Please correct the P40b!

Discussion in 'Warbirds International' started by --stec, May 17, 2002.

  1. rgreat

    rgreat FH Developer

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    You know any more significant factors ? :)
    Amount of Lift are greatly depends on WingArea.
    There WingLoading is plays its role.
    Keep in mind i dint say that WingLoad are ONLY factor.
    I just say its a moust significant factor.
    Why? Becouse other parameters in real ww2 planes didnt differ to much to swap less maneuverable and more maneuverable planes.

    I hope you can understand my poor english right. :)
     
    Last edited: May 20, 2002
  2. niklas

    niklas Active Member

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    rgreat, at the end it´s lift what is the most import factor. lift is a linear function of wingarea, and also a linear function of lift-coefficint which is in turn a linear function (ok, almost) of AoA. So high AoA is AS important AS wingarea for lift.

    btw, the Spit had a surprisingly low lift coefficient - lot of wingarea, though.

    I did a quick search on the net:
    From http://www.acepilots.com/planes/p40_warhawk.html

    Joel Paris was a P-40 ace with the 49th Fighter Group in the Southwest Pacific. In Fire in the Sky: The Air War in the South Pacific, he relates his opinion of the P-40:
    >>
    I never felt that I was a second-class citizen in a P-40. In many ways I thought the P-40 was better than the more modern fighters. I had a hell of a lot of time in a P-40, probably close to a thousand hours. I could make it sit up and talk. It was an unforgiving airplane. It had vicious stall characteristics. ...
    If you knew what you were doing, you could fight a Jap on even terms, but you had to make him fight your way. He could outturn you at slow speed. You could outturn him at high speed. When you got into a turning fight with him, you dropped your nose down so you kept your airspeed up, you could outturn him. At low speed he could outroll you because of those big ailerons. They looked like barn doors on the Zero. If your speed was up over 275, you could outroll it. His big ailerons didn't have the strength to make high speed rolls ...
    <<

    Outrolled by a Zero at speeds below 275mph, i&acute;d say either the wb-zero rolls to slow or the P40 too fast.

    From a P-40 handbook: http://www.danford.net/manual3.htm
    >>
    STALLING
    15. The stalling characteristics of this aircraft are good. At minimum speed the stall is gentle and there is some buffeting and pitching before the wing, generally the right, drops gently, followed by the nose.

    At high speed the machine can be stalled as a result of the coarse use of the elevators producing high acceleration loadings, but due warning is received, particularly on the high speed turn, by a shuddering of the aircraft, and loads of over 5g. can be applied to 180 to 200 m.p.h. without the aircraft stalling.

    The stalling speeds of the aircraft at normal operational loads, were as follows:

    Undercarriage up and flaps up - 80 I.A.S.
    Undercarriage down, flaps up - 82 I.A.S.
    Undercarriage up, flaps down - 73 I.A.S.
    Undercarriage down, flaps down - 75 I.A.S.
    <<

    One has to take into consideration that IAS at high AoA is too low, so actual "true" IAS is higher. But obviously this info was used for the P40 in WB.
    Furhtermore it&acute;s a tomahawk I manual, and the tomi I had a gross weight of only 6787 (http://home.att.net/~jbaugher1/p40_2.html)
    The P40B had more weight, , 7326 pounds gross, http://home.att.net/~jbaugher1/p40_4.html
    Isnt&acute;t it funny that the official manufactor handbook speaks about gentle stall characteristics while the pilot you did fly it calls it an "unforgiving plane" with "vicious stall characteristics"?....

    niklas
     
  3. Red Ant

    Red Ant Well-Known Member

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    Niklas, another question if you don't mind. What is the lift coefficient? Judging from the word coefficient it sounds like some multiplier. Or is it the amount of lift generated by the plane's fuselage as opposed to its wings?
     
  4. Vadim Maksimenko

    Vadim Maksimenko Well-Known Member

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    Well, well, here experts come ;) Wingload is similar, but power load of 109 is just 76% of P40. That means only one: in equal turn P40 should loose 24% more energy than 109. Add here higher drag of P40 airframe (compare wing area at least: at the same AOA P40's wing produces 26% more drag than that of 109) and watch the result. We see here "playability" that rendered flight phisics a nonsense. :(
     
  5. -nicae-

    -nicae- Well-Known Member

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    gimme one of those! :p
     
  6. rgreat

    rgreat FH Developer

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    P40C turn time = 18 sec
    P40E turn time = 19.2 sec.
    IRL
     

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  7. devill

    devill Well-Known Member

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    We got ourselves a real mistery here guys, a?

