Big Crash at Reno
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PS.GG was reported at 495 mph; that equates to M.645 at 5500ft at an assumed *T of 20*C; M.75 would be 579 mph in the same conditions.
Shock strength and location are dependent on Mach number and CL. You can see what Mach buffet looks like from the tufts and the wake rake/camera vibrating. Mach buffet is just a stall, but at substantially higher q's so the loads are higher.
Last edited by ClippedCub; 10th Oct 2011 at 04:13.
Life's too short for ironing
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More fundraising for the victims of the crash going on at the moment....
loadedtv - live streaming video powered by Livestream
The goal is $1,000,000 - nothing ventured, nothing gained
loadedtv - live streaming video powered by Livestream
The goal is $1,000,000 - nothing ventured, nothing gained
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Nauseating
You are taking an airplane designed to kill Germans with 1940 engines. Because it's a cool airplane, let's race it by chopping it to s--t and tearing off its radiator and on and on.. stupid and hateful.
The pilot and his crew blasted several people into atoms with their insane modifications of this airplane, and their old man steward who dyed his gray hair brown, because the idea of graceful aging was anathema to his narcissist being, is the main culprit.
This entire episode is hateful to aviation - the butchering of a great airplane, the narcissism of the pilot, the tragedy of the annihilated and their families. For what? A stupid race that means nothing. A way to convert money into noise.
-drl
The pilot and his crew blasted several people into atoms with their insane modifications of this airplane, and their old man steward who dyed his gray hair brown, because the idea of graceful aging was anathema to his narcissist being, is the main culprit.
This entire episode is hateful to aviation - the butchering of a great airplane, the narcissism of the pilot, the tragedy of the annihilated and their families. For what? A stupid race that means nothing. A way to convert money into noise.
-drl
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This entire episode is hateful to aviation - the butchering of a great airplane, the narcissism of the pilot, the tragedy of the annihilated and their families. For what? A stupid race that means nothing. A way to convert money into noise.
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Video Frame Grabs
I've grabbed a bunch of video frames from the best video I've seen of the GG initial roll left. These have been processed by increasing brightness and contrast, and cropping to show only the aircraft. They seem to show the port elevator deflected up. The elevators are not visible at the initiation of the problem but soon become visible as the g turns the aircraft. Compare the thickness of the stabilizer-elevator combination above and below the fuselage to see this.
The only way that there would be significant elevator split is if the elevator torque tube system failed.
The third and fourth pictures appear to be showing the port elevator deflected upward. The second picture is not clear enough, and the attitude in the first picture puts the elevator too close to the wing to be sure of anything. Subsequent pictures appear to show the elevators back in balance.
One would assume that if the torque tube simply failed at either the port or starboard side, that the port elevator would be deflected downward by a force twice what was needed from the tab, and the starboard elevator would move upward due to the loss of down torque from the other side. Instead we appear to see the opposite effect, so perhaps the likely shearing of the torque tube is indeed due to a failure of the tab system.
The Ghost should have had an elevator bobweight in the system to increase stick force per g. If so, the mass of the elevator actuation system would act to dampen torsional shock loads being sent from the port elevator, so the torque on the inboard side of the port elevator could be higher than the torque on the inboard side of the starboard elevator.
The pictures of the trim tab separating indicate that the entire tab was not lost, but that it instead detached at the inboard end and broke off at the center support. The separation at the inboard tab attachment may be due to flutter from some other initial failure (such as the linkage), or it may be the actual initiating event.
The only way that there would be significant elevator split is if the elevator torque tube system failed.
The third and fourth pictures appear to be showing the port elevator deflected upward. The second picture is not clear enough, and the attitude in the first picture puts the elevator too close to the wing to be sure of anything. Subsequent pictures appear to show the elevators back in balance.
One would assume that if the torque tube simply failed at either the port or starboard side, that the port elevator would be deflected downward by a force twice what was needed from the tab, and the starboard elevator would move upward due to the loss of down torque from the other side. Instead we appear to see the opposite effect, so perhaps the likely shearing of the torque tube is indeed due to a failure of the tab system.
The Ghost should have had an elevator bobweight in the system to increase stick force per g. If so, the mass of the elevator actuation system would act to dampen torsional shock loads being sent from the port elevator, so the torque on the inboard side of the port elevator could be higher than the torque on the inboard side of the starboard elevator.
