Me262 question: Did it have WEP?

[EagleDNY]

I have a good history of the 262 where the test pilot was trying out the 262V3 (the one modified to accept the Jumo 004), and the big problem he had when trying the first jet-powered flight in it was that lacked elevator authority in the tail-down attitude (this prototype didn't have a nose wheel), so they had him "apply the brakes momentarily at the 112 Mph unstick speed so that the Me 262 would tip up, put the elevators into the airstream, and make takeoff possible".  Takeoff speed of 125 with 20 degrees of flaps and a full load of fuel is reported in that manual, but go look at some films of actual 262 takeoffs vs what people normally do in AH.  The actual takeoffs are done at a very shallow angle - they ease off the deck then pull in the gear and continue a modest acceleration while raising the flaps - they don't do much actual climbing until they get up to a more reasonable speed and the flaps are fully retracted.

Did you guys read the section on "diving" on page 12 of that manual?  I wonder about this manual a bit given the quote "It is also reported that once the speed of sound is exceeded, this condition disappears and normal control is restored."  I wonder who got the job of diving a 262 past Mach 1 to find this out? 
 
On the WEP question - the 8,700 rpm limit of the Jumo 004B is itself an interesting story.  The Jumo 004A was not approved for production because of the 'excessive use of strategic materials' (too much rare and expensive metal in the turbine blades).  The Jumo 004B fixed this by making the turbine blades out of what was essentially folded sheet metal and had a time-between-overhaul of only 50 hours (and even that was never reached).  The first 004B-1s would run at 9,000 rpm, but at this speed they began having vibration failures.  They called in a musician who determined the natural frequencies of the turbine blades by bowing on them with a violin bow.  Once he figured out the natural frequencies of the individual blades in the turbine wheel they found that they needed to taper the blades slightly and reduce the rpm to 8,700 to overcome the vibration problem. 
The 8,700 rpm for 10 minutes limit is there because of the risk of engine failure if you push the 004B too hard for too long.  There are all kinds of other 'warnings' on what not to do as well - like don't start the engine over 13,000 feet due to a fire hazard, don't open the throttles too fast while on the ground as it causes cavitation in the compressor stages, etc. 

[Krusty]

They didn't understand Mach1 back then. It was impossible for any WW2 aircraft to break that limit.

[BnZs]

I see no direct relation. If we would get the >8400 settings as a kind of "WEP", nothing much would change in terms of combat performance if we get 10 mins of full power at a time. Even at only 8400 rpm, the 262 cruises at insane speed. It still would be the same dread of all goons and buffs.

How much longer would it take you to climb to your given altitude and accelerate to anywhere near your top speed? It already takes a day and a half. It looks like this needs to be done to the bird for purposes of accuracy, but if you are going to nerf it even slightly, reduce the perk price slightly too. Its only fair.

[colmbo]

Also, the manual lists lift-off speeds as 112-125mph or so. HAH!!!

I can never get mine to lift off without full flaps and at least 150-175mph!

Your unstick speed seemed a bit high so tried it out.

With full fuel and using 3 notches of flaps I lifted off at 105-110 IAS.  At about 90IAS I rotated until I bumped the tail then lowered the nose just far enough to keep the tail from dragging.  You really have to honk the nose up.

[Charge]

"They didn't understand Mach1 back then. It was impossible for any WW2 aircraft to break that limit."

Oh really? I thought it was possible but the real challenge was to survive the event. The manual likely describes the aerodynamic pressure effects on control surfaces prior to actual "sound barrier" so as such it is likely that exceeding the actual sound barrier in a 262 was not something you looked forward to in any case, emergency or not.

I recall that one of the veterans who flew the 262 told that when you were landing you were supposed to listen to the engines while they were warm and if there was a slight scraping sound from engines you were to notify the mechanics that is was probably time to change the engine as the noise was caused by the exhaust turbine scraping the walls of the exhaust tube and if you pushed the engines too hard you were guaranteed to get that scraping sound upon RTB.

The exhaust turbine was probably the weakest part of the engine as there was a chronic lack of materials to manufacture such a high stress part in large quantities from proper materials.

-C+

[Krusty]

No, not possible. Leading up to the barrier is an entire layer (multiple layers?) of boundary pressure that can have all sorts of effects. All those effects and more that were attributed to "the speed of sound" or "mach1" in WW2 times were rarely ever close to Mach1. I think it is safe to say no WW2 vehicle broke the speed of sound, ever...


Unless you count a V2 on re-entry... 

[Krusty]

Your unstick speed seemed a bit high so tried it out.

With full fuel and using 3 notches of flaps I lifted off at 105-110 IAS.  At about 90IAS I rotated until I bumped the tail then lowered the nose just far enough to keep the tail from dragging.  You really have to honk the nose up.

D'oh, I forgot to do some offline testing. I'll make a reminder.

You may be right, but at least going by the notes, it shouldn't be a sudden sharp pull-out. It should be a shallow gentle angle, which to me implies the plane floats off the ground (nearly level). I wonder why the difference with AH? Are the wings not creating enough lift? Have to haul it back and get a major AoA for same results?