    Wait until thursday, I'll ask my Aerodynamics professor about this.

    :znaika:
     
  8. mish

    mish Member

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    Speaking about sustained turns of 109's


    Let's collect some evidences.

    Bf 109b

    This plane was extraordinary good turner. Comparative tests showed that 109b could turn with even less sustained turn radius than I-16 (type 10) .

    Bf 109E

    I have no evidences that 109E could get sustained turn time better than 24 sec.
    So the question is what had happened to 109E comparing to it's predecessor 109B.
    From my point of view 109E had some aerodynamics problems, especially with slats openning (they opened too early).
    The point is that 109E could not get a good sustained turn time if the slats got opened (to much drag/too low speed). And if the pilot keeped 109E in turn preventing slats openning (higher speed/ bigger radius) it wasn't possible to get time better than 24 sec.

    Bf 109F

    109F got lots of improvements in aerodynamics and the problems with slats opening were fixed.


    Some conclusions:
    Unfortunatelly the FM of WB doesn't model the work of slats. That's why the 109E lose too mush E now while manoeuvring. That gives him real sustain turn time but provides unreal decreasing of it's overall manoeuvrability.
     
  9. devill

    devill Well-Known Member

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    Don't forget that Bf109Fs wing was a little different from Es.
     
  10. HoHun

    HoHun FH Beta Tester

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    Hi Devill,

    >What you just reffered to as "nonsense", came out from Mike Spick's book, and was confirmed as true by my college professor (teaches aerodynamic constructions at my university).

    I'd suggest that you try to post some verbatim quotes. If you rely on experts, it's generally a good idea to post a coherent sentence or even paragraph from that expert so that his point of view and his explantion are verifyable. What you've posted so far is not a good basis for further discussion, I'm afraid.

    Here's an example:

    "4 more flights were also conducted by Dr. Wurster on 26 August 1936. The task was to record departures in left and right turns with 'free' slats. The flight tests showed that the departure behaviour of the Bf 109 in turns and aerobatic flight was decidedly more docile ('wesentlich gutm&uuml;tiger') than with slats retracted."

    (From Radinger/Schick, "Me 109", on stall and spin trials with the Bf 109V1, W.Nr. 758 D-IABI.)

    The Messerschmitt stall and spin trials were exhaustive, spanning years and costing 2 million Reichsmark. The end result was the deletion of the mechanism for locking down the slats that had been installed in the V1 prototype.

    >>"Don't believe the P-40 is an American Spitfire - it weighs 30% more at the same power, and that's is a large difference."

    >Fine, but I was talking about Spit... :rolleyes:

    You were implying an analogy between the Spitfire and the P-40. I pointed out the difference.

    Regards,

    Henning (HoHun)
     
  11. HoHun

    HoHun FH Beta Tester

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    Hi Red Ant,

    >The 109 does have a significant power loading advantage over the P-40 (and it shows in the game), but in terms of wing loading the difference is very marginal at best. They are close enough together so that it comes down to aerodynamics (drag under medium AOA's and so on).

    >max takeoff mass: 3655 kg 2665 kg
    >wing loading : 166.7 kg/m^2 164.8 kg/m^2
    >power loading : 3.18 kg/HP 2.42 kg/HP

    As Niklas pointed out, the Me 109's and the P-40's wings are very similar. At very similar wing loading, the P-40 is able to generate the same G rate at the same speed - though it has to produce more lift to do so, lift is proportional to wing area.

    However, just as Vadim implied, drag is proportional to wing area as well.

    The result is that the P-40B flies the same turn as the Me 109 at 37% more drag (using your figures for the sake of the example). It does not have 37% more power, however.

    Accordingly, the P-40B should be able to keep turning with the Me 109 in an instantaneous turn. It should bleed speed faster than the Me 109, though. It should really run into problems in sustained turns, though - the Me 109 has about the same power as the P-40, but being lighter, it can get a tighter turn at the same drag.

    (Of course, the wings are not entirely identical. The Me 109's wing does not suffer from a loss of efficiency due to wash-out, and its automatic slats give it a lower corner speed which translates into superior instantaneous turning ability. On the other hand, the P-40B is lighter than the value you've provided, increasing its turn rate, too.)

    Regards,

    Henning (HoHun)
     
  12. HoHun

    HoHun FH Beta Tester

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    Hi Rgreat,

    Thanks for posting the numbers!

