Minnesota Crash

[Raymond J1]

This seems the horizontal tailplane, seen with the same angle as the wing. The plane does not look broken, just tilted to the right.

[DXB]

Ugh what a horrific tragedy - it doesn't seem like there's a count on casualties or identification of victims.  The 3 or 4 relevant frames of that Youtube vid show the plane pancaking in at a very nose high attitude with the airframe appearing fully intact.  There was a loss of control of unknown cause, and I don't care to speculate on that given the limited info available.  However, around the moment the bottom of the empennage strikes the ground, the central spar snaps and both wings fold up vertically.  The horizontal stab seems to do the same.  As a non-physicist/engineer, the structural forces that would make the main spar snap at that particular moment are not at all intuitive to me, but forces on the horizontal stab seem to have been similar. Regardless, wing spar failure does not appear to be the etiology of this accident. accident.  Any insights from the engineers here on why the airframe would come apart this particular way at the moment of impact? 

[jlunseth]

33 minutes ago, carusoam said:

Note on wing stress: below maneuvering speed, the wing will stall before it gets damaged… a design criteria of GA airplanes… approach to the airport appears to be pretty well below maneuvering speed

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

[DXB]

10 minutes ago, Bartman said:

First of all this is a tragedy and there may have been a medical or workload issue. My condolences to the family and friends. 
 

I am convinced the appearance of the wings is an artifact brought about by capture rate and the speed of decent. If you look closely at the tail there are two images superimposed. There are two stripes and one elongated tail. 

Video artifact?!   Interesting - I don't know squat about these cameras, but I see what you mean about the tail.

[jlunseth]

1 minute ago, DXB said:

Ugh what a horrific tragedy - it doesn't seem like there's a count on casualties or identification of victims.  The 3 or 4 relevant frames of that Youtube vid show the plane pancaking in at a very nose high attitude with the airframe appearing fully intact.  There was a loss of control of unknown cause, and I don't care to speculate on that given the limited info available.  However, around the moment the bottom of the empennage strikes the ground, the central spar snaps and both wings fold up vertically.  The horizontal stab seems to do the same.  As a non-physicist/engineer, the structural forces that would make the main spar snap at that particular moment are not at all intuitive to me, but forces on the horizontal stab seem to have been similar. Regardless, wing spar failure does not appear to be the etiology of this accident. accident.  Any insights from the engineers here on why the airframe would come apart this particular way at the moment of impact? 

Dev, look at the video and the freeze frames someone was kind enough to put up. The wing is already folded before the aircraft strikes the ground, they do not fold at the moment of impact. 

[Davidv]

13 minutes ago, Bartman said:

First of all this is a tragedy and there may have been a medical or workload issue. My condolences to the family and friends. 
 

I am convinced the appearance of the wings is an artifact brought about by capture rate and the speed of decent. If you look closely at the tail there are two images superimposed. There are two stripes and one elongated tail. 

Yes, at the speed it was falling to the ground, a right bank tight before impact could have caused the right wing to hit first and maybe that caused it to snap upwards….

[DXB]

9 minutes ago, jlunseth said:

Dev, look at the video and the freeze frames someone was kind enough to put up. The wing is already folded before the aircraft strikes the ground, they do not fold at the moment of impact. 

First frame where it comes into view, the airframe looks normal - clearly something serious happened but the spar is in one piece at that moment.  A single frame later the horizontal stab and both wings appear folded up, but it's not entirely clear to me if the tail is contacting the ground at that moment. I'm having trouble imagining the forces that would cause the central spar to snap at that moment, or how it could have that appearance as a video artifact.  I've no expertise in assessing either though. 

[jlunseth]

No, I am sorry, but the speculation that the impact caused the wings to fold is not accurate. Go into the video in youtube, hit settings and set the video to play at the lowest speed (0.25). At 17:40.04 hit the “k” key which stops the video. Then use your right and left arrow keys to step through the video. These controls do not work perfectly every time, but if you play with them you should be able to watch the aircraft fall at slow speed.  You may have to exit the video and enter again to get the controls working properly. Both the right and left wing are folded vertically before the tail of the aircraft strikes the ground. The leading edge of the right wing is plainly visible behind the left wing. It also appears that the flaps and ailerons may be gone but I am not going to speculate on that, the NTSB will figure it out. The time stamp on the video obscures the crucial point where the ailerons would be at the fixed wingtip, so it is difficult to see whether that point is protruding backwards with no aileron attached. The quality of the video is quite good on my screen.

