China Eastern 737-800 MU5735 accident March 2022

[Link Kilo]

Various reports on social media of an incident involving China Eastern Airlines Boeing 737-800 operating flight MU5735. Some reports - unconfirmed by news sources as I type - state that the flight has supposedly crashed near Wuzhou.

[logansi]

Has crashed into the mountains

https://twitter.com/TheLegateIN/status/1505820283734994947

[logansi]

Final FlightRadar position has a decent rate of 31,000 fpm

[Auxtank]

METAR Wuzhou Xijiang Airport (WUZ)METAR ZGGG 210830Z 15003MPS 9000 SCT026 OVC050 28/23 Q1009 NOSIG

[TBSC]

From FL290 to ground in 2 mins. The aircraft was delivered to the operator new in 2015.

[Auxtank]

Manufacturer Serial Number (MSN) 41474
Line Number 5453
Aircraft Type; Boeing 737-89P(WL)

First Flight 5 Jun 2015
Age 6.8 Years
Production Site Renton (RNT)


https://cimg3.ibsrv.net/gimg/pprune.org-vbulletin/700x474/b_1791_china_eastern_airlines_boeing_737_89pwl_planespotters net_1254914_e0198c85b7_o_c4919eaff8b097730de13a8af02dfca9e0d 3653c.jpg

[A320 Glider]

FR24 shows FL290 to A090 in a 3 minutes. Is FR24 data reliable in this aspect?

A few things point to losing 20k in 3 minutes.

Unfortunately it isn't looking like a great outcome for all those onboard.
For Boeing, it isn't a MAX.

[logansi]

Apparent video of Final moments:

https://twitter.com/aus_forum/status/1505837550350782466

Nose straight down. Just awful

[A320 Glider]

Apparent video of Final moments:

https://twitter.com/aus_forum/status/1505837550350782466

Nose straight down. Just awful

I am a bit skeptical about that video.
However, if this is verified as true, then this is clearly suicide. Either pilot or cockpit breached.

[Ohrly]

I am a bit skeptical about that video.
However, if this is verified as true, then this is clearly suicide. Either pilot or cockpit breached.

It is the grainiest footage in the world, but it doesn't appear to have a vertical stabiliser to me.

[A320 Glider]

I can confirm its being shared by Chinese state media on Weibo. (Chinese facebook)

That looks too slow to be an aircraft in a nose dive, unless the CCTV playback was slowed down.

[switch_on_lofty]

Personally I look because I fly the same type and want to know what happened and if there's anything I can learn to avoid the same happening to me.
Purely from my selfish pov I'd rather see some evidence of what happened than nothing or silence. This allows me to draw inferences or conclusions. If there was a news blackout every time there was an accident or incident it wouldn't advance flight safety.
RIP to those onboard.

[TheEdge]

I am a bit skeptical about that video.
However, if this is verified as true, then this is clearly suicide. Either pilot or cockpit breached.
Looks like no wings or something similar....quite difficult to glide, maybe not a suicidal act.

[logansi]

If the Flightradar data is close to correct the final resting place is very close to Wuzhou (ZGWZ) - less than 5km. Wuzhou sees regular 737 flights.

[AmuDarya]

It might be helpful for the discussion here (as amateur speculations are not deleted) for professionals here to 1) state their credentials and 2) list causative factors that can be ruled out, given the extremely minimal information available.

That might help the readers here with a baseline against which these drive-by amateur comments can be measured.

[Running Ridges]

There’s a video going around showing what looks like part of the lower wing skin fairly intact. Would be surprised if a section that size survived a high speed impact. Maybe indicates partial break up pre-impact?

https://mobile.twitter.com/Shadi_Alkasim/status/1505821880791408640

[eagle21]

Is this part of the rudder (a/c right)? When comparing the paint scheme it seems like it is the only place that it could come from. Is so it has been found away from the fire
https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/864x1920/3a9746aa_f0c1_42f0_bdd4_edb11def99b7_8447f820376f5456e968368 cb828bc1f4cef162f.jpeg

[Homesick-Angel]

Surely nothing can be ruled in or out at this point?.

The Boxes (if intact) should tell a fair portion of the tale.

The speculation (for those who seem to be offended by it) is to do with a general interest , a fear that something similar should befall any of us and the hope the root cause , if it can be found, might stop it happening again.. it happens on every single similar thread here - if it does bother you it mightn’t be the site for you.

RIP to all.

[Flocks]

So when was the last time an autopilot disconnect caused a crash in China? You seem to insinuating it's happened regularly enough to not be an unexpected cause...
​​​​​
If it is not in China it doesn't count ? ...

Flash airline flight 604, malfunction lead to autopilot disconnected and pilot not controling their aircraft, that it is low altitude doesn't change anything, high altitude make it even more easier to loose control.

Adam air flight 574 ... High altitude lost of control after autopilot disconnectedhttps://en.m.wikipedia.org/wiki/Flash_Airlines_Flight_604

The descent rate varied during the fatal dive, with a maximum recorded value of 53,760 feet per minute,
From memory, I believe that the descent profile of the Adam air is quit similar of the one seems to be seen here.

I also remember a pilot suicide, with the pilot banking the plane high altitude and also same very fast descent from high FL to ground in few minutes, forgot which plane thought. Not saying it what happened there, but descent profile would also fit.

[172_driver]

West Air Sweden CRJ200 instrument failure at FL330 in darkness, causing spatial disorientation, is at first glance quite similar to this.

[Jason74]

It might be helpful for the discussion here (as amateur speculations are not deleted) for professionals here to 1) state their credentials and 2) list causative factors that can be ruled out, given the extremely minimal information available.

That might help the readers here with a baseline against which these drive-by amateur comments can be measured.

Credentials:
15 years Royal Australian Air Force. Qualified on PC9, C-130, Macchi MB-326, F/A-18, Hawk-127. Qualified Flying Instructor, Instrument Rating Examiner, Low Level Demonstration Pilot, Flying Safety Officer.
15 years airline pilot. Captain on A350, A330.

Causative Factors:
Absolutely no idea. How could I offer an opinion before the data is in?


My deepest condolences to the families of those involved.

[CW247]

All 737-800s at MU are grounded
My hunch is a runaway trim.

[Salina Chan]

All 737-800s at MU are grounded.
says who? FR24 seems to disagree, there are about ten of their 738s in flight as of this posting

[logansi]

Interesting new data in the more granular data from Flightradar24

If the reporting is correct it seems to show that for a short period the crew recovered, gained altitude before the dive resumed.

https://cimg2.ibsrv.net/gimg/pprune.org-vbulletin/1105x890/foxjcxmxeaembgv_1__c9fd76537c1136b809bba4ed125f8c4dcaf384fd. png

[Cool banana]

This appears to be the lower outer wing structure, with the fuel tank blow out panels missing,

https://cimg9.ibsrv.net/gimg/pprune.org-vbulletin/983x773/b737_china_539128f74b5c1a87c81108ba3f0f672f0df2f4f7.jpg
From Weibo, Aircraft debris near the scene of the accident.

[A320 Glider]

Guys, do you remember Germanwings? I stated early on in the discussion that a plane doesn't go from cruise to crash very quickly. I was immediately mobbed on here when I suggested it was suicide. Now the bells are ringing again nearly 7 years to this day (24th Mar) and again I am being mobbed for saying this looks like a suicide event.

I have been on PPRuNe a lot longer than most that say don't speculate.
I do not fly the 737 but many on here do and this will be unfortunately another learning event for us all.

It is healthy for us to have a grown up discussion regarding accidents. This is how we learn in the industry. Our checklists, procedures and everything we do are unfortunately written in the blood of our deceased colleagues.

[aeromech3]

From eagle 21 picture. Well the rudder is composite and the blue ends at the trailing edge; strange how some rivets are torn through and others just popped; the aluminium non painted piece looks whole and with no external paintwork unlikely the nose of the rudder, presume could be a back closing panel of the V.fin where the nose of the rudder swings, the green bracket also that area. and so rudder flutter and delamination less likely in MHO.
JAL123 a B747 RPB repair failure leading to an over pressurisation in the tail section comes to mind, though it is unlikely to have been started in this case by a cabin air loss as blow out vents are now designed to cope with this..

[A320 Glider]

JAL123 a B747 RPB repair failure leading to an over pressurisation in the tail section comes to mind, though it is unlikely to have been started in this case by a cabin air loss as blow out vents are now designed to cope with this..

Plus the aircraft was at cruise for quite some time.
If it was a structural failure due to pressurization, it would have occurred a lot sooner in the flight (i.e. during climb, just like JAL123 and CAL611).

[henra]

Interesting new data in the more granular data from Flightradar24

If the reporting is correct it seems to show that for a short period the crew recovered, gained altitude before the dive resumed.

https://cimg2.ibsrv.net/gimg/pprune.org-vbulletin/1105x890/foxjcxmxeaembgv_1__c9fd76537c1136b809bba4ed125f8c4dcaf384fd. png

Speed vs. vertical speed doesn't seem to make much sense. Maybe timing issue between the columns?

[dr dre]

All 737-800s at MU are grounded
My hunch is a runaway trim.

In the 3 recent incidents of 737 runaway trim (2 MAXs and Fly Dubai at Rostov) the descent angle with the runaway nose down trim was at a max about 45 degrees. The two social media videos of this incident indicate a far greater descent angle.

Plus there was a period of erratic flight prior to the final nose down pitch and descent, this incident seems to have suffered an almost instant controlled flight in cruise to near vertical descent.

[Silver Shadow]

Photos of large pieces of debris on the ground do not seem consistent with being part of the plane when it slammed into the ground. Detached prior? Location where found??

[Kenny]

A total of 132 people on board, made up with 123 passenger and 9 crew members, so at least one or both jump seats would had been occupied during the flight, that should rule out hijacking or suicide possible cause.

If you mean the cockpit jump seats must have been occupied, not all 73’s come with the second JS. 5 cabin crew and 2 pilots, might have simply meant that 2 cabin crew were in the CC jump seats.

Last time I saw a flight track like that and a vertical dive to the end, was the Alaska Airlines loss of Stab.

[Hogger60]

If you mean the cockpit jump seats must have been occupied, not all 73’s come with the second JS. 5 cabin crew and 2 pilots, might have simply meant that 2 cabin crew were in the CC jump seats.
Most Chinese airlines have at least 3 or sometimes 4 pilots. I've seen many crews with Capt, FO, SO, and 1 stripe cadets walking to the airplane. So my guess is 4 pilots and 5 cabin crew.

[diclemeg]

Germanwings didn't go from cruise to crash very quickly... it was a slowish descent into the mountain. Nothing like this.

You are correct...however there was another suicide crash by a disgruntled asian pilot, that looks like this. I think it was Silk Air in Indonesia.

[Christodoulidesd]

how about cut-off broken rudder like the American Airlines Flight 587 a310 in new york in 2001?

[DoggyWoggy]

Who remembers the Air Nippon 737-700 incident where the copilot was trying to let the Captain back into the cockpit and accidentally mistook the rudder trim wheel for the cockpit door switch? The pilot ended up putting the aircraft in a 30000ft/min descent with almost full uncommanded rudder deflection.

Unfortunately I can’t post links because I’m below 10 posts but a quick Google of ANA 117 will come up with results (https://japantoday.com/category/national/ana-pilots-unaware-for-20-seconds-that-plane-was-almost-turning-upside-down).

[tupungato]

how about cut-off broken rudder like the American Airlines Flight 587 a310 in new york in 2001?

It was A300, not A310.

[EI_DVM]

A rudder hard-over and the resulting bank could likely result in these sorts of rates of descent.

Though personally my mind is quite open as to the cause at this stage.

Initially I'd speculated a deep stall, with the crew unable to get the nose down based on the initial reported VS similar to AF447, however the since revealed fairly consistent and then increasing GS seems to make this appear less likely for now as well as the cruise altitude of FL290 would have a significant margin away from coffin corner.

In my experience emergency descents even with full speed-brake in the Mach to Speed transition only tend to result in a VS of 8,000-9,000 fpm before quickly stabilising at about 4,000-5,000fpm once the transition to speed is complete which seems incompatible with this VS, particularly given the aircraft was pretty much at the MACH/Speed cross over altitude or there abouts.

Wings falling off or other structural failure seems a possibility, this should be able to be determined within the next few days should the debris of the wings or tailplane be found a distance from the main fuselage wreckage.

A suicide possibility exists, but it would have to be very drastic to get the airplane into that sort of attitude, and then the short recovery of altitude before the final dive seems to indicate there was an attempt to recover. IIRC the German Wings incident involved a much more tame 3,500-4,000fpm descent as well with no attempted recovery.

All speculation for the next while.

[procede]

Could trim or pilot input get the attitude so nose down? I would think you would need a complete failure of the elevator and/or horizontal tail.

[Christodoulidesd]

stand corrected sir

[Australopithecus]

Absolutely not suggesting it to be the case, but the lower wing skin in that condition makes me wonder about the recent pickle fork AD.

[vilas]

Not only it is very possible to put a 737 in such a dive, it's also impossible to pull it out from a high speed dive. It's not a protected aircraft. It was put in 65° dive in Rostov on don, in JAL incident it rolled on the back due to inadvertent rudder trim before it was pulled out. If it was mishandled then it could have easily entered into inverted dive. No surprises there.

[ETOPS]

My guess - stab trim runaway not noticed by crew. Autopilot eventually gives up an disengages leading to violent pitch down. Crew figure out what’s wrong and retrim only to overstress during the pullout.

[Compton3fox]

​​​​​
If it is not in China it doesn't count ? ...

Flash airline flight 604, malfunction lead to autopilot disconnected and pilot not controling their aircraft, that it is low altitude doesn't change anything, high altitude make it even more easier to loose control.

Adam air flight 574 ... High altitude lost of control after autopilot disconnectedhttps://en.m.wikipedia.org/wiki/Flash_Airlines_Flight_604

The descent rate varied during the fatal dive, with a maximum recorded value of 53,760 feet per minute,
From memory, I believe that the descent profile of the Adam air is quit similar of the one seems to be seen here.

I also remember a pilot suicide, with the pilot banking the plane high altitude and also same very fast descent from high FL to ground in few minutes, forgot which plane thought. Not saying it what happened there, but descent profile would also fit.

Would that be Silkair 185 you are referring to? https://en.wikipedia.org/wiki/SilkAir_Flight_185 I recall the tail section separating from the rest of the A/C during the resulting near vertical dive.

[Magplug]

As a lifelong professional jet pilot I make a couple of observations.

- A runaway trim that is not detected(?) will put the aircraft into an uncontrollable dive - but NOT a vertical one.
- This a/c seems to have been just fine and stable right up to the point it left cruise altitude approaching destination
- The fact we are seeing lots of panels on the surface with pulled rivets suggests design forces were exceeded in flight leading to structure break up. The rest of the structure is in a very deep hole.
- No conclusions can be drawn from the FR24 data that a recovery was being attempted. This aircraft had departed controlled flight suddenly and catastrophically

For me the circumstances are very similar to Metrojet 9268 (EI-ETJ) that crashed in Sinai. When the four corners are established we may well find that the empennage is not located with the main body of the wreckage indicating separation. The list of causal factors for that separation at the end of a stable cruise is a very short list indeed.

[Propellerhead]

Runaway trim is pretty obvious in a 737 as the trim wheel makes a loud clattering noise as it turns. A prolonged turning of the wheel is not something you’d expect in the cruise. And you can stop it by putting your hand on the wheel.

[Cool banana]

China Eastern pilots’ policy is both crews must be seated 20 mins prior to TOD. This was well past that point.



This is an 6 year old aircraft, but from the data available it looks like a catastrophic failure or a midair collision with a military aircraft/drone.

Any Thunderstorm activity or CAT located close to the TOD? haven't seen any Mid / High Level Significant Weather Chart for that area.

[Matt48]

The video appears to show the aircraft either side on with no vertical stab, or a fuselage stripped of all flight surfaces.
Either way, RIP to all souls onboard.
Very sad outcome for all concerned.

[Salina Chan]

China Eastern pilots’ policy is both crews must be seated 20 mins prior to TOD. This was well past that point.



