Aces High Bulletin Board
General Forums => Aircraft and Vehicles => Topic started by: Gaston on April 27, 2009, 06:30:34 AM
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Hello everyone.
This is a quote from the recently posted 1990 comparative flight tests done by an association of test pilots;
"Corner speeds were all VERY CLOSE to the maximum level flight speed, implying rapid energy loss when turning at the structural limit."
This is the exact passage that made me think that the P-51D with metal elevators had its peak turn rate at around 400 MPH, a claim that Hightech said was "just insane".
While I do agree a peak turn rate so high is not logical and wrong, and that I compounded this error by misreading/misremembering a 450 yards turn radius at 400 MPH TAS as 450 ft., the above quote does make me wonder just how close to the maximum level speed is the widely accepted 270 MPH TAS corner speed for the P-51D...
It doesn't seem very close at all. These were tests done by a several professional test pilots, with modern instruments, up to about 6 Gs.
I'm not claiming my previous statements on this issue were correct, but since they were based on the above, I think some clarification is needed on the words "very close", which I approximately quoted, in a toned-down form even, while citing these 1990 tests...
Maximum level speed for a P-51D pulling 67" at 10 000 ft. is not too far from 400 MPH TAS, perhaps 385 or so...
At the very least some explanation is needed here...
Gaston.
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[Aussie Joker] And here... we... ...GO![/Aussie Joker]
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While I do agree a peak turn rate so high is not logical and wrong, and that I compounded this error by misreading/misremembering a 450 yards turn radius at 400 MPH TAS as 450 ft., the above quote does make me wonder just how close to the maximum level speed is the widely accepted 270 MPH TAS corner speed for the P-51D...
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I'd expect the corner speed to be IAS not TAS. If you go high enough, 270 mph IAS will become 400 mph TAS.
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Doesn't corner speed always go up with airspeed? Especially with older birds, where there is no way to retain the energy needed to maintain the best corner speed in a flat turn.
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No to both...
No, the test specifies an altitude of 10 000 ft., so even 270 IAS would be about 315-320 MPH TAS... This is still a LONG way from the max. level speed at 67" for a P-51D...
No, "corner speed" is a SPECIFIC speed, usually the lowest speed at which the maximum G can be maintained for a continuous period of time of several seconds (which should equal the minimum radius of turn for a 180°), that is, not a split-second "bump" in Gs.
"Very close" is odd, and does suggest 350-370 MPH TAS at least... (290-310 IAS at 10 000 ft. roughly)
My working theory right now is that to save strain on these old airframes, they truncated the turn test to a 90° turn, and extrapolated the rest of the turn from there...
The problem with doing that is that at increasing speeds, most American WWII fighters respond more crisply with less "mushing" or "lag-time" to the elevator response in the early part of the turn, and this skews the perception of the turning response as getting ever heavier but better as speed goes up. They loose the "mushing", but don't necessarily continue tighter than at a lower speed...
Actual combat reports (I am about to finish reading the entire supply of P-47/P-51 combat reports from the "WWII aircraft performance" site...) do indicate a better turn rate for the Mustang at higher speeds versus both german fighters (less so for the 109), but not really the high rate of speed loss that is implied in these 1990 tests. At lower speeds the P-47 and P-51 do more than hold their own in prolonged turning, often on the deck, with the only exception being against the FW-190 (the only time the sentence "I was out-turned" [at similar speed] will appear on an U.S. pilot's typewriter is against the 190...).
Another bit of trivia; Against a Me-109G-6 with underwing gunpods, the P-47 will OUT-spiral climb it to the left, gaining 180° in four consecutive 360° climbing turns, ending it in a victory at 140 MPH IAS at 5000 ft.. (Mc Dermott, May 25 1944.) Contrary to my previous thread title, the 109 does do much better to the right against the p-47, being roughly equal...
Out-spiral climbing 109s I have yet to hear the P-51 do, strangely enough...
In any case these 1990 tests do seem odd, and I have heard of at least two veterans being puzzled by them...
Gaston.
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The question is, what power settings were used? Normal Power? MIL power? Combat Power?
I wouldn't be surprised that Normal Power was used. After all, who would volunteer their Warbird to be flown at Combat Power for the sake of an unimportant test?
My regards,
Widewing
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http://www.wwiiaircraftperformance.org/p-47/er/78-mcdermott-25may44.jpg
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In point of fact, corner velocity is the lowest speed at which the maximum allowable Gs can be pulled. It has nothing at all to do with "sustaining" the Gs. WWII prop fighters did not have enough thrust to sustain a max-G turn without descending, nor did the Korean or AFAIK Vietnam era jet fighters.
How can we find the minimum airspeed needed to pull max-Gs? The speed at which an airplane will stall under a specific G-load is the accelerated stall speed. The accelerated stall speed of an airplane in a given configuration can be derived by multiplying the 1g stall speed by the square root of the number of Gs.
For instance, take an airplane with known to stall in clean configuration at 100mph IAS, and which is structurally limited to 8gs. The square root of 8 being 2.83, that means the accelerated stall speed for that aircraft *will* be 283 mph IAS, in *clean* configuration. However, the corner speed for the P-51 is usually quoted not in clean configuration, but with one notch of flaps deployed, which will increase lift and lower corner velocity somewhat to...around the same 270mph IAS that has been known for 60 some odd years. Rather anticlimactic outcome, aye?
Pilot resistance to G-forces plays a heavy role in air combat, especially without G-suits, so just for sh*ts and giggles we'll work out the 6g accelerated stall speed, which turns out to be 245 mph IAS.
For further sh*ts and giggles, let us say that the airplane is at a higher gross weight than the, I don't know, 9,611 lbs. usually quoted in performance reports for this aircraft. Let us say that it is loaded heavily enough to raise the 1g stall speed to 105 mph. Through the "magic" of physics and mathematics, we find that the 8g accelerated stall speed of the aircraft has now become 297mph IAS. In fact, lets do calculate for 6 and 4 gs using this heavier weight:
8g accelerated stall-297mph IAS
6g accelerated stall-257mph IAS
4g accelerated stall-210mph IAS
For additional sh*ts and giggles, we will look at an airplane known to stall in clean configuration at 127mph IAS:
8g accelerated stall-359mph IAS
6g accelerated stall-311mph IAS
4g accelerated stall-254mph IAS
Now note, these figures are not even close. In fact, the former aircraft has 8gs of lift available at a speed lower than than the 6g stall speed of the latter aircraft! These figures make it very likely that any "out-turning" of the former on the part of the latter has alot to do with the geometry of ACM and skilled piloting and little to do with any putative turn advantage for the vastly heavier-loaded aircraft. Sustained turn radius is so closely tied to an airplane's loading/minimum flying speed that the latter aircraft simply could not sustain a tighter radius speed for speed, and for the much heaver loaded aircraft to have an advantage in sustained turn rate would require a vast advantage in thrust which simply does not exist when comparing the two aircraft in question.
However, a Fw-190 at 300mph IAS will easily avoid/turn-inside a P-51 piloted by someone who has been taught to "keep it fast" and is chugling along at 400mph IAS, a fact which I suppose is lost on those unfamiliar with even the basic practicalities of ACM. :devil More is the pity, could save a lot typing if this were not the case.
Oh and Gaston, there is no mechanism in the real world for the aerodynamic forces of a deflected elevator to be "delayed", and if you have discovered one, you're the first since Kittyhawk to do so. Here is something for you to do with your time than posting to this forum: Get a library card. Check out a book on basic aerodynamics. Even the very basic stuff they teach you in ground school for a private pilot ticket would illuminate you in regards to how airfoils work, critical AoA, accelerated stall, and the formula for deriving accelerated stall speed.
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http://www.wwiiaircraftperformance.org/p-47/er/78-mcdermott-25may44.jpg
There is so much that goes into winning even a simple Luftberry in the real world that we don't have in the sim...our "pilots" are not variable in their G-tolerance, nor is it very hard to ride the ragged edge with a stall warning and predictable, easily detectable buffet on your side.
And of course we can expect the Jug to have superior engine performance above 20K.
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Oh and Gaston, there is no mechanism in the real world for the aerodynamic forces of a deflected elevator to be "delayed", and if you have discovered one, you're the first since Kittyhawk to do so. Here is something for you to do with your time than posting to this forum: Get a library card. Check out a book on basic aerodynamics. Even the very basic stuff they teach you in ground school for a private pilot ticket would illuminate you in regards to how airfoils work, critical AoA, accelerated stall, and the formula for deriving accelerated stall speed.
Actually there is a "delay" - this is the time it takes the pilot to actually pull the stick and increase the AOA, especially at high speeds. In AH the delay simulates the stick forces since you cannot make a plastic tabletop joystick to produce forces. And the library card lecture was not very polite.
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I wouldn't be surprised that Normal Power was used. After all, who would volunteer their Warbird to be flown at Combat Power for the sake of an unimportant test?
Not to mention pulling 6 Gs. In another thread, we, with a few exceptions, agreed that the results of that report are highly questionable. So much so as to doubt its ability to be used as a comparitive reference for the characteristics of the tested aircraft.
