Right...the 262 would or should employ its speed in a single pass at an enemy fighter and never try to turn with one. The Me-262 was an interceptor of bombers, not a jet "fighter."
Which jet was better, the Me 262 or the Gloster Meteor?
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Right...the 262 would or should employ its speed in a single pass at an enemy fighter and never try to turn with one. The Me-262 was an interceptor of bombers, not a jet "fighter."
With regard to the Jumo 004 engines, it is reported in Design Analysis of Me 262 Jet Fighter Part II that the wall thickness of the mild steel flame tubes was 0.91 mm. The engines operated at a pressure of about 300 kPa and a temperature of 775 degrees C. At that temperature steel has only about 15% of its normal strength. That's what I call "sailing close to the wind."
It's no wonder they had a limitation of 10 minutes at full power imposed on them.
Suggesting otherwise is something out of cloud cuckoo land.
It's no wonder they had a limitation of 10 minutes at full power imposed on them.
Suggesting otherwise is something out of cloud cuckoo land.
Kurfürst
Staff Sergeant
With all respect, I would rather trust the engineers the engineers who designed it for that thickness... perhaps they knew better.
And that silly comment on "10 minutes imposed on its used".... begs for the question why the Meteor has to be "limited" to 5 minutes only..?
(Of course the answer is that 5/10 minutes were the design practice in both countries for max power, for every combat plane... rather than some non-existent connection between cover sheet thickness, and possible periods of operation)
And that silly comment on "10 minutes imposed on its used".... begs for the question why the Meteor has to be "limited" to 5 minutes only..?
(Of course the answer is that 5/10 minutes were the design practice in both countries for max power, for every combat plane... rather than some non-existent connection between cover sheet thickness, and possible periods of operation)
drgondog
Major
Edger Schmeud - the designer for the Mustang was also the head of design for the F-86.. which 'German' engineers did you have in mind as the F-86 major contributor?
If you revise your statement to say Schmeud was influenced by 262 design sweep and leading edge slats you be closer to the facts.
tail end charlie
Senior Airman
- 615
- Aug 24, 2010
The 262 wing sweep makes it as advanced as a douglas dakota, the sweep was to adjust the CofG not to reduce drag at high speed
OK. Conceded, but German engineering including swept-wing research data went off to the US. The name Edger Schmued (German-born US citizen) may have misled me in this regard.
Regards,
Magnon
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drgondog
Major
That has nothing to do with my comment. Having said that if the only reason was to adjust the center of LIFT to accomodate the cg, they could have adjusted the cg in different ways.
The wing wind tunnel data was extensively reviewed by Edgar Schmeud and the resultant wing design on the F-86 was both to delay transonic drag rise (sweep) as well as improve low speed and turning qualities (leading edge slats).
tail end charlie
Senior Airman
- 615
- Aug 24, 2010
Everything I have read on the 262 says the wing sweep was to adjust for heavier than expected engines and that the wing sweep on a 262 would have little effect. The DC3 Dakota has swept wings
drgondog
Major
I don't really understand what your point of view is regarding 'wing sweep on a 262 would have little effect'.
1. it would move the center of lift (aerodynamic center of the wing) aft from a straight wing design. This would change the static margin (the relationship between cg and ac), change the necessary relationship of the horizontal stabilzer on pitch effectiveness. Do you consider these effects negligible?
2. it would increase the aircraft speed capability before experiencing transonic drag by effectively reducing the t/c ratio (and the velocity component chordwise). It would have the effect of raising the Mcr. Is this not important in your mind?
3. both of those effects were 'significant' not 'little'.
as for the C-47 it was 'little' not significant - but it (sweep) also had the effect of moving the aerodynamic center of the wing a little bit aft in comparison with a zero sweep wing.
tail end charlie
Senior Airman
- 615
- Aug 24, 2010
Hi Magnon
probably my bad wording, the wing sweep was for your point no 1 (obviouslly important) but the actual sweep used was not sufficient to make a substantial difference to the transonic performance (your point 2) as below.
