Fatality Crash KHOU looks like a Cirrus

ircphoenix said:
Well to be fair, the checkout in a Cirrus for most insurance companies/rental outfits is longer than most people fly in a year.




My understanding is that the SR20 is a tad on the underpowered side, but the SR22 is fine.
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That makes a lot of sense. I imagine they go through all the slow flight characteristics.
 
RoscoeT said:
Maybe you saw a different video. The one I saw involved a shadow appearing for all of about one second before impact. It was rotating as it appeared. It sounds like what you are saying is that the airplane was falling perfectly vertically with no rotation, until a second before impact, where a spin may have started. Again, I've never seen an airplane fall in a vertical flight path without either being in a vertical dive, or spinning. I'd be interested to hear how you could reproduce this. And I don't think you can tell much about yaw rate from a one second shadow on a video. And unless a spin is very flat (this wasn't), the roll component is much more obvious than yawing. Believe me, I've done and seen hundreds of intentional spins, and seen some accidental ones as well. I know that they look like and how they develop.
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I have watched several videos which seemed to include the same basic footage. Here is one of them: http://www.click2houston.com/news/investigation-into-deadly-plane-crash-near-hobby-airport-continues

What you can clearly see is that the plane's shadow is not yawing up to just a second or so before impact.
You certainly don't see that non-yawing shadow for long, perhaps a second or so, but if a plane is spinning the yaw rate doesn't stop, not even for a split second. If you have a sample video of a spinning plane taking a pause in its yaw rate mid-spin, please share it.

Also, I am not saying anywhere the plane was falling "perfectly vertical". In fact, I am quite sure it had at least some forward speed.
 
RotorDude said:
I have watched several videos which seemed to include the same basic footage. Here is one of them: http://www.click2houston.com/news/investigation-into-deadly-plane-crash-near-hobby-airport-continues

What you can clearly see is that the plane's shadow is not yawing up to just a second or so before impact.
You certainly don't see that non-yawing shadow for long, perhaps a second or so, but if a plane is spinning the yaw rate doesn't stop, not even for a split second. If you have a sample video of a spinning plane taking a pause in its yaw rate mid-spin, please share it.

Also, I am not saying anywhere the plane was falling "perfectly vertical". In fact, I am quite sure it had at least some forward speed.
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That security cam is the ONLY video floating around. I timed all of 0.95 seconds from the instant the shadow becomes visible to the moment of impact. And there is a slow mo version, and I still see yaw from the start, but it appears it may have accelerated at the end. I have done hundreds of spins in thirteen different aircraft types. They do not all rotate smoothly and consistently prior to the fully developed stage, which can take up to 3 turns in many types. Some airplanes will break quickly into the spin entry, then wallow around slow for a moment before resuming a quicker rotation. Pilot inputs also have an effect on this change in rotation rate. And yes, I've had a spin nearly stop for a moment after it broke, before resuming rotation. Incipient phase. Aircraft differ, so do W&B conditions. Impact showed little to no forward speed.
 
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RoscoeT said:
That security cam is the ONLY video floating around. I timed all of 0.95 seconds from the instant the shadow becomes visible to the moment of impact. And there is a slow mo version, and I still see yaw from the start, but it appears it may have accelerated at the end. I have done hundreds of spins in thirteen different aircraft types. They do not all rotate smoothly and consistently prior to the fully developed stage, which can take up to 3 turns in many types. Some airplanes will break quickly into the spin entry, then wallow around slow for a moment before resuming a quicker rotation. Pilot inputs also have an effect on this change in rotation rate. And yes, I've had a spin nearly stop for a moment after it broke, before resuming rotation. Incipient phase. Aircraft differ, so do W&B conditions. Impact showed little to no forward speed.
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I don't think we are that far apart. I think that based on the shadow's near zero yaw rate, there was essentially no spin before the aircraft suddenly yaws and rolls, just prior to impact. Since it's very likely that the aircraft was in a deep stall just before the sudden yaw and roll, it could have been in what is called "incipient spin" at that point, meaning it's not quite spinning, but about to start it.
My main point is that there was no real spin until a second or so before impact. I have seen quite a few stall-spin accident videos, and have done quite a few spins myself, including during my aerobatic training long ago. I have also experienced some inadvertent/unintentional stall/spins in a glider, fairly recently. So I think I know enough to recognize a spin when I see it, and conversely a non-spin when it's not there.
The key point I see in this specific accident sequence is that apparently the spin portion, if any, was at the very last second and it was just a stall before that.
But as I said before, I am sure the NTSB experts will issue a final verdict soon enough.
 
