Minnesota Crash

[DXB]

2 hours ago, A64Pilot said:

I don’t believe the rates of descent are possible. You just can’t go from level flight at what assumption is less than gear speed as his gear were down to over 300 kts in 2,000 of altitude?

Remember the gear are down so their drag at those airspeeds are quite substantial. I doubt the aircraft could achieve those speeds from 10,000 ft.

I accept you guys analysis on reported speeds, just believe the data is flawed

‘I also don’t believe the horizontal failed due to flutter, but from a tremendous overload, remember to pull the nose up at high G, the Horizontal has to develop a large downward force, I believe the wing and tail failed at about the same time, neither from flutter, failure modes are different so the investigation will be able to tell.

I believe that because in other accidents where the tail has failed, the wing actually fails downward as after the tail failed there is a huge neg G load on the wings, but in this case it seems apparent that the wings failed from positive G.

Do we know for a fact his gear was down? It's not clear to me from the video stills or if he was at a position on the approach where it would be expected to be down as he started to have trouble.  The speeds still seem extraordinary even with the gear up.  

FWIW, here's the report for the J that snapped its center spar in 2006 in Texas - in that case clearly flew into a thunderstorm.  The wreckage was pancake with both horizontal stabs attached but bent up 45 degrees and wings still part of the main wreckage.  Whether the spar snapped from positive or negative overload isn't made clear in the report  but would be apparent from looking at the metal.  In the thunderstorm I'd imagine oscillating loads deforming it in both directions with it ultimately snapping in the weaker direction. Once broken the "shuttle cock"- like behavior of the fuselage with both wings folded up might be much the same.  https://planecrashmap.com/plane/la/N577RS/

Regardless, the myth that the Mooney spar is indestructible has been safely put to rest in my mind.  

Edited August 10, 2021 by DXB

[Nukemzzz]

My condolences to the friends and family of those that were lost in this accident. 
 

I also wanted to say that I hope the NTSB follows MooneySpace because this is a master class of intelligent folks coming together to understand something.  If they read this thread it will save them some time. 
 

I also wonder…does the NTSB check forums for clues of what was maybe done before an accident?  Things posted by the pilot ahead of the crash  

 

 

 

 

[jaylw314]

56 minutes ago, Nukemzzz said:

My condolences to the friends and family of those that were lost in this accident. 
 

I also wanted to say that I hope the NTSB follows MooneySpace because this is a master class of intelligent folks coming together to understand something.  If they read this thread it will save them some time. 
 

I also wonder…does the NTSB check forums for clues of what was maybe done before an accident?  Things posted by the pilot ahead of the crash  

Sometimes but not always.  There was an infamous case in the RV community where the NTSB looked extensively at social media and forum posts prior to a fatal RV-10 crash, but some interpreted this as "witch-hunting" since that is not typically done

[FloridaMan]

Curious if the tail was worked on. There have been counterfeit bolts that have ended up in aviation supply chain before. 

[carusoam]

Many of the long bodies got their tail huck bolts reviewed for proper hardware… just a few years ago..

There was a case that some bolts were not the right ones, installed at the factory…

So… a large number of LBs had their bolts reviewed… a handful had their bolts replaced…

Expect a log entry to cover the AD would exist…

A search for huck bolts around here will probably uncover the AD itself…

 

Those bolts hold the whole tail on… at the hinge…

PP thoughts only, not a mechanic…

Best regards,

-a-

[Shadrach]

2 hours ago, jaylw314 said:

Sometimes but not always.  There was an infamous case in the RV community where the NTSB looked extensively at social media and forum posts prior to a fatal RV-10 crash, but some interpreted this as "witch-hunting" since that is not typically done

Yes, but  in that case didn’t they attempt to use the pilot’s previous online comments to portray him as anti-authority?

[Shadrach]

2 hours ago, carusoam said:

Many of the long bodies got their tail huck bolts reviewed for proper hardware… just a few years ago..

There was a case that some bolts were not the right ones, installed at the factory…

So… a large number of LBs had their bolts reviewed… a handful had their bolts replaced…

Expect a log entry to cover the AD would exist…

A search for huck bolts around here will probably uncover the AD itself…

 

Those bolts hold the whole tail on… at the hinge…

PP thoughts only, not a mechanic…

Best regards,

-a-

Almost everyone had their pitch trim assemblies and huck bolts reviewed. I would bet that the majority of the aircraft listed in the final AD were short and mid-bodies. An M20TN triggered the action but a misassembled J model ensured that all the metal tail Mooney aircraft were included.