This is an 6 year old aircraft, but from the data available it looks like a catastrophic failure or a midair collision with a military aircraft/drone

the thought occurred to me as well, something akin to the GOL mid-air - although the GOL 73 broke up at some point on the way down iirc.

[procede]

Speed is groundspeed, if the aircraft is not travelling horizontally it is going to be erratic

I would think it is (true) airspeed, as transmitted by the transponder. If this was groundspeed, it would not correspond with a dive.

[threemiles]

I would think it is (true) airspeed, as transmitted by the transponder. If this was groundspeed, it would not correspond with a dive.
It is Ground Speed indeed. It comes in a packet called Velocity from which Ground Speed and True Track can be derived.
No further speculations on the values, could be a number of reasons.

[fdr]

Is this part of the rudder (a/c right)? When comparing the paint scheme it seems like it is the only place that it could come from. Is so it has been found away from the fire
https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/864x1920/3a9746aa_f0c1_42f0_bdd4_edb11def99b7_8447f820376f5456e968368 cb828bc1f4cef162f.jpeg

Last bits that looked like that I examined had a flutter-type event from going deep into the buffet boundary. Shredding laminate is not a very common failure mode.

Sad day.

There had been some convective weather around that area.

[Havingwings4ever]

Ran video(of showing an object coming down in a vertical arc trajectory) by a friend who put it through a forensic video editing program, he does this for a living.

I am pretty confident seeing the resulting video that the tail section is not present during the length of that video. Wing and engine on 1 side seems present but not sure, other side not visible.

Analysis of FR24 data indicates in last 2 minutes an abrupt extreme vertical descent followed by a steep vertical ascent, followed by a final extreme vertical descent till impact. Continuous loss of altitude with a temporary 'leveloff' after the 'climb', followed by increasing extreme rate of altitude loss.
I am not familiar with the airspeed data from FR24.
Pictures are showing popped rivets in several parts of the fuselage indicating over exceedance of design limits.

Somehow crew lost control of the vertical flightpath; likely loss of tail section, immediate or during the last 2 minutes of flight.
failure of rear bulkhead, collision in the air, runaway trim,we are just guessing right now.

Crew seems to have been fighting to get the aircraft recover from the initial steep abrupt vertical descent. Must have been horrific those last 2 minutes.

May their souls be at peace.

30 year plus airline/instructor Boeing/MD's/Airbus, lot of hand flying

[A320 Glider]

exact point they would have been expected to commence descent.

The FO suggests the captain use the washroom before TOD. Captain obliges. Tries to return.

RIP to the crew and pax. Terrible tragedy whatever the explanation is.

[awqward]

It is Ground Speed indeed. It comes in a packet called Velocity from which Ground Speed and True Track can be derived.
No further speculations on the values, could be a number of reasons.

I think it depends on whether the FR24 data is derived from ADS-B or Multi-Lateration (MLAT)… GS is calculated simply by time between horizontal fixes…

https://www.flightradar24.com/blog/how-we-track-flights-with-mlat/

[fdr]

For educational sake, the vertical tail surface is called a vertical stabilizer. The rudder is the movable control surface at the aft end of the vertical stabilizer. In the flight 587 case you share the video of the entire vertical stabilizer departed the aircraft due to overstress from improper rudder inputs.

AA587's loss had a number of factors going on, and for an event in Nov 2001, the term "improper" loses a bit of it's crispness as causation.

The FO who was PF had experience in aircraft that were able to take aggressive control inputs.
The Airbus manner of giving a rudder ration limiting effect does not act to reduce the sensitivity of the input, ti does the exact opposite; instead of the Boeing method of reducing the deflection for a given deflection of pedal input to reduce loads, the bus does the opposite, it reduces the pedal deflection available, to reduce the rudder deflection, and that means for a given aero load, the Airbus sensitivity of the rudder pedals becomes more sensitive.
The certification of the load sequence of the rudder was not required to be accounted for in the loads analysis or in the TIA.
the sequence of alternating deflections coinciding with high yaw angles resulted in very high bending loads, and the rudder deflection added alternating torsion loads, and they went wild.
The vertical stabiliser was mounted by a series of pins running longitudinally along the perimeter of the composite stabiliser to fix the primary load paths. The secondary load path was by an internal yoke system.... the load required to shear the attachment lugs results in a lever arm for the structure that exceeds the failure loads for the secondary structure, as the lug/pin failure results in a lever arm acting on the secondary structure.
AI and TBC both had guidance for jet upset that had crew pre primed (a Gary Klein sort of concept) to wiggle them pedals.
The awareness of the structure sensitivity to alternating torsion-bnnding was not recognised in Part 25 before the accident.


We know a lot more after that event than we did beforehand. Amazingly, we were recording QAR/DFDR data of cyclical rudder imputs after that disaster, with the penny not dropped.

[BFM]

Sad. Interesting though; that video seems to show the fuselage going supersonic with characteristic vapour puffs. I thought at first it was disintegration debris, but review does not confirm that.

[377 Pete]

Last three minutes of MU-5735

https://cimg2.ibsrv.net/gimg/pprune.org-vbulletin/2000x1064/mu_5735img_3b624abfc51728322157c19fc7fbdb36796dcb33.jpg

[spiros737]

The sheets parts looks like they have been torn by high aerodynamic pressure. the loss of the rudder may have led the plane to a major descent.

[jewitts]

Ran video(of showing an object coming down in a vertical arc trajectory) by a friend who put it through a forensic video editing program, he does this for a living.

I am pretty confident seeing the resulting video that the tail section is not present during the length of that video. Wing and engine on 1 side seems present but not sure, other side not visible.

Analysis of FR24 data indicates in last 2 minutes an abrupt extreme vertical descent followed by a steep vertical ascent, followed by a final extreme vertical descent till impact. Continuous loss of altitude with a temporary 'leveloff' after the 'climb', followed by increasing extreme rate of altitude loss.
I am not familiar with the airspeed data from FR24.
Pictures are showing popped rivets in several parts of the fuselage indicating over exceedance of design limits.

Somehow crew lost control of the vertical flightpath; likely loss of tail section, immediate or during the last 2 minutes of flight.
failure of rear bulkhead, collision in the air, runaway trim,we are just guessing right now.

Crew seems to have been fighting to get the aircraft recover from the initial steep abrupt vertical descent. Must have been horrific those last 2 minutes.

May their souls be at peace.

30 year plus airline/instructor Boeing/MD's/Airbus, lot of hand flying
My first thoughts on seeing the raw video. Some of the debris, not found in the hole, seem to be winglets and other wing or tail parts. Maybe nothing to do with the cause.

[Cool banana]

My first thoughts on seeing the raw video. Some of the debris, not found in the hole, seem to be winglets and other wing or tail parts. Maybe nothing to do with the cause.

https://cimg2.ibsrv.net/gimg/pprune.org-vbulletin/750x450/china_e_b6aecbcbeadf789f903eab46d782a299cc1c747b.jpg
Right Wing tip.

Let see what the investigating team comes up with.

[kenparry]

Ref the wing parts that appear to have separated, I suspect from their state and the descent profile, that the aircraft reached its divergence speed and the outboard wings came off. This would not be the root cause, but an indirect result of an earlier problem that produced the extreme dive angle. It has happened before - a B737-200 flown by Copa (Panama) sometime in the 90s.

[Compton3fox]

Looking at the last data points: GS 376kts VS 30976 ft/min = ~305 kts. Decent angle is arctan(305/376) = 39 degrees. <please check my maths!> Based on the video evidence, it suggests that AOD increased markedly in the very last phase of the decent. Maybe up until this point, the A/C was relatively intact but suffered some significant break up close to the ground.

[Auxtank]

Looking at the last data points: GS 376kts VS 30976 ft/min = ~305 kts. Decent angle is arctan(305/376) = 39 degrees. <please check my maths!> Based on the video evidence, it suggests that AOD increased markedly in the very last phase of the decent. Maybe up until this point, the A/C was relatively intact but suffered some significant break up close to the ground.

Your maths is intact. So something on FR24 didn't catch it - which is hardly surprising, the algo's on FR 24 are designed to be as accurate as possible in conventional flight profiles - not this sort of thing.

Somebody made a graphic here; you can see some attempt at recovery, maybe (at 06:22:16 UTC) - or, change of configuration of surfaces (non-pilot initiated, e,g; further structual failure) resulting in change of flight path. Or, again. this could be FR24's Algorithyms's interpolating unusual data and as a result plotting erroneous trajectory.
Obviously, the blue aircraft symbol is not representative of the aircraft's attitude but simply it's position in altitude and even then - only very approximately and exaggerated for illustration purposes.

So a pointless task of guessing. The only thing that will clarify what happened is the boxes.



https://cimg6.ibsrv.net/gimg/pprune.org-vbulletin/525x680/foxfdtyamammxju_f63a467346a7251362c0bdde67c4d48d4046b0fb.png

[C2H5OH]

The dashcam video Dominic Gates had on his Twitter feed [can't post links] does look more like 45 degrees.
I tend towards seeing a vertical stabilizer - but it's tough.

[weatherdude]

Hello, since it was mentioned earlier in the thread:

Doesn't look like anything remarkable, you can click into the district or change time if needed.

Visible sat pic (https://weather.us/satellite/henan/satellite-hd-10min/20220321-0620z.html)

IR Sat pic (https://weather.us/satellite/henan/top-alert-10min/20220321-0620z.html)

Lightning detection (https://weather.us/lightning/henan/20220321-0625z.html)

[tubby linton]

Hello, since it was mentioned earlier in the thread:

Doesn't look like anything remarkable, you can click into the district or change time if needed.

Visible sat pic (https://weather.us/satellite/henan/satellite-hd-10min/20220321-0620z.html)

IR Sat pic (https://weather.us/satellite/henan/top-alert-10min/20220321-0620z.html)

Lightning detection (https://weather.us/lightning/henan/20220321-0625z.html)
Any CAT or mountain wave forecast?

[weatherdude]

Some decent tailwind, but nothing out of the ordinary afaik (https://weather.us/model-charts/german/2022032100/henan/wind-300mb/20220321-0600z.html)

[A320 Glider]

Any CAT or mountain wave forecast?

Dear Sir, please can you tell me if any airliner in modern commercial aviation history has been brought down by lightning or CAT?

Looking at FR24 data, did they overshoot their TOD? Did they try and rush the descent and something happened? The investigators will be checking out the maintenance history of this bird. It's a fairly new plane but has it had any repairs recently? What about tail strikes lately?

[pattern_is_full]

Rudder or the whole vertical stabilizer sheering off wont create such a rapid fall. Remember there is airspeed and Ailerons and Elevators should still be effective, assuming symmetrical thrust. Only the directional control is lost.
Intentional dive or Runaway nose down stabilizer is what I can think off. The video seems too unrealistic.

What do you suppose the loss of a ton of weight (VS) from the extreme aft of the fuselage (long lever arm) would do to the CoG? I would expect a severe and probably uncontrollable nose-over.

https://www.pprune.org/archive/index.php/t-457960.html

What would it do to the integrity of the hydraulic lines running to the rudder? And thus the availability of hydraulic control pressure for elevator operation?

[Wycombe]

Dear Sir, please can you tell me if any airliner in modern commercial aviation history has been brought down by lightning or CAT?


If it counts as modern, a BOAC B707 was brought down by severe CAT in Japan in 1966

BOAC 911 (https://en.wikipedia.org/wiki/BOAC_Flight_911)

The investigation concluded that the vertical stabiliser came off first.

[clark y]

The Flightradar24 table presented earlier shows a speed of maximum speed of 590kts around the point of the vertical speed reversal. The airspeed was possibly faster. Very fast for an airliner at 8000'. As for the G loading at the point of the vertical speed reversal, my guess is it was probably very great in the positive or even negative direction.

[henra]

What do you suppose the loss of a ton of weight (VS) from the extreme aft of the fuselage (long lever arm) would do to the CoG? I would expect a severe and probably uncontrollable nose-over.

Past cases of such occurences tend to show otherwise. Neither the B-52 which lost 3/4 of its VS nor AA587 nosed over. Problem with lost VS is loss of directional control in Yaw.
Massive nose overs have occured in the past (in Military and General Aviation) as a consequence of losing Horizontal stabilizers. If the FR24 is valid this could potentially happen due to exceeding the structural limit in the first apparent recovery (if the FR24 traces are correct). That said in one of the videos the final trajectory rather looks like 50° ND and possibly with a slight recovery path. The other video on the other hand looks pretty vertical. Simply not possible to safely conclude from the few bits we have. First important information bit to obtain woould be the four corners. After that there is a first chance to get a somewhat clearer picture.

[Cool banana]

[QUOTE=fdr;11203404]Last bits that looked like that I examined had a flutter-type event from going deep into the buffet boundary. Shredding laminate is not a very common failure mode.


https://cimg2.ibsrv.net/gimg/pprune.org-vbulletin/864x1920/ce_5ab2bdc9cce4bd6a53e939dafd2ac33e2818dfce.jpeg
more parts of the right wing tip mid leading edge and inboard right logo panel

That is part of the wingtip not the rudder

[Consol]

Re a previous poster's comments about asymmetry, the track was remarkably constant until the 30000ft/min descent rate was well established. This implies the autopilot may have remained engaged for some time. Even an engine failure with autopilot engaged would show some track change.
Edited,
There was also clearly a recovery and even a brief climb so the initial upset event cannot have been totally catastrophic.

[Auxtank]

Re a previous poster's comments about asymmetry, the track was remarkably constant until the 30000ft/min descent rate was well established. This implies the autopilot may have remained engaged for some time. Even an engine failure with autopilot engaged would show some track change.

That was me and all I was saying was that the more unusual and "in extremis" the flight path - the more FR24 data can be discarded as inaccurate - and in this case with what seems to be the case, absolutely discarded. We know it dived, that's all we know. FR24 cannot reveal anything more at this point. Anyone chasing FR24 for facts about causal factors is chasing windmills.

[MACH6]

Unfortunately PILOT SUICIDE is the most likely reason for this crash.

Rudder hardover, Stab trim runaway, mishandling a depressurisation WILL NOT result in a descent profile like this. I’ve tried it in the sim and the descent profiles are NOT near vertical like this.

SILKAIR flight MI 185 is a very similar example to compare. Deliberate, sustained pilot input with stab trim at full manual nose down and a high thrust setting was determined as the cause of this crash by the NTSB as an addendum to the final report.

[7478ti]

- Profound sympathy to the crew, pax and their families.
- More data is needed to even start any credible assessment. Like the distribution of remaining identifiable parts, any ATS communication, preliminary failure mode of identifiable pieces, etc.
- an ultimate pitch tuck can have many many root causes
- much of the above speculation is both technically way off-base, and very unfair to the families of the lost flight crew, pax, ....and even to the airline at this point.
- let's hope a credible internationally staffed accident team can be fielded ASAP, and the results honestly, credibly, and quickly reported.
- There are just too many NGs we're flying out there, to not have credible bounds being placed on the inaccurate speculation now being distributed... ASAP.
- Let's hope for usable DFDR, QAR, and CVR data... but in accidents like this, that can be long shot.
​​​​​​- Profound sympathy to the crew, pax and their families.

[mrdeux]

I'm a tad suspicious of the video. It looks very much like one of a crashing Long March booster from a couple of years ago.
https://cdn.images.express.co.uk/img/dynamic/151/590x/secondary/China-rocket-crash-Long-March-booster-2656263.webp?r=1599550692168

[PAXboy]

In trying to ascertain what speed it was falling at, does anyone know what ther terminal velocity would have been - and how long to reach that from the start of the fall? The media are putting all sorts of numbers on the vertical speed, doubtless some from here.

[etrang]

As a general question, how reliable is Chinese accident investigation and reporting?

[ChicoG]

Yeah who would hv a camera pointing at some random point at a mountain?

It was reportedly CCTV footage from a nearby mining operation playing on TV, filmed on a mobile by someone.

[LNAV VNAV -]

The thing is, the speed is constant until the descent starts. If altitude was maintained after an engine failure, there should be a decrease in speed.

