Which jet was better, the Me 262 or the Gloster Meteor?

[drgondog]

Extrapolated further, if Mcr for the Me-262 was only .8M in a dive, it was within the envelope of a pursuing Mustang - and that would not be 'insignificant'.

The Spitfire was said to have had an Mcr of 0.89, the Tempest 0.83, the Mustang 0.8, the Meteor 0.83 and the Schwalbe 0.86. Any advantage to the Schwalbe over the Meteor would be at least partly due to the higher aspect ratio of the wing, surely. And that advantage is bought at the expense of lower wing second moment of area and hence structural strength, a tradeoff which only makes sense for a specialist interceptor.

Regards,

Magnon

The Spit Mcr probably was lower than .89 as the speed it attained during the documented dive trials was well into Mcr. The max speed recorded for a Mustang dive (that returned intact) was .84-.85 and there were visible signs of structural damage. I don't know about the Tempest. My comment above was to illustrate that a couple of percentage points delay in Mcr would be significant - not that the 262 was limited (ultimate limit) to .8

As to 'advantages' one way or the other, one needs a full set of data to make valid statements regarding structural integrity, static margin limits, total Cg travel, trim drag at extreme AoA, etc.

When you pose that 'any advantage to the Schwalbe over the Meteor would be partly due to the AR of the wing, surely" - what are you thinking about specifically?

AR would have an effect on Induced drag, but by itself leaves much to be discovered relative to structural considerations. The wing design on the 262 would be influenced by three primary factors - L/D obviously, Structural integrity, and low speed stability. The leading edge slats would have been added to improve manueverability at high AoA as well as add to the low speed handling characteristics. I am not overlooking fuel capacity or the aero interference drag brough about by the nacelles but those would have been in the trade offs while trying to maximize the mission specs.

The sweep, as noted in the historical accounts was designed to move the aerodynamic center at the MAC aft to improve the stability throughout the cg range. It should have, despite repeated opinions, also influenced the drag rise favorably by a couple of percentage points, particularly with later models that sewpt from the root to the tip, rather that straight leading edge from root to engine.

The planform taper/tip would be further refinement to minimize induced drag for that airfoil and also structural considerations

Far more importantly is the root chord geometry and the taper to the wing tip. The depth of the spar at the root and the main beam/torque box geometry will have much to say about both stresses due to the lift distribution effect on bending loads and the tosion applied by aerodynamic loads and vortex which must be distributed spanwise to the root.

Mc/I is of course a classic equation for stress on a homogeneous body due to a bending load - but in airframe design back in those days a 'normal' spar design was top and lower caps (usually extrusions), augmented by wing skin to take out the axial loads resulting from bending and a shear panel to transfer the axial loads from one cap to the other...what did you have in mind with the 'lower wing second moment of area and hence lower strength"??

I can get all the 'strength' one needs to take out bending in say a 9% t/c by either lengthening the chord (Spitfire approach) to deepen the spar (local 'thickness') for a beam cap/shear panel design of certain area and web shear panel thickness, or maintain 9% with shorter chord (Me 262) by a variety of ways but all would increase wing weight. (i.e. increase cap area, same cap area/thicker surface skin)

 

[drgondog]

The snaking - it wasn't specified as just occurring at high speed - was raised by Wendell apparently for an early condition where the aircraft had only two main tanks and an auxilliary tank. (For a total capacity of 529 US gallon).

I don't recall the USAAF report at Wright Pat discussion yaw/dutch roll for any condition except high speed and/or manuever with aft fuel in fuselage. I'll be able to comment more when I unpack my books.

The Me 262 Pilots Handbook indicates that a further 158 gallon rear auxilliary tank had been added and the rear main tank slightly reduced in capacity (total capacity 655 US gallon). One would have to assume that the CG problem had been exacerbated. The last page of the Handbook also indicates that there was going to be provision for two jettisonable tanks of 158 gallon. One would surmise that these would be wing tanks, which would raise the mass moment of inertia of the aircraft again and probably compound the snaking problem.

Negative effect to stability due to external tank Depends on multiple factors and speed/loading envelope

Wendell states that the aircraft would automatically stall in a turn if the CG was too far aft.

MANY aircraft display this nasy habit for aft cg. Actually a mere stall instead of a coupled stall/snap roll is to be desired.

The CFE report on the Meteor states that the CG remained within its design envelope at all times. Your feedback on the Me 262 would be appreciated, especially if you have access to other sources (e.g Wright Pat?). It seems to me to be an intriguing and critical aspect of the aspect of the viability of the aircraft as a dogfighting machine.

This is advantage but not necessarily the winning advantage. Also - the issue may often be mitigated by process - like use fuse fuel before mains.

It would seem to me to be extremely naive to expect that in all cases of air combat you could have consumed enough fuel to keep the CG within its design envelope, particularly as Allied aircraft were lurking around the German airfields.

