) version is essentially the same as the '43 clipped wing version with slightly less wing loading, and the Merlin 46 type has a different engine which is (I assume) optimized for high-medium alts.

Minor variations may be ascribed to my faults as a test pilot, or arbitrary decisions about averaging out the results of the four runs for a given type.

cheers

horseback

[MaxGunz]

Those are the ones in IL2Compare 4.07m, the last IL2C I have.

[IceFire]

Originally Posted by MaxGunz

Those are the ones in IL2Compare 4.07m, the last IL2C I have.

There's a 4.11 IL2 Compare kicking around. Haven't seen a 4.12 yet...

[Monty_Thrud]

Originally Posted by IceFire

There's a 4.11 IL2 Compare kicking around. Haven't seen a 4.12 yet...

http://forum.1cpublishing.eu/showthread.php?t=29744

Scroll down for 4.11

[MaxGunz]

I've had IL2C 4.11 and 4.07m for a while it turns out, just only a shortcut to 4.07m on the desktop. 4.07m version is off now, 4.11 link in place and holy cow now I see the confusion! I forgot about the rabbit Spitfire versions and now I have to wonder why is there no P-51D with empty fuselage tank and CoG to match? Then we could hear a new verse or chorus to 'stang-whining based upon stick forces too high.

[pandacat]

It's quite interesting to see post-510kph, 2700rpm actually accelerates faster than 3000rpm for p51c. Btw, do you have similar data on P51Ds? 5nt and 20na. I would expect slightly worse performance. Also, it's surprising to see 109G series has slower acceleration than mustangs given 109 has higher power to mass ratio.

[MaxGunz]

Consider how CSP's work in the case of the P-51.

[pandacat]

Originally Posted by MaxGunz

Consider how CSP's work in the case of the P-51.

But doesn't everybody else have CSP, too? Spit, 109, 190? Or P51's CSP is somewhat special? For spit and 109, it seems from the charts that 3000rpm always accelerates faster than 2700rpm