The sound barrier

[drgondog]

KK,

The Me-262's horizontal stabilizer isn't emersed in turbulent flow, that's the reason it is placed so high, to keep that from happening. The thing that is causing the elevator trim tabs not to work is the shockwave forming near the rear of the horizontal stabilizer, causing turbulent flow over the control surfaces, the elevator trim tabs, rendering them ineffective. That is why the all moving tail plane works and the elevator trim tabs don't.

Wrong on "the shockwave at the trailing edge of the horizontal stabilizer"

A shockwave at the trailing edge only occurs when the ac is 100% supersonic in which case there would also be a shockwave at the leading edge.

In that case there is a corresponding shock wave at the leading edge of the nose, wing and tail, as well as a shock wave at the trailing edge of the wing and tail. In front of the leading shock wave(s) is subsonic flow, in between the leading and trailing shock waves is supersonic flow, aft of the shock wave is subsonic flow. The angle of the shock wave is proportional to the Mach.

You are a self proclaimed expert at ballistics are you not? The physics works perfectly for bullets travelling faster than sound.

The Me-262's stick never froze or became stiff, the control forces remained light throughout the speed range.

Lindner and others are very explicit regarding the enormous stick forces required (50kg at .86) as the 262 progressed from .82 Mach. He specifically notes his struggle with both hands on stick trying to prevent the nose down tuck until he was able to free one hand to retard the throttles - and survive.

So, it raises the question what do you consider 'light stick forces'??

True, again the reason for mounting the tail plane high. The reason for the all moving tail plane being used as the main control surface for pitch was to improve maneuverability in transonic supersonic flight.

True, but 'high' is relative.. out of the wake turbulence of the wing body is appropriate in more cases than a T tail

 

[Erich]

well gents it is awful tough to prove anything I suppose, Messer was not interested in Guido's max out the jet flight he was involved head over heels with last ditch LW test trials of unknown swept back winged A/C for 1946 and beyond. Some day possibly we will get a full on report, we can gather all the factoids with graphs and what we know about the sped of sound but we also know for full on reasons that many LW docs during 1945 are lost to the wind, maybe just that special day will come when something buried is back from the lost and found and will tell you some of the LW JG materials were buried as such at their A/F's
~ in the report and it it is singed in my brain is that the rivets were popping the wings were buckling under the speed of the descent

 

[DerAdlerIstGelandet]

Only ? Adler the gun cover panel on the Me-262 was large and if torn away would create a very large gap in the nose and as-well as a large blunt area directly facing the airstream.

Perhaps not, but it depends alot on its position compared to the incoming airstream.



Absolutely, but like I said much depends on its position in regards to how dangerous it is to loose it midflight.

Soren, more than likely it would not tear the aircraft apart. The pilot would have to lower the airspeed but he could fly the plane home and land. But what do I know? I am only trained and qualified to work on structures...

All you are doing speculating and making up your own facts and truth.

That is okay though, the forum is used to it after all these years.

 

[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.

Soren - ???? this 'red herring' was trotted out by you as a continuation of the poor quality issue you posed regarding 262. Everybody agrees that a panel coming off at .86 is potentially serious. Now what?

BTW - with reference to yaw issues. I found references by LW test pilot Fey, RAF pilot Morrison, and USAAF Test report that the CONSISTENT yaw issue occurred at aft Cg - dominantly with a full aft fuel tank.. in other words Every 262 with that condition at speeds staring at 350mph + and particularly noticable at 400. All on the Xeno website you posted earlier.

 

[Soren]

Wrong on "the shockwave at the trailing edge of the horizontal stabilizer"

A shockwave at the trailing edge only occurs when the ac is 100% supersonic in which case there would also be a shockwave at the leading edge.

You're right, I meant to say the leading edge as I've done in all the posts up to that one, I spun things around, that's what happens when you forget your morning coffee I guess..

 

[Soren]

Soren, more than likely it would not tear the aircraft apart. The pilot would have to lower the airspeed but he could fly the plane home and land. But what do I know? I am only trained and qualified to work on structures...

All you are doing speculating and making up your own facts and truth.

That is okay though, the forum is used to it after all these years.

Great, a mod openly patronizing a member

 

[Soren]

BTW - with reference to yaw issues. I found references by LW test pilot Fey, RAF pilot Morrison, and USAAF Test report that the CONSISTENT yaw issue occurred at aft Cg - dominantly with a full aft fuel tank.. in other words Every 262 with that condition at speeds staring at 350mph + and particularly noticable at 400. All on the Xeno website you posted earlier.

I'd like to see these references plz. According to Fey only 1/3 of the a/c he flight tested for service approval exhibited any yaw issues, so what you're saying doesn't make any sense.

 

[kool kitty89]

Soren I never claimed that the the wing-body design of the Me 262 was bad, I just stated that a proper configuration would be needed to keep the stibilizer from being blanked.