True - if Fw 190s were attacking Mustang bases all the time, they would have an advantage against a Mustang with full aft tank in most ACM at low level. OTOH fuel was such a shortage that Me 262s didn't have full tanks at all times anyway.

For viable gunnery, not only does the aircraft have to be controllable, but the gun should not be liable to jamming during high-G manoeuvres. The Schwalbe cannon was notorious in this regard. It would seem that the strategy was going to have to always be hit-and-run tactics at high speed. That's very narrow and suited only to a specialist interceptor. But that's exactly what the Shwalbe was designed for.

Regards,

Magnon

Many Allied fighters were very succesful engaging much more manuevrable Axis fighters, particularly Japan, with the primary advantage of just much greater speed. The smart 262 pilot kept his speed up and decided whether to fly away and come back or simply continue on. A P-38 or a Mustang (or F4U or F6F) against a George had best keep the same advice at hand and turn only a limited degree for a brief deflection on such aircraft already pulling high G's.

 

[Magnon]

Many Allied fighters were very succesful engaging much more manuevrable Axis fighters, particularly Japan, with the primary advantage of just much greater speed. The smart 262 pilot kept his speed up and decided whether to fly away and come back or simply continue on. A P-38 or a Mustang (or F4U or F6F) against a George had best keep the same advice at hand and turn only a limited degree for a brief deflection on such aircraft already pulling high G's.

That's what I have been saying all along...

 

[Magnon]

Magnon: "It would seem to me to be extremely naive to expect that in all cases of air combat you could have consumed enough fuel to keep the CG within its design envelope, particularly as Allied aircraft were lurking around the German airfields."

Drgndog: "True - if Fw 190s were attacking Mustang bases all the time, they would have an advantage against a Mustang with full aft tank in most ACM at low level. OTOH fuel was such a shortage that Me 262s didn't have full tanks at all times anyway."​

If you can't fill your fuel tanks, you can't carry out very meaningful operations. Taking this to it's ultimate conclusion, the whole problem could be fixed by having no fuel at all. Maybe this was why 1432 were built, most sitting on the ground and only around 300 were ever used in combat. (Sorry, I'm just being facetious here.)

The evidence that fuel storage was critical is the fact that they started with three fuel tanks, added another auxilliary tank and according to the Me262 Handbook, were looking to add two extra drop tanks. Were the Germans perhaps looking to base the aircraft remotely from Allied attack, hence the need for the extra range?

Regards,

Magnon

 

[Magnon]

I have attached some data for critical temperatures in the JUMO engine which indicate why it was very prone to damage when overheated on opening the throttle too quickly.

The BMW temperature profile was as close as I could get to the JUMO. It had the same problem, in any case.

Regards,

Magnon

 

[drgondog]

If you can't fill your fuel tanks, you can't carry out very meaningful operations. Taking this to it's ultimate conclusion, the whole problem could be fixed by having no fuel at all. Maybe this was why 1432 were built, most sitting on the ground and only around 300 were ever used in combat. (Sorry, I'm just being facetious here.)

The evidence that fuel storage was critical is the fact that they started with three fuel tanks, added another auxilliary tank and according to the Me262 Handbook, were looking to add two extra drop tanks. Were the Germans perhaps looking to base the aircraft remotely from Allied attack, hence the need for the extra range?

Regards,

Magnon

Yes - most Me 262 bases were roughly east of a line from munich through Leipzig and Berlin in the last couple of months of the war. The 8th AF specifically attacked airfields like Leipheim and Landsburg, etc to go after 262s.

Like the Mustang the Me 262 mission flexibility was greater with additional fuel, but far from useless with the internal fuel capability (and mostly Not fully tanked up simply because of shortages of fuel). Having said this the Me 262 fuel situration per se was probably better than recips which required refined gasoline rather than Diesel/Kerosene at that time of the war.

 

[Magnon]

When you pose that 'any advantage to the Schwalbe over the Meteor would be partly due to the AR of the wing, surely" - what are you thinking about specifically?

AR would have an effect on Induced drag, but by itself leaves much to be discovered relative to structural considerations. The wing design on the 262 would be influenced by three primary factors - L/D obviously, Structural integrity, and low speed stability. The leading edge slats would have been added to improve manueverability at high AoA as well as add to the low speed handling characteristics. I am not overlooking fuel capacity or the aero interference drag brough about by the nacelles but those would have been in the trade offs while trying to maximize the mission specs.

The sweep, as noted in the historical accounts was designed to move the aerodynamic center at the MAC aft to improve the stability throughout the cg range. It should have, despite repeated opinions, also influenced the drag rise favorably by a couple of percentage points, particularly with later models that sewpt from the root to the tip, rather that straight leading edge from root to engine.