from Messerschmitt Me 262 Schwalbe / Sturmvogel
quote
Swept wings had been proposed as early as 1935 by Adolph Busemann, and Willy Messerschmitt had researched the topic from 1940. In April 1941, he actually proposed to fit a 35° swept wing (Pfeilflügel II) to the Me 262. Though this suggestion was not implemented, he continued with the projected HG II and HG III high-speed derivatives of the Me 262 in 1944, which were designed with a 35° and 45° wing sweep respectively. The production Me 262 had a leading edge sweep of 18.5° primarily to properly position the center of lift relative to the center of mass and not for the aerodynamic benefit of increasing the critical Mach number of the wing (the sweep was too slight to achieve any significant advantage). The aircraft was originally designed as a tail-dragger which it was built as in the first (Me 262 V1) through fourth (-V4) prototypes, but it was discovered on an early test run that the engines and wings "blanked" the stabilizers, giving almost no control on the ground. Changing to a tricycle landing gear arrangement, firstly as a fixed undercarriage on the fifth prototype aircraft, then a fully retractable one on the sixth and succeeding prototypes, corrected all of these problems immediately.
unquote
It seems that the 262 was used for tests with higher sweep which certainly would have improved the transonic performance.
I mentioned the Dakota as its wings were swept for similar reasons, to adjust CofG/Cof Lift
drgondog
Major
The effective chordwise flow component for an 18 degree sweep is .951057 Vfreestream -
V=Vfs x cosine 18%. This says that the velocity over the wing, parallel to the aircraft CL axis, in a wing chord wise direction - is .95% of the same flow for a straight wing of same airfoil, as a function of freestream velocity.
Further what it means that as the Me 262 was enetering Critical Mach for a straight wing, it was only at 95% of the velocity required for critical mach with the 18 degree sweep.
Hence ~ 5% increase in Mach crit over the swept Me 262 wing. Not insignificant
tail end charlie
Senior Airman
- 615
- Aug 24, 2010
From the figures I have seen the 262 had a critical mach number of about 0.84 to 0.86 with its swept wings similar to a spitfire where I have seen 0.86 to 0.89 mentioned. Whether the sweep is significant depends on the eventual aim since the 262 never had enough power to reach its critical mach number in level flight.
A 5% reduction in drag is useful, but as I said everything I have read the sweep wasnt introduced for aerodynamic reasons . If the original design (with straight wings) had 5% more drag then it was not as aerodynamic as many prop designs but it probably wasnt intended to be. The 262 was the "first off" to prove jet engines the next generation were proposed to have the jets in the fuselage and 35-45 degree swept wings.
drgondog
Major
TEC - It wasn't a 5% reduction in drag, it was a 5% increase in speed (or delay to effect) before Mcr was reached - and it definitely was reached in a dive in the .82M-.87M range.
As to everything you have read - is that the same as 'read everything written'? particularly by the Me 262 designers - versus the author that wrote Stormbirds? I can almost (but not quite as I have not read everything that was written about the design choices made) that the sweep was selected for more than just shifting the aeordynamic center of lift movement slightly aft.
The Me 262 was cleaner than the Mustang and the Mustang was the cleanest of the conventional aircraft of WWII. It was definitely intended to be extremely clean.
BTW aeros would kill their mothers for a decrease of 5% in drag - it is that 'useful'!
tail end charlie
Senior Airman
- 615
- Aug 24, 2010
Just looking at the 262 it is clear it was clean, and of course a 5% increase in speed is more than useful and significant however in term of aircraft (like the sabre) capable of breaking the sound barrier which is how this conversation started, the sweep on the operational 262 wasnt significant however the sweep on the proposed modifications was very much like a sabre, but this wasnt built.
from The Messerschmitt Me-262 Schwalbe / Sturmvogel
quote
* Several other variants were considered but not built. The "Me-262 HG" featured wings with greater sweepback for high-speed performance and a "vee" or "butterfly" tail.
unquote
I am not a pilot but I would imagine if an engine stops on a 262 it would pull to one side, unless the pilot can correct this immediately with a swept wing there would be a huge reduction in airflow and lift from the side with no engine running.
tail end charlie
Senior Airman
- 615
- Aug 24, 2010
Parsifal sorry its an old post but I didnt see it
I think a major part of thinking on the allies side was developing technology safely, I read that of the first 12 shooting stars made, at least 2 crashed killing the pilot (2 from 12 is like a combat situation), and both British and German jet programmes suffered losses to engine problems too. Aeroplanes which kill such a large number of top class pilots must have been regarded as suspect and so wherever possible British and Americans would be conservative while the Germans facing defeat would take the risk.
