swampyankee
Chief Master Sergeant
- 3,954
- Jun 25, 2013
Germany's use of maltreated, underfed slave labor did little to improve build quality, but treating the peoples of invaded countries well was contrary to nazi ideology.
Zyzygie’s Mumbles and Rambles
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Germany's use of maltreated, underfed slave labor did little to improve build quality, but treating the peoples of invaded countries well was contrary to nazi ideology.
Kevin J
Banned
I believe the top speed of the Me 262 ranged from 485 to 540 mph depending on build quality.
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- #383
Many thanks for keeping it brief Koopernic.
I don't think I could have digested the full version...
Your deep conviction on the matter brought to mind aphorism #630 in Friedrich Nietzsche's "Human, All Too Human"...
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- #384
Re Galland and the idea of the "Schnellbomber," we'll have to agree to disagree. But Messerschmit seemed to think the ideal configuration for a bomber should be nearer the Meteor in terms of cockpit location:
Re the automatic throttle, you may be interested:
The German jets were extremely heavy, and hence had low thrust to weight ratios. This wasn't going to change with further development.
The proposed future development JUMO engines all had a thrust to weight ratio of 1.4 to 1. Half that of the Derwent V.
Re maneuverability:
The Meteor had a much higher service ceiling than the Me 262: 13,000 vs. 11400 metres.
Re the automatic throttle, you may be interested:
The German jets were extremely heavy, and hence had low thrust to weight ratios. This wasn't going to change with further development.
The proposed future development JUMO engines all had a thrust to weight ratio of 1.4 to 1. Half that of the Derwent V.
Re maneuverability:
The Meteor had a much higher service ceiling than the Me 262: 13,000 vs. 11400 metres.
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Snautzer01
Honourably banned
- 38,244
- Mar 26, 2007
not to bad or as good ad the Fw190
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
The Jumo 004 series were heavy, others like the BMW 003A were lighter at 1,375 pounds with a max. thrust of 1,760 lbf., HeS8 at 838 pounds with a max. thrust of 1,300 lbf. and the HeS30 at 860 pounds with a max. thrust of 1,896 lbf.
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- #387
Very interesting. But unfortunately just more "if only" sagas. Also apart from the HeS 30, fairly low thrust to weight ratios:
"...Helmut Schelp, in charge of engine development at the RLM, refused to give Heinkel a production contract, an event Hans von Ohain claims brought Ernst Heinkel near tears. Schelp noted that while the design was excellent, BMW and Jumo were so far ahead they simply did not need another "Class I" engine – something that would prove ironic in another two years when both of those engines were still not operational. It also appears he had some misgivings about the compressor arrangement, but if this was the case it was never official. He also cancelled von Ohain's Heinkel HeS 8 at the same time."
"Instead of yet another Class I engine, Schelp asked Heinkel to continue work on a Class II engine of about 1,300 kg thrust, which would be needed for reasonably sized single-engine fighters, and as a useful addition to twin-engine bombers. Thus work on the HeS 30 and HeS 8 ended, and Heinkel turned, grudgingly, to the Heinkel HeS 011, which would not enter production before the war ended. The remains of Müller's team were then moved to the Heinkel-Hirth plants to work on the new engine..." Wikipedia
It looks like it held some promise, but never got beyond the prototype stage. We don't have any details of performance in combat conditions: What was it like in terms of durability? Reliability? Controllability? Specific fuel consumption? Surge resistance?
All of these were the Derwent's strengths.
JUMO bench tests - deterioration with time:
Creep was inevitable with the alloys they were using.
The development of Nimonic was crucial to making gas turbines practical:
Corrosion was also a big problem. Mild steel highly stressed and exposed to hot (~ 700C) oxidizing gas was not going to last long. That was medium cherry red hot.
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GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
However, the of the Jumo engine list you posted, only the 004, 004A and 004B were ever used the rest were either in the test phase or they were paper projects.
The HeS8 as not allowed to be developed, like the HeS30 and keep in mind that they didn't have remarkable thrust, but they weighed a fraction of a 004, greatly reducing the weight penalty.