The planform taper/tip would be further refinement to minimize induced drag for that airfoil and also structural considerations

Far more importantly is the root chord geometry and the taper to the wing tip. The depth of the spar at the root and the main beam/torque box geometry will have much to say about both stresses due to the lift distribution effect on bending loads and the tosion applied by aerodynamic loads and vortex which must be distributed spanwise to the root.

Mc/I is of course a classic equation for stress on a homogeneous body due to a bending load - but in airframe design back in those days a 'normal' spar design was top and lower caps (usually extrusions), augmented by wing skin to take out the axial loads resulting from bending and a shear panel to transfer the axial loads from one cap to the other...what did you have in mind with the 'lower wing second moment of area and hence lower strength"??

I can get all the 'strength' one needs to take out bending in say a 9% t/c by either lengthening the chord (Spitfire approach) to deepen the spar (local 'thickness') for a beam cap/shear panel design of certain area and web shear panel thickness, or maintain 9% with shorter chord (Me 262) by a variety of ways but all would increase wing weight. (i.e. increase cap area, same cap area/thicker surface skin)

I was thinking along the lines of what was expressed by A.C Kermode in "Mechanics of Flight - Introduction to Aeronautical Engineering." I don't have anything like your background in this area. Here he was talking about the benefits of aspect ratio in terms of reducing induced drag:

"the best we can do in practical design is to make the aspect ratio as large as possible. Unfortunately a limit is soon reached - from the structural point of view. The greater the span, the greater must be the wing strength, the heavier must be the structure, and so eventually the greater weight of the structure more than counterbalances the advantages gained. Again it is a matter of compromise...​

If I were designing a specialist interceptor, I would compromise towards the low end of manoeuvrability, hence G-forces and hence structural strength.

The Meteor was accepted as having a rugged airframe, and this was proven in around 25 years in Argentinean and Brazilian service. The F 8 airframe was proven to be able to survive quite heavy damage from 37 mm MiG cannon in Korea:

"...Although a strictly subsonic aircraft, the Meteor did have a high performance for a straight-wing fighter; it was rugged, versatile, and capable of being adapted to various missions..."​

The Evolution Of Modern Aircraft NASA

The Meteor had a much more robust wing as per -

Meteor; Wing aspect ratio; 4.94
Me 262; Wing aspect ratio; 7.32
Meteor; Wing Thickness; 12% root; 10.4% tip
Me 262; Wing Thickness; 11% root; 9% tip
Meteor F3; Wingspan; 13.1 m
Me 262; Wingspan; 12.53 m​

Note that the wing drag of the Meteor was higher, but because the nacelles were integrated with the wing, the Meteor nacelle drag was less than the Me 262 (see attachment), despite the centrifugal compressor forcing a larger engine diameter.

I'd be interested to know how you would interpret the "miscellaneous" item?

Regards,

Magnon

 

[drgondog]

I was thinking along the lines of what was expressed by A.C Kermode in "Mechanics of Flight - Introduction to Aeronautical Engineering." I don't have anything like your background in this area. Here he was talking about the benefits of aspect ratio in terms of reducing induced drag:

Remember Induced Drag is but one component of drag - and it dominates at low speed with high angles of attack when compared with vortex and parasite drag. At high speeds the drag due to compressibility and parasite drag dominates and induced drag is low by comparison.

"the best we can do in practical design is to make the aspect ratio as large as possible. Unfortunately a limit is soon reached - from the structural point of view. The greater the span, the greater must be the wing strength, the heavier must be the structure, and so eventually the greater weight of the structure more than counterbalances the advantages gained. Again it is a matter of compromise...​

True - for same root chord to tip chord geometry - refer back to my conversation a couple of posts back

If I were designing a specialist interceptor, I would compromise towards the low end of manoeuvrability, hence G-forces and hence structural strength.

The Meteor was accepted as having a rugged airframe, and this was proven in around 25 years in Argentinean and Brazilian service. The F 8 airframe was proven to be able to survive quite heavy damage from 37 mm MiG cannon in Korea:

"...Although a strictly subsonic aircraft, the Meteor did have a high performance for a straight-wing fighter; it was rugged, versatile, and capable of being adapted to various missions..."​

The post WWII Meteor also experienced growth in capability due to enhanced design features.

The Evolution Of Modern Aircraft NASA

This is a nice table for comparison - but you have noted that the drag presented is for extremely low speed range Reynolds number where induced drag dominates? It would be nice to see the table at higher speeds near Vmax. Visualize Induced Drag as a second degree curve with highest value where the wing first experiences lift and Cl is close to Clmax, then asymptotically approaches its lowest value at top speed where the AoA and Cl is lowest - then place the parasite drag and all its components at a very low level where Clmax is highest and growing as a function of V>>2 - reaching its highest value at highests speed. In the case of these fighters they all were in compressibility range > .55 M and compressibility drag would be added to parasite drag in this range for those airfoils. Not going to discuss the vortex drag component in context of the tables.