The pictures of the trim tab separating indicate that the entire tab was not lost, but that it instead detached at the inboard end and broke off at the center support. The separation at the inboard tab attachment may be due to flutter from some other initial failure (such as the linkage), or it may be the actual initiating event.
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Just thumbing through one of, if not the best book, on aerodynamics written and found this. (Aerodynamics for Naval Aviators)
The pilot may purposely induce various motions to the aircraft by the action of the controls. In addition, certain undesirable motions may occur due to inadvertent action on the controls. The most important condition exists with the short period longitudinal motion of the airplane where pilot-control system response lag can produce an unstable oscillation. The coupling possible in the pilot—control system-aircraft combination is most certainly capable of producing damaging flight loads and loss of control of the aircraft.
When the normal human response lag and control system lag are coupled with the airplane motion, inadvertent control reactions by the pilot may furnish a negative damping to the oscillatory motion and dynamic instability exists. Since the short period motion is of relatively high frequency, the amplitude of the pitching oscillation can reach dangerous proportions in an unbelievably short time.
When the pilot induced oscillation is encountered, the most effective solution is an immediate release of the controls. Any attempt to forcibly damp the oscillation simply continues the excitation and amplifies the oscillation. Freeing the controls removes the unstable (but inadvertent) excitation and allows the airplane to recover by virtue of its inherent dynamic stability.
The pilot induced oscillation is most likely under certain conditions. Most obvious is the case of the pilot unfamiliar with the "feel" of the airplane and likely to over control or have excessive response lag. High speed flight at low altitude (high q) is most likely to provide low stick-force gradients and periods of oscillation which coincide with the pilot- control system response lag. Also, the high q flight condition provides the aerodynamic capability for failing flight loads during the oscillation.
If a pilot induced oscillation is encountered the pilot must rely on the inherent dynamic stability of the aircraft and immediately release the controls. If the unstable excitation is continued, dangerous oscillation amplitudes will develop in a very short time.
If I'm not mistaken the accident ticks all the boxes, but as I commented before, time will tell. No taking over from the NTSB for me.
PILOT INDUCED OSCILLATIONS
The pilot may purposely induce various motions to the aircraft by the action of the controls. In addition, certain undesirable motions may occur due to inadvertent action on the controls. The most important condition exists with the short period longitudinal motion of the airplane where pilot-control system response lag can produce an unstable oscillation. The coupling possible in the pilot—control system-aircraft combination is most certainly capable of producing damaging flight loads and loss of control of the aircraft.
When the normal human response lag and control system lag are coupled with the airplane motion, inadvertent control reactions by the pilot may furnish a negative damping to the oscillatory motion and dynamic instability exists. Since the short period motion is of relatively high frequency, the amplitude of the pitching oscillation can reach dangerous proportions in an unbelievably short time.
When the pilot induced oscillation is encountered, the most effective solution is an immediate release of the controls. Any attempt to forcibly damp the oscillation simply continues the excitation and amplifies the oscillation. Freeing the controls removes the unstable (but inadvertent) excitation and allows the airplane to recover by virtue of its inherent dynamic stability.
The pilot induced oscillation is most likely under certain conditions. Most obvious is the case of the pilot unfamiliar with the "feel" of the airplane and likely to over control or have excessive response lag. High speed flight at low altitude (high q) is most likely to provide low stick-force gradients and periods of oscillation which coincide with the pilot- control system response lag. Also, the high q flight condition provides the aerodynamic capability for failing flight loads during the oscillation.
If a pilot induced oscillation is encountered the pilot must rely on the inherent dynamic stability of the aircraft and immediately release the controls. If the unstable excitation is continued, dangerous oscillation amplitudes will develop in a very short time.
Moderator
A way to convert money into noise.
Oh yeah, and give rise to many interesting and informative discussions (both in success, and unfortunate failure), some of which are intruded by persons offering no value or interest whatsoever, just foul drivel!
I'm sure there is great sadness with many people about this. Words like "kill" and "hateful" do nothing to help anyone get past this sadness. Perhaps deSitter should only type into computers which are not operating at the time....
On the positive side, I'm learning lots about control and stability! Thanks everyone else......
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their old man steward who dyed his gray hair brown,...... is the main culprit
Everyone else can relax now....
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Machinbird. I notice two additional artifacts: One, the port stabiliser makes a different line with the TE of the wing than does the Stbd. This shows a torsion to the right, out of rig with the Long axis? Also, one can see quite clearly the outline of the main spar in the wing. It is outlined by the skin taking form around it in reaction to the immense g.
