The sound barrier
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Sorry I think I'm getting confused. Fair enough, anyone can make a mistake and say or type the wrong word, but, as quoted above, didn't you then go on to describe exactly which bit of the tail you meant (control surface and trim tabs, which are at the rear)? How can you do that by mistake?
Waynos,
There's nothing untrue about the shockwave rendering the rear control surfaces ineffective (The very reason for the all moving tail plane), it's the placement of the shockwave which is at the LE in the transonic region (Like I've said earlier), and NOT the trailing edge as I mistakenly wrote.
But if I wasn't aware of this (As Bill oddly seems to suggest) then why did I make it clear earlier, seriously ?
I made a swap around, a mistake, that's it.
There's nothing untrue about the shockwave rendering the rear control surfaces ineffective (The very reason for the all moving tail plane), it's the placement of the shockwave which is at the LE in the transonic region (Like I've said earlier), and NOT the trailing edge as I mistakenly wrote.
But if I wasn't aware of this (As Bill oddly seems to suggest) then why did I make it clear earlier, seriously ?
I made a swap around, a mistake, that's it.
kool kitty89
Senior Master Sergeant
Sore, what I was asking was what the charaterisics of the stick forces were at critical mach. As I understand it, elevator control loss comes in 2 possible forms 1: excessve control forces, 2: being blanked by turbulence with controls still movable.
Which is the case for the Me 262? (if it's the former, boosted controls would allow the elevator to work as it did in the F-86 -granted the F-86's tailplane had a higher Mach number as well)
And you never answered my question from post #195.
That's very interesting on the Me 163 Delcyros. I would think that the thick root section (14% -not sure about sweep-) would be too thick, not to mention the wooden wing construction. (not to mention the trim problems of tailless aircraft in the transsonic regionand possible issues with the LE slots at such speeds) Besides the much breater thrust available at these speeds, I think the Me 163 would be less likely sucessfully perfrom this feat than the Me 262.
Bill, Data for the Me 262's tailplane airfoil would be interesting, but I immagine that's going to be difficult to find. (also not there was no sweepback to the tailplane, it just had LE taper, there was a ~20 degree swept-back version used on the HG I/II though)
And again: Bill, could you clarify my question on swept wing airfoils. see post #208
Which is the case for the Me 262? (if it's the former, boosted controls would allow the elevator to work as it did in the F-86 -granted the F-86's tailplane had a higher Mach number as well)
And you never answered my question from post #195.
That's very interesting on the Me 163 Delcyros. I would think that the thick root section (14% -not sure about sweep-) would be too thick, not to mention the wooden wing construction. (not to mention the trim problems of tailless aircraft in the transsonic regionand possible issues with the LE slots at such speeds) Besides the much breater thrust available at these speeds, I think the Me 163 would be less likely sucessfully perfrom this feat than the Me 262.
Bill, Data for the Me 262's tailplane airfoil would be interesting, but I immagine that's going to be difficult to find. (also not there was no sweepback to the tailplane, it just had LE taper, there was a ~20 degree swept-back version used on the HG I/II though)
And again: Bill, could you clarify my question on swept wing airfoils. see post #208
drgondog
Major
Re: snaking and dutch roll? Go back to your post which has the link to the Me 262 POH. There is the POH Handbook compiled by USAAF from the flight tests and German intelligence debriefings post war with persons such as Lindner and Fey - LW and Morrison - RAF
1. Then wander into Stormbird Rising
Appendix C, page 197-198, and go to section 3. Flight Characteristics, par e. "The handling characteristics were poor at all speed above 350 mph. The airpland would not make a very good gun platform because of a tendency to hunt directionally in snaking at speeds above 400mph"
The above is from the series of tests performed on USAAF inventory numbers T-2-711 (wn111711) and T-2-4012 (no given wn) in February 1947 and reported in F-TR-1133-ND
2. Appendix B, RAF Interrogation Report of Gerd Lindner, and later verified by Karl Baur before the 1947 Flight Tests at Wright Pat.