Visualize the plot resembling a 'bucket' - hence the terp Drag Polar or Drag Bucket

The Meteor had a much more robust wing as per -

Meteor; Wing aspect ratio; 4.94
Me 262; Wing aspect ratio; 7.32
Meteor; Wing Thickness; 12% root; 10.4% tip
Me 262; Wing Thickness; 11% root; 9% tip
Meteor F3; Wingspan; 13.1 m
Me 262; Wingspan; 12.53 m​

Note that the wing drag of the Meteor was higher, but because the nacelles were integrated with the wing, the Meteor nacelle drag was less than the Me 262 (see attachment), despite the centrifugal compressor forcing a larger engine diameter.

I'd be interested to know how you would interpret the "miscellaneous" item?


Regards,

Magnon

What micellaneous item? From inspection of data above it is clear that the mean chord for the Meteor is quite a bit longer than the 262 (i.e greater wing span but lower Aspect ratio). This data also implies a thicker (Deeper) airfoil than the wing thickness % imply. This further implies the wing drag of the Meteor is higher (independent of induced drag).

 

[Magnon]

What micellaneous item? From inspection of data above it is clear that the mean chord for the Meteor is quite a bit longer than the 262 (i.e greater wing span but lower Aspect ratio). This data also implies a thicker (Deeper) airfoil than the wing thickness % imply. This further implies the wing drag of the Meteor is higher (independent of induced drag).

The miscellaneous item at the bottom of the table was noted as including interference etc. It gave a figure of 3 lb for the Meteor and 8 lb for the Me 262.

 

[Magnon]

What micellaneous item? From inspection of data above it is clear that the mean chord for the Meteor is quite a bit longer than the 262 (i.e greater wing span but lower Aspect ratio). This data also implies a thicker (Deeper) airfoil than the wing thickness % imply. This further implies the wing drag of the Meteor is higher (independent of induced drag).

That's arguably an understatement... The wing area of the Me 262 was less than two thirds that of the Meteor. The wing spans were similar. That makes the mean chord of the Me 262 wing around two thirds that of the Meteor. With the average ~10% higher t/c ratio of the Meteor wing, the resulting average wing thickness is also less than two thirds that of the Meteor. As the second moment of area is a function of Ay^2, I would have thought that that leaves a lot to make make up in terms of thickening of wing members and skin. Of course this would be important not only for bending, but also torsion, particularly if as you say they were intending to install wing drop tanks.

DragonDog: Mc/I is of course a classic equation for stress on a homogeneous body due to a bending load - but in airframe design back in those days a 'normal' spar design was top and lower caps (usually extrusions), augmented by wing skin to take out the axial loads resulting from bending and a shear panel to transfer the axial loads from one cap to the other...what did you have in mind with the 'lower wing second moment of area and hence lower strength"??​

The Republic Thunderjet had these sorts of problems in the early fifties:
Extract from Wikipedia

"The structural improvements were factory-implemented in the F-84D, which entered service in 1949. Wings were covered with thicker aluminum skin, the fuel system was winterized and capable of using JP-4 fuel, and a more powerful J35-A-17 engine with 5,000 lbf (22.2 kN) was fitted. It was discovered that the untested wingtip fuel tanks contributed to wing structural failures by inducing excessive twisting during high-g maneuvers. To correct this, small triangular fins were added to the outside of the tanks. The F-84D was phased out of USAF service in 1952 and left Air National Guard service in 1957."​

"The first effective and fully-capable Thunderjet was the F-84E model which entered service in 1949. The aircraft featured the J35-A-17 engine, further wing reinforcement, a 12 in (305 mm) fuselage extension in front of the wings and 3 in (76 mm) extension aft of the wings to enlarge the cockpit and the avionics bay, an A-1C gunsight with APG-30 radar, and provision for an additional pair of 230 gal (870 L) fuel tanks to be carried on underwing pylons."​

By the way, Republic converted the F 84 from straight wing to 38.5 degree swept wing and reportedly found little benefit:

Air, Land and Sea: 2008-08-10
Design and development
In 1949, Republic created a swept wing version of the F-84 hoping to bring performance to the F-86 level. The last production F-84E was fitted with a swept tail, a new wing with 38.5 degrees of leading edge sweep and 3.5 degrees of anhedral, and a J35-A-25 engine producing 5,300 pound-force (23.58 kN) of thrust. The aircraft was designated XF-96A. It flew on 3 June 1950 with Otto P. Haas at the controls. Although the airplane was capable of 602 knots (693 mph, 1,115 km/h), the performance gain over the F-84E was considered minor. Nonetheless, it was ordered into production in July 1950 as the F-84F Thunderstreak. The F-84 designation was retained because the fighter was expected to be a low-cost improvement of the straight-wing Thunderjet with over 55 percent commonality in tooling.

