Vampire vs Me 262

Discussion in 'Aviation' started by bigZ, Jan 19, 2008.

  1. bigZ

    bigZ Member

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    How do you think the Vampire would perform against the 262?
     
  2. delcyros

    delcyros Well-Known Member

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    Which Vampire? Which Me-262? If contemporary, than the Vampire MK I is more or less equal to the Me-262A in almost every respect, with the exception of better maneuverability, worser gunsight, worser stall speed behavior and worser high speed behavior. The post war Vampire F IV has an advantage of acceleration and climb, but here, nobody knows what the Me-262 would receive as advantages as her development ended (The czech buildt Avia S92 was continuing the production on the base of captured tooling devices).

    An Oberammergau document dating from feb. 1945 shows different stages of "improvements" of the serial production Me-262A. The most basic improvement is given below in comparison to the calibrated, average speed test of 120+ serial Me-262 performed in january 1945. It does show only slight improvements of the canopy, the controlls and surface treatment, all to be implemented in serial production along with the Jumo-004D4 in april 1945 (the graph is for Jumo-004B3, about 3.5% less avaiable thrust). There is some evidence that a few of these improved Me-262A reached an advanced stage in assembling to receive Werknummern. None of those came into combat. The graph is based on the performances of the V-9 high speed prototype, modified to these improvements in 1944.
     

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  3. bigZ

    bigZ Member

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    Thanks delcyros. I thought the maneuverability of the Vampire would be better. But surely the Vampire had a Gyro gunsight giving it the edge talking contempory.
     
  4. Soren

    Soren Banned

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    Maneuverability would only be better at low speeds, at high speeds the Me-262 has the edge.
     
  5. delcyros

    delcyros Well-Known Member

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    There is nothing wrong with the maneuverability of the Vampire. It outrolls the -262 at most speeds, was cleared for full acrobatics and turned very well.

    Charackteristics of maneuverability:
    Low wingload, mass concentrated, finely balanced ailerons. Light Stick (very sensitive), good roll charackteristics through the entire speed regime.
    Elevator very sensitive, pulling to hard will give no stall warnings. Pilots have to be careful, not to enter unintended spins, esspeccially at lower speeds.
    Rudder not very sensitive, demanded coarse movement to be of much consequence.
    The aeroplane was agile within the 600-800km/h speed range at low level. At lower speeds, however, steep turns required coarse use of rudder to maintain height, and it was uncomfortably simple to stall in relatively shallow turns.

    Stall charackteristics:
    The stall was likely to be accompanied by quite sharp wing-drop, but a surprising amount of aileron control existed right down to the stall, albeit with marked control buffet. One was advised to recover quickly while use of the most effective elevator could be maintained. Though by no means dangerous, the spin could be embarrassing owing to blanking of the diminutive rudders and the necessity to use coarse elevator control resulted in the aircraft pointing at terra firma for an uncomfortable length of time while speed built up!

    Engine handling:
    Pilots experienced in pistonengine handling had to learn to anticipate speed demands earlier as the power response from the Goblin was considerably slower, and any rapid throttle movement might cause engine surge, flame out or, at worst, a burst compressor (this is very typical for early generation jet engines, altough this belongs to planes with Goblin II not H1A. I suppose the charackteristic for the earlier engine is not better). In this regard, there is little difference between Jumo-004 and Goblin.

    High speed handling:
    At the upper end of the speed range, the Vampire behaved in singular fashion with the onset of compressibility, and from M=0.71 up to 0.76 the aircraft displayed increasing porpoising and wing buffet until at M0.79 the aircraft would suddenly "break" up or down with the likelihood of a wing drop, giving the sensation of an "incipient" flick roll.

    The Vampire MK IV was not equipped with a gyro gunsight. It featured a normal reflector gunsight type.
     
  6. Soren

    Soren Banned

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    Delcyros the Vampire wasn't anywhere near as forgiving as the Me-262, and at high speed it was at a disadvantage to the Me-262.