[A30_737_AEWC]

Final FlightRadar position has a decent [sic] rate of 31,000 fpm

While ~31,000 fpm is a decent velocity, I think we are talking about descent rate.

Of all the places, I'd have thought folks here would have known what they were talking about :ugh:

I wouldn't even call it a descent rate. It was a terminal dive. I wonder what the engines were doing ?

[jeepjeep]

https://cimg7.ibsrv.net/gimg/pprune.org-vbulletin/750x702/still_of_descent_video_mu_5735_d14efc0bda9bf75681b4f0b2601b2 d264cde4a84.jpg
MU-5735 descent video still

[jeepjeep]

https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/360x800/wing_structure_mu_5735_57f3adb9072b76dcb07c4026d975b8a6be940 45e.jpg
Wider view of wing structure MU-5735

[Dim Sum]

https://cimg7.ibsrv.net/gimg/pprune.org-vbulletin/750x702/still_of_descent_video_mu_5735_d14efc0bda9bf75681b4f0b2601b2 d264cde4a84.jpg
MU-5735 descent video still

The video from this still is real. The guy in the video speaks Cantonese with a really heavy accent and the two words I understood was "直落" which means "straight down." There are two provinces in the whole of China (besides HK and Macau) where locals speak Cantonese.. Guangxi (where the plane went down) and Guangdong.

Too many armchair experts in this thread :ugh:

[krismiler]

With the two MAX disasters being so recent, any B737 pilot should have been fully up to speed on dealing with stab trim malfunctions. Surely this would have been highlighted by the training departments of all B737 operators, with a relevant exercise being included in the required training or testing sessions.

As the aircraft was a passenger varient, a massive CofG shift due to unrestrained cargo seems unlikely.

An Alaska Airlines flight 261 scenario with the stabilizer commanding full down pitch due to mechanical failure or improper maintenance would be one of the first possibilities to look into. Perhaps an issue similar to the rudder hard overs experienced back in the 1990s has reared its head.

Pilot suicide or unlawful interference are possible as well.

[Turkey Brain]

A “ Jet upset “ is a strong possibility.

Any distraction to the flying of the plane or a control problem at altitude can become a crash.

As the aircraft approaches high Mach speed the lift moves back, due to Mach effects. The nose lowers more and only in lower thicker air does the elevator have sufficient control authority.

Most modern airplanes have a Mach Trim, which will apply nose up stabiliser to help control this effect.

The issue is, if the plane’s speed is not controlled adequately early on in the descent, then the airspeed loads or manoeuvring loads in the lower thicker air can destroy the airframe.

See Wiki for “ Jet Upset “ and also “ China Airlines 006 Feb 1985 “.

The 747 tail plane has chunks missing from the near supersonic descent. It’s incredible it survived.

( Apparently part of the reason the 747 survived is that some of the gear fell down, breaking the up locks as it was pulling 5 g, the extra drag helped to limit the airspeed.)

So this aircraft ended up going very fast with bits falling off it.

Loss of control at altitude due to Mach effects can lead to rapid airspeed build up and excessive air loads in lower thicker air.

This 737 unfortunately seems to have had a very rapid descent, for whatever reason leading to inflight breakup.

[QDM360]

A lot of folks seem to take it as a fact that the aircraft was temporarily recovered, briefly climbing, just before crashing - according to the tracking site. Watching the videos, if they are accurate, this seems highly unlikely though.

Remember, the altitude data from ADS-B / FR24 site is a barometric pressure reading transmitted by the aircraft itself only. Sure, in normal flight, a reduction in barometric pressure correlates with a gain in altitude. But when an aircraft left controlled flight, there are other reasons which could cause a temporary reduction in barometric pressure at the static port - which would falsely be interpreted as a brief climb.

So, what you should take as a fact is: we don't know...

[FlightDetent]

Industry rumours there may had been significantly in excess of a dozen deadheading flight crew on-board.

-- x --

Unlawful interference by overpowering the flight controls by a 3rd party is rather beyond imaginable, given the physical and procedural barriers. Mainline Chinese carriers employ uniformed security guards and cockpit access procedures are strict 100% post-9/11.

-- x --

Was there really a climb segment before the impact? If so, one speculative chain of events:
- upset + loss of control / spatial disorientation at high alt
- high speed dive with severely abnormal attitude in IMC
- break cloud with crew regaining orientation but overstressing the airframe during a belated attempt to avoid crashing which was impossible to pull (no pun).
- partial physical brake-up of aerodynamic surfaces due to overload, namely some of the tail structure
- dismembered hull plunges to the ground.

As clueless as anyone. Is the countrywide grounding of 737-800 by CAAC confirmed?

[allaru]

Credentials:
30 years plus on Boeings, 20 years plus as wide body Captain.

Not being one to speculate but maybe they lost an engine and instead of drifting down stalled the aircraft, then put in the wrong rudder or tried to use aileron to recover the dropped wing then ended up inverted in an energy and attitude state that was beyond their capability to recover from.

But I guess we will only know when the CCP release their transparent report into the incident.

My condolences to all on board.

[Stick Flying]

Let me chime in on this, a long time (2005+) lurker.


Is this trim-mechanism run-away plausible: Ehhhh, yep.



If we are to believe the FR24 data, it does not logically back up a trim runaway scenario. The speed (I'm still unsure whether we are talking G/S or TAS), drops slightly just before descent. This would not be abnormal if this was TOD as the aircraft sequences to ECON descent speeds (Mach). But then at about the time the descent rate increases exponentially, the speed is shown as a good 70-90Kts less than Cruise/TOD schedule. This anomaly lends itself to some other form of event unless the data table has a high inaccuracy capability. Only the CVR/FDR will allow those that analyze these events the opportunity to piece together the possible causes, hopefully arriving on a conclusive reason.

[NSEU]

Trim-switch failures: Could be, though "there are trim-switch-disable switches for that to overcome the issue", so a secondary upset should not have to happen, which did happen in just over a minute.

You understand that yoke trim switches have an "power button" button and a "direction" button? It's unlikely both switches would fail. Also, faulty yoke switch inputs can be immediately overridden by pulling/pushing on the stick in the opposite direction, then the cutout switches can be used.

Avionics maintenance engineer (40 years)

[Andy78]

Any thoughts on how likely serviceability of the recorders will be. Looks like nothing left of the aircraft. Know they are tough, but not indestructible and there was a big fire.

[Mookiesurfs]

Credentials: Retired military and airline pilot

Working backwards, it appears we have a near vertical dive with some associated breakup. How do we arrive in that position? Imo:
1. Catastrophic mechanical failure in cruise - unlikely
2. Pilot suicide - unlikely, plausible.
3. Terrorist act - unlikely, plausible
4. Gradual stab trim until autopilot gives up and kicks off, followed by departure from controlled flight. Recovery attempt overstresses aircraft. - plausible
5. There are many other ways to depart the aircraft and botch the recovery. - all plausible at this point.
We are going to have to wait and see.

[bsieker]

Any thoughts on how likely serviceability of the recorders will be. Looks like nothing left of the aircraft. Know they are tough, but not indestructible and there was a big fire.

The recorders will almost certainly not be serviceable, i. e. they will be destroyed and will not work.

But the memory modules will almost certainly still be readable; they are in some of the toughest enclosures you can imagine, they can protect the memory from shock in excess of 1000 G acceleration, and prolonged hot fires. It is the enclosures' only job to protect the memory modules in precisely this kind of situation. This looks like a head-on crash with a velocity not too different from the Germanwings murder-suicide, so the entire aircraft acts as a crumple-zone reducing the acceleration experienced by the recorders.

The problem will be to find them. This can take weeks.

[lederhosen]

As a long time 737 captain I would say that a 737 loss from at or near cruise altitude is quite an unusual event. But it does remind me of at least one Indonesian loss of control accident (Adam Air?). Flight level 290 is not that high and the chance of being in instrument flight conditions cannot be excluded. Very few airlines encourage manual flight that high and if the airplane departed controlled flight for some reason then the startled crew might not perform a text book recovery. There is some data suggesting the aircraft made a high speed pull out relatively low with the possibility of over stress and ensuing breakup. But that is just speculation. It is a bit of a short flight for fuel imbalance to be a big issue. But technical failure, plain and simple operator error or of course some exterior factor like turbulence could have caused the initial loss of control. The black boxes will hopefully show up shortly and then we will have something firmer to go on.

[FlightDetent]

lederhosen thanks! One of the reasons behind crew losing themselves at the onset (not saying it actually happened) could be a simple but deep confusion.

I recall a guided training SIM session on the Classic with Dual Eng Fail at TOC design to experience exactly that. For the NG, would the resulting electrical configuration & systems remaining be a lot to handle? Startle effect included.

For the sake of exploring the technological consequences of such a scenario.

-- x --

links to some cases already mentioned (varied relevance)

1997 Silk Air 185: Unconfirmed deliberate CFIT
https://aviation-safety.net/database/record.php?id=19971219-0

2007 Adam Air 574: Spatial disorientation
https://aviation-safety.net/database/record.php?id=20070101-0

2015 Germanwings: Pilot suicide
https://aviation-safety.net/database/record.php?id=20190223-0

2019 Atlas Air: Upset due undesired TOGA activation
https://aviation-safety.net/database/record.php?id=20190223-0

[diclemeg]

As a general question, how reliable is Chinese accident investigation and reporting?

Lets not get sanctimonious on our reporting and safety...after all it was the chinese who first grounded the Max.... and if not for them I would bet the FAA wouldn't have, and instead did some sort of software workaround and leave no sensor redundancy on the MCAS.

[FlightDetent]

As a general question, how reliable is Chinese accident investigation and reporting?If it was a collision with military equipment the publishing part will be challenging and not necessarily overcome without a cover story. But no doubt the reason will be found out and corrective actions taken.

One of the power-pillars of a controlling government, anywhere, is providing (a sense of) security to its own people. Falling aeroplanes are cross with the marketed purpose.

On top of that, as W.C.'s far eastern twin would have said: "Never let a good uproar go to pass without public punishment."

[Organfreak]

No, logic tells us that we don't know yet WHAT happened.

[FlightDetent]

If atlas air 3591 had happened at FL290 Firewalling the thrust levers from stable cruise will have a marked pitch-up but nowhere near what's required to cause an upset. At FL290 the engines operate near maximum available thrust for thermodynamic and engineering efficiency anyway.

The second part, overzealous pushover and nosedive, might be similar. But the trigger needs to be a different one.

As well, noted by wiggy earlier, the geometry of TLs in their forward cruise position places the TO/GA buttons out of the way, not to mention those are completely different designs between 767 and 737. Or someone reaching for the flap lever at that altitude...

I linked the accident report only for completeness, the dynamics look uncorrelated IMHO.

[bsieker]

[in reply to a questions about Chinese accident investigation quality]


[...]
But no doubt the reason will be found out and corrective actions taken.
[...]


I agree. Also keep in mind that under ICAO rules they are required to allow representatives from the country of aircraft design (USA) and aircraft manufacturer (also USA) to participate in the investigation:

5.18 The State of Registry, the State of the Operator, the State of Design and the State of Manufacture shall each be entitled to appoint an accredited representative to participate in the investigation.

They won't have a say in the report, but will be allowed to observe, and can write their own additional, if unofficial, reports.

Traditionally, the engine design and manufacturing companies also request and receive permission to send representatives, but there is no such obligation under ICAO Annex 13.

[visibility3miles]

The video from this still is real. The guy in the video speaks Cantonese with a really heavy accent and the two words I understood was "直落" which means "straight down." There are two provinces in the whole of China (besides HK and Macau) where locals speak Cantonese.. Guangxi (where the plane went down) and Guangdong.

Too many armchair experts in this thread :ugh:

The angle of the video relative to the flight path could make it seem like it was going straight down.

If the video was taken perpendicular to the flight path, then that would be correct.

If it was taken parallel to the flight path, it might not have been able to pick up a horizontal component of the plane going away from the video camera.

Either way, it shows a high rate of descent.

I’ll leave it to others to map out where the camera was relative to the flight path and won’t post again on this thread.

[CommanderCYYZ]

I have not seen anything relating to ATC chatter anywhere. I have no experience with Chinese ATC. Is it something that we are likely to see released, or will it fall into the CCP information void?

[xji]

I have not seen anything relating to ATC chatter anywhere. I have no experience with Chinese ATC. Is it something that we are likely to see released, or will it fall into the CCP information void?

(Not a professional, just somebody following the news, so my terminology is off.) The latest news from today is that they entered the air control zone of Guangzhou not long before the crash. The ATC noticed that they started a steep dive and repeatedly tried to reach them, but got no reply whatsoever until the end.

[WideScreen]

If we are to believe the FR24 data, it does not logically back up a trim runaway scenario. The speed (I'm still unsure whether we are talking G/S or TAS), drops slightly just before descent. This would not be abnormal if this was TOD as the aircraft sequences to ECON descent speeds (Mach). But then at about the time the descent rate increases exponentially, the speed is shown as a good 70-90Kts less than Cruise/TOD schedule. This anomaly lends itself to some other form of event unless the data table has a high inaccuracy capability. Only the CVR/FDR will allow those that analyze these events the opportunity to piece together the possible causes, hopefully arriving on a conclusive reason.
Looks like your speed qualification assumptions are wrong. The FR24 speed data is Ground Speed. So, when the airplane goes down vertically, the Ground Speed will show zero, while the TAS can and will be enormous, largely above VNE, even the speed of sound (hence the reports about "booms") can be reachable.

Your assumption about a decreasing "speed" in the FR24 data, happening before the upset is wrong. Only once the upset starts, the Ground Speed goes down, understandable, since the airplane is diving with more 20K ft/min. So no anomaly in the reported FR24 speeds.

[WideScreen]

You understand that yoke trim switches have an "power button" button and a "direction" button? It's unlikely both switches would fail. Also, faulty yoke switch inputs can be immediately overridden by pulling/pushing on the stick in the opposite direction, then the cutout switches can be used.

Avionics maintenance engineer (40 years)
Somehow, this forum is leaking valuable postings, something I have noticed more and more, especially over the past 5-10 years.

Of course, the trim switches are as you describe, though that does not imply, a trim-runaway is impossible. Hence, the presence of the double trim cut-off switches. These are there, because these are regulatory and technically needed.

[Auxtank]

I keep coming back to the (speculated and in no way confirmed) fact that they were TOD.
TOD in the 738 is fairly benign;
A few buttons punched on the FMC- VNAV Checked, etc and on the MCP- ALT put in (and depending on whether it was VNAV or only LNAV - V/S - can you really go sooo wrong doing any of that? Other FMC Inputs at that time pertain to Flap select for Landing, etc - nothing to do with anything directly connected to changing the physical config of the aircraft at that time.
and the Checklist is only;

Pressurization
Recall
Autobrake
Landing Data
Approach Briefing

So there's nothing mechanical there that moves anything physical on the airframe. (Apart from Autobrake dial on the MIP)
It's so wierd - TOD is like the last phase of flight where something suddenly goes so completely wrong. The only thing you can do on the MCP (and that's the only thing you actually touch apart from selecting your Autobrake setting on the MIP) at TOD to crash the aircraft is dial in ALT 0 and V/S 8000/FPM. That will get you spat out. But to do that the bloke sitting next to you - checking your work - would have something to say about it. And if it was me - I'd challenge you as to why you'd dialled in those Extreme MCP ALTS and V/S and if you wearn't making sense I'd probably knock you out and have you removed from the cockpit.

It doesn't make sense - it just fell out of the sodding sky. For me that makes it Mech Fail. Something went 'Twang' and it became unrecoverable (with the best will in the World being flown up front) but I have absolutely no idea how or why. But I am very anxious to know.

RIP

[YukonHusky]

[in reply to a questions about Chinese accident investigation quality]

I agree. Also keep in mind that under ICAO rules they are required to allow representatives from the country of aircraft design (USA) and aircraft manufacturer (also USA) to participate in the investigation:

They won't have a say in the report, but will be allowed to observe, and can write their own additional, if unofficial, reports. Traditionally, the engine design and manufacturing companies also request and receive permission to send representatives, but there is no such obligation under ICAO Annex 13.Barring an unusual CCP exception, mainland China Covid regulations will require any country of aircraft design, aircraft manufacturer, etc representatives to quarantine for 3 weeks (first, 2 weeks in mainland Central Government-quarantine hotel plus 1 additional week in other hotel/residence). Potentially, less than ideal 3 week+ investigation observation delay.