In the meantime, the USAF, hoping for improved high-altitude performance from a more powerful engine, arranged for the British Armstrong Siddeley Sapphire turbojet engine to be built in the United States as the Wright J65. To accommodate the larger engine, YF-84Fs with a British-built Sapphire as well as production F-84Fs with the J65 had a vertically stretched fuselage, with the air intake attaining an oval cross-section. Production delays with the F-84F forced USAF to order a number of straight-wing F-84Gs as an interim measure.​

The Thunderjet wing had a relatively moderate aspect ratio at around 5:1. Your feedback would be appreciated.

In terms of drag, the Meteor could well afford to trade off increased wing drag in return for improved ruggedness and manoeuvrability due to the possession of more powerful and efficient engines (20% lower specific fuel consumption).

By the way, I would still like to see your feedback on the hot end temperature analysis re the JUMO and the Derwent.

 

[riacrato]

Who said the drop tanks were to be installed under the wings anyways. AFAIK they were installed underneath the fuselage where the A-2 had the bomb racks. See also Me 262 B-1a:

 

[drgondog]

That's arguably an understatement... The wing area of the Me 262 was less than two thirds that of the Meteor. The wing spans were similar. That makes the mean chord of the Me 262 wing around two thirds that of the Meteor. With the average ~10% higher t/c ratio of the Meteor wing, the resulting average wing thickness is also less than two thirds that of the Meteor. As the second moment of area is a function of Ay^2, I would have thought that that leaves a lot to make make up in terms of thickening of wing members and skin. Of course this would be important not only for bending, but also torsion, particularly if as you say they were intending to install wing drop tanks.

I am still curious regarding your application of 'second moment of inertia'? to any extrapolated comparison between the two ships. I would have to have the actual cross sections from the wing tip to the root chord as well as the aero load distribution and twist to begin to start on any structural/stress analysis.

Torsional effects were more pronounced for swept wing configurations as well as spanwise flow complications - the MiG 15 had quite a bit of trouble until they installed wing fences - as an example -

DragonDog: Mc/I is of course a classic equation for stress on a homogeneous body due to a bending load - but in airframe design back in those days a 'normal' spar design was top and lower caps (usually extrusions), augmented by wing skin to take out the axial loads resulting from bending and a shear panel to transfer the axial loads from one cap to the other...what did you have in mind with the 'lower wing second moment of area and hence lower strength"??​

The Republic Thunderjet had these sorts of problems in the early fifties:
Extract from Wikipedia

"The structural improvements were factory-implemented in the F-84D, which entered service in 1949. Wings were covered with thicker aluminum skin, the fuel system was winterized and capable of using JP-4 fuel, and a more powerful J35-A-17 engine with 5,000 lbf (22.2 kN) was fitted. It was discovered that the untested wingtip fuel tanks contributed to wing structural failures by inducing excessive twisting during high-g maneuvers. To correct this, small triangular fins were added to the outside of the tanks. The F-84D was phased out of USAF service in 1952 and left Air National Guard service in 1957."​

"The first effective and fully-capable Thunderjet was the F-84E model which entered service in 1949. The aircraft featured the J35-A-17 engine, further wing reinforcement, a 12 in (305 mm) fuselage extension in front of the wings and 3 in (76 mm) extension aft of the wings to enlarge the cockpit and the avionics bay, an A-1C gunsight with APG-30 radar, and provision for an additional pair of 230 gal (870 L) fuel tanks to be carried on underwing pylons."​

By the way, Republic converted the F 84 from straight wing to 38.5 degree swept wing and reportedly found little benefit:

Air, Land and Sea: 2008-08-10
Design and development
In 1949, Republic created a swept wing version of the F-84 hoping to bring performance to the F-86 level. The last production F-84E was fitted with a swept tail, a new wing with 38.5 degrees of leading edge sweep and 3.5 degrees of anhedral, and a J35-A-25 engine producing 5,300 pound-force (23.58 kN) of thrust. The aircraft was designated XF-96A. It flew on 3 June 1950 with Otto P. Haas at the controls. Although the airplane was capable of 602 knots (693 mph, 1,115 km/h), the performance gain over the F-84E was considered minor. Nonetheless, it was ordered into production in July 1950 as the F-84F Thunderstreak. The F-84 designation was retained because the fighter was expected to be a low-cost improvement of the straight-wing Thunderjet with over 55 percent commonality in tooling.

