Bf-109 vs Spitfire vs Fw-190 vs P-51

Discussion in 'Aviation' started by Soren, May 26, 2008.

  1. Soren

    Soren Banned

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    First a little about turn performance, explained by Gene (Crumpp):
    Board Message

    And the methods for calculating drag lift:

    Lift (L) = Cl * A * .5 * r * V^2

    Coefficient of lift (Cl) = Established in windtunnel tests

    Drag (D) = Cd * A * .5 * r * V^2

    Drag Coefficient (Cd) = Cd0 + Cdi

    Induced drag coefficient (Cdi) = (Cl^2) / (pi * AR * e)

    Coefficient of drag at zero lift (Cd0) = Established in windtunnel tests

    Note: End results are in Newtons (N), so you'll have to convert into Kilogram force (Kgf).


    Then lets compare the specs of each a/c:


    [1]Bf-109 K-4

    Weight: 3,364 kg
    Wing area: 16.15 m^2
    Wing span: 9.92 m
    Wing AR: 6.09
    Wing Clmax: 1.70
    Cd0: ~0.021 ? (Cleaner than F, G)

    Engine power: 1,975 HP
    _____________________
    Lift loading = 122.5 kg/m^2
    Span loading = 339 kg/m
    Power loading = 1.7 kg/HP


    [2]Bf-109 G-10

    Weight: 3,200 kg
    Wing area: 16.15 m^2
    Wing span: 9.92 m
    Wing AR: 6.09
    Wing Clmax: 1.70
    Cd0: 0.023

    Engine power: 1,830 HP
    _____________________
    Lift loading = 116.5 kg/m^2
    Span loading = 322.5 kg/m
    Power loading = 1.74 kg/HP


    [3]Spitfire Mk.XIV

    Weight: 3,850 kg
    Wing area: 22.48 m^2
    Wing span: 11.23 m
    Wing AR: 5.61
    Wing Clmax: 1.36
    Cd0: 0.0229

    Engine power: 2,235 HP
    _____________________
    Lift loading = 125.9 kg/m^2
    Span loading = 342.8 kg/m
    Power loading = 1.72 kg/HP


    [4]Fw-190 Dora-9

    Weight: 4,270 kg
    Wing area: 18.3 m^2
    Wing span: 10.51 m
    Wing AR: 6.03
    Wing Clmax: 1.58
    Cd0: No data so far, any is welcome

    Engine power: 2,075 HP
    _____________________
    Lift loading = 147.6 kg/m^2
    Span loading = 406.2 kg/m
    Power loading = 2.05 kg/HP


    [5]P-51D Mustang

    Weight: 4,400 kg (Empty fuselage tank)
    Wing area: 21,64 m^2
    Wing span: 11.21 m
    Wing AR: 5.8
    Wing Clmax: 1.35
    Cd0: No data so far, any is welcome

    Engine power: 1,830 HP
    _____________________
    Lift loading = 150.6 kg/m^2
    Span loading = 392.5 kg/m
    Power loading = 2.40 kg/HP
     
  2. Kruska

    Kruska Member

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    Hello Soren,

    Turn performance: I am not a pilot myself but I had the chance several times, - almost puking myself half dead – and **** scared - to sit next to my uncle (IMO a very, very experienced flyer and former ww2 Luftwaffe pilot) mistreating his Cessna 172 or Beechcraft Baron like it was a Ju87 or F-104 diving into and around the Bavarian Alps. Jesus he would tilt and circle his a/c at 90 degrees angle for 6-7 360 degree turns which made me feel like half an hour and expecting the a/c just to drop down like a stone.

    The guy was a lunatic. No joke, many active G-91/F-104 pilots really refused to fly with him.

    He was using everything that could move in/on this a/c, pedals, steering, manually pumping the throttle, wind drafts and I think even his and my body weight.

    What I mean to say is, that if 2 extreme professional pilots run into each other, the turn performance on their a/c’s is actually “manipulated” or caused by entering into their preferable angles/degrees of flight maneuvers taking into account the “air feeling” around them that has more influence on turn performance then all this technical mathematical lift/drag/climax formula.

    Which normal pilots probably couldn’t even make use off, because they wouldn’t be lunatic enough – like my uncle – to get themselves into/above the limits of an aircraft.

    As I said I am not a pilot, but this is the way I felt it.

