Utilizing the P-51D's instability

[AquaShrimp]

I would say this maneuver might be on the negative g-limits of a Mustang.

[Yeager]

you are saying the Cobra wasn't a Russian invention,
====
How do you "invent" physics?  

This thread passed me by intentionally as I never want my P51 FM to become unstable.  Ive ended too many other P51s sorties while they were in this condition to want to go there myself.

[Kweassa]

Two things:


1) The "Dogfights" episode portrays the spinning phase of the P-51 as having a considerable amount of time "pointing backwards", which is as mtnman pointed out a poor depiction. In essence the maneuver is a snaproll with a strong yawing momentum caused by a hard rudder input and momentum.

 A "normal" snaproll would merely resemble an 180 degrees aileron roll, albeit considerably accelerated than usual, whereas the maneuver WW and dtango did (and presumably by the two P-51 pilots as well) partially resembles a barrel roll.

 With the sudden pull of the stick and kick of the rudder the aircraft "snaps" violently at the apex of the "barrel roll" with some amount of yawing momentum, which at certain angles gives off the illusion that the plane is travelling rearwards - but actually does not, as demonstrated by dtango's "flat plate".

 This is supported by the actual AAR provided by the pilots, where they themselves who initiated the maneuver, identify it as a "snaproll".


2) There are a plethora of actual footage of various warplanes, as well as airshowplanes, doing essentially the same maneuver as portrayed by WW and dtango, in YouTube. The same maneuver can be observed in some of the links I've provided, which contains an actual footage of RC planes doing it, also with a simulated footage complete with graphical descriptions explaining just what kind of flightpath the plane travels through.

 The only difference would be the arc, width, and the severeness of the yawing motion as the plane snaps into a sudden roll seemingly resembling a barrel roll - hence, the reason why I've said it is "already well known amongst real pilots".

 

 There is no 'anomaly'. The plane snaprolls as expected, except it isn't flying straight and level as it does it.

[Charge]

"The "Dogfights" episode portrays the spinning phase of the P-51 as having a considerable amount of time "pointing backwards", which is as mtnman pointed out a poor depiction."

I don't really trust Dogfight series in how they present the maneuvers. I base this view on the numerous films I have seen from them. I agree that something resembling that surely happened but the exact execution of such maneuver is doubtful. In such wild maneuver you cannot be even sure where your eyes are pointing so if you see the pursuers nose you might see if from any angle your head happens to be if it happens to point at the pursuer.

If the depicted maneuver did happen it probably happened in quite a slow speed and such a quick recovery was a fluke, not something you can easily reproduce, or even want to.

-C+

PS. http://www.wwiiaircraftperformance.org/mustang/P-51B-Spin-Tests.pdf

[Kweassa]

If the depicted maneuver did happen it probably happened in quite a slow speed and such a quick recovery was a fluke, not something you can easily reproduce, or even want to.

 I'd agree to that upto a certain point.

 Among the two depictions Cpt. Bryan, in his last-ditch attempt in a wild snaproll, lost control of the plane and fell straight downwards. Widewing, in one of his films, also loses control of his plane after the desired motion, and plummets for a while until he regains control. In case of Lt. Candelaria, I sincerely doubt he predicted the turn of events as he went into the maneuver, and my reasoning is his hybrid form of a barrel roll/snap roll was done with wide arc/radius as the enemy overshot, which landed him a one in a million shot.

 In any case, (IMO) there's a reason why "snap roll" type of maneuvers never really makes it among the list of "official" ACM, since it is a result of a accelerated stall, rather than a plane flying within the the limits of its envelope. It is because the plane steps out of the envelope, that it rolls so fast, way faster than its normal rolling speed, in the first place. And as bozon once said, and I quote, "anything can happen when normal airflow is lost over the plane".

 However, how a plane reacts under such conditions, whatever dangers there may be, is not entirely random. In some cases it is predictable, and "snap rolling" is a technique used by many pilots both in the game, and in real life. Would it be so hard to believe if it was just a normal snap rolling? People do it all the time.

