Minnesota Crash

[ragedracer1977]

52 minutes ago, Yetti said:

downloaded from youtube.  Here we are panned over.

https://youtu.be/StTXvdm9x_8

 

I changed that on YouTube to 1/4 speed.  I'm even more convinced the wings were folded. Both of them.  You can see them both tilt forward in the next frame. 

[Scott Dennstaedt, PhD]

On 8/8/2021 at 2:08 PM, bradp said:

 

 Scott were there CBs in the area at the time or the accident? 

Brad,

Not that I can see.  There was a pretty nasty MCS that was to the ESE of the area as you can see on the IR satellite, but the tops in the area at the time of the accident were pretty low so the likelihood of any deep, moist convection was near zero.

 

Tops in the area were around 3,000 ft MSL based on this RAOB shown below that was launched about 15 minutes prior to the accident and only about 5 miles away. That's about as good as you are going to get for weather info. 

KFCM 072353Z 09007KT 9SM OVC012 22/19 A2977 RMK AO2 SLP077 T02220194 
KFCM 072253Z 06007KT 10SM OVC013 23/19 A2976 RMK AO2 SLP075 T02280194
KFCM 072153Z 08010KT 9SM OVC011 22/20 A2977 RMK AO2 SLP078 T02220200
KFCM 072100Z 08009G17KT 10SM OVC011 22/19 A2978 RMK AO2 T02220194

There was a wind shift right at the tops which is very common with stratocumulus decks that are largely created because of low-level instability and moisture (ground was fairly moist).  The air tends to dry out where the inversion stops because the winds switch to a more southwesterly (dry) flow.

[DXB]

1 hour ago, Yetti said:

I don't normally comment on crash videos.   but I do video.   Slowed down.  There is some weird ghosting/artifacts.   https://youtu.be/ZGf7B9X7_dg

 

To my eye, this version seems to corroborate those who say the right wing hit first and that's what snapped the spar.  Then there are those who say it clearly shows the plane coming down all the way with wings folded - that still doesn't seem to be the case in the first image of the plane. Perhaps everyone is suffering from confirmation bias when looking at the video, though spar failure in flight seems less likely in absence of this somewhat confusing visual information.  The loss of tail components before impact seems most likely due to overstressed components from overspeed flutter and/or hard manipulation of the elevator during the final moments of this tragic chain of events.   Very sad to hear three lives were lost but glad for lack of casualties on the ground.

Edited August 9, 2021 by DXB

[Yetti]

20 minutes ago, ragedracer1977 said:

I changed that on YouTube to 1/4 speed.  I'm even more convinced the wings were folded. Both of them.  You can see them both tilt forward in the next frame. 

I am of the need better video.  Watch the limbs behind the plane.   When the plane first enters the screen, the limb is visible where the wing should be if folded up.  There is lots of artifacting that is happening so.   What I find more weird is usually when you get low and slow in a Mooney you will get  a left wing hits first spiral.   This is nose up. mostly level.

[Yetti]

2G and 4G cant remember which is upper or lower limit.

[A64Pilot]

3 hours ago, MikeOH said:

If you accept an assumption that there was a PRE-existing defect (bad repair or corrosion) in the main spar then the video evidence is plausibly consistent.  The spar then becomes the weak point vs. the horizontal stab.  Further, that type of defect in the center section would result in BOTH wings breaking at the same time.

The nose up attitude is again consistent with the incredible timing of capturing this right at the moment of failure.

Still waiting for what kind digital video artifact would apply only to the image of the wings but not the fuselage???

That’s why I asked if anyone could find evidence of major damage in the past, was she rebuilt after tornado damage or whatever? Being such a newish airplane makes corrosion less likely I think.

Air speed wise, there wasn’t the altitude available to build a bunch of airspeed and the gear was down, which also of course helps keep from building a lot of speed quickly. Plus if you watch the video there just wasn’t a whole lot of forward   speed, it seems to me to be coming down at a rather steep angle, nose up. So she had around 1,000 ft to build speed? with the gear down and then be nose high before the crash?

60 MPH is over 5,000 ft per min, and if I had to guess it wasn’t descending faster than that, hitting the ground is like hitting a concrete wall, and 60 MPH into a wall is incredibly destructive.