    Regards
    Kruska
     
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  3. starling

    starling Member

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    yes,well the 109 crashes a lot on take off and landing,the less said about 190 the better,the p 51 was an aircraft made to british specs,so the spit wins again.:lol: .lee.
     
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  4. DerAdlerIstGelandet

    DerAdlerIstGelandet Der Crew Chief
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    :rolleyes:

    Here we go again...

    Please post proof that the 109 crashes a lot on take off and landing.

    I want to see:

    1. Number of 109s (all models) that crashed on take off.
    2. Number of 109s (all models) that crashed on landing.
    3. Percentage of 109s (all models) that crashed on take off and landing.

    If you are going to make innacurate posts, then please back them up.

    Now having gotten past that part also please explain:

    1. What is so bad about the Fw 190?
    2. How is the Spit better than the P-51D? Sure the Spit is more maneuverable, but what good does that do if the Spit can not get to the battle because it does not have the range of the P-51D?

    If you post facts to back up your posts that is fine, but you are rather biased in your opinions and post nothing to back it up.

    And Soren, your link above does not work for some reason.
     
  5. parsifal

    parsifal Well-Known Member

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    Ho hun has a thread devoted to this particular subject. He has shown that the 109 suffered very little additional attrition in either landing or take off accidents, as compared to the 190.

    What I dont know is the attrition rate of both the german fighters compared with those of other nations. I would suspect, that as the pilot training standards dropped towards the end of the war, then the accident rate for all LW a/c would have risen

    I do know also that fighters used for Night Fighter operations suffered a high rate of attrition in landing accidents, for obvious reasons.

    None of this has anything to do with the narrow track landing gear, and none of it points to the 109 being an especially dangerous a/c to fly. its a complete furphy
     
  6. DerAdlerIstGelandet

    DerAdlerIstGelandet Der Crew Chief
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    Agreed parsifal...

    I am just getting tired of this guy posting the same thing: "yes,well the 109 crashes a lot on take off and landing" in every thread that has to do with the 109.
     
  7. Soren

    Soren Banned

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    You're right Adler, I forgot you have to be a member to see what is written on the forum. Anyway here it is:


    Turn performance can be derived from the following relationship:

    [​IMG][​IMG][​IMG]

    However as the USN Manual notes, this relationship is not corrected for thrust. Hence whenever angle of bank is changed, speed must increase and turns are limited by the same load factor. Radius will increase speed along with the rate of turn.

    An increase in thrust not only represents an increase in the aircrafts ability to overcome total drag:


    [​IMG][​IMG][​IMG]

    It represents an increase in lift:
    [​IMG]

    So while an increase in thrust directly effects the thrust limit of the EM diagram:
    [​IMG]

    It also influences the lift limit of the EM diagram.

    This mitigates or eliminates the radius increase that occurs when the effects of thrust are not considered in our first formulation. This would be limited by the airfoils CLmax that of course no fighter I am aware of in WWII could achieve in sustained maneuvering anyway.

    As Perkins and Hage states, turning ability stems from the fundamental relationship of Power Available to Power Required.

    This is why the P47's sustained maneuvering ability increased when it was fitted with the high activity propeller or the Spitfire Mk XIV was able to match the Spitfire Mk IX in sustained turn performance in spite of a 5 lbs wingloading increase.

    All the best,

    Crumpp
     
  8. parsifal

    parsifal Well-Known Member

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    Even though the statistics show no appreciable difference in the incidence of landing accidents overall, I confess I have read accounts to say that it was tricky to land because of the narrow track landing gear. Perhaps it may be true that for an inexperienced pilot there was a higher risk of landing accident??? Ho Hun did not show this. I strongly doubt that it is the case, but I guess it is worth at least looking into. I hate asking the question when little twirps like that are around, because they will pick up the comment, and use it for any purpose
     
  9. Soren

    Soren Banned

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    The 109 was tricky to land, but not because its landing gear was narrow, but because of the slight toe out of the wheels. Here's a little quote from Dave Southwood (Modern 109 pilot):

    The '109 floats like a Spitfire and controls are effective up to touchdown. After touchdown, directional control is by using differential braking. The three point attitude is easy to judge, and although it bucks around on rough grass it does not bounce significantly on touchdown. however, the landing is not easy. From approaching the threshold up to touchdown the forward view is very poor, and it is difficult to assess drift. if the aircraft is drifting at touchdown, the toe-in on the wheel towards which it is drifting causes a marked swing, and you are working very hard to keep straight and avoid a ground loop. Each landing is a challenge, and just a bit unpredictable. Hard runways have higher friction than grass surfaces, and so the wheels dig in even more if drifting on touchdown, making ground-loops more likely on runways than on grass. The possibility of drifting on touchdown increases with a crosswind, and so for these two reasons, we are only flying the Gustav off grass and with a 10kt crosswind limit. I have flown the Buchon off the runway, and landed with a 10kt crosswind on concrete, but it is something that I would never do out of choice!
     