[carusoam]

Note on wind shear…. Stalling prior to breaking is good for the wing… given enough altitude to recover from the stall.

Last altitude ping was 2900’ MSL…

Airport KFCL is at about 900’ MSL… 

 

Note on reality vs. electronic images… it is quite possible that AI tries to sew images together… what we see in a single frame, where the object is moving so quickly… may not actually be complete reality… unfortunately…

 

Thanks to JL for the extra insight of the local area, and how to slow the video down frame by frame…

Best regards,

-a-

[BKlott]

Prior event involving “minor” damage to the aircraft:

------- FAA Accident/Incident 1 -------
Occurrence Date	2014-06-06		Aircraft Make	MOONEY
Aircraft Model	M20M		Damage	MINOR
Document Last Modified	2014-07-31
Narrative	AIRCRAFT DEPARTED KMLE AT APPROXIMATELY 13:00 CDT WITH INTENDED DESTINATION OF KAXN. AIRCRAFT WAS ON A VFR FLIGHT. AT AN ALTITUDE OF APPROXIMATELY 5500' MSL, APPROXIMATELY 5 MILES FROM KMML, THE WINDSHIELD WAS SUDDENLY COVERED IN OIL ELIMINATING ALL FORWARD VISION. PILOT STATED THAT HE PULLED BACK THE THROTTLE AND BEGAN AN IMMEDIATE DESCENT TO KMML. THE PILOT LANDED THE AIRCRAFT ON RUNWAY 12 AND WENT OFF THE END OF THE RUNWAY, STOPPING IN THE GRASS. ON SCENE INVESTIGATION OF THE INCIDENT FOUND THAT THE PLUG AT THE FRONT OF THE ENGINE AND THE PROPELLER GOVERNOR IDLER GEAR SHAFT HAD DEPARTED THE ENGINE CRANKCASE AND WERE FOUND INSIDE THE PROPELLER RING GEAR ASSEMBLY.
***** No NTBS Accidents Found *****
***** No NTBS Pre 1982 Accidents Found *****
------- SDR 1 -------
Date Of Report	1994-03-31		Operator Control Number	94ZZZX1691
Date Of Occurrence	1994-02-28		Aircraft Registration	9156Z
Aircraft Manufacturer	MOONEY		Aircraft Group Code	M20
Aircraft Manufacturer Model	M20M		Aircraft Make Model Sequence	5870222
Air Carrier Name	Unknown		Air Carrier Operation Code
Operation Type	G		Stage Of Operation	APPROACH
Severity Factor	FREQUENT		Air Transport Association Code	Reciprocating Engine Cylinder Section
Precautionary Procedures	NONE		Nature Of Condition	ENGINE FLAMEOUT, VIBRATION/BUFFET
Segment	ENGINE		Descriptive Name Of Part	VALVE
Defective Location On Aircraft	NR 3 CYL EXH		Failed Part Condition	BROKEN
Part Total Time	444		Part Total Time Since Overhaul	0
Component Manufacturer			Component Manufacturer Model
Component Manufacturer Number			Manufacturer Part Number
Ata Code
Remarks	ENGINE BECAME ROUGH UPON REDUCTION OF POWER FOR LANDING. UPON INSPECTION OF ENGINE FOUND CYLINDER NR 3 EXHAUST VALVE WITH ONE-QUARTER OF FACE MISSING. ALSO FOUND CYLINDER NR 1 WITH PISTON PIN CAP SHAVING OFF MATERIAL. TOP OVERHAULED ENGINE WITH FACTORY NEW CYLINDERS (UNDER LYCOMING WARRANTY).

 

 

 

[A64Pilot]

I think it has do do with frame rate and speed of object, but I’m sure we have all seen bent props on a Gopro or similar camera before, I think the broken wings are from a similar effect.

But boy they do sure look real 

[aviatoreb]

I agree - I think it is entirely plausible that the wing folding appearance is a video artifact.

How many of us have take videos or photographs either through our spinning prop looking forward or of another airplane on the ground looking at the prop - and it seems like the prop is dramatically curved?  

I am just sick inside seeing what was clearly a horrible accident.