I have no idea what kind of video artifact or whatever could cause this, it’s way over my head, I sort of understand CCD camera’s, about as much as say most understand how a car works.

But we are all tossing around theories, which is fine as it isn’t disrespectful I don’t think, and I’m certain we will find out if the wings broke before impact or not from the investigation. My SWAG is the experts can determine descent rate by how many feet were travelled between frames by knowing frame rate, but that’s a guess too.

[Yetti]

Standard frame rate is 30 frames per second.  Sometimes stuff is 29.   I am seeing like 3-4 frames of falling through the screen.  ie very fast falling.

[A64Pilot]

2 hours ago, toto said:

Some new details on KR including a video interview with the NTSB rep.  Notably, he said that portions of the left elevator and left horizontal stabilizer were found two blocks away from the crash.

http://www.kathrynsreport.com/2021/08/mooney-m20m-257-tls-bravo-n9156z-fatal.html

Well, that pretty much makes it certain that it was an inflight break up then, I just hope it was quick and maybe G’s were high enough for them to be unconscious

Edited August 9, 2021 by A64Pilot

[EricJ]

6 minutes ago, Yetti said:

Standard frame rate is 30 frames per second.  Sometimes stuff is 29.   I am seeing like 3-4 frames of falling through the screen.  ie very fast falling.

Security cams are often very low frame rate, 10-15 fps, and 15 fps was pretty common for just about everything not too long ago.   Interleaving can complicate interpretations, and often a lot of it is already processed out by the time it gets to YT.

 

[kmyfm20s]

I think a lot of use are having a hard time believing our overbuilt Mooney wings can actually fail and taco up like that. Something really bad happened up there and hopefully there is enough clean wing spar left to do the analysis. Sad deal, RIP pilot and passengers! 

[donkaye]

The fire went out fast.  Both wing parts are available and I would think the part that went through the fuselage didn't have enough time to completely burn.  So the whole wing should be available to see where it failed.

Given the wing was stress tested to 9½ Gs before the "jig" broke, I found it shocking to see the wings fold, if that is what happened.

The main spar is an I-beam stressed for the vertical.  Had it folded back that would be one thing, but to fold in the vertical where its strength is, that is something unbelievable.

[DJE22]

1 hour ago, A64Pilot said:

That’s why I asked if anyone could find evidence of major damage in the past, was she rebuilt after tornado damage or whatever? Being such a newish airplane makes corrosion less likely I think.

Air speed wise, there wasn’t the altitude available to build a bunch of airspeed and the gear was down, which also of course helps keep from building a lot of speed quickly. Plus if you watch the video there just wasn’t a whole lot of forward   speed, it seems to me to be coming down at a rather steep angle, nose up. So she had around 1,000 ft to build speed? with the gear down and then be nose high before the crash?

60 MPH is over 5,000 ft per min, and if I had to guess it wasn’t descending faster than that, hitting the ground is like hitting a concrete wall, and 60 MPH into a wall is incredibly destructive.

I have no idea what kind of video artifact or whatever could cause this, it’s way over my head, I sort of understand CCD camera’s, about as much as say most understand how a car works.

But we are all tossing around theories, which is fine as it isn’t disrespectful I don’t think, and I’m certain we will find out if the wings broke before impact or not from the investigation. My SWAG is the experts can determine descent rate by how many feet were travelled between frames by knowing frame rate, but that’s a guess too.

Initial NTSB interview shared that descent rate near end of the flight exceeded 5000’ per minute. 

[Jerry 5TJ]

If the image is at 15 frames per second, and if the camera is raster-scanned then the start of the scan is about 66 milliseconds before the end of the scan.   That’s enough to seriously distort the details of an object crossing the field of view at perhaps 1/2 foot per millisecond.  
 

Technical video details aside, I’m more interested to hear how this M20R got into an un-stabilized descent in the first place.   

[DJE22]

4 hours ago, eman1200 said:

has anyone posted the link to the audio?  do we know yet if there was more than 1 person aboard?