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Actually there is a "delay" - this is the time it takes the pilot to actually pull the stick and increase the AOA, especially at high speeds. In AH the delay simulates the stick forces since you cannot make a plastic tabletop joystick to produce forces. And the library card lecture was not very polite.
The time to deflect the elevator is not what is meant by delay. The OP theorizes that a given elevator deflection can occur and *not* develop aerodynamic forces for awhile, which is absurd and impossible at speeds below compressability. Politeness is given where politeness is deserved, which is not the case with this incessant inanity.
BTW, if we take the accelerated stall formula and plug in 350mphIAS as the 6g accelerated stall speed, that implies a 1g stall speed of approximately 142 mph IAS. I don't know the exact amount of weight you would have to add to a P-51 to raise its Vs to 142mph IAS (There are some on the forum who can probably calculate it in their heads), but I'm going to hazard a guess that you would have to burden the aircraft to beyond its listed maximum takeoff weight.
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Technically speaking there is a delay. But in the speed ranges we are speaking of, it would be less than 0.1 seconds from 0 AOA to max AOA. Most pilots will not ever match the performance of the plane at those speeds simply because the snatch/sudden onset of g's is not a pleasant experience, think sledge hammer on top of head. I.E. it )(*)&)(& hurts.
Most people would smoothly pull into it in the less than 1 sec range.
HiTech
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No, "corner speed" is a SPECIFIC speed, usually the lowest speed at which the maximum G can be maintained for a continuous period of time of several seconds (which should equal the minimum radius of turn for a 180°), that is, not a split-second "bump" in Gs.
Please Please Please research some basic terms,
Corner speed is the slowest an aircraft can go and still pull it's airframes limit (or pilot limit) of g's given in IAS. There is nothing sustained about it.
So when you make statements like
G can be maintained for a continuous period
It only shows how completely clue less you are.
There are many people here who would love to help expand your knowledge, but you are going to have to start asking questions about things you do not know, and at the very least start learning some basic equations of flight.
I have not checked the math, but I would venture to guess all WWII planes can maintain corner speed at max G until they run out of altitude.
HiTech
HiTech
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Most pilots will not ever match the performance of the plane at those speeds simply because the snatch/sudden onset of g's is not a pleasant experience, think sledge hammer on top of head. I.E. it )(*)&)(& hurts.
Can we model this?
Sounds like a great opportunity to fix the physics-defying e-pilot we have.
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Can we model this?
Sounds like a great opportunity to fix the physics-defying e-pilot we have.
If you'll notice, full deflection of control surfaces takes time, I don't know, looks like a little less than a second to me. I do long for a more punishing red-out model and a "do not move control surfaces so rapidly" lock-up that was easier to trip though.
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Does it really take about a second to go from lock to lock with no airflow over the surfaces?
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If you'll notice, full deflection of control surfaces takes time, I don't know, looks like a little less than a second to me. I do long for a more punishing red-out model and a "do not move control surfaces so rapidly" lock-up that was easier to trip though.
I am more referring the ability of our virtual sierra hotel fighter jock to sustain the massive change in G loads when strapped into defensively oriented Spitfire 16's. ;)
Flip, flop, knock!
SYSTEM: You have banged your head against the canopy and broken your neck trying to evade enemy fire like a n00b. Don't move your controls like a moron.
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Can we model this?
Sounds like a great opportunity to fix the physics-defying e-pilot we have.
It already is , and has been as long as I can remember.
HiTech
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I think it's pretty clear if you read my sentence about corner speed that I know it's not sustained; I said continuous over SECONDS, to distinguish it from a micro-second "bump" in Gs for which the airframes are stressed at; 13 Gs for the P-51, 15 Gs for the 109...
There IS something sustained about it, because otherwise, if that was the ABSOLUTE G limit for ANY lenght of time, there would be no need for 15 Gs airframes now would there?
I added that corner speed is usually equivalent to the smallest unsustained turning radius, but you still have to sustain the Gs for at least 180° to make a radius... Diving in the turn to maintain the "perfect" corner speed and the smallest possible turning radius could be implied, but I said "should" because I wasn't talking about absolute theoretical perfection...
These airframes had to be overstrenght, just like an alpinist rope has to have a breaking strain many times a body's weight, because even a slip or shake can cause 10 Gs for miliseconds, just like wind buffeting or a small pitch-up can cause 10 Gs for periods of time far too short to black-out the pilot, but long enough to cause a crack!
WW II fighters, incidently, were not normally structurally overstressed in turns, but in dive pull-outs above 400 MPH TAS, because the parallel pull of gravity added a lot to the pitch-up instability and the pull-out strain...
This reminds me of a gruesome anecdote I heard of a North American engineer visiting front-line units. A pilot told him; "the wings are breaking off in the dive pull-out", to which the engineer, knowing about the Mustang's 13 Gs rating, confidently replied; "Impossible, you cannot exert that much force on the airframe at the required speed; we tested it." The pilot describes what happened next; "He had not finished speaking his words that we heard the familiar clap-boom of a p-51B's breaking its wings, the clap being the wings breaking, the boom being the fuselage burying itself 10 ft. into the ground. We turned in time to see two fluttering Mustang wings, the fuselage and pilot having long since dived into the ground. "What was that?" he said. "It just happened again" I said..."
So trained engineers who had designed, tested and calculated the stresses on the P-51 for YEARS did not know everything about their creation... So much for "calculated" figures...
On the delayed response issue, there is the time for the pilot to pull the required force (as pointed out); this is what I call the pilot-stick delay, then there is the time for the control suface to overcome the pitch stability; elevator-pitch delay (usually very quick as fighters are designed with low stability), finally there is the pitch-trajectory delay, a critical one because not all aircraft do the same at the same speeds, the Spitfire/FW-190A being great at low speeds, but tending to mush at higher speeds (the Spitfire above 300 MPH did not allow the pilot to pull the top of the stick more than 3/4 inch before mushing. The good thing was that the mush still allowed full 3 axis control.), while the P-47 mushed at lower speeds, and maybe also at higher speeds, without the help of gravity in the "oblique turn trick", to the point Robert Johnson described performing a full roll OPPOSITE to the 190's turn, just to "take out" the mushing that for some reason "disapeared" after a full 360° opposite roll but not before...
This alone shows mushing was a considerable issue, and is mentionned by pilots at all kinds of speeds, except that I think that at 350-400 MPH TAS and above the differences in mushing tendend to "narrow down" among many aircrafts, especially in horizontal turns, but less so in dive pull-outs if the FW-190A is taken as an example...
I don't think "mushing" can be described as being anything other than a delay in turning...
As for the "corner speed very close to the max. level speed", I think since they did stall these aircrafts in turns, and if they found it best to do turns with flaps at, say 310 MPH IAS-370 TAS at 10 000ft., then it could mean we don't know the Mustang as well as we think we do... These were, after all, a bunch of seasoned test pilots with modern instruments... It does corroborate the anecdotal increasing turn disparity with German fighters above 300 MPH TAS. That they didn't go to 8G does raise questions, assuming that the 8 G/270 MPH IAS corner speed was not a "calculated" figure, such things being often unmentionned in 1940's data... (Remember the Noth American engineer's absolute trust in his math?)
The main problem I have with what they are saying is their perhaps jet bias that makes them underestimate the low speed sustained turn rate acceleration below a speed they may have avoided. Also, we don't know what they meant by "very close". Finally, learning the Mustang stall is a fine art, though I wouldn't assume that they didn't know that.
They do however mention using 67" MAP in the test.
Gaston.
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gaston:
So trained engineers who had designed, tested and calculated the stresses on the P-51 for YEARS did not know everything about their creation... So much for "calculated" figures...
I have done dog fights in the p51 along with many others fights in different air plane types. How much time above 6'gs in a plane do you have? So do not even try pull the engineers do not know what pilots do, because it is a nice antidote, but in reality it is not true.
but you still have to sustain the Gs for at least 180° to make a radius..
And once again you show your total lack of understanding of basic concepts,math,physics and simple terms like turn radius.
Radius is just a simple way of describing an arc, no mater how short or long the arc is. If you prefer you could give speed and Degrees per sec to describe a radius. Or would you rather give the degrees of arc and its length to describe the radius.
The concept of Corner speed has nothing to do with sustaining a turn of any length. It is simply as I said, Min speed at which max g's can be pulled. To try read anything more into Corner speed than this definition only shows a complete lack of understanding of basic terms.
I have even flown real planes to find their corner speed. Along with other things like min vertical maneuvering speed.
And the term MUSH is not a stick sensation, it normally refers to reaching the stall edge not departing, so the plane feels like it is sliding more threw the air, so what you are describing is the spits quick response to small stick movements, not its slow response.
HiTech
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Another bit of trivia; Against a Me-109G-6 with underwing gunpods, the P-47 will OUT-spiral climb it to the left, gaining 180° in four consecutive 360° climbing turns, ending it in a victory at 140 MPH IAS at 5000 ft.. (Mc Dermott, May 25 1944.) Contrary to my previous thread title, the 109 does do much better to the right against the p-47, being roughly equal...