[43Inches]

The profile plot from post #52 is interesting as it does not show a "vertical" drop, probably more likely between 30-40 deg trajectory. I also agree with a post that highlighted the two ADSB blips where there is an extended gap between responses of say 15 seconds, where both steep descents seem to originate, was there some sort of electrical fault or factor? From both ADSB cutouts the aircraft initiates a steep descent and lurches left, from what the plot shows. After the first there seems to be a turn of sorts back to the right and some recovery action by 10,000 feet then a second gap in returns and it goes back into the final steeper profile.

[Wellfan]

The recorders will almost certainly not be serviceable, i. e. they will be destroyed and will not work.

But the memory modules will almost certainly still be readable; they are in some of the toughest enclosures you can imagine, they can protect the memory from shock in excess of 1000 G acceleration, and prolonged hot fires. It is the enclosures' only job to protect the memory modules in precisely this kind of situation. This looks like a head-on crash with a velocity not too different from the Germanwings murder-suicide, so the entire aircraft acts as a crumple-zone reducing the acceleration experienced by the recorders.

The problem will be to find them. This can take weeks.

Doing a quick and dirty calculation on the g force the black box is likely to have experienced on impact (based on velocity figures that were calculated earlier in the thread), the memory modules will have survived by a fairly comfortable margin

[unworry]

I keep coming back to the (speculated and in no way confirmed) fact that they were TOD.
TOD in the 738 is fairly benign;
A few buttons punched on the FMC- VNAV Checked, etc and on the MCP- ALT put in (and depending on whether it was VNAV or only LNAV - V/S - can you really go sooo wrong doing any of that? Other FMC Inputs at that time pertain to Flap select for Landing, etc - nothing to do with anything directly connected to changing the physical config of the aircraft at that time.
and the Checklist is only;

Pressurization
Recall
Autobrake
Landing Data
Approach Briefing

So there's nothing mechanical there that moves anything physical on the airframe. (Apart from Autobrake dial on the MIP)
It's so wierd - TOD is like the last phase of flight where something suddenly goes so completely wrong. The only thing you can do on the MCP (and that's the only thing you actually touch apart from selecting your Autobrake setting on the MIP) at TOD to crash the aircraft is dial in ALT 0 and V/S 8000/FPM. That will get you spat out. But to do that the bloke sitting next to you - checking your work - would have something to say about it. And if it was me - I'd challenge you as to why you'd dialled in those Extreme MCP ALTS and V/S and if you wearn't making sense I'd probably knock you out and have you removed from the cockpit.

It doesn't make sense - it just fell out of the sodding sky. For me that makes it Mech Fail. Something went 'Twang' and it became unrecoverable (with the best will in the World being flown up front) but I have absolutely no idea how or why.

RIP

Spoke to my son this morning (B738 pilot here in Australia) and the consensus amongst his colleagues echoed your sentiments above

I suspect it's chicken and egg speculation now, until the recorders are recovered and read:

How did the crew's actions at TOD contribute to this catastrophic event, or had something failed on the plane just prior to TOD

My thoughts are with the families of those lost


Retired B driver

[ChrisJ800]

My one flight on a chinese domestic airline was just over 25 years ago and it was a Boeing but cant recall the model. What I do recall is at TOD the autopilot was disengaged and close to full spoilers deployed. So it was a loud rough decent for us. Back then the flight crew were straight from the chinese airforrce and their level of English was basic. I am sure things have improved there since then. I am a retired CPL.

[exosphere]

Someone with more video analysis skills than me could provide a rough speed calculation based on the video using the aircraft lenght as scale reference? Surely it won’t be 100% accurate but I think that the Ground Speed reported from FR24 data is far from accurate and is not even close to the TAS experienced in the final moments. With 3000ft/min a 738 can barely keep 300knots indicated. With 30.000fpm there is no way the speed was lower than 600kts especially with so much potential energy from FL300.

edit: if no such speed was ever reached than a recovery attempt should be realistic, and if a recovery was even partially successful that means that the initial upset was probably not as catastrophic as someone might expect.

[deja vu]

My one flight on a chinese domestic airline was just over 25 years ago and it was a Boeing but cant recall the model. What I do recall is at TOD the autopilot was disengaged and close to full spoilers deployed. So it was a loud rough decent for us. Back then the flight crew were straight from the chinese airforrce and their level of English was basic. I am sure things have improved there since then. I am a retired CPL.
Seriously, basic knowledge of China ATC 25 years ago would tell you the crew vey rarely get to make decisions about descent profiles.

[epc]

Registered just to say that there's another video (dashcam) from a different angle which shows the "horizontal component". I can't post it, but search and you shall find.

Going back to lurk mode.

This is the dashcam footage you speak of:

Dashcam Footage

[kyden]

My one flight on a chinese domestic airline was just over 25 years ago and it was a Boeing but cant recall the model. What I do recall is at TOD the autopilot was disengaged and close to full spoilers deployed. So it was a loud rough decent for us. Back then the flight crew were straight from the chinese airforrce and their level of English was basic. I am sure things have improved there since then. I am a retired CPL.

It's interesting you say that as I used to work next to a major runway and have witnessed many takeoffs and landings. It was always the China Eastern planes that came in hot and heavy (as I called it) and were the loudest of all the 737s. We would make a joke...oh it''s another CE landing again...

[Capt Kremin]

The aircraft was in maintenance for two full days days before the crash.

https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/1274x841/china_eastern_maintenance__5e8eece039f00663b83b281349233b72a ff8bade.jpg

[FlightDetent]

I think FR24 has predictive ability in case the actual data is missing. In predictive mode it assumes the plane is flying normally. So we should not rely on the data. ABC News said as much tonight.I have seen that predictive capability many times over when the target A/C gets out of coverage.

That is a feature of the animation onscreen. The raw dataset available for download, which I hope anyone talking above had been using, is just plain record of the collected ADS-B transmissions.

FR24 seem to truncate some of it (sub zero FL readings) but otherwise it is what it is.

-- x --

Not sure if the TOD discussion is relevant, i.e. whether the events unfolded after the descent was instructed by ATC.

[Capt Kremin]

Observation. Take it for what you will: The final three ADSB speed outputs show the groundspeed decreasing; which is not indicated by any noticeable pitchup in the two videos, coupled with an increase in the rate of descent.

Possible speedbrake deployment?

[jeepjeep]

A lot of folks seem to take it as a fact that the aircraft was temporarily recovered, briefly climbing, just before crashing - according to the tracking site. Watching the videos, if they are accurate, this seems highly unlikely though.

Remember, the altitude data from ADS-B / FR24 site is a barometric pressure reading transmitted by the aircraft itself only. Sure, in normal flight, a reduction in barometric pressure correlates with a gain in altitude. But when an aircraft left controlled flight, there are other reasons which could cause a temporary reduction in barometric pressure at the static port - which would falsely be interpreted as a brief climb.

So, what you should take as a fact is: we don't know...

A true pearl of wisdom - always understand the instruments and sampling process behind the data.

[tdracer]

The aircraft was in maintenance for two full days days before the crash.


Back in the late 1990's, I worked 737-3/4/500. We had repeated issues with poor maintenance with Chinese operators - things like throttle cables breaking due to excessive wear less than 100 hours after they were supposedly inspected. When I worked at a car dealership while in college, we called that a 'wall job' - customer brings in the car, it gets parked up against a wall for a few days - customer comes back and picks up the car with a sizable repair bill when no actual work had been done (didn't happen at my dealership, but I knew of dealerships where it did).
I'd rather assumed that sort of thing was a thing of the past as the Chinese market had matured - maybe not...

[Chiefttp]

A runaway trim scenario in which the pilots were surprised would seem unlikely given the 737 manual Trim wheel would have been spinning and clicking away a few inches from each pilot. Hard to not notice that.

[logansi]

The aircraft was in maintenance for two full days days before the crash.

https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/1274x841/china_eastern_maintenance__5e8eece039f00663b83b281349233b72a ff8bade.jpg


Don't take for granted it was in maintenance, China has strict Covid policy at the moment, domestic flying is way down with 60% of flights canceled. Could have just been grounded due to canceled flights.

[43Inches]

Back in the late 1990's, I worked 737-3/4/500. We had repeated issues with poor maintenance with Chinese operators - things like throttle cables breaking due to excessive wear less than 100 hours after they were supposedly inspected.

737 Throttle cable?

[PJ2]

However this began & finished, it wasn’t “throttle cables”.

[B2N2]

What is irritating is how thinly veiled the racism is and how quickly it surfaces on a thread like this.
Contrary to popular belief you don’t need to be able to speak English to fly a jet.
Last time I checked there are 6 official ICAO languages, Chinese being one of them.
Chinese system is different, ATC stands for Air Traffic Control.
This is where you fly, this is your offset, this is where you descent. The pilot operates the airplane and ATC controls the airplane.
Different doesn’t mean it’s wrong or somehow inferior to what “we” do.
So typically Pprune-ish, "well 30 years ago I had this happen or 30 years ago that was the case so it must be the same now blah blah blah"
NO.
That’s exactly what Boeing's response was after not one but two fatal accidents.
’Well it wasn’t a western company so they have done it wrong’.
STOP doing that.

[A-3TWENTY]

A lot of people had posted their opinions of what could have happened.

I flew in China for 10 years, being last flight in 2020. I'm not racist, just pragmatic.

The ATC there is crap. Not only the control itself, but also the attitude from ATC to the to pilots. Chinese pilots accept all kind of stupid requests from the ATC without a word. It is almost impossible a Chinese pilot refuse a stupid ATC instruction. Specially if the crew had a 2700 hrs Cpt.
It is well possible that they had an engine failure , request to descend and got a "stand by" as an answer. And they lost speed until the stall. It really would not surprise me at all.
I really think that China lasted a lot without a fatal accident. They had imminent accidents though out this years.
I remember foreign pilots had years of discussions in the cockpit because Chinese pilots flew at night with their radar off, and worst, with cockpit windows covered with newspapers to avoid radiation. Its happened until the day a wide body China Eastern flew into an isolated CB and lost 10000 ft. And so on. Many, but many stories. If you want to know more download flying upside down.pdf from the Internet.

So I really believe this accident had a partnership between ATC and crew. But.... as everything in China we will never know. BTW , probably the boxes were destroyed, but the communication between the plane and ATC wasn't revealed yet. Probably will never be.

Fortunately for all foreign pilots flying in China , it happened with a local crew.

My condolences to all families involved.

[FullMetalJackass]

A lot of people had posted their opinions of what could have happened.
It is well possible that they had an engine failure , request to descend and got a "stand by" as an answer. And they lost speed until the stall. It really would not surprise me at all.

So I really believe this accident had a partnership between ATC and crew. But.... as everything in China we will never know. BTW , probably the boxes were destroyed, but the communication between the plane and ATC wasn't revealed yet. Probably will never be.



If that were the case, we would be seeing a decrease in ground speed before the start of any descent. As it is, the aircraft appeared to be flying straight and level, then there's 15 seconds where no ADS-B data is available and in that 15 seconds, the aircraft has dropped 50 knots GROUND Speed but had already lost 2000 feet of altitude and was now descending at 21.000fpm. Correct me if I'm wrong, but first reaction to engine failure in cruise on a 737 is disconnect autothrottles, select MCT on the operative engine, perform any recall items and then maintain cruise flight level until reaching single engine drift down speed which can take a couple of minutes.

Here we have 15 seconds between cruising along steadily and suddenly descending rapidly. My initial thoughts were a runaway trim scenario - maybe not the sort which has the trim wheels clanking around - but slow and insidious over a period of minutes which isn't noticed - because the coincidence of an upset happening where they would usually be at TOD is just too much to overlook. So, they set the altitude to, say, FL 100, the AP commanded nose down, but plane was horribly out of trim due some defect. Crew were preoccupied with briefing the approach and before they realised what was happening, they were already in the merde...

[xji]

The ATC there is crap. Not only the control itself, but also the attitude from ATC to the to pilots. Chinese pilots accept all kind of stupid requests from the ATC without a word. It is almost impossible a Chinese pilot refuse a stupid ATC instruction. Specially if the crew had a 2700 hrs Cpt.

It is well possible that they had an engine failure , request to descend and got a "stand by" as an answer. And they lost speed until the stall. It really would not surprise me at all.

So I really believe this accident had a partnership between ATC and crew. But.... as everything in China we will never know. BTW , probably the boxes were destroyed, but the communication between the plane and ATC wasn't revealed yet. Probably will never be.

Fortunately for all foreign pilots flying in China , it happened with a local crew.


The Chinese media are already reporting that they entered the range of Guangzhou ATC at 14:17, started the rapid descent at 14:20 and the ATC repeatedly tried to reach them without any response until the end. Take that however you will.

Also, can’t help but agree that the last part you wrote seems completely unnecessary.

[oblivia]

One of the recorders has been found.

https://www.scmp.com/news/china/politics/article/3171547/china-eastern-airlines-flight-mu5735-black-box-found-plane

[Capt Kremin]

If this was a jet upset and the crew was trying to address the ROD with a standard recovery, I am wondering where the lateral changes in track come into play?

36 seconds after the stable flight path was lost, the aircraft has completed a 40 degree turn to the left.

36 seconds after that is has turned approximately 65 degrees to the right, all the time descending.

This of course is not how you would expect a UA recovery from a deep nose down attitude to be carried out.

Something else is going on here.

[tupungato]

The ATC there is crap. Not only the control itself, but also the attitude from ATC to the to pilots. Chinese pilots accept all kind of stupid requests from the ATC without a word. It is almost impossible a Chinese pilot refuse a stupid ATC instruction. Specially if the crew had a 2700 hrs Cpt.

From press release: "The captain had accumulated 6,709 flight hours total, the first officer 31,769 flight hours, the second officer 556 hours, all of them in good family relations."
So somewhat more than 2700.

[logansi]

From press release: "The captain had accumulated 6,709 flight hours total, the first officer 31,769 flight hours, the second officer 556 hours, all of them in good family relations."
So somewhat more than 2700.


There is some issue in the translation, the 556-hour pilot was the first officer. The first officer listed as having 31,769 hours was a check and training captain, however, in China, they are listed as a F/O on crew manifests.

[oblivia]

“The exterior of the recovered device is quite damaged and frontline investigators are figuring out if it is the flight data recorder or the cockpit voice recorder,” Mao Yanfeng, director of the Civil Aviation Administration of China’s accident investigation unit, told reporters after the black box was found on Wednesday.

https://www.scmp.com/news/china/politics/article/3171547/china-eastern-airlines-flight-mu5735-black-box-found-plane

[MikeSnow]

Running the numbers: The vertical speed three times touched 30,976 feet per minute, which is exactly 600km per hour.[...]It is suspicious that the vertical speed peaked three times at exactly 600kmh (I am suspicious of round numbers).

Actually 30,976 feet per minute is about 566 km/h, not 600 km/h. But you are right to be suspicious about that number, because it's quite close to the maximum vertical speed that can be encoded by ADS-B: 32,640 feet per minute (597 km/hour). So it wouldn't surprise me if that 30,976 fpm value is the maximum that can be reported by this particular type of aircraft due to some additional limitation, and the actual vertical speed probably reached even higher values.

ADS-B encodes vertical speed as a 9 bit integer (there are also two additional bits for direction - up/down - and source - GNSS or barometric), and each increment of that integer represents 64 feet/minute. So there are only 512 possible values for vertical speed, between 0 and 511. And because 0 is regarded as "no data", you have to substract one from that encoded value before multiplying by 64. That gives a maximum of 510 x 64 = 32,640 feet / minute. You can't get more than that encoded in an ADS-B data packet.

