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Venturi

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About Venturi

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    "Now the chief limitation (apart from mechanical ones) was detonation at high boost pressures." A.C.Lovesy, Rolls-Royce

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  1. Bomb effectiveness drops non-linearly and rapidly with range. Buildings are surprisingly resilient. This is why firebombing was performed after HE bombs. The fires did far more damage than the bombs.
  2. May I suggest, https://ww2aircraft.net/forum/threads/data-base-japanese-aircraft-engines.19466/page-12
  3. The outer 2 gun barrels visibly move on the mustang. https://m.youtube.com/watch?v=niJ82YCiuYU
  4. Hello, the M2 Browning uses a long recoil lockup system, and as such, the barrel ought to recoil during firing. You can look out the window and see the barrel tips protruding past the barrel tubes on at least the P-40 and P-51. These do not move while firing. i would recommend as a possible enhancement to the in-cockpit experience, to model barrel recoil on these weapons where the barrel is normally visible. Also, independent rates of fire for each weapon is recommended.
  5. Yes. Allison was making sure that it didn't have problems with the engines. Think about any manufacturing company which provides a warranty. They have specific parameters for operation, above which they no longer honor the warranty. Allison was being safe (from their perspective) with conservative power ratings for their engines. While this certainly makes sense in peacetime aviation, a different calculus is required in wartime. Remember, the Brits had been at war for three years by Dec 42, and they also had extensive aerial combat experience - reflected in their different operation of the engines as shown in the memo. What this memo proves, by Allison's own statement, is that they were being overly conservative in their ratings for the V-1710 F3R/F4R. They were concerned that the crews in the field, used to ignoring their conservative guidelines on the F3R/F4R, would also ignore the Allison guidelines on use of the new model of engine they were producing, which would result in ACTUAL severe damage. This has been hashed out before in old threads. It would be nice to see it implemented. The historical performance of the P-40 and P-39 (and P-51A) - as used by the British and the Soviets in particular - really was not based on the "official Allison guidelines" but rather on what the pilots could pull on planes that were heavier and had poorer altitude performance than their German and Japanese counterparts at that point in the war. In my opinion, the pilots used around 55-60" of manifold pressure, given high PN fuel that was supplied - 100/130 at this point in the war. In fact, as shown elsewhere, when Allison installed a manifold pressure regulator in these aircraft (sometime after 1943, long after the P-40E was a prime "front-line" fighter) they magically uprated the engine to 5min at 56" MAP. There is difficulty in using the engine in the P-40E correctly in the game for two reasons. 1, manifold pressure changes dynamically with altitude. This makes constant adjustment of the throttle necessary as you climb or dive, to maintain a consistent MAP. 2, the varying RPM of the engine affects manifold pressure. This is partially modeled correctly by IL-2 GB. As shown in the sim, when you are above critical altitude for the engine, increases in RPM (assuming wide open throttle) will increase the MAP. However, below critical altitude, IL-2 GB models this incorrectly. What should occur is that with a fixed throttle, increases in RPM should REDUCE MAP, not increase it. You will find that IL-2 GB simulates this incorrectly.
  6. You can also book a flight in a P40... ...by the way. Increasing engine RPM while maintaining same throttle should REDUCE MAP as long as critical altitude for a given RPM has not been reached. This occurs because there is a pressure drop behind the throttle butterfly in the intake tract, as long as the throttle is not wide open.
  7. My only consideration is accuracy. Yes, the P51 was much faster and far better at altitude. That should be the case. But the rest of this discussion is not about speed or endurance.
  8. Additional consideration should be made to the relative weights of the differing Allied aircraft as well as their power to weight ratios and their historical reputations. The Allison V-1710-39 of the P-40E for instance was later rated to run higher MAP (with manifold pressure regulator installed) without actual mechanical change of the engine itself. This would have given it approx 1500hp (1470) at WEP. The P51 for instance did not have a significantly higher HP rating, and if you look at the wing section and planform, it was less ideal than the P-40E for dogfighting. It had a significantly slower roll rate than the P-40E. The P-51 also weighed more, which would have increased induced drag. So you tell me... ...was the historical bad reputation of the P-40E actually based largely on it having a single stage, single gear supercharger and thus poor high altitude performance, compared to its European contemporaries which had already moved to high altitude supercharger configurations? I would suggest that when flown to later war power levels and under 10,000 feet, the P-40 easily outperformed the P-51 in a dogfight.
  9. Weight is important in aerodynamic turning performance, insofar as it creates lift-induced drag. A higher wing loading will create more drag at a given angle of attack than a lower wing loading, at equal aircraft weights. This is simplistic as wing planform matters a huge amount, too. There is a lot more than that which creates drag penalties, though... airframe drag at high angles of attack are very significant. Up to 50% of the drag according to aeronautical engineer friends. There is also no easy way to calculate these since there is no “table” of aircraft planform drag at differing angles of attack, unlike wing cross-sections. It does not matter for constant turns because the drag can be treated as being a fixed quantity in the equations, and cancelled out. However in combat it is the preservation of energy which is critical and this is a huge grey area. I have no idea how the engineers who make the simulation have modeled this, but others have tried to come to some empirical conclusions about the relative values of this using data in the sim, like JtD’s thread. The problem is that when the data is not published or disseminated, then it can be changed as engineer concepts of the aircraft’s performance, or as changes in other areas of the aircraft’s modeling change. I am not saying that is happening, what I am saying is that it is a black box that is open to interpretation
  10. Yeah the E4 weighs less but, it also has a lot less wing area. Recommend some consideration about instantaneous turn rate vs continuous. Also consideration to the relative weights of P-40, P-39, and P-51. As much as some people like to think, it is not the only factor in airplane performance. Yes Soviets had MUCH worse avgas in 1941/2. however we are modeling optimal considerations in the sim
  11. Glad to see we get the inverse square law at last.
  12. Nice job. All that work to line up a shot, it will be fun to see realistic results.
  13. The turbo is not parasitic unlike a sc, but it does rob exhaust gas pressure/thrust. If IL-2 were to model engines accurately, any throttle+turbo setting which gave you 100% allowed manifold pressure and no more, while retaining wide open throttle, would be the most efficient. Any throttle butterfly, when partially closed, induces by design a pressure drop behind it in the intake tract, which will need to be compensated for to achieve desired manifold pressure by increased turbo speed - and thus less exhaust thrust at altitudes above 1km or so. Optimum efficiency is achieved with WOT above SC critical altitude, and manage turbo speed as necessary to achieve desired MAP. If we were in the real world.
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