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the port stabiliser makes a different line with the TE of the wing than does the Stbd.
Take powerpoint and mark up the picture you think this is most obvious.
Be sure you are not looking along the trailing edge line of the elevators. You have to look at the leading edge of the stabilizer to show actual tail twist relative to the wing, probably by lining up the corners of the stabilizer LE tips.
If the port elevator deflected as much as I suspect it did, it may account for the left roll at the beginning.
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Hi Machinbird. It is most pronounced in the second frame. Line up the port stab with the dihedral of the (left) wing. Do the same with the stbd stab and note what I think is about 7-10 degrees off rig. Leftward. A straightedge makes it look sharper. The first frame shows it also with the Port Stab tip proud of the wing line; the stabd is blended in.
Rotate the frame 90 degrees, it is of course easier to see that way. The fourth frame would be about where I see a start of the recoil of the tail feathers back to stabd in slomo.
If one was patient, and could orient the PITCH angle with the video, and index it with the time between frames, a rough value of G could be had?
Do you notice the Spar shadow spanwise?
These are not inconsequential interruptions of airframe contour/rigging.
Imagine trying to fly or recover with the tail out of rig several degrees from the fuselage and wings.
Or don't, gives me the willies........
Rotate the frame 90 degrees, it is of course easier to see that way. The fourth frame would be about where I see a start of the recoil of the tail feathers back to stabd in slomo.
If one was patient, and could orient the PITCH angle with the video, and index it with the time between frames, a rough value of G could be had?
Do you notice the Spar shadow spanwise?
These are not inconsequential interruptions of airframe contour/rigging.
Imagine trying to fly or recover with the tail out of rig several degrees from the fuselage and wings.
Or don't, gives me the willies........
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Lyman, I think you are being fooled by asymmetric elevator deflection into perceiving the stabilizer is twisted.
On the first picture, you cannot make out any stabilizer landmarks, only elevator. On the second picture, the light gap between the stabilizer and wing is symmetric although extremely small. On the third and fourth frames, the light gap appears symmetric.
Keep in mind we are dealing with very few pixels, and if you blow the pictures up to gain accuracy, the surfaces become 'mushy' and ill-defined.
Furthermore the display appears to begin shading in the next frame over a short interval and you have the beginning of the next image ghosting next to the current ones. This ghost effect isn't all bad since the degree of displacement of the ghost is an indication of rate of position change.
On the first picture, you cannot make out any stabilizer landmarks, only elevator. On the second picture, the light gap between the stabilizer and wing is symmetric although extremely small. On the third and fourth frames, the light gap appears symmetric.
Keep in mind we are dealing with very few pixels, and if you blow the pictures up to gain accuracy, the surfaces become 'mushy' and ill-defined.
Furthermore the display appears to begin shading in the next frame over a short interval and you have the beginning of the next image ghosting next to the current ones. This ghost effect isn't all bad since the degree of displacement of the ghost is an indication of rate of position change.
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From this video;
Reno Crash Live 2011-09-16 - YouTube
If anybody can work out pitch rate for the first 45 degrees and the last 45 degrees of pitch, we can work out g. Might need a stop watch after correlating to the video clock. I got 90 degrees in 2 seconds but that's rounded from the video. Even then, works out to 16-20 g's average. Makes sense that Voodoo pulled 10g with one tab intact that GG would pull 20 g's with the only trimming tab displaced. If we can get tenths of a second, the number will be more accurate.
Torquing across the elevators due to the one tab is still bothersome, and a failure mode could be either elevator twisted loose from the torque tube exciting the 180 degrees out of phase plunging flutter of the horizontal that might be seen in the video. This would over strain the tab actuator rod causing the tab to flutter/fail allowing a higher g pitch up than Voodoo.
Reno Crash Live 2011-09-16 - YouTube
If anybody can work out pitch rate for the first 45 degrees and the last 45 degrees of pitch, we can work out g. Might need a stop watch after correlating to the video clock. I got 90 degrees in 2 seconds but that's rounded from the video. Even then, works out to 16-20 g's average. Makes sense that Voodoo pulled 10g with one tab intact that GG would pull 20 g's with the only trimming tab displaced. If we can get tenths of a second, the number will be more accurate.
