Zyzygie’s Mumbles and Rambles

cimmex said:

Why a more bulky Centrifugal compressor engine with around the same thrust? In my opinion it would be a step back in the evolution.
cimmex

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For one, the technology of centrifugal compressors was more mature at the time. Centrifugal compressors are still used in new engines, especially in smaller sizes, as they scale down better.

swampyankee said:

For one, the technology of centrifugal compressors was more mature at the time. Centrifugal compressors are still used in new engines, especially in smaller sizes, as they scale down better.

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Also the contemporary jets were susceptible to "surge," or effectively stall of the compressor blades. This problem wasn't really finally overcome in axial flow engines until the 60s. The centrifugal compressor was much less susceptible and hence was the pragmatic way to go at the time.

Zyzygie said:

Also the contemporary jets were susceptible to "surge," or effectively stall of the compressor blades. This problem wasn't really finally overcome in axial flow engines until the 60s. The centrifugal compressor was much less susceptible and hence was the pragmatic way to go at the time.

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Surge is a problem in both centrifugal and axial flow compressors, but it's significantly easier to deal with in a centrifugal unit. Usually, though, modern axial flow engines will have significant variable geometry, such as inlet guide vanes, and anti-surge bleeds to deal with it.

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Zyzygie said:

Also the contemporary jets were susceptible to "surge," or effectively stall of the compressor blades. This problem wasn't really finally overcome in axial flow engines until the 60s. The centrifugal compressor was much less susceptible and hence was the pragmatic way to go at the time.

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Care to quantify your statement that was painted with a brush as wide as a 4 lane highway?

FLYBOYJ said:

Care to quantify your statement that was painted with a brush as wide as a 4 lane highway?

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The centrifugal was much more robust, not only for resisting surge, but also for ingesting Canadian ducks and 50mm Swiss hailstones!
See attachment.

Zyzygie said:

The centrifugal was much more robust, not only for resisting surge, but also for ingesting Canadian ducks and 50mm Swiss hailstones!
See attachment.

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You're blowing smoke - what specific engines? When? How many? Yes, a centrifugal compressor is much more robust, but to generalize with little specifics is nonsense as that clip you posted.

Admiral Beez said:

The intended opponent of the 262 was heavy bombers.

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The original concept of the Me262 was to be a true fighter.
When the 262 was first put to paper, Messerschmitt had virtually no idea about how a jet aircraft would perform versus the known qualities of piston powered aircraft (other than the performance data gleaned from Heinkel's He178 and He280), and thus designed the 262 around what little was known about high-speed flight.

FLYBOYJ said:

You're blowing smoke - what specific engines? When? How many? Yes, a centrifugal compressor is much more robust, but to generalize with little specifics is nonsense as that clip you posted.

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I assume that you haven't read the attachment. I tried to open it with my iPhone with no luck, but it's fine from my computer...

Also, apart from the advantage in terms of surge resistance, the Derwent had a higher pressure ratio and operating temperature than the JUMO.

GrauGeist said:

The original concept of the Me262 was to be a true fighter.
When the 262 was first put to paper, Messerschmitt had virtually no idea about how a jet aircraft would perform versus the known qualities of piston powered aircraft (other than the performance data gleaned from Heinkel's He178 and He280), and thus designed the 262 around what little was known about high-speed flight.

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And the He 280 offered darn little to the design of the Me 262. The He 280 flying for the first time under power in March of 1941 and the 262, using a Jumo 210 in the nose flying the next month. it would be another year before the 262 flew with jet engines, it was at the end of 1942 that the 3rd He 280 flew.
Both programs were running at the same time and development of both was slow due to a lack of flyable engines so I don't really see a whole lot of back and forth between the programs.

Zyzygie said:

I assume that you haven't read the attachment. I tried to open it with my iPhone with no luck, but it's fine from my computer...

Also, apart from the advantage in terms of surge resistance, the Derwent had a higher pressure ratio and operating temperature than the JUMO.

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I have - and you're only talking about specific early engines, basically cherry picking.

"contemporary jets were susceptible to "surge," or effectively stall of the compressor blades. This problem wasn't really finally overcome in axial flow engines until the 60s."

J-35? J-47? Orenda? RR Avon?

Shortround6 said:

And the He 280 offered darn little to the design of the Me 262. The He 280 flying for the first time under power in March of 1941 and the 262, using a Jumo 210 in the nose flying the next month. it would be another year before the 262 flew with jet engines, it was at the end of 1942 that the 3rd He 280 flew.
Both programs were running at the same time and development of both was slow due to a lack of flyable engines so I don't really see a whole lot of back and forth between the programs.