In the meantime, the USAF, hoping for improved high-altitude performance from a more powerful engine, arranged for the British Armstrong Siddeley Sapphire turbojet engine to be built in the United States as the Wright J65. To accommodate the larger engine, YF-84Fs with a British-built Sapphire as well as production F-84Fs with the J65 had a vertically stretched fuselage, with the air intake attaining an oval cross-section. Production delays with the F-84F forced USAF to order a number of straight-wing F-84Gs as an interim measure.​

I am not sure where you are going with this. Republic was (and is) famous for building aircraft which invariably utilized all available runway - all the time. The nickname for the F84F was 'Gravel Gobbler' and the F-105 was the 'Thud'. The difference between the two aircraft other than sheer size was that the 105 pilots favorite comment to F-15 and F-16 pilots on the deck chasing them was 'Check your 12" - meaning they couldn't be caught from behind at low altitude. The current rugged beast is the A-10, an absolute marvel for CAS but barely faster than a Mustang and slower than the Me 262.

As to torsion - as torque box is always a more complicated design than a wing spar and actually more esoteric when looking at asymetric load transfer from tail to fuselage - but nevertheless far more complex relative to a homogeneous spar or beam.

The Thunderjet wing had a relatively moderate aspect ratio at around 5:1. Your feedback would be appreciated.

the lower the aspect ratio, the lower the profile drag for the wing and also less complexity in designing for wing torque in swept wing aircarft. Virtually all high performance aircraft with a design balance between speed and manueverability (for last 30 years) will have an AR somewhere between 2 and "3 something"



In terms of drag, the Meteor could well afford to trade off increased wing drag in return for improved ruggedness and manoeuvrability due to the possession of more powerful and efficient engines (20% lower specific fuel consumption).

Not if combat with a significantly faster opponent is a desired mission. Visualize a MiG 15 vs F84 or Banshee?

By the way, I would still like to see your feedback on the hot end temperature analysis re the JUMO and the Derwent.

Thermodynamic efficiency is enhanced with greater delta between intake and exhaust temps - the rest is trade offs and compromises based on metallurgy..

As to the question regarding 'miscellaneous' in which you were pointing to the interference drag comparisons? Interference drag is a complicated 'catch all' which collects viscous components of drag related to lift. That would include pressure drag associated with changes in angle of attack such as fuselage vortex drag, nacelle and nacelle/pylon interference drag, changes in trim drag and 'simply' changes in drag due to engine power effects (inlet or exhaust).

As the tables a.) do not elucidate further, and b.) there is not a corresponding Reynolds number presentation for 800 feet per second (it is not linear), I have no basis for comment

 

[Magnon]

Thermodynamic efficiency is enhanced with greater delta between intake and exhaust temps - the rest is trade offs and compromises based on metallurgy...

I will take that as - "As an airframe specialist, I don't give a stuff about powerplants."

It seems to me that that's the sort of thinking that led to all the problems with the Schwalbe. "Design the airframe first and then the rest can just be improvised along the way."

I have attached a copy of bench testing on the JUMO over a period of 7.5 hours. It is generally accepted that three hours on a test banch were equivalent to around one in combat. (That's assuming the engine wasn't "cooked" in a panic opening of the throttle or due to a surge event in combat).

From the graph, I'd estimate a 2.5% drop in thrust and 4.5% increase in specific fuel consumption. It would be reasonable to surmise that over the usual ten hour JUMO engine life in combat, a very much more dramatic drop in performance of the aircraft would result.

The other thing I'd like some feedback on, one way or the other, is the analysis on on post #34 on http://warbirdsforum.com/showthread.php?t=451&page=4

The bottom line here was:

Summarizing, the speed margin of the 262 versus the wartime Meteor III equipped with the 2000lb S/T engines would be
Sea level 4mph (0.82%)
5K 12mph (2.45%)
10K 20mph (4.04%)
15K 24mph (4.81%)
20K 34mph (6.83%)
25K 38mph (7.72%)
30K 24mph (4.94%)

Two factors limited the Meteor III's speed, i.e. a structural limit of 500mph and a critical mach of 0.74, whichever was met first.​

Regards,

Magnon

 

[drgondog]

I will take that as - "As an airframe specialist, I don't give a stuff about powerplants."

Somewhat true - engine design is a deep and complex discipline. I took two propulsion curses and discuss aspects of the theory (after 45 years) but never designed an engine per se. Have been involved in inlets however but even those were all either very low speed helicopter or very high speed multi mach supersonic.

It seems to me that that's the sort of thinking that led to all the problems with the Schwalbe. "Design the airframe first and then the rest can just be improvised along the way."

I would say that you are incorrect. Airframe, avionics, armament, powerplant, landing gear teams work closely throughout a design process - before preliminary design is complete - all the way through the design cycle. I have no experience with Messerschmist but I feel confident they did Not take that attitude.

I have attached a copy of bench testing on the JUMO over a period of 7.5 hours. It is generally accepted that three hours on a test banch were equivalent to around one in combat. (That's assuming the engine wasn't "cooked" in a panic opening of the throttle or due to a surge event in combat).

With respect to the Jumo - what is speculation versus fact vs generally accepted?

