Sorry, I thought I was focusing on the failures, not the basics.

Won't happen again.

Where do you make the 'Pop', Drag?

Is there a specific audience to address?

I don't buy the whole aileron induced stall-flick. It's going to take an almighty pull and a lot of G to get close to the stall flat out, clipped wings or not. Running figures conservatively, a 130mph Vs would give at least 14G to get a stall at 500mph - you don't accidentally pull 14G because you got a bit excited rounding a pylon! Alternatively, at 5G, the stall would be a smidge under 300mph. To put it another way, if the clipped wings were going to put it that close to a stall they wouldn't be clipped. Flying around on the back of the drag curve isn't fast.

The video really isn't that clear, half the artefacts could be down to the camera.

The underside of the wing will see pretty much the same pressure even if you stall - the separation of airflow is from the top surface. No reason for the bottom skin to 'balloon'. I don't see any nose drop either, I see the aircraft react to the lift vector being turned further round towards the ground. No real visible yaw either, and any yaw generated by an asymmetric stall will tend to perpetuate the condition, not recover it. Nor do I see the torsion, but flicks do exert a tremendous load on the tail feathers.

I also think it's a little presumptuous to claim the roll rate is higher than standard, it may or may not be: the clipped wing will aid roll, but the ailerons are tiny compared to the original where they go to the end of the wing - so there's 10 foot less aileron too.

Trim was most likely nose down (the earlier posted photo from another flight supports that), or at least we can say that at high speed the a/c would have required a significant nose down input.

WRT the Oil Canning: Assuming the photo is from the same flight, it is significantly before the incident - because it is on the right side (which is pointed to the sky mid turn), and the tailwheel is stowed. Interesting, but I don't know what it means, if anything.

I don't really want to make guesses, but my money's on a trim failure precipitating the wobble. The pick up of the left wing was probably completely instinctive, whatever caused it, and probably the last deliberate action in the aeroplane.

Dont know how else to make folks aware of these pictures, they are pretty incredible

Ghost photo w/out trimtab - Page 12 - Aviation Airshow Air Race Photography Discussion

post 114


Ok, I realize I'm new here so I hope I'm not overstepping. Nevermind my lack of knowledge regarding all of this. But here it goes. About three days ago I sat down and did my version of a timeline/order of events based on the slow-mo video. Alot of what you folks have said have really proven what I was thinking. But I have a few questions, observations and personal theories on a few things.
a. Regarding the pics of the oil canned fuselage, I remember the original post, but I'll be if I can find it again....I believe it was taken in the VOS, and I personally think that it may be somewhat normal for GG as I have seen another photo with it from 2010 and without the scoop for support, who knows what effect that had on that area.
b. I have noticed on various other videos GG heading into turns and really looking unstable, is this a function of its tiny ailerons?
c. I am also of the opinion that he was really stretching her legs down the VOS that last time, and wonder just what kind of G's were experienced in 7 and 8 vs. what he had experienced before.
d. I also wonder what are the chances that he was reaching a very critical stage of GLOC (probably not the right term at this point) just as the a/c goes wings vert by cutting a tight corner over 8. And his completely natural instincts took over for a split second to right the a/c, but in the process over corrected and inadvertantly over pulled the mayday manuver putting himself completely out.
e. I subscribe to the pushing him down in the cockpit thus displacing the control stick forward and to the right, and thus commanding the a/c to come out of its climb and roll to the right.
f. Now, in the slow-mo I hear a click....is this the mystery pop....maybe the math wizards out there can guesstimate based on distance, time vs. sound when exactly that pop occurred during the sequence.
g. Does anybody else see vapor below the wings during the initial wing vert and what I consider a slight climb (even though the a/c is 90 degree to the ground it still appears as a climb to me based on the a/c taking on what appears to me as more positive G's.......or is it just reflection?
d. Now for my big question....with the exception of the somewhat level flight in the VOS....why would these a/c require so much nose down trim. To my totally untrained way of thinking that some of this nose up tendency would be beneficial during their long banking turns, it would really give the a/c a feeling of digging into the turn. But that said I have seen a pic of GG with that poor little tab really up in the airstream, also what would the purpose be of not using both, I would think that would put a great deal of torsional stress on the entire elevator system.