 
 Something not easily reproduced, I'll agree to that. However, it's not as if you are deliberately crashing your plane into a mountain. In both cases, Cpt. Bryan and Lt. Candelaria mentions they've practiced it before. How'd they practice such if it was something unreproduceable in the first place?

[Hack9]

Wow! Entertaining thread!  I've been awol from ah for far too long evidently.  Look what I've been missing!

A brisk salute: Excellent films and airplane handling! Great stuff.

Also: Lots of excellent historic and technical knowledge has been exhibited in this thread, so I'm hoping some of you would like to comment authoritatively on the any of the following.

All this talk of snap rolling P-51s made me chuckle as I recalled reading something in a P51 pilot's manual telling pilots NOT to try to snap roll the airplane.  The fine AH films in this thread suggest it can be done...or at least something very similar to a snap roll can be done with our flight model...with practice. And of course, Capt. Bryan specifically mentioned performing a snap roll in his AAR.  Yet, the P51 manual issues an official prohibition of the move.

I looked up the following quote from AAF Manual 51-127-5, (revision published 15, Aug 1945), p78 just to check and see if I was remembering correctly and sure enough:

"The aerodynamic characteristics of the P-51D are such that snap rolls cannot be satisfactorily performed.  This has been proved by a long series of test flights.  So don't try any snap rolls in an attempt to show that you're the guy who can do them.  You'll invariably wind up in a power spin - and that's bad.
(Caution: Acrobatics must not be attempted unless the fuselage tank contains less than 40 gallons of fuel.)"

Jumping back to page 77 of the same manual to see what was said about power spins I found:

"Power-on spins are extremely dangerous and must never be performed intentionally under any circumstances....the spin tends to tighten, and there is a rapid loss of altitude.  Recovery control will have no effect on the airplane until the throttle has been completely cut back."

It goes on to describe standard N.A.C.A spin recovery then a few paragraphs later:

"It may take up to six turns to recover from a two to five turn power spin.  In this situation you may lose as much as 9000 feet of altitude."

First question: Does anyone know if this official 'don't snap roll the P51' order dates back to the time of Capt. Bryan's AAR or even before that? The manual I have is a revision that was essentially very late or post war as dated August '45.  I wonder if earlier manuals say the same thing about snap rolls in the P51.

Secondly, does anyone know of technical and/or historic reasons other than those quoted above from the manual as to why snap rolls would be specifically excluded from authorized acrobatic maneuvers for the aircraft? The manual suggests that the power-on spin and required recovery are the main reason for the prohibition. The balance and behavior of the remaining fuel load is also suggested as a possible complicating factor to acrobatics in the Mustang (the < 40 gallon rule.)  Anything else we should know about the P51D and its instabilities?  Were there specific structural flaws in the Mustang that added further reasons to avoid snap rolling the aircraft?

If the anti-snap roll warning was part of Capt. Bryan's training, he seems to be thumbing his nose at that very manual and the notion that the P51 can't be snap rolled 'satisfactorily' in his AAR.  He not only mentioned performing a snap roll,  but claimed to do it as a combat maneuver.  I imagine he probably did do it, and surely others at least tried it when possible despite any official warnings.  He and other pilots likely tried to squeeze every bit of performance out their aircraft, and tried to learn every trick in the book to get the upper hand, knock down e/a get home alive. I know I sure would have.

We get a brand new, perfectly tuned and maintained aircraft every time we up in AH, so it's not that I'm worried about popping a few rivets or becoming a lawn dart while practicing.  Just curious from a historic point of view.

Thanks for your time,
Hack9

[dtango]

I believe the intent of Widewing's post was to encourage people of the value of spending time learning the nuances of any particular plane in Aces High and flying it to the limit.  I posted the flat plate as an example of that.  Nothing more, nothing less.  

That's why I was and still am loathe to get dragged into a FM discussion about it.  I've avoided commenting on the FM of the maneuver.  With the flat plate, we are talking about a complex post-stall maneuver.  The airplane is out of the envelope of normal flight and there is no simple way to mathematically evaluate it comparitively that I know of short of using navier-stokes equations.