From the graph, I'd estimate a 2.5% drop in thrust and 4.5% increase in specific fuel consumption. It would be reasonable to surmise that over the usual ten hour JUMO engine life in combat, a very much more dramatic drop in performance of the aircraft would result.

You make a lot of assumptions, some based on speculation some on fact. In which category do the above fall? When engines decrease performance significantly - there is an engine change and the sub par engine is either overhauled or scrapped so as to not accept 'sub par performance'

The other thing I'd like some feedback on, one way or the other, is the analysis on on post #34 on http://warbirdsforum.com/showthread.php?t=451&page=4

The bottom line here was:

Summarizing, the speed margin of the 262 versus the wartime Meteor III equipped with the 2000lb S/T engines would be
Sea level 4mph (0.82%)
5K 12mph (2.45%)
10K 20mph (4.04%)
15K 24mph (4.81%)
20K 34mph (6.83%)
25K 38mph (7.72%)
30K 24mph (4.94%)

Two factors limited the Meteor III's speed, i.e. a structural limit of 500mph and a critical mach of 0.74, whichever was met first.​

Regards,

Magnon

Comment with respect to what specifically?

Dynamic Pressure loads (1/2 rho V>>2) at the upper limit of the aircraft's capability often resulted in structural failure, say, during manuever and asymmetic force input. Yaw in a dive or a roll or sideslip would be flight conditions difficult to analyze in preliminary design. Even more difficult would be the prediction of onset of flutter and aeroelastic loads at such thresholds... a high frequency reversible load under such conditions would be extremely dangerous.

Neither design team was particularly knowledgable about increase in interference drag due to compressibility and were perhaps just past being 'vaguely aware' of the shock wave phoenomena moving the center of aerodynamic pressure aft or the pressure gradient change in the transonic ranges. These variables contributed to a.) increased flow separation and immersion of flight controls aft in highly turbulent flow, b.) pitch trim changes due to cahnges in CMac contributing to pitch down forces beyong human strength to overcome, and c.) increased dynamic pressure loads beyond predicted levels from early analysis.

I am not able to comment on the nacelle design for either a/c other than the 'miscellaneous' drag in the table you showed - at 100 feet per second - which should Not extrapolate to any form of compressibility effects at .74 (or above) at the inlet of the meteor..

 

[Magnon]

Originally Posted by Magnon
I was thinking along the lines of what was expressed by A.C Kermode in "Mechanics of Flight - Introduction to Aeronautical Engineering." I don't have anything like your background in this area. Here he was talking about the benefits of aspect ratio in terms of reducing induced drag:

Remember Induced Drag is but one component of drag - and it dominates at low speed with high angles of attack when compared with vortex and parasite drag. At high speeds the drag due to compressibility and parasite drag dominates and induced drag is low by comparison.

"the best we can do in practical design is to make the aspect ratio as large as possible. Unfortunately a limit is soon reached - from the structural point of view. The greater the span, the greater must be the wing strength, the heavier must be the structure, and so eventually the greater weight of the structure more than counterbalances the advantages gained. Again it is a matter of compromise...
True - for same root chord to tip chord geometry - refer back to my conversation a couple of posts back

If I were designing a specialist interceptor, I would compromise towards the low end of manoeuvrability, hence G-forces and hence structural strength.

The Meteor was accepted as having a rugged airframe, and this was proven in around 25 years in Argentinean and Brazilian service. The F 8 airframe was proven to be able to survive quite heavy damage from 37 mm MiG cannon in Korea:
"...Although a strictly subsonic aircraft, the Meteor did have a high performance for a straight-wing fighter; it was rugged, versatile, and capable of being adapted to various missions..."
The post WWII Meteor also experienced growth in capability due to enhanced design features.​

With regard to the Sabre, which was designed in light of knowledge of the German swept-wing research and inspection of captured ME 262s:

...In August of 1945, project aerodynamicist L. P. Greene proposed to Raymond Rice that a swept-wing configuration for the P-86 be adopted. Wind tunnel tests carried out in September of 1945 confirmed the reduction in drag at high subsonic speeds as well as the beneficial effect of the slats on low speed stability. The limiting Mach number was raised to 0.875.
Based on these wind-tunnel studies, a new design for a swept-wing P-86 was submitted to the USAAF in the fall of 1945. The USAAF was impressed, and on November 1, 1945 it readily approved the proposal. This was one of the most important decisions ever made by the USAAF--had they not agreed to this change, the history of the next forty years would undoubtedly have been quite different.