 

https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAD.nsf/0/21d59bd9725bdf3e862579c7004a06a4/$FILE/2012-05-09.pdf

[toto]

It's been a sobering thought today, after reading Scott's blog post on the local weather, how a severe loss-of-control event could occur when descending from clear air with light winds through a 600ft layer into more clear air and a 1200ft ceiling.

[Raymond J1]

3 hours ago, carusoam said:

Many of the long bodies got their tail huck bolts reviewed for proper hardware… just a few years ago..

There was a case that some bolts were not the right ones, installed at the factory…

So… a large number of LBs had their bolts reviewed… a handful had their bolts replaced…

Expect a log entry to cover the AD would exist…

A search for huck bolts around here will probably uncover the AD itself…

 

Those bolts hold the whole tail on… at the hinge…

PP thoughts only, not a mechanic…

Best regards,

-a-

Antoine,

Drifting on the subject of this thread...

I have seen on Mooney many bolts that are not at the right length... You could say that they are not suitable. But I also saw that these bolts were well mounted, with excess washers to be able to provide the tightening function, I mean no thread of screws subjected to shear stress. For mounting the tail unit, there are 3 bolts and a hinge. The top two bolts each have a spacer...It is the spacers that performs the function of anti-friction bearing for pivoting in compensation. The bolts each have 2 shear surfaces... It's oversized. The hinge too is oversized, more so than the bolts.

In the M20, the inconsistency is the rudders, which hold with the same diameter of bolts as the engine frame...

 

To return to the topic of this thread, I found very relevant the proposal of a spatial disorientation with the distraction of a reprogramming of the GPS after the clearance of the controller... If the pilot does not have much maneuverability training in VSV condition (Flight without visibility) it is quickly a serious problem on our machines.

 

[jaylw314]

1 hour ago, Shadrach said:

Yes, but  in that case didn’t they attempt to use the pilot’s previous online comments to portray him as anti-authority?

Yes, that was the gist of it.  It was pretty damning stuff but there was also some specific statements and questions he posted about the electrical system that were relevant to the accident itself

Edited August 11, 2021 by jaylw314

[dominikos]

23 hours ago, David Lloyd said:

I think the first picture is the whole story.  At 18:38:34 something happens and the plane goes from a stable approach at a reasonable speed  to a short series of increasing pitch, turns, altitude and speed excursions ending 72 seconds later when the airplane descends from the clouds and pulls the yoke hard enough to break the airplane. The next to the last ADSB hit

showed 147 knots ground speed, but factoring in the 30,000 FPM descent would result in an airspeed considerably above VNE.

So, what happened at 18:38:34?  I have had several attitude indicator failures over the years as well as about 10 vacuum pump failures.  Two of the AI failures acted the same as with a vacuum failure:  over two or three minutes, the AI would oscillate slowly up, down, right, left with increasing amounts and rates as the gyro wound down.  Except the last one.  A couple seconds from a normal indication to a 45 degree bank and 20 degree pitch, oscillating back and forth, increasing the amount and rate, before suddenly parking itself in a 90 degree, nose high indication.  Start to finish about 10 seconds.  Thank God I wasn't in cloud.  Could his AI have failed?  Down, up, left, right, up, down, left, up, down!  Did the autopilot initially follow?  A sudden failure in a bumpy cloud might be overwhelming.

All of us would like to think something beyond our control happened here.  The elevator broke off causing the plane to go out of control.  Or the wing broke in half due to some hidden damage.  Or a thunderstorm.  Microburst.  No, we will wait two years for the NTSB report and find a mundane answer.  

This is a very scary possibility that I have not seen discussed much. With vacuum failure, if AP was engaged, could it start a chain of event that resulted in unrecoverable plane attitude??? I don’t know the safety margin for this autopilot, but let’s say that AI swing violently, if AP tried to keep up, it would a) confuse the pilot, b) might be interpreted as turbulence or microburst, c) took sometime to diagnose and respond to… At that point, we have spatially disoriented pilot with failing primary instruments.

I hope this makes sense. Putting it forward as a scenario but also as a question on how to avoid situation like this with AP engaged. I don’t believe APs have automatic failover in case of AI failure.