And I was talking about stick forces at/above the Me 262's Mcrit. If control was lost because the stick went stiff (for pitch, not roll), that was a GOOD sign in terms of the design, as it would mean that the elevator would still work if sufficient force was applied. (either with trim tab adjustment or if boosted controls had been added, as with the transsonic a/c I mentioned -particularly the F-86, and in the case of the P-38 which could recover from terminal dives using the trim tab)



Bill, would the shock wave at the stabilizer its self (when the critical mach number of the tailplane had been exceeded) result in stiffening controls, or "loose" ones. (the latter implying the elevator was "blanked")


Also, you didn't answer my questions about swept wings, I was asking what the data for the (root and tip) airfoil sections refers to. Are the figures for the wing measured in "straight" configuration, or are they taking the sweep into account. (the comment about Delta wings was that this would not be an issue in their case)

I had thought it was the former case (of the unswept section) but The Incomplete Guide to Airfoil Usage gives the airfoil for the Sabre as 9.5% root, and 8.5% at the tip. But this page North American XP-86 Sabre says that an 11% root and 10% tip were used. (which would apear that latter may be taking sweep into account)

 

[Soren]

Lindner and others are very explicit regarding the enormous stick forces required (50kg at .86) as the 262 progressed from .82 Mach. He specifically notes his struggle with both hands on stick trying to prevent the nose down tuck until he was able to free one hand to retard the throttles - and survive.

That I haven't heard before Bill, and it puzzles me abit as Fey makes it clear that the control forces are light at all speeds. Also I've never heard of heavy stick forces in the Me-262 before, could you show me the report by Lindner ?

 

[kool kitty89]

Then how was elevator control lost at .84+ mach Soren?

Good control forces up to the problematic speed range would be conceivable, but at critical mach I don't think you'd expect to have light controls. (inless the tail was emersed in turbulence like the P-47 aparently was at critical mach with the elevator being somewhat slack, but useless)

 

[Soren]

You are a self proclaimed expert at ballistics are you not?

Test me Bill, I think I know pretty much all their is to know about the subject.

The physics works perfectly for bullets travelling faster than sound.

Pretty true, although there are variances.

 

[delcyros]

A lot of discussion here.

I would like to quote two sentences from the spiegel magazine, which interviewed Ing. Jan Horn and Ludwig Bölkow from Messerschmidt, both claimed:

Ludwig Bölkow:"Wir flogen örtlichen Überschall",
Jan Horn: " Nach meiner Kenntnis sind etwa vier bis sechs Schallmauerd
urchbrüche" gelungen.

Note that no further, reinforcing data is presented. Both claims were raised in relation with Mutkes claim. It is likely that most of J. Horn claims refer to fatal dives which eventaully succeeded in breaking the speed of sound but failed coming back, e.g. returning to safe flight condition.

It should be quite interesting that Mano Ziegler also raised a claim for Heini Dittmar to have broken the sound barrier while making a full power dive in a Me-163B. Ziegler claims that on July 6, 1944, Heini Dittmar flying a pre-production comet Me 163BV18 VA + SP was measured travelling at a speed of 1,130 km/h measured with ground instruments, bangs heard clearly on the ground (Würzburg track).

I don´t have the technical background knowledge necessary to get involved in the discussion and so far I can only give a personal opinion to the topic:
With the present set of aviable records and despite Prof. Otto Wagners 1999 paper which approved a possibility (which by then was something new), Mutke´s claim cannot pass critical examination in a way to positively verify the event from a historical perspective, let alone a technical investigation.

 

[Soren]

Then how was elevator control lost at .84+ mach Soren?

Mach 0.86, because of turbulent airflow over the control surfaces of the tailplane cause by the shockwave forming at the LE, like I said very early on in this discussion to Bill:

"I don't believe the entire 'horizontal stabilizer' was immersed in turbulent flow Bill, the elevators might have been because of the shockwave produced at the LE of the stabilizer, but not the entire stabilizer. So like Muthke one could trim the a/c out of the dive by utilizing the fully movable horizontal stabilizer, which is what he did."

 

[HoHun]

Hi Delcyros,

>I would like to quote two sentences from the spiegel magazine, which interviewed Ing. Jan Horn and Ludwig Bölkow from Messerschmidt, both claimed:

Do you happen to know the exact issue the article was in? I think it was not a real interview feature, but just some quotes in the text of a journalist's article. (At least, if it's the same article I've read a couple of years back.)

Thanks in advance!

Henning (HoHun)

 

[drgondog]

Test me Bill, I think I know pretty much all their is to know about the subject.

Then why did you miss that little point about supersonic shock waves?

Pretty true, although there are variances.

Your example might be? It is exactly true - not pretty true.

