Zyzygie’s Mumbles and Rambles

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At the bottom of the CFE report it said the engines had to be throttled back to prevent surging between 20,000 and 37,000 ft.

Elsewhere it says 16,000 rev/min for climbing as against up to 16,600 for takeoff.

This is a couple of orders of magnitude less prone to surge compared to the JUMO, where, as Wendel says, you have to be very wary of surge while getting ready for takeoff.

Read what the CFE report says about the remedy for surge: At high altitudes "surge can be eliminated by throttling back the engines." As I've shown, the Derwent with centrifugal compressor was much less prone to surge than the axial JUMOs. Surge in the JUMO was likely to result in a fire or flameout. Deadly, as many German pilots were to experience. Including the Austrian ace Walter Nawotny.
 
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It's been a long time since I worked with gas turbines, but multi-stage compressors are going to be more susceptible to surge, in general, as the blades in the last rows of a compressor tend to have their loading increase as a compressor operates at lower rpm. This need to rematch is why multi-stage compressors will have various forms of variable geometry, such as variable stator angles or bleed valves. P&WA fielded multi-spool engines for this reason, as the two spools made the stage matching problem much easier.

The other way is that the amount of mass flow possible through a fixed-size duct will usually drop with heat addition; this is called the Rayleigh line. Adding fuel to a gas turbine engine too fast will shift the operating line of a compressor towards it surge line, and if it's done to fast, the engine will surge. A major design issue with fuel controls was to make the engine walk the fine line between acceptable response rate (iirc, the current FARs for civil engines is no more than 8 seconds from flight idle to maximum thrust) and not surging. Sometimes they don't make it (a former co-worker told me of the time he was in a 727 which had to do an emergency go-round due to a vehicle crossing the runway. He started sweating when he heard the engines giving that unmistakable noise from going into surge.
 
Zyzygie said:
At the bottom of the CFE report it said the engines had to be throttled back to prevent surging between 20,000 and 37,000 ft.

Elsewhere it says 16,000 rev/min for climbing as against up to 16,600 for takeoff.
Click to expand...

What makes the meteor an even bigger dog as it can't achieve it's full power, with already a much lower mach number than the 262, that makes it worse.

Zyzygie said:
This is a couple of orders of magnitude less prone to surge compared to the JUMO, where, as Wendel says, you have to be very wary of surge while getting ready for takeoff.
Click to expand...
Again, pilote's notes. Is Wendel an equivalent of the RAE. or the NACA? or the Rechlin EK?
The RAE seems to approve the German numbers for the 262 (see WWIIaircraftperformance) and the USA even more as the full test report seems to have disappeared from earth, and strangely the 262 wasn't allowed to participate in the 1946 Cleveland National Air Races



If you throttle back, you loose the thrust, you loose speed. Having such a lower speed than the 262, it's getting even worse, and gaining speed in the dive is also not permitted because of the mach limitation, so even with 5K feet advantage, the meteor will still be a dog. and unable to catch a 262 that's cruising with a higher mach than the meteor.
Again, documents from Naca/RAE or Rechlin please to prove the point about the 004 surge...
 

Check out:

"...The JUMO 004 didn't like radical air intake changes. Doing a maneuver like that could have it flame out. The Me 262 was not a dogfighting airplane like the F86 was later on..."​
​
And that's just referring to doing a roll...

Trying to carry out research into engine surge on a testbed was hopeless. Feedback from combat was absolutely crucial.

With all due respect to the staff at the research establishments, they weren't the ones best able to evaluate an aircraft in combat...
 
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Meteor F3 - CFE


The Me 262 from their graph below had a claimed climb rate of 1000 ft/min at 25,000 ft.

Appendix D

View attachment 578591
wwiiaircraftperformance.org
The Meteor still had a climb rate of 1000ft/min. at 31,000 ft., because of its excellent materials of construction (particularly Nimonic 75 and Nimonic 80)

The Me 262 seems to have to finish the graph for climb rate at 20,000 ft... But extrapolates to just over 1000 feet per minute at 25,000 ft.

wwiiaircraftperformance.org

Surge (Cavitation) was far more important to the JUMO than the Derwent. When surge occurred, the airflow to the combustion chamber radically dropped, hence reducing the air-fuel ratio and consequently increasing the combustion temperature. As the JUMO was already operating arguably beyond its "red line" temperature, this was disastrous, inevitably causing engine failure, and fire if the fuel wasn't cut immediately. The JUMO flame tubes were fabricated from mild steel, the Derwent from Nimonic 75:

Flight


I don't have the JUMO 004 figures, but they should arguably be similar.

For a temperature of 760C, the mild steel flame tubes would be running at just under "cherry red."
 

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The bad situation with regards to JUMO 004 and BMW 003 materials (and hence reliability) didn't have to be so:

"...According to figures for Ni usage per engine in Kay's "German Jet Engine and Gas Turbine Development 1930-1945" (2002), the entire production run of Jumo 004 engines, for example (some 6010 engines) used approximately 40 metric tons of nickel. This is not an insignificant amount, but compared to 1944 Ni supplies (10900 tons), consumption (9500 tons), or stocks (7900 tons) (U.S. Strategic Bombing Survey), the needs amount to little more than rounding error..."

Early German gas turbine development
 
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Why does the Me 262 testing run out at 20,000 ft?
Probably because you've pretty much run out of your allowed 10-15 minutes at full power? And to go longer would be "pushing your luck"?


Hans Fey

Zenos' Warbird Video Drive-in
ME262PilotsDebrief.pdf
 
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The Me262 had enough fuel for 80 minutes of cruise or 30 minutes of combat.
It also had a Rate of Climb close to 4,000 per minute. Meaning it would take it about 5 minutes to get to 20,000 feet with a full loadout.