[krautland]

Second CAAC press conference today. Key takeaways:

- one black box found, severely damaged
- ATC communications "normal"
- weather not a factor
- Captain 6709h, 1st F/O 31769h (double confirmed), 2nd F/O 556h, all have good family relationships


China changes incredibly fast. I think flight crews who worked there twenty years ago experienced a vastly different place. ATC is an issue as they are military and speak to you in that tone. regulators generally shrug complaints off and ask "why change it when it works?" ... CAAC meanwhile has used a hard enforcement approach to radically change a formerly unsafe aviation market into one that hasn't had a crash like this one in ten years in spite of its massive size. Generally they have adopted an approach of producing excellent investigative material and publicizing it widely in Chinese to get maximum trust from the flying public. They don't care at all about writing anything in english, which I presume is why a lot of folks outside of China haven't noticed their changed practices vs ten years ago.

[MACH6]

Often, the SIMPLEST explanation is the correct one….

A NEAR VERTICAL dive in a B737 can only be caused by SUSTAINED PILOT INPUT.

After the SILKAIR MI 185 disaster in 1997, several scenarios including RUDDER HARDOVER, JET UPSET, ENGINE FAILURE, STALLS, DEPRESSURISATION and SUSTAINED PILOT INPUT were simulated by the human factors group, which were part of the accident investigation team. (see final report).

SUSTAINED PILOT INPUT produced a nearly identical rate of descent and just under 3nm lateral distance travelled.

The other scenarios didn’t get anywhere near the same descent or distance travelled.Also, the aircraft exceeded the local speed of sound, causing the ‘boom’ sounds locals heard in the final stages of descent.

I hope the recorders can be recovered in a usable condition. But like the SilkAir accident, I’m sure they would have been disabled before the dive.

[KAPAC]

Has the tail section been found ?

[agird]

Never attribute to racism that which can be explained by bad practice.
​​​​​​
How do US vs Chinese fatal crashes match up over the last decade?

[fdr]

Looking at the last data points: GS 376kts VS 30976 ft/min = ~305 kts. Decent angle is arctan(305/376) = 39 degrees. <please check my maths!> Based on the video evidence, it suggests that AOD increased markedly in the very last phase of the decent. Maybe up until this point, the A/C was relatively intact but suffered some significant break up close to the ground.

your maths is about right, and the aircraft has a resultant TAS down the flight path of 484 kts, At the lower levels that is an IAS of around 460-475 roughly, which is about 100kts over the Vne of the plane. At very high mach numbers, above the height where a change in the descent occurred to a momentary apparent recovery, the b737 wing reduces lift for a given AOA from the development of strong normal shock on the underside of the wing. a normal shock at high mach is expected, the 737 has a visible shock at around 0.78M, the Classic had one quite observable at at around 0.735. On the top, at speeds over MMo, the shock on the bottom of the wind results in a rapid loss of lift for a given AOA, which results in a decaying flight path, or a pretty hefty increase in AOA needed to maintain level flight.

Adam Air DHI 574, and Silk Air reached speeds higher than this aircraft, but both of those had very odd reasons for the upset. Adam Air was not far removed from Air Asias bad day out for causation. The usual testing limit for Mdive is around 0.06M above the proposed MMo, roughly. The B737 is not much fun at taht but it will do it, but 100kts over Vmo is a tall ask for the aircraft. The increased AOA needed to effect a recovery results in very high buffet and that is one of the items that impacts flutter boundaries.

The simulators that are certified for flight training do not properly represent the aircraft at speeds well in excess of Vmo/MMo, they give a sense of comfort that the MACH/CL, and MACH CM data does not support, the trim change is observable in the MMo-Md dive data. Back in the dark ages this was described as Mach tuck, and the explanation out of the AP3456A was related to the shock foot movement rearwards.... yes, that does occur, but the tuck comes from the development of the shock on the bottom of the wing, and that has a very abrupt loss of CL for the trimmed AOA, and that results in a stunning Cm change. The above just suggests that getting nose low in a jet transport goes bad pretty quickly, and the simulator does not have great fidelity for training in that area. For the occasions that I did tests out beyond MMo to Md the recovery was of enough concern that the flights were planned to have a high thrust level in the descent, so that if the tuck was excessive, a speed reduction from reducing thrust could be made. Some planes are just beautiful, like the Falcon, it is impeccable to very high speeds, with full authority without buffet. The B737 Classic has buffet that was odd given the rule, and the NG has a normal envelope that essentially alters to achieve compliance of the rule, through the little orange line that starts to drop down below the MMo indication, same for a few others, and that gives the compliance to the rule, albeit at a mach a little lower than the nominal MMo. In upsets, where the ATR is engaged, the thrust comes back rapidly to idle. If that hasnt occurred, then more has happened than can be explained by a simple upset. That info resides in the engine EEC memory chips, which have some possibility of having survived. The CVR and DFDR of this aircraft probably survived the average deceleration but any heavy structure that impacts them in the deceleration would have way above the 3400g test levels. The average deceleration would be around 2000-2100g, its about 50/50 the FDR or CVR will have taken higher impact loads.

All in all, would be surprised that the plane in this case was the trigger of the event, and an upset can occur without substantial crew error, or any action by the crew. An upset in severe weather can put the plane into a position that care is needed. The odd thing is that the most significant factor in the recovery of a high speed jet upset is the detection-recognition time of the crew before an effective recovery action is commenced. The only exception that comes to mind on that is the stunning survival of the B747 of CAL on its way to the USA that held together well beyond where it should have failed, it was pretty daggy by teh time it got to California, but it didn't splash down.

[krautland]

​​​​​​
How do US vs Chinese fatal crashes match up over the last decade?

10 years without a fatal incident in China. There were two fatalities in the same period in the US.

https://news.cgtn.com/news/2022-02-26/China-sets-safe-flight-world-record-of-100-million-continuous-hours-17XDwhGIPra/index.html

https://www.airlines.org/dataset/safety-record-of-u-s-air-carriers/

China and the US are very close in number of system seats. China briefly was ranked first during Covid but that has since changed in favor of the US again.
Change could be temporary though as China is building a ton of new mega airports and is set to add 8,000 new 100+ seat aircraft in the next 20 years.

https://centreforaviation.com/analysis/reports/china-becomes-the-largest-aviation-market-in-the-world-521779

[fdr]

Often, the SIMPLEST explanation is the correct one….

A NEAR VERTICAL dive in a B737 can only be caused by SUSTAINED PILOT INPUT.

After the SILKAIR MI 185 disaster in 1997, several scenarios including RUDDER HARDOVER, JET UPSET, ENGINE FAILURE, STALLS, DEPRESSURISATION and SUSTAINED PILOT INPUT were simulated by the human factors group, which were part of the accident investigation team. (see final report).

SUSTAINED PILOT INPUT produced a nearly identical rate of descent and just under 3nm lateral distance travelled.

The other scenarios didn’t get anywhere near the same descent or distance travelled.Also, the aircraft exceeded the local speed of sound, causing the ‘boom’ sounds locals heard in the final stages of descent.

I hope the recorders can be recovered in a usable condition. But like the SilkAir accident, I’m sure they would have been disabled before the dive.

That is true for the MI185 case, the flight path was very well defined and it was difficult to replicate it. Other steep descents in the 30-50 degree range have occurred for other causes, the trim runaway being a low likelihood cause (except when someone does something pretty dumb with a system architecture unwittingly).

The data gives enough information to exclude most stalls as a cause, and a number of items can give a roll excursion that will drop the nose to below 30 degrees nose down in short order. The contenders for that sort of thing is a simple TS entry and disorientation, a slat element extension at cruise, a TR deployment, a revisit of the yaw damper/rudder reversal issue etc. Most of these are not likely but they get to the same point in time and space without being MI185 or EGYPT 990, or really odd events like Adam Air 574.

[fdr]

​​​​​
If it is not in China it doesn't count ? ...

Flash airline flight 604, malfunction lead to autopilot disconnected and pilot not controling their aircraft, that it is low altitude doesn't change anything, high altitude make it even more easier to loose control.

Adam air flight 574 ... High altitude lost of control after autopilot disconnectedhttps://en.m.wikipedia.org/wiki/Flash_Airlines_Flight_604

The descent rate varied during the fatal dive, with a maximum recorded value of 53,760 feet per minute,
From memory, I believe that the descent profile of the Adam air is quit similar of the one seems to be seen here.

I also remember a pilot suicide, with the pilot banking the plane high altitude and also same very fast descent from high FL to ground in few minutes, forgot which plane thought. Not saying it what happened there, but descent profile would also fit.

Flash 604 had some other controversial system possibilities raised that were discounted yet had occurred to the type previously, and in fact was photographed in a SAF B737 which got the crews attention. 574, the autopilot disconnection wasn't the basic problem, the turning off of reference systems for the APLT and the ADIs of the crew pretty much made that a most unfortunate event.

[waltair]

I
Something went 'Twang' and it became unrecoverable (with the best will in the World being flown up front) but I have absolutely no idea how or why.

RIP

Maybe. Or maybe not. I teach people to fly these things. Done simulator with the China Eastern guys, this aircraft. Nice guys, I like them.

It would not surprise me at all if the report says they just kept doing “X“ until the plane crashed; never figured out what was going on. Human beings are fragile things. I would trust the machine over the man. I have seen people lock right up. And the other one just sits there. Totally possible. It is just how we are, we are fallible.

[FlightDetent]

484 TAS is closer to 440 CAS.

G-EZJK made it to 429 and already the AAIB bulletin noted the crew's actions on the yoke alone would not have stopped the descent.

[RatherBeFlying]

I have seen people lock right up. And the other one just sits there. Totally possible. It is just how we are, we are fallible.Was right seat in a Viscount simulator (white on black AH) when the left seat got it upside down at 16,000 and just sat there with me screaming in his ear we were upside down until we hit the ground.

Would be a good simulator scenario to have in the curriculum, but don't prebrief the guy expected to take over.

[ATC Watcher]

@ Krautland : ATC is an issue as they are military and speak to you in that tone.
That was a long time ago, they are civil now. The problem still is that the airspace around the civil routes is mostly military airspace and cannot be penetrated, even for weather.

[Doug Stark]

Lets not get sanctimonious on our reporting and safety...after all it was the chinese who first grounded the Max.... and if not for them I would bet the FAA wouldn't have, ...

I have to disagree here. It was an ex NASA astronaut, the Minister of Transport for Canada that called the FAA to tell them that his experts had reviewed the data from both Max 8 crashes and had recommended (and accepted) to the PM that the Max be grounded in Canada. At the time, Trump viewed the Chinese grounding (1st group to do so) as 'political' and anti American. It was the final straw when Transport Canada ordered the grounding.

Check the Washington Post article dated 2019/03/13/

[Siu Mo To]

A lot of people had posted their opinions of what could have happened.

I flew in China for 10 years, being last flight in 2020. I'm not racist, just pragmatic.

The ATC there is crap. Not only the control itself, but also the attitude from ATC to the to pilots. Chinese pilots accept all kind of stupid requests from the ATC without a word. It is almost impossible a Chinese pilot refuse a stupid ATC instruction. Specially if the crew had a 2700 hrs Cpt.
It is well possible that they had an engine failure , request to descend and got a "stand by" as an answer. And they lost speed until the stall. It really would not surprise me at all.
I really think that China lasted a lot without a fatal accident. They had imminent accidents though out this years.
I remember foreign pilots had years of discussions in the cockpit because Chinese pilots flew at night with their radar off, and worst, with cockpit windows covered with newspapers to avoid radiation. Its happened until the day a wide body China Eastern flew into an isolated CB and lost 10000 ft. And so on. Many, but many stories. If you want to know more download flying upside down.pdf from the Internet.

So I really believe this accident had a partnership between ATC and crew. But.... as everything in China we will never know. BTW , probably the boxes were destroyed, but the communication between the plane and ATC wasn't revealed yet. Probably will never be.

Fortunately for all foreign pilots flying in China , it happened with a local crew.

My condolences to all families involved.


[QUOTE=A-3TWENTY;11204388]A lot of people had posted their opinions of what could have happened.


I flew in China the last 15 years and I still fly into China. I don't know if I should call it racist but I sense a lot of expats here seem to have the superiority complex.
Admittedly I have not operated with a mainland Chinese in the seat but I had a few in the jumpseat as "navigator" into non open airports. They seem reasonable when we had discussion about work.
I agree ATC is crap but it is not true to say the locals comply without a word. I can speak the language so I understand everything on the frequency. Often I heard pilots argued with ATC and some got very fiesty. And so you think a 2700 hrs captain from elsewhere will always speak up??? So there are no near mishaps in other parts of the world?? I do not agree with the punitive culture but it has been 10 years without a fatality. It is quite scary if you look at the safety stats of a large European/"Asian" airline but nobody talks about them even when they had a crash. When there is any incident Chinese related everybody jumped on it. When something happened and a local pilot saved the day nobody talks about it.
Having worked in a few companies with diverse workforce and also as a checker, I have seen people with substandard performance from every continet; so is good performance.

[swh]

CVR was found yesterday, the base of the unit had significate damage, the cylindrical memory unit which contains the data has the appearance of being in good condition was sent to Beijing last night. The NTSB has also been formally invited to participate in the investigation. https://www.reuters.com/article/china-crash-transportation/u-s-says-china-invites-ntsb-to-participate-in-boeing-crash-probe-idINL2N2VQ1HO?edition-redirect=in

https://cimg7.ibsrv.net/gimg/pprune.org-vbulletin/690x518/bf30cc2931d8af5fc1f7aed148af36e2_337c71aa5c426bd36b4fb70916e 14fc471c82204.png
Source: Aviation Accident Investigation Center of Civil Aviation Administration

https://youtu.be/rg41I1xGupY

[Auxtank]

Maybe. Or maybe not. I teach people to fly these things. Done simulator with the China Eastern guys, this aircraft. Nice guys, I like them.

It would not surprise me at all if the report says they just kept doing “X“ until the plane crashed; never figured out what was going on. Human beings are fragile things. I would trust the machine over the man. I have seen people lock right up. And the other one just sits there. Totally possible. It is just how we are, we are fallible.

They are indeed. But this is when the training should kick in hard and achieve;

Establish who has Controls. State it,
Memory Items,
Inputs to attempt to establish Straight And Level,
QRH whilst the other is PIC.
Work QRH Items for stated Outcomes.


I think they were doing more than just sitting there. I think they were very very busy. I think it's far easier to "Lose it and Lock Up"' in the sim (knowing it's only your job that's over and not your life) - a relatively consequence-free environment than when you're actually there in the air.

Sim work - it's hard to say - there are differences in the state of the mind - in some ways you're harder focused in the sim than real World and in other ways you're softer focused. What you cannot do in the sim is convince someone they're about to die if they get it wrong.
Knowing you're going to die will mean you will do ANYTHING you can to avoid that.
Looking at the somewhat spurious data so far - it looks very likely that the pilots were severely deprived of flight controls from on or soon after the initial upset occurred all the way to the impact on the ground. That would suggest a loss of one or more control surfaces.

[DaveReidUK]

I also agree with a post that highlighted the two ADSB blips where there is an extended gap between responses of say 15 seconds, where both steep descents seem to originate, was there some sort of electrical fault or factor? From both ADSB cutouts the aircraft initiates a steep descent and lurches left, from what the plot shows.

A simpler, and more likely, explanation for ADS-B blips would be that there weren't any - the aircraft could well have continued to transmit normally, but for some reason those transmissions weren't picked up by FR24's crowd-sourced receivers, possibly due to an unusual aircraft attitude where the transponder antenna was blanked.

[Ngineer]

Unfortunately we are living in a COVID world where there are a lot of rusty people in the aviation industry. I have seen many maintenance errors as a result, and have been expecting to see many more. It would not surprise me if this was somehow related to an error. There are a lot of mechanisms in place to get Flt crew back up to standard after considerable time not flying, but in the maintenance field it is very different. And when workplaces are restructured to save costs during this mess, things are more likely to go wrong.

