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Panthera

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  1. @unreasonable Keep in mind that the P-39 uses a symmetrical profile airfoil for most of the wing, and hence is going to produce a lower overall Clmax. By comparison the F6F uses the high lift NACA 5 digit series profile (which is similar to the 2R1 of the 109,) from root to tip, and thus as we see in the same report also generates a significantly higher Clmax than the P-39 at the same speeds (until ~0.6 mach) & altitude: That said the 1 G prop idle Clmax that they use for the aircraft in BoX might be correct, it's the power on Clmax at speed I'm curious about, esp. as compared with DCS for both aircraft.
  2. Well the landing speed I've seen for the real life K-4 was 150 km/h, so IL2's stall speed of 154 km/h gear & flaps down seems off, seeing as you don't land at, and certainly not below, stall speed. As for the gear & flaps up stall speed, I don't have a reference to compare it with, but in IL2 it appears very high. Now regarding the P-51 & power on Clmax, all I can say is that it should be around 1.3 @ 0.25 mach for the P-51 at low altitude, and as such most likely noticably higher for the Bf-109 at the same speed & altitude up until around 0.45 mach where the laminar flow profile resurges in Clmax. This is partly based on the direct comparison between the F6F & P-51B in NACA report TN1044, which shows the difference in Clmax vs mach we can expect between a fighter (F6F) using a similar conventional airfoil as the 109 (yet without slats), and one using the low drag type as on the P-51. And the difference is significant at the same altitude & speeds (flying speeds, mind you) where we have flight test figures for both. This in turn also checks out with what I've read others write regarding the F6F (& F4U) vs P-51B in USN testing, that is in terms of turning performance the disparity was significant despite a similar (F6F) to worse (F4U) wing loading than the P-51B.
  3. You're not making much sense now. You're effectively trying to make a case that the Clmax is correct at 280 km/h based on a 1 G (prop idle) stall speed measurement. Why would you do that if you already knew Clmax at 280 km/h (prop throttled) is going to be different?
  4. If Clmax was the same irrespective of speed and G load, then why do we have Clmax vs mach diagrams? As for what the exact Clmax should be at the respective speeds, power on, we don't have any exact figures for the 109. But we do have clmax vs mach figures for the P-51 vs aircraft using conventional profiles similar to that one the 109, and at the same altitude there is a marked difference. In short we can pretty safely assume that the 109's clmax between 0.2 to 0.5 mach is higher than that of the P-51. It seems like this was taken into account for the FM in DCS, but not IL2.
  5. Drag it out? There is obviously an issue. The main points raised so far is that the relative turn performance between the 67" Hg P-51 and 1.8ata K4 is incredibly different between IL2 and DCS. In DCS the 1.8ata K-4 performs substantially better than the 67" Hg P-51 in sustained turns (SL, 400 L fuel), as it should. Whilst in IL2 both aircraft are pretty much even, if not with a slight advantage to the P-51. The issue is wings level Clmax, i.e. low speed 1 G (& prop idle), is not going to be the same as the Clmax, power on, at dogfighting speeds
  6. Mhmm, but then what happens to your speed? A specific amount of thrust equals out the drag generated at a certain speed & lift coefficient (Ps=0). So if you increase thrust, but maintain the same bank angle and altitude, what happens? The answer is you keep gaining speed until you reach the next time drag & thrust reach equilibrium at a higher speed, G and rate. In other words if you got more thrust than what is generated in a level turn at Clmax (lift limit) and 280 kmh, then unless you deliberately stall your aircraft, you will accelerate until you reach the speed where drag again cancels out the thrust. So if an aircraft which can maintain 3 G at 280 kmh with 10000 kgf of thrust (random no.), with no altitude loss, but now gets its thrust increased to 12000 kgf (new Ps=0 now equal to old Ps=+xxx), it will now actually be able to both maintain 3 G at 280 kmh AND climb at the same time.
  7. Let me ask you all this: If at 280 kmh, and 3 G, thrust equals the drag generated (aka you can sustain said 3 G at 280 kmh with no altitude loss), then what happens if you further increase thrust? I hope you can see where JtD is coming from after thinking about this.