[toto]

10 minutes ago, dominikos said:

This is a very scary possibility that I have not seen discussed much. With vacuum failure, if AP was engaged, could it start a chain of event that resulted in unrecoverable plane attitude??? I don’t know the safety margin for this autopilot, but let’s say that AI swing violently, if AP tried to keep up, it would a) confuse the pilot, b) might be interpreted as turbulence or microburst, c) took sometime to diagnose and respond to… At that point, we have spatially disoriented pilot with failing primary instruments.

I hope this makes sense. Putting it forward as a scenario but also as a question on how to avoid situation like this with AP engaged. I don’t believe APs have automatic failover in case of AI failure.

Pretty good recentish article in Aviation Safety on this..

https://www.aviationsafetymagazine.com/features/autopilots-and-their-errors/

[donkaye, MCFI]

5 minutes ago, dominikos said:

This is a very scary possibility that I have not seen discussed much. With vacuum failure, if AP was engaged, could it start a chain of event that resulted in unrecoverable plane attitude??? I don’t know the safety margin for this autopilot, but let’s say that AI swing violently, if AP tried to keep up, it would a) confuse the pilot, b) might be interpreted as turbulence or microburst, c) took sometime to diagnose and respond to… At that point, we have spatially disoriented pilot with failing primary instruments.

I hope this makes sense. Putting it forward as a scenario but also as a question on how to avoid situation like this with AP engaged. I don’t believe APs have automatic failover in case of AI failure.

Before upgrading my plane, I had my KI256 OH'd at least 3 times.  Indication of failure was "slow to erect" time.  Normally, when power was removed from  it, it took time to spin down.  Only once did I come out to the airplane and on power turn on found the AI upside down.  What I'm saying is, unless there is a catastrophic failure of the gyro, it doesn't fail immediately, so the KFC 150 is not likely to go bonkers immediately.

In this day and age and with the cost of backup attitude indicators being so inexpensive, it is not fair to both a pilot and passengers not to have an electric one installed in the aircraft.

[jlunseth]

If you look at the specifications in the listing on aircraft.com when the aircraft was sold, it had both backup alternators and a standby vac, so the pilot had resources if the vac failed. https://www.aircraft.com/aircraft/1207543/n9156z-1991-mooney-m20m-bravo The panel photos do not show a backup AI, but there was a Turn Coordinator. My own experience with failure of the vac is that the AI continues to work for awhile, but you really need to disconnect immediately if it is failing because the gyro falls slowly and gives false readings as it does, then when it starts to wobble you have a real problem if you are on AP still. If the 256 itself fails, the failure in my own experience is very slow, over more than one flight, and although the aircraft might not maintain the final approach course very well you would be able to penetrate a deck that thin. You might be off course, but you would get through it.

All that said, there might be a sudden failure mode of the 256 that I am not familiar with.

I agree with Don, there is no excuse now for not having a good, backup, electric AI. Among other things, if the primary AI is drifting off and showing, for example, a bank when the aircraft is not in a bank, that would be immediately apparent by looking at the backup. If the vac fails it is critical to either immediately switch to the backup vac if you have one, and if you don't, get the aircraft off AP, hand fly, and go to what instruments you have available and that are working.

[donkaye, MCFI]

Adding to my previous post, this accident was unlikely to have happened had the GFC 500 with its envelope protection and level button been installed.  With the more expensive long bodies where the price to value of the airplane is relatively small, I think it makes sense to consider an autopilot upgrade a priority.  For safety purposes is makes sense for all models in my opinion.  With the newer autopilots with envelope protection I think spatial disorientation accidents could become a thing of the past.

[Hank]

1 minute ago, jlunseth said:

I agree with Don, there is no excuse now for not having a good, backup, electric AI. Among other things, if the primary AI is drifting off and showing, for example, a bank when the aircraft is not in a bank, that would be immediately apparent by looking at the backup. If the vac fails it is critical to either immediately switch to the backup vac if you have one, and if you don't, get the aircraft off AP, hand fly, and go to what instruments you have available and that are working.

So if you have an AI and a Backup AI, and they show different things, how do you identify quickly which one has a problem and which one [you hope] is still reading correctly?

[steingar]

What I really don't get is the layer he was in was only 1000 feet thick.  How could he get those violent oscillations and not pop out the top into clear air?

[ArtVandelay]

So if you have an AI and a Backup AI, and they show different things, how do you identify quickly which one has a problem and which one [you hope] is still reading correctly?