One example of how things can go wrong from a simple error. An aircraft is on the ground for an extended layover and all drains, static ports & pitot probes are covered up (etc, etc). All covers are removed at the return to service, however the pitot covers on the vertical stab are missed. It does not get picked up on the walk around. Aircraft goes flying and everything seems fine until the pilot disconnects the autopilot and tries to fly it manually with high airspeed. The elevator feel is subsequently compromised and the elevator controls are over sensitive.

In no way am I suggesting this as a cause, just an example of the unexpected. I have personally seen aircraft go flying with gear pins left in, drain covers still fitted, and maintenance paperwork not completed. The Aviation industry is different to what it was 2 years ago. Everyone needs to take an extra minute to double check what they, and others, have or have not done.

[nonsense]

I have to disagree here. It was an ex NASA astronaut, the Minister of Transport for Canada that called the FAA to tell them that his experts had reviewed the data from both Max 8 crashes and had recommended (and accepted) to the PM that the Max be grounded in Canada. At the time, Trump viewed the Chinese grounding (1st group to do so) as 'political' and anti American. It was the final straw when Transport Canada ordered the grounding.

Check the Washington Post article dated 2019/03/13/
https://www.washingtonpost.com/local/trafficandcommuting/canada-grounds-boeing-737-max-8-leaving-us-as-last-major-user-of-plane/2019/03/13/25ac2414-459d-11e9-90f0-0ccfeec87a61_story.html

[43Inches]

As many who have worked with or associated with Chinese aviation over the last 30 years would know the countries attitude to aviation is indeed changing to one of trying to maintain reasonable standards. This also involved change of attitudes towards the ex military pilots who were unsuited to airline style work and move to more western style management of training/checking processes for civil aviation. As with many other areas in China the industry is very punitive if you mess up, you don't get many chances if you stuff up, but that's not just China. Considering the challenging flying in China, with mountainous terrain and terrible weather and smog conditions they do a pretty good job, considering the amount of flying done these days. If you try and pin some cultural BS on their pilots it would just be from a prejudice mind.

[Ziaii]

Unfortunately we are living in a COVID world where there are a lot of rusty people in the aviation industry. I have seen many maintenance errors as a result, and have been expecting to see many more. It would not surprise me if this was somehow related to an error. There are a lot of mechanisms in place to get Flt crew back up to standard after considerable time not flying, but in the maintenance field it is very different. And when workplaces are restructured to save costs during this mess, things are more likely to go wrong.

One example of how things can go wrong from a simple error. An aircraft is on the ground for an extended layover and all drains, static ports & pitot probes are covered up (etc, etc). All covers are removed at the return to service, however the pitot covers on the vertical stab are missed. It does not get picked up on the walk around. Aircraft goes flying and everything seems fine until the pilot disconnects the autopilot and tries to fly it manually with high airspeed. The elevator feel is subsequently compromised and the elevator controls are over sensitive.

In no way am I suggesting this as a cause, just an example of the unexpected. I have personally seen aircraft go flying with gear pins left in, drain covers still fitted, and maintenance paperwork not completed. The Aviation industry is different to what it was 2 years ago. Everyone needs to take an extra minute to double check what they, and others, have or have not done.
Thank you for bringing this up.
Yes, investigation should include records of maintenance performed in this CoViD era.
And check all possible tasks that may have been missed (or exceeded if time-controlled).

[Vhammer]

Fortunately the throttles and flight controls are not interlinked.
With over 10K hours on the 737 including the 800 and Max, and some training in accident investigation, I'd like to offer a few observations.
First off, I don't believe it is possible to reach the ground in two minutes without the throttles pushed up. No one keeps power in, in a dive. Its instinctive for anyone that's been flying for any period of time to reduce power to idle.
Now with power at idle I don't think even vertical you can descend 29K feet in two minutes.
Now to get vertical, you would have to have a condition where not only are the flight controls unresponsive but they have had to go into a full nose down position by themselves, and be resisting input to reduce the angle of descent, which without some kind of assistance would not normally occur on their own.
OR you would have have to a failure of the flight control system as well.
So we are talking two separate events, by systems not related, except by the person flying.
I could be grossly mistaken, but I don't believe you will find much data coming out of China that isn't manufactured. The airplane has been in service 7 years, so bugs have been worked out. This leaves one of several possibilities.
Crew action, maintenance or some external factor.

[CodyBlade]

Mi 185 had the throttle fire walled.Asian report says it part of escape/recovery action.

[Turkey Brain]

@ Krautland :
That was a long time ago, they are civil now. The problem still is that the airspace around the civil routes is mostly military airspace and cannot be penetrated, even for weather.

A point on safety and weather avoidance, in any country.

The military have never stopped me deviating for weather in China. When ATC can’t approve your weather deviation request.

” Pan Pan, Pan Pan, Pan Pan, avoiding weather, will fly offset 30 nm miles right “

Incredibly my colleagues have said “ oh they won’t like that ! “

do I really care ?

My priority is the safety of my customers and colleagues, not the controller’s feelings who
maybe has their hands tied, with many rules.

[esreverlluf]

Fortunately the throttles and flight controls are not interlinked.. With over 10K hours on the 737 including the 8oo and Max, and some training in accident investigation, I'd like to offer a few observations. First off, I dont believe it is possible to reach the ground in two minutes without the throttles pushed up. No one keeps power in , in a dive. Its instinctive for anyone thats been flying for any period of time to reduce power to idle. Now with power at idle I dont think even vertical you can descend 29K feet in two minutes. Now to get vertical, you would have to have a condition where not only are the flight controls unresponsive but they have had to go into a full nose down position by themselves, and be resisting input to reduce the angle of descent. which without some kind of assistance would not normally occur on their own. OR you would have have to a failure of the flight control system as well. So we are talking two separate events, by systems not related. except by the person flying. I could be grossly mistaken, but I dont believe you will find much data coming out of China that isn't manufactured. The airplane has been in service 7 years, so bugs have been worked out. This leaves one of several possibilites. Crew action, maintenance or some external factor.

29000 feet in two minutes is only about 150kts - I would have thought that would be easily achievable in a vertical dive with power off . . .

[Australopithecus]

Fortunately the throttles and flight controls are not interlinked.. With over 10K hours on the 737 including the 8oo and Max, and some training in accident investigation, I'd like to offer a few observations. First off, I dont believe it is possible to reach the ground in two minutes without the throttles pushed up. No one keeps power in , in a dive. Its instinctive for anyone thats been flying for any period of time to reduce power to idle. Now with power at idle I dont think even vertical you can descend 29K feet in two minutes. Now to get vertical, you would have to have a condition where not only are the flight controls unresponsive but they have had to go into a full nose down position by themselves, and be resisting input to reduce the angle of descent. which without some kind of assistance would not normally occur on their own. OR you would have have to a failure of the flight control system as well. So we are talking two separate events, by systems not related. except by the person flying. I could be grossly mistaken, but I dont believe you will find much data coming out of China that isn't manufactured. The airplane has been in service 7 years, so bugs have been worked out. This leaves one of several possibilites. Crew action, maintenance or some external factor.

Seriously, you need to think about that. We can maintain 310 kts in a normal descent with engines at idle. With a vertical flight path the aircraft will keep accelerating at 9.8m2 until it reaches its terminal velocity, somewhere near Mach 1. Re-read FDR's post earlier. He's an actual test pilot, and he explains what happens when in the transonic regions just above the normal envelope

An aircraft seven years old isn’t one that has the bugs worked out. Its one, especially if barely used in two years, that will develop the
usual litany of defects and rectifications.

27 years all variants 737 on four continents.

[common toad]

29000 feet in two minutes is only about 150kts - I would have thought that would be easily achievable in a vertical dive with power off . .

When was the last time you saw a ROD of 14,500 fpm?

[Turkey Brain]

There is a common misconception on this and other threads relating to max achievable rates of descent.

An excellent post by ‘ fdr’ explained in some detail about the aerodynamic effects of subsonic airliners exceeding their certified Mach No.

I think that post or a previous post also explained that flight simulators are not programmed to accurately simulate these situations outside the normal certified flight envelope.

If you inadvertently roll more than 90 degrees of bank in the cruise, and stay in trimmed flight there is no lift up, it’s sideways. If you manage to roll near to inverted, then all the lift of the wing will be towards the ground.

As the speed builds up rapidly, the lift also increases rapidly, accelerating you down.

If you happen to notice the unusual attitude you unload the wings and roll to the nearest horizon, and begin a smooth pullout.

If you’re still distracted, planes will normally enter a spiral descent, but if fully inverted (180 degrees of bank ) you basically start flying the second half of a loop. Without any pilot input, just from the trimmed state of the aircraft.

In these situations the engine thrust is almost irrelevant, full thrust is nowhere near the weight of the aircraft. In the cruise at altitude full thrust is maybe just above 1/20 of the aircraft weight. Airliners have a lift drag ratio of maybe 1/20. Maybe a bit better with more modern aircraft.

But you get the idea, the weight of the aircraft is significantly more than thrust from the engines.

As the plane approaches high transonic speeds , approaching Mach 1.0 you get a dramatic drag build up, Critical Mach drag rise, or whatever you wish to call it.

Airliners are bluff objects designed to fly subsonically, so this extreme drag makes going supersonic very difficult.
So generally the max rate of descent will be about Mach 1.0

As an aside, using the FlightRadar24 altitude readouts, the rate of descent corresponds to about a 1,000 ft a second. 5,000 ft lost in 5 seconds if I read the numbers correctly. Or 60,000 ft a min or 685 mph. Local speed of sound is 707 mph assuming a standard atmosphere and a temperature of -25 C.

So vertical speed M 0.97 , this is only the vertical speed using the data. As stated by previous posts the data from FR24 can be smoothed or assumed. When you allow for the horizontal ground speed to get the true airspeed and Mach No. the numbers are higher.

With previous Jet upsets when the data is pulled and all the circumstances are allowed for, the max speeds always seem to be subsonic, or mildly supersonic.

As ‘ fdr ‘ stated as you descend into thicker air it is also warmer, which means the local speed of sound increases too. So for a given speed, the aeroplanes Mach No will decrease. As you descend into warmer air you should get more control.

There are two big issues with these high speed descents.

1:you can rapidly exceed the aircrafts design max speed which can lead to structural failure.

2: you need a lot of sky to pull out of a high speed descent.

Lastly, I have read that most ‘ Jet upsets ‘ that occur in visual conditions are survived, but those in cloud or at night with a limited visual reference are not.

From my aged memory the CAL 747 that had a ‘ jet upset ‘ was only flown correctly when the crew got a visual horizon at about 20,000 ft. I note that for this unfortunate flight, the cloud base was much lower.

P.S. My credentials; I can’t spell but have flown commercially for far too long.

[43Inches]

With over 10K hours on the 737 including the 8oo and Max, and some training in accident investigation, I'd like to offer a few observations. First off, I dont believe it is possible to reach the ground in two minutes without the throttles pushed up.

Amazing in 10k hours you managed to find throttles on the 737... Where are these people coming from that don't even know basic cockpit terminology yet claim to have vast experience on type. Most airliners will reach 3000-4000 fpm descent with no power with less than 10 deg nose down, put the thing into a 40 deg nose down flight path (which the radar plots indicate happened here ref post #52) with power (or not) and you will find that rate of descent gets pretty high. Agreed to achieve -40 deg net flight path the nose must have been lower than that again, unless bits had fallen off. Pretty sure in just about any aircraft you could push the nose down to 45 deg and it will keep accelerating past break up speeds unless you have dive brakes or a parachute. If breakup speed is past mach 1 then it will do that. Remembering that with these subsonic machines as the aircraft approaches mach 1 the tendency is for the aircraft to pitch down further, hence mach trimmers.

[FWRWATPLX2]

So, I served as a Captain flying Boeing 747-400, 747-300, 747-200, 737-800 and 737-700, a former lowly US Army helicopter pilot - No Cat Shots. I have landed on ships, but in helicopters (at night). Army-trained Aviation Maintenance Officer and Maintenance Test Pilot, Aircraft Mechanic License, published and paid international Aviation-safety writer, since 1983. At one time I held Airline Transport Pilot License from seven countries, including a Chinese ATPL. The day I sat the CAAC (Chinese ATPL) written examination, I was the only foreign captain in the room to pass and many Chinese pilots including former PLA failed the exam, too. It was still partially written in Chinese. Long retired after 36 years flying professionally.

I was a Contract Captain in China nearly five years. I was the first white boy contracted and the first foreign captain to sign a contract with the airline that merged with China Eastern Airlines. There was a long period of time, maybe as long as a year, I was the only foreign Captain at the airline. I actually flew China Eastern Airlines Boeing 737-800 aircraft, as a Captain. I feel damned upset that I may have known some of the flight and cabin crew. I have not asked. I would not. I almost prefer not knowing.

That said, to all of the above: Without the Flight Data Recorder recovered and analyzed, without the Cockpit Voice Recorder (now recovered and) analyzed, without ACARS QAR Data analyzed, by the CAAC and Boeing and hopefully NTSB, HOW THE HELL CAN ANY OF YOU ASSUME TO KNOW OR GUESS WHAT HAPPENED?!

If you are airline pilots or retired from the airline game, it is damned unprofessional to weigh in what you think might have happened. It contributes nothing to the Final Accident Report.

I will not be sharing anything on this forum, regarding the accident, other than the aforementioned and, rest assured Boeing manufactures great airplanes, designed to be flown well by very average pilots. I was one of them.

[FullMetalJackass]

That said, to all of the above: Without the Flight Data Recorder recovered and analyzed, without the Cockpit Voice Recorder (now recovered and) analyzed, without ACARS QAR Data analyzed, by the CAAC and Boeing and hopefully NTSB, HOW THE HELL CAN ANY OF YOU ASSUME TO KNOW OR GUESS WHAT HAPPENED?!



Nice rant. Now, back on Planet Earth, what does the R in PPRuNe stand for?

Bonus point if you answered谣言

So why do people indulge in rumour and speculation? In my case it's because I want to learn from the mishaps of others, to hopefully avoid making those same mistakes. Who was it who said:

You must learn from the mistakes of others, because you won't live long enough to make them all yourself?

[Flyhighfirst]

I think you will find that gravity alone would take around 44 seconds

It will be very easy to tell if info released is being held back. As Boeing and the NTSB have a right to access the recorders as well. So either they are granted access and will have to be forthright in their reporting or they deny access and everyone knows it’s a whitewash.

I think there is a better than even chance they will play it by the book.

[paxnerd]

"On Thursday, rescuers said they had found engine components, part of a wing and other “important debris” as they searched the mountainside in a rural part of the Guangxi region for a fourth day. A four-foot-long piece of debris suspected to be from the plane was found more than six miles from the main crash site, said Zheng Xi, the commander in chief of the Guangxi Fire Rescue Corps. As a result, search teams will widen the area they are combing, he added. At the main crash site, a state broadcaster showed the workers digging with shovels around a large piece of wreckage that the reporter described as a wing, which bore part of the China Eastern logo and was perched on a steep, barren slope fringed by dense thickets of now-flattened bamboo."
From the New York Times: debris recovered some distance from the main crash site.

[sopwithnz]

Reuters just now : Debris from the jetliner including engine blades, horizontal tail stabilisers and other wing remnants was concentrated within 30 metres of the main impact point, which was 20 metres deep.

********One 1.3 metre-long fragment suspected to be from the plane was found about 10 km away, prompting a significant expansion of the search area, officials told a news briefing. ********************

Also reporting data accessible on CVR ... https://www.reuters.com/world/china/chinese-search-second-black-box-crashed-jet-2022-03-24/

[B2N2]

The first CCTV video shows a vertical descent due to camera angle, the dashcam footage shows a steep descent but not vertical.
Its difficult to see if the aircraft is right side up or inverted.
One thing I want to emphasize here, it is entirely possible to regain control after an upset and still be in an unrecoverable situation due to lack of altitude.
As in the airplane is under positive pilot control and still crashes.
Simulator upset training will show you how little time you have before the situation becomes unrecoverable either because the airplane is so far out of the envelope that it will come apart during the recovery or insufficient altitude.
This is obviously a PC simulation freeze frame but it’s the best picture to illustrate a possible scenario. Airplane ends up inverted and nose down. “Pulling through” as if flying a part loop will over stress the airframe and take a tremendous amount of altitude. Rolling upright and pulling out of the dive will overstress the airplane and run out of altitude.

https://cimg8.ibsrv.net/gimg/pprune.org-vbulletin/1280x720/image_00ac9e72ce280823f3d2b1a30a11ba05118f039f.jpeg

The question that remains is what got them there?