    I did a quick check against the P-40B in the game:

    real P-40C @ 1000 m: 445 km/h
    game P-40B @ 1000 m: 500 km/h (295 mph IAS)

    real P-40C @ 4860 m: 545 km/h
    game P-40B @ 4572 m: 582 km/h (285 mph IAS)

    (I chose 4572 m = 15000 ft since it seems to be the top speed altitude.)

    Any way I look at it, there seems to be something wrong with the P-40B.

    The P-40 really shouldn't be able to reach the same (or better) top speeds than the Me 109E on the same power. Just look at the P-40's landing gear bulges - these are bigger and poorer streamlined than Messerschmitt cannon gondola.

    (Unfortunately, I don't understand the Russian captions. Does the second footnote refer to the use of low octane fuel? I'd still consider the Warbirds P-40B too fast in comparison to the Me 109E, even considering that.)

    Regards,

    Henning (HoHun)
     
  13. devill

    devill Well-Known Member

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    >>I'd suggest that you try to post some verbatim quotes. If you rely on experts, it's generally a good idea to post a coherent sentence or even paragraph from that expert so that his point of view and his explantion are verifyable. What you've posted so far is not a good basis for further discussion, I'm afraid.<<


    If you really want me to do that, you'll have to wait a few days. I gave the book to a friend and he's out of town.
    But i don't see the point in doing that because you will not admit that you were wrong...

    I'll do it anyways.
     
  14. illo

    illo FH Beta Tester

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    Lets not make this any personal arguing contest.

    What we have to do is to find more data and solve FM problems if they exist.
     
  15. -nicae-

    -nicae- Well-Known Member

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    yes! master yoda, hear, you must!

    ermmm.. ok, so maybe illo's avatar isnt yoda after all... :dura:
     
  16. HoHun

    HoHun FH Beta Tester

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    Hi Devill,

    >If you really want me to do that, you'll have to wait a few days.

    I've got more patience to wait for good data than I have dealing with carelessly posted poor data.

    Regards,

    Henning (HoHun)
     
  17. devill

    devill Well-Known Member

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    CC Illo, I'm trying to get some more info on wings and aeroprofiles, and HoHun will get his quotation.
     
  18. HoHun

    HoHun FH Beta Tester

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    Hi Illo,

    >What we have to do is to find more data and solve FM problems if they exist.

    Actually, we've collected a number of points so far that need attention:

    1) Is the weight of the P-40B correct? (Net and gross weights)
    2) Is the power of the P-40B correct? (Power over altitude graph)

    (These have to be checked by Rgreat.)

    3) As Niklas pointed out, the P-40B stalled at 80 mph IAS, which due to position error of the instrument should work out as at least 85 mph (concluding from other aircraft, as the Tomahawk manual doesn't provide a position error calibration table). I made a quick test and found the stall speed of the fully loaded P-40B to be 75 mph IAS/CAS (IAS is equivalent to CAS in the game as far as I can tell).

    Though it may not seem much, a 10 mph advantage in level flight stall speed translates into a much bigger advantage under G loads.

    Even worse, the manual Niklas referred to might have been meant for a Tomahawk I instead for the 500 lbs heavier P-40B, which then could be expected to have an 83 mph IAS stall speed. That could mean the P-40B stalls at 75 mph in-game versus 88 mph (or more) in real life.

    4) The speed numbers for the P-40C Rgreat posted are 38 - 55 km/h lower than the speeds of the P-40B in the game. I don't know if there's something in the Russian caption that justifies this lower performance, but it's obvious that the P-40 would be a lot less dangerous if it were considerably slower than the Me 109E (as Rgreat's table suggests).

    These are just possible problems, and it may be that some (or all) of them turn out to be modelled OK. However, I think it's reasonable not to jump to conclusions without a thorough investigation.

    Regards,

    Henning (HoHun)
     
  19. devill

    devill Well-Known Member

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    Guys,

    What do you think about speeds of Bf109E and P40b and Spit Ia on the TAS page? Those are some really screwed up results: E4 is slower than P40 below 5000m and slower than Spit at all hights???
    Are those speeds from the game or from the data that FH used for making the models?
    Btw all speeds are moved to the left by 10-15 km/h at least!
     
  20. -nicae-

    -nicae- Well-Known Member

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    max speeds is not entirely of v1.42 yet.
    and it is done by in-game testing by breedr.