So it appears there's an error in someone's math...

It is fun watching the vain attempts to discredit it, though - please, carry on.
 

There's big errors in someone's maths...

Let's not go on any longer about climb rates.
 
"...As a bomber, the long nose of the Me 262 limited dive bombing by not providing an adequate view on the target. This, coupled with dangerous approach speeds, make dive bombing a harrowing - though still possible - affair. Pilots simply were taught to drop their bombs above 3,000 feet to allow for the necessary altitude to recover in a climb..."

https://www.militaryfactory.com/aircraft/detail.asp?aircraft_id=108
 
"...Where agility was a limitation in the Me 262, this was offset by its ability to generate speed either through diving or through the open throttle. The nose-mounted cannon - disastrously lethal on paper - was known to regularly jam at the feed mechanism during maneuvering which rendered the Me 262 useless. The cannons also held a low muzzle velocity which made it largely inaccurate beyond 600 meters and useless as a ground strafing weapon. Combat losses were made at the hands of enemy fighters and, on occasion, some bomber gunners. Attrition rates were also increased by accidents due to pilot error and the general unreliability of the engines..."
https://www.militaryfactory.com/aircraft/detail.asp?aircraft_id=108
 
Several years ago, I met a gentleman who was also visiting Colling's "909" B-17 at the local airport. Turns out he was the R/O and top turret gunner on a B-17 in Europe.
During the coirse if the conversation, the Me262 came up and he became emotional.
He stayed that on one mission, an Me262 appeared out of their contrail and opemed fire, the cannon could be clearly heard over the din of their bomber's engines. The 30mm rounds shredded everything in the fuselage, exploding oxygen tanks and turing the waist gunner into a pulp. It also blew the inboard engine on the statboard wing away from it's mounts and blew the tail gunner position completely out of the fuselage. He stated that his turret simply could not traverse fast enough to lead the jet. His bomber had to dump it's bombload in order to remain airworthy and they struggled to keep up with the other bombers as they continued to their target and then home. To leave the group was death.
He survived several other Me262 attacks and each one was pure terror, unlike attacks from the Bf109s, Fw190s and Me410s.

Cherry pick all the crap you want and also let me know how well the P-80 and/or Meteor did in combat over Europe.

Oh wait, never mind.
 

I've repeated ad nauseum that the Me262 was a formidable bomber destroyer.

This forum is about dogfighting.

A big difference.

I've also said that I agreed with Galland that with 300 of them operating each day they could have stopped the strategic bombing campaign...

If they'd prioritised nickel for the Me262 they could have done that.
 

Z,

I'm going to have to respectfully disagree with Gallands comment. Yes the 262 could be a difficult opponent, and yes it could make life hell for the heavies. However, history shows us their use was limited. If, and it's a big if, Germany somehow could get 300 a day operational it would mean something along the lines of 600+ available PER DAY to draw spare parts from or to use. Given a higher concentration of attacks, the USAAF would have become more adept at killing them, both in the air and on the ground.

I could easily see where the bomber streams would be preceded by fighter squadrons hunting 262s on the deck or taking off. Then stack your fighters in layers above the bombers and peel off / reset as required to handle in bound jets. Also keep in reserves your hunter killers who follow them home for a big cup half inch lead poisoning. If there is one thing the Allies could do is put more metal in the air over Germany than could the Luftwaffe.

I'm not saying it wouldn't be a problem, but it would be solvable.

My opine of course.

cheers,
Biff
 

I've assumed that Germany had the same access to Nimonic or equivalent as the Allies.
As you say, that is a very big IF... But maybe not if they'd started working on it in 1940 like the Brits...

On the other hand, if they had eked out the War for another six months they would have faced the Atomic bomb, and the Meteor F4 and Lockheed P80...

Cheers,

Z
 
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Forgotten airfields

Me 262 concrete runway layout

Žatec - Czech Republic​
(Fliegerhorst Saaz)​
​
50°22'13"N 013°35'34"E​
​
Runway: 28/10 - 2500 x 80m - concrete​
Runway: 26/08 - 1400 x 20m - concrete​

Žatec airfield (Czech: letiště Žatec or Žatec-Staňkovice, also known as Fliegerhorst Saaz, ICAO: LKZC) was an airfield 65kilometers northwest of Prague.​
The airfield was originally built by the Luftwaffe in 1944 with one concrete runway measuring 1700x60m. It became the home base for the world's first operational jet fighter group: JG7 with Me-262 jet fighters. On the very last day of WWII (8 May 1945) at 15:20, I./JG 7 'Nowotny' Me-262 pilot Oberleutnant Fritz Stehle (2.Staffel) took off with his wingman and at 16:00 shot down a Soviet... fighter Yak–9. The engagement, which occurred over Freiberg, was the last aerial battle of World War II in Europe, and Stehle's victory may very well be the last aerial victory by a German fighter pilot in World War II.​
​
Still during the afternoon hours of 8 May 1945, all Me-262s capable of flying took off and headed west to parts of Germany that were occupied by the Western allies to avoid being captured by Soviets. It is believed all of them landed on Kaltenkirchen (unknown), Munich-Riem (2), Luneburg (1), and Faßberg (1). A large amount of non-flyable, damaged or wrecked Luftwaffe planes of many types (including Me-262s) remained at the airfield...​



Luftwaffe Jet Airfield Construction
 
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When you consider that these aircraft often had to be hauled to the runway by draft horses in order to save fuel, it gives a whole new meaning to the term "scramble."
How did they manage?
 
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