Big Crash at Reno
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Being a data recorder, I wonder what the intergration time was for that "21g" if it was very small then I would imagine a transient spike might be possible.
Though to have a small intergration time it means recording lots of data, hence more weight due to storage.
Though to have a small intergration time it means recording lots of data, hence more weight due to storage.
I don't know what the unaccelerated stall speed of the Ghost would have been but 21G would require that the airplane be moving at an indicated airspeed of about 4.5 times that speed. The listed speed of 495 mph seems too high to be an indicated speed. Maybe GS or TAS but not IAS or CAS as that would be close to 550 mph in the turn at over 5,000' density altitude. Average lap speeds didn't even approach that, though top speed down the "valley of speed" could. I'd guess the IAS as being closer to 450 mph max. At 450 mph, the unaccelerated stall speed would have to be 100 mph to make the 21G credible. Interesting. I wonder what that stall speed is...
Still some mystery here.
Still some mystery here.
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Is it not the case that the ratio has to be at least 4.5? So any unaccelerated stall of up to 100mph would do it?
(Subject to the disclaimer that I have considerably more experience in arithmetic than aeroplane design...)
(Subject to the disclaimer that I have considerably more experience in arithmetic than aeroplane design...)
Is it not the case that the ratio has to be at least 4.5g?
Edited to add that if the unaccelerated stall speed is greater than 100 mph, the 21G is a stretch. And 21G seems like more than the trim change with loss of tab would produce, but that's pure conjecture. Maybe if there is enough good video to measure the angular change of momentum over time, the load factor can be calculated that way.
Last edited by westhawk; 29th Sep 2011 at 10:45. Reason: Additional comments
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#180 @ 9:00 One sees the actual departure of the trim tab from the airframe. So, "broke off" is not an accurate way to describe the tail damage. It broke, but "off" came later, near the apex of the ascent.
The Roll to wings vertical prior to the climb is interesting in that it may involve other than control surface deflection. Look carefully at the sheet metal on the underside of the wing in the slomo. Either the light is changing, or the under surface is "unloading", losing its dynamic "crush" in a ....STALL?
21G? No comment. Leeward was in high G well before the mini roll left, and may have been impaired/incapacitated before the climb itself.
Them's some very short wings. AoA at the "Roll"? Anyone?
addend. Watch the slomo carefully. As the a/c is "rolling" left, notice the NOSE dropping, alot. The a/c then looks to have recovered itself, and the Pitch Up is dramatic, very quick. So this unusual 'snap' left may have been the port wing dropping in STALL. It would be the one to drop out, as Leeward arrested the left roll 'turn' he had just made, its velocity being slightly less than the right wing, due turn radius, and its aileron increasing its net AoA, drag.
It is the Nose Drop that would have violently overloaded the tail feathers, producing the longitudinal collapse of the tail section evident in the still photo (wrinkling). So if the geometry of the image is accurate, the photo will have been exposed in the split second before 'climb'.
Just as the tail collapsed, it also Pitched the a/c UP. I think the pilot was a passenger after that Pitch change.
At Nose Drop, there would be large negative G. At Reversal into climb, large positve. Add Roll, and Yaw, and the human body may have exceeded its physical limits, as well as the tail.
The Roll to wings vertical prior to the climb is interesting in that it may involve other than control surface deflection. Look carefully at the sheet metal on the underside of the wing in the slomo. Either the light is changing, or the under surface is "unloading", losing its dynamic "crush" in a ....STALL?
21G? No comment. Leeward was in high G well before the mini roll left, and may have been impaired/incapacitated before the climb itself.
Them's some very short wings. AoA at the "Roll"? Anyone?
addend. Watch the slomo carefully. As the a/c is "rolling" left, notice the NOSE dropping, alot. The a/c then looks to have recovered itself, and the Pitch Up is dramatic, very quick. So this unusual 'snap' left may have been the port wing dropping in STALL. It would be the one to drop out, as Leeward arrested the left roll 'turn' he had just made, its velocity being slightly less than the right wing, due turn radius, and its aileron increasing its net AoA, drag.
It is the Nose Drop that would have violently overloaded the tail feathers, producing the longitudinal collapse of the tail section evident in the still photo (wrinkling). So if the geometry of the image is accurate, the photo will have been exposed in the split second before 'climb'.
Just as the tail collapsed, it also Pitched the a/c UP. I think the pilot was a passenger after that Pitch change.
