P-38 Bugged

Discussion in 'Engineering Retrospective' started by -ALW-, Jan 25, 2003.

  1. -ALW-

    -ALW- Well-Known Member

    Joined:
    Dec 1, 2001
    Messages:
    2,086
    Location:
    Minot, North Dakota, USA
    I'm sure there are some out there. I'll refer to the one I have for the moment. If someone does find another, I think we'd all like to see it.
     
  2. -ALW-

    -ALW- Well-Known Member

    Joined:
    Dec 1, 2001
    Messages:
    2,086
    Location:
    Minot, North Dakota, USA
    Well, here is what you're looking for maybe?....
     

    Attached Files:

  3. -ALW-

    -ALW- Well-Known Member

    Joined:
    Dec 1, 2001
    Messages:
    2,086
    Location:
    Minot, North Dakota, USA
    Here is some information. I don't know if this will be useful, but all my info is coming from a P-38 Lightning "Pilot's Manual" issued by the AAF which stresses the performances of differing loads and how they affect the aircraft. There seem to be many variations concerning HP ratings, but I think these are accurate.
    What I want to do here is show the differences in HP ratings with and without War Emergency Power (WEP)

    Copied verbatim....
     

    Attached Files:

    Last edited: Apr 28, 2003
  4. -ALW-

    -ALW- Well-Known Member

    Joined:
    Dec 1, 2001
    Messages:
    2,086
    Location:
    Minot, North Dakota, USA
    Specific Engine Flight Chart P-38J & F-5B_1.jpg
     

    Attached Files:

  5. -ALW-

    -ALW- Well-Known Member

    Joined:
    Dec 1, 2001
    Messages:
    2,086
    Location:
    Minot, North Dakota, USA
    Specific Engine Flight Chart P-38L_1.jpg
     

    Attached Files:

  6. -ALW-

    -ALW- Well-Known Member

    Joined:
    Dec 1, 2001
    Messages:
    2,086
    Location:
    Minot, North Dakota, USA
    If no-one noticed, I'll mention to take note of the WEP HP settings.
     
  7. Comet-

    Comet- Well-Known Member

    Joined:
    Aug 7, 2002
    Messages:
    142
    Location:
    Prague, CZ
    And here we go again. Sorry for not answering. That manual is not mine, so I can hardly say anything about that. I don't know rules of that website.

    This aircraft definitely catched my atention. Nearly every source states exceptional manouverability and stability of this aircraft at low speeds, especially compared to the other american aircrafts and also german aircrafts. Both Americans and Germans were sure that at lower speed, P38 outturned and outmanouvered 190 and 109 without much problems. P38 pilots even used CLIMBING SPIRAL to the right against 109, which was simply UNABLE to follow....(that was surprising, compared to WB FM. But then, with minimal torque effect in WB it isn't much surprise...)

    Fact that this underdog, how Galland called it, was able to escort bombers deep into the Germany in the middle of war, nearly everytime and everywhere facing with huge numerical superiority of axis aircrafts (and also Luftwaffe's pilots at their peak), and still managed to rack 5:1 kill ratio in ETO (deep in the enemy territory), even with very poor training level of its pilots, that speaks something about this plane. Its 20:1 kill ratio in PTO and fact, that it killed more japanese aircrafts than anything else, is again something very impressive.

    And it is so hard to find reliable data... British tests are nearly useless, they didn't even bother to run it at full power. And in USA there was huge political pressure against this a/c...

    ----

    Hohun: thx for explanation, I had little trouble with understanding, how to read it.

    Alw: Yes, those charts are nice, too bad that climb times are only for military power :(



    ---

    There is problem I found with power ratings of Allison V1710F-30, mounted in the L model.

    Most "ordinary" sources are publishing 1600 HP for WEP settings (60 manifold, 3000 RPM). But there is one source claiming that real power of Allison engine was 1725 HP, and it was confirmed by Lockheed's tests, and 1600HP was a error many authors copied.