OK....mods delete away if need be, or feel free to scold me through a pm. As I said before I dreamed, built, babied, and raced my own cars for 20 years (the dreaming part started when I was 6.....a lonnngggg time ago) so I understand a bit of the mechanical part of this and certainly the competitive aspect of this, although I would never have the scrotal fortitude to do what these cowboys do.

Thanks for your patience with this book of a post. That airplane was just plain sexy....maybe too sexy

Mark1234

I posted a theory earlier that presumed Tab failure causation. This is all conjectural, and if it reads a little too conclusively, my bad.

Earlier on, prior to the snap left, a slight roll is seen to the right. This could result from the loss of Trim Integrity on the left side, as the Tail twisted rightward. This torsion would oil can the fuse in the manner seen, whether the photo is concurrent the upset or no.

The reaction of the pilot would be to roll left, and without knowing his Roll datum, in the circuit, it is not possible to index pilot input from here on.

With an ineffective Tab (it was still attached) and its drag, it wouldn't cause the LOC on its own, imo. But it would certainly instigate some input from Leeward, and well, no one I know has ever been there.......

regards, Bill

Human G Tolerance
 

http://home.comcast.net/~shademaker/GLOC-Threshold.jpg
The above chart is taken from this paper http://csel.eng.ohio-state.edu/voshell/gforce.pdf
The chart shows a typical person's response to sudden g application and what warning might be available of impending loss of consciousness.

Terminology note: I am using the term grayout to describe the loss of the complete visual field without unconsciousness, and the term blackout to describe unconsciousness. They are the terms I remember from my initial training many years ago.

The red line shows a rapid g onset to a high sustained g level resulting in blackout without warning in a few seconds.
The yellow line shows a high pulse g load decreasing to zero g without causing either visual effect or blackout.
The green line shows a slower g application resulting in visual effects after a few seconds(collapse of the visual field to a tunnel) flollowed by grayout and blackout.
And the blue line shows a substantial period of no symptoms followed by visual effects and finally blackout.

In the GG accident, It appears the extremely high g commences in the left bank and within 1.5 seconds, the right roll rate during the pull up commences, probably indicating GLOC.
The pilot of Voodoo Chile is reported to have debriefed his experience as follows:
The pictures showing Jimmy Leeward "missing in the cockpit" probably indicate that he too had his shoulder harness reel unlocked.

Machinbird

From the graph, and counting real time, Leeward was fully 5 seconds into some raunchy pull. With the g telemetry it should be known when he had the most likelihood of passing out.

It isn't unreasonable to consider he passed out and bitched up the stick, Rudder prior to the wobble, snap.

I gather you don't have much experience pulling g.
Your theory has little relevance to someone who has practice in pulling g.
Additionally, your theory is missing a causative factor for the pitch up.

You are the one Pitching a theory that the Pitch UP was caused by aerodynamically set controls, and was uncommanded. Have you changed your mind? Because it fits with an incapacitated pilot early on.

I'm watching an a/c at ~5 g for five seconds, look at your own graph and consider my post again?

If you prefer, call it 3.5 for the same five seconds. Jimmy Leeward was 74 yoa. His circulatory system likewise was 74, and no g suit to keep 02 in his noggin, instead of puddling in his legs. Experience in pulling G may not have compensated for the Physics involved here.

Lyman, With experience and if I was flying, I could pull 5 g without a g suit for a minute, or 6+ g for a minute with the 'speed jeans' on.

Jimmy Leeward was experienced and he was flying. Older isn't always disadvantageous. If he had slight hypertension, he could withstand higher g than a 'young puppy'. What matters was how well he used his muscles to keep blood where he needed it.

You still haven't explained how the trim tab failure could occur as a result of pilot incapacitation, whereas, if the trim tab loses integrity it is no longer providing nose down trim and we already have an example event that shows 10+ g can result. That is sufficient for prompt GLOC.

I don't know what the great mystery here is. He's got roll instability that the other non-modified Mustang does not. He chopped up this airplane and it didn't fly like it should have. Are we surprised? No.

-drl

You make it sound like this is the first time anyone has raced a modified Mustang with clipped wings......

http://www.mustangsmustangs.com/p-51...ousMetal.2.jpg

http://images.rcuniverse.com/forum/u...5856_11603.jpg


http://www.mustangsmustangs.com/p-51...RedBaron.1.jpg

http://www.mustangsmustangs.com/p-51...Stiletto.1.jpg


http://www.mustangsmustangs.com/p-51...s/Strega.1.jpg

Academic I know in the (tragic) circumstances but I'm another one not "buying" some elements of the GLOC graph presented into evidence earlier.

