Allied reaction to the Me 262 swept wings

[Jenisch]

In every source I have read, the Allies are said to only have understood the benefits of the swept wing of the Me 262, after evaluted the plane after the war. However, I'm a little skeptical about this. I think Allied engineers must have paid much attention to the "strange" wings of the type in guncam footage.

Anyone can tell me something about this?

 

[FLYBOYJ]

AFAIK there were papers written about swept wings with regards to trans sonic flight prior to WW2. Swept wings before WW2 were used shift C/G. Look at the XP-55

 

[Jenisch]

Think I already heard something about this as well, Flyboy.

This being the case, together with the possibility of analyze guncam footage, only boost my idea that it wasn't necessary to evaluate a Me 262 to understand the principle of it's wings. Sounds much logical that the American and British engineers must have had a lot of discussion when first saw guncam images of the plane with swept wings.

 

[davebender]

Me-262s didn't enter combat in Gruppe strength until March 1945. That doesn't allow much time to obtain and analyze guncam footage.

 

[Jabberwocky]

Me-262s didn't enter combat in Gruppe strength until March 1945. That doesn't allow much time to obtain and analyze guncam footage.

First claimed shoot down was August 1944, so theoretically there was plenty of time to get gun cam footage.

However, there was a major lag between things going on in the combat groups and information getting to aerodynamics researchers in the ground. It was the 1940s, information transfer was much slower than we take for granted nowadays.

On swept wing research:

There were various papers on swept wings in the US and UK in the 1920s and 1930s, but, as noted above, mostly as a means of CoG management and AFAIK all of them dealt with low speed. Swept wings had appeared on quite a number of aircraft prior to WW2 and the advent of the various German swept wing aircraft during the war period.

The link between swept wings and supersonic air speed came in the mid-1930s in Germany. Adolph Busemann is credited with the idea of using swept wings for controllability of supersonic airflow, notably presenting a paper at the October 1935 Volta Congress on High Speeds in Aviation. The idea was then researched in Germany, with work shifting from theoretical to practical wind tunnel work during 1939.

German research in this area was therefore 5-6 years ahead of efforts in the US by the end of the war. In the US, Robert T Jones had come up the same ideas as Busemann at the end of 1944/beginning of 1945, a decade after Busemann presented his work publicly. Jones published papers on swept wings in May and June 1945 - just a few months before the first papers on German

There were a slew of NACA and other papers from 1946-1948 on German research into swept wings and high speed airflows. After 1946, a lot of work was done - usually in cooperation with 'paperclipped' German scientists - on combining German swept wing expertise with US/UK data on very thin airfoils.

 

[Jenisch]

However, there was a major lag between things going on in the combat groups and information getting to aerodynamics researchers in the ground. It was the 1940s, information transfer was much slower than we take for granted nowadays.

I found that hard to belive. Engineers were probably the main persons interested in the Me 262. As soon as it appear, informations about it were the highest priority.

 

[davebender]

That would have been an early model with wings swept only 18 degrees. Not sure that would make much of an impact.

 

[tyrodtom]

I think we're making a bit much of the swept wings on the Me262, they were only 18.5 degrees on all models. The early models center wings between the engines and fuselage was unswept, but later models all the wing was swept. But the 18.5 degrees was only the leading edge, the trailing edge was swept much less, more like 10 deg.
If you look at planforms of several aircraft of that era, you'll see swept leading edges, even the C-47, CW-21, T-6, etc.

 

[FLYBOYJ]

I think the German paper that addressed swept back wings and trans sonic flight gave 35 degrees as the "magic" number. In the book "Arrow of the Future" I think it's mentioned that the 262's swept back wing was done for C/G purposes and no thought was given to trans or supersonic flight.

BTW - F-86 wing sweep? 35 degrees. MiG-15? 35 degrees.

 

[oldcrowcv63]

IIRC, the big deal to western engineers about the swept wings was the German's transonic wind tunnel and flight data compiled during the war. AFAIK, allied engineers were somewhat aware of the benefits of swept wings but hadn't acquired much actual data or experience in the transonic flight regime. German test data (on models?) may have included some larger sweep angles, but I would expect transonic data on any sweep angle would be a boon to western engineers.