    You can read about the aerodynamics of the a/c at NASA's website:
    ch11-2
     
  7. delcyros

    delcyros Well-Known Member

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    The NASA page doesn´t tell You anything about the Vampires maneuverability. The Me-262 certainly cannot outmanouvre a Vampire for most of the speed range, except the extreme slow and extreme fast ranges.
     
  8. bigZ

    bigZ Member

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    Appreciate the incite guys. Was their a reason for not fitting a Gyro Gunsight for the Vampire?
     
  9. delcyros

    delcyros Well-Known Member

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    I don´t know for sure but I suppose it has something to do with avaiability and priorities perhaps? In the net, the early Vampire appears to be consistently noted for having reflector type gunsights:

    [1.0] Vampire Variants

    MK 4E gyro gunsights have been refitted by the late 40´s as standart equipment.
     
  10. Soren

    Soren Banned

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    It can out-turn the Vampire at all speeds, but not out-roll it. And roll rate is an important aspect, esp. as speed increases and turn performance is restricted by the airframe pilot. Roll rate becomes very decisive here.
     
  11. delcyros

    delcyros Well-Known Member

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    Have you ever flown a Vampire? Or for that matter a Me-262? I cannot say to have done either but You claim it will outturn them without having any proof for this claim. It´s pure speculation.
    Have you turn charts on your hand to proof Your claim? I doubt so.
    And if you come to an physical aproach,
    -emc

    Sustained turn performance is in relationship of power avaiable and power required for preventing a stall. The Me-262´s wing does provide less lift and has less powerload than the Vampire´s. It cannot outturn the Vampire over the whole speed regime on a sustained turn base.
     
  12. fly boy

    fly boy Member

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    i would go for 262 even though you have to slowly thottle up or down
     
  13. B-17engineer

    B-17engineer Active Member

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  14. Soren

    Soren Banned

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    Delcyros,

    The Me-262's wing doesn't provide less lift, it infact provides approx. 25% more lift pr. area than the Vampire's wing. So unless you're suggesting that the Vampire has a 25% larger wing area your argument just doesn't hold water.

    And as to power-loading, well again the Me-262 holds a clear advantage with 17.6 kN vs the Vampire's 9.3 kN. (Hence the Me-262 much superior performance)

    So like I said the Me-262 easily out-turns the Vampire through the entire speed regime.
     
  15. delcyros

    delcyros Well-Known Member

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    No,I suggest to look into the Vampire´s airfoil and it´s properties. It features EC1240/0640 airfoils, with a 14% thickness at the root and 9% at the wingtip. Corrected for the reynolds number this yields a good 18% better Cl-max than the Me-262´s semi-symetrical 12% at the wingroots and 6% the wingtips. And this Cl-max is reached at more comfortable angle´s of attack, too. Wingload for the Vampire is 175 Kg/m^2 (corrected for airfoil and max CL: 136.7Kg/m^2). Me-262 wingload is 294,9Kg/m^2 (corrected for airfoil and max CL: 268.1 Kg/m^2 and 214,4Kg/m^2 with full span LE-slats deployed, respectively). So basically, yes, the Vampires wing does provide more lift effectively.

    Uhh, wait a minute. Two Jumo-004B4 will yield 3.923lbs/1.780Kp thrust, that´s not 17.6KN! The Vampire I has a H-1A delivering 2.770 lbs of thrust (=~2.600lbs/1.180Kp if we factor in air intake / exhoust losses). The problem is that the Vampire I weights 3.899Kg normal while the Me-262A weights 6000Kg normal (both without external loads and hardpoints/droptanks). The resulting thrust/weight ratios are 0.303 for the Vampire and 0.297 for the Me-262, not much to tell between both. If anyone, than the Me-262 does NOT hold the advantage in powerload.

    It is not necessary to overexaggerate the Me-262´s abilities. It has advantages over the Vampire but turning performance most likely is not one of them.
     
  16. Soren

    Soren Banned

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    For crying out loud Delcyros! Are you just making up stuff as you go along ?

    The Jumo 004B's max output is 8.8kN (1,980 lbft), and the Me-262 has two of them !