Man, you're drawing a long bow on some very tenuous conclusions on this one.
A. The pilot only specified a "109" - nothing about a G-6, nothing about underwing gunpods.
B. No indication of relative energy states - the P-47 had just come down from 20,000 feet, but we have no indication of the relative speed of the "109". It is highly possible that the P-47 traded speed for angles.
C. The P-47 pilot states "after three or four climbing turns". So, what is it? Three? Or four?.
D. How do you know the turns were "consecutive 360 degree turns"? Again, the AAR states 'three or four climbing turns", not three or four climbing circles, or spirals. It is not clear that the aircraft entered a Luftberry until after the P-47 had made its shots (the Luftberry being a primarily defensive move).
E. What is you're evidence that the 109 (which 109 by the way?) is "roughly equal" to the P-47 in a left hand turn?
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I thought the problem with early batches of P51s was the undercarriage extending in pull-outs which made the wing snap? It was simply fixed with an undercarriage lock.
-C+
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The time to deflect the elevator is not what is meant by delay. The OP theorizes that a given elevator deflection can occur and *not* develop aerodynamic forces for awhile, which is absurd and impossible at speeds below compressability.
doesnt seem that absurd, heres a suggested mechanism: deflection of a control surface will change the airflow over the wing, there will be a transition period from one airflow to the other. the transition may introduce more turbulent airflow until it has settled into the deflected state (cause of "mushiness"?). Now factor in the abrupt change of AoA caused by the control surface deflection, again there will be a transition period until the airflow has settled into its new state. during these transitional periods between steady states you might expect more turbulent airflow and consequently a temporary drop in Cl. Could this be the cause of the perceived "mushiness"?
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It already is , and has been as long as I can remember.
HiTech
Then I am aghast.
Since I started playing AH in 2001, I have never been hit in the head with a sledgehammer.
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doesnt seem that absurd, heres a suggested mechanism: deflection of a control surface will change the airflow over the wing, there will be a transition period from one airflow to the other. the transition may introduce more turbulent airflow until it has settled into the deflected state (cause of "mushiness"?). Now factor in the abrupt change of AoA caused by the control surface deflection, again there will be a transition period until the airflow has settled into its new state. during these transitional periods between steady states you might expect more turbulent airflow and consequently a temporary drop in Cl. Could this be the cause of the perceived "mushiness"?
Hitech has already answered your question and illustrated how long the flow change takes. It is not instantaneous of course, but in practical terms it is so short that it hardly makes a difference. It cannot furfill the OP's theory of an elevator being fully deflected, doing nothing for a humanly detectable period of time and then suddenly developing the tail-down force.
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Then I am aghast.
Since I started playing AH in 2001, I have never been hit in the head with a sledgehammer.
You must not be married.
Regards,
Hammer :D
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Good one Hammer :)
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HiTech's posts are just not as much fun since he got a spell checker. :(
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It is not instantaneous of course, but in practical terms it is so short that it hardly makes a difference. It cannot furfill the OP's theory of an elevator being fully deflected, doing nothing for a humanly detectable period of time and then suddenly developing the tail-down force.
i'm not sure I understand what you're saying, you say its "not instantaneous" then go on to argue that there cant be a delay (ie. it is instantaneous). my suggested mechanism (although it may be completely wrong) does explain the delay transitioning from one steady state to the next.
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i'm not sure I understand what you're saying, you say its "not instantaneous" then go on to argue that there cant be a delay (ie. it is instantaneous). my suggested mechanism (although it may be completely wrong) does explain the delay transitioning from one steady state to the next.
The point is that the time-frame for it to happen is too short for it to make a difference because of the human limitation. You are not going to run into a case below compressability speeds where a 190 pilot manages to fully deflect the elevator, nothing at all happens for a discernable moment, THEN the G pile on as the OP alleges. The time between elevator deflection and the development of aerodynamic forces, in this case the tail-down forces that pitch the nose up, is as good as instantaneous from the human standpoint. What I'm getting at here is the difference between pointing out the simple truth that light does not in traverse space instantaneously, and the claim that it is possible for a human to observe, orient, decide, and act quickly enough to dodge a lightning bolt, or the claim that lightning bolts headed for Germans move slower than those headed for Americans :devil
This is assuming that the pilot *can* actually deflect the elevator, and is not to be confused with situations where the control forces are simply too high for him to achieve deflection, which WAS a problem for some WWII planes, able to achieve very high speeds but lacking hydraulic controls, or "compressability" phenomenon at very high speeds when some of the airflow over the plane approaches the speed of sound.
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Also, since there is all this talk of turn rates and radii from someone who does not have pragmatic ACM experience in either the real or virtual skies, I must point out that ANY WWII prop fighter, running along at 350mph IAS or so, would *never* be able to follow an aircraft ~100mph slower in a turn for very long at all. The attempt to do so without reducing speed inevitably results in the much faster plane overshooting the slower one.
Whether the limited by pilot endurance or airframe structure there are only so many Gs a pilot can practically induce in a maneuver. There is a minimum speed at which these Gs can be pulled, pulling these same Gs at higher speeds means reduced turn rate and greatly increased turning circle. Not that attacking with excess speed is useless, indeed it might be considered the favored way to attack in WWII, but that excess speed beyond corner does *not* improve turning circle. The point is being able to convert that excess speed in the vertical to re-attack or just plain extend after a missed gun solution.
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The time between elevator deflection and the development of aerodynamic forces, in this case the tail-down forces that pitch the nose up, is as good as instantaneous from the human standpoint....and is not to be confused with situations where the control forces are simply too high for him to achieve deflection...
Agreed.
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ah I see your point. I imagine the airflow transitions pretty quickly in the elevator deflection phase, but would take longer and be more noticable during the cruise to blackout turn AoA transition, since the airflow is magnitudes more complex over the entire airframe than just the tailplane alone. HT suggests it could be 0.1s range which would be easily noticable to an experienced pilot.
so since we've discovered that there is a delay in the aerodynamic forces taking effect after control deflection, and there is a possible model for it in the real world, are you going to get a library card? :)
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ah I see your point. I imagine the airflow transitions pretty quickly in the elevator deflection phase, but would take longer and be more noticable during the cruise to blackout turn AoA transition, since the airflow is magnitudes more complex over the entire airframe than just the tailplane alone. HT suggests it could be 0.1s range which would be easily noticable to an experienced pilot.
A tenth of a second? Perhaps you don't realize how quick this is. Do you think you could even deflect the elevator in a 10th of a second or less?
so since we've discovered that there is a delay in the aerodynamic forces taking effect after control deflection, and there is a possible model for it in the real world, are you going to get a library card? :)
When I said there was no mechanism for delay, it was pretty clear for those who are *not* clueless that I meant delay of the sort detectable on a human scale, that would say lead to a Fw-190 pilot being able to fully deflect his elevator at 350mph IAS at low altitudes yet somehow have no aerodynamic forces on the tail for several seconds, and then suddenly these forces would "kick in". This was the OP's way of reconciling some wild speculation illogically derived from combat reports with the contradictory fact that repeated tests both by Germans and Allies show the airplane to have reasonable elevator authority at speeds up until at least 350mph.
If you think I meant air can move at literally infinite speed, I despair of you. Someone would have noticed such an interesting phenomenon by now, and I think Mr. Einstein might raise some objections. :devil
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[qoute]so since we've discovered that there is a delay in the aerodynamic forces taking effect after control deflection,[/quote]
I never said any thing of the sort. I said that it takes time from the force being applied at the tail, directly related to stick input. It then takes time for the plane to rotate to develop AOA, It is a simply application an of F = MA and I said from level to stall at corner speed would be in the .1 sec range,if you could move the stick that rapidly, and no, a pilot could not notice this, nor would he be very likely to even move the stick that fast.
The point of this per the OP post is moot. He seems to think that this has something to do with measuring cornering speed. Finding the corner speed of a plane is very simple, you just put the plane at g limit, keep slowing down by raising the nose in the turn while maintaining the same g's until it stalls. The speed at which it stalls is corner speed.
HiTech
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ok so there is the time taken to move the stick, and a corresponding delay as the aircraft changes attitude to a higher AoA, about 0.1s. got it :)
Oh and Gaston, there is no mechanism in the real world for the aerodynamic forces of a deflected elevator to be "delayed", and if you have discovered one, you're the first since Kittyhawk to do so. Here is something for you to do with your time than posting to this forum: Get a library card. Check out a book on basic aerodynamics.
BnZs I dont really need to second guess what your thinking, you were very specific when you stated "there is no mechanism in the real world for the aerodynamic forces of a deflected elevator to be 'delayed' ". I have suggested such a mechanism, which no one so far has refuted. Perhaps if you'd extending your reading to some fluid dynamics as well as basic aerodynamics, you might have taken into account the transient states as well as the steady states in the system.
Gaston found some test data which didnt match up with his expectations or understanding of the subject, so posted on the board for everyone to discuss. This is a good thing, and should lead to a greater understanding of the subject for all. Suggesting that he is wasting peoples time by posting and should go get a library card is not only plain rude, it doesnt promote wider understanding of a subject which many here find interesting.