In general, it's my impression that the importance of the Me 262 wing sweep had been blown out of proportion. I may have missed something and as in most cases, remain open to being convinced otherwise...

 

[davparlr]

IIRC, the big deal to western engineers about the swept wings was the German's transonic wind tunnel and flight data compiled during the war. AFAIK, allied engineers were somewhat aware of the benefits of swept wings but hadn't acquired much actual data or experience in the transonic flight regime. German test data (on models?) may have included some larger sweep angles, but I would expect transonic data on any sweep angle would be a boon to western engineers.

In general, it's my impression that the importance of the Me 262 wing sweep had been blown out of proportion. I may have missed something and as in most cases, remain open to being convinced otherwise...

I agree. I think most of the response to the gun camera reviews showing the swept wing Me-263 was the recognition for what it was, a design correction for cg outage. Its performance was not any better than straight wing designs on the Allied drawing boards such as the P-80. A slightly higher mach would not have been apparent. However, when German research data was available, reactions were quick.

 

[cimmex]

I don't believe in the swept wing CG adjusting theory, it would have been much easier to move the engines front or back a little bit
regards
cimmex

 

[FLYBOYJ]

I don't believe in the swept wing CG adjusting theory, it would have been much easier to move the engines front or back a little bit
regards
cimmex

You're entitled to your opinion but it's true and was commonly done for years. This was mentioned in "Arrow for the Future" by Walter Boyne. Not only did you do this for CG requirements but you also did this as a means to put the Mean Aerodynamic Chord (MAC) and a specific point on the wing.

From Wiki...

"The first aircraft with swept wings were those designed by the British designer J.W.Dunne in the first decade of the 20th century. Dunne successfully employed severely swept wings in his tailless aircraft as a means of creating positive longitudinal static stability. Historically, many low-speed aircraft have had swept wings in order to avoid problems with their center of gravity, to move the wing spar into a more convenient location, or to improve the sideways view from the pilot's position. For instance, the Douglas DC-3 had a slight sweep to the leading edge of its wing. The wing sweep in low-speed aircraft was not intended to help with transonic performance, and although most have a small amount of wing sweep they are rarely described as swept wing aircraft. The Curtiss XP-55 was the first American swept wing airplane, although it was not considered successful. The swept wing had appeared before World War I, conceived as a means of permitting the design of safe, stable, and tailless flying wings. It imposed "self-damping" inherent stability upon the flying wing, and, as a result, many flying wing gliders and some powered aircraft appeared in the interwar years."

AND....

"Although the Me 262 is often referred to as a "swept wing" design, the production Me 262 had a leading edge sweep of only 18.5°, too slight to achieve any significant advantage in increasing the critical Mach number. Sweep was added after the initial design of the aircraft, when the engines proved to be heavier than originally expected, primarily to position the center of lift properly relative to the centre of mass. On 1 March 1940, instead of moving the wing forward on its mount, the outer wing was repositioned slightly aft; the trailing edge of the mid-section of the wing remained unswept. Based on data from the AVA Göttingen and wind tunnel results, the middle section's leading edge was later swept to the same angle as the outer panels"

From the book by Will Radinger, and Walter Schick, Me 262 and I believe the authors are from Germany...

 

[oldcrowcv63]

The great german invention of the swept wing.... (My issue is not with the Germans but with western historians) Germans were indeed pioneers in the early theoretical development of its use in transonic and supersonic flight but as well stated above, the swept wing concept and its other advantages were fairly well known before WW2 or the advent of the Me-262.

The first two aircraft shown below were developed in response to a USAAC 1939 RFD R40-C with specs defined in XC-622:

The Curtiss XP-55 Ascender (Ass-Ender), first flight: 7/19/43 leading edge sweep ~ 45° , speed ~ 400 mph (Not transonic!)
The Northrop XP-56, First flght: first flight: 9/30/43 leading edge sweep ~ 26°, trailing edge sweep: ~ 8.6°, speed ~450+mph
The Northrop XB-35, First flght (of 1/3rd scale model N-9M) : first flight: 12/27/42, full scale a/c: June 1946, leading edge sweep ~ 27°, trailing edge sweep: ~ 10.15°, speed ~400 mph

If I understand correctly the airfoils of each of these aircraft were not optimized for anything near the transonic regime...