[45989]

Did this in the sim as an experiment (800) 15 sec Above 250kts unrecoverable

[rigpiggy]

Past cases of such occurences tend to show otherwise. Neither the B-52 which lost 3/4 of its VS nor AA587 nosed over. Problem with lost VS is loss of directional control in Yaw.
Massive nose overs have occured in the past (in Military and General Aviation) as a consequence of losing Horizontal stabilizers. If the FR24 is valid this could potentially happen due to exceeding the structural limit in the first apparent recovery (if the FR24 traces are correct). That said in one of the videos the final trajectory rather looks like 50° ND and possibly with a slight recovery path. The other video on the other hand looks pretty vertical. Simply not possible to safely conclude from the few bits we have. First important information bit to obtain woould be the four corners. After that there is a first chance to get a somewhat clearer picture.

most times loss of horizontal stabilizer ends very quickly with wings breaking off due rapid rotation download (negative g)loading the wing.

[Capn Bloggs]

Did this in the sim as an experiment (800) 15 sec Above 250kts unrecoverable
Could you explain how you did this? What was the trim set at? Was it a trim runaway? Did you set full nose-down trim then try to manually wind it back? Did you deliberately hold the nose down?

[fdr]

most times loss of horizontal stabilizer ends very quickly with wings breaking off due rapid rotation download (negative g)loading the wing.

as happened with Lauda 001

[Daverave83]

If it's a case is was a runaway trim even at extreme you could still get control of the Aircraft. the problem arises that there are 2 ways to do this which is ease the throttle so there's less friction on the elevation controls which they call the "roller coaster" so that you can manually adjust the trim Or increase airspeed to it's maximum threshold this of course makes it more difficult and normally a 2 man job to adjust the trim.

I think this is reason we see them try and gain control at 8000 and a increase in airspeed. Didn't the flight bank to the left?Recovery from a Severe Out of TrimAccelerate or decelerate the airplane to an in-trim airspeed. If a recovery must be initiated from an extreme nose-down out-of-trim requiring a high pull force, an increase in airspeed may relieve enough of the elevator load and control displacement to permit manual trimming. Do not exceed speeed limitation. If a recovery must be initiated from an extreme nose-up out-of-trim requiring a high push force, a decrease in airspeed may relieve enough of the elevator load and control displacement to permit manual trimming. It should be noted that the relationship between airspeed change and trim change do not remain constant. As airspeed is increased, trim change requirements decrease.

In an extreme nose-up out-of-trim condition, requiring almost full forward column, decellerate, extend the flaps and/or reduce thrust to a minimum practical setting consistent with flight conditions until elevator control is established. Do not decrease airspeed below the minimum manouvring speed for the flap configuration. A bank of 30 degrees or more will relieve some force on the control column. This, combined with flap extension and reduced speed, should permit easier manual trimming.

[Capn Bloggs]

Airplane ends up inverted and nose down. “Pulling through” as if flying a part loop will over stress the airframe and take a tremendous amount of altitude. Rolling upright and pulling out of the dive will overstress the airplane and run out of altitude.
Not if you don't pull too hard. And neither will, in every case, cause you to run out of altitude (as appears to be the case here, if indeed the leveloff was deliberate). Besides, why are you rolling upright if you're vertical?

This gives us a terminal velocity of 170 m/s or 330 knots.
Are you serious? A Cessna 172?

As for your comment You are exaggerating the 4-5 times, 43Inches gave you 5000fpm for an Emergency Descent (which in my experience is about right). You're stating the terminal velocity of a C172 is 330kts. That could be in no other condition except straight down. That's 33,000fpm (and would be much more in a 737). That is MORE than 43Inches "4-5 times".

I doubt your username. :suspect:

[A0283]

Very preliminary impression ...

My impression was that Chinese officials declared that parts of the horizontal stabiliser where found at the main crash site. And suggest a 30m diameter main impact zone.

The CVR was found with the 'box' flattened and the memory 'can' scraped but apparently intact. Not indicated where this was found.

Video of the main crash site show a fragmented plane with fragments of metal and composite (with honeycomb) structure overloaded and tubing/lines bent.
One engine was visible in a pit next to a pool of water (the area is very muddy now and more rain is expected - tough job for SAR, my respects - looks they need bamboo matting to get around in some places). The heavy rain appears to have started after the impact.
A bit above the direct impact zone there is a single (right hand) winglet and the trees in that area show a scythe like cut.
Some trees there appear to be about 35cm thick others leg or arm thick.
In the vicinity of the winglet lies what seems part of the top panel of the center section of the aircraft, which sits above the 2nd and 3rd window in front of the forward escape hatch.
A wing panel of a few metres long lies to a side (not sure yet if it was a top or bot panel), with Z-type stringers on one side, which is split spanwise through the lettering and along the edge of the covers.

It looks like the impact was perpendicular to a kind of gulley which has a walking path to at least one side. If true this makes the SAR job even harder. And might explain the landslide risk the Chinese authorities were referring to.

Debris was found a few miles away, no confirmation yet if that belonged to the plane.

So, at max two corners have been found and it seems like the nose section must be dug out.

It seems that the impact was not vertical but under more of a final angle than would be expected from the videos. With the dashcam video looking more representative.

[fdr]

One thing I want to emphasize here, it is entirely possible to regain control after an upset and still be in an unrecoverable situation due to lack of altitude.
As in the airplane is under positive pilot control and still crashes.
Simulator upset training will show you how little time you have before the situation becomes unrecoverable either because the airplane is so far out of the envelope that it will come apart during the recovery or insufficient altitude.

The question that remains is what got them there?

Prior to doing Mdive testing I ran LED and DES simulations using STAR CCM+ of high-resolution 3-D BAC447 series of sections and variants, and found that the Cl collapses at extreme mach numbers, well above MMo. That was also associated with a very large shift in the Cm. The wing works fine within the design envelope. Any extended time in an extreme nose low atitude is going to compromise the ability to generate adequate aoa to get a good recovery pitch rate going. This isn't grandads pitch problems in his P-38 or Spitfire IX, its not even the P-80's discomfort at high speed, and it isn't reflected in the QTG if you go play in the B737 sim. This isn't specific to the B737, it is just one of those things, doing supersonic aerobatics is bad enough if you can pull 9 G if you start from M0.8 vertical downwards.

[ before discounting the loss of g capability at high speed ask any phabulous phantom driver what the g available was supersonic, or how much real estate gets used up with a supersonic dive from 45K, due to the limited g available to pull out in such a case. And that is a wing that arguably was designed for high-speed flight and dogfighting. Some may unkindly argue that the Phantoms wings were only used to have a place to hang MERs and fuel tanks].

The speed buildup just from gravity is ~20 kts/sec at -90 FPA, at 45, is around. 15 knots/sec, without the engine thrust, which adds about another 4kts a sec in a vertical dive. Drag increase is a fair bit but is still low order, the B737 total drag at M0.8 at average weighs is around 5,000-7,000 lbs roughly, it isn't a large amount, compared to acceleration available from gravity. Most speed brakes reduce lift, and that increases the aoa that has to be set to get adequate g loading, and that increases buffet and shock effects. Now this is not what the FAA espouses on aerodynamics, but then the FAA still demands we teach Bernoulli's principle for lift which just ain't so. Move your hand across the sink full of water and soapy bubbles, and you will find that the circulation theory/ bound vortex is visible, including the start vortex, the bound vortex and a stop vortex. What you won't find is what we are supposed to teach pilots about how their plane actually flies, which while simple to explain is fundamentally wrong, and gets wrongerer the more that compressibility comes into play.

Mods; remove or not this post, it is your choice. It is factually correct, and the insistence of our industry to put it's head in the sand means we are bound to repeat the same mistakes needlessly.

What happened to this aircraft, 50/50 the CAAC will not find a cause, and won't agree with Boeing. There is a guy in Denver that worked on kinematic reconstruction of some flight paths by a different method to the one I used in the same accidents, both being variants of MLE to match the couple of data points that existed. In one case, the CVR was able to give the engine RPM from the broad band FFT, and the actual acceleration and deceleration was able to be found from the harmonic lines of the AC system which ran fans in the cockpit; The CSD has a lag function and the overspeed or underspeed of the CSD is traceable on the CVR. The CVR in this case may ahve survived, the EEC memories are most likely to have survived, the DFDR had a less than 50% chance of surviving for various reasons.

it is possible that the debris dispersion analysis with prevailing winds will prove or disprove that any component departed early in the event. It is unlikely, but it would be reavealing if ever found. Components of the stabiliser/elevator and tail will very likely be found from a failure point in the mid dive case, and would be evident as missing components from the local debris field. The military search radar from around Wuxu airbase may have tracked the debris from the aircraft, it is about the right range to have tracked targets.

[B2N2]

Not if you don't pull too hard. And neither will, in every case, cause you to run out of altitude (as appears to be the case here, if indeed the leveloff was deliberate).

Civilian airliners are not rated for high G maneuvers, the 737 is +2.5 /-1 in clean configuration so your choice is to either overstress the airframe or run out of altitude or both if the initial loss of control was at even medium altitudes.
In the sim we do our upset recovery training starting at 20,000’ and I’ve frequently seen recovery as low as 4000’.
Vertical your choice is push or pull, negative or positive G. Anything less then vertical upright you pull, anything less then vertical but inverted would require rolling upright then pull.
I mean we’re talking aerobatic maneuvers here.

[michael9000]

Standard procedure, thrust to idle, wings level, pull to nearest horizon.
With a -1 limit I would not being doing anything negative, it would be the last thing you do.

[Noober]

Am I seeing this correctly that there are two crash sites? The plane looked fairly intact in the videos, at least you could see both wings. Would a single engine have enough force to create the crater in this picture?

Drone footage shows they are a few hundred yards apart. Sorry can't post a damn picture for some reason. Google image search "mu5735 aerial", Pictures 1+2 are a few hundred yards from 3+4

[Lonewolf_50]

This looks like the set of pictures that Noober was referring to.
https://www.google.com/search?q=mu5735+aerial&sxsrf=APq-WBsYUYG1JNRO6QJzSK2opq8wBOKpqw:1648147776604&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjR3ov2tN_2AhXOjYkEHcHRDgwQ_AUoAnoECAEQBA&cshid=1648147862577638&biw=1920&bih=923&dpr=1
@Noober,: Was that right?
https://cimg0.ibsrv.net/gimg/pprune.org-vbulletin/800x400/1648148072_5cf91454f5cb10d3ab340812913188de0decbfa2.jpeg
Pictures 1 & 2
https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/930x558/2119_c4f3f3da74bf80981c63253fb75153ee2e4a8ede.jpg
Pictures 3 & 4

[Noober]

Yep that's correct. There's drone footage floating around on twitter that shows these two locations are about 300-400 yards apart. Seemed a little odd for a plane hitting at that angle.

Bottom picture I believe in the main fuselage.

[silverelise]

Am I seeing this correctly that there are two crash sites? The plane looked fairly intact in the videos, at least you could see both wings. Would a single engine have enough force to create the crater in this picture?

Drone footage shows they are a few hundred yards apart. Sorry can't post a damn picture for some reason. Google image search "mu5735 aerial", Pictures 1+2 are a few hundred yards from 3+4

The press conferences yesterday were reporting two main impact sites both sides of a hill, within 1sq km. They also reported some debris had been found 6 miles away and they were extending their search area as a result.

[tdracer]

Good Grief :ugh::ugh::ugh:
I spent nearly my entire career working jet turbine engines. While the technically correct term is "Thrust Lever", even I use the terms "Thrust Lever", "Throttle Lever", and "Throttle" pretty much interchangeably when talking the subject (I'm rather more careful when writing). Even Boeing people call the automatic thrust control feature "Auto-Throttle" even though those levers it moves are correctly referred to as "Thrust Levers" (and the group that was responsible for the function was always called the "Auto-Throttle Group"). Seriously, is there anyone on this forum who doesn't know what we're talking about when some writes "Throttles" or "Throttle Levers"? Sheese.
Can we possible quit the semantics discussions and get back to the topic of what may have caused this aircraft to crash?

[43Inches]

Good Grief :ugh::ugh::ugh:
I spent nearly my entire career working jet turbine engines. While the technically correct term is "Thrust Lever", even I use the terms "Thrust Lever", "Throttle Lever", and "Throttle" pretty much interchangeably when talking the subject (I'm rather more careful when writing). Even Boeing people call the automatic thrust control feature "Auto-Throttle" even though those levers it moves are correctly referred to as "Thrust Levers" (and the group that was responsible for the function was always called the "Auto-Throttle Group"). Seriously, is there anyone on this forum who doesn't know what we're talking about when some writes "Throttles" or "Throttle Levers"? Sheese.
Can we possible quit the semantics discussions and get back to the topic of what may have caused this aircraft to crash?

It's actually very relevant to this thread, as non english speaking crew can be bamboozled by calling the same thing several names. It's very important when teaching ESL crews that the terminology is spot on. Airbus knows this as parts of the group come from non english speaking nations, hence why a lot of thought is in it's terminology. Boeing, well they just do things and put names that makes it sound different to the competition.

[DaveReidUK]

Fixed links from previous post:

Rescue underway after China air crash (http://en.people.cn/n3/2022/0322/c90000-9974407.html)
Rescue work continues at plane crash site in mountain forests (http://en.people.cn/n3/2022/0323/c90000-9974937.html)
Recovered black box believed to be cockpit voice recorder: official (http://en.people.cn/n3/2022/0324/c90000-9975190.html)
Experts investigate plane crash site as rain hinders rescue work (http://en.people.cn/n3/2022/0324/c90000-9975373.html)
Black box of MU5375 recovered at crashed site (http://en.people.cn/n3/2022/0324/c90000-9975508.html)

[A0283]

Very preliminary impression part2

Photos are not good enough yet, but, Lonewolf_50 's two photo's.

The top photo has a gulley shape, it is not littered with fragments like the bottom photo. The top photo has blackened area's, which may refer to the initial fire. Some parts of the treeline in the bottom photo also appear to have some fire damage.
Based on this my first impression is that the top photo is land erosion and the bottom photo the impact area of the aircraft. So, still one main impact area. And based on official reports also possible but not yet confirmed items shedded earlier, but much further away.

[PoppaJo]

It's actually very relevant to this thread, as non english speaking crew can be bamboozled by calling the same thing several names. It's very important when teaching ESL crews that the terminology is spot on. Airbus knows this as parts of the group come from non english speaking nations, hence why a lot of thought is in it's terminology. Boeing, well they just do things and put names that makes it sound different to the competition.
Agree. QZ8501 is another example, with the aircraft out of control heading towards the ocean, one told the other to ‘pull down’ on the sidestick, amongst numerous other non standard terms. Hardly helped the situation, in fact most certainly contributed to the end result.

[grizzled]

Agree. QZ8501 is another example, with the aircraft out of control heading towards the ocean, one told the other to ‘pull down’ on the sidestick, amongst numerous other non standard terms. Hardly helped the situation, in fact most certainly contributed to the end result.

Hi PoppaJo,

This same sentiment has been expressed by others (re "non-standard" terms) with regard to the accident you mention. I have posted previously on pprune about the problems with judging -- or even trying to understand -- words, phrases and conversations from CVR playbacks. It is something I have experience with, especially in the context of analysing CVR conversations between flight crew with different native languages (as was the case with QZ8501). In the case of QZ8501, the phrase "pull down" is not / was not uttered the way you and others seem to think it was. I was involved in that investigation and I can tell you that specific phrase, in that instance, uttered by that Captain, could easily be the entire subject of a PhD dissertation on multi-language crews in stressful situations. Feel free to PM me if you want to chat about this issue and that particular accident, as discussing it here would quite correctly be considered by the Mods as thread drift.

