Advanced designs

[kool kitty89]

I didn't say anything about developing the HeS 011 preferentially. I actualy think it was not that great of an idea to go with (design was good but not practical for the time frame). It did manage to produce the originally specified ~2860 lbf, though the expected 3000+ lbf advancement was never reached.

I suggested continued work on the HeS-30 (109-006) class 1 axial design, which was developing very well by the time it was canceled in 1942. It was nearing production quality and thrust appeared to be about to exceed that of the 004 engine (900+ kp) It would have certainly been ready for production before the 003 and possibly even before the 004B. With about half the weight and size of the 004 with similar thrust and good SFC, probably similar to the 003's 1.4 lb/lbf/hr. But at the time the RLM thought that the 004 and 003 were far ahead and about to be ready for production and that they simply didn't need another axial design.

I think it would have been best to focus on the less problematic class I designs. Also I said Ohain should have tried working with axial turbines like Whittle did, as the radial turbine (though good for an uncooled design) was heavy, and too large to use turbine alloys practically and couldn't be air-cooled practically. I also flame-cans (opposed to annular combustors) would have been much easier to work with. Axial turbines had also been explored more than radial-inflow types had. (like centrifugal compressors over axial) Such an engine with air-bleed cooled turbine should have offered higher operating conditions and have higher efficiency, and would be easier to scale-up to a class II sized design. (ie 2,700 lbf Halford H.1 in England)

As I mentioned above.

I certainly agree that Britain was slowed by 2 years due to Rover's mismach, as at the time Rover was chosen Whittles achievements were only weeks behind Ohain's. And in some ways ahead, as Whittle's WU could run on Diesel while the HeS 1 ran only on Hydrogen, and Heinkel's team was still considering gasoline as fuel for the HeS 3. Of course Heinkel's own project was later held up by several months due to delay in aquire Hirth due to political problems (possibly due in part to Messersmitt). And Muller wasn't receptive to Hirth help, which finally happend after Muller left iirc.

Though I'm not sure if the Derwent (and Nene-Derwent-V) would have developed the same if R.R. had worked with PowerJets earlier, possibly the W.2 700 (2,500 lbf) would have been produced instead, though the W.2Y (Derwent) may have been developed too, I'm just not sure. Of course the Halford H.1 Goblin (2,700 lbf) could have also been used if not diverted to the Vampire, or perhaps R.R. could have licensed production of the Goblin for use in the Meteor Mk II. As I still doubt a Nene or especially Derwent V engine would have been available in numbers by early 1945, with decent reliabillity. (as even the J33 was struggling in productin and reliabillity at this time)

 

[kool kitty89]

As it was, the Meteor F.III was doing ~520 mph with long nacelles. (I think they were still using Derwent I's)

Did the Meteor III ever use Derwent II's (2,200 lbf) or IV's (2,420 lbf)?

I'd think they'd have upgraded them as better marks became available. (like how the first ~15 were down-graded to Wellands due to lack of Derwents)

As said the Meteor Mk II with 2,700 lbf Goblin I's would have been good too, but they were diverted to the Vampire... (Which was outperforming the Meteor by this time, and with far less engine-power and only one engine)

 

[kool kitty89]

Does anione know if production Metor F.III's used Derwent Mk.II's or Mk.IV's (Mk.III's were II's experementally fitted with a vacuum pump for boundary layer control). It would make sence as these were available prior to the war's end, but I've never read about their use, in any a/c for that matter.

Use of these engines on the Meteor, along with new nacelles should have allowed top-speed, and climb performance to match the 262's and turning should be better with lower wing loadin, though there would still be problems with airflow separation over the thick tail surfaces at high speeds. (not fixed until the advent of the new tail seen on the F-8) Though the ailerons were still wired heavy, the Me-262 was no fast roller either due to the long and heavy engines.

 

[Soren]

Multhopp has always maintained that he would have made modifications to the P.183 design along the way as development would have played out if the project had reached fruition.