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If the data cards from the avionics are intact, that will be by far the best data available and will answer the questions about what the plane was doing prior to impact. The video is interesting additional information but some of the analyses being carried out here are a bit of a stretch.
 
bikert said:
If the data cards from the avionics are intact, that will be by far the best data available and will answer the questions about what the plane was doing prior to impact. The video is interesting additional information but some of the analyses being carried out here are a bit of a stretch.
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RotorDude said:
The only thing I am "adamant" about is that the shadow in the video was not yawing until seconds before impact, and I have never seen a spin which doesn't include at least a moderate yaw rate. I am not disputing the possibility that a spin did develop at the very end, just before impact. My only point is that there was no spin before that point.
But I suspect the NTSB will have all of this fully analyzed in their report, and I will certainly defer to their verdict.
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I don't need to wait for the NTSB report to conclude you don't have a clue. You can't determine the rate of rotation or lack thereof based on so very few frames of a shadow. You can, however, conclude, based on the distribution of the wreckage, that the aircraft was basically falling straight down and by the frame just before impact, that it was closer to level than pointed straight down. My speculation, based on 35 years of flying, military and civilian, is that in an attempt to "keep the pattern tight" she overshot final due to the tailwind on base and cranked it around. In so doing she used too much rudder and skidded the aircraft. When it went into an accelerated stall with the yaw from the skid, the aircraft entered a spin too low to use the parachute or recover aerodynamically. Most of the Cirrus operators at my airfield tend to fly wider and longer patterns than lower performance singles. I bet she was used to a long stabilized final and when she attempted a "tight pattern," her motor skills were not up to the task.
 
Witmo said:
I don't need to wait for the NTSB report to conclude you don't have a clue. You can't determine the rate of rotation or lack thereof based on so very few frames of a shadow. You can, however, conclude, based on the distribution of the wreckage, that the aircraft was basically falling straight down and by the frame just before impact, that it was closer to level than pointed straight down. My speculation, based on 35 years of flying, military and civilian, is that in an attempt to "keep the pattern tight" she overshot final due to the tailwind on base and cranked it around. In so doing she used too much rudder and skidded the aircraft. When it went into an accelerated stall with the yaw from the skid, the aircraft entered a spin too low to use the parachute or recover aerodynamically. Most of the Cirrus operators at my airfield tend to fly wider and longer patterns than lower performance singles. I bet she was used to a long stabilized final and when she attempted a "tight pattern," her motor skills were not up to the task.
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I've been flying longer than you if that's a criterion, but my observation of no yaw rate (i.e. no spin) in this case until a moment or so before impact would be the same regardless. To determine yaw rate, all you need are two frames: if they are both showing the same yaw angle, the yaw rate is zero, i.e. no spin. So it's not really rocket science. As far as the rest of your theory, I suspect you might be right, esp. the final part, but still prefer to wait for the NTSB's verdict. I've already paid them, so might as well get my money's worth. :)
 
RotorDude said:
ITo determine yaw rate, all you need are two frames: if they are both showing the same yaw angle, the yaw rate is zero, i.e. no spin. So it's not really rocket science. :)
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I've watched the same video. You can't say there is ZERO yaw rate. The yaw rate is perhaps low but not zero.
 
bikert said:
I've watched the same video. You can't say there is ZERO yaw rate. The yaw rate is perhaps low but not zero.
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Yes, initially it's either zero or very low, so low that it precludes a spin. Then suddenly, just prior to impact, you see a significant roll and yaw rate, which could be the beginning of a spin at that point.
 
Is there a video that you can link to that shows that of which you speak?

I only see the security camera footage that lasts a second or so and the shadow shows yaw. I think the shadow may not show much of a yaw when the shadow first appears, but I think that is because of the distance of the shadow from where it ultimately ends up. As the video progresses there does appear to be quite a bit of yaw in there.
 