The He280 performed remarkably well as a fighter with the HeS8 and would have been relentless with the HeS30...when they installed 004s on it, the He280 could barely get off the ground...
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- #389
Hmmm... sorry, but this looks like another "if only" story:
"...The German Air Ministry eventually forced airplane makers towards the newer, more advanced HeS 011 series turbojet engine due to ongoing issues with the HeS8 and HeS 30 turbojet models. However, the advanced nature of this new engine was equally problematic for engineers. This is where pulsejets allowed at least some further development to take place regarding the He 280 prototypes. Similarly, the BMW 003 and Junker Jump 004 turbojets were options."
"Due to all of its inherent limitations, the Messerschmitt Me 262 "Schwalbe" twin-jet-powered fighter was selected ahead of the He 280 to become Germany's first jet fighter in the war. As such, the He 280 was canceled in full on March 27th, 1943, and Heinkel was forced to concentrate on German bomber production and development for the remainder of the war..."
https://www.militaryfactory.com/aircraft/detail.asp?aircraft_id=220
I note that the Germans were also working on a sort of hybrid centrifugal-axial engine? The Heinkel HeS 011.
It would be interesting to see what their rationale was there...
General characteristics
- Type: Turbojet
- Length: 3450 mm (11 ft 3¾ in)
- Diameter: 875 mm (34½ in)
- Dry weight: 950 kg (2,094 lb)
- Compressor: Diagonal + three stage axial
- Combustors: 16 chambers
- Turbine: Two stage axial.
- Maximum thrust: 12.7 kN (2,900 lbf) at 11,000 rpm.
- Thrust-to-weight ratio: 1.29
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Lockheed P-80 Shooting Star vs. de Havilland Vampire
Walter J Boyne's book "The Best of Wings" quotes Me 262 test pilot Gerd Lindner pilot as saying it could achieve 565mph at 16,400ft (that would have been 925kmh at 5000m). He was a professional test pilot, not a factory acceptance pilot or a fighter pilot. He's paid to be technically accurate. Smooth surface, maybe filled in, well aligned airframe, well aligned engines, good pair of engines.
Lindner also notes he nursed a pair of engines to 60 hours on the wing. The official Jumo MTBO was 25 hours and on the basis of spare parts production the Germans expected 4 x 25 hours life out of the engines. The Luftwaffe maintenance crews, the blackbirds were possibly pulling them early to be safe. It is also important to note that the more reliable hollow air-cooled blades of the Jumo 004B4 only reached the front in December 1944 or so and so air cooled blades were likely quite rare.
Poor Airframe build tolerances & quality was not due to the quality of the labour, which was quite capable, but the fact that Me 262 were being built in the open air in Forrest factory lines on wooden rails without jigs. The Jumo 004 also suffered from unauthorised martial substitution.
The 25 hour overhaul involved replacing the 6 carbon steel combustion chamber cans and the turbine. Turbine was to be inspected at 25 and run till 37.5 if ok, I thunk this was seldom done.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
"If only"?
The He280 was further developed than the Me262, flying under it's own power roughly two years ahead of the Me262 - it was the slow development of the engines (ALL makes) that plagued the jet fighter program.
The HeS8 and HeS30 were not allowed to be developed further like the 004 and 003 were - both of which were never fully developed by war's end and the HeS series were less problematic than the Jumo/BMW engines.
Instead of looking at their total thrust output, look closely at their Thrust to Weight ratio.
HeS8: 1.61
HeS30: 2.20
Jumo004B: 1.25
BMW003A: 1.13
The He280 was further developed than the Me262, flying under it's own power roughly two years ahead of the Me262 - it was the slow development of the engines (ALL makes) that plagued the jet fighter program.
The HeS8 and HeS30 were not allowed to be developed further like the 004 and 003 were - both of which were never fully developed by war's end and the HeS series were less problematic than the Jumo/BMW engines.
Instead of looking at their total thrust output, look closely at their Thrust to Weight ratio.
HeS8: 1.61
HeS30: 2.20
Jumo004B: 1.25
BMW003A: 1.13
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- #392
I don't follow...