At Nose Drop, there would be large negative G. At Reversal into climb, large positve. Add Roll, and Yaw, and the human body may have exceeded its physical limits, as well as the tail.
Last edited by Lyman; 29th Sep 2011 at 11:43.
I would think that from the video ,at Pylon 7,that GG hit wake vortex from Strega and Voodoo,who were approximately 4-5 secs ahead,GG having overtaken `R-Bear at this point.That may have triggered the failure of the left tab,the Mustang has two trim tabs,but there does appear to be a difference in deflection,looking at the `oil-canning` pic.#207 ,and the other left -side shot.#162.
The EAA article mentioned earlier,Jimmy says the ac stalls about 130 mph,but cleanly. I would estimate the wing area at about 175 sq.ft,and at about 8000lbs a wing loading about 46-50 lbs/sq.ft.,so I would guess a peak `g` of about 15.. but what is telemetered depends also on the position relative to the Co G.
Whilst it has been poo-pooed ,the seat may have failed,depending on its mountings; it also looks from the other slideshow link,that the harness mounting is somewhere behind the seat and below the pilot` shoulders,ideally should be above/level,and attached to the main a/c structure...certainly used to be for F1 air-racing,when I were a lot younger..Similarly, it could be that ,being forced down and forward,JL could have been struck by the control column,in the chest/face/neck.
Just another point about the `oil-canning`,in that particular area is where the structure normally houses/supports the radiators; however I would be surprised if the area had not been strengthened to accomodate their removal.
I would suspect that next year there may be aircraft with `trimmable stabilisers`back in vogue.
As an aside ,I think Matt Jackson should keep it zipped until the investigation is over..
The EAA article mentioned earlier,Jimmy says the ac stalls about 130 mph,but cleanly. I would estimate the wing area at about 175 sq.ft,and at about 8000lbs a wing loading about 46-50 lbs/sq.ft.,so I would guess a peak `g` of about 15.. but what is telemetered depends also on the position relative to the Co G.
Whilst it has been poo-pooed ,the seat may have failed,depending on its mountings; it also looks from the other slideshow link,that the harness mounting is somewhere behind the seat and below the pilot` shoulders,ideally should be above/level,and attached to the main a/c structure...certainly used to be for F1 air-racing,when I were a lot younger..Similarly, it could be that ,being forced down and forward,JL could have been struck by the control column,in the chest/face/neck.
Just another point about the `oil-canning`,in that particular area is where the structure normally houses/supports the radiators; however I would be surprised if the area had not been strengthened to accomodate their removal.
I would suspect that next year there may be aircraft with `trimmable stabilisers`back in vogue.
As an aside ,I think Matt Jackson should keep it zipped until the investigation is over..
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This is a question, not an assertion; Believing that the trim tab failure caused a very unusual and uncontrollable pitch change, would it be possible for the aircraft to sustain a very brief pitch up to record the stated 21G? Could it occur, but not for long enough for the aircraft to actually stall at that G load and relieve itself? Like gust loading, could an event like this occur, cause various loads and effects to the aircraft, but not be sustained long enough for the aircraft to actually stall?
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Pilot DAR
The first evidence of trouble is the anomalous roll left, and I am having trouble matching that up with a fouled or broken TT. There is some evidence of Pitch change prior, and that could be W/T, but again, I Think the snap left and Nose Down shows a high speed STALL. If you look at Pitch just after this slight roll enhancement, you'll see a pronounced drop in the Nose. The Ghost carries this Pitch down only briefly, and starts its ascent right away.
I think Jimmy was tighter to the pylon than Strega, Voodoo, and would have passed their W/T 'above' (actually, "inside"), as it settled outward. This upset looks very much like a too-tight turn, a quick STALL, and autonomous recovery. The fuselage distortion is quite indicative of an overloading downward moment, a result of exposing the tail to extreme aspect at this remarkable speed.
For me, it is easier to see the Trim Tab fracture as a result of, rather than a cause of, the climb. Again, it was in the airstream in the up position to begin with, and its exposure would have been at an even steeper AoA than the HS in the brief STALL aspect. The elevator would have seen some airstream relief in this aspect, and the HS would have been the source of the energy that overloaded the Fuselage in the area of the Buckled skin.
To answer your question, if the NOSE drops, the G would be quite negative, and a starting point for the ensuing positive G associated with the climb. As a reversal, I consider these values to be additive, and the damage resulting quite alarming. Both to the pilot and the airframe.