The first time I can clearly see the shadow is when it clears that propane tank. The plane is clearly rotating counterclockwise from this point until it hits the car. You can step through the vid frame by frame here:

http://rowvid.com/?v=9CE7gHkpsgE
 
I think there's some confusion... what many people are seeing as mostly roll, I believe, is yaw. I think the rapid aspect change on the shadow as the aircraft approaches the ground is throwing people.
 
ircphoenix said:
Is there a video that you can link to that shows that of which you speak?

I only see the security camera footage that lasts a second or so and the shadow shows yaw. I think the shadow may not show much of a yaw when the shadow first appears, but I think that is because of the distance of the shadow from where it ultimately ends up. As the video progresses there does appear to be quite a bit of yaw in there.
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If you play this video frame by frame, starting from when the shadow first appears, you'll see that initially the yaw rate is near zero, and then grows rapidly just before impact.
 
RotorDude said:
If you play this video frame by frame, starting from when the shadow first appears, you'll see that initially the yaw rate is near zero, and then grows rapidly just before impact.
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That's the one I've watched probably 2 dozen times now... and each time I see yaw in it from the moment the shadow is immediately apparent just after the propane tank until impact. I think there's a trick of shadow going on.
 
ircphoenix said:
That's the one I've watched probably 2 dozen times now... and each time I see yaw in it from the moment the shadow is immediately apparent just after the propane tank until impact. I think there's a trick of shadow going on.
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I think there are definitely some perception issues occurring.


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Witmo said:
I don't need to wait for the NTSB report to conclude you don't have a clue. You can't determine the rate of rotation or lack thereof based on so very few frames of a shadow. You can, however, conclude, based on the distribution of the wreckage, that the aircraft was basically falling straight down and by the frame just before impact, that it was closer to level than pointed straight down. My speculation, based on 35 years of flying, military and civilian, is that in an attempt to "keep the pattern tight" she overshot final due to the tailwind on base and cranked it around. In so doing she used too much rudder and skidded the aircraft. When it went into an accelerated stall with the yaw from the skid, the aircraft entered a spin too low to use the parachute or recover aerodynamically. Most of the Cirrus operators at my airfield tend to fly wider and longer patterns than lower performance singles. I bet she was used to a long stabilized final and when she attempted a "tight pattern," her motor skills were not up to the task.
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Just to clarify, she was on upwind on her third go around. The controller was giving her instructions for her next approach. The first instruction was "turn left" he went on to instruct " join down wind for 4 and I need you to keep it tight................" It was during these instructions the controller said," ma'am, straighten up, straighten up". The end of the flight aware track shows a slight left turn before it ends. She was just left of RWY centerline off the departure end when she crashed. It wasn't a downwind/base or base/final turn.
 
ircphoenix said:
That's the one I've watched probably 2 dozen times now... and each time I see yaw in it from the moment the shadow is immediately apparent just after the propane tank until impact. I think there's a trick of shadow going on.
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uncreative said:
I think there are definitely some perception issues occurring.
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I agree that it's not trivial to analyze that shadow's behavior. I'd love to see what the NTSB do with it. I would not be surprised that an expert could extract the actual attitude of the aircraft from the shadow in each frame and reconstruct the dynamic evolution of the pitch, roll and yaw from it. Once that's available, the only missing element would be pilot control and power inputs, which perhaps can be deduced from the above. Then the results as far as what exactly happened would be clear.
I hope the NTSB wouldn't just brush it aside as yet another base-to-final stall-spin accident (though it might well have been), but analyze that crash sequence in frame-by-frame detail.
 
RotorDude said:
I hope the NTSB wouldn't just brush it aside as yet another base-to-final stall-spin accident (though it might well have been).
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That would be really stupid of them... it was not even close to a base-to-final accident. Maybe a crosswind-to-downwind accident, or an upwind-to-crosswind accident... she was on the opposite end of the runway from final.
 
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Lowflynjack said:
That would be really stupid of them... it was not even close to a base-to-final accident. Maybe a crosswind-to-downwind accident, or a upwind-to-crosswind accident... she was on the opposite end of the runway from final.
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I haven't looked at the details, but if she was that far from base, why would her airspeed have been that low? Not sure about the Cirrus, but most light GA aircraft would have a significant
margin over stall speed when on crosswind or downwind (up to abeam the numbers) assuming reasonably flown.
 
