Zyzygie’s Mumbles and Rambles

stona · Dec 23, 2016

Juha2 said:
Istill doubt that they are claims, IIRC the first loss to Me 262 confirmed by Allied data was the 8 Aug 44 Mossie, the 3rd on the list. I don't have time to go through your list but when you combared it to the info given by Drgondog 7 years ago, they definitely seems to be claims, see: Which fighter brought the biggest new advantage when introduced? and his following two messages.

Juha

Schreiber's second claim for a Spitfire can't be confirmed from the Allied side. Maybe he had a 'sore throat'.
Cheers
Steve

stona · Dec 23, 2016

yulzari said:
Re the Nene sale to the Soviet Union. From memory so definitely 'IIRC' the Soviets were offering a large pile of foreign currency of which Britain was desperately short (hence the civilian food ration having been reduced to below the wartime level).

Exactly.

At the time, or shortly thereafter, concerns were raised about the sales, but the government response was that the engines were not secret and that the sale was a commercial transaction between Rolls Royce and the Soviet Union. See this extract from Hansard.

Jet Engines (Foreign Sales) (Hansard, 22 November 1948)

It might seem incredible to us, but, once again, we have a hindsight not afforded to the decision makers of the time.

Cheers

Steve

Juha2 · Dec 23, 2016

Magnon said:
Some useful data? can it be right?

...Loss figures from III./EJG 2, KG 51, and JG 7 were comparable. A comprehensive technical report by the technical officer of III. Gruppe, Oberinspektor Grote, compiled on March 3, 1945, listed the following causes for 42 aircraft losses:

pilot error 13
technical faults 19
enemy action 10

See p.89
Manfred Boehme. JG 7: The World's First Jet Fighter Unit 1944/1945. Schiffer Publishing, 1992.

This is an old note which I can't verify. It could be suspect.

Nothing wrong in your note, exactly as in the book.

Ps. but the text continued (Boehme's text): "Evaluation of surviving damage reports shows that in many cases the technical faults and resulting flyng accidents must be seen as direct results of improper handling by the pilot...

Zyzygie · Dec 23, 2016

The JUMO 004 was arguably still on a steep development curve when it was forced to enter service with the Me 262:

"In principle, development has now reached a stage where functionally the various parts of the engine are in order. However, due to the haste with which this development was carried out it is impossible to claim that there will be no more difficulties and that development is concluded. The difficulties we still have involve individual components of the engine and I would like to select only two from this group. One is the turbine. Recently we have had certain difficulties with the turbine wheel, with unexpected failures in the turbine blades due to vibration. The second component is the control system, and here I will touch on the problem of opening and closing the throttles, which was raised by the Reichsmarschall. I mentioned in Regensburg that we had things under control up to 8 km. Beyond that we are still somewhat unsure. But we have already flown to over 11 km. However it cannot be guaranteed with certainty that we will have the problem at upper altitudes rectified by the time series production begins, so that the pilot will be able to open and close the throttles without worrying about a flame-out."

In fact Junkers failed to eliminate this shortcoming before the engine entered production. Controlling the engine remained the great weakness of the 004 until the end of the war."

See p.37-38
Manfred Boehme. JG 7: The World's First Jet Fighter Unit 1944/1945. Schiffer Publishing, 1992

I believe that they did eventually solve the main turbine vibration problem:

"Later in 1943 the 004B version suffered turbine blade failures which were not understood by the Junkers team. They focussed on areas such as material defects, grain size and surface roughness. Eventually, in December, blade-vibration specialist Max Bentele was once again brought in during a meeting at the RLM headquarters. He identified that the failures were caused by one of the blades' natural frequencies being in the engine running range. His solution was to raise the frequency, by increasing the blade taper and shortening them by 1 millimeter, and to reduce the operating speed of the engine[6] from 9,000 to 8,700 rpm."

Wikipedia

Although hollow pressed metal blades operating in a hot environment would have an inherent problem, no matter how well balanced it was initially:

"The second was the turbine blades. These were, on production models, made from hollow folded ... alloy steel and spot welded. This means they [were liable] to warp slightly in use leading to imbalance of the turbine and wiping the bearings in operation. While a fairly ingenious method of cooling (passing air through the hollow blade space), it is also problematic and led to reduced engine life."

How many jets to have a decisive impact on the war? • Axis History Forum

Zyzygie · Dec 23, 2016

Juha2 said:
Nothing wrong in your note, exactly as in the book.