Torquing across the elevators due to the one tab is still bothersome, and a failure mode could be either elevator twisted loose from the torque tube exciting the 180 degrees out of phase plunging flutter of the horizontal that might be seen in the video. This would over strain the tab actuator rod causing the tab to flutter/fail allowing a higher g pitch up than Voodoo.
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From a colleague in the US
Subject: Fwd: [GSWarbirds] Reno Incident
So here is the scoop I got over the weekend. Turns out one of the
mechanics at the airport was on the ground team for one of the unlimited
racers and had the spot in the pits right next to the lost plane. The
ground team had a real time data feed from the airplane.
Looks like the plane had a high speed flutter on the port elevator trim
tab. The pilot reported a vibration.
· The trim tab came off in flight which caused the entire tail group
to twist. There are trim tabs on both sides and the asymmetry caused a
huge over load. Also high power settings require a lot of nose down trim
to stay level, the loss of the trim tab could not be overcome by the
pilot. The twist in the tail group made the tendency to nose up even
greater and caused damage to the internal structure in the tail –
looking at the pictures you will see the tail wheel is down and the gear
doors are gone – stuff was coming apart in there.
· The twist and the loss of trim caused a near instantaneous 11G pull
up – this probably incapacitated the 73 year old pilot and may even
have broken the mounts on the pilot seat. Note you cannot see him in the
cockpit. The 11G pull also caused a brief loss of engine power from low
fuel pressure – the pump could not overcome 11G.
· After the 11G pull up the airplane unloaded in steep climb –
with the G off the engine regained power.
· Without the pilot to overcome it the airplane torque rolled causing
a split S into the ground.
· The data showed that the airplane was pulling 105 inches on
manifold pressure on impact. The "normal" race boost would be 60
to 70. So the airplane was going just under 500MPH when it hit so no
fire just total disintegration.
Subject: Fwd: [GSWarbirds] Reno Incident
So here is the scoop I got over the weekend. Turns out one of the
mechanics at the airport was on the ground team for one of the unlimited
racers and had the spot in the pits right next to the lost plane. The
ground team had a real time data feed from the airplane.
Looks like the plane had a high speed flutter on the port elevator trim
tab. The pilot reported a vibration.
· The trim tab came off in flight which caused the entire tail group
to twist. There are trim tabs on both sides and the asymmetry caused a
huge over load. Also high power settings require a lot of nose down trim
to stay level, the loss of the trim tab could not be overcome by the
pilot. The twist in the tail group made the tendency to nose up even
greater and caused damage to the internal structure in the tail –
looking at the pictures you will see the tail wheel is down and the gear
doors are gone – stuff was coming apart in there.
· The twist and the loss of trim caused a near instantaneous 11G pull
up – this probably incapacitated the 73 year old pilot and may even
have broken the mounts on the pilot seat. Note you cannot see him in the
cockpit. The 11G pull also caused a brief loss of engine power from low
fuel pressure – the pump could not overcome 11G.
· After the 11G pull up the airplane unloaded in steep climb –
with the G off the engine regained power.
· Without the pilot to overcome it the airplane torque rolled causing
a split S into the ground.
· The data showed that the airplane was pulling 105 inches on
manifold pressure on impact. The "normal" race boost would be 60
to 70. So the airplane was going just under 500MPH when it hit so no
fire just total disintegration.
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Internet article of Matt Jackson denying previous internet article.
What Didn’t Cause the Reno Air Race Crash | Jeff Wise
What Didn’t Cause the Reno Air Race Crash | Jeff Wise
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"So here is the scoop I got over the weekend. Turns out one of the
mechanics at the airport was on the ground team for one of the unlimited
racers and had the spot in the pits right next to the lost plane. The
ground team had a real time data feed from the airplane."
Scoop of what?
Sorry but my daughter brought her iPad home and I had to try it out somewhere. No disrespect intended.
I've been following this thread since the accident and have learned a lot. The dynamics of racing, both human and Physical, are something of which I was previously unaware.
CC you've shown me what I should have been studying 35 years ago.
mechanics at the airport was on the ground team for one of the unlimited
racers and had the spot in the pits right next to the lost plane. The
ground team had a real time data feed from the airplane."
Scoop of what?
Sorry but my daughter brought her iPad home and I had to try it out somewhere. No disrespect intended.
I've been following this thread since the accident and have learned a lot. The dynamics of racing, both human and Physical, are something of which I was previously unaware.
CC you've shown me what I should have been studying 35 years ago.