Very true Twitch. And one thing which would've been realized (was already planned) was the need for either LE slats or wing fences on the Ta-183, or there would be tip stall issues.

The predicted performance of the Ta-183 with the HeS-011 engine is very impressive, a 1,000 + km/h top speed and 6,000 + ft/min rate of climb, not bad.

 

[Soren]

Use of these engines on the Meteor, along with new nacelles should have allowed top-speed, and climb performance to match the 262's and turning should be better with lower wing loadin,.

Nope, the Meteor still wouldn't be able to turn with the Me-262, the 262's full span LE slats more than making sure of that.

 

[kool kitty89]

The meteor could probably turn better at low to medium speeds speeds (below 450 mph), though certainly not at high speeds as the early Meteors had serious problems with airflow separation over the tail surfaces at high speed. (starting at ~500 mph) The 262 should also have had better speed retention, while the Meteor may have had better initial acceleration with a net thrust of 4800 lbf with derwent IV's, and probably a better climb rate too. At ~13,800 lb gross weight, it would have had a thrust/weight of nearly .35!

Rember also the Meteor III had quick-deploying maneuvering flaps to aid in turning too. (I'm not sure if it had airbrakes yet, but I think so; I know the YP-80A's didn't get airbrakes though)

Still I have no knowlege as to the usage of Derwent Mk.II or IV engines on any a/c, but it stands to reason that they would replace earlier marks for production, and as the Meteor was the only craft using the engine it would be the one to recieve it.

 

[kool kitty89]

Of course it's lift loading that realy affects turning ability and climb, and this would depend on wing efficiency, though I'd expect the Meteor would be better at low to medium speeds due to the thicker airfoil and there's still the flaps andor airbreaks to considder.

But above 450 mph (depending on altitude) the Meteor starst to get unstable, particularly at altitude, due to airflow separation over the tail. And crit mach was low untill the new nacelles were added, but even then only ~.79 mach.

 

[red admiral]

But above 450 mph (depending on altitude) the Meteor starst to get unstable, particularly at altitude, due to airflow separation over the tail. And crit mach was low untill the new nacelles were added, but even then only ~.79 mach.

Critical Mach was about 0.83-0.85M for the F.4 with longer nacelles. Max speed was around 580mph at 10,000ft, then the performance is Mach limited.

 

[delcyros]

Red Admiral, my figures give lim. Mach =.81 for the F IV with long nacelles, that would resemble about .83 to .84 for crit Mach, respectively, matching Your figures nicely. The buffeting was serious at these speeds. And more worrisome, the Meteor never was cleared for full acrobatics.
The air brakes didn´t allow higher tactical speed, they had to be deployed before reaching 400 IAS.

 

[kool kitty89]

The Meteor III wasn't cleared for areobatics due to wing structural issues, the same reasnon for the heavy ailerons. (later fixed on the Mk.4 with a stronger airframe and clipped wings, though the clipping was also to reduce drag iirc) I beleive it the problem was discovered when first testing the more powerful Derwent I engines in the prototype Meteors and one suffered a structural failure to the wing durring high-speed maneuvers. The airframe of the F.III is the same structure as the Mk.I iirc, thus it wouldn't have been untill the strengthened structure of the Mk.4 that high-speed aerobatics would be safe, though clipped wings alone on the F.III may have been enough to allow high-speed maneuvers due to the decreased stresses, at least in the intrim (as was done with some Griffon engined Spitfires prior to wing strengthening to the airframe), but this was't done for the F.III, so it doesn't really matter.

I remember reading that mach limit for the Vampire Mk.I and Meteor III were both .79 Mach at SL, though this would increase with altitude as well and crit mach would be higher as well. Thise figures may be only for the short nacelles though, and it may very well have been stable into the 500 mph region, but once into the .8 mach area conrol became some what unstable iirc, though I may be wrong.