(again, guessing... I still have to do some personal testing)

[MiloMorai]

This is how a Me262 should take off.

http://www.youtube.com/watch?v=gh9SK5JH7w8&NR=1

and

http://www.youtube.com/watch?v=zsku0AZylfg&feature=related

[Krusty]

This is how a Me262 should take off.

http://www.youtube.com/watch?v=gh9SK5JH7w8&NR=1

and

http://www.youtube.com/watch?v=zsku0AZylfg&feature=related

Smart thinking!

See when I take off in this thing in AH it's got a much longer run and a MUCH higher AoA just to get off the ground. Combo mentioned a pretty extreme AoA also. Is it pilot error in our case? Or is the AH flight model off a tad?

[EagleDNY]

They didn't understand Mach1 back then. It was impossible for any WW2 aircraft to break that limit.

That's what makes me wonder about the guys that wrote that manual.

[colmbo]

Smart thinking!

See when I take off in this thing in AH it's got a much longer run and a MUCH higher AoA just to get off the ground. Combo mentioned a pretty extreme AoA also. Is it pilot error in our case? Or is the AH flight model off a tad?

You can't really make a judgement just from watching the video since we don't know what speed they were lifting off at.  Real life I wouldn't pull a multi-engine airplane off the ground at minimum speed because of the risk of an accident if you should lose an engine while slow -- very bad juju.

[Guppy35]

Again going on what that RAF pilot I knew wrote, they had 1800 yards at Fassberg and barely squeaked over the trees.  it was a slow rise on take off.  The first guy going actually scrapped through the trees.  He then managed to collapse the nose gear on landing.  my RAF friend managed to get his down fine

As for the engines, the practice was to have the mechanics standing by each engine with a fire extinguisher to cool it at start up.  Not very reliable.

[Shiva]

And there were a few other amusing design quirks of the 262. Some years ago, the local CAF had an event with a number of WWII pilots, where I met Gunther Rall and Walter Schuck, among others. One of the other ex-LW pilots had been in KG50 when they were transitioning to the Sturmvogel, and he talked about a problem with the 262's landing gear that he discovered the hard way.

The 262 did not have a steerable nose wheel; instead, the nose wheel castered, with the pilot able to steer the plane on the ground with the rudder (if there were sufficient airflow), by differential throttle, or by differential braking. The latter two, if used improperly, could get a 262 to rotate around one stationary main wheel... in the process, castering the nose wheel 90°, after which it was not possible to get it to straighten out again; when he did it, one of the ground crew had to come over and kick the tire to force it back into line.

His story gave me the idea -- which I still have yet to find the time to carry out -- of making a vignette of a 262, stopped at the edge of the runway with its nosewheel turned 90°, the pilot, having gotten out of the cockpit, standing with one hand up on the side of the plane bracing himself as he tries to kick the wheel around so he can get it rolling again, and title it "Kick the tires..."

[Charge]

"No, not possible. Leading up to the barrier is an entire layer (multiple layers?) of boundary pressure that can have all sorts of effects. All those effects and more that were attributed to "the speed of sound" or "mach1" in WW2 times were rarely ever close to Mach1. I think it is safe to say no WW2 vehicle broke the speed of sound, ever..."

Interesting. Do you have a further insight on this or just guesswork? It sure sounds like that.

AFAIK the practical sound barrier is nothing like you described. The multiple "boundary layers" can be induced on the object that accelerates towards the speed of sound causing the speed of sound to be exceeded locally on eg. wingprofiles (compressibility). That is probably something you are referring to with "all sorts of effects".

Theoretical calculations have indicated that it was possible for 262 to achieve Mach 1.2 in a dive, although it is suspected that while the structure can take it upon acceleration it possibly cannot hold together on deceleration. My guess is that fuselage is OK in this kind of stress but it is probably wings that are under an incredible stress due to too shallow sweep-back angle.

So any pilot who survived the event were more of less quite lucky to live the feat. Eg. Mr Mutke who has claimed to have broken the sound barrier in a 262 told that he started his dive from about 40k feet so the atmospheric conditions changed all the time during his dive as the temperature and altitude changed, and as such also the conditions to exceed the speed of sound also changed. In that sense I don't think it is all that impossible as you suggest.

http://www.aerospaceweb.org/question/atmosphere/q0112.shtml

Structurally the 262 was not too flimsy either. In comparison if 109 had 0.75mm aluminum on tip of its wing, the thickness was 2mm in 262. The net effect on structural strength is considerable.


"And there were a few other amusing design quirks of the 262."

That is interesting too. What are the design quirks in 262 to begin with?

The nose wheel hardly qualifies as one -P38 and P39 actually had the same kind of arrangement.

Building a working axial turbofan engine out of non-optimal materials hardly qualifies as another. Maybe an engineer could have said: "We don't have proper materials so we won't build it. Of course we could build it from high grade steel but it would mean that the fans would be need to be changed quite frequently but that is not the proper way to do it so we won't do it at all."

Now that would have qualified as idiotic, wouldn't it?

-C+

[MiloMorai]

The nose wheel hardly qualifies as one -P38 and P39 actually had the same kind of arrangement.

At least the P-38 and P-39 had the air from the propeller flowing by the rudder while thew Me262 had to be moving at some speed to have airflow around the rudder.
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The Me262A-1a required 920m/1006yds for take off using 100% power. I am presuming unstick distance.