page 194
Aircraft Performance and Flying Qualities "12. Maximum altitude from ZLindner was 12,400 metres. Maximum speed ever attained with the Me 262 was 1004 Kmh at 4300 metres, the angle of flight being between 20 and 25 degrees"
Behavior in a High Mach number dive "35. Lindner stated that the Machmeter was not successful; He said the experiments with high speed were made with 70 altimeters mounted in the fuselage and photographed automatically every 1/2 second. These altimeters were connected to chordwise holes in each mainplane. The true airspeed indicator would be checked by flying between two tall chimneys. The interpolation, after a test flight, of all the altimeter readings, and those of the TAS indicator, enabled an accurate determination to be made of the mach number attained in the flight."
"38. Lindner stated that he climbed to 8000 metres and dived at an angle of 20-25 degrees where mach number 0.86 was reached. He reached 1000 kmh TAS (as read on the TAS indicator), giving he said a corrected mach number of 0.86. At Mach 0.83 the nose started to drop, and he had to pull the stick with a force of 15kg with both hands. As the Mach number increased, a violent buffeting set in, appearing to come from the canopy behind his head and producing a very high frequency banging noise. The aircraft became more nose heavy, and at mach 0.86 he was pulling with a force of 40-50 kg.
"40. On the strength of these tests the service pilots were instructed to not exceed a 'true airspeed indicator" reading of 950 pmh and were advised to set the trimmer so that a slight push was required to initate the dive. They were also told to not use the trimmer for recovery. Several fatal accidents have occurred in the Luftwaffe which Lindner attributed to pilots exceeding this speed limit, and being unable to pull out using both hands - the forces being so great that they could not get one hand from the stick to the trimmer."
"46. Elevators. The first few Me 262s were fitted with fabric covered elevators. At speeds between 850-920 TAS (indicator) at about 1000/2000 meters, ballooning of the fabric occurred. This could result in the aircraft showing a tendency to nose further in the dive. Sometimes the fabric would burst; this had occurred five tmes and in each case the aircraft had landed safely; recovery from the dive being effected by means of the adjustable tailplane. The fabric was replaced by metal."
The last point by Lindner should put a few of the proposed transonic questions to rest.
1.The ballooning effect should cause probable flow separation over the elevators, reducing the overall effectiveness of the elevator - but demonstrating the slab tail was still effective at very hign speeds near transonic.
2. The nose down effect was a direct consequence, pre-shockwave, was a consequence of losing some horizontal stabilizer effectiveness - not the next issue of transonic flow causing a huge increase of CMac.
Any other references other than the link you provided plus the above.
Now - where are YOUR references?
It's nr.2 KK, the elevator trim tabs are still movable but emersed in turbulence thus ineffective. But like I've been saying from the beginning not the whole horizontal stabilizer is emersed in turbulent airflow, only the rearest part where the control surfaces are located, and again because of the shockwave forming at the LE of the stabilizer fin. So trimming the taiplane will work. Thus the only way to change pitch attitude in transonic flight is to trim the tail plane, like Mutke did.
If it were option nr.1 you'd read it in the a/c manual as the control forces will increase gradually along the speed range, but no such thing is mentioned. What is said is that the controls remain light throughout the speed range, even at very high speed. As a matter of fact I've never heard or read about high stick forces in the Me-262, from all that I have read about the a/c the controls were light and well harmonized at all speeds.
If it were option nr.1 you'd read it in the a/c manual as the control forces will increase gradually along the speed range, but no such thing is mentioned. What is said is that the controls remain light throughout the speed range, even at very high speed. As a matter of fact I've never heard or read about high stick forces in the Me-262, from all that I have read about the a/c the controls were light and well harmonized at all speeds.
drgondog
Major
KK- the freestream only 'sees' the LE angle, but the normal and tangential velocities are reduced to the 1/4 chord. The 163 had a clear sweepback increase over the 262 and even with a higher (but not much higher) increase to t/c should delay transonic region to a higher freestream Mach number.