I was pretty sure the Meteor IV had some serious separated flow over the tail near the mach limit as well, a problem that wasn't overcome until the F-8 type tail was introduced.

 

[Soren]

Of course it's lift loading that realy affects turning ability and climb, and this would depend on wing efficiency,

Which is why the Me-262 turns better.

The Me-262 features full span automatic LE slats as well as a higher AR wing, giving it a better L/D ratio and much higher CLmax, the slats alone raising the CLmax critical AoA by 25%. And then there's the extra thrust which is important to turn performance as-well.

 

[kool kitty89]

Similar to the Bf/Me 109's slats, though those weren't full span and were mainly to improv aileron control when near stalling iirc.

But high wing efficiency and slats only go so far when you're comparing such a difference in wing-loading with ~60 lb/ft2 for the 262 compared to ~37 lb/ft2 for the Meteor III both at max-take-off. (14,100 lb for the Me 262 and 13,800 lbs for the Meteor). But as said the Meteor wasn't officially cleared for aerobatics and had compressibillity problems. (high-speed controll problems being encountered well below the Mach limit iirc)

Besides, high-speed a/c (particularly in this time period) were at their best when used as "energy tactics", though this is more important when fighting aganst piston planes particularly (due to better initial acceleration and low-speed handeling of such opponents) similar tactics were utilized by P-47s with their high wing-loading and excelent speed retention and dive performance. Likewise the Me-262 would hve better speed retention due to the cleaner airframe with very low drag. The high thrust of the Meteor F.4 largely made upo for this (as well as improoved aerodynamics and airframe) that's a differen't story...

The P-80 and Vampire are a bit of a different group, though both of their early models had lower Mach limits as well, though improovements came realitively quickly after the war and anything above .75 mach would only apply to dives. Also, compared to the early Meteor, these two vraft performed well in maneuvers into the 500 mph range. (though the YP-80s did have a problem with boundary layer separation in the intakes)

 

[Soren]

Keep focus for a moment now Koolkitty,

The slats were not put on the Bf-109 for improved aileron control, they were put on to delay tip stall and increase the CLmax critical AoA of the entire wing, dramatically improving turn performance and lowering the stall speed of the a/c.

The Me-262 needed full span slats partly because its wing thickness ratio hardly changed through the entire span, but mainly because it was a jet fighter and the engines weren't pushing air over the first 45-55% of the wing span. For this reason the Me-262 needed full span slats, cause otherwise CLmax critical AoA would vary too much and tip stall would still be a problem.

Now on the Me-262 vs Meteor debate;

Lets compare weight with no fuel as the fuel consumption was about the same for both a/c.

Me-262
Empty equipped weight: 3,800 kg
Wing area: 21.7 m^2

Wing loading = 175.11 kg/m^2

Gloster Meteor
Empty equipped weight: 4,800 kg
Wing area: 32.52 m^2

Wing loading = 147.6 kg/m^2


Now let us ignore the increase in CL the higher AR causes and alone consider that the Me-262 benefits from a increase in lift critical AoA by 25% because of its automatic LE slats:

175.11 * 0.75 = 131.33 kg/m^2

So as you can see the slats alone more than makes sure that the Me-262 always will out-turn the Gloster Meteor.

 

[delcyros]

Wing loading = 147.6 kg/m^2


Now let us ignore the increase in CL the higher AR causes and alone consider that the Me-262 benefits from a increase in lift critical AoA by 25% because of its automatic LE slats:

175.11 * 0.75 = 131.33 kg/m^2

So as you can see the slats alone more than makes sure that the Me-262 always will out-turn the Gloster Meteor.

