Vampire vs Me 262

[bigZ]

How do you think the Vampire would perform against the 262?

[delcyros]

Originally Posted by bigZ

How do you think the Vampire would perform against the 262?

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.

[bigZ]

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.

[Soren]

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

[delcyros]

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.

[Soren]

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

[delcyros]

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.

[bigZ]

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

[delcyros]

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:

The aircraft was armed with four Hispano Mark V 20 millimeter cannon in the bottom of the nose, with a maximum of 150 rounds per gun. They were aimed by a reflector-type gunsight. There was a gun camera in the nose.

[1.0] Vampire Variants

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

[Soren]

Originally Posted by delcyros

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.

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.

[delcyros]

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,

"to do this, you will need engineering drawings, which will have to be digitized, a good meshing program, unsteady and steady CFD programs -- I suggest VSAERO, FLIDYN, and USAERO from Analytical Methods, Inc -- and a structures program, such as ANSYS(I'm basically a fluids guy image). After some training (I suggest at least a BS in aerodynamics, in addition to specialized training in the different programs), a couple of cycles, to make sure that you're getting decent matches with reliable flight test data, you can write a paper and submit to the AIAA Journal of Aircraft or one of the equivalent publications, respond to the referees' comments, and have your name blazoned in ink. It will, of course, make absolutely no difference in anybody's opinion."

-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.

[fly boy]

i would go for 262 even though you have to slowly thottle up or down

[B-17engineer]

i say 262

[Soren]

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.

[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.

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.

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)

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.