The flat plate is a type of lomcevak maneuver where I'm also using the effect of the running propeller to induce particular motions while the airplane is temporarily in a post-stalled state.  We know lomcevak's are real maneuvers.  If I had doubts about the maneuver, it wouldn't be if the Mustang (or any other WW2 fighter) could initiate some type of lomcevak tumble like the flat plate, but if it could structurally survive it or not.

==============
Charge,

You obviously didn't appreciate any of my comments on wind tunnels .  I can't blame you for not following the entire thread to see why I even mentioned anything about them to begin with.  It had nothing to do with proving or disproving that the Mustang could perform the maneuver.  I was simply trying to clear up a misconception about scale models in wind tunnels.

Tango, XO
412th FS Braunco Mustangs

[Fruda]

Originally posted by Krusty
You can't be serious. The laws of physics are the same for an elephant falling and a feather, but they forces ACTING on said objects are so far different as to be uncomparable.


Same for RC planes and real planes. You can NOT compare them in a serious manner.

Have you ever seen a Yakovlev at an airshow? They do stunts like this all the time, though much more precise because the airframe is made exactly for aerobatics.

Just because a Mustang can flop around in the air doesn't mean it can hover on its propeller. Physics isn't symmetric...

[Charge]

"his hybrid form of a barrel roll/snap roll was done with wide arc/radius as the enemy overshot, which landed him a one in a million shot."

I can agree with that.

I was trying to point out that Mustang had an issue why rudder was not recommended in slowing down the aircraft but I don't understand what it actually is. Was it to prevent the pilot from over-stressing the rudder construction since the fuselage has such a big side area to limit the slip or is the airframe prone to accelerated stall even with use of rudder? It may well be that despite the big side area the aircraft is somewhat unstable so that it really can enter a rather peculiar accelerated spin (notice the difference between B/D) but how could it instantly recover from it? The speed may be a rather deciding factor in such case considering keeping the controls effective but the manual (Hack's post) suggests that power on stalls are the most dangerous.  Maybe it really can be safely executed by suddenly cutting the power in turn and pulling from the stick so that the a/c snap rolls and assisting a bit with rudder the resulting spin happens already in horizontal plane and opposite controls are able to get it under control until a vertical spin has time to develop. Power back on and you a back in the game.

But instantly recovering from a spin where you go tail first for a while? I find it very very hard to believe such maneuver to be possible with any WW2 fighter. Weight, G limits, COG vs COL or more precisely weight division in fuselage in relation to lifting or controlling forces and airfoil design prevent this IMO.

***

AFAIK the point in Hartmann maneuver was to cause the shooter to be forced to push negative Gs so that any kind of accurate shooting was impossible since you were hanging from your harness.

***

Finnish pilots did practice a maneuver called "impossible" or "senseless" where you deliberately entered a totally uncontrolled stalled neg G flight state from slow speed by pushing the stick e.g. foward left and stomping the opposite rudder fully down (IIRC), but the recovery took time and it was also considered a last resort maneuver just to get you a second chance if the assailant is about to get a sure kill. In training it was done with a trainer which had a reputation of being quite dangerous in its extremes.

-C+

[gripen]

Originally posted by Charge
Finnish pilots did practice a maneuver called "impossible" or "senseless" where you deliberately entered a totally uncontrolled stalled neg G flight state from slow speed by pushing the stick e.g. foward left and stomping the opposite rudder fully down...

"Älytön" - literally tranlated as "senseless "etc.  is just another name for the snap roll.

Generally dtango's film shows considerably yawed snap roll, reminds the flat spin.

[AquaShrimp]

At low speeds, the P-51 had very poor yaw stability.  This is why the US Navy did not adopt the P-51 for carrier use.  Once the P-51H was developed, with its much larger vertical fin, the yaw stability improved dramatically.

[nickf620]

Originally posted by DiabloTX
Candelaria's move reminds me of the "death blossom" from The Last Star Fighter movie, circa 1984.