The sound barrier (1 Viewer)

[drgondog]

Well as you know at close to Mach 1 even small defeciencies can be fatal. Lets say a panel comes off at Mach 0.85 because of a small gap made in assembly, well that could cause the whole a/c to come apart.

If you think a 1/4" gap between butt joint panels would make a difference at Mach 1, much less Mach 2 - you have never seena Mig 21 up close. 'gap's might make a difference in drag if those panels were immersed in a boundary layer but you wouldn't notice it in turbulent region.

Wrong argument.

The pace at which a/c were being contructed in 1945 as well as, and no less, the circumstances under which they were made, enevitably caused a lot of quality issues. But to make matters even worse the LW, in order to get enough a/c in the air, had to significantly lower their quality acceptance demands. Hans Fey also notes the lower quality acceptance demands and differing workmanship between a/c in the report on the site I referenced earlier.

The only 'quality issues' that would make a lot of sense would be heat treat/metullurgy issues on High strength fastners and casting/forgings. You have any data showing those were the issues of concern?

Infact by 1945 Hungarian built 109's were considered to be of much better quality than German built ones.

You said earlier that 'only a few' 262s exhibited a tendency to hunt' - which is at variance with all the 262s tested by USAAF after the war. You stated those were 'quality issues'?? also. With respect to what?



Yes, but will it stay together ?

That HAS been the question Soren with zero substantiation that yes, the me 262 as designed and built, will in fact take the aerodynamic loads associated with .89- 1.0 Mach..

and that the pitch down issue at .83 to .86 was somehow solved, that the associated bending and torsion forces that would be experienced attempting to control high speed yaw (on Rudder) and pitch (slab tail with very high associated stick forces) were 'not a problem' and shown to be so with rigorous stability and control analysis coupled with professional aero analysis and advanced structural solutions taking all that into account..

Why isn't the logic and fact base so compelling that anyone (not even Everyone) agrees with you.. Messerschmidt didn't, the RAF and USAAF Test pilots didn't, I have seen zero LW Test pilots giving testimony in 1944-1945 when they were actually flown, the Russians quit flying it past .86 after barely surviving the experience, the Czechs (to my knowledge) never pushed it past .84. THERE is a HUGE drag rise between .82 and .9 - much less 1.0 assuming stability and control issues were ever solved.

The modern day builders (Stormbird) placard the airframe at 540kts at SL (~.82M) despite a far superior engine, improved internal structure and internal/extenal quality. Why?

You think you have made your speculative case?

 

[drgondog]

The MiG 15 had its tail mounted near the top of a very large fin, surely a major flutter problem when nearing mach unity? When they built a supersonic fighter MiG moved the tail to ther rear fuselage, like it was on the F-86

I understood the primary problem for the Mig 15/17 was also Pitch down in the transonic as the shock flow moved the CP to 50% chord region without enough deflection in the elevator to fully compensate.. but it has been a long time since I even thought about that so I could be wrong.

Flutter is almost always an issue when a control surface is immersed in a turbulent wake - or the natural frequency of the control assembly is close to the input forces/frequency of the airflow and vortices being shed upstream.

 

[FLYBOYJ]

Slight digression here but wasn't the first British pilot to exceed Mach 1 Roland Beaumont in a USAF F-86? Albeit unofficially. I'm sure I read that somewhere.

I believe you are correct

The MiG 15 had its tail mounted near the top of a very large fin, surely a major flutter problem when nearing mach unity? When they built a supersonic fighter MiG moved the tail to ther rear fuselage, like it was on the F-86

That was done, but I think the non-area rule fuselage and the wing fences also played havoc at transonic speeds as well.

 

[Waynos]

Yes, quite so. I know that the MiG 19 prototype had a high tail like its predecessors and that it was very quickly changed, I'll nip off to see if I can find out why.


Apparently the reason was spin recovery, rather than flutter.

 

[Soren]

You said earlier that 'only a few' 262s exhibited a tendency to hunt' - which is at variance with all the 262s tested by USAAF after the war. You stated those were 'quality issues'?? also. With respect to what?

Do you have a source for that claim Bill, and how many is all ??

I have a source for the fact that only a few Me262's exhibited the tendency to hunt: Me-262 test pilot Hans Fey, Allied Report, the site I referenced, written in big bold black letters.

 

[Soren]

If you think a 1/4" gap between butt joint panels would make a difference at Mach 1, much less Mach 2 - you have never seena Mig 21 up close. 'gap's might make a difference in drag if those panels were immersed in a boundary layer but you wouldn't notice it in turbulent region.

Lets say the left gun cover comes off at Mach 0.86, that'd be pretty serious Bill. If wind is allowed inside a gap it will eventually, with increases in speed, increase the gap and lift the entire panel off.

 

[FLYBOYJ]

Lets say the left gun cover comes off at Mach 0.86, that'd be pretty serious Bill. If wind is allowed inside a gap it will eventually, with increases in speed, increase the gap and lift the entire panel off.