It gave a normal CRUISE speed of 465 mph?
As I read it, the maximum measured speed was 568 mph at 20,000 ft.
Hans Fey gave the following:
As for roll rate:
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Kevin J
Banned
IIRC, according to Kurfurst, the performance tolerance of new production German fighters at the end of WW2 was +-5%. So if median speed was 510mph then for Me 262, say 484-535mph, then a cleanup that you wouldn't do in the field should give you maybe an extra 5%. So max speed 562mph?
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- #394
Myth Busting the Me-262 - Kaiserslautern American
Mythbusting the Me 262 - Kaiserlautern American
"The prototype Galland flew was powered by the first model of the Jumo 004, the Jumo 004A. This engine had been constructed with the highest quality materials available — notably nickel, cobalt and molybdenum — and as a result functioned reasonably well."
"Unfortunately, it was impossible to produce the Jumo 004A in large quantity because Germany did not have enough of these raw materials, and the production version, the Jumo 004B, was built with inferior materials."
"All of the "hot section" components were changed to aluminum-coated steel, and the turbine blades were also produced from different materials than those used in the Jumo 004A. The engine was easier to mass produce, but it was much less reliable and it required a complete overhaul every 10 hours. It also required delicate throttle movements in flight — difficult in combat."
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- #395
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- #396
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- #397
Hans Fey stated that they were only allowed 10-15 minutes at maximum speed.
Higher speeds than normal could sometimes be achieved but at the expense of overheating the engine hot components. Hence a correspondingly much higher risk of incurring catastrophic engine failure.
IIRC the engines were required to be overhauled if taken above full load for more than 10 minutes.
Extract from The Jet Race and the Second World War.
Extract from The Messerschmitt Me 262 Jet Fighter | Defense Media Network
The Me 262 Stormbird: From the Pilots Who Flew, Fought, and Survived It
By Colin D. Heaton
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- #398
The HeS 011 had a 4 stage compressors. Stage 1 is the interesting stage. It is often referred to as a diagonal flow compressor or a mixed flow compressor. On the surface it looks like a centrifugal radial compressor but the key difference is a carefully curved design that directs the outgoing air in the axial direction instead of radial. The air is directed on to a stator vane which achieves considerable compression. This is followed by 3 normal axial stages, an annular combustion chamber and a two stage air-cooled turbine.
The mixed flow (centrifugal/axial) first stage compressor ensured combat ruggedness and the ability to ingest turbulent air. Hence aircraft concepts with the HeS 011, such as the Me 262 HG III often are shown with the engines in the wing root area or even buried in the wing rood ingesting air through slits in the leading edges.
The first German jet engines not only had radial single sided compressors they had radial inflow turbines which are just radial compressors running in reverse. von Ohain chose these because they tend to self balance the compressor and turbine.
In order to keep the diameter down (which the von Heinkel and Ohain worried about more than Whittle Rover RR) von Ohain added a single stage fan ahead of the radial compressor (without stator). Because they couldn't get enough compression and airflow to achieve performance goals they started to add axial stages after the radial compressor. This eventually evolved into the HeS 011A.
Part of the reason was that although the German air ministry had bet on axial jets they wanted to keep developing centrifugal gas turbines.
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- #400
Sometimes contemporary turbines use centrifugal in series with axial compressors, but always put the centrifugal after the axial as it's more effective at the high pressure end. On the other hand, as you say, the centrifugal gave "combat ruggedness and the ability to ingest turbulent air." In a combat situation, straightforward technical considerations may be less important than resistance to damage from flying shrapnel or other loose battlefield material. The Russians have taken that very seriously, see Foreign object damage - Wikipedia
"...The Russian Mikoyan MiG-29 and Sukhoi Su-27 fighters have a special intake design to prevent the ingestion of FOD during take-off from rough airfields. The main air intakes could be closed with mesh doors and special inlets on the top of the intakes temporarily opened. This would allow enough airflow to the engine for take-off but reduced the chances of the engine sucking up objects from the ground..."