21G? No comment.
The first evidence of trouble is the anomalous roll left, and I am having trouble matching that up with a fouled or broken TT. There is some evidence of Pitch change prior, and that could be W/T, but again, I Think the snap left and Nose Down shows a high speed STALL. If you look at Pitch just after this slight roll enhancement, you'll see a pronounced drop in the Nose. The Ghost carries this Pitch down only briefly, and starts its ascent right away.
I think Jimmy was tighter to the pylon than Strega, Voodoo, and would have passed their W/T 'above' (actually, "inside"), as it settled outward. This upset looks very much like a too-tight turn, a quick STALL, and autonomous recovery. The fuselage distortion is quite indicative of an overloading downward moment, a result of exposing the tail to extreme aspect at this remarkable speed.
For me, it is easier to see the Trim Tab fracture as a result of, rather than a cause of, the climb. Again, it was in the airstream in the up position to begin with, and its exposure would have been at an even steeper AoA than the HS in the brief STALL aspect. The elevator would have seen some airstream relief in this aspect, and the HS would have been the source of the energy that overloaded the Fuselage in the area of the Buckled skin.
To answer your question, if the NOSE drops, the G would be quite negative, and a starting point for the ensuing positive G associated with the climb. As a reversal, I consider these values to be additive, and the damage resulting quite alarming. Both to the pilot and the airframe.
21G? No comment.
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In an earlier post, I remarked that looking at the crash video, if the speed is about 500mph and the time from horizontal flight to vertical is about 2.5 seconds, a back of the envelope calculation suggests approx 15g initial G.
That's no aerodynamics calculation, purely on the physics of something at a certain speed changing direction in a certain amount of time. 21g may have been a peak figure for a short amount of time.
That's no aerodynamics calculation, purely on the physics of something at a certain speed changing direction in a certain amount of time. 21g may have been a peak figure for a short amount of time.
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The video shows a sudden and extreme G whilst the a/c is wings vertical,
and while horizontal flight path is evident, the G is experienced 90 degrees out of phase, relative to path vector. It is at this time the T/W starts to come out. So I think it important to consider that the G loads were not consistent, they were experienced in rolling, yawing aspect, not just in "Climb". They also differed in Negative/Positive direction. It also would support some uncommonly high G values.
I think the camera is a constant, it shows no vibration, and the lighting, while variable, cannot account for the Torsional fuselage movement v/v the wings, and there is evidence of sudden and out of rig airframe displacement. As a/c is rolling out to Right, Note both elevators in extreme ND. This is either the result of dramatic aspect increase to the airstream via pilot input, or the result of exposure to dramatic airflow over the top of the HS, resulting from sudden NOSE DOWN. It is too rapid for Pilot input, so I think the latter. Bear in mind, that if the control surfaces are being back driven to this extent, continuity with the stick may have been lost. As the STALL is recovered, the elevators go neutral, then deflect up, again from airflow, not PILOT, resulting from the climb. As speed is lost, the controls seek neutral, and the aspect becomes gentle, as if the pilot were in control.
and while horizontal flight path is evident, the G is experienced 90 degrees out of phase, relative to path vector. It is at this time the T/W starts to come out. So I think it important to consider that the G loads were not consistent, they were experienced in rolling, yawing aspect, not just in "Climb". They also differed in Negative/Positive direction. It also would support some uncommonly high G values.
I think the camera is a constant, it shows no vibration, and the lighting, while variable, cannot account for the Torsional fuselage movement v/v the wings, and there is evidence of sudden and out of rig airframe displacement. As a/c is rolling out to Right, Note both elevators in extreme ND. This is either the result of dramatic aspect increase to the airstream via pilot input, or the result of exposure to dramatic airflow over the top of the HS, resulting from sudden NOSE DOWN. It is too rapid for Pilot input, so I think the latter. Bear in mind, that if the control surfaces are being back driven to this extent, continuity with the stick may have been lost. As the STALL is recovered, the elevators go neutral, then deflect up, again from airflow, not PILOT, resulting from the climb. As speed is lost, the controls seek neutral, and the aspect becomes gentle, as if the pilot were in control.
Last edited by Lyman; 29th Sep 2011 at 15:57.
That's no aerodynamics calculation, purely on the physics of something at a certain speed changing direction in a certain amount of time. 21g may have been a peak figure for a short amount of time.