PS. but the text continued (Boehme's text): "Evaluation of surviving damage reports shows that in many cases the technical faults and resulting flyng accidents must be seen as direct results of improper handling by the pilot...

If that is right, then enemy action was literally the least of their worries on any given sortie.

Zyzygie · Dec 23, 2016

Zyzygie said:
Although hollow pressed metal blades operating in a hot environment would have an inherent problem, no matter how well balanced it was initially:

"The second was the turbine blades. These were, on production models, made from hollow folded manganese alloy steel and spot welded. This means they [were liable] to warp slightly in use leading to imbalance of the turbine and wiping the bearings in operation. While a fairly ingenious method of cooling (passing air through the hollow blade space), it is also problematic and led to reduced engine life."
How many jets to have a decisive impact on the war? • Axis History Forum

See attached

Fighterguy · Dec 24, 2016

Centrifugal compressors for gas turbine engines were a borrowed design from turbo-superchargers, a simple re-purposing and expansion of known technology. Axial compressors are far more efficient with a higher compression ratio, and higher temperatures, but required completely new and untried production methods. This is an example of existing manufacturing techniques and processes unable to meet new concepts. Seems the Germans plagued themselves with this often. Developing technologically advanced and unproven weapons programs, without the luxury of being a continent away, helped lead to their undoing.

Shortround6 · Dec 24, 2016

Actually the early axial compressors were not more efficient than the centrifugal compressor. In theory they may have been but in actual practice it took until the late 40s for an axial compressor to get past a 4;1 compression ratio in service form.
It wasn't just manufacturing techniques but actual compressor design. It is easy to say "just add stages until the desired pressure ratio ratio is reached" It is a lot harder to actually get the compressor disks/blades and stator blades to play well together. A Centrifugal compressor had one stage to deal with (at least in the beginning) The German jets were using 8 stages or 8 sets of compressor blades and 7-8 sets of stator blades, all different. get one set wrong and it screws up the entire set.
During testing some companies (not German) found that a particular set of blades actually lowered the pressure ratio rather than increased it. Any set of blades that went into stall condition choked the entire assembly.

Fighterguy · Dec 24, 2016

Shortround6 said:
Actually the early axial compressors were not more efficient than the centrifugal compressor. In theory they may have been but in actual practice it took until the late 40s for an axial compressor to get past a 4;1 compression ratio in service form.
It wasn't just manufacturing techniques but actual compressor design. It is easy to say "just add stages until the desired pressure ratio ratio is reached" It is a lot harder to actually get the compressor disks/blades and stator blades to play well together. A Centrifugal compressor had one stage to deal with (at least in the beginning) The German jets were using 8 stages or 8 sets of compressor blades and 7-8 sets of stator blades, all different. get one set wrong and it screws up the entire set.
During testing some companies (not German) found that a particular set of blades actually lowered the pressure ratio rather than increased it. Any set of blades that went into stall condition choked the entire assembly.

Correct! That was my point. The theoretical application couldn't be matched by contemporary production knowledge and materials. The British gas turbine engines used existing technology, whereas the Germans started from scratch in a sense.

Magnon · Dec 24, 2016

Shortround6 said:
Actually the early axial compressors were not more efficient than the centrifugal compressor. In theory they may have been but in actual practice it took until the late 40s for an axial compressor to get past a 4;1 compression ratio in service form.
It wasn't just manufacturing techniques but actual compressor design. It is easy to say "just add stages until the desired pressure ratio ratio is reached" It is a lot harder to actually get the compressor disks/blades and stator blades to play well together. A Centrifugal compressor had one stage to deal with (at least in the beginning) The German jets were using 8 stages or 8 sets of compressor blades and 7-8 sets of stator blades, all different. get one set wrong and it screws up the entire set.
During testing some companies (not German) found that a particular set of blades actually lowered the pressure ratio rather than increased it. Any set of blades that went into stall condition choked the entire assembly.

In the beginning the centrifugals were arguably
- Simpler
- Much more robust in terms of battlefield damage
- Much more resistant to surge
- Higher pressure ratio
- Higher thrust to weight ratio
Against that, they had a higher frontal area and hence drag, but the Meteor designers compensated for that by burying the engine in the wing.

Zyzygie · Dec 24, 2016

Fighterguy said:
Correct! That was my point. The theoretical application couldn't be matched by contemporary production knowledge and materials. The British gas turbine engines used existing technology, whereas the Germans started from scratch in a sense.