    Same source is claiming, that max speeds from the Lockheed factory tests for P38L were:

    Max speed at sea level: 352 mph
    Max speed at 5,500 ft : 369 mph
    Max speed at 23,500 ft. 440 mph (WEP) 5 minutes max.
    Max speed at critical alt: 444 mph @ 25,800 (WEP) 5 minutes max.

    ----

    With turbochargers with improved cooling, it is definitely very dangerous aircraft for high altitudes, 25k+. Having nearly same HP available at 30k as at surface level is crazy, mechanical superchargers of P51 (and 109 wasn't better, I assume) weren't even in the same class. Only P47 was close.

    What was power rating of 109K above 25K? MW50 should lost its effect at this altitude, that was task for GM-1, but 109 wasn't equipped with both systems at once?
     
  8. HoHun

    HoHun FH Beta Tester

    Joined:
    Sep 22, 2001
    Messages:
    2,643
    Hi Comet,

    >But there is one source claiming that real power of Allison engine was 1725 HP, and it was confirmed by Lockheed's tests, and 1600HP was a error many authors copied.

    This source probably is "CC Jordan"? He's a great P-38 lover, but I'd not use anything he wrote for verifying flight models.

    >With turbochargers with improved cooling, it is definitely very dangerous aircraft for high altitudes, 25k+. Having nearly same HP available at 30k as at surface level is crazy, mechanical superchargers of P51 (and 109 wasn't better, I assume) weren't even in the same class.

    Actually, at 30000 ft, the mechanically supercharged V-1650 of the P-51B gave virtually the same power as each of the P-38J's turbocharged V-1710s. The P-51D had an engine with lower full-throttle height, but my point is that mechanical superchargers were indeed in the same class as turbos :)

    Another thing to take into account is exhaust thrust which was close to zero for the P-38. The Jumo 213E (Ta 152H) for example yielded exhaust thrust equivalent to about 400 - 500 extra HP at the propeller shaft (at top speed). So the P-47D with 2300 HP @ 30000 ft was not so far from the Ta 152H with 1630 shaft HP at the same altitude - it was more like 2300 vs. 2100 HP, with the Ta 152 being much smaller and lighter as it didn't have to carry a turbo supercharger.

    There are advantages and disadvantages of both technologies, and I don't think any of them was superior in WW2.

    >What was power rating of 109K above 25K? MW50 should lost its effect at this altitude, that was task for GM-1, but 109 wasn't equipped with both systems at once?

    Good point! The Me 109 is often considered a high-altitude aircraft, but actually it was best at medium altitude. It's low weight helped its performance higher up, and in the thin air there was no control heaviness anymore, but the engine wasn't really optimized for it.

    Regards,

    Henning (HoHun)
     
  9. Comet-

    Comet- Well-Known Member

    Joined:
    Aug 7, 2002
    Messages:
    142
    Location:
    Prague, CZ
    Hi Hohun,

    yes, it was from C.C. Jordan, is he that "famous"? . It looked to me a bit too optimistic, thats why I posted it here to see how close or far from the truth it was.

    I thought it was something similar to Isegrim's posts about 109, or Skychimp's posts about other american aircrafts (p51, p47), but I was probably overwhelmed by his positive attitude :)))).

    And I forgot about the thrust again....damn! :)
     
  10. HoHun

    HoHun FH Beta Tester

    Joined:
    Sep 22, 2001
    Messages:
    2,643
    Hi Comet,

    >yes, it was from C.C. Jordan, is he that "famous"?

    I witnessed a discussion on rec.aviation.military a while back where some very knowledgable guys debated the issue with Jordan. It was a fight that raged for weeks, and in a nutshell, it turned out that the best top speed of the P-38 as quoted by Jordan was never actually achieved in flight and the engines bench-tested at the high powers he claimed for the P-38's Allisions suffered internal damage (which he knew when posting the figures). So I just don't use his data anymore :-(

    >And I forgot about the thrust again....damn! :)

    As a rule of thumb, the DVL (Germany's NACA/TsAGI equivalent) concluded that turbochargers had an advantage at low speeds and with regard to range, while mechanical superchargers had an advantage at high speeds.

    The message was to use turbochargers for bombers and mechanical superchargers for fighters :) As Germany didn't manage to mass-produce turbo-superchargers, this advice remained mostly academical though.