Good point. It's possible that between the video and the telemetry a reliable model of the events can be reconstructed if common time references can be worked out. The vehicle recorders lab at NTSB has an admirable success rate in this area, so I wouldn't rule it out.
It will interesting to see what investigative documents are posted on the E-docket library when they get to it. (nothing yet as of today)
As an aside ,I think Matt Jackson should keep it zipped until the investigation is over.
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Do you see it?
I've been looking over the video posted by Knot4u in post #181 and there seems to be some activity around the elevators during the brief left roll at the beginning of the accident sequence. It is very fast, but to me, the outline of the elevator trailing edges becomes briefly asymmetrical and the port elevator seems to move up sharply coincident with the left roll. The motion is what is catching my eye, but when I stop frame, the contrast is not good enough to be sure of anything.
Other significant items visible are the tail wheel dropping just after the aircraft rolls wings level and begins to pull up.
If you watch the trailing edge of the port elevator during the pull up, you can see the trim tab begin to break loose and then separate, roughly at the time the top of the aircraft is pointed at the camera.
Just a personal opinion here, but the initial wings level at pull up seems to be the result of lateral control input, and the beginning of right roll shortly after commencement of the pull up probably marks the beginning of GLOC. The pull up itself was the result of changed aerodynamic configuration and was not commanded.
If 21 g acceleration were to be generated, it would have to be an impulse. Sustained 21 g would almost certainly fail the engine mount. They just don't build that much safety factor into aircraft.
There are a few "telemetry reports" on the web that are at variance with the telemetry report with 21 g of acceleration.
Here is one from the bearhawkgroups.com website dated 9-23-2011:
It may be that these reports can co-exist and merely report different moment's telemetry data.
I view the entire flight path from pull up to impact as most nearly representing a high g barrel roll, and there was no significant slacking of g over the top. The curvature in flight path was extreme and continuous to my eye.
Those predicting a broken neck for the pilot as a result of the high g, are probably wrong. One of our F-4's snatched 12.5 g which greyed the crew out but they suffered no lasting effects from the g exposure. The F-4 needed a lot of rivets replaced in the wings and tail though. The human body is very tough.
Other significant items visible are the tail wheel dropping just after the aircraft rolls wings level and begins to pull up.
If you watch the trailing edge of the port elevator during the pull up, you can see the trim tab begin to break loose and then separate, roughly at the time the top of the aircraft is pointed at the camera.
Just a personal opinion here, but the initial wings level at pull up seems to be the result of lateral control input, and the beginning of right roll shortly after commencement of the pull up probably marks the beginning of GLOC. The pull up itself was the result of changed aerodynamic configuration and was not commanded.
If 21 g acceleration were to be generated, it would have to be an impulse. Sustained 21 g would almost certainly fail the engine mount. They just don't build that much safety factor into aircraft.
There are a few "telemetry reports" on the web that are at variance with the telemetry report with 21 g of acceleration.
Here is one from the bearhawkgroups.com website dated 9-23-2011:
Telemetry downloaded from Galloping Ghost revealed an 11g pull up, fuel flow interrupted on the way up, and then the engine restarted when fuel flow
resumed at the top of the arc. The aircraft was making 105 inches of MP(Manifold Pressure) on the way down.
resumed at the top of the arc. The aircraft was making 105 inches of MP(Manifold Pressure) on the way down.
I view the entire flight path from pull up to impact as most nearly representing a high g barrel roll, and there was no significant slacking of g over the top. The curvature in flight path was extreme and continuous to my eye.
Those predicting a broken neck for the pilot as a result of the high g, are probably wrong. One of our F-4's snatched 12.5 g which greyed the crew out but they suffered no lasting effects from the g exposure. The F-4 needed a lot of rivets replaced in the wings and tail though. The human body is very tough.
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Machinbird
Howdy. The 'add' roll left, at the moment one expects a roll right for level, is consistent with a wing drop on the left. With input right aileron the left aileron drops into the airstream, creates drag (lift) whilst the right aileron tucks up and lessens drag on the right wing. As you know, of course.
Is it possible this was a STALL? I pick up a NOSE drop after the wings reach vertical, and quickly followed by regain of lift, and NOSE up.
When the tail comes back into view, there is a marked torsional sequence of the Tail Feathers relative to the Fuselage, likely caused by asym downforce after the TT broke.