From DESIGN FOR AIR COMBAT
Also there are stuctural implications for swept wings. All things being equal, the deflection of a uniformly loaded cantilever (which the wing approximates) is a function of the fourth power of the length. A swept wing of a given span is necessarliy longer than a straight wing. For a 18.5 degrees sweep, assuming constant cross-section, that would result in over 20% greater deflection, not taking into account the greater (around 50%) wing loading of the Me 262.
There are other factors: see The Penalties of Sweepback in DESIGN FOR AIR COMBAT
Overall, it seems the gains were minimal and the penalties were significant.
The Messerschmitt ME 262
"The more conventional Me 262 was originally designed with straight wings. But, because it was one of the world's first high speed aircraft not to have the forward weight concentration of piston engines, it turned out to be tail heavy. In order to restore the balance between the lift and mass centres, the wing outboard of the engine nacelles was swept back, as it had been on the DC3 airliner for similar reasons. Eventually the Me 262 was given a leading edge sweepback of 18.5 degrees across the span, a modest sweep which had little effect on drag..."
Also there are stuctural implications for swept wings. All things being equal, the deflection of a uniformly loaded cantilever (which the wing approximates) is a function of the fourth power of the length. A swept wing of a given span is necessarliy longer than a straight wing. For a 18.5 degrees sweep, assuming constant cross-section, that would result in over 20% greater deflection, not taking into account the greater (around 50%) wing loading of the Me 262.
There are other factors: see The Penalties of Sweepback in DESIGN FOR AIR COMBAT
Overall, it seems the gains were minimal and the penalties were significant.
The Messerschmitt ME 262
With Allied aircraft operating in ever-increasing numbers over the Reich, operational evaluation of the Me-262 had been difficult, to say the least. Trying to work the bugs out of an aircraft while dodging enemy fighters was far from an ideal situation for flight test.
The evaluation did show that the Me-262 was not only fast but was responsive and docile. However, it did tend to "snake" at high speeds, reducing its accuracy as a gun platform, and it was underpowered, with a long take-off run. Losing an engine was very dangerous, since the Me-262 could barely stay in the air on one engine. If an engine was lost below 290 KPH (180 MPH), the aircraft would usually be lost as well. The engines were also not very reliable, being prone to flameouts and burnouts.
The evaluation did show that the Me-262 was not only fast but was responsive and docile. However, it did tend to "snake" at high speeds, reducing its accuracy as a gun platform, and it was underpowered, with a long take-off run. Losing an engine was very dangerous, since the Me-262 could barely stay in the air on one engine. If an engine was lost below 290 KPH (180 MPH), the aircraft would usually be lost as well. The engines were also not very reliable, being prone to flameouts and burnouts.
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The Me-262 was highly vulnerable on takeoff and landing since the Jumo engines took a long time to throttle up, and since the engines tended to set asphalt runways on fire, the Me-262 was restricted to operations at airfields with concrete runways. On 7 October two were shot down on takeoff by Lieutenant Urban L. Drew of the USAAF, flying a P-51 Mustang. The Luftwaffe eventually assigned FW-190s, when they were available and had fuel, to fly air patrols around the air bases to protect the Me-262s, and the airfields were ringed by heavy flak defenses. The flak installations were a mixed blessing, however, since they were often staffed by poorly-trained and nervous troops who were just as likely to fire on friends as foes.
Many of the Me-262 pilots were also inexperienced, and flying an aircraft with performance greater than any operated before would have been a challenge to more professional aviators. Hitting Allied bombers while streaking through a formation at high speed was difficult, and if an Me-262 pilot slowed down to take more careful aim, he became a good target for the bombers' defensive fire and escorting Allied fighters.
The Messerschmitt ME 262
THE 456th FIGHTER INTERCEPTOR SQUADRON
It seems that the Me 262 may have been less than ideal as a gun platform. I would have thought that hitting relatively slow moving and unmanoeuvrable bombers should have been relatively straightforward.