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Agreed.
The 262's wing was even "swept" back during development not for performance, but to adjust the CoG with the change in engines.
On the otherhand, the He280 with it's elliptical wing, offered far better performance in a "turning fight" situation than the Me262.

GrauGeist said:

Agreed.
The 262's wing was even "swept" back during development not for performance, but to adjust the CoG with the change in engines.
On the otherhand, the He280 with it's elliptical wing, offered far better performance in a "turning fight" situation than the Me262.

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I'd like to see a well-built and sorted Heinkel He 162 Volksjager vs. a Meteor. I imagine the 162 offers a much tighter dogfighting ability over the 262.

FLYBOYJ said:

I have - and you're only talking about specific early engines, basically cherry picking.

"contemporary jets were susceptible to "surge," or effectively stall of the compressor blades. This problem wasn't really finally overcome in axial flow engines until the 60s."

J-35? J-47? Orenda? RR Avon?

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OK - a few instances:

Powerplant: 1 × Pratt & Whitney J57-P-21/21A turbojet:

However, the Super Sabre's extremely high accident rate—typically caused by compressor stalls, wing fractures, and persistent yaw instability—was even deadlier. More than 889 F-100s were lost in accidents out of 2,294 built, killing 324 pilots.
Rolls-Royce Avon engine:Edit

The Rolls-Royce Avon turbojet engine was affected by repeated compressor surges early in its 1940s development which proved difficult to eliminate from the design. Such was the perceived importance and urgency of the engine that Rolls-Royce licensed the compressor design of the Sapphire engine from Armstrong Siddeley to speed development.
The engine, as redesigned, went on to power aircraft such as the English Electric Canberrabomber, and the de Havilland Comet and Sud Aviation Caravelle airliners.
Olympus 593:Edit

During the 1960s development of the Concorde Supersonic Transport (SST) a major incident occurred when a compressor surge caused a structural failure in the intake. The hammershock which propagated forward from the compressor was of sufficient strength to cause an inlet ramp to become detached and expelled from the front of the intake.[4] The ramp mechanism was strengthened and control laws changed to prevent a re-occurrence.[5
U.S. Navy F-14 crashEdit

A compressor stall contributed to the 1994 death of Lt. Kara Hultgreen, the first female carrier-based United States Navy fighter pilot. Her aircraft, a Grumman F-14 Tomcat, experienced a compressor stall and failure of its left engine, a Pratt & Whitney TF30turbofan, due to disturbed airflow caused by Hultgreen's attempt to recover from an incorrect final approach position by executing a sideslip; compressor stalls from excessive yaw angle were a known deficiency of this type of engine.
]

Zyzygie said:

OK - a few instances:

Powerplant: 1 × Pratt & Whitney J57-P-21/21A turbojet:

However, the Super Sabre's extremely high accident rate—typically caused by compressor stalls, wing fractures, and persistent yaw instability—was even deadlier. More than 889 F-100s were lost in accidents out of 2,294 built, killing 324 pilots.
Rolls-Royce Avon engine:Edit

The Rolls-Royce Avon turbojet engine was affected by repeated compressor surges early in its 1940s development which proved difficult to eliminate from the design. Such was the perceived importance and urgency of the engine that Rolls-Royce licensed the compressor design of the Sapphire engine from Armstrong Siddeley to speed development.
The engine, as redesigned, went on to power aircraft such as the English Electric Canberrabomber, and the de Havilland Comet and Sud Aviation Caravelle airliners.
Olympus 593:Edit

During the 1960s development of the Concorde Supersonic Transport (SST) a major incident occurred when a compressor surge caused a structural failure in the intake. The hammershock which propagated forward from the compressor was of sufficient strength to cause an inlet ramp to become detached and expelled from the front of the intake.[4] The ramp mechanism was strengthened and control laws changed to prevent a re-occurrence.[5
U.S. Navy F-14 crashEdit

A compressor stall contributed to the 1994 death of Lt. Kara Hultgreen, the first female carrier-based United States Navy fighter pilot. Her aircraft, a Grumman F-14 Tomcat, experienced a compressor stall and failure of its left engine, a Pratt & Whitney TF30turbofan, due to disturbed airflow caused by Hultgreen's attempt to recover from an incorrect final approach position by executing a sideslip; compressor stalls from excessive yaw angle were a known deficiency of this type of engine.
]

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Still meaningless - compare those handful of instances to the amount of fleet flight hours and at the end that will tell you if this was truly an issue. The F-100 for example, did have a high attrition rate but you do not show compressor stalls compared to the rest of the aircraft lost. I think you'll find with the F-100, many of the crashes involved "C" models which had no wing flaps.

fastmongrel said:

Only if the Royal Navy built HMS Habakkuk

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Admiral Beez said:

The intended opponent of the 262 was heavy bombers. What was the intended opponent of the Meteor? Insufficient range to escort bombers over Europe and no bombers to shoot down. I get the sense that the Meteor was built because the technology was there, and having a jet fighter seemed like a prudent idea, rather than it having a purpose like the interceptor 262.