Bill,
Here are MY sources:
Go here: http://www.zenoswarbirdvideos.com/Images/Me262/ME262PILOTDEBRIEF.pdf
Read under flying characteristics, from Me-262 test pilot Hans Fey:
"There is no flutter while diving. Fay conjectures the reason for this to be the high position of the horizontal stabilizer in relation to airflow around the wings.
Around one third of the airplanes tested by Fay had a slight tendency to skid during their first flights. This was easily eliminated by adjusting the trim tab on the rudder"
Now read this, the Allied POH for the Me-262 prepared by Allied test pilots:
http://www.zenoswarbirdvideos.com/Images/Me262/262PilotHandbook.pdf
Again under flying characteristics, surprise surprise, similar conclusions, great flying characteristics, no flutter in dives, utilizing the tail plane trim is too effective. Btw note the German air speed indicator lists TAS.
No where, I repeat no where do I see anything about poor handling! Infact I find quite the contrary, the handling of the a/c is praised by all who flew it!
Here are MY sources:
Go here: http://www.zenoswarbirdvideos.com/Images/Me262/ME262PILOTDEBRIEF.pdf
Read under flying characteristics, from Me-262 test pilot Hans Fey:
"There is no flutter while diving. Fay conjectures the reason for this to be the high position of the horizontal stabilizer in relation to airflow around the wings.
Around one third of the airplanes tested by Fay had a slight tendency to skid during their first flights. This was easily eliminated by adjusting the trim tab on the rudder"
Now read this, the Allied POH for the Me-262 prepared by Allied test pilots:
http://www.zenoswarbirdvideos.com/Images/Me262/262PilotHandbook.pdf
Again under flying characteristics, surprise surprise, similar conclusions, great flying characteristics, no flutter in dives, utilizing the tail plane trim is too effective. Btw note the German air speed indicator lists TAS.
No where, I repeat no where do I see anything about poor handling! Infact I find quite the contrary, the handling of the a/c is praised by all who flew it!
kool kitty89
Senior Master Sergeant
Bill, 14% compared to 11% thickness is a pretty big difference, not to mention the airfoil characreristics were different. (with max chamber of 18% chord located at 25% chord) I don't know what the thickness is with sweep taken into account though.
I don't think I fully understan the properties of swept wing though. I know of the increase in chord, the (detrimental) spanwise flow, and the advantages in the supersonic. (keeping the wings behind the shock wave) And than in the transsonic region the sweep reduces wave drag by "sweeping" the shockwaves developing on the wing. Does the spanwise flow its self increase critical mach number? (I'm going to look for some articles on it)
Would the rather high degree of LE taper on the P-80 and Vampire contribute to higher critical Mach numbers?
Soren, the Wright Field manual makes similar comment about good stability and lack of elevator flutter at high speeds. (noted to be likely a result of the tail position)
Again referring to the Mcrit characteristics of the rudder, I may be mistaken, but I think the shockwave developed at the tailplane (when it's Mcrit is exceeded) could result in either of the 2 possible loss of control problems I mentioned. (loose stick-blanked elevator, or immovable due to exteme control forces) The "blanking" problem can also result from wing turbulence as previouslt mentioned, but that's not the issue here.
I don't think I fully understan the properties of swept wing though. I know of the increase in chord, the (detrimental) spanwise flow, and the advantages in the supersonic. (keeping the wings behind the shock wave) And than in the transsonic region the sweep reduces wave drag by "sweeping" the shockwaves developing on the wing. Does the spanwise flow its self increase critical mach number? (I'm going to look for some articles on it)
Would the rather high degree of LE taper on the P-80 and Vampire contribute to higher critical Mach numbers?