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Gaston found some test data which didnt match up with his expectations or understanding of the subject, so posted on the board for everyone to discuss.
I have been doing some research, and have proven conclusively that sweet apples fall up. The reason they fall up is because sweets attract things. So with my immense knowledge fluid dynamics it is obvious that any air/wind would be attracted to the apple.
Now the wind would cause this sweet apple to move in the same direction, but because this apple does not complete a 180 degrees of arc do to the wind, it will not have a turning radius. So there fore the only way this can be is if the apple is not falling.
Now Newton was only a scientist he only observed and studied apples he never ate one to know if it was sweet, as opposed to us real people who have far greater knowledge because we eat apples every day. And as the antidote goes we don't like doctors and that is why we eat so many apples. And as must be completely obvious, newton was a doctor of physics and really hated apples. ( I have done research and have proof that he was trying to kill all apple trees).
HiTech
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I have been doing some research, and have proven conclusively that sweet apples fall up. The reason they fall up is because sweets attract things. So with my immense knowledge fluid dynamics it is obvious that any air/wind would be attracted to the apple.
Now the wind would cause this sweet apple to move in the same direction, but because this apple does not complete a 180 degrees of arc do to the wind, it will not have a turning radius. So there fore the only way this can be is if the apple is not falling.
Now Newton was only a scientist he only observed and studied apples he never ate one to know if it was sweet, as opposed to us real people who have far greater knowledge because we eat apples every day. And as the antidote goes we don't like doctors and that is why we eat so many apples. And as must be completely obvious, newton was a doctor of physics and really hated apples. ( I have done research and have proof that he was trying to kill all apple trees).
HiTech
:rofl
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Every one of his "theories" seem to be based on reading a combat report and then pulling stuff out of the air that the author of the combat report never mentioned.
Gaston found some test data which didnt match up with his expectations or understanding of the subject, so posted on the board for everyone to discuss. This is a good thing, and should lead to a greater understanding of the subject for all. Suggesting that he is wasting peoples time by posting and should go get a library card is not only plain rude, it doesnt promote wider understanding of a subject which many here find interesting.
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Quote(Jabberwork);
Man, you're drawing a long bow on some very tenuous conclusions on this one.
A. The pilot only specified a "109" - nothing about a G-6, nothing about underwing gunpods.
-The combat is dated May 25, 1944; it is unlikely in the extreme to be anything other than a G-6 pulling 1.42 ATA.
This other very similar combat on May 19, with the P-47D out-spiral climbing in the same way, shows in the comments of Cpt. Ealey below that the gunfire set off ammunition in the wings;
http://www.wwiiaircraftperformance.org/p-47/er/78-luckey-19may44.jpg
It should be noted, for those who don't know, that May 1944 is a special period in the Western air war; this is the month when the "bombers only" directive was first given by the Lufwaffe high command; a disastrous order that was never relaxed despite soaring losses and NO increase in bombers shot down. Like all stupid orders, it was probably not followed as stricktly in the following months as during the month of May. This is the month were you can see for the first time, and mostly the last time, strings of five or more victories in a single P-47 sortie; in the entire range of P-47 combat reports on the site, only two such P-47 victory strings occur, both in May. Probably a similar, but not identical, story for P-51s. (I am only starting on reading the P-51s)
May 1944 was also the period of the war where, to comply with the new bombers-only directive, I would expect the greatest percentage of gondola equipped 109s. (At this time, these ALWAYS came with a new 109G-6; you had to take them off.)
You'll also have to excuse my bias that the most likely source of evident P-47 spiral climb superiority over the 109 would have something to do with underwing guns...
B. No indication of relative energy states - the P-47 had just come down from 20,000 feet, but we have no indication of the relative speed of the "109". It is highly possible that the P-47 traded speed for angles.
- It is clearly stated that the fight started with both turning at the same time into the climbing spiral. If there was a vast speed difference at the start, the spiral would not have been a lasting contest...
C. The P-47 pilot states "after three or four climbing turns". So, what is it? Three? Or four?.
- I see little difference, and a great congruence, with the speed at the end, that the turns were consecutive...
D. How do you know the turns were "consecutive 360 degree turns"? Again, the AAR states 'three or four climbing turns", not three or four climbing circles, or spirals. It is not clear that the aircraft entered a Luftberry until after the P-47 had made its shots (the Luftberry being a primarily defensive move).
-Again, the 140 MPH IAS speed for a P-47 at the end, at 5000 ft., is pretty explicit as to what went on before, even if the circles were not "perfect"...
E. What is you're evidence that the 109 (which 109 by the way?) is "roughly equal" to the P-47 in a left hand turn?
- I said roughly equal in a RIGHT-hand turn. I think to the left the 109G is slightly INFERIOR to the P-47 at "level" speeds above "low" speeds, by which I mean 200-250 MPH IAS depending on altitude. I make the assumption a downward spiral would exceed these speeds but still would be below diving speeds. There are a few examples that support this fairly narrow notion, but the clearest is this;
http://www.wwiiaircraftperformance.org/p-47/er/78-wilkinson-1dec43.jpg
Note that in the first part of the 109's attack, to the LEFT, the P-47D lost 3 pursuing 109Gs between 28 000 ft. and 20 000, including the last one, at SOME point, with NO shots being fired by the pursuers. On the second part of the attack, by the SAME last aircraft, it took from above 20 000 ft. to 8 000 ft. to turn the tables, this time WITH shots being fired by the pursuer. At the end, I suspect the thicker air gave the lighter P-47 elevators the advantage that the 109 pilot didn't have the time to trim out.
Now I know for a fact that at least the Razorback variant of the P-47 prefers the left turn at high level speeds, there's too much evidence to doubt it, but the above convinced me the 109's left preference was not as marked as the Razorback P-47's, or even the FW-190's. So the 109G at least appears more competitive to the right, and I theorize this would extend to the spiral climb, though I have no specific combat example yet. Century ace Steinhoff said the 109 spiral climb was very effective against BOTH the P-47 and P-51, and one would generally assume that the 109 would be superior to the P-47 in this, but to the left it is apparently closer than it is with the P-51! (Hence my gondola assumption in one case, and my left turn assumption in the other case where the turn side is not mentionned...)
Gaston.
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About mushing;
This is my idea of what the mushing delay might be; basically it means too much pilot authority over the control surface; the pilot pushes the tail down too easily. The plane stalls "straight ahead" in effect.
The fact that the Spitfire's maximum backward stick movement at high speeds is a mere 3/4 inch before "mushing" speaks volumes as to how pronounced the condition can be... Robert Johnson's contorsion of rolling his P-47 OPPOSITE the enemy's turn to avoid mushing is a loud indication of this condition also... I won't dwell on the FW-190A at high speeds...
On the other hand, heavy-elevator aircrafts such as the Me-109G and P-51 don't seem to have such severe mushing issues, though I'd hate to make a "rule" out of it...
But then heavy controls means a delay in pulling... And pull-out problems as well...
There MIGHT be some aircraft types with a delay in actual pitch response; maybe not, or maybe 1/10th of a second as discussed here...
Mushing might allow the pilot to do things not available to more "trajectory rigid" aircraft; in the Spitfire it is documented that this mushing was used to shoot inside the turning circle by pointing accross it (I always add at this point that this was of no use defensively...). The Mustang had more trouble gaining lead, and had to resort to an "oscillation", or flaps, to point "inside", but probably with a shallower angle of reach.
Also, mushing might have allowed the pilot to point the engine's axis of thrust further into the outside of the turn, where the air is made slower relatively by the slanted airflow angle, thus increasing thrust, and thus "hanging on the prop".
In any case, from observing WW II footage (I remember a P-38 under enemy fire in particular), the mushing at the start of the turn can, at some speeds, last as much as 3 seconds or more after the bank is done...
I am now reading into the P-51 combat reports section at "WW II aircraft performance", and I have already seen some interesting stuff that might clarify parts of those unexpected 1990 tests results.
The P-51's WW II turn performance has always mystified me, not at high level speeds, because I always understood that it was superior there, but in sustained turning contests, where the number of consecutive 360°s can be as high as ten or even much more, sometimes on the deck, and yet still the Mustang comes out ahead of a similar turning aircraft like the 109G that has, supposedly, BETTER acceleration...
It strikes me, on reading a few combat reports so far, that the P-51 catches up in multiple 360° turns, but then, somewhat UNLIKE the P-47, has TROUBLE establishing lead, having to resort to ocillations, flaps or short rudder kicks to get very brief leads. In lower speed turns, apparently, the P-51 does NOT out-turn the 109G... This tends to support the 1990 test's statement of the P-47's overall superiority to the P-51 in turning, which seems so odd to us, and yet is confirmed not only by the lack of trouble the P-47 has to establish aiming leads in countless combat reports, but also by the Germans themselves: In the recently published book "On Special Missions", the Luftwaffe evaluation of the P-47 was a flat-out; "superior in turns to the Bf-109G", whereas the p-51B was "dangerous in the stall, one of our pilots was killed"... Yet they still were more impressed with the P-51...
