1. #1
    I dont get it, everytime I go into a dive from about 10,000ft and reduce the prop pitch down to %10, and try to pull out from 2,000 feet up, the controls dont respond and I fly straight into the trees.

    IS there something wrong with the game, the p38, or is it the pilots fault that I keep crashing into the ground from a steep dive in my p38?

    I notice that I seem to have to hit above 500mph for it to happen, but have only done it 2x.
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  2. #2
    JtD's Avatar Senior Member
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    The P-38 has extremely heavy controls at high speeds. You need to trim up a lot if you want to pull out from this low.

    Why do you reduce prop pitch to 10%?
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  3. #3
    It was a real life issue with the P-38. Once it had reached a certain speed compressiblity became a major life or death issue. The shockwave would disrupt the airflow flowing over the horizontal stabilzer and it couldnt get enough airflow over it to pull you out. Later p-38's had dive recovery flaps (Dive break key in sim) to help you recover.

    The Luftwaffe exploited this weakness knowing that a P-38 wouldnt follow in a steep dive.
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  4. #4
    mortoma's Avatar Senior Member
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    Pop your combat flaps and that also will help you recover in the early J model P-38. In the later models you have an air brake, which is a Godsend.
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  5. #5
    AndyJWest's Avatar Senior Member
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    This topic has been discussed in forums before, I think.

    IL-2 Compare gives the max dive speed (VNE in pilot-speak) as 820 km/h for th P38-J and 880 km/h for the L models. A quick check on the QMB shows that nothing falls off at that speed, at least at low level (I was starting at 5000m and diving fairly shallowly on full power). The problem is that (a) there is a marked pitch down effect as speed increases, which needs to be trimmed out, and (b) the control effectiveness reduces markedly. I don't know how IL-2 Compare derives its figures, but they seem reasonable to me, in that dive recovery will be so sluggish. Diving at full throttle at VNE is probably safer than throttled back, simply because to stay within the limit, the dive will have to be shallower. Don't know whether it is good for the engines though.

    I'd forgotten about the dive brakes myself, and haven't tried combat flaps: in my tests (J & L Late only) I recovered ok without. You could maybe also try sideslipping to slow down a bit though I haven't tried it.

    I think I'll do a few more tests, simply because I've been flying P38s quite a bit lately, and ought to know for sure what I can get away with
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  6. #6
    Originally posted by Superjew1:
    a dive from about 10,000ft,

    the controls dont respond

    IS there something wrong with the game, the p38, or is it the pilots fault

    it is the game

    despite the fact that it would happen to every WWII type, Oleg saw fit to add compressability to the P 38 only

    the compressability he put on it, at that, is complete hogwash, IRL the P 38 could not reach its critical mach speed in dives started below 20,000ft
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  7. #7
    Originally posted by Daiichidoku:
    <BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Superjew1:
    a dive from about 10,000ft,

    the controls dont respond

    IS there something wrong with the game, the p38, or is it the pilots fault

    it is the game

    despite the fact that it would happen to every WWII type, Oleg saw fit to add compressability to the P 38 only

    the compressability he put on it, at that, is complete hogwash, IRL the P 38 could not reach its critical mach speed in dives started below 20,000ft </div></BLOCKQUOTE>

    And the 109, don't forget the 109...
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  8. #8
    In a previous post there was discussion about compressibility and how its seldom modeled properly in games.
    One flaw that i see in many sims is that they cut out or limit elevator control as soon as the plane reaches its critical mach, but the reality is that the plane would need to go a bit faster for the shock wave to be big enough to engulf the air going over the elevators. Most planes would shutter and buffet, and have trouble with controlling ailerons before experiencing loss of elevator control, but i'm not sure if there was an exception with the P-38.
    It is also a gradual effect on control surfaces not an on and off phenomenon.


    Another flaw i see is the altitude and the degree the compressibility effect is modeled.
    It is related to altitude and speed, and generally you need to be going faster at lower altitudes to have a similar effect, however at lower altitudes there is also more air pressure against the control surfaces. This is a double edge sword, meaning that compressibility effects can be more severe at lower altitudes, but also easier to recover from, provided the plane isn't damaged.
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  9. #9
    AndyJWest's Avatar Senior Member
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    I'm not sure it is compressability as such that is modelled, more that at those speeds, the P38 has negative pitch stability: as it speeds up, the nose goes down. This can catch you out in other fast aircraft in the sim, though the P38 is possibly the most notable example.

    I did a few more tests, and starting from 10000m in a shallowish full power dive, you will get marked buffeting as you get to VNE, and structural failure will occur if you go much faster. I got lucky once, though - the elevator fell off, and the aircraft pitched up into steep climb, slowing enough for a bailout. I suspect that which failure occurs is probably random, or at least not easily predicted, but whatever happens, it is unlikely to be pleasant.

    I am assuming that the speeds given by IL2 Compare are indicated airspeed, rather than true airspeed, though in any case, the buffeting is always a clue that you are going too fast for safety. It takes time to learn the quirks of an aircraft, and I'd rather have a plane that does this, than one that spins if you sneeze (no names here, I don't want to offend the Pxx pilots)
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  10. #10
    Originally posted by RegRag1977:
    And the 109, don't forget the 109...
    compressability not modeled on 109s

    only P 38 and B1 rocket
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