North American's next step was to choose the aspect ratio of the swept wing. A larger aspect ratio would give better range, a narrower one better stability, and the correct choice would obviously have to be a tradeoff between the two. Further tests carried out between late October and mid November indicated that a wing aspect ratio of 6 would be satisfactory, and such an aspect ratio had been planned for in the proposal accepted on November 1. However, early in 1946 additional wind tunnel tests indicated that stability with such a narrow wing would be too great a problem, and in March the design reverted to a shorter wingform. An aspect ratio of 4.79, a sweep-back of 35 degrees, and a thickness/chord ratio of 11% at the root and 10% at the tip was finally chosen... ​

North American XP-86 Sabre

This seems to me to confirm what I believe we have agreed, that the Schwalbe wing design was optimised for a relatively narrow high speed interceptor role.

At this point, DragonDog, I'd like to pay tribute to your patience in explaining esoteric aerodynamic theory to complete amateurs such as myself. I think that with open-minded research it is possible to winkle out some truth with regard to this subject, which is all too often clouded in myth. Keep up the good work!

Regards,

Magnon

 

[Magnon]

Who said the drop tanks were to be installed under the wings anyways. AFAIK they were installed underneath the fuselage where the A-2 had the bomb racks. See also Me 262 B-1a:

Thanks for that information Riacrato.

 

[Magnon]

I will take that as - "As an airframe specialist, I don't give a stuff about powerplants."

DragonDog quote:

"Somewhat true - engine design is a deep and complex discipline. I took two propulsion curses and discuss aspects of the theory (after 45 years) but never designed an engine per se. Have been involved in inlets however but even those were all either very low speed helicopter or very high speed multi mach supersonic."​

Now was that just a Freudian slip - propulsion curses?

 

[drgondog]

I will take that as - "As an airframe specialist, I don't give a stuff about powerplants."

DragonDog quote:

"Somewhat true - engine design is a deep and complex discipline. I took two propulsion curses and discuss aspects of the theory (after 45 years) but never designed an engine per se. Have been involved in inlets however but even those were all either very low speed helicopter or very high speed multi mach supersonic."​

Now was that just a Freudian slip - propulsion curses?

simply poor proofreading - I did well in the courses but also serene in the knowledge that I wouldn't be interested in working up north central/east US where GE and Pratt are located..

 

[drgondog]

This seems to me to confirm what I believe we have agreed, that the Schwalbe wing design was optimised for a relatively narrow high speed interceptor role.


Regards,

Magnon​

I am not so sure that such statement has enough data to support the conclusion.. The aspect ratio of the 262 wasn't particularly remarkable for interceptors of the day -

In addition, the Me 262 wasn't following traditional rules for such per se, nor was the meteor.

The imbedded/low mount twin engine designs necessitated by low thrust engines dictated much of the wing design. Had the 262 provided for a much larger internal fuel capability, there would have been more options for wing planform and t/c ratios to reduce drag more.​

 

[delcyros]

I have attached a copy of bench testing on the JUMO over a period of 7.5 hours. It is generally accepted that three hours on a test banch were equivalent to around one in combat. (That's assuming the engine wasn't "cooked" in a panic opening of the throttle or due to a surge event in combat).

From the graph, I'd estimate a 2.5% drop in thrust and 4.5% increase in specific fuel consumption. It would be reasonable to surmise that over the usual ten hour JUMO engine life in combat, a very much more dramatic drop in performance of the aircraft would result.

The other thing I'd like some feedback on, one way or the other, is the analysis on on post #34 on http://warbirdsforum.com/showthread.php?t=451&page=4

The bottom line here was:

Summarizing, the speed margin of the 262 versus the wartime Meteor III equipped with the 2000lb S/T engines would be
Sea level 4mph (0.82%)
5K 12mph (2.45%)
10K 20mph (4.04%)
15K 24mph (4.81%)
20K 34mph (6.83%)
25K 38mph (7.72%)
30K 24mph (4.94%)

Two factors limited the Meteor III's speed, i.e. a structural limit of 500mph and a critical mach of 0.74, whichever was met first.​

Regards,

Magnon

Magnon, You have to be more careful with selecting Your sources and jumping from individual samples (ONE TEST on ONE engine at ONE given day) to general conclusions. Put them in a meaningful statistic in the first place would be my primary advise. This may allow the interested reader to judge whether or not the sample has significance for the whole Jumo-series or not. You may find the relevant primary sources in the Freiburg Archive (but it may be possible that some of the material relating to Jumo benchtest moved to Berlin since 2002) and I know that a roughly 2in thick agglomeration of single benchtests is there. That beeing said, I greatly appreciate Your input here.

The speed margin of wartime Me-262 (with all the plane to plane variation) and Meteor is significantly different from what You suggest. It´s not a single value but a spread of discrete points. For the Me-262 You may find the Rechlin mass tests on 142 serial Me-262A1 intersting. Tests were conducted late in 1944 with top speed measured in different altitudes and clacluclated back to standart atmosphere, but the paper dates to early 1945 (I think it was RG-Lunatic who digged out this source first in another -262 relevant post). It would be highly interesting to see a comparable convolution of serial Meteor-III tests before jumping to general statements.

Best regards,
delc