So how come the Merlin P-51 won turning contests versus the Me-109G? Let's listen to some examples that I found illuminating;
In "Jagdwaffe "Defending the Reich"" vol.5, section 3, p.202; "Oseau was attacked by P-51s which forced him into a turning dogfight. Each turn became tighter, and the BF-109 slowed down, MORE SO THAN HIS ADVERSARIES." Now let's remind ourselves that Oseau's aircraft in this fight was a Me-109G-6AS, no less! (No gondolas...) Even more tellingly, this witness of the fight, a young Oberfahnrich, adds; "Oseau was probably shot down near the ground." So in his opinion, as a witness, Oseau was out-turning the Mustangs, and would have continued to do so, until he could rely only on his engine to turn...
Leo Schuhmaher of II./Jg1 said, relating to this combat; "Several times I had said to Oseau the FW-190 was better than the Bf-109, but being an old 109 hand, he preferred it."
On the "WW II aircraft performance" site, several quotes are offered besides the P-51 combat reports. Note the first one below the "Turn" segment of these quotes, and its telling similitude;
"The E/A could not turn with me without losing altitude, and eventually I got on to him."
or "I could out-turn him easily, but could not pull quite enough enough lead to get strikes."
or "I could out-turn him all right, but once in a while I'd hit a high speed stall trying to get enough lead on him."
or "They both started turning to the left and we fell into a luftberry that continued for 10-15 minutes."
Now, of course, I could be accused of cherry-picking those quotes that best illustrate what I intend to say, but I'll note that the P-47D, in continuous turns, either out-turns rapidly or does not out-turn at all (with the previously posted, Wilkinson Dec 1, 1943 example being one of the rare exceptions of a continuous downward spiral of several minutes). And, if in a position to fire, the P-47 NEVER has trouble gaining lead, but much more often will have trouble seeing the target hidden by its nose... Generally, it could be said that: The P-47 has trouble seeing because it leads from the inside of the circle, the P-51 has trouble leading because it sits on the outside of the circle...
The P-51 usually comes in from behind in prolonged turns, which suggest, combined with the above, that it does not out-turn, but in fact out-ACCELERATES (or more accurately I think, does NOT decelerates as much) within a similar or wider turn; and the pilot will say; "I out-turned him" But he did so following the same or an even wider turn; which explains the airshow clip posted here where the two interviewed airshow pilots who respond, without hesitation; "Oh, definitely the 109 out-turns the P-51". But if the P-51 is maintaining better speed on a similar or wider turn (at non-airshow 67-72" WEP!), it's STILL gaining...
For some reason the P-51, despite a mostly inferior climb rate to a "clean" 109, a probable inferiority in sustained climbing turns, and possibly an inferior turning radius at low or even medium speeds, is noticeably superior in maintaining speed in level turns, so that it still wins low-speed turning battles, ESPECIALLY near the ground...
This would mean the 1990 tests could be correct about the P-51's high corner speed (being easy to establish as Hitech said), but made the wrong assumptions about its ability to sustain low-speed turns.
Why does the Mustang accelerates (or NOT decelerates) so well in level turns, but NOT in climbs, is quite a mystery to me, but it seems to me this would explain some of the various contradictions we see here...
Gaston.
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I have been doing some research, and have proven conclusively that sweet apples fall up. The reason they fall up is because sweets attract things. So with my immense knowledge fluid dynamics it is obvious that any air/wind would be attracted to the apple.
Now the wind would cause this sweet apple to move in the same direction, but because this apple does not complete a 180 degrees of arc do to the wind, it will not have a turning radius. So there fore the only way this can be is if the apple is not falling.
Now Newton was only a scientist he only observed and studied apples he never ate one to know if it was sweet, as opposed to us real people who have far greater knowledge because we eat apples every day. And as the antidote goes we don't like doctors and that is why we eat so many apples. And as must be completely obvious, newton was a doctor of physics and really hated apples. ( I have done research and have proof that he was trying to kill all apple trees).
Bravo!! Best belly laugh I've had for weeks.
Badboy
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Why does the Mustang accelerates (or NOT decelerates) so well in level turns, but NOT in climbs, is quite a mystery to me, but it seems to me this would explain some of the various contradictions we see here...
To put it very over simplified.
Climb & acceleration are just different measurements of the same thing. I.E. Power/wight.
Sustained turn rate is a more a function of Power / drag.
Instantaneous turn rate is a function of Lift / weight.
HiTech
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About mushing;
This is my idea of what the mushing delay might be; basically it means too much pilot authority over the control surface; the pilot pushes the tail down too easily. The plane stalls "straight ahead" in effect.
The fact that the Spitfire's maximum backward stick movement at high speeds is a mere 3/4 inch before "mushing" speaks volumes as to how pronounced the condition can be... Robert Johnson's contorsion of rolling his P-47 OPPOSITE the enemy's turn to avoid mushing is a loud indication of this condition also... I won't dwell on the FW-190A at high speeds...
An airplane stalls when the critical AoA is exceeded. That is it. It cannot stall "straight ahead" or any some such nonsense unless this happens. Please, for the last time, learn some basic aerodynamics.
One of three things can happen when the pilot pulls back on the stick at speeds below compressability:
1. The airplane pitches nose-up until critical AoA is reached at which point it stalls.
2. The plane pitches up and the critical AoA is increased until the lift generated puts too many Gs on either the airplane structure or the pilot, resulting in either relaxation of stick pressure, blackout, or structural failure. This is a possibility only above a certain airspeed, referred to as "corner velocity", below corner velocity the airplane will stall before this many Gs are pulled.
3. If the airspeed is high enough, the pilot may lack the requisite physical strength to deflect the elevators enough to pull max Gs.
That is it, there is no "mushing" phenomenon of the kind you are theorizing, Hitech has already explained what this term actually means as typically used by pilots.
Do you understand how elevators work at all in the conventional horizontal stab arrangement? The plane is flying along, and the wing is generating lift. When the pilot pulls back on the stick, down force on the tail is generated. Think of the wing as a fulcrum. The nose *will* pitch up, which in turn increases the wing's AoA. The tail can no more go down without the nose pitching up and the AoA increasing than you can move one end of a see-saw downwards without the other rising. On some level I cannot believe I am having to explain this to an adult human being supposedly familiar with airplanes.
I have read "Thunderbolt" so many times that the cover is falling off, and Bob Johnson never once mentions "mushing". If you knew the *slightest bit* about ACM you would recognize rolling in the opposite direction for what it is, a lag roll type maneuver, nothing other than three-dimensional geometry being used to maintain shooting position.
As for the rest, there are simply far too many unknown variables in combat reports to gain much useful info from them, even if one can refraim from adding wild and erroneous speculations to what is actually written, which apparently you can not. The simple act of going 'round and 'round in a Luftberry involves as much pilot skill at riding the edge as airplane performance if the airplanes are even vaguely similar in sustained turn performance.
BTW, what you are going for in your P-51 "theorizing" is the idea that a P-51 might have a superior sustained turn *rate* even if inferior in sustained turn radius to the 109, rate being the deciding factor in nose-to-tail turns. And an airplane with a sustained turn rate advantage/turn radius inferiority chasing one with the opposite attributes will often find itself in what is called cold-side lag. Unfortunately, you have no more knowledge about ACM than aerodynamics. Which is unfortunate, because it would save you a great deal of typing and us a great deal of rebutting inane, insane, and physically impossible hogwash.
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Robert Johnson DID use the term "mushing" in his interview, and he DID say "no mushing" after rolling in the opposite direction to his turn... I don't think he even moved the nose up to get some "oblique turn" gravity help. I think the maneuver helped the weaker "high" wing get more bite in the turn transition... That's what it sounded like to me. Ask Widewing.
Gaston.
P.S. BTW, kind of interesting how the anecdotes are piling up on the side of those 1990 tests that the P-47D and FW-190A were better-turning than the lighter P-51Ds and Me-109Gs, isn't it?
Oseau also had trouble believing it, and this explains the frustration of Ofw Leo Schuhmacher who said, in reference to a turnfight; "Several times I had said to Oseau that the FW-190 was better than the Me-109..."
It is counter-intuitive, but it was generally true.
The higher altitude fighting and the climb rate still made the 109 necessary, in any case, but by the end of 1944 it was only 30% of the Western Front fighter strenght.
G.
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I have yet to come across any interview where he mentions mushing in relation to this move. I do know this maneuver was a form of lag roll. This is easier for me because I actually know what a "lag roll" is and its place in the ACM repetoir. Geometry is more the point here to avoid the overshoot and move to a position more to the rear quarter, "gravity assist" is incidental. "Higher wing getting more bite" is arrant nonsense. You don't get uneven AoA without rotation. This incident does not describe Johnson attempting to practice his spin recovery techniques during the middle combat. If he had executed a snap-roll, he would have said snap-roll.
P.S. BTW, kind of interesting how the anecdotes are piling up on the side of those 1990 tests that the P-47D and FW-190A were better-turning than the lighter P-51Ds and Me-109Gs, isn't it?
Too bad every single actual flight-test, and the opinion of WWII pilots disagrees with that conclusion. The plural of anecdote is NO data.