Many of the Me-262 pilots were also inexperienced, and flying an aircraft with performance greater than any operated before would have been a challenge to more professional aviators. Hitting Allied bombers while streaking through a formation at high speed was difficult, and if an Me-262 pilot slowed down to take more careful aim, he became a good target for the bombers' defensive fire and escorting Allied fighters.
The Messerschmitt ME 262
THE 456th FIGHTER INTERCEPTOR SQUADRON
It seems that the Me 262 may have been less than ideal as a gun platform. I would have thought that hitting relatively slow moving and unmanoeuvrable bombers should have been relatively straightforward.
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drgondog
Major
The Mcr for that airfoil in straight wing plan form with same tip/root ratio should be less than a Mustang, but it was at least 2-3% greater with two drag buckets strapped under the wing.
Quote: "Define 'minimal' gains, and 'significant' penalties - those terms in this discussion are minimally objective to debate in a significant manner."
The record-breaking Meteor F4 with 41' wing span flew at 616 mph. The Me 262 was certainly not going to do any more. It was reported to be out of control at that speed when put into a dive. So the gain would have to be defined as minimal in terms of maximum speed.
The Messerschmitt ME 262
The triangular fuselage was a dead-end experiment. Nobody has bothered to emulate it since. From the picture, it is not hard to see why.
Google Image Result for https://www.fiddlersgreen.net/aircraft/Messerschmitt-Me262/IMAGES/3-view-messerschmitt-me262.jpg
The record-breaking Meteor F4 with 41' wing span flew at 616 mph. The Me 262 was certainly not going to do any more. It was reported to be out of control at that speed when put into a dive. So the gain would have to be defined as minimal in terms of maximum speed.
...Messerschmitt also conducted a series of flight tests with the series production Me 262. In these dive tests, it was established that the Me 262 was out of control in a dive at Mach 0.86, and that higher Mach numbers would lead to a nose-down trim that could not be countered by the pilot. The resulting steeping [sic] of the dive would lead to even higher speeds and disintegration of the airframe due to excessive negative g loads...
The Messerschmitt ME 262
After the war, "Watson's Whizzers," led by Colonel Harold E. Watson from USAAF Air Technical Intelligence, shipped several intact Me 262s to the United States for further evaluation. The tests, conducted by Albert Boyd (the head of flight test for the USAAF) and a soon-to-be-legendary Chuck Yeager, determined that the performance of the Me 262 was essentially equal to the P-80A. The Me 262 had a slightly higher critical Mach number-0.83 Mach versus the handbook limit of 0.80 Mach for the P-80A--but the difference was of little value in the real world since the Me 262 could only reach that velocity in a dive, whereas the P-80A could do it in level flight. However, despite the fact that the Me 262 was almost 2,000 pounds heavier than the P-80A, the German aircraft accelerated quicker and had approximately the same climb performance.
During the tests it was found that the slightly swept wing of the Me 262 provided no useful reduction in drag, mainly because the triangular cross-section of the fuselage created so much base drag that nothing could really help much. The swept wing did not change the critical Mach number by a measurable amount, and certainly did not help performance in the low transonic region where the Me 262 was particularly unstable. The P-80A had much better handling characteristics than the Me 262, largely because it was more refined aerodynamically and had its thrust vector on the centerline of the aircraft instead of at the quarter-span of each wing.
From Me-262: Wunderplane or compromise?During the tests it was found that the slightly swept wing of the Me 262 provided no useful reduction in drag, mainly because the triangular cross-section of the fuselage created so much base drag that nothing could really help much. The swept wing did not change the critical Mach number by a measurable amount, and certainly did not help performance in the low transonic region where the Me 262 was particularly unstable. The P-80A had much better handling characteristics than the Me 262, largely because it was more refined aerodynamically and had its thrust vector on the centerline of the aircraft instead of at the quarter-span of each wing.
The triangular fuselage was a dead-end experiment. Nobody has bothered to emulate it since. From the picture, it is not hard to see why.
Google Image Result for https://www.fiddlersgreen.net/aircraft/Messerschmitt-Me262/IMAGES/3-view-messerschmitt-me262.jpg