The audio is on this link:

 

even more revealing is this:

http://www.kathrynsreport.com/2021/08/mooney-m20m-257-tls-bravo-n9156z-fatal.html
 

[DJE22]

4 minutes ago, Jerry 5TJ said:

If the image is at 15 frames per second, and if the camera is raster-scanned then the start of the scan is about 66 milliseconds before the end of the scan.   That’s enough to seriously distort the details of an object crossing the field of view at perhaps 1/2 foot per millisecond.  
 

Technical video details aside, I’m more interested to hear how this M20R got into an un-stabilized descent in the first place.   

“….how this M20R got into un-stabilized…”

NTSB: parts of horizontal stab and elevator were found 2 blocks away 

(final heading of aircraft was North: horiz stab and elevator parts were found approx 2 blocks directly south)

[DJE22]

7 hours ago, 1980Mooney said:

It could be as simple as a case of autopilot failure for a pilot who historically relies on the autopilot when flying IMC approaches. The skills to immediately hand fly the plane in the clag may be rusty resulting in disorientation.  

Or, a pilot who engages autopilot “after” he has lost control; and the autopilot over stresses tail section….?

[DJE22]

9 hours ago, 1980Mooney said:

Exactly!  Everyone is off chasing the red herring.

Parts of horizontal stabilizer and elevators were found 2 blocks to the south of resting place 

[carusoam]

Time frame for a rock dropped in a vaccuum…  free fall without air  resistance…

From 2k’ agl….

https://www.translatorscafe.com/unit-converter/en-US/calculator/free-fall/

 

11 seconds…

@ a vertical speed of 245mph  or 22kfpm

 

This part of the wild ride was not contained in the Flightaware data…

The plane is not a rock, in a vacuum…

 

This simple calculation indicates… that when a plane loses control… it can be at Vne pretty quickly…

Applied to this accident… Vna can be exceeded very easily…

 

traditional crash investigation would use the needle’s shadow imprinted on the ASI’s face to know what the airspeed was at the time of deceleration…

 

This machine would be traveling very quickly if the pilot was incapacitated…

 

Along with gear down, the flaps would be expected to have been deployed at this point… adding to the strength issues…

[DJE22]

12 hours ago, jlunseth said:

I completely agree Anthony. However, I remember reading somewhere that the up and down drafts in a tstorm can cause virtually instantaneous changes in the airspeed that the wing experiences. In other words, the aircraft may be traveling horizontally at Vne, but is struck by up or down drafts many times that speed, which means the wing is well over Vne. Especially so in the “sheer wall” between where the storm is sucking up warm moist air, and where it is dumping down cold air and rain. This is why we all stay away from red cells. We get violent microbursts and straight line winds here in the summer. Not all the time and not everywhere, but they certainly happen and can be violent. A64 is right on that one. Having been in that spot at that airport before, and this is sheer speculation, that is what would cause the pilot to be less than responsive on the radio. Way too much going on and you are just trying to keep the white side up, the greasy side down, your head off the headliner, and some space between you and the earth. 

Here is the panel. It was a standard 6 pack with 530 and 430W’s. The specs say it had a stormscope. https://www.aircraft.com/aircraft/1207543/n9156z-1991-mooney-m20m-bravo

“I completely agree Anthony. However, I remember reading somewhere that the up and down drafts in a tstorm can cause virtually instantaneous changes in the airspeed that the wing experiences. In other words, the aircraft may be traveling horizontally at Vne, but is struck by up or down drafts many times that speed, which means the wing is well over Vne. Especially so in the “sheer wall” between where the storm is sucking up warm moist air, and where it is dumping down cold air and rain.”
 

pilots unfamiliar with flying in unpredictable, turbulent air mass instinctively engage autopilot when they sense trouble. The is precisely the opposite action one should take.  
We flew thunderstorm research in the late 80’s / early 90’s. We ALWAYS hand flew the aircraft and allowed the up and downdraft to take us.  I suspect we all know it doesn’t take a significant storm + autopilot engaged at the wrong time,  to break things.  Very curious to learn how the horizontal stab and elevator failure occurred.

”there but for the grace of God”

[FloridaMan]

Seems pretty standard. In overspeed situations the tail flutters, the elevator sheds its counterweights and all bets are off. There was a rocket crash some years ago in California that exhibited the same behavior. If I ever experience flutter, my intention is to chop power, prop full forward and throw out the brakes as quickly as possible. 