Ive seen access covers come off F-4s that went way more than mach 1 - most of the time nothing happened.

Gaps in structure could be detrimental depending where they are located. Again all this is highly subjective.

 

[pbfoot]

Ive seen access covers come off F-4s that went way more than mach 1 - most of the time nothing happened.

Gaps in structure could be detrimental depending where they are located. Again all this is highly subjective.

ditto but on 104's

 

[drgondog]

Lets say the left gun cover comes off at Mach 0.86, that'd be pretty serious Bill. If wind is allowed inside a gap it will eventually, with increases in speed, increase the gap and lift the entire panel off.

And 1.) you know this how?, and 2.) so what?

It would be more serious if the nose tuck kept putting extraordinary forces on the tail

I'm not saying it doesn't happen or it doesn't have consequences - but I believe this round robin has been all about Mach 1 in an Me 262. Example please of real world 'actual's rather than Soren 'hypotheticals'?

 

[DerAdlerIstGelandet]

Well as you know at close to Mach 1 even small defeciencies can be fatal. Lets say a panel comes off at Mach 0.85 because of a small gap made in assembly, well that could cause the whole a/c to come apart.

That depends on the panel Soren. If a structural panel comes off, possibly it will make the aircraft come apart (possibly, not certainly).

Just any old panel though, probably not.

Lets say the left gun cover comes off at Mach 0.86, that'd be pretty serious Bill. If wind is allowed inside a gap it will eventually, with increases in speed, increase the gap and lift the entire panel off.

Again Soren, not nessessarily. Just because a panel comes off in flight is not neccessarily going to cause anything.

Do you know the difference between "any old" panel and a structural panel?

 

[claidemore]

One of the problems with Mutkes story, is confusion about when he reduced engine power and flamed out. The way it is written in some sources, one could mistakenly assume he reduced engine power after the plane stopped buffeting and had smoothed out. Question is, why would you do that? If the plane has stopped buffeting, and is flying smoothly, why do anything?

Others sources make it clear that he reduced power when the plane initially started buffetting.

Not all sources mention the few seconds when the 262 supposedly stopped shaking then resumed, and even if that happened, it is not conclusive proof of supersonic flight. It is only proof that the plane stopped shaking, for all we know it could have reduced speed enough to stop shaking (after engine flameout), then increased speed because of the nose down pitch, until Mutke finally managed to trim it out. In fact that is the far more likely chain of events, one that all the other evidence would support.

Another question is; if Mutke knew the speedometer was stuck at 1100 kmh, and reported it, was there nobody amongst all those jet jocks at his airfield that knew what the speed of sound was? Why didn't somebody say "Holy freeolies Batman, you must have broke the sound barrier!" Another discrepancy is that some sources say he figured out what he might have done after Yeagers flight, (1947) and other sources say he didn't figure it out till 1989.

Since this happened in April 1945, when was this particular 262 built? If we follow the theory that late war 262's were of inferior build quality, how could this one survive going supersonic?

Also, if Mutkes engines flamed out, there was no more thrust, mooting the point about zero thrust from the prop driven Spitfire. We should note that the Spit XI was a very clean plane, polished finish, gaps sealed and smoothed out, no guns, no ammo bay bulges, no armored windscreen etc.

We should also remember that the 262 did not have a true 'swept' wing, (18.5 degrees) and that fact is pointed out in almost every reference on the plane. A proposed sweep of 45 degrees (HG III)had a projected speed of Mach .96. Mutkes plane is reported as having structural damage to the wing, so not only was there danger of tail damage, but wing failure as well.

As for the study done in 1999, every plane is designed by experts in aerodynamics, and nearly every plane exhibits behaviors that the designers didn't anticipate and have to make corrections for. Unless someone actually puts a 262 through a test program and proves with instruments that it can go supersonic,the 1999 study is at best theoretical.

 

[KrazyKraut]

German fighter aircraft near the end of WW2 were "in general" of lower quality. That doesn't mean that every single example was. So this is no proof or indication whatsoever. If you want to disprove or prove anything, resorting to even more highly speculative argumentation like you did in that entire post doesn't help anything.

The 1999 study may be theoretical but at least it's based on facts and figures not suggestion.

 

[kool kitty89]

The 004 has neither a convergent-divergent nozzle nor reheat and so the thrust massively drops off by Mach 1. Far more important is the fact that you're in a dive and gravity is pulling you earthwards - which is why a Spitfire can accelerate up to M0.94.

The Me 262 had negligible wing sweep. The effect can be calculated by taking the Cosine of the sweep angle. This reduces the effective thickness by an entire 5% to give an effective thickness of 10.5%. This is a far cry from the 5% and 6% t/c for other high transonic aircraft (and most are much cleaner designs)

Actuall, at the wing center section (inboard of the nacelles) the Me 262 has 0 sweep, just a LE extention to match the swept outboard sections. (so these sections would be the full 11% chord) Additionally, the root had the max thickness at 35% chord rather than 40% on the outboard sections. (the outboard section tapered from 11% at 40% chord to 9% at 40% chord, not taking sweep into account)

PS: The X-1 barely had any wings, more like fins

Actually, for its size, the X-1's wing was rather substancial, and fairly thick all things considered. At 10% thickness, the XS-1 (X-1-1) had a thicker wing than the F-86 (9% at root) without even taking sweep into account. The later X-1-2 and X-1A/B/D had 8% thick wings. Now, the F-104 had fins!