This seems akin to a F-106 vs a MiG-21.

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I don't think the Meteor had an intended target, it was an effort to get some form of jet powered aircraft operational as soon as possible.

pinehilljoe said:

I don't think the Meteor had an intended target, it was an effort to get some form of jet powered aircraft operational as soon as possible.

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I guess what I am getting at, was the Meteor optimized for maneuverability or speed? Is it set up to fight the 262? The armament seems ideal for dog fighting.

Maaan, there are so many things I'd like to add to this thread... Firstly though, the specification that the meteor was built to, F.9/40, dated 14/11/40. Here is text lifted directly from it:

"The DTD requires the development of a single-seat fighter utilising the Whittle system of jet propulsion. The salient advantage of this system of propulsion is the possiblity of speeds particularly at high altitudes which it would not be possible to obtain by the orthodox arrangement of engine and airscrew. To make full use of the possibilities available a small aeroplane is essential.It is vital for the success of he project that every item of service equipment which is not absolutely essential should be eliminated. This specification is issued to cover the design and construction of a twin engined single-seat fighter to develop the application of jet propulsion to a service aeroplane.

Performance: The maximum speed at 30,000ft shall not be less than 430mph. When taking off from a grass surface with full fuel and military load the aircraft shall be capable of crossing a 50ft screen within a distance of 600 yards in stillair. On landing the aircraft should come to rest in not more than 700 yards, with full fuel and military load."

The rest goes into armament, "six 20mm cannon guns each with 120 rounds, or with four guns, 150 rounds per gun is required.", engine type and radio equipment. That's it. A jet fighter, no less.

The Me 262 evolved from two initial design studies, the Messerschmitt P 65 and P 1065, powered by two BMW P.3304 engines. Both were straight winged aircraft of the same configuration as the 262 and in the latter, the triangular cross section of the 262's fuselage, the 'dreiecke Rumpfform', imposed by the drawing office owing to concerns about undercarriage stowage by Voigt was in place. Messerschmitt himself wanted the 'ovale Rumpfform' of the P 65, but it seems the former won the day in the end.

Discussions for a single-seat jet fighter within Messerschmitt staff began in October 1938 and the Technical Office of the RLM offered a requirement on 4 January 1939, titled Vorlaufige technische Richtlinien fur schnelle Jagdfluzeuge mit Stahltriebwerk (Preliminary technical criteria for a high speed fighter aircraft with a jet engine). I don't have a direct quote from the spec, but what is outlined in books on the 262 is that two versions were proposed, one for a high-speed pursuit and the other for target defence. This is translated from the spec, however:

"Operational Deployment (for operations against aerial targets) a) High speed Fighter b) Intercept Fighter [Heimatschutzer]
Number and type of powerplant: One turbojet engine (make unspecified)"

The rest goes into armament, radio and performance: "Maximum speed 900km/h (559mph) Landing speed: possibly not over 120km/h (75mph)". In the text the initial design considerations were for a twin tail boom fighter like the Focke Wulf Flitzer or the DH Vampire. Voigt assessed that a twin engined design was more practicable and work began on the P 1065 on 1 April 1939. The first incarnation of a swept wing appeared on the P 65 in February 1940.

For fear of turning this into a wall of text, regarding the centrifugal versus axial argument, its worth noting that prototype Meteors were fitted with de Havilland jet engine, or Halford H.1 after its designer, the brilliant Frank Halford, also responsible for the Napier Sabre and de Havilland Gipsy engines (some portoflio!) and a Metrovick F.2 axial flow engine. The H.1 powered prototype DG206/G was in fact the first Meteor to fly, on 5 March 1943. The first Metrovick F.2 powered Meteor, DG204/G first flew on 13 November 1943. The first Whittle engined Meteor, DG202/G powered by two Rover W.2Bs first flew on 24 July 1943.

The DH engined Meteor flying first took place because of the political nonsense between Power Jets Ltd, Whittle's firm, and Rover, with whom he had contracted to build the W.2 jet engine. After Rolls-Royce got involved ("Don't worry, we'll design the simplicity out of it" - Ernest Hives of RR after being told by Whittle of its design concept), before the Meteor's first flight, at this stage still known as the Gloster F.9/40 after the spec laid out to build it, the firm manufactured the W.2 Welland to go into the Meatbox.