Combination of turn coordinator, airspeed and altitude indicators breaks the tie.

[PT20J]

10 minutes ago, ArtVandelay said:

Combination of turn coordinator, airspeed and altitude indicators breaks the tie.

That's easy during a training exercise, but more difficult under stress. The GFC 500 LVL will save you if the instrumentation is good but you just got distracted and lost control, but it may not help if the instrumentation is bad. In my new, about to be installed G3X/G5 there are three kinds of failures: Gross failures (like an accelerometer with no output) that are immediately obvious by a red X on the display, Recoverable failures that cause temporary loss of attitude information while realigning, and miscompare errors where the G3X and G5 don't agree and the software cannot tell which is correct. For this reason, I'm including a non-Garmin (so as to have technology diversity) AV-20-S. With three attitude indicators displayed, it will always be immediately obvious which is the problem and if that's the one that is driving the autopilot, I can revert the autopilot to the correct one.

Skip

[ArtVandelay]

if that's the one that is driving the autopilot, I can revert the autopilot to the correct one.
Skip

How difficult is that to do? How many menus do you need to navigate through?

[PT20J]

6 minutes ago, ArtVandelay said:

How difficult is that to do? How many menus do you need to navigate through?

Quickest way is to pull the offending CB.  

[Shadrach]

On 8/10/2021 at 1:25 PM, jlunseth said:

Dev, I did some searching and found a couple of others. They are not easy to find because they have been so few in number and the Mooney has been around long before the internet, therefore records are not necessarily in a searchable database, and I may not have found all.

One was a one-line report of a spar failure in an M18C.

"A72 Mooney M-18C 31 Mar 64 1 D Roanoke Rapids, N.C. USA. Wing failure (spar). Ref: NTSB file 2-1036"

https://apps.dtic.mil/sti/pdfs/ADA137254.pdf

The other was a J. https://aviation-safety.net/wikibase/44066

There may have been another J in California, I could not find enough of a record to verify.

The Rocket and J were wing failures, but both were different from the current accident in that the failure of the horizontal stabilizer reportedly caused the wing to fail in the negative direction, that is, upward if the aircraft had been right side up at the time. In the Rocket incident the factory concluded that the failure of the stabilizer caused the aircraft to tumble up and over, hence the negative wing failure. As we know, structural integrity in the upward direction is about half that in the downward direction, or at least that is how the FAA rates normal category aircraft. 

The issue of concern to us as Mooney pilots is that there have been at least four incidents now, of failure of the horizontal stabilizer and elevator, which likely is a flutter issue, not a load issue. This video has been around forever and is worth watching for anyone who needs a lesson in the effects of flutter. Turn the sound off, the music is aggravating.

The lesson is that we cannot exceed Vne. Not that any of us have been going around doing that just for fun, but rather, if put in a potential accident scenario we must obviously protect Vne at whatever cost.

Also, I was the one who said 800 based on having looked at the weather off and on during the day, earlier than the accident. Scott Dennstaedt gave us a RAOB that put the ceiling at 1200 and there were a few others who provided more current weather. Not that an extra 400 feet would make that much difference to your point about the force required to fail the wing by pulling up.

From the sparse accident history it does appear that failure of the wing can be caused by the failure of the stabilizer. It appears to me it would be fair to say, though, that this is the first time that has occurred in the positive direction rather than the negative (excluding the Mite accident in 72 - different wing). 

Adagio For Strings makes the video all the more ominous..

[M20F-1968]

3 hours ago, ArtVandelay said:

Combination of turn coordinator, airspeed and altitude indicators breaks the tie.

Take out the turn co-ordinator (or as I did with an S-TEC autopilot, hide it behind the panel) and replace with an electric AI. 

I have the Garmin G600, a 3" vacuum AI (as I also have a vacuum step), and a Mid-Continent 2" AI.  Two that run on electric power and one that is vacuum.  

John Breda

[toto]

4 hours ago, Hank said:

So if you have an AI and a Backup AI, and they show different things, how do you identify quickly which one has a problem and which one [you hope] is still reading correctly?

I may be oversimplifying, but in this particular case, a quick cross-check with a visible horizon before descending into IMC would identify the misbehaving AI.

[toto]

4 hours ago, jlunseth said:

I agree with Don, there is no excuse now for not having a good, backup, electric AI.

Especially when they cost less than 0.8amu with a battery and require no installation. 

https://dynonavionics.com/pocket-panel.php