I think the TT broke off as a result of drag, past critical stress, aiw. The Trim Tab loss is not on its own sufficient to explain, with these other clues apparent.
This Torsion would explain the buckled skin in the still photo, but so would a Nose Drop post stall.
Keep after the video, I think you will see rapid and extreme Pitch aspect changes, coincident and following the short snap to left. This Pitch is certainly what caused the TW to drop out, since clearly it was dropping out before the climb.
This is suggestive to me of the massive g load at this point in the sequence, prior to 'climb'. Carefully watch the entire airframe as it reacts to the rolling, it is in extreme distortion, the elevators and wing undersides are distorted radically, and the flight path is 'shaken' in the camera lens.
Let me know if you cannot see the Torsional flexion in the tail relative the fuselage, I can find the exact frame, I think.
Ah, the Phantom
So, for the rest of us, shouldn't we be looking for a reason the left wing drops out? Instead of why a Trim Tab let go? The 'Roll' follows the precise timing for a reversal into Right Roll, and if the rest of you can't see the aileron on the left wing dropping down, I think I see it. What does a wing do when it is asked for more lift at critical Lift? It Stalls, drops, and induces a Nose Drop in Roll, with Yaw. All of these quite visible in the video.
The other explanation is that the Tail, having lost a tab, imparts twist into the fuselage, and this causes the unwanted Roll Left. This is evident from the video, but did it cause the roll back to the Right? The twist is clockwise as seen from the back, consistent with a loss of downforce on the left HS. Depends on the position of the broken Tab. Did Leeward have ND cranked in, or NU? And did the tab break as a result, or did it cause, the upset?
Pretty powerful Tab.
Howdy. The 'add' roll left, at the moment one expects a roll right for level, is consistent with a wing drop on the left. With input right aileron the left aileron drops into the airstream, creates drag (lift) whilst the right aileron tucks up and lessens drag on the right wing. As you know, of course.
Is it possible this was a STALL? I pick up a NOSE drop after the wings reach vertical, and quickly followed by regain of lift, and NOSE up.
When the tail comes back into view, there is a marked torsional sequence of the Tail Feathers relative to the Fuselage, likely caused by asym downforce after the TT broke.
I think the TT broke off as a result of drag, past critical stress, aiw. The Trim Tab loss is not on its own sufficient to explain, with these other clues apparent.
This Torsion would explain the buckled skin in the still photo, but so would a Nose Drop post stall.
Keep after the video, I think you will see rapid and extreme Pitch aspect changes, coincident and following the short snap to left. This Pitch is certainly what caused the TW to drop out, since clearly it was dropping out before the climb.
This is suggestive to me of the massive g load at this point in the sequence, prior to 'climb'. Carefully watch the entire airframe as it reacts to the rolling, it is in extreme distortion, the elevators and wing undersides are distorted radically, and the flight path is 'shaken' in the camera lens.
Let me know if you cannot see the Torsional flexion in the tail relative the fuselage, I can find the exact frame, I think.
Ah, the Phantom
So, for the rest of us, shouldn't we be looking for a reason the left wing drops out? Instead of why a Trim Tab let go? The 'Roll' follows the precise timing for a reversal into Right Roll, and if the rest of you can't see the aileron on the left wing dropping down, I think I see it. What does a wing do when it is asked for more lift at critical Lift? It Stalls, drops, and induces a Nose Drop in Roll, with Yaw. All of these quite visible in the video.
The other explanation is that the Tail, having lost a tab, imparts twist into the fuselage, and this causes the unwanted Roll Left. This is evident from the video, but did it cause the roll back to the Right? The twist is clockwise as seen from the back, consistent with a loss of downforce on the left HS. Depends on the position of the broken Tab. Did Leeward have ND cranked in, or NU? And did the tab break as a result, or did it cause, the upset?
Pretty powerful Tab.
Last edited by Lyman; 30th Sep 2011 at 19:06.
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I can't question your opinion re: the pilot's spine, but the environment in the P-51 is not conducive to survival so much as it is to success. I certainly don't criticize your experience in the F-4.
Here, there is a possible transient load of 21g. Almost twice that your buds survived. He was ok before the Roll, we assume. There is no provision for helmet anchoring a la NHRA, and the straps are less than useless in regimes outside their design, which is mostly for straight and level. If you pick up the PITCH changes, the distortion of the airframe, the TW loss of stow, the Rolling moment, and the YAW, then consider he is wearing coveralls, tennis shoes, and sports a brain bucket built for visibility, I don't like the chances for his spine to survive.