 

[Erich]

note to Dave yes III./JG 7 was quite operational together in January 1945.

 

[Jabberwocky]

I found that hard to belive. Engineers were probably the main persons interested in the Me 262. As soon as it appear, informations about it were the highest priority.

As much as there is this perception of a mad scramble to get at German aeronautic technology in late 1944/early 1945, this really doesn't appear to be the case. On the US side, the first true specialist aeronautical technical teams didn't arrive in the ETO until April 1945. Remember, the western allies did not get into Germany proper until March.

Initial silhouettes for the Me 262 and Me 163 for fighter pilots were only available from September 1944. Accurate silhouettes were provided around December.

There was a war on. Combat units got priority.

There are no NACA/RAE/RAS technical reports on German transonic aircraft and swept wing designs until the immediate post war period, at least none that I can find. The first reference I can come up with on an engineering examination of German swept wing aircraft is a paper entitled "Reports on Selected Topics of German and Swiss Aeronautical Developments," for the Combined Intelligence Objectives Subcommittee, dated June 1945, and it mostly focuses on wind tunnel models. There are a slew of technical appraisals between July 1945 and December of the same year, ranging from appraisals of German aircraft, through to critiques of manufacturing techniques and examinations of rocketry designs.

Mostly, the US and UK appeared to be concentrating on their own technological development in these areas, such as the Miles M 52 and the various US Army and Navy supersonic programmes, until mid-1945.

 

[Siegfried]

The idea of using swept wings to delay shockwave formation and reduce supersonic drag goes to Dr Adolf Bussmann in 1933.

In 1935 Mussolini organised and sponsored a lavish aerodymanics conference in Volta Italy where every German, American, British, Italian, Swiss, Austrian etc aerodynamicist of note attended. Bussmann delivered several papers. He talked over it at Dinner. People Joked with him about it. They even drew humourous swept wing aircraft with scimitor props. Every allied aerodynamicist in attendance missed it or forgot it including Eastman Joacobs who had designed the NACA 4 and 5 digit aerfoils used in allied fighters such as the Spitifre (Mitchell actually travelled to see Jacobs before choosing the NACA 4 digit series for the Spitfire) and also developed the laminar flow wings used in the Mustang. Theodore Karman a German-Jewish immigrant who worked for Junkers in WW1 and left for the USA (15 years before Hitler, he was seeking better emplyment) and became one of the USA's foremost supersonic expert also missed it.

About 1938 Dr Alber Betz of the AVA at Goettingen (a sort of German NACA) proposed to use wing sweep to allow high speed transonic flight.

In Early 1940 Ludwig Boelkow wrote a paper showing how an aircraft with 37 degree wing sweep and NACA 22012 wings could fly at Mach 0.95 and not suffer Mach tuck.

This is significant because Boelkow designed the Me 262 (lofting its wing first thing out of uni) followed by ongoing contributions. Though the Me 262's wing sweep is attributed to a C of G changes driven by bigger engines the designers definitely knew the advantages.

1940 Willy Meesersmitt lobbies succesfully for a large scale supersonics program.

The swept wing aircraft we see used in early tailess designs carry little or no depth of understanding and would not significantly raise Mach, in fact many were dangerous.

The transonic swept wing tends to have to have profiles suited to higher speed flight anyway. It also needs to be symmetrical in camber to prevent uneven shockwave formation. It also should have minimal washout (wing twist) to also prevent shockwave formation.

The toughest technical problem is over coming spanwise flow. Due to the sweep and the interation with the fueselage the airflow tends to be along the wing in the spanwise direction. The greatly increased distance of flow means there is more distance for the boundary layer to thicken, then seperate and cause a stall at the wing tips, which being at the back move the center of lift forward and cause a pitch up and further deep stall.

