1990 tests; P-51/F6F/P-47/FG-1; all corner speeds close to max. level speed?

[BnZs]

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

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.

[BnZs]

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.

[Stoney]

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. 

[RTHolmes]

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?

[BnZs]

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.

[hitech]

[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

[RTHolmes]

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.

[hitech]

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

[morfiend]

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

     

[BnZs]

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.

[Gaston]

    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.

[Gaston]

   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.
       

       


   

   

   

   

[Badboy]

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

[hitech]

     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

[BnZs]

   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.