In the case of 109G vs. Fw-190A, it is literally physically impossible for the 190A to have a tighter sustained radius of turn or better sustained radius of turn, unless perhaps the loading is very biased, a very late-war high-wingloaded 109G laden with gondolas against an early-model 190 with the outer MG/FFs removed. But even there it is unlikely.
The things that would make it possible for a heavier wing-loaded plane to have a tighter sustained turn radius are: 1. A higher Clmax, either because of the airfoil itself or lift-increasing devices such as flaps superior to that of the 109G, which the 190A does not have or 2. A *much* superior power loading, which the 190A also does not have. A superior sustained *rate* for the heavier wing-loaded aircraft can be a product of a superior ratio of thrust/induced drag, which is also not the case for 190 vs. 109G. The physics here are not debatable.
Everything resembling a valid flight test that the rest of the world has heard of agrees that the 190A's rate and radius of turn are poor. British tests of captured examples say this. German tests say this. It could not match a Corsair or Hellcat in tight maneuvers. The Russians, fighting against both, say the 190's maneuverability was considerably inferior to the 109s. The only way a 190 ever even achieved relative neutrality against a 109 was likely by being tested/flown by someone who believed the 109 slots opening=imminent stall and thus never achieved Clmax while turning the 109, which was often the case even with green Luftwaffe pilots, to say nothing of Allied testers.
Every flight test anyone *besides* you has ever heard of confirms that the 109s controls become heavy at speeds starting at around ~280mph IAS, while the 190s was good to at least 350. This, along with firepower, cockpit size and visibility, ease of take off/landing, and ease of management constitutes the primary reason the 190 was preferred by the Allies.
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Bob Johnson did comment on the P-47 mushing...
CCJ: What about a situation where you end up in rolling scissors with a Focke Wulf? Do you follow him by reversing the turn too?
RSJ: No. Whenever you get into a series of reverses, the airplane tends to mush-out a bit when you reverse your turn. The Jug tended to mush a bit more than the 190. The way to avoid this was roll into the reverse.
CCJ: I'm not sure I follow you.
RSJ: Picture this in you mind. The 190 rolls into a hard left. You follow, firing as he crosses your guns. Suddenly, he reverses his turn, hard right. Rather than reverse, you continue rolling left until you are in a right bank, just like the 190. Now, pull hard. No mushing. If he reverses again, you roll left and fire as he crosses your guns. If he doesn't reverse, I pull the nose high and roll out behind him.
My regards,
Widewing
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It sounds like "mushing" in this case refers to the effect of inertia in the roll. Which is a new use of the word on me, but not anything outside of the laws of aerodynamics. :)
Bob Johnson did comment on the P-47 mushing...
CCJ: What about a situation where you end up in rolling scissors with a Focke Wulf? Do you follow him by reversing the turn too?
RSJ: No. Whenever you get into a series of reverses, the airplane tends to mush-out a bit when you reverse your turn. The Jug tended to mush a bit more than the 190. The way to avoid this was roll into the reverse.
CCJ: I'm not sure I follow you.
RSJ: Picture this in you mind. The 190 rolls into a hard left. You follow, firing as he crosses your guns. Suddenly, he reverses his turn, hard right. Rather than reverse, you continue rolling left until you are in a right bank, just like the 190. Now, pull hard. No mushing. If he reverses again, you roll left and fire as he crosses your guns. If he doesn't reverse, I pull the nose high and roll out behind him.
My regards,
Widewing
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Thanks for the quote, Widewing.
It seems mushing in this case is due to the momentum of the turn being one way, reversing the turn aggravates this, and thus the pilot is well aware of it.
R. Johnson-"Now pull hard. No mushing." That is clearly meant as ELEVATOR-related mushing, and that is exactly how I took it.
The P-47, especially the razorback, was known for its crisp aileron reversal, which probably is why Johnson makes the strange statement that the P-47 "rolled as quickly" as the FW-190; the good reversal probably gave a better impression than the actual number performance.
Now consider this logically; which has the greater mass and leverage, and is the more likely as such to cause some delay to an action; the front of a 30 foot fuselage loaded with a P&W 2800 engine, or the tip of a wingtip on the end of a 15 foot wing?
In addition, there may be mushing the pilot is not aware of, if WW II footage is any guide; mushing the way I understand it does not necessarily imply a lack of immediate turning; Johnson clearly states the 190 does not mush as much in reversed turns as the P-47, however the FW-190's prolonged turn performance at high speed is poor, so that even if it pulls an impressive 4-5 Gs in the turn, if the theoretical "perfect" circle would have allowed 7 Gs, then there could still be two full G's lost to "mushing" in an "elongated" turn.
It could also be that the response is immediately to a full 7G potential for the first 90°, then as the attitude of the aircraft reaches close to 90° to the original trajectory, the aircraft would then "sink" horizontally in the same direction as its starting trajectory, decelerating into a wider turn while still imposing on the pilot 7Gs for a short time. The pilot could very well not be aware of it.
Given how not-so-crisp a lot of WW II footage elevator pitch responses look, I don't think it is outlandish to say "mushing" has some effect on turn performance...
As for the 190 turn performance, I already posted in a previous thread a test that illustrates PERFECTLY the point that the 190A performs better in turns relative to the P-47D at lower speeds, and not at higher speeds. The same P-47D that out-turns the 109G according to the Germans themselves... (See "On Special Mission"; Kg 200)
Gaston.
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As for the 190 turn performance, I already posted in a previous thread a test that illustrates PERFECTLY the point that the 190A performs better in turns relative to the P-47D at lower speeds, and not at higher speeds. The same P-47D that out-turns the 109G according to the Germans themselves... (See "On Special Mission"; Kg 200)
Gaston.
Johnson could roll his P-47 as quickly as the 190 pilots because a primary limitation on roll rate at speed in WWII airplanes with unboosted controls was how much the pilot could deflect his ailerons, and Johnson was quite the athlete. But that would not keep the 47 from having more inertia in a roll due to say 4 .50 cals and ammo in each wing, in an aircraft double the mass of the Fw-190. Whereas whether he is reversing his turn by rolling right/left or by continually rolling one direction, it is still a reversal and wing lift must still be used to change the aircrafts flight path in the same way.
The 190A has a similar wing loading to the P-47 and a superior power loading at low altitudes. It is not at all like comparing it to the 109G, which is superior in every trait related to turning and which is acknowledged to be the better turner of the two. You continually fail to understand how a combat reports are not useful for giving us any concrete data about aircraft performance because of the unknowns. And this "2G's lost to mushing"...again BS. G forces are induced when lift being used to turn the aircraft. A 747 and an RC model, if they could be at the same speed, at the same bank angle, pulling the same Gs would be producing *the same rate and radius of turn* Once again this is not up for debate.
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It seems mushing in this case is due to the momentum of the turn being one way, reversing the turn aggravates this, and thus the pilot is well aware of it.
No he is referring to roll responsiveness I.E. rolling one way, then rolling the other, nothing about what your are referring to as mushing.
2nd even though he does not state it, this roll reversal sounds like it is well below corner speed. I.E. he is at the Top of the lag roll. Because at corner speed I would have a very hard time believing the Ailerons felt soft.
Now consider this logically; which has the greater mass and leverage, and is the more likely as such to cause some delay to an action; the front of a 30 foot fuselage loaded with a P&W 2800 engine, or the tip of a wingtip on the end of a 15 foot wing?
Once again you are incorrect, the mass of a motor that is in the center of the airplane will have very little to do with the planes total rolling moment as compared to gas and other things mounted in the wings.
It could also be that the response is immediately to a full 7G potential for the first 90°, then as the attitude of the aircraft reaches close to 90° to the original trajectory, the aircraft would then "sink" horizontally in the same direction as its starting trajectory, decelerating into a wider turn while still imposing on the pilot 7Gs for a short time. The pilot could very well not be aware of it.
Say WHAT?
If the pilot is maintaining 7 g's for the turning circle to become "wider" the plane would have to accelerate. (This is not debatable).
HiTech
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Agreed on this last point; if the aircraft mushes at the mid-way point of a 7G 180° turn, the turn can no longer be 7 Gs; my mistake... The point I wanted to make was that if the mushing occurs, with the aircraft pointing at close to 90° to the starting trajectory, BEFORE the halfway-point of the semi-circle (implying pointing the nose INSIDE its turn "perfect" circle, while skidding past the "perfect" circle itself), then the mushing would feel like a near-vertical deceleration that would seem to the pilot like close to the same thing as "normal" turn-related Gs.
But then you said that the degrees per second of pivoting made by a fighter's nose cannot be at a different rate than that implied by the turning circle itself...
It was one of the characteristics of the Spitfire that it could do this, mushing with full 3-axis control and shooting "inside" its own turn.
I don't see how it can be denied that the Spitfire flew like this...
The "scientific" term might be an accelerated stall, but if full 3 axis control remains, I think calling this a stall is a factor of confusion rather than clarity...
As for the Jonhson interview, look at the wording; "the airplane tends to mush-out a bit when you reverse your turn" He did NOT say: " the airplane tends to mush-out a bit when you reverse your ROLL"
Also; "Now, pull hard. No mushing."