    The max output of the Vampire FB.1's Goblin 1 is 9.3 kN (2,100 lbft)!

    You can see the different thrust figures available to the different De Havilland a/c here:
    de Havilland data

    The Me-262's empty weight is 3,800 kg, the Vampire's empty weight is 3,300 kg, so thats a power-loading of 215 kg/kN vs 314 kg/kN respectively. It's no wonder that the Me-262 is considerably faster at 870 km/h, and climbs faster at 3,900 ft/min, despite being a larger a/c. (The Vampire FB.5 with a 13.8 kN engine climbs at 4,500 ft/min and isn't even as fast at 866 km/h)

    And as to the airfoils, again you seem to just be making up stuff and then base your wild claims on it.

    The official airfoil thickness ratio of the Me-262 is 11% at the root and 9% at the tips. The airfoil design used was the NACA 00011-0.825-35 NACA 00009-1.1-40.

    The Vampire's airfoil thickness ratio is 14% at the root and 9% at the tip, not hat different from the Me-262. The airfoil type used was the EC1240/0640 EC1240/0640.

    And as to your CLmax figures, well they are based solely on thickness ratio, which is ridiculous cause you can't even begin to figure out CLmax by just using thickness ratios for crying out loud! First of all there's no std. increase in Clmax with an increase in thickness ratio, infact Clmax may drop with an increase in thickness ratio depending on the airfoil type, so you can forget that those ridiculous Clmax figures you posted !

    For example a NACA 23000 series airfoil (Known for its high CLmax figures) of 9 - 16% thickness ratio has a CLmax of 1.58 to 1.64 ! That's a lot more than usual. But as the thickness ratio increases to 18% the CLmax actually starts to drop.

    So like I said the Me-262 holds a lift advantage of ~25% pr. surface area, giving it a lower lift-loading, and it also holds a good advantage in power to weight ratio.

    (3,800 kg / 21.7)*0.75 = 131.33 kg/m^2
    (3,300 kg / 24.3) = 135.8 kg/m^2
     
  17. Glider

    Glider Well-Known Member

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    I notice from the De Haviland web site that the F1 was fitted with the 2,100lb engine and later the 3,100lb engine. The extra 1,000lb would make all the difference to the performance.
    What isn't clear is when the switch was made.
     
  18. red admiral

    red admiral Member

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    The H.1 was initially tested at 2300lbf which was then increased to 2700lbf in the Goblin I and 3000lbf in the Goblin II and then 3100lbf in the Goblin III.

    I have no idea where Soren's stats on the Vampire come from, and the use of empty weights more or less completely nullifies the discussion. Using empty weight gives the Me 262 a massive advantage in as it completely overlooks the much higher fuel consumption of the 2x004s compared to the single Goblin. Combat weight (mid between empty-max) shoudl be used.

    The Me 262 climbs much slower at 3900ft/m against 4500ft/min and the speed differential is an entire 4mph in favour of the Me 262. Vampire FB.5 had slightly more thrust but put on weight through extra equipment postwar.
     
  19. Soren

    Soren Banned

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    red admiral,

    Try actually reading my post before jumping to conclusions. I linked my source on the Goblin engines.

    The Vampire FB.5 is the one which climbs at 4,500 ft/min and has a top speed of 866 km/h, NOT the Vampire Mk.I which is the only version which saw service in 45. Do you even know when the different versions saw service??

    Also there's nothing wrong with using empty weights, esp. since it's only natural that a more powerful a/c consumes more fuel. Also the use of the Jumo 004D would've not only decreased fuel consumption but also increased power to 10.3 kN.
     
  20. Glider

    Glider Well-Known Member

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    I have found out that the 3,100lb thrust version of the Goblin was fitted to the 41st Vampire mk1 onwards.
    The Mk1 with the larger engine would I have thought been a pretty hot plane to fly without the extra weight added to the Mk3 let alone the Mk 5.

    Re the different engine powers, All I can say is that the incremental jumps in power are likely to have happened during development, but the chances of those differing versions were fitted into production aircraft over such a short time period is small.
     
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