Big Crash at Reno
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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.
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.
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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
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
Last edited by xmh53wrench; 2nd Oct 2011 at 10:03. Reason: wrong link
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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
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
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Human G Tolerance
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:
...coming down for the start he had unlocked the inertia reel to reach for a switch on the instrument panel...and then forgot to lock it again. After the pitch up, he found himself (in his own words) with his hands on the sandpaper (the floorboard) and the stick stuck between his helmet and shoulder, literally doubled-over in the cockpit.
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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.
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.
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It isn't unreasonable to consider he passed out and bitched up the stick, Rudder prior to the wobble, snap.
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.
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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.
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.
Last edited by Lyman; 3rd Oct 2011 at 03:43.
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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.
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.
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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
-drl
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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...
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...
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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.
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.
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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?
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?
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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?
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?
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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
http://www.pprune.org/6721683-post41.html
I see it comes from this forum as well.
the Galloping Ghost......... detailed pix
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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.
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.
Last edited by Lyman; 3rd Oct 2011 at 23:04.