Soren, the Wright Field manual makes similar comment about good stability and lack of elevator flutter at high speeds. (noted to be likely a result of the tail position)
Again referring to the Mcrit characteristics of the rudder, I may be mistaken, but I think the shockwave developed at the tailplane (when it's Mcrit is exceeded) could result in either of the 2 possible loss of control problems I mentioned. (loose stick-blanked elevator, or immovable due to exteme control forces) The "blanking" problem can also result from wing turbulence as previouslt mentioned, but that's not the issue here.
drgondog
Major
BS ALERT. You still beathe your own air and dismiss the top two test pilots at Messerscmidt - Lindner and Baur who directly contradict what you are saying. I just laboriously recapitulated the interview and the source. What sources do YOU have discussing 'light stick forces between .80 and .86 Mach?
drgondog
Major
You have a disturbing tendency to leap at sunshine and avoid the dark.
If Lindners debriefing, verified by Baur is BS - PROVE IT! They forgot more than you will ever know and their testimony and verification directly contradict what you say..
kool kitty89
Senior Master Sergeant
Ok, I think I understand the swept wing issue. (increased chord asside) Due to the sweep, the speed of the airflow over the wing is lower than it would be with a similar straight wing. It doesn't have anything to do with spanwise flow OVER the wing (and this doesn't even really occur at high speed and low AoA) but the airflow being spit with some flowing outward along the wing LE and the rest flowing over the wing. Thus the Mach number of the air flow experienced by the wing will be lower than that of the freestreem.
So a straight wing of 9% chord will have a lower critical mach number than a 35 degree swept wing of 11% chord of similar airfoil type. (despite the true chord length of both wings being the same)
Also, the Komet apears to have a LE sweep of ~26 degrees. (the P-80 has one of ~12-15 degrees, though at the root it apears to be greater than 20 degrees. The vampire looks like ~15-18 degrees)
Additionally the Me 262's wing its self, while having a LE sweep of 18.5 degrees, only seems to have been swept back (outboard of the nacelles) ~11 degrees, to the change in actual thickness would be only ~2%. And this section is of 11% (at 40% chord) tapering to 9%.
Also the LE sweep of the tailplane is ~25 degrees and the fin's is ~45 degrees.
However, I still don't know if the airfoil data for swept wing a/c is from a "head on" (unswept) perspective or if it's a measure of the true swept wing. (if it's the former, the 11% chord refrence to the F-86 would be in error)
So a straight wing of 9% chord will have a lower critical mach number than a 35 degree swept wing of 11% chord of similar airfoil type. (despite the true chord length of both wings being the same)
Also, the Komet apears to have a LE sweep of ~26 degrees. (the P-80 has one of ~12-15 degrees, though at the root it apears to be greater than 20 degrees. The vampire looks like ~15-18 degrees)
Additionally the Me 262's wing its self, while having a LE sweep of 18.5 degrees, only seems to have been swept back (outboard of the nacelles) ~11 degrees, to the change in actual thickness would be only ~2%. And this section is of 11% (at 40% chord) tapering to 9%.
Also the LE sweep of the tailplane is ~25 degrees and the fin's is ~45 degrees.
However, I still don't know if the airfoil data for swept wing a/c is from a "head on" (unswept) perspective or if it's a measure of the true swept wing. (if it's the former, the 11% chord refrence to the F-86 would be in error)
claidemore
Senior Airman
Fay never flew any of his test planes higher that 13000 feet, and did not push them to the limit of dive speed, only enough to pass acceptance tests. When he speaks of no flutter while diving, he is not talking about Mach .84 or .86, but of speeds in the 600mph or less range. His job was to make sure the plane could make minimum speeds for acceptance, not to test their max performance.
And that report is a second hand summarization, written by an interrogator/interviewer, not by Fay himself.
In no way can it be compared to an actual test report.
And that report is a second hand summarization, written by an interrogator/interviewer, not by Fay himself.
In no way can it be compared to an actual test report.