On straight winged transsonic aircraft, 10% thickness/chord ratio seems to be the max for the wing. The Skystreak, F-94C, and CF-100 all having 10% TR airfoils (the CF-100's not even being a laminar flow section, but a conventional NACA 0010) and all three were capable of diving through Mach 1.

 

[kool kitty89]

Given the airfoils used on the MiG-15 and 17, they should have significantly high critical Mach numbers to safely get to Mach 1. However, it would seem the limitig factor is the tail configuration, the horizontal stabilizer/elevator losing control ability near Mcrit. It would seem that neither featured a trimmable stabilizer or boosted elevator controls, let alone "all flying" tail.
I don't think the fences were really an issue though, being features of several supersonic aircraft many Soviet, and the F-102.



The F-86's boosted elevator seems to have been fully functional up through Mach 1, with no mention of trim being used to recover from supersonic dives in several accounts I've heard and read. (including Welch's, and prior to the F86E the Sabre didn't feature an all flying tail, but a boosted elevator with a fully trimmable tailplane)


The MiG's lack of boosted alevator controls also hampered maneuverability at high speed.

 

[Soren]

There's is no confusion regarding when Mutke shut his engines Claidemore, he shut them down after entering smooth flight as he regained control, it all went really quick. You should read Mutke's first hand account, there he explains in detail what happened.

He had entered a dive at full speed from an altitude of roughly 12,000m when suddenly his a/c began to shake violently, his airspeed indicator stuck against 1,100 km/h. He tried to recover by pulling back on the stick but the a/c just kept increasing the dive angle, he had no elevator control. Then suddenly all the vibrations stopped and a smooth 10 second ride followed, immidiately he shut the engines and started trimming the tailplane, and as the a/c started to recover the vibrations started again unil finally he leveled out at 8,300m.

 

[kool kitty89]

Soren, do you have a link to Mutke's story?

The previously mentioned page on luftarchiv.de no longer seems to exist: http://mach1.luftarchiv.de/mach1.htm

 

[Soren]

That's the one I was going to link KK. Didn't it work just a couple of days ago ?

 

[Soren]

And 1.) you know this how?, and 2.) so what?

Bill if a panel like the gun cover were to be ripped off a Me-262 at Mach .85 then it can only be serious. Hae you seen how big that panel is and where it is located ??

It would be more serious if the nose tuck kept putting extraordinary forces on the tail

Again only a few exhibited this behavior.

I'm not saying it doesn't happen or it doesn't have consequences - but I believe this round robin has been all about Mach 1 in an Me 262. Example please of real world 'actual's rather than Soren 'hypotheticals'?

The flight wasn't recorded Bill, so it's a matter of opinion wether one believes the Me-262 went supersonic or not, different arguments popping up in support of both scenarios.

 

[Juha]

Soren
Quote: " I was presenting arguments from all parties Juha."

Now I understand that presenting arguments from all parties means presenting arguments for and against something, not that one tries to proof one's own POV by presenting arguments that one him/herself doesn't believe.

Quote: "Well it supports it a lot in my mind as the Me-262 was over 200 km/h faster in level flight."

Now IMHO it's rather well known fact that at least in 40s the level speed wasn't a very reliable indicator for the max Mach number possible for certain a/c. Think for ex P-47 and Spitfire XI. And putting a jet engine on a/c not necessary helped either see for ex Saab J 21A vs 21R. Putting a jet engine into J21 increased level speed but not the max Mach number. And see Waynos message #157 for further info.

Quote:" The X-1 barely had any wings, more like fins"

Now IMHO X-1 clearly had wings.

Juha

On Mutke's story, to me as an historian the greatest problem is, why to wait 50 years before tell it. He would not be the first one whose stories got better with time. In the end it's a question of what we believe. To me his story is possible but not probable, too many things had to go just right by chance, but of course there is the possibility that he was very lucky.

Juha

 

[KrazyKraut]

I have no doubt that his account is true. When it was made public is of little relevance to me. The man led a life outside of this stuff and just because WE argue about whether or not lift loading is a relevant or valid measure does not mean every other person in the world cares.

I have talked to veterans of the Panzer force and they didn't even know half the subtypes or specifications. They simply didn't care. Rall himself made several mistakes in interviews about the Bf 109. Does that make him less credible?

The question to me is not whether his account is true. The question is if the evidence is enough to conclusively say that the man broke the sound barrier. Which it is imo not. The symptoms he described also occur when an aircraft nears the sound barrier or can be attributed to the actions he took. So I agree with you that while it is possible he broke the sound barrier, there is no conclusive evidence that he wasn't just close to it.