Am I misreading it or it is seriously suggesting that a progressive "squeeze" to 5 g in 5 seconds - the green line, will lead to GLOC?

A further thought - I believe the early ballistic ejection seats could hit 20G plus - not great for the back/neck, but not necessarily an instant bone breaker either...

Machinbird

So incapacitation could have caused an inadvertent input of NOSE UP, which he was pulling anyway? With a marked addition of increase AoA of the Tab, it could easily have been overloaded. Mind you, with VooDoo, we have a prior event, and I take your point. Down to metal fatigue, I'd say that it is likelier that the pilot was fine until the Tab let go. If the Tail was that asym, then a large instability enters in Roll. Also Yaw.

Again, the tab may have led to control input that was not ideal, and who would know just how much of what to input into a broken Tail? The Tailwheel lost its retention somewhere just here, prior to the climb, so it is logical to predict the highest g happened in this roll/reversal sequence.

If the remaining tab was not sufficient to keep the elevators down, they went up (asymmetrically), and could have been an additive input that was responsible for the proposed blackout.

Leeward would have instinctively wanted to climb, besides its the rule, so the 80 degree Pitch Up might have been caused by the pilot afterall?

I am not trying to draw conclusions, perhaps I'll attempt to present things a bit more tentatively.

I draw attention to the pre event G to set the stage for a loss of consciousness with a quick transient, not to establish earlier gloc.

The circulatory system makes accomodations for aging, and it is not conducive to high g manuevering, no matter the musculature. Not sure hypertension applies here. With a fit pump, muscle tone and BMI are important. Your graph tells the story.

Stick Force
 

Let's say you are happily cruising over Stead about 200 feet off the deck in your modified P-51. Your speed is about 490mph and you are trimmed for level flight.

How many pounds of force would you need to pull on the stick to induce a 12 G climb? How about a 21 G climb?

It will be "x" minus"y". Where x = manual pull, and y = loss of NOSE DOWN TRIM, with the croaked Tab. Without the tab, the HS will migrate UP.

Assuming the trim is in fact ND. Any trim at that velocity is a mixed blessing, if in an emergency one wants and needs a vanilla response?

Someone a great deal more familiar may post in?

I read somewhere that GG had only one operational elevator trim tab.

The other tab was fixed.

Is this correct?

Correct? I could not say.

Counterintuitive? Oh yeah.

Here is where I read the trim tab story.

http://www.pprune.org/6721683-post41.html

I see it comes from this forum as well.

the Galloping Ghost......... detailed pix

One trim tab on the left elevator only.

Desert

Que? Is that a make shift Yaw damper as well, then? Cheat to the left, and save on Rudder Drag? Wouldn't that be conducive to torsional vibration on the elevator hinge?

Sounds almost like, cheating.

Besides, if he has ND cranked in when level, he sure does not want it in a steep turn, nothing but drag. NU helps in the turn, so what, is he some trim monkey, constantly adjusting trim to suit attitude? That is a lot of load on/off/transit on the rig. And a LOT of wear. If he's using muscles to overcome the ND and is leaving the tab up in the airstream whilst yanked in a turn, that is just dangerous, and would (could) explain the extreme NU when the Tab croaked.

Quote: Lyman "Wouldn't that be conducive to torsional vibration on the elevator hinge?"

I think that is what I was sort of asking towards the end of my long post. But hadn't considered the vibration aspect, just a simple twisting of the elevators in relationship to each other. I've seen the question regarding the use of only one TT and a reason for it, asked on numerous forums but not ever have I read an inkling of reason for doing it.

Information I've seen on other forums indicates that this might be better stated as one functional trim tab only. I have seen pictures that I will post a link to that indicate the port and starboard elevators are interchangeable on the P-51. When built back up after its substantial overhaul, GG had trim tabs in both positions. The bellcrank on the starboard elevator tab is on the top surface, and on the port elevator tab, the bottom surface. The starboard trim tab may have still been ground adjustable even if that tab was fixed. For pictures of the GG rebuild, see WarbirdAeroPress.com
and
WarbirdAeroPress.com
Wow, what an extensive rebuild!!

The F-16 has Stabilators. They articulate on separate pins that allow deflection in opposite direction, to enhance (to put it mildly!) Roll. They of course deflect in concert, when selected for Pitch only.