    Regards,

    Henning (HoHun)
     
  11. -ALW-

    -ALW- Well-Known Member

    Joined:
    Dec 1, 2001
    Messages:
    2,086
    Location:
    Minot, North Dakota, USA
    Well, what about the ME262 engines?? How reliable were they and how long did they ACTUALLY last? They (WBFH) don't model any aircraft defects so that shows to me that would not be an issue.
    :dunno:
     
  12. -ALW-

    -ALW- Well-Known Member

    Joined:
    Dec 1, 2001
    Messages:
    2,086
    Location:
    Minot, North Dakota, USA
    And look what I posted above previously.
    I think this data is what we should use. What would it hurt to go with original data?
     

    Attached Files:

    • p38.jpg
      p38.jpg
      File size:
      41.2 KB
      Views:
      235
    Last edited: May 24, 2003
  13. HoHun

    HoHun FH Beta Tester

    Joined:
    Sep 22, 2001
    Messages:
    2,643
    Hi ALW,

    >They (WBFH) don't model any aircraft defects so that shows to me that would not be an issue.

    By that logic, you could increase the powers of all of the Warbirds aircraft since the P-38's Allisons were far from the only ones to be run at increased power in a bench test. (Many other engines were, often even without defects.)

    Pretending that these bench test powers would be representative for operational duty is quite misleading.

    But as you have quoted the same 1600 HP/60" Hg power values I'd have used, we're in agreement anyway :)

    Regards,

    Henning (HoHun)
     
  14. -ALW-

    -ALW- Well-Known Member

    Joined:
    Dec 1, 2001
    Messages:
    2,086
    Location:
    Minot, North Dakota, USA
    That is true, I wouldn't go by bench tests in any case because you're at only one altitude (ground level). Your situations up at higher altitudes in my view would allow for short periods of excessive rpm's for example. The fact that those engines are under load during combat would make me think that it is allowable. It's like revving an engine in your car. If you rev it too high for too long, you will damage it. On the other hand, if it is under load, that problem is not the case. That is the reason I think you see the differences in rpm's and hp at those alts.
    Thanks for responding.
     
  15. HoHun

    HoHun FH Beta Tester

    Joined:
    Sep 22, 2001
    Messages:
    2,643
    Hi ALW,

    >Your situations up at higher altitudes in my view would allow for short periods of excessive rpm's for example.

    Actually, bench tests were conducted in pressure chambers so that high altitudes could be simulated, too.

    As WEP could be sustained for 5 min, any higher power setting could have been sustained for less than that - again, this is the same for other aircraft, too.

    Note the three-stage power settings - WEP (5 min), MIL (15 min), continuous (well, continuous :) In Warbirds, we have only two power settings available - WEP and 100% - and usually, 100% is implemented as MIL. This actually works out as an advantage for a plane with short MIL period like the P-38 - it gets 1425 HP continuous instead of just 1100 HP. (Other fighters may have 30 min or even 60 min of MIL available in real life).

    Regards,

    Henning (HoHun)
     
  16. Comet-

    Comet- Well-Known Member

    Joined:
    Aug 7, 2002
    Messages:
    142
    Location:
    Prague, CZ
    Hi HoHun,

    well, 15 minutes was official limit from the factory...that is far from from how long that plane can run on MIL or WEP settings in reality. In this point I believe pilot's accounts. Especially when they could run on WEP settings for far more than 5 minutes (20 minutes wasn't exception). Better reduced life of engine than lost aircraft.

    It depends on altitude, speed, condition of the engine, possible damage. But that requires complete simulation of the engine system...

    ---

    It would be nice to see our FH aicrafts cruising at CRUISE velocity and not at MIL power all the time.
     
  17. HoHun

    HoHun FH Beta Tester

    Joined:
    Sep 22, 2001
    Messages:
    2,643
    Hi Comet,

    >well, 15 minutes was official limit from the factory...that is far from from how long that plane can run on MIL or WEP settings in reality.