 

[Soren]

Then why did you miss that little point about supersonic shock waves?

I didn't, read my post. Infact read my last post.

Your example might be? It is exactly true - not pretty true.

Normal spitzer at 2,200 fps, large shockwave at the tip AND near the back.

Same with a/c, shockwaves form both at the LE AND the TE in supersonic flight.

However a variance occurs when changes in shape occur along the object, you didn't note that.

 

[drgondog]

Mach 0.86, because of turbulent airflow over the control surfaces of the tailplane cause by the shockwave forming at the LE, like I said very early on in this discussion to Bill:

"I don't believe the entire 'horizontal stabilizer' was immersed in turbulent flow Bill, the elevators might have been because of the shockwave produced at the LE of the stabilizer, but not the entire stabilizer. So like Muthke one could trim the a/c out of the dive by utilizing the fully movable horizontal stabilizer, which is what he did."

LOL - go back to my earlier reply to your 'trailing edge shock wave boo boo' reply where you can't doctor your quote - you said TRAILING EDGE Soren.

Theoretically, if the sweep angle was less and the airfoil thickness greater on the horizontal stabilizer - supersonic flow and SUBSEQUENT shock wave at the leading edge could occur. What was the 262 tail geometry and airfoil?

But a.) the tail has to go supersonic at or below .86 for the shockwave to exist at .86, and b.) because the slab tail was there it would be very effective even at supersonic speeds.

So, to emphasize some points.
1. I don't believe the nose over an the attendant control stiffness was cause by the the elevator being blanked nor do I believe the elevator went supersonic well below Mach 1.
2. I do believe the pitch down was caused by the transonic shock wave forming in the .82-.86 range, thereby moving the ac back from .25 to ~.5 chord point. I don't know if the ac center had moved all the way to .5 chord at .86.
3. As a result of the aft movement of ac, the CMac changed from close to neutral to a decided and progressive nose down pitch about the lateral axis of the airplane, requiring increasing 'Up' elevator to compensate for nose down pitch forces.
4. I believe further that the increasing stick force required to offset the increasing CMac due to increased airspeed was a direct result of the required elevator forces on the airframe to try to move the nose back up. This is my biggest area of doubt regarding 262 capability to reach Mach 1 with all the parts wired together.
5. The question remaining about all this is twofold.

One - did Mutke not have enough strength to continue retarding the nose down pitch forces and the 262 continued to a stable point (i.e. vertical) despite all he could do? Or did Mutke intentionally go vertical and immediately pull the throttles when he had a free hand, then as the 262 slowed down to below .82, was he then able to avoid another 'pitch down moment' in the transition....

and BTW as the 262 transitioned from >.86 M to the pre shock wave migration velocity then his huge aft stick force to hold attitude suddenly goes away and the 262 would quickly require a push forward to prevent a too rapid pull up.

If he actually did achieve Mach 1 he is the luckiest SOB that ever flew an airplane to survive.

I go with the former scenario..and the latter 'luck' condition - and still do not believe it happened.

 

[Soren]

LOL - go back to my earlier reply to your 'trailing edge shock wave boo boo' reply where you can't doctor your quote - you said TRAILING EDGE Soren.

Doctor ???! I took it straight from the post man! 10-14-2008, 11:32 PM, Post #84.

I accidently confused it around in the post where I said it was at the trailing edge in the transonic region when I should've written leading edge, I already mentioned that one page back in reply to your response to it, go back and read it yourself.

 

[drgondog]

I didn't, read my post. Infact read my last post.

The last post cleverly corrected the original post 198 - see below

Normal spitzer at 2,200 fps, large shockwave at the tip AND near the back.

Same with a/c, shockwaves form both at the LE AND the TE in supersonic flight.

LOL-You have a charming capability of parroting the comment blowing away your thesis - and claiming it as your own
.

This is your direct quote from post 198 to KK

KK,

The Me-262's horizontal stabilizer isn't emersed in turbulent flow, that's the reason it is placed so high, to keep that from happening. The thing that is causing the elevator trim tabs not to work is the shockwave forming near the rear of the horizontal stabilizer, causing turbulent flow over the control surfaces, the elevator trim tabs, rendering them ineffective. That is why the all moving tail plane works and the elevator trim tabs don't.

The Me-262's stick never froze or became stiff, the control forces remained light throughout the speed range.

 

[Soren]

Bill,

Before you turn nasty childish once more read post #205.

You that's the problem with you Bill, you make one mistake, be it a typo or accidental swap around, you emmidiately jump in calling one a liar. You don't understand simple mistakes. And furthermore, and this is what usually makes debating with you a very unfriendly and childish affair, you have a nasty and a bit disturbing habbit of bringing in previous and completely unrelated debates to strenghten your own argument by trying to either ridicule your opposition or induce doubt as to his credibility.

You just don't know what an honest mistake is.