  10. Waynos

    Waynos Active Member

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    I believe the problem (such as it was) did not only relate to the narrowness of the track (a 'fault' shared with the Spitfire) but also due to the legs being splayed outwards in an attempt to increase track. This meant that if the aircraft swung a little on touchdown or made an approach that was not quite level there was a danger of one leg 'digging in' and resulting in the plane coming to grief.

    I think their is a danger of overstating this though because the Spits u/c could also catch out the unwary pilot but little is made of this.

    Ah, I see Soren pointed this out just before me
     
  11. DerAdlerIstGelandet

    DerAdlerIstGelandet Der Crew Chief
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    Agreed, but to say the Bf 109 crashes alot on take off and landing is wrong...
     
  12. Soren

    Soren Banned

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    Exactly Waynos.
     
  13. Soren

    Soren Banned

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    Absolutely.
     
  14. drgondog

    drgondog Well-Known Member

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    Couple of suggestions as we dive into this discussion

    1. Get accurate Total Parasite/Wetted area drag numbers.

    For the 51, RAE wind tunnel results for full scale 51B was reported at .0047
    The NACA wind tunnel tests at Langley yielded .0055
    The tests performed by North American on the propellerless dive tests at .75 Mach (to see how real conditions matched with Wind Tunnel) yielded .0053

    Lednicer also used this number - would suggest .0053

    2. The referenced Cdwet for the Spit IX is .0065

    3. The referenced Cdwet for the Fw 190A-8 was .0071 and the D-9 was .0063

    Second. What are the thrust parameters you intend to use? Hp is vague and each propeller is designed for specific target performance.. so how are you going to 'model' the differences in Thrust efficiency?

    Third. from an analytical standpoint each hp/thrust value is a 'saw tooth' that varies with altitude. I assume you will wish to be rigorous with respect to matching altitudes for the comparisons and matching low speed turning conditions as well as high speed?

    Fourth. The 51 has some 'quirky' 'power on' longitudinal stability issues at very high CL range close to CL max. We have beat to death the problemd encountered by Fw 190 wing in high G turns. Where do you want to bake that into your proposed calculations?

    Last. Pick a base weight, use a typical ammo load and use the same fuel load for each airplane. For the 51B as an example, the ammo/gun weight will about 190 pounds less than D, and the airframe empty will be 7,010 for the B/C and 7,635 pounds for the 51D. Aileron control stick forces are very high for the 109 at high speed, this is always interesting when making high G/High speed turn calculations... as it translates to the strength of the pilot - but not a factor on the other ships.

    I've just started re-thinking this after my last series of questions to Gene some months ago - which we haven't gotten around to finishing.
     
  15. davparlr

    davparlr Well-Known Member

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    All the data I have shows the P-51D power as being 1600 HP at SL and a max of about 1700 at 10k.
     
  16. Soren

    Soren Banned

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    Ofcourse HP means nothing without knowing prop efficiency, but the speeds of the a/c compared to the overall drag give a very good idea of this.

    As for weights, well it has already been chosen = Full weight for all a/c except the -51 which is left with empty fuselage tank. The reason for this is I understand that P-51 pilots on escort missions would rely on fuel from the fuselage tanks first to empty it, and then swith over to the external tanks until they had to be dropped. This way the CG stayed within the right range.
     
  17. Soren

    Soren Banned

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    Not at 70" MAP
     
  18. Soren

    Soren Banned

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    Btw, about the P-51's Clmax figure, this is lower according to NACA which lists it as 1.35.

    I admit 1.47 is my own estimate..
     
  19. ponsford

    ponsford Member

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    davparlr: 1830 BHP is obtained at 4000' in level flight using 75" MAP. I found that info at this source:
    P 51B Performance Test
     
  20. ponsford

    ponsford Member

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    I did some more looking around and found that by using +25 lbs boost - about 80" MAP, max power for a P-51 with -7 engine is 1940 BHP at S.L.
     
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