Incipient spins are usually not stable in rotation or attitude. That the shadow appears to indicate a changing rotation rate means little (to me), especially since we don't know what control inputs the pilot may have been using during the incident. That the aircraft fell nearly vertically, with only a moderate nose down attitude and exhibiting some rotation during the fall seem to be far better clues as to what happened, aerodynamically speaking.
 
RotorDude said:
I haven't looked at the details, but if she was that far from base, why would her airspeed have been that low? Not sure about the Cirrus, but most light GA aircraft would have a significant margin over stall speed when on crosswind or downwind (up to abeam the numbers) assuming reasonably flown.
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All you have to do is look at this thread. She missed on 35, she crashed NW of the field when being told to turn back to a downwind for 4.
 
JCranford said:
Holy crap! You claim to have looked at every detail of the 1.3 second shadow enough to deduce a cause but you dont know what end of the runway she was on!!??
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Actually I never deduced a "cause", and don't know the exact details surrounding the accident. My only focus was on the crash sequence as depicted in the short security video clip, where it appears to me that the plane enters the scene (as a shadow first) with a very low (or zero) yaw rate, and only goes into a possible spin at the very end, just prior to impact. What happened before the plane enters the video is unclear to me at the moment, though I assume the pilot got into a stall at some point and lost control.
 
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UngaWunga said:
screen cap right before impact.

i-PBVqW5j.jpg
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Yes, we are looking at the same video. Obviously by this point there is a pronounced yaw rate, and a very possible spin (though not sure it's "flat").
 
RotorDude said:
I haven't looked at the details, but if she was that far from base, why would her airspeed have been that low? Not sure about the Cirrus, but most light GA aircraft would have a significant
margin over stall speed when on crosswind or downwind (up to abeam the numbers) assuming reasonably flown.
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Correct but the kicker there is "reasonably flown".

3 occupants, who knows how much fuel but if she really cranked it hard and added some top rudder, there's a jump in load factor and a possible skid. The rest is self explanatory.
 
RotorDude said:
Yes, we are looking at the same video. Obviously by this point there is a pronounced yaw rate, and a very possible spin (though not sure it's "flat").
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I'm pretty sure planes don't typically spin "flat" like Goose and Mav in top gun. All the ones I've seen are nose down cork screwing in similar to this unfortunate incident. It takes a tremendous amount of elevator input with heavy throttle and a very far back CG to hold an actual flat spin in an aerobatic plane.
 
She stalled the airplane at very low altitude , possibly due to fuel exhaustion. As a result four people died needlessly.
 
RotorDude said:
I haven't looked at the details, but if she was that far from base, why would her airspeed have been that low? Not sure about the Cirrus, but most light GA aircraft would have a significant margin over stall speed when on crosswind or downwind (up to abeam the numbers) assuming reasonably flown.
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As with any plane you have to keep an eye on your speed while climbing out and turning cross. They don't teach us power on stalls for the fun of it, it's a real thing in all planes.
I fly an SR20 very similar to this plane and there are definitely things that can get you slow if you're not paying attention. Forget to pull flaps up, leave too much up elevator trim in from landing attempt, simply not watching airspeed and then initiating a tight turn.
There's also the potential of wake turbulence which would be a wild card that could case a problem like this even if she did do everything right on the climb out.

Fortunately the Cirrus has very robust data recording and will likely be reconstructed by the NTSB to give us a much better picture of what really went on.
 
tuwood said:
I'm pretty sure planes don't typically spin "flat" like Goose and Mav in top gun. All the ones I've seen are nose down cork screwing in similar to this unfortunate incident. It takes a tremendous amount of elevator input with heavy throttle and a very far back CG to hold an actual flat spin in an aerobatic plane.
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You don't have to hold an aerobatic airplane in a flat spin, you have to know how to get out of one. Art Scholl died filming the flat spins you mentioned while filming Top Gun. I don't think he was holding tremendous elevator. They think his CG may have been aft due to cameras mounted on the plane.

In a true flat spin, you have very little air over the horizontal and elevators, therefore it's hard to get the nose down. Some claim to have recovered by unbuckling and moving forward in the plane. The only way to get most GA planes into a real flat spin would be to have the CG loaded too far aft.
 