Some points to consider:
wingloading isn´t everything. Without knowing the exact lift coefficiant and the condition of flight, You cannot make such a simplification.
The Meteor had a thick wing with large chort (large RE-numbers) and correspondingly high lift coefficiant.
The Me-262 had a comparably thin wing, the chort varied from very large on the wingroots to very thin on the wingtips with correspondingly different RE-numbers and compared to the Meteor a significantly lower lift coefficiant, which could be improved by deployed slats by about 25% only at very high angles of attack. At such an angle of attack, the wing of the meteor would already be stalled, in every other aoa, the Meteors wing provides more lift. Turning that hard is only possible at very low speeds (g-issues) and would bleed off Your energy quickly.

 

[red admiral]

Lets compare weight with no fuel as the fuel consumption was about the same for both a/c.

If by "about the same" you mean the Ju 004 was roughly 50% worse you'd be correct. Best to compare the weights at half-load. The lower AR wing is better for maneuverability, especially in the roll, but both planes roll pretty slowly on accont of the mid-wing engines.

 

[Soren]

Delcyros,

You apparently do not understand the function of the slats very well. The slats start to deploy at a very low AoA, and then gradually (Or immediately depending on the ferocity in the increase of the AoA) extend until they can no more. In a maximum performance turn the critical AoA has been increased by 25%, and so has lift, giving the Me-262 the edge. The Me-262 can easily pull critical AoA even at high speed, however depending on how fast it's going the G forces might be to great for the airframe - something like 8.5 - 9 G's, plus at those loads the pilot is no longer concious.

Also that the Meteor reaches its CLmax earlier in the AoA range is no advantage. Because of the slats the Me-262 can pull steeper turns at all speeds and because of this is helped more by its available thrust as the vector has been increased.

Also AFAIK the Me-262's wing thickness ratio stayed very close over the entire span, something like 10 to 9 or 8.5. The main reason for the full span slats was however that there was no additional thrust over inner parts of the wing.

Red admiral,

Low AR is ONLY good for roll rate, it is bad for turn rate as induced drag is increased.

 

[delcyros]

Delcyros,

You apparently do not understand the function of the slats very well. The slats start to deploy at a very low AoA, and then gradually (Or immediately depending on the ferocity in the increase of the AoA) extend until they can no more. In a maximum performance turn the critical AoA has been increased by 25%, and so has lift, giving the Me-262 the edge. The Me-262 can easily pull critical AoA even at high speed, however depending on how fast it's going the G forces might be to great for the airframe - something like 8.5 - 9 G's, plus at those loads the pilot is no longer concious.

Also that the Meteor reaches its CLmax earlier in the AoA range is no advantage. Because of the slats the Me-262 can pull steeper turns at all speeds and because of this is helped more by its available thrust as the vector has been increased.

Also AFAIK the Me-262's wing thickness ratio stayed very close over the entire span, something like 10 to 9 or 8.5. The main reason for the full span slats was however that there was no additional thrust over inner parts of the wing.

Seriously, Soren, slats do not deploy at low or moderate AoA´s. They do pop out close to the point where the airflow does change to turbulent or seperated, which is typically only valid for high angles of attack. At low or medium angle´s of attack, LE-slats do not add to the lift coefficiant. So You need a condition of flight were such extreme aoa-conditions apply. This is only at low speeds possible due to g-issues. Deployed slats greatly increase the drag and any Me-262 driver is better advised to keep his "e" as high as possible, esspeccially since the energy retention (=acceleration) of this A/C is pretty low.

 

[kool kitty89]

Soren, the weight figures on the Metoer don't match up for what I've read, they do match those of the Meteor Mk.4 and F-8 fairly closely, but these are more than 1000 kg heavier than the Mk.I and III. (both the structure and weights of the Mk.I and III were about the same with empty weight of ~3700 kg and ~6,260 kg max take-off)

The wing area figures are also off with even the clipped wings of later models being 350 ft2 (~32.5 m2) and the Mk.I and III having an even higher with 374 ft2 (~34.8 m2). So the results would be much different.