German research deeply investigated these phenomena and came up with several solutions
1 Slats
2 Wing fences
3 Forward Sweep (eg Ju 287 jet test bed)
4 Crescent wing (ie reducing sweep at wing tips to let spanwise flow fall of to be used on the Ar 234 crescent wing)

5 To cope with the flutter issues that were eventuating Junkers developed for the Ju 287 a way of cantilevering the engines on pods to act like pendulums that lower the resonant frequency and to counterbalance wing. Hence the pods on the B-47

Salvaged Me 262 slat hardware was in fact used in the first 7 F-86 Sabre.

Note the premature tip stall of the Curtiss XP-55 Ascender (Assender) was never solved.

Bussman came to the US under paperclip. While lecturing and explaing how showaves formed in 3d and should be viewed as pipes Richard Whitcomb had an epiphany that led to the the formulation of the Whitecombe Area Rule. While everyone else laughed Bussmann actively defended him. The Germans has in fact been well aware of this effect, Whitcomb merely defined it eloquently.

 

[FLYBOYJ]

Salvaged Me 262 slat hardware was in fact used in the first 7 F-86 Sabre.

Good information but are you saying that the first 7 F-86s used 262 hardware or 262 hardware was "fitted" as in test fitted to the "6-3" wing?

 

[Siegfried]

Good information but are you saying that the first 7 F-86s used 262 hardware or 262 hardware was "fitted" to the "6-3" wing?

Actual Me 262 slat mechanism taken from salvaged Me 262.

http://sabre-pilots.org/classics/v53sabre.htm
"Slowly but surely, North American's engineers brought the design to its final shape. But the slat design remained a problem. Finally, an entire Me-262 wing was flown in from Wright Field. North American's engineers disassembled the slats and modified the slat track mechanism to fit the XP-86 wing, using the Me-262 slat lock and control switch. Although not perfect, it was a start and the slat worked. In fact, the first seven aircraft used Me-262 slat locks and tracks. "

Its fairly obvious I think that by the time they got the the Me 262 Messerschmitt were pretty good at the difficult art of slat mechanism design. Thye NA engineers just took what they saw would work. I think most F-86 had slats but some eventually received droop snoot leading edge flaps.

The F-86 actually used US style laminar flow profiles, which has excellent transonic propeties anyway combined with swept wings. The combination was very effective.

The effectiveness of wing sweep was quickly accepted by US aerodynamcists because R.T.Jones, an American had started writing papers on the issue in 1944. He had put a few 1.5 inch deltas in a supersonic wind tunnel. George Schaier (B-29 and B-24 wing designer, was certainly up on it).

The Germans had more or less come up with many indepth solutions to the spanwise flow issue which were of much greater value than the fairly trivial knowledge of how swept wings delay shock. Theodore von Karman, who headed NACA researcg at the time, estimated it at 2 years.

However the Germans were well ahead on the spanwise flow control issue. Nose flaps was another thing they developed as well as Kruger Flaps (inadvertantly named after Kuruger, the assistant of Ar 234 designer Rudiger Kosin)

 

[FLYBOYJ]

Actual Me 262 slat mechanism taken from salvaged Me 262.

http://sabre-pilots.org/classics/v53sabre.htm
"Slowly but surely, North American's engineers brought the design to its final shape. But the slat design remained a problem. Finally, an entire Me-262 wing was flown in from Wright Field. North American's engineers disassembled the slats and modified the slat track mechanism to fit the XP-86 wing, using the Me-262 slat lock and control switch. Although not perfect, it was a start and the slat worked. In fact, the first seven aircraft used Me-262 slat locks and tracks. "

Its fairly obvious I think that by the time they got the the Me 262 Messerschmitt were pretty good at the difficult art of slat mechanism design. Thye NA engineers just took what they saw would work. I think most F-86 had slats but some eventually received droop snoot leading edge flaps.

Again great info but I have problems believing that 7 prototype aircraft had "used" 262 parts on them. Perhaps remanufactured parts reversed engineered from the original hardware. I know this was still in the post war period but if this was actually done it was beyond risk, it crossed the line into stupidity.

BTW, excellent site!