If GG had one Tab fixed in ground-only aspect, and the other operable in flight, one gets the 'same' effect, though obviously the poor mans' version. Roll is enhanced along with Pitch trim. I'm going to assume the elevators remain affixed to the single Tube/hinge barrel that carries both, aligned identically.

Interesting trick. Under severe load, one can imagine an asymmetrical span wise loading on this Tube, and the potential for vibration, even flutter, or buzz. The drag of Trim, on the left, is spent on Yaw capture when turning, and makes elegant use of Drag that would otherwise go to waste. If the pilot is flying trim, mechanically, this sytem has some issues relative to load (torsional) on the tube, and on the HS bellcrank, and cables. When back driven, the system would be subject to variable loading, unless damped in some fashion, and this set up would want some serious monitoring.

Unlikely, but possible, is the loss of Elevator continuity, if the actuating frame had a break in the attach to the tube. Since control is asssumed to have been pilot/unavailable anyway, it isn't impossible that the Elevators were flapping in the airstream, following, instead of leading the flight path.

The flight path after the snap looks eerily ballistic, it is too smooth to have controls inputting directional leads.

wrench, I missed your bit about the asym tab purpose, but does this proposition sound in any way applicable?

Thanks for the link. Lots of good photos there:

http://i2.photobucket.com/albums/y17...lipboard06.jpg

http://i2.photobucket.com/albums/y17...ipboard06a.jpg

http://i2.photobucket.com/albums/y17...lipboard01.jpg

http://i2.photobucket.com/albums/y17...lipboard04.jpg

http://i2.photobucket.com/albums/y17...pboard02-1.jpg

Lyman: thanks for the explination, you would think since I spent my racing career turning right to go left, than all of that would make sense to me, but having the right TT fixed still seems backwards to me, but I will take your explanation.

Lost in Saigon: How did you manage to extract those photos? I just ordered a 1/32 kit and they would be a great source of detail, and I would like to save them to my laptop before they disappear. Thanks

Also, new long distance vid, but really shows the pitch up.

It is quite easy to do. Just hit "Print Screen" on your keyboard, and you take a snapshot of what is displayed on your monitor. Then open "PAINT" or a photo-viewing program like "Irfanview"(free download) and hit "Control V" to paste it. You then crop it to size and save the file.

More info: Print screen - Wikipedia, the free encyclopedia

Alt-PrintScreen is better - it just copies the focused application (active window), not the entire screen. There is probably a Mac and Linux equivalent.

-drl

In Ubuntu Linux if you alt print screen it will actually open a image viewer with the captured window in it, you can save straight to disk from that

The thing that niggles me wrt to the single functional trim tab is this statement from the link I posted earlier.

"He was warned about the forces being put on that one tab."

Did the previous incident of trim tab failure not give cause for concern?

I know it's a human trait to believe that it can't happen to you and I hope that the rest of the racers are making suitable modifications to their awe inspiring aircraft.

Incidententally, does anyone know what happened to Learfang, the P51 with Lear jet wings?

Crashed in 1999: P-51 Mustang Survivors: " Miss Ashley " , N57LR - serial #: 87-1002 Sights, Sounds, History.

N57LR plane crash in NV details :: PlaneCrashMap

http://www.mustangsmustangs.us/p-51/...002_05_mk1.jpg

Thanks for that Lost in Saigon.:ok:

Lyman....did you get the chance to look at that 18 photo sequence? Am I mistaken or a does it look like the TT is in major flutter in #7a, if the GG is rolling to its right why are the ailerons showing roll to the left in #15a? or am I just all twisted around? Just curious on your take.

If you have anything with the sort of resolution you allude to, I'd love to see them? PM is good.

thanks wrench

More photos of the tail area:

http://i2.photobucket.com/albums/y17...pboard01-1.jpg

http://i2.photobucket.com/albums/y17...pboard02-2.jpg

http://i2.photobucket.com/albums/y17...lipboard03.jpg

http://i2.photobucket.com/albums/y17...pboard04-1.jpg

http://i2.photobucket.com/albums/y17...lipboard05.jpg

http://i2.photobucket.com/albums/y17...pboard06-1.jpg

http://i2.photobucket.com/albums/y17...lipboard07.jpg

Trying to catch up. Before this tragedy happened, I had been talking to some teams about reducing compressibility drag on the Mustang Unlimteds, so I might have some unique contributions.