Give me a link to Lindners debriefing and Baur's verification Bill cause I can't find it.
No to reverse what you just said, are you saying that what LW test pilots Fritz Wendel Hans Fey as-well as the Allied test pilots are saying is BS ??
I have to concur with Claidmore, nothing in that interview with Fey ever mentions transonic speeds, only general acceptance trials. Indeed the words 'transonic' and mach do not even appear in the document (a quick ctrl F will demonstrate that). It even states that as long qas the plane could attain 510mph it was was passed as OK and that on several occasions Fey found himself parting company with parts of the plane, which all seems to support the opposite view.
drgondog
Major
The "link" I provided for the above quotes are extracted verbatim from the book Stormbirds Rising by Hugh Morgan and published by Osprey in 1994. I believe I noted that before launching into the entire series of quotes.
The section in the POH handbook from the link YOU provided is found on page 7 Section 2 - Pilot Operating Instructions, para c. "Center of Gravity" and para d. Take Off Weights and Balances.
You apparently missed this section. In case you don't know what to look for I recommend you pay particular attention to the instructions to not put fuel in the rear tank and also the explanation of the behavior when the afte cg exceeds 30% MAC. You will find reference to both the yaw and stall issues when that restriction is ignored.
http://www.zenoswarbirdvideos.com/Im...otHandbook.pdf
If you will search diligently you will also see that I never claimed that the 262 had flutter problems. In fact the only reference I ever saw relating to harmonic issues at all was Lindners reporting of "severe buffeting and high frequency banging noise". I assumed from this description that he was experiencing the first real separation (and severe turbulence aft of cockpit) of flow from both the wings and fuselage - not flutter.
Flutter would have been transmitted to his stick and the description should be different.
Now - since we are quoting from Wendel, take a look at the report by Kapitan Fritz Wendel in your link
Flying the Messerschmitt Me-262
Go to page 4, sections 7 and 8 and take a glance at the warning for aft cg as well as rigging for further reference to yaw issues. I recognize that similar issues and warnings surrounded a Mustang when the aft fuse tank was loaded... but these instructions apply to EVERY Me 262 - not just a few with "QC/QA" issues and poor quality... as similar instructions applied to 51 drivers for normal operations in which the tank had to be filled
Are we about 'done' with snaking?
We still have a question about the issue at high speed as it was seemingly encountered in the two tested after the war and brought to the US. Based on all the data, I suspect further that the problem experienced by the US test flights might have been related to the rigging issue discussed by Wendel.
drgondog
Major
It gets a little tricky here. First, the sweepback angle relative to airplane axes is in fact referenced to the LE. A 35degree sweep wing is 35 degrees from the perpendicular to the CL and 125 degrees from CL
For an untapered wing of very high AR (approximating 2-D) the airflow component is in fact Vfs*COS(Sweep LE) and the airfoil profile perpendicular to the LE is in fact the areodynamic profile for that flow.
Real world for a tapered wing is that for a close approximation of design to reality you assume the normal flow is perpendicular to the 1/2 chord.
Now it gets trickier going from aero design to the shop floor. Frequently the structural ribs hanging off the spar will be perpendicular to the main spar but they may also be designed parallel to fuselage.
Obviously the rib for a 'parallel' design will be the 'true 'aerodynamic profile reconstructed at an angle from the spar. So the lines group gets involved to ensure the manufactured rib running parallel to the airframe which creates the airfoil surface of the skin, when cut perpendicular to the spar, results in an airfoil section which is what the areos specified.
claidemore
Senior Airman
You need to re-read the report Soren. Every a/c had to pass a 950kmh 30 degree dive test.
Fay said that speeds in the 1000 to 1050 range were 'spoken of' as the absolute maximum. He also said that if the dive speed only reached 900 kmh, the plane was passed anyways.
Great, a mod openly patronizing a member
No, only pointing out the truth. The forum (not just mods) has known this for quite some time.