    Again, the same is true for other planes, and if you start with a 30 min MIL allowance, chances are that you can sustain higher power for longer than starting with the P-38's 15 min allowance. (Not to mention MW50.)

    The official power limits were carefully selected, and adjusted if too many engine failures occurred. Accordingly, they're representative of the tactically sensible maximum power.

    If we'd include the possibility of "breaking the rules" in Warbirds, that would affect all planes, and it would be quite a nuisance gameplay-wise since the guy who's fighting in gliding distance of his airfield would always fly at greater boost than his opponent.

    If you ask me, we're flying too much at WEP in Warbirds even now, not too little :)

    Regards,

    Henning (HoHun)
     
    1 person likes this.
  18. Red Ant

    Red Ant Well-Known Member

    Joined:
    Jan 18, 2002
    Messages:
    4,917
    Location:
    Germany
    Your conclusion is equally flawed as your numbers. First off, the normal combat weight for the P-38L is around 17,500 lbs (that translates to roughly 7,730 kg). Empty weight is 14,100 lbs by the way. Secondly, the L's V-1710-111/113 engines have a maximum power rating of 1,600 hp each (with war emergency power). After all you gave the 190A8 its WEP-rated power output (with MW 50 boost even!), so it's only fair to treat the 38 the same. Therefore the recomputed numbers are as follows:

    P-38L
    Power rating: 3,200 hp
    combat weight: 17,500 lbs ( 7954 kg )
    Wing area: 327.5 sqft ( 30.41 sqm )
    Power loading: 5.47 lbs / hp ( 2.49 kg / hp ) = 121.5 percent of the Focke Wulf's value
    Wing loading: 53.44 lbs / sqft ( 261.56 kg / sqm ) = 111.3 percent of the Focke Wulf's value


    Fw-190A8
    Power loading: 2.05 kg / hp
    Wing loading: 235 kg / sqm

    Yes, the numbers still speak in favor of the 190. The thing is there are other factors that also need to be taken into account. If comparing planes to each other was simply a matter of comparing T/W ratios and power loadings then the Su-27 would never be able to turn inside an F-16 because with a power loading of 92 kg / kN and a wing loading of 423 kg / sqm the F-16 clearly has the better stats ( 124.4 and 492 for the Su-27 Flanker B), yet the Flanker is generally thought to have a sustained turn equal to or slightly better than that of the Falcon. Wing shape and thickness, drag at low and high angles of attack and tons of other factors also play an important role here.
    Anyway, the counter-rotating propellors have already been mentioned and are an advantage for the P-38. Also the P-38's wing aspect ratio of 8.3 is considerably better than that of the Focke Wulf at 6.0. Furthermore the P-38L's fowler flaps greatly increased lift when deployed, thereby shifting the equation further in the Lightning's favor.

    http://www.simhq.com/_air/air_002b.html
    If anyone here seriously thinks a Lightning would be "doomed" in an encounter with a Fw then I have a bridge to sell you. :rolleyes:
     
  19. PressLuftHammer

    PressLuftHammer FH Beta Tester

    Joined:
    Mar 5, 2003
    Messages:
    13,855
    Location:
    Ekaterinburg (Russia)
    Certainly there are also other factors first of all it is the maximal factor of elevating force Clmax it depends basically from airfoils. for example Su-27 Clmax=1,6 for F-16 Cyl=1,1 But at Fw.190A and P-38 identical airfoils NACA230 therefore here P-38 advantages has no. His unique advantage the greater lengthening of a wing.
     
  20. -ALW-

    -ALW- Well-Known Member

    Joined:
    Dec 1, 2001
    Messages:
    2,086
    Location:
    Minot, North Dakota, USA
    After having been away for such a long time I missed some things. When I came back after nearly 2 years away...I saw there was an update to WBFH. When I checked what was updated, I didn't see much. BUT, to my amazement and pleasure I had the opportunity to once again fly the P-38 I once knew :D. Thanks to the developing team for keeping WarBirds fun and interesting! I don't know if they listened to my rantings finally or what, but it's great to be back in the seat again! I've been flying here again for the past several months. I'll see whomever I recognize and say hello to old friends again!