Haven't had time to study the video frame-by-frame but can comment in areas. Like everyone here, still putting the pieces together.

- "Could it occur, but not for long enough for the aircraft to actually stall at that G load and relieve itself?"

Dynamic stall can result in higher CLmax than the FAA demonstrated one knot/sec deceleration to the stall by hysteresis. Though on some other boards, there are claims of the telemetry being limited to 8g's. Don't know if we'll get the right number until the report, unless someone takes the time to convert the geometric flight path to g's. Since the tailwheel pops out before wings level, this might not capture the max.

- Remember a report in the past about older people being able to handle g better than the younger ones if they have any hardening of the arteries since the airteries don't expand as much to accept blood. This probably wouldn't matter much at 10+ g's, but the discussion should preclude age.

- Leaning towards the structural failure causing the left wing drop since wake turbulance would be unlikely since the wind was coming from the direction it was and was strong from the flags flying in various videos.

- "Roll Rate on this a/c is rapid, far higher than the factory model with ten feet less span. Similarly, the ailerons are half length, and it would be interesting to know if they were clipped Out/In, or In/Out. This is critical, since ailerons are airfoils, and subject to STALL just as any other."

Roll rate capability is a function of wing span-to-aileron span, and would be reduced due to the clipped wings at the tip, but at these q's, the airplane had plenty of control authority. Ailerons don't stall like wings since the leading edge is protected by the slot, but the upper surface can separate at high enough deflections.

- The racing Mustangs have an aft cg, so the elevator is deflected for nose down moment at race speeds. Some of the guys have changed the incidence to alleviate this requirement. Leeward had the one port trim tab. Voodoo had the elevator shear the torque tube fasteners on the lost trim tab side. Probably from the violent act of the trim tab fluttering and departing.

- The trim requirements in the turns and straights tend to balance out due to the aft movement of the center-of-pressure due to a shock wave forming on the inboard wing at 4 g's in the turn. Haven't analyzed it yet, and Leeeward was banked pretty good in the turn, but 6 or 7 g's probably wouldn't cause Mach buffet, looking at the pressure distribution at 4 g's. Yes, the Unlimteds are seeing compressibility drag due to the original subsonic airfoil selection.

This seems like a forum with informed, and talented individuals, and will try to contribute as I read through the thread.

Roll rate is dependent on wing area/aileron/area, among other things. I see your point, as the area of the wing was not "halved" as was the aileron area. Good point.

Having a shorter wingspan reduces the inertia of the rolling moment? Less energy is needed to start, maintain roll? The aircraft is also less stable in roll.

The rapidity of the wing drop is what captivates me, not the impulse strength of the ailerons. I doubt the snap left was controls induced, more like a wing drop from loss of net lift v/v the right wing? Wake turbulence remains a possibility? Torque from the loss of structural integrity at the Tail?

Clipped wings, quick turns, eh? I am waiting for the next gen Mustang to show up with anhedral?

As to airfoil, the aileron is just a wing with a humongous cuff. And the laminar flow Mustang is sensitive to interruptions in local airflow?

Google for the basic aerodynamic and control theory answers of wings.

Could have been turbulence from ground based items/structures, but to conclude the initial dip was from wake turbulence of the lead airplanes is unwarranted due to the wind conditions. Am sure there are some weather history websites that would have the atmospheric conditions to the hour. For this reason, am leaning toward the left wing drop as being an artifact of the mechanical failure.

Whatever the cause, Leeward did an excellent job of arresting the left roll with the right amount of finesse. Reflexes like a cat from muscle and experience memory developed over the years. If nothing else, he can be remembered for his skill.

In response to the just prior post, that's missing now, on discrete roll rates in the turn;

There's a small right roll rate well before the left wing drop with a slight left roll rate immediately before the left wing drop. Consider these excursions to be positioning corrections. Ailerons are rate controls, as opposed to attitude controls, i.e., once a bank angle is established, aileron deflection is zero to maintain bank angle. The aircraft stopped rolling at wings level indicating the ailerons returned to neutral. The roll resumed during/after the wings level pull up.

Should you include the "slight correction" needed each time to arrest the roll? Could these have been merely imprecise, instead of "positioning" inputs? Not a criticism, certainly, this is a hot a/c.

There is no shame in "hunting" a roll at 475 mph.

Lyman, you're not a pilot, are you. No offense, but what's your background? You seem to have a Wiki knowledge of aircraft, their workings, and their operation.