Fitting the axial flow engines to the Meteor was not overly successful as it was slower, but not because of the engines themselves, but the installation on the wing. The centrifugal engines sat in front of the main spar, whereas the F.2 had to sit below the spar, which led to a longer undercarriage installation. DG204/G was lost in an accident in January 1944 owing to a compressor failure during aerobatic manoeuvres. Performance losses over the centrifugal Meteors were not excessive, but were notable,, top speed was 25mph below the others and rate of climb was 15 percent less - profile drag of the underslung nacelles was more than predicted.

At this stage its worth considering how each aircraft handled from a pilot's standpoint and who better to offer this information than our favourite forum test pilot (!), the Late Eric 'Winkle' Brown. There's no better choice for this since he flew both types at around the same time in an official capacity as a test pilot, so his recollections are worthy of adding here.

Brown flew most variants of the Meteor, including specialised post-war variants, such as the prone-pilot Meteor and first turbo-prop aircraft, a Meteor with RR Trent propeller installations, which he commented very favourably on, as well as the F.8, which we won't include in our discussion owing to its post-war pedigree, but what he does say is that the RR Derwent installation utterly changed the Meteor's performance decidedly for the better.

"Soon after my arrival at R.A.E. I flew Meteor EE214/G, ths becoming the first naval pilot ever to fly a jet aircraft. Exciting as that event was for me, it could not conceal the fact that the Meteor I was a rather mediocre aeroplane from the handling standpoint. Besides being underpowered, it had heavy ailerons, suffered from directional instability, and had terrible forward view in rain."

Brown doesn't have much more to say about the early incarnations of the jet, merely to comment on the tests he carried out that were cautious research into behavioural characteristics of jet powered airframes. This is his conclusion in Wings of the Weird and Wonderful (Airlife, 1983) on the Meteor chapter and is worth reading from a comparison with the '262 standpoint:

"The Meteor was a worthy holder of the title of Britain's first operational jet aeroplane and because of its amazing adaptability survived in service in various forms for 25 years. At the outset it was hardly in the same class as Germany's counterpart, the Messerschmitt Me 262, but it improved to become a very snappy performer although even at its peak, never reaching the apex of the Me 262. It was the aircraft on which many of Britain's service pilots got their first taste of jet flying, but it was hardly a docile trainer for it had an Achilles heel - a high single-engine safety speed because its two powerful engines were too widely separated. This characteristic cost lives and gave the Meteor the reputation of an aircraft that had to be flown with respect."

Now, the Me 262. Brown has enormous praise for this aircraft (that bias that people bang on about here at work, perhaps), and the chapter on the Me 262 in Wings of the Luftwaffe (MacDonalds and Janes, 1977 - Hikoki reprint) is far more extensive and thus revealing than that of the Meteor in Wings of the Weird and Wonderful, so I won't be going into every detail; you guys are gonna have to buy these books for that stuff.

"If asked to nominate the most formidable combat aircraft to evolve in WW2, I would unhesitatingly propose Messerschmitt's Me 262. I say 'unhesitatingly' advisedly, despite having flown the Spitfire in virtually all of its variants, the Mosquito, the Lancaster, the Mustang and even Mitsubishi's Zero-Sen; all warplanes that might be considered as contenders for this accolade."

"I was immediately struck by its beautiful, yet sinister lines, which reminded me vividly of those of a shark."

"The take-off run was long and the aircraft gave one the feeling that it was underpowered, as indeed was the Meteor I."

"Our interest in the Me 262 at RAE Farnborough was threefold. Firstly, we were intrigued to discover if the performance really did match the capabilities claimed by the Germans; secondly we were anxious to discover the behaviour of the swept-wing configuration at high mach numbers, and thridly we wanted to know if this aircraft provided a good gun platform. We soon ascertained that the German figures were by no means extravagant, but the high mach performance must, of course, be related to the contemporary state of art."

"The important thing, however was that I had ascertained the tactical usability of the Me 262 up to Mach.82, and this capability had undoubtedly endowed Messerschmitt's fighter with a marked advantage over every other operational aircraft of WW2."

Brown then goes into directional snaking, which is of course interesting reading, but I'm not gonna transcribe the whole article. His closing is full of admiration for the jet.

"It was in my view unquestionably the foremost warplane of its day; a hard hitter which outperformed anything we had immediately available but which, fortunately for the Allies, was not available to the Luftwaffe in sufficient numbers to affect drastically the course of events in the air over Europe. It was a pilot's aeroplane, which had to be flown and not just heaved into the air. Basically underpowered and fitted with engines sufficiently lacking in reliability to keep the adrenaline flowing, it was thoroughly exciting to fly, and particularly so in view of its lack of an ejector seat. I was reminded vividly of this aircraft when I first flew the F-4 Phantom some 20 years later."