I will concede his words could be interpreted either way, but my impression is that he felt reversing the roll affected the turn response, and that by continuing the same roll he sensed that his turn response was more immediate.
Also, if mushing in the roll response was what was in question, this mushing loss was unlikely to be as great as continuing through 270° to roll "the long way around". On the other hand, mushing in the turn response could well be worth rolling 270° to avoid.
Even if it turns out the intended meaning was for roll only, it still remains that one of the tactical advantages of the Spitfire was to be able to shoot inside its own turn, and even the Mustang had to resort to it (with difficulty) because of its noticeably wider (if faster) turn...
As for the relative turn rates, I think the real-life results are often counter-intuitive to calculated values, and the fact that the 1990 tests were done by real test pilots, and caused a surprise as to the expected outcome, means we should not dismiss them as unimportant. The fact that Warbirds were not their area of primary interest, since they in fact mostly tested other kinds of aircrafts, actually increases their credibility. Their comments about lower speed sustained turns do seem speculative... I plan to order the complete report eventually...
Gaston.
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"then the mushing would feel like a near-vertical deceleration that would seem to the pilot like close to the same thing as "normal" turn-related Gs."
More likely it will feel like relaxation of Gs due to loss on "foot hold" due to mushing i.e stalling through turn. Maybe you meant this by saying "deceleration" as deceleration generally means less Gs.
"It was one of the characteristics of the Spitfire that it could do this, mushing with full 3-axis control and shooting "inside" its own turn. I don't see how it can be denied that the Spitfire flew like this..."
I'm not sure what this means but I'm willing to claim that Spit, of all planes, cannot do such thing. Due to wash-out it can enter a controlled half-stall where root of the wing has stalled but the wing tips have not, but if the critical AoA for its wingprofile is around 13 degrees, with wash-out it would be around 15 deg but considering the shape of the leading edge it is still dangerously on the verge of a full span stall. On the other had Bf109 probably could do this because of the wingtip slats which make such radical maneuver possible, although not from a 7G turn...
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I will concede his words could be interpreted either way, but my impression is that he felt reversing the roll affected the turn response, and that by continuing the same roll he sensed that his turn response was more immediate.
Also, if mushing in the roll response was what was in question, this mushing loss was unlikely to be as great as continuing through 270° to roll "the long way around". On the other hand, mushing in the turn response could well be worth rolling 270° to avoid.
Even if it turns out the intended meaning was for roll only, it still remains that one of the tactical advantages of the Spitfire was to be able to shoot inside its own turn, and even the Mustang had to resort to it (with difficulty) because of its noticeably wider (if faster) turn...
Read again, why do you think he continued to roll in the same direction when he needed to reverse his turn, I.E. you can roll 180 left or 180 right and the the out come is exactly the same. It is simply because of the slow roll reversal, it is very obvious that is what he is speaking about.
But then you said that the degrees per second of pivoting made by a fighter's nose cannot be at a different rate than that implied by the turning circle itself...
While this is mostly correct, I did not say this. During the time you are increasing AOA, the 2 rates can be different. But this time span is very short, and for most purposes can be ignored.
Even if it turns out the intended meaning was for roll only, it still remains that one of the tactical advantages of the Spitfire was to be able to shoot inside its own turn
All planes can do this. When flying at max AOA, all planes are shooting inside their turning circle . The exact degree inside the circle is simply AOA - (wing incidence measured from the guns). This would normally be in the 14 - 16 degree range.
HiTech
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I have just remembered a combat anecdote that MAY prove Johnson's "mushing" description refers to a mushing TURN, NOT a mushing roll;
He encountered a FW-190D at a fairly high altitude; 25 000 ft. +.
He approached the FW-190D from behind, which saw him late; the FW-190D broke LEFT at the last moment.
Jonhson then rolled RIGHT 270°, and pulled-in in a continuous turn that the 190D never changed for a long period. (I assume this was his razorback, because on his second tour he never scored)
Now if the roll rate "mush" was what he wanted to avoid, he could have rolled left, and if the German reversed right he could easily have CONTINUED his left roll a further 180°, until being in a right bank. This is EXACTLY what he described doing in his interview with Widewing. However, this is NOT quite what he did in this actual combat...
In actual combat he started his roll OPPOSITE the FW-190D's left turn. My theory why he did this is this; the high altitude (25 000 ft. +) introduced different priorities; roll speed and reverses are LESS important, mushing in turns MORE important.
A full opposite RIGHT roll equals a "pull hard. no mushing" turn to the LEFT, his top priority at this high altitude. He even describes how the P-47 responded "beautifully" to the turn...
The loss of time implied by rolling opposite; here at LEAST 2-3 seconds (more at high altitude) compared to a 1-2 second 90° left roll, means he hoped to gain by some other means than roll, unless the P-47 rolled so much better to right always that he always rolled right no matter what...
But then he would not have described to Widewing doing a left roll, continuing it through 270° against a left-breaking, then reversing, 190, if that's NEVER what he did...
I think if the 190 had broken to the right at this high altitude, he could very well have rolled left to take out the "mushing" of his subsequent right turn, after the usual full 270° roll. It would make sense as this would be the exact mirror-image of what he actually did at this altitude.
At a lower altitude it could have been a different tactic; roll rates would be faster and "mushing" in turns less pronounced. It could even be that at lower altitudes the slower P-47 right turn is more apparent, so he would roll right with a right-breaking 190, and left with a left-breaking one, continuing the roll 270° IF a reverse occurred; exactly what he described to Widewing.
So it does seem the grammatical meaning of what he said is closer, since he never applies "mushing" to the word roll, but to turn.
Gaston.
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I have just remembered a combat anecdote that MAY prove Johnson's "mushing" description refers to a mushing TURN, NOT a mushing roll;
He encountered a FW-190D at a fairly high altitude; 25 000 ft. +.
He approached the FW-190D from behind, which saw him late; the FW-190D broke LEFT at the last moment.
Jonhson then rolled RIGHT 270°, and pulled-in in a continuous turn that the 190D never changed for a long period. (I assume this was his razorback, because on his second tour he never scored)
Now if the roll rate "mush" was what he wanted to avoid, he could have rolled left, and if the German reversed right he could easily have CONTINUED his left roll a further 180°, until being in a right bank. This is EXACTLY what he described doing in his interview with Widewing. However, this is NOT quite what he did in this actual combat...
In actual combat he started his roll OPPOSITE the FW-190D's left turn. My theory why he did this is this; the high altitude (25 000 ft. +) introduced different priorities; roll speed and reverses are LESS important, mushing in turns MORE important.
A full opposite RIGHT roll equals a "pull hard. no mushing" turn to the LEFT, his top priority at this high altitude. He even describes how the P-47 responded "beautifully" to the turn...
The loss of time implied by rolling opposite; here at LEAST 2-3 seconds (more at high altitude) compared to a 1-2 second 90° left roll, means he hoped to gain by some other means than roll, unless the P-47 rolled so much better to right always that he always rolled right no matter what...
But then he would not have described to Widewing doing a left roll, continuing it through 270° against a left-breaking, then reversing, 190, if that's NEVER what he did...
I think if the 190 had broken to the right at this high altitude, he could very well have rolled left to take out the "mushing" of his subsequent right turn, after the usual full 270° roll. It would make sense as this would be the exact mirror-image of what he actually did at this altitude.
At a lower altitude it could have been a different tactic; roll rates would be faster and "mushing" in turns less pronounced. It could even be that at lower altitudes the slower P-47 right turn is more apparent, so he would roll right with a right-breaking 190, and left with a left-breaking one, continuing the roll 270° IF a reverse occurred; exactly what he described to Widewing.
So it does seem the grammatical meaning of what he said is closer, since he never applies "mushing" to the word roll, but to turn.
Gaston.
A couple of points... Bob never encountered a 190D as they didn't enter service until he was long gone from combat. He may have run into a prototype... Maybe, but not likely.
Johnson only did one tour, which was extended for a few additional missions to get 27 kills (he was going to be pulled from combat when he reached 27). Johnson was on his way home in May of 1944.
My regards,
Widewing
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Lag Roll
(http://www.tpub.com/content/aviation2/P-1222/P-12220028im.jpg)
An appropriate maneuver whenever one has energy and excess lead on the bandit. But where does this condition come up most in actual combat? When one is pursuing a bandit who reverses his turn, which automatically converts any lag or pure pursuit approach you may have been following into lead pursuit, thus making a lag roll an appropriate response if you don't want to try just shooting him as he crosses.. Obviously a good way to counter an opponent with a fast roll-rate scissoring willy-nilly....whether he ends up going right, or going left, you can enter smoothly into an appropriate maneuver that retains the offensive.
Now you know what a lag roll is. If you knew the name, form, and purpose of the rest of the BFMs, you might be able to cease converting good honest combat reports into walls of text composed primarily of equine exhaust product.
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No. Whenever you get into a series of reverses, the airplane tends to mush-out a bit when you reverse your turn.