But. It is moot. Grey is enough to put this aircraft into the asphalt. Not even grey, for that matter. The stick is long, and wants deliberate and accurate movements. It is alive. Moving it in 3G is not without its challenge.
Here, there is a possible transient load of 21g. Almost twice that your buds survived. He was ok before the Roll, we assume. There is no provision for helmet anchoring a la NHRA, and the straps are less than useless in regimes outside their design, which is mostly for straight and level. If you pick up the PITCH changes, the distortion of the airframe, the TW loss of stow, the Rolling moment, and the YAW, then consider he is wearing coveralls, tennis shoes, and sports a brain bucket built for visibility, I don't like the chances for his spine to survive.
But. It is moot. Grey is enough to put this aircraft into the asphalt. Not even grey, for that matter. The stick is long, and wants deliberate and accurate movements. It is alive. Moving it in 3G is not without its challenge.
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Right roll!
Check closely - just before the sudden left roll, it seems to me the plane is trying to roll RIGHT, very slight, almost imperceptible - but definitely there. In particular, just before tucking the left wing under, it seemed the right rolls were about to get out of hand so he overcorrected with left roll INPUT, and then snap - too late.
In other words, he's in a fast steep turn with highly modified aerodynamics for his airplane, and it has basically stopped flying normally and is trying to roll right - probably because the outer (right) wing is stalled. It's in a high-speed stall induced by too much speed through a turn.
-drl
In other words, he's in a fast steep turn with highly modified aerodynamics for his airplane, and it has basically stopped flying normally and is trying to roll right - probably because the outer (right) wing is stalled. It's in a high-speed stall induced by too much speed through a turn.
-drl
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deSitter
There is that, and it comes at a reasonable point in the turn for the pilot to start rolling out level for the show center pass. A Right Roll involves deflection of ailerons, left down, right up. this changes the lift and load on each wing. If the left wing exceeds its critical Lift, it will STALL, and the a/c will now reverse, and Roll Left. It is not a good thing, because it imparts Yaw to the airframe, and enormous loads on the Tail, and Heavy engine (see Machinbird, above). As the Nose drops, (increases the radius of the "turn"), speed/Lift is regained and the a/c (wing) starts to fly again. This is too quick for it to be under the pilot's control, it is simply what aircraft do. The upside is that the a/c recovers aero flight on its own. The downside is it overreacts, and starts a....phugoid. So the climb after the loss of the TailWheel structure was likely a natural, and the roll, descent at the top was a bottom wave of the phugoid.
If you look carefully at the underside of the a/c, you will see the ambient lighting flaring on the skin. This is not to do with the light, but with the orientation of the skin itself. This a/c, like most others, is basically a balloon when flying through the air. Pressure from the airstream forces the skin inward against its formers, and substructures, and a balance is reached relative to the speed, and attitude of the a/c. When a deviation in flight path or airloads occurs, the skin responds, as does the structure beneath it. A Stalled wing, for instance, will unload the skin and change the way the light reflects upon it. The a/c effectively, "bulges" where the pressure has released, and this is evident, along with a startling re-orientation of the airframe with the airstream, what you see as an emphatic 'wobble', producing large G deviations from "Normal".
This "Snap" roll left is not commanded, and it is definitely not reversed, by the pilot. It is far too quick to have been input by Leeward. I am magnifying the video to see if I can capture the Left aileron bulging in to the airstream at the TE, but so far...
Can this event have been instigated by the Trim Tab failure? Possibly. It would have also caused a Pitch UP, and an adverse and torsional roll also.
The Tail is seen rebounding from this torsion in a dramatic out of rig aspect with the wings, look closely, and see the airframe rock and roll with this out of rig condition. (It is quite brief, if it had continued, the a/c would likely have come apart at this point.) This misaligned and reorienting event may have produced what was heard as a pop. It is not impossible some substructures broke, or fractured. It may have been the TailWheel snapping away from its lock.