Last edited by thcrozier; 11th Oct 2011 at 03:05.
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Another frame showing bent port HS due to plunging flutter if the frame isn't an optical illusion. The counterweights out at the tips would exacerbate this mode from the elevator pitch flutter, and/or an elevator twisting off the torque tube. The left one looks a little bent too.
http://www.wire-edm.com/temp/1.jpg
http://www.wire-edm.com/temp/1.jpg
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Machinbird. You are saying that asymmetric elevator has me fooled into seeing the stabilizer is twisted? What else could it be doing? Any out of consonant deflection by the two elevators would torque the Stabs radically. At that velocity? It would twist the airframe, I don't see ailerons capable of rolling that a/c that rapidly, the roll was uncommanded, surely.
I do see the twist of the tail, and I see the a/c recovering from it in the video. The recoil shakes the image of the a/c in the video, do you not see that? There is distortion of the image throughout this sequence, the object was in the midst of a violent airborne prang. imo.
Cub: Yes, The left HS has a pronounced anhedral in that image.
That appears to be Mach's #2 image in his four sequence panel, above.
If I may, I'd suggest I see the ailerons commanding a right roll in that image, and we know it was rolling left. Did the tab problem interrupt a right roll?
I do see the twist of the tail, and I see the a/c recovering from it in the video. The recoil shakes the image of the a/c in the video, do you not see that? There is distortion of the image throughout this sequence, the object was in the midst of a violent airborne prang. imo.
Cub: Yes, The left HS has a pronounced anhedral in that image.
That appears to be Mach's #2 image in his four sequence panel, above.
If I may, I'd suggest I see the ailerons commanding a right roll in that image, and we know it was rolling left. Did the tab problem interrupt a right roll?
Last edited by Lyman; 11th Oct 2011 at 03:32.
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Ailerons Frame 2 to 3
Frame 2 appears to me to show the ailerons commanding a right roll as well, but because the plane had moved some distance between 2 and 3, the camera angle, including a possible roll off vertical of the focal plane itself, might have occurred within that interval. Spherical aberration in the lens might also be coming into play. Therefore, I wouldn't bet a whole lot of money that the plane is really banked more steeply left in Frame 3 than it is in frame 2. I'd want to know much more about the camera and lens before opining on what frame intervals show. You might even need multiple angles to be sure; though telemetry could well render optics issues moot at the end of the investigation.
I agree that there appears to be significantly more downward force on the left side HS than on the right in Frame 2; so his initial roll rate to the right could have been slower than he expected. Was he really going for horizontal wings, which, if still conscious at the time, he would have known would send him straight over the crowd, or is it possibly over control or an unpredicted snap to the right that put him there?
I agree that there appears to be significantly more downward force on the left side HS than on the right in Frame 2; so his initial roll rate to the right could have been slower than he expected. Was he really going for horizontal wings, which, if still conscious at the time, he would have known would send him straight over the crowd, or is it possibly over control or an unpredicted snap to the right that put him there?
Last edited by thcrozier; 11th Oct 2011 at 06:50. Reason: Typo
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I think the right elevator may have failed at its mount to the bellcrank before the tab failed. If it retreated upward, this leaves the left elevator to command the current NOSE DOWN. It cannot, on its own, so it loses the trim tab, and both elevators migrate to emphatic NOSE UP, though asymmetrically. I'd like to be able to say Jimmy immediately pushed and rolled right, but I think he was already incapacitated. I think with maximum tail section deflection down, and twisted port down, the a/c violently reacted, and pitched back on its own to ND and level, carrying right aileron throughout the double fail. The tail section reverted to close to original alignment, but, carrying some NOSE UP bias, the a/c climbed, lost power, and ballistic roll, inversion, and power recovery followed.
It's hard to say. I am astonished with the violence of the Pitch Up with wings vertical, and believe this is the point of maximum airframe load.
The fact remains that NTSB have it all. All of it. They will have the real deal in time enough. Without risk, and bold experiment, life would not be full.
I'll be at RENO next year; maybe I'll get to meet up with Clipped Cub.
It's hard to say. I am astonished with the violence of the Pitch Up with wings vertical, and believe this is the point of maximum airframe load.
The fact remains that NTSB have it all. All of it. They will have the real deal in time enough. Without risk, and bold experiment, life would not be full.
I'll be at RENO next year; maybe I'll get to meet up with Clipped Cub.