[DXB]

32 minutes ago, jlunseth said:

No, I am sorry, but the speculation that the impact caused the wings to fold is not accurate. Go into the video in youtube, hit settings and set the video to play at the lowest speed (0.25). At 17:40.04 hit the “k” key which stops the video. Then use your right and left arrow keys to step through the video. These controls do not work perfectly every time, but if you play with them you should be able to watch the aircraft fall at slow speed.  You may have to exit the video and enter again to get the controls working properly. Both the right and left wing are folded vertically before the tail of the aircraft strikes the ground. The leading edge of the right wing is plainly visible behind the left wing. It also appears that the flaps and ailerons may be gone but I am not going to speculate on that, the NTSB will figure it out. The time stamp on the video obscures the crucial point where the ailerons would be at the fixed wingtip, so it is difficult to see whether that point is protruding backwards with no aileron attached. The quality of the video is quite good on my screen.

As far as I can tell, these are the only 3 frames that provide any insight.  Am I missing one?  In the first one, the spar appears intact. In the second one it has clearly snapped (barring a video artifact which I am having trouble imagining).   In that one, is not clear whether the tail is contacting the ground or not, but part of it may be obscured by grass in the frame so it seems plausible (compare contour of the visible red paint under the tail to the same area in the frame above).  In the third frame, the fuselage has cratered /disintegrated but the folded wings are still clearly visible (also artifact?).  I'm really not sure what's going on here.

Edited August 8, 2021 by DXB

[Shadrach]

In my opinion, the image of the folded wings is not consistent with any artifact I have seen in other videos. For one, they do not appear distorted in any way. Additionally, both wings appear folded up almost symmetrically at the fuselage attach points. Seems unlikely an artifact of the right wing. This is a very sad and odd situation. The flight aware data does not show an overspeed condition nor the types of changes in pitch that one would normally associate with an in flight break up.

Edited August 8, 2021 by Shadrach

[toto]

When I look at the earliest image, it looks like the underside of the wings is painted in the maroon color. Then suddenly in the "folded" images, the underside is white. Am I looking at this wrong?

[toto]

2 minutes ago, toto said:

When I look at the earliest image, it looks like the underside of the wings is painted in the maroon color. Then suddenly in the "folded" images, the underside is white. Am I looking at this wrong?

Answering my own question.. yep, you're looking at it wrong..

[Raymond J1]

47 minutes ago, DXB said:

Première image où elle apparaît, la cellule a l'air normale - il s'est clairement passé quelque chose de grave mais le longeron est en un seul morceau à ce moment-là. Une seule image plus tard, le stab horizontal et les deux ailes semblent repliés, mais je ne sais pas tout à fait si la queue touche le sol à ce moment-là. J'ai du mal à imaginer les forces qui feraient claquer le longeron central à ce moment-là, ou comment il pourrait avoir cette apparence d'artefact vidéo. Je n'ai aucune expertise dans l'évaluation non plus. 

Deux images qui se suivent donnent des contradictions. A 0:03 l'avion est entier, à 0:04 il y a cette vue mais il a déjà touché le sol. Le bris de l'aile est semble t'il une conséquence de l'impact.

 

[DXB]

10 minutes ago, toto said:

When I look at the earliest image, it looks like the underside of the wings is painted in the maroon color. Then suddenly in the "folded" images, the underside is white. Am I looking at this wrong?

I wondered about that too but I suspect it is just a light/shadow effect plus poor resolution from the end-on viewing angle 

[DXB]

16 minutes ago, Raymond J said:

Deux images qui se suivent donnent des contradictions. A 0:03 l'avion est entier, à 0:04 il y a cette vue mais il a déjà touché le sol. Le bris de l'aile est semble t'il une conséquence de l'impact.

Merci pour votre contribution de l'autre côté de l'océan Atlantique. J'aurais aimé en savoir assez pour continuer le dialogue en français.

[lithium366]

What you see as a double-tail artifact is a car parked behind (compare several frames).

Wings painted white just blend into the color of the skies on a shitty video so looks like they were collapsed in all 3 frames 

[Flyfalcons]

That's no video artifact.

[aviatoreb]

There are several particularly vexing and mysterious things about this crash that are unsettling.  Not least of which the possibility of a wing fold structural failure vs a video artifact.  I expect the ntsb will not only need to do what they can to analyze the physical wreck if it is still in condition to decide the issue, but perhaps talk to the specific company that makes that specific camera to get to the bottom of what kind of video artifacts are possible with that kind of camera.

[ragedracer1977]

Zoomed in a bit.  That's both wings. No way a video artifact. Given the structure involved, I can't imagine how such a thing is even possible.  

 

[Flyfalcons]

You can clearly see the TKS leading edges on both wings.  

[DXB]

Could the tail striking with enormous force with the nose up transmit enough horizontal load to the main spar to break it?  It is designed to take enormous vertical loads but much weaker to horizontal stress I believe?