There is that, and it comes at a reasonable point in the turn for the pilot to start rolling out level for the show center pass. A Right Roll involves deflection of ailerons, left down, right up. this changes the lift and load on each wing. If the left wing exceeds its critical Lift, it will STALL, and the a/c will now reverse, and Roll Left. It is not a good thing, because it imparts Yaw to the airframe, and enormous loads on the Tail, and Heavy engine (see Machinbird, above). As the Nose drops, (increases the radius of the "turn"), speed/Lift is regained and the a/c (wing) starts to fly again. This is too quick for it to be under the pilot's control, it is simply what aircraft do. The upside is that the a/c recovers aero flight on its own. The downside is it overreacts, and starts a....phugoid. So the climb after the loss of the TailWheel structure was likely a natural, and the roll, descent at the top was a bottom wave of the phugoid.
If you look carefully at the underside of the a/c, you will see the ambient lighting flaring on the skin. This is not to do with the light, but with the orientation of the skin itself. This a/c, like most others, is basically a balloon when flying through the air. Pressure from the airstream forces the skin inward against its formers, and substructures, and a balance is reached relative to the speed, and attitude of the a/c. When a deviation in flight path or airloads occurs, the skin responds, as does the structure beneath it. A Stalled wing, for instance, will unload the skin and change the way the light reflects upon it. The a/c effectively, "bulges" where the pressure has released, and this is evident, along with a startling re-orientation of the airframe with the airstream, what you see as an emphatic 'wobble', producing large G deviations from "Normal".
This "Snap" roll left is not commanded, and it is definitely not reversed, by the pilot. It is far too quick to have been input by Leeward. I am magnifying the video to see if I can capture the Left aileron bulging in to the airstream at the TE, but so far...
Can this event have been instigated by the Trim Tab failure? Possibly. It would have also caused a Pitch UP, and an adverse and torsional roll also.
The Tail is seen rebounding from this torsion in a dramatic out of rig aspect with the wings, look closely, and see the airframe rock and roll with this out of rig condition. (It is quite brief, if it had continued, the a/c would likely have come apart at this point.) This misaligned and reorienting event may have produced what was heard as a pop. It is not impossible some substructures broke, or fractured. It may have been the TailWheel snapping away from its lock.
Last edited by Lyman; 1st Oct 2011 at 14:14.
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deSitter: Check closely - just before the sudden left roll, it seems to me the plane is trying to roll RIGHT, very slight, almost imperceptible - but definitely there. In particular, just before tucking the left wing under, it seemed the right rolls were about to get out of hand so he overcorrected with left roll INPUT, and then snap - too late.
In other words, he's in a fast steep turn with highly modified aerodynamics for his airplane, and it has basically stopped flying normally and is trying to roll right - probably because the outer (right) wing is stalled. It's in a high-speed stall induced by too much speed through a turn.
In other words, he's in a fast steep turn with highly modified aerodynamics for his airplane, and it has basically stopped flying normally and is trying to roll right - probably because the outer (right) wing is stalled. It's in a high-speed stall induced by too much speed through a turn.
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Wake Turbulence is certainly a possibility. The aircraft in entering its last turn exhibits an instability in roll that could be Wake Turbulence induced, but consider that for the instability to remain uncorrected points instead to the inherent instability of this a/c at speed. WT is a fleeting event, it flies its own path, and it does not conform to the flight path of the following a/c.
Was the Ghost In/Out of W/T? If the procuring cause of the upset, it is unlikely to have remained in the Ghosts path, and the upset/crash was a result of the initial snap Left, whether a broken tab, overcontrol, W/T, or STALL.
On the back straight, Ghost descends and levels, reaching its likely maximum speed in the circuit. The turn imparts high G force and the turn tightens as Leeward rolls to ~80 degrees.
Ghost is in passing mode, flat out, and the psyche is powerful. I think 177 is as tight to this pylon as any in the circuit, and loss of control at its most susceptible.
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.
So, maximum velocity, roll rate; minimum wing, aileron. Test Flight.
Was the Ghost In/Out of W/T? If the procuring cause of the upset, it is unlikely to have remained in the Ghosts path, and the upset/crash was a result of the initial snap Left, whether a broken tab, overcontrol, W/T, or STALL.
On the back straight, Ghost descends and levels, reaching its likely maximum speed in the circuit. The turn imparts high G force and the turn tightens as Leeward rolls to ~80 degrees.
Ghost is in passing mode, flat out, and the psyche is powerful. I think 177 is as tight to this pylon as any in the circuit, and loss of control at its most susceptible.
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.
So, maximum velocity, roll rate; minimum wing, aileron. Test Flight.