On the engine efficiency, the 004B used 1.44 lb/(lbf hr) in the best versions (though at its worst the 004B may have consumed closer to 1.8 lb/(lbf hr) but I don't have a refrence for the actual values), while the Welland used 1.12 lb/(lbf/hr) and the Derwent I used 1.18 lb/(lbf hr). (note that using kg of fuel and kp force doesn't change the values) For refrence the De Havilland Goblin used 1.14 lb/(lbf hr), the HeS-3B used 1.60 lb/(lbf hr) and the BMW 003A used 1.40 lb/(lbf hr) though this was improved in the 003E model of the same thrust iirc, as did the 004D.

However, the low-drag airframe of the Me-262 partially made up for the poorer fuel efficiency, though it was likely not enough to fully compensate in comparison to the Meteor. (particularly with long nacelles and other drag reducing modifications)

 

[Soren]

Seriously, Soren, slats do not deploy at low or moderate AoA´s. They do pop out close to the point where the airflow does change to turbulent or seperated, which is typically only valid for high angles of attack. At low or medium angle´s of attack, LE-slats do not add to the lift coefficiant.

Seriously, Delcyros, that is incorrect. The automatic LE slats start to deploy already at low AoA's, that's fact.

The LE slats work by delaying boundary layer seperation, increasing the critical AoA CLmax of the airfoil by approx. 25% in the covered areas. The slats function by means of airpressure, as the the pressure starts to decrease on the top of the wing the slats start to deploy, the speed of which is completely determined by how quick the change in AoA is.

Bf-109, Me-262 F-86 pilots generally all loved this device because of its very positive effect on the turn rate stalling speed of the aircraft.

So You need a condition of flight were such extreme aoa-conditions apply. This is only at low speeds possible due to g-issues.

Incorrect. The airframe is the limit, which means 8.5 - 9 G's.

What the slats do is allow the Me-262 to reach its limit earlier in the speed range than the Meteor. At very high speeds it all becomes equal as a max performance turn will either rip the wings off the a/c or make the pilot unconcious.

Deployed slats greatly increase the drag

And that is downright wrong. Automatic LE slats do NOT increase drag at all Delcyros. What you're thinking about is fixed LE slots.

Automatic LE slats function by means of airpressure, extending gradually as the pressure on the top of the wing gradually decreases as AoA is increased. There will NOT be any "stepped" increase in drag when the slats deploy, only at the point where even the slats cannot prevent the wing entering a stall, this is at the critical AoA, but that goes for all wings, with or without slats. When the critical AoA is reached drag is suddenly and violently increased and now overcomes lift, creating a stall.

But, the tighter your turn the more the drag, and that is universal. So when the Me-262 turns tighter than the Meteor it is whilst generating more lift also generating more drag.

and any Me-262 driver is better advised to keep his "e" as high as possible, esspeccially since the energy retention (=acceleration) of this A/C is pretty low.

Again you're incorrect, by virtue of its clean design the Me-262 has much better energy retention in maneuvers than piston engined a/c. Furthermore energy retention is NOT acceleration, it refers to the rate of energy loss in maneuvers, and here the ME-262 retains its energy much longer than any piston engined fighter.

LuftWaffe test-pilot technical inspector Hans Fay:
"The Me-262 will turn much better at high than at low speeds, and due to its clean design, will keep its speed in tight turns much longer than the conventional type aircraft"

Me-262 POH, Flight characteristics:
"(2) The airplane holds its speed in tight turns much longer than conventional types"

 

[kool kitty89]

I'm not suer what Delcyros meant by

and any Me-262 driver is better advised to keep his "e" as high as possible, esspeccially since the energy retention (=acceleration) of this A/C is pretty low.

either, but it is true that the Me 262 accelerated poorly compared to most prop-driven fighters (particularly at low speeds), but I certainly agree that the Me 262's energy retention is excelent compared to piston-engined fighters and the Meteor. (and probably the He 280 and Vampire, but probably similar to the P-80A and He 162) It performed best when used as an "energy fighter".