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Houston_accident_site.jpg By the way - here's the location of the accident site. ("Untitled Placemark")

Just to the N/W of the airport. From street view you can see the propane tank that was between the point of impact and the road in front of the hardware store. If you look at the upper left corner of the building, from the street, you can see the security camera that caught the images.
 
Lowflynjack said:
You don't have to hold an aerobatic airplane in a flat spin, you have to know how to get out of one. Art Scholl died filming the flat spins you mentioned while filming Top Gun. I don't think he was holding tremendous elevator.

In a true flat spin, you have very little air over the horizontal and elevators, therefore it's hard to get the nose down. Some claim to have recovered by unbuckling and moving forward in the plane. The only way to get most GA planes into a real flat spin would be to have the CG loaded too far aft.
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However it is extremely difficult for a GA plane to get into that true flat spin, not impossible but difficult. With aerobatic planes it requires a significant amount of power and large control surface inputs. Art Scholl was flying an aerobatic plane and if I recall the speculation was that he had a mechanical failure because he had done hundreds of flat spins without incident before.
Most GA planes tend to spin in a nose down fashion similar to the Cirrus in this case and the recovery is neutral aileron, down elevator, and opposite spin rudder. Basically you have to break the stall to recover.

I don't want to oversell my knowledge because I am still a student pilot myself in GA, but my experience with aerobatics is from building and flying 50% scale aerobatic RC planes for many years. It takes a lot of work to get a plane balanced out for a true flat spin and it takes a lot of power and control inputs to hold it. Full scale or 50% scale, the physics are still the same.
 
tuwood said:
However it is extremely difficult for a GA plane to get into that true flat spin, not impossible but difficult. With aerobatic planes it requires a significant amount of power and large control surface inputs. Art Scholl was flying an aerobatic plane and if I recall the speculation was that he had a mechanical failure because he had done hundreds of flat spins without incident before.
Most GA planes tend to spin in a nose down fashion similar to the Cirrus in this case and the recovery is neutral aileron, down elevator, and opposite spin rudder. Basically you have to break the stall to recover.

I don't want to oversell my knowledge because I am still a student pilot myself in GA, but my experience with aerobatics is from building and flying 50% scale aerobatic RC planes for many years. It takes a lot of work to get a plane balanced out for a true flat spin and it takes a lot of power and control inputs to hold it. Full scale or 50% scale, the physics are still the same.
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The way I was told when training with a very experienced aerobatic pilot in a Pitts is, if you intentionally get in one, you can get out. If you end up in one by mistake, you probably won't.

I agree, most GA planes won't go into one. If the CG was aft and your reaction when falling is to hold the stick back to keep yourself away from the ground... hang on.
 
Lowflynjack said:
The way I was told when training with a very experienced aerobatic pilot in a Pitts is, if you intentionally get in one, you can get out. If you end up in one by mistake, you probably won't.

I agree, most GA planes won't go into one. If the CG was aft and your reaction when falling is to hold the stick back to keep yourself away from the ground... hang on.
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I can agree with that. Goal number one is to never get into one in any plane by mistake. Your odds are a little better if you're in an aerobatic plane for sure.
 
tuwood said:
However it is extremely difficult for a GA plane to get into that true flat spin, not impossible but difficult. With aerobatic planes it requires a significant amount of power and large control surface inputs. Art Scholl was flying an aerobatic plane and if I recall the speculation was that he had a mechanical failure because he had done hundreds of flat spins without incident before.
Most GA planes tend to spin in a nose down fashion similar to the Cirrus in this case and the recovery is neutral aileron, down elevator, and opposite spin rudder. Basically you have to break the stall to recover.

I don't want to oversell my knowledge because I am still a student pilot myself in GA, but my experience with aerobatics is from building and flying 50% scale aerobatic RC planes for many years. It takes a lot of work to get a plane balanced out for a true flat spin and it takes a lot of power and control inputs to hold it. Full scale or 50% scale, the physics are still the same.
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I normally put some lead in the tail to get the CG back to where I liked it, which would produce some nice inverted flat spins:)
 
What about the W/B tendencies of a Cirrus? Considering two front seat pax, one rear seat pax, some luggage and an hour or two of fuel, would that tend to push the CG pretty far back?

I know a lot of the planes I fly have to really be forced to get the CG too far back.
 
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