Vampire vs Me 262

[Soren]

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

[Glider]

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.

[red admiral]

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.

[Soren]

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.

[Glider]

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.

[delcyros]

Originally Posted by Soren

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)!

Actually, the Jumo-004B3/4 were the only models rated to 890 Kp thrust, the B-2 was limited to 840 Kp and the B-0/B-1 rated to 820 Kp, respectively. By 1945, the vast majority of engines were Jumo-004B3/4. Only the Spider-Cap prototype hat 2.100 lbs rated H-1A´s, The Vampire F-I (there was no FB-I) was serially equipped with Goblin-I rated to 2.700 to 2.770 lbs, while using a more sophisticated mark rated to 3.100 lbs installed from the 41st serial plane onwards.

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)

You are comparing apples with oranges. The FB-5 is a heavier fighter-bomber variant and in this condition (no fuel, no ammo, no loads) neither plane will be able to take off. Comparisons are usually placed at normal (full combat load), occassionally at overloaded fighter configuration in order to reflect operational conditions, both of which place the Me-262 at a slight disadvantage.

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.

No claims, just proofs. Unlike You, I have access to the profiles in question. And your data don´t contradict mine (NACA 00011 is semi-symetrical).

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 !

No. My Cl-max figures do come from drag/lift profiles, provided by profile software. Thickness ratio is not the decisive aspect in airfoil performances. If you have access to ordinates of the profiles (to be obtained in the net) and Mark Drelas or other software (profile 2.0 is excellent) You will find my values for Cl-max substantiated. Don´t forget to use the profile for the correct reynold-numbers! Each airfoil has different profiles for different RE-numbers.

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.

That´s pretty irrelevant as neither the Me-262 nor the Vampire had this airfoil.

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

Disagreed. You are free to verify this on Your own, my friend. Assuming that both planes have the SAME AIRFOIL is a substantial and in this case basic error.

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.

Yes. Agreed 100%.

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??

There is only a slight difference in speed and performance between Vampire FIII and Vampire FB-V. The Vampire F-I using Goblin-I (2700lbs) is slightly lower rated but in no ways inferior as pointed out above at any condition other than "almost empty".

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.

Anthony Kay rates the Jumo-004D4 (of which none ever equipped Me-262A´s to see combat) with 930Kp thrust (9.1KN). The Jumo-004E without reheat was rated to 1000 Kp (9.8KN) thrust, but this engine, too was about to be produced.

[DerAdlerIstGelandet]

Soren instead of telling people they are full of ****, post some sources to back up your facts. Then there is no arguement...

[Glider]

I have found some stats on the Vampire F1 which people may want to compare to the 262.
de Havilland D.H.100 Vampire - History, Specifications and Pictures - World Military Aircraft

Its seems to be more than a match in most areas.

[Soren]

Originally Posted by DerAdlerIstGelandet

Soren instead of telling people they are full of ****, post some sources to back up your facts. Then there is no arguement...

I never said he was full of ****, I was questioning his info as assumptions as he seems to be posting about something which he has limited knowledge on.

Also I did post sources Adler, you just overlooked them. On the other hand Delcyros has posted no sources for his info on the Me262 or Vampire.

The Jumo 004B's out-put is 8.8kN, that's fact, Delcyros just wants to slither around this.

Delcyros,

I'd like to see the results from the drag/lift profile software in the form of screenshots please. I'm esp. interested since Foilsim & VSAERO is showing very different results from yours!

Also the root thickness ratio of the Me262's wing is 11% and the tip 9%.

Look here for more information on airfoils:
The Incomplete Guide to Airfoil Usage

This isn't a battle of points, you don't loose face being wrong.

[DerAdlerIstGelandet]

Originally Posted by Soren

I never said he was full of ****, I was questioning his info as assumptions as he seems to be posting about something which he has limited knowledge on.

Soren it is a term used here in the United States. It does not litterally mean you said he was full of ****.

[Soren]

I know, but it came across abit harsh Adler, that's all. (I do the same frequently, it's a bad habbit, I'm a very straight forward person) Things easily get interpreted incorrectly on forum boards. You cleared up what you meant, all is good.

[delcyros]

I am pretty sure, I could file screenshot the whole day long and wouldn´t change Your mind, Soren.
The design Clmax of Vampire and Me-262 aren´t the same.
Please check the NACA report 647, avaiable online for the Cl-max of the NACA 0009 and 0012 airfoils for the following condition (full scale AR: 6.0 models tested at standart atmossheres for 100 mp/h).

The Vampire´s EC 1240/0640 airfoil is investigated in R. & M No° 2678
(11084, 11191) A.R.C. Technical Report and compared with the NACA 0012. Bottom line is that the NACA 0012 (AR=6)has a CLmax of 1.40 and Reynoldsnumber of 5.0 mill. at Mach=0.1 compared to Clmax =1.26 at R= 5.0 mill. and AR=6 for the NACA 0009. The Cl-max figure of all airfoils drops while engaging higher Mach fractions until about Mach=0.4 where above mentioned report starts to compare the NACA 0012 (remember, it is better than the NACA 0009 in Cl-max by 11.1%) with different other airfoils. You can deduct the logic from this approach: The NACA 0009 has a lower Cl-max than the NACA 0012, which itselfe finds to be little different from the EC 1240/640.

Could one of the moderators resize the images, please? Thanks in advance.

[Soren]

Just post the screenshots Delcyros.

Just posting the CLmax figures for the NACA 0009 - 18 series airfoils solves nothing.

[Seawitch]

Only a very few 262's out gunned the Vampire

[delcyros]

I will submit screenshots of the airfoils and their respective RE-functions as soon as I receive a permission to do so. Some of the software involved requires this.
However, You can see easily that the NACA 0009 does not provide as much lift as a NACA0012 or the Vampire´s EC1240/0640 under identic conditions from the charts above. It is approx. 11.1% short of this in between Mach= 0.1 and Mach = 0.4. Of course, both planes do have different conditions, actually. The aspect ratio is different as is the planform and the reynolds number or the smallest chordlength (which in our cases define the max. Cl due to lift distribution over span by absence of geometric wing twists). To adress these aspects, I used 3d models of the wings in question in order to derive the correct RE-numbers for each section. The models are generated with rds-student (see isometric viewings below, not identic in scale!).
The critical max. permissable reynolds number for the Vampire wing is 42% higher than for the Me-262 (the shortest airfoil sections at the tips respectively), translating into the aforementioned netto advances of the Vampire. These do define the max. permissable (= flyable) Cl-max. The higher Cl-max of the wingroot sections is only of theoretical interest, it´s use would not be possible for any controlled flightregime (that´s why You have LE-slats usually at the outer wings or a geometric twist to offset the drop in lift distribution towards the wingtips) as it provokes a wingtip stall.
One of the key results from the above mentioned RAF paper is that Cl-max figures of otherwise identic wings ARE NOT BEHAVING like solids. THEY CHANGE with REYNOLDS NUMBERS, MACH FRACTIONS and ASPECT RATIO. While a Cl-max of ~1.25 is possible at Mach 0.1 for a given wing with NACA 0009, the Cl-max at Mach 0.4 is below 0.8 for the same wing! A plane which enjois a lower stall speed benefits from higher possible Cl-figures. Fortunately for us, the Me-262´s stall speed is 175 Km/h (109 mp/h) while the Vampire´s is reported to be 109 mp/h, too. The advantages of the very thin Me-262 wing are coming handy at higher Mach fractions than Mach =0.5 and are substantial at Mach= 0.7. So define maneuvering speed in the first place!