[DanM20C]

2 hours ago, 1980Mooney said:

Parts found 2 blocks away don't explain why he started making an S turn 2 miles away and why he departed 2700 ft a mile away from the crash site.

I know the last two radar tags are probably not very accurate.  But simple math with the information there shows that the airplane would been around 265kts of airspeed. (121kt ground speed over 2 sec=410ft horizontally, 800ft vertically over 2 sec, = aircraft traveling 899ft in 2 sec.  450ft/sec = 265kts)  I'm guessing that last return is about the point they exited the overcast and it happens to be about 2 blocks south of the impact.  The natural instinct would be to pull when you see all that ground in front of you, I'm sure I would have done the same.  I'm betting the structural failure happened in that last 3 sec to a structurally sound air frame. 

It's all so sad.  My thought's and prayers are with the families. 

Dan

[Urs_Wildermuth]

I think we have to be careful not to simply dismiss the break of the wing spar as impossible because we wish it to be so. Yes, no spar so far has broken in flight but there is always a first time.

Here it looks like we are seeing a multiple structural failure, which obviously can have a tremendous effect on our fleet. But that does not mean we have to go into denial and think that our eyes or the video deceives us just because we can not imagine it. On the opposite. If there is a problem, it needs to be addressed.

[bradp]

7 hours ago, DJE22 said:

Initial NTSB interview shared that descent rate near end of the flight exceeded 5000’ per minute. 

Now combine that fact with the apparent 45-def nose up attitude.  I think this is going to be a pull up and over stress event. 

[DXB]

3 hours ago, Urs_Wildermuth said:

I think we have to be careful not to simply dismiss the break of the wing spar as impossible because we wish it to be so. Yes, no spar so far has broken in flight but there is always a first time.

Here it looks like we are seeing a multiple structural failure, which obviously can have a tremendous effect on our fleet. But that does not mean we have to go into denial and think that our eyes or the video deceives us just because we can not imagine it. On the opposite. If there is a problem, it needs to be addressed.

I remain puzzled by those convinced by the video that an in flight failure of the central spar precipitated loss of control, leading to this accident. It does not convincingly show the wings folding up until the plane contacts the ground at high speed.  Certainly one should wait for info  gained from examining the central spar remnant before precluding the spar failure hypothesis, but such analysis may prove unobtainable here.  If it is unobtainable, it would be a logical fallacy to still favor a hypothesis that something unprecedented happened for this airframe when there are so many features here that are consistent with a more conventional accident.  Spatial disorientation in IMC, perhaps precipitated an avionics failure,  subsequent loss of control, and secondary structural overstress of the tail is a recurring tragedy that has killed scores of people since the dawn of aviation. An element of pilot medical incapacitation would be a bit further down on the list.  But the extraordinary interpretation of Mooney spar failure in absence of extreme turbulence as the primary cause here demands a much higher burden of proof; I doubt the NTSB will find compelling evidence to support that conclusion but cannot discount it entirely based on what is known at the moment. 

[Davidv]

5 minutes ago, DXB said:

I remain puzzled by those convinced by the video that an in flight failure of the central spar precipitated loss of control, leading to this accident. It does not convincingly show the wings folding up until the plane contacts the ground at high speed.  Certainly one should wait for info  gained from examining the central spar remnant before precluding the spar failure hypothesis, but such analysis may prove unobtainable here.  If it is unobtainable, it would be a logical fallacy to still favor a hypothesis that something unprecedented happened for this airframe when there are so many features here that are consistent with a more conventional accident.  Spatial disorientation in IMC, perhaps precipitated an avionics failure,  subsequent loss of control, and secondary structural overstress of the tail is a recurring tragedy that has killed scores of people since the dawn of aviation. An element of pilot medical incapacitation would be a bit further down on the list.  But the extraordinary interpretation of Mooney spar failure in absence of extreme turbulence as the primary cause here demands a much higher burden of proof; I doubt the NTSB will find compelling evidence to support that conclusion but cannot discount it entirely based on what is known at the moment. 

Agreed, with the frame rate of that video camera and the speed of the plane there is no way to conclusively say what happened.  However, as @DanM20C pointed out above, if the plane was indicating 265 knots at any point and the pilot yanked back the controls, maybe that could have been enough for some serious structural damage?