This extract from Welcome to the Frank Whittle Website may be relevant:

Whittle nevertheless filed the first patent for a turbo-jet on 16th January 1930... showing a 2 stage axial compressor feeding a single-sided centrifugal compressor. By the time he embarked on building an engine he had decided to simplify this to a single, double-sided centrifugal compressor.

Which was best? An axial compressor could achieve a higher efficiency under ideal conditions. It would have a smaller diameter, resulting in lower frontal area, lower blade tip speeds and the opportunity for an annular combustion chamber. Against this, it would be mechanically less robust and aerodynamically much more sensitive to both intake conditions and downstream pressure changes, such as those induced by rapid throttle movements. Both these could lead to blade stalling and resulting surges, which could in turn produce catastrophic blade failures. Pressure increase per row of blades was low, requiring at least 8 rows with intermediate stator blades. A centrifugal compressor would be simpler and cheaper to produce, would be more rugged and much more tolerant of the varying intake conditions and throttle changes encountered by a flight engine. It would need to run at higher speeds but there was the extensive experience of small centrifugal compressors developed as aero-engine superchargers, whilst there was little prior art on axials.

Zyzygie · Dec 26, 2016

For what it's worth, some relevant data for the Derwent, JUMO 004 and BMW 003:

Derwent

· Overall pressure ratio: 3.9:1

· Turbine inlet temperature: 1,560 °F (849 °C)

· Specific fuel consumption: Derwent IV 1.17 lb/lbf/hr (119.25 kg/kN/hr), Derwent V 1.02 lb/lbf/hr (103.97 kg/kN/hr)

· Thrust-to-weight ratio: Derwent IV 2.04 lbf/lb (0.0199 kN/kg), Derwent V 3.226 lbf/lb (0.0316 kN/kg)

· Military, static: Derwent IV 2,000 lbf (8.90 kN) at 16,600 rpm at sea level, Derwent V 3,500 lbf (15.57 kN) at 14,600 rpm at sea level

· Cruising, static: Derwent IV 1,550 lbf (6.89 kN) at 15,400 rpm at sea level, Derwent V 3,000 lbf (13.34 kN) at 14,000 rpm at sea level

· Idling, static: Derwent IV 120 lbf (0.53 kN) at 5,500 rpm at sea level, Derwent V 120 lbf (0.53 kN) at 5,500 rpm at sea level

JUMO 004

· Maximum thrust: 8.8 kN (1,980 lbf) at 8,700 rpm

· Overall pressure ratio: 3.14:1

· Specific fuel consumption: 1.39 N/(N·hr)

· Thrust-to-weight ratio: 1.25 (12.2 N/kg)

BMW 003

· Maximum thrust: 7.83 kN (1,760 lbf) at 9,500 rpm at sea level for take-off

· Overall pressure ratio: 3.1:1

· Turbine inlet temperature: 770 °C (1,418 °F)

· Specific fuel consumption: 142.694 kg/kN/hr (1.4 lb/lbf/hr)

· Thrust-to-weight ratio: 12.5 N/kg (1.282 lbf/lb)

· Normal, static: 6.89 kN (1,550 lbf) / 9,000 rpm / sea level

· Military flight: 6.23 kN (1,400 lbf) / 9.500 rpm / 2,500 m (8,202 ft) / 900 km/h (559 mph; 486 kN)

· Normal, flight: 2.85 kN (640 lbf) / 11,500 rpm / 11,000 m (36,089 ft) / 900 km/h (559 mph; 486 kN)

Magnon · Jan 2, 2017

GrauGeist said:
Even if the Luftwaffe had 1,000 Me262s fully equipped with all the fuel they needed, endless ammo supply, all the qualified pilots to fly them and an endless supply of parts, the Allies still would have overwhelmed them with the 1,000 plus bomber stream and hundreds of fighters on escort rotation and the rest on CAP missions.

And this was each day...

"I'll never change an opinion I've expressed often, that with just 300 Messerschmitt Me 262 jet fighters we could have on any day shot down a minimum of 200 bombers," said Galland. "If this could have continued for even a fortnight, then the day bombing would have had to be halted." Galland called the "blitz bomber" idea "a typical Hitler error."