To reverse a turn is to state roll the other way.
rather than reverse, you continue rolling left until you are in a right bank,
Why would rolling an addition 180 degrees left and then pulling for a right hand turn, vs rolling right and then pulling for a right hand turn make any different to the turn performance.
Answer it would not, but it would make a substantial difference to the roll performance.
Hence why the turn mush simply refers to the roll response.
If you do not wish to see this simple fact, then all hope of you understanding the basics of ACM is hopeless. Because roll performance and reversal timing is what wins a scissors as he describes.
HiTech
HiTech
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From HiTech:
"If the pilot is maintaining 7 g's for the turning circle to become "wider" the plane would have to accelerate. (This is not debatable)."
HiTech has it, mathematically completely true. If may humbly add to this, none or few aircraft of WW2 could do this without the loss of altitude, and neither could the pilots. (Pressure suit issue etc). Basically you'd say 5 G's for 5 seconds, or tops 6 for 6, and you're ... out.
I think many on the boards actually forget about the vertical factor in turns though.
Just the cents.
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The Spitfire's advantage in "mushing" was described in company of the 3/4 inch stick top maximum pull range limit above 300 MPH, which, if exceeded, caused a very stable, full 3-axis control, high-speed "stall" that allowed to shoot easily inside the turning circle. Better than most other aircrafts in this respect... This is from an actual mid-late Spitfire flight test, not theories... (Probably a Mk V, but these characteristics were described as typical of all Spitfires.)
In addition, with its slats deployed, the Me-109G has been quoted here as being capable of maintaining level flight in a continuous 40° nose-up attitude... Constant "mushing" in other words...
The "lag roll" would indeed explain why Johnson rolled the opposite way to the target's turn, although I don't think he had much excess speed, since the 190 was higher, and the subsequent dogfight was quite prolonged. The term lag roll was never mentionned, nor climbing above the enemy, but it might make sense, if he assumed his faster P-47 would catch-up eventually, to buy extra turning room by rolling away from the enemy's turn.
In any case, this instance would be the only time in thousands of reports that I hear of an attacker rolling opposite to a target's turn, and this happens to involve the very pilot who mentions, ambiguously to me; "mush-out a bit when you reverse your turn" and "Now pull hard. No mushing."...
As for the 190D, that too seemed strange to me, but you read commonly from U.S. pilots, in early '44, about "modified" 190s, Me-209s, FW-290s "fighters" etc... Misidentification of non-existent types...
Although I can't claim to know what Johnson was thinking, and thus I may very well be wrong, there are some factors that would tend to at least lean things towards "mush" being related to turn, not roll.
1- "Mushing" is a common WW II-era term that is almost always related to turns, NEVER to roll. For roll, the more common terms would be; "lag", "soft", "delay" or "not crisp".
2- At usual P-47 combat speed, which typically you would want above 200 MPH IAS, roll reverse lag is a negligible issue, especially in the P-47!
Quote, Hitech;"2nd even though he does not state it, this roll reversal sounds like it is well below corner speed. I.E. he is at the Top of the lag roll. Because at corner speed I would have a very hard time believing the Ailerons felt soft."
-For once we fully agree on this, because, as I explained earlier, the leverage of the engine's weight against the 30 foot distant elevators is obviously an infinitely bigger issue than the leverage of the weight of a 15 foot wing against the ailerons...
At any reasonable combat speed that could be considered "typical", especially at the start of the fight, the "mushing" of the ailerons is simply not that big of an issue...
The P-47's roll rate increased all the way to 230 MPH IAS+, and stayed high much further. Futhermore, the Razorback P-47 was NOT known for its slow roll reversal, and in fact I have read often that it was a particular strenght of the type...
It just doesn't seem as being as big an issue as would be required for Johnson's quote, because unless the 190 reverses EXACTLY at the precise moment he reaches a 90° bank, it makes no difference whether his remaining 180° roll is right or left to reverse... Again, Hitech correctly pointed this out...
3- Finally, I remember now yet another thing that made me lean towards a "mushing" turn interpretation of Johnson's words, rather than the simpler and more obvious "mushing" roll. This is said to be in his biography;
"When banking for a turn, the P-47 tends to auto-rotate." This could have been;
"When banking RIGHT for a turn, the P-47 tends to auto-rotate."
Now "auto-rotate" can mean one of two things; the nose drifts towards the bank side, which would be natural and would not require corrective rudder action. Hardly a problem worth mentionning...
OR it could mean; the nose drifts OPPOSITE to the bank side, which would then open a whole new can of worms, because it would establish a link between the rolling action and the turn behaviour, which is what is not accepted here.
So it could pay to have long "opposite" rolls, to drift the nose the (opposite) way you want, and this might affect how the turn will respond after a long 270° roll; with more "bite" (and reduced angle-off), perhaps because of a less disturbed prop airflow spiral? Hence; "pull hard. No mushing."
At high altitudes, you don't expect many roll reverses from the opponent, because rolls are not as fast, so you start your roll OPPOSITE to the enemy's turn to drift the nose the right way, and so take out the angle-off and "mushing" with a full 270° opposite roll.
At lower, more typical altitudes, you EXPECT the 190 to reverse at some point, so you match his roll side, knowing that, if he reverses, it will give you again the full 270° or 180° roll that drifts the nose the opposite way and takes out both "mushing" and angles.
This matches my perception that "mushing" in turns was a P-47 problem (diminishing with speed) while the P-47 "mushing" in rolls is not a characteristic of the P-47 I have ever heard, on the contrary...
I don't intend to defend this interpretation all the way to the Supreme Court, as I think the "roll" meaning is 80% more likely to be correct, but I would appreciate if someone could quote in detail Johnson's book, and tell me what is the meaning he intended for the P-47 "auto-rotating" in a roll...
Gaston.
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"The Spitfire's advantage in "mushing" was described in company of the 3/4 inch stick top maximum pull range limit above 300 MPH, which, if exceeded, caused a very stable, full 3-axis control, high-speed "stall" that allowed to shoot easily inside the turning circle. Better than most other aircrafts in this respect... This is from an actual mid-late Spitfire flight test, not theories... (Probably a Mk V, but these characteristics were described as typical of all Spitfires.)"
Let me explain why this is not accurate. First of all Spitfire has a 13% thickness ratio (NACA 2213/NACA 2209.4) wing profile i.e. thinner than other planes of that era. The relative thickess to other wings is nearly the same but aerodynamically its own thickness ratio is what determines how it behaves at extreme AoAs. In general the thickness ratio enhances the max AoA behaviour, to a certain limit, of course. If the wing had the same thickness (15-16%) as other aircraft of that era it would have been very thick (for that wing area) and the drag would have been excessive. Also the rather low relative thickness allowed the Spit to make a very fast dive even to the extent that the airframe was not able to withstand such speeds.
Secondly the elliptical planform is very good, if not ideal, in terms of dealing with drag but the negative side of such planform that has even span loading is that it loses all the lift at once in a stall. This, mildly said, disturbing feature was countered with 2 degrees wash-out (quite standard, as in P51 and FW190) which gave ample warning of stall. However due to overly sensitive elevator control it was still easy to pull too quickly too much AoA which caused a full span stall, although veteran Spit pilots were not likely to make such mistake. The bob weights in controls in later variants further helped in preventing this.
109's maximum level flying angle is claimed to be as high as 60 degrees (supposedly for G2 or G6). While it certainly had advange of its wing tip slats I find it somewhat hard to believe this and have never heard or read of this being used to advantage in actual combat.
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First of all Spitfire has a 13% thickness ratio (NACA 2213/NACA 2209.4) wing profile i.e. thinner than other planes of that era. The relative thickess to other wings is nearly the same but aerodynamically its own thickness ratio is what determines how it behaves at extreme AoAs. In general the thickness ratio enhances the max AoA behaviour, to a certain limit, of course.
Generally, thinner airfoil sections stall faster than thicker airfoil sections. Certainly most 15% sections stall later than 13% sections.
If the wing had the same thickness (15-16%) as other aircraft of that era it would have been very thick (for that wing area) and the drag would have been excessive.
Compared to what? The P-51 profile was thicker and even at maximum thickness at the root chord, the P-51 had less profile drag at the design lift coefficient. The P-47, Corsair, Hellcat...even the 190 had a thicker root chord and the common 23015 section they shared had lower profile drag. The Spitfire turbulent airfoil is a section that possesses an extremely high profile drag coefficient compared to most other NACA airfoils.
Secondly the elliptical planform is very good, if not ideal, in terms of dealing with drag but the negative side of such planform that has even span loading is that it loses all the lift at once in a stall. This, mildly said, disturbing feature was countered with 2 degrees wash-out (quite standard, as in P51 and FW190) which gave ample warning of stall.
And, in doing so, Supermarine eliminated the only advantage the planform offered. With the washout built into the wing, the elliptical lift distribution was lost, and the Spitfire laid claim to a wing that ranked as one of the highest drag wing designs in the war.
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Gaston: I have a few question.
1 Do you wish to learn basic physics
2 Do you believe physics will never change and can not be ignored in any evaluation of flights?
3 Do you wish to understand basic terms as they relate to flying?
HiTech