  8. 1) Did you notice the high altitude comparison? The F6F is achieving a higher Clmax at the same mach (higher even) at 25,000 ft than the P-51 is at 5100 ft. 2) 280 km/h = 0.234 mach, 300 km/h = 0.24 mach, 370 km/h = 0.31 mach at SL (also mach increases relative to TAS with altitude), 3) At 0.24 mach the Clmax is listed as 1.34 for the P-51 at 5100 ft, power on. Meanwhile the F6F reaches 1.35 at 0.35 mach and 25,100 ft, whilst at the same speed & altitude the P-51 reaches 1.12. (Both power on) What does this tell you? Also note the following:
  9. OR it means an increase in power doesn't improve the sustainable G/rate at the same speed ingame as it realistically should?? That's what he was saying: "If the Bf109K-4 does indeed not gain anything from the extra power, it is worth looking into airscrew efficiency, as suggested earlier. Unless it stalls at this speed." You would do yourself a massive favor if you actually read what others are writing before jumping to conclusions.
  10. Which is what he pointed out is a flaw in the simulation (!), and he is correct.
  11. Except the G load won't be the same, as the higher thrust allows a higher G load (and thus rate) to be sustained at the same speed (!!) You need to understand the difference between Ps & lift limit, sustained & instantaneous rate.
  12. The physics of what happens when you add thrust are always the same: Increase thrust and the Ps curve, within the lift limit, goes up. You can argue against this till your head goes blue, but you'd be arguing against the basic laws of physics. In short the only difference between a jet and a prop job in this case is that the shape of the Ps curve looks different as a prop loses efficiency with speed, hence the Ps curve starts off high from the lift limit curve and then falls off more sharply with speed as thrust actually decreases for the prop job. Where'as with a jet thrust often increases with speed due to ram effect. Calculated doghouse plot for a P-38 (green line is lift limit with flaps): Notice how the Ps=0 curve moves up (within the lift limit) with increases in power/thrust.
  13. It will. If you increase specific excess power (Ps) then you also increase the turn rate at the same speed up until you become lift limited. JtD is completely right about this. If you take a look at the below dog house plots you'll see the curves listed Ps = x. Ps = 0 is specific excess thrust equal to the drag generated in a level turn with no loss in altitude (refered to as max sustained turn rate) Ps = -400 is specific excess thrust PLUS gravity's help in a 400 ft/s diving turn (same effect as increasing thrust) Ps = +400 is specific excess thrust MINUS gravity's help in a 400 ft/s climbing turn (same effect as decreasing thrust) F-15 A-10 In short these charts allows you to directly observe how an increase (or decrease) in thrust affects the sustained turn rate of an aircraft, and as you can see an increase in thrust will heighten the Ps curve, allowing for a higher G to be sustained at the same speeds up until the lift limit (Clmax, max instantaneous rate) is reached. If you in turn increase the Clmax, then you move the lift limit curve to the left. Now if you instead increase wing area, you move the whole doghouse plot to the left. (Hence why aircraft size matters) No, it doesn't. I already told you under what condition the 1.4 figure applies, and it isn't the scenario we're discussing in this thread = dogfighting speeds & loads. Similarly the 1.4'ish figure for the 109 is for a prototype with a completely different wing and no slats, and again at wind tunnel speed and 1 G. No it's actually with the 109 carrying 12 liters more (400 vs 388 L).
  14. No, no evidence to support you claim has been presented. Even Holtzauge's graphs, using a similar Clmax (which I disagree with), show a 1+ sec advantage in the K-4's favour with 1.8ata vs 75" Hg and same fuel load. Which is the exact reverse of the representation in IL2. So I honestly don't know why it is you keep believing he is endorsing your misled views.
  15. According to what source exactly? Do you have a source for the Clmax of the 109 & P-51 at dogfighting speeds, under G load, and power on? If so please share it. Remember that a Clmax of 1.4 for the P-51 is at very low speeds and power off, where'as the advantage of conventional airfoils is in lift production under load at the typical flying speeds of prop jobs. It's two very different scenarios. On the contrary available evidence suggests the Clmax of the 109 should be noticably higher than that of the P-51, power on, at the typical dogfighting speeds, and this is only further backed up by pilot testimony in regards to how these two aircraft compare under those conditions.
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