The idea of making the Me 262 a bomber had genuine consequences and possibly owes less to Hitler than to engineer-planemaker Wilhelm E. "Willy" Messerschmitt, whose company created the jet, although Messerschmitt himself had no role in designing it. On Sept. 7, 1943, granted a rare audience with the Fuehrer, Messerschmitt expressed mixed feelings about the jet and repeated his longstanding request that top priority be accorded to the Me 209-II propeller-driven fighter.

The Messerschmitt Me 262 Jet Fighter | Defense Media Network
https://fighterba.se/portfolio/messerschmitt-me-262a-1-schwalbe/

stona · Jan 2, 2017

Galland is hardly a reliable witness, far more concerned after the war with distancing himself from the regime and blaming everyone but himself for the failings of the force he commanded. He usually blamed men who are dead, and therefore not in a position to defend themselves.
Actually, facing invasion, the use of the Me 262 as a fast bomber seems perfectly reasonable to me, as it did to other senior Luftwaffe figures apart from Galland.
There are many reasons so few Me 262s were produced and why they were so late, most can be laid firmly at Messeschmitt's door.
Cheers
Steve

Zyzygie · Jan 2, 2017

stona said:
Galland is hardly a reliable witness, far more concerned after the war with distancing himself from the regime and blaming everyone but himself for the failings of the force he commanded. He usually blamed men who are dead, and therefore not in a position to defend themselves.
Actually, facing invasion, the use of the Me 262 as a fast bomber seems perfectly reasonable to me, as it did to other senior Luftwaffe figures apart from Galland.
There are many reasons so few Me 262s were produced and why they were so late, most can be laid firmly at Messeschmitt's door.

Cheers
Steve

Steve,
Galland KNEW that the Me262 was useless as a bomber. The location of the cockpit in the middle of the fuselage over the wings meant that they could not even see the target land a bomb in the right zip code, let alone do any real damage.
Cheers

Denniss · Jan 2, 2017

It makes no sense to produce a thousand more Me 262 if you don't even have sufficient engines to power the historically built ones.
The bomber idea by Hitler/Mtt had no influence on production as the engines were not ready - either not mass-producable due to lack of strategic materials or by far not reliable enough (alternative version with less stragic mats)

stona · Jan 2, 2017

Zyzygie said:
Steve,
Galland KNEW that the Me262 was useless as a bomber. The location of the cockpit in the middle of the fuselage over the wings meant that they could not even see the target land a bomb in the right zip code, let alone do any real damage.
Cheers

Like the Typhoon, P-47, Hurricane, Spitfire, F4U, Fw 190 etc. etc.?

It was useless as a level bomber from 3,000m, as it was used around D-Day, mainly because it was still supposed to be secret, but as a fighter bomber it may have been far from useless.
There are plenty of British accounts of attacks by the Me 262s of KG 51 which were sometimes effective and always caused consternation. The RAF Wing that moved forward to the airfield at Grave (No. 125 Wing), in October 1944, was so harassed by the fighter bomber Me 262s that it was forced to withdraw to Melsbroek, nearer Brussels, three weeks later.
Cheers
Steve

Zyzygie · Jan 3, 2017

stona said:
Like the Typhoon, P-47, Hurricane, Spitfire, F4U, Fw 190 etc. etc.?

It was useless as a level bomber from 3,000m, as it was used around D-Day, mainly because it was still supposed to be secret, but as a fighter bomber it may have been far from useless.
There are plenty of British accounts of attacks by the Me 262s of KG 51 which were sometimes effective and always caused consternation. The RAF Wing that moved forward to the airfield at Grave (No. 125 Wing), in October 1944, was so harassed by the fighter bomber Me 262s that it was forced to withdraw to Melsbroek, nearer Brussels, three weeks later.
Cheers
Steve

All those aircraft had an engine in front.
They had no choice of putting the cockpit forward...
No jet fighter designer since has been stupid enough to copy the ME 262 model.

stona · Jan 3, 2017

Zyzygie said:
All those aircraft had an engine in front.
They had no choice of putting the cockpit forward...

True, but not the point. It didn't prevent them from being effective fighter bombers, and it didn't stop the Me 262 being one either.

Does the position of the Me 262 cockpit relate to the armament? Bear in mind that compared to more modern aircraft it is small, the fuselage is quite shallow (put one next to a Meteor!)

Cheers

Steve

Milosh · Jan 3, 2017

The 262 had C/G problems. If the cockpit had been moved forward then the fuel tank in front of the cockpit would have had to be moved to behind the cockpit further messing up the C/G.

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