Cheers,
Grizz .

[FlightDetent]

It's actually very relevant to this thread, as non english speakingNo it is not, not to this thread. Also not everything is about Airbus doing it better.
​​​​​​Chinese crew couldn't care less about 'rooners having a fit because the hair is too thick.

Most likely, outside of the USA, CEAir is one of the worlds top 5 operators of 737 per total accumulated sectors. This won't be a crisis of misunderstanding.
​​​​

[tdracer]

Airbus knows this as parts of the group come from non english speaking nations, hence why a lot of thought is in it's terminology. Boeing, well they just do things and put names that makes it sound different to the competition.
Now you're just being silly. Much of Boeing's terminology pre-dates the very existence of Airbus (heck, some of it probably dates back to WWII if not before). More specifically, the Boeing use of the term "Auto-Throttle' dates back to the 1960's - the early 747s had a system called "FFRATS" - Full Flight Regime Auto Throttle System.
Find me a pilot that doesn't know what "pull back the throttle" means, and I'll show you a pilot that has no business in the pointy end of an aircraft.

[sopwithnz]

"CCTV reported that some parts of the aircraft have been found 255 meters away from the main crash site."
More info here:
https://www.bloomberg.com/news/articles/2022-03-22/china-plane-crash-update-pilots-didn-t-answer-calls-as-jet-dove?srnd=premium-asia

[camel]

https://www.ndtv.com/world-news/second-black-box-of-crashed-plane-not-found-yet-chinese-state-media-2842001

FDR not found .Official statement.

[camel]

Live stream https://www.youtube.com/watch?v=l0JTYp0d99U

[notmanyflyinghours]

According to CNN (sorry can't post URLs but its front page...)

"The airline and its subsidiaries have temporarily grounded 223 Boeing 737-800 aircraft, airline spokesperson Liu Xiaodong said in a press conference on Thursday. The same type of plane was involved in the crash.".

[bsieker]

Officials at the press conference (in the CGTN live stream linked above) just stated that they were going to release the report(s) in English, as well as Chinese. Chinese is an ICAO working language, so they are not obliged to, but I guess they realise the international importance of this accident.

[A0283]

The life feed shows video from this morning. The search at that time recovered what appears a big fragment of the top of one MLG, broken in half, the big connection rods broken in half (deformation - no plasticity it seems), trunnion on one side still shiny, the fragment required 5-6 man to carry, so say roughly at least 120kg weight.

Recovery status impression around 1050utc:

cockpit area - probably or only light material (documentation reported),
tail - maybe found today 25th,
horizontal stabiliser - big part suggested but not seen in photo or videostream yet,
winglet left hand - no sign,
winglet right hand, with part of the outer wing - right hand most likely,
wing itself - fragments of outer wing possible,
fuselage - from early on part of the top panel in front of the fwd escape hatch, probable,
fuselage - multiple large pieces of outer shell, all bent and torn and pushed flat,
engine - one certain, other no sign,
MLG/NLG - suggested is one of the main,
instruments - no sign or report of any till now,
instruments - wiring, no sign or report of any till now
total - in total about 183 parts, bigger fragments are collected in a row of tents on location,
total - a few hundred structure fragments and perhaps other types of fragments in between,
CVR - confirmed

Rough outline of the accident area:

The main area of interest is running N to S in what I call the gulley (low valley you might say). In the upper half of that NS-stretch is the main impact area which contains almost all (bigger) fragments). To the North of the gulley is a burned forrested area. The area with the 'possible burned landslide' (the other one of Lonewolf_50s two photos) is an estimated 300-400 m to the East and has no involvement with the accident.

[EDLB]

SCMP writes that they found potential parts 10km (6miles) from the crash site.
https://www.scmp.com/news/china/article/3171854/china-eastern-flight-5735-suspected-debris-found-10km-crash-site-search?utm_source=copy_link&utm_medium=share_widget&utm_campaign=3171854

Which would mean that something departed long before impact form the plane.

[Mudman]

SCMP writes that they found potential parts 10km (6miles) from the crash site.
https://www.scmp.com/news/china/article/3171854/china-eastern-flight-5735-suspected-debris-found-10km-crash-site-search?utm_source=copy_link&utm_medium=share_widget&utm_campaign=3171854

Which would mean that something departed long before impact form the plane.
10km radius around the crash site.
https://cimg0.ibsrv.net/gimg/pprune.org-vbulletin/2000x1242/crash_site_10km_radius_158ba995e63b9c76476c0544c06918b8f4733 101.jpg
10km radius around crash site

[Teddy Robinson]

SCMP writes that they found potential parts 10km (6miles) from the crash site.
https://www.scmp.com/news/china/article/3171854/china-eastern-flight-5735-suspected-debris-found-10km-crash-site-search?utm_source=copy_link&utm_medium=share_widget&utm_campaign=3171854

Which would mean that something departed long before impact form the plane.
from the article "Zheng Xi, head of the Guangxi regional fire and rescue office, said the piece of suspected wreckage was about 1.3 metres long and 10cm wide (4.3ft by 4 inches).
It was found 10km away and the search area was expected to be expanded by half, he told a press conference in Wuzhou, near the crash site."

Balance tab ?

[silverstrata]

.
When the 737 NG was first introduced it did lose a number of elevators in flight, due to excessive turbulence from the flight spoilers. So the max speed for spoiler deployment was reduced to 240 kt for a number of years - which was a pain in the arrse on the descent, because the spoilers are only really effective at high speeds (when the angle of attack is reduced).

To cure the problem, an extra hinge-point was added to the NG elevator, to stop them falling off.
Needless to say, losing elevators can spoil your day.

Silver

[nnc0]

Is it curious that the CVR module has been recovered but not the FDR?

Given the speed of Impact and trajectory I'd expect them to be found right beside on another. The crater isn't that big so where is it?

[EDLB]

The plane crashed with bullet speed into the ground leaving mostly small shrapnel sized parts. So the remains will be in the 30m radius by 20m depths shared with all other ingredients. The people working there have my deepest respect. The FDR memory will be found but it can take a while. The Chinese make a very professional job there so we will get to the true cause of this accident.

[DaveReidUK]

Is it curious that the CVR module has been recovered but not the FDR?

Given the speed of Impact and trajectory I'd expect them to be found right beside on another. The crater isn't that big so where is it?

I believe the recorders in one or both of the Max accidents were only found after much searching, so it's not altogether surprising that the Chinese FDR is still outstanding.

Both recorders will have been reduced to mangled fragments - only the stainless steel or titanium shell that protects the memory modules needs to survive - and the missing one could well be several feet down in the mud.

[grizzled]

Both recorders will have been reduced to mangled fragments - only the stainless steel or titanium shell that protects the memory modules needs to survive - and the missing one could well be several feet down in the mud.DRUK has it exactly right. Sadly, I have been to several accident sites involving high speed, near vertical impacts. You cannot imagine (don't want to imagine) such a scene. In addition to everything being reduced to simply fragments, those fragments are twisted, torn, dirt or mud-covered (sometimes burned) pieces of pieces of pieces. The orange boxes (exterior portions) are no exception, as they are usually the same dirty colour as everything else, and often in smaller pieces as well. Almost nothing looks like something you would recognize, because everything was crushed and conglomerated in an instant.

So, patience is called for, as is a large dose of respect and empathy for those doing the onsite work.

[Sailvi767]

All 737-800s at MU are grounded
My hunch is a runaway trim.

Why would they not simply disconnect the trim or just grab the trim wheels? Both those fixes assume the system that automatically shuts down a runaway trim if the control column moves opposite the trim direction has failed. A runaway trim at cruise altitude should be a non event.

[Mookiesurfs]

Why would they not simply disconnect the trim or just grab the trim wheels? Both those fixes assume the system that automatically shuts down a runaway trim if the control column moves opposite the trim direction has failed. A runaway trim at cruise altitude should be a non event.
They could and they would. Probably not runaway trim, imo. A more plausible scenario for trim related loss of control at altitude is a gradual failure of a system that causes the autopilot to trim unremarkably, like a gradual fuel imbalance, rollback, or something else. The AP will trim to the limit of its authority and then kick off, handing you a plane that is well out of trim. This really should be manageable at 29,000’ but can be tricky the closer you get to 41,000’.

We can’t rule out a catastrophic event at cruise yet, bomb or otherwise.

[Sailvi767]

They could and they would. Probably not runaway trim, imo. A more plausible scenario for trim related loss of control at altitude is a gradual failure of a system that causes the autopilot to trim unremarkably, like a gradual fuel imbalance, rollback, or something else. The AP will trim to the limit of its authority and then kick off, handing you a plane that is well out of trim. This really should be manageable at 29,000’ but can be tricky the closer you get to 41,000’.

We can’t rule out a catastrophic event at cruise yet, bomb or otherwise.

The trim system in the 737 is very obvious if not annoying when running. That includes when the autopilot trims. If in fact they ignored the spinning trim wheels and noise as soon as the autopilot moved the elevator to counter the incorrect trim input the trim brake would engage and stop the runaway.

[PJ2]

FWIW, I don't see a longitudinal trim issue (runaway stab) as causal, particularly with fuel distribution which is primarily a lateral issue, (also, not sufficient fuel on board to cause a large imbalance issue), or an engine "roll-back", ("lateral roll followed by upset" scenario). Also, continuous stab trim operation would be immediately noticeable these days & handled as per (non-MAX) runaway drills.

So far, we haven't seen any thorough analyses of the vertical development of weather in the area. Tim Vasquez produced some great work, many years ago now, on the AF447 threads.

Whatever occurred, did so very swiftly.

Horizontal stabilizer jackscrew operation:

https://www.youtube.com/watch?v=rxPa9A-k2xY

[Mookiesurfs]

The trim system in the 737 is very obvious if not annoying when running. That includes when the autopilot trims. If in fact they ignored the spinning trim wheels and noise as soon as the autopilot moved the elevator to counter the incorrect trim input the trim brake would engage and stop the runaway.
It’s noticeable, but we’re talking intermittent inputs here, not a constant running. Anyone with time in type knows that the plane is constantly making intermittent trim inputs on its own, and that it is normal unremarkable background cockpit noise. A constantly running trim would be remarkable, but that’s not what we’re talking about.

[exosphere]

Regarding the wreckage piece allegedly found 10km away, it could well be that the initial upset caused it, but it’s not necessarly the reason for that upset. Entering such a dive would require a relatively quick pitch down which also means negative G’s, maybe exceeding final load factor.

[Al Symers]

Don’t rule anything out. If you saw some of the crazy sh!t I saw flying in China you’d agree that just about any scenario is possible.

59 y.o. Captain gets hard terrain warning. Must be punished. Downgraded to FO as he approaches retirement. Gets rostered with a leader captains (who downgraded him) son. Makes for an interesting cockpit dynamic. Who’s really in control in that situation? Anyone who’s flown in China knows it’s not the guy in the LHS. Up there it doesn’t matter a damn what’s right, it’s all about who’s right. Add in lots of hands on the controls, (a staple in Chinese aviation) and it doesn’t take much to create a disaster.

Might have just been the cranky old guy giving the yoke a shake to make a point, or stomping on the rudder (yup, seen that happen), with zero regard for consequences. Engine failure and stall also a possibility, keeping in mind that if you let a yaw develop in to a roll, it will eventually lead to aerobatics if left unattended.

Saying aviation in China is much safer than it used to be is like saying wars aren’t as messy as they used to be. The weapons may have changed but it’s the same result in the end.

[Turkey Brain]

……. Entering such a dive would require a relatively quick pitch down which also means negative G’s, maybe exceeding final load factor.

Assuming the descent started at the time of the last cruise data point, a big assumption !
To lose 2,000 ft in 14 seconds is average about plus 0.3 g.

As long as the descent started at least 11 seconds of the first altitude readout of 27,025 ft then zero g would suffice.

Coincidently, if the descent was at an average of zero g for 11 seconds the rate of descent would be 21,737 ft/min at the next data point, 27,025 ft. using my simplified calcs. Assuming gravity, G = 10 m/s etc. So rough calcs.

The data point from FR24 gives a Rate of Descent at 21,696 ft/min.

So surprisingly similiar numbers. Maybe I made a mistake in my calcs.


But if correct, the aircraft didn’t need a high negative g bunt to achieve the initial descent, just a lack of lift.

All pretty horrible, but many scenarios achieve these numbers. 2 immediately spring to mind.

1: Wings level zero g profile.

2: a roll past or near 90 degrees.


1: The wings level zero g scenario seems highly unlikely, a jack fail or trim run away would in my guess be unlikely to achieve exactly zero g. I would assume some sort of dramatic manoeuvre but this is not an area where I have any expertise.

2: So very little lift component up. The problem with the roll case seems to be the lack of heading change.


The fidelity of the FR24 data may mask track changes. I note a 2 degree track change to the left passing 27,000 ft and 10 degrees left passing 25,000 ft. It’s back on track,( 100 degrees ) at 22,500 ft, but by 15,000 ft it’s now deviated to a track 40 degrees to the right.

A slow spiral ?

I can’t tell from the numbers. Maybe someone can.



equations used.

V^2 = U^2 + 1/2 a t ^2. V = velocity achieved, U initial velocity ( 0 in this case ) , a acceleration, t time

S = Ut + 1/2 a t ^ 2. S = distance

[fdr]

FWIW, I don't see a longitudinal trim issue (runaway stab) as causal, particularly with fuel distribution which is primarily a lateral issue, (also, not sufficient fuel on board to cause a large imbalance issue), or an engine "roll-back", ("lateral roll followed by upset" scenario). Also, continuous stab trim operation would be immediately noticeable these days & handled as per (non-MAX) runaway drills.

So far, we haven't seen any thorough analyses of the vertical development of weather in the area. Tim Vasquez produced some great work, many years ago now, on the AF447 threads.

Whatever occurred, did so very swiftly.

Horizontal stabilizer jackscrew operation:

https://www.youtube.com/watch?v=rxPa9A-k2xY


Nor do I;

reading the follow on posts, here is some physics for pondering for the other posts....

Planes fly nicely unless they are either -

commanded to do something else; or
upset by external factors; or
the fundamental stability of the toy gets upset.

A plane that is happily bumbling along at 1.0g doesn't suddenly decide to go to 0.3g. the trim solution is to an angle of attack, and it is not going to have a large excursion from that to some other value just because the autopilot decided to turn off. If the autopilot elected to enter a wild ride, then as long as the autotrim function is running the plane will happily retrim to the new angle of attack and do what the errant autopilot computer is commanding. The plane continues otherwise doing its short period or long period oscillations around the mean trim alpha. Yaay. has been like that since Wilbur and Orville decided that the world needed flight attendants to make it a more palatable life.

A pilot pushing on the prong will drop the nose, as long as he (or she, but most she's are not stupid enough to do what the boys do) is pushing. As soon as he (or she) lets go of the input, the plane is going to revert to the trimmed alpha, and it will do a recovery all on its lonesome. Not just nice to have, it is a mandatory design requirement, even for unstable designs, the 1's and 0's have to be able to guarantee that is always the case.

getting to a seriously nose low condition takes a lateral excursion in order to occur unless the tail has gone its own way, and as was previously mentioned, with Lauda 004, "Mozart?" when the inadvertent thrust occurred on an engine in the mid climb, the PW4060 issue resulted in a huge disruption of the flow over the wing section immediately behind the nacelle, and that caused a large lift loss as well as yaw. As the aircraft rolled from the loss of lift, and from the secondary effect of the yaw, eventually the structure got to a point of exceeding the strength of the tail and the tail failed, by memeory with an asymmetric failure of the horizontal stab/elevator and then complete failure of the vertical stab, whatever, shortly thereafter, from the loss of the horizontal stab, the Cm from the wing and the CG shift of losing a stack of weight at the tail resulted in a rapid pitch down, that ended up with an overload of the main wing from an excessive negative g loading, after which the wings departed, and what was left was not much at all. A full on failure of the tail usually ends with the sky filled with chaff, an inflight breakup is almost always the outcome. JAL103 was an exception to that.

An aircraft that has a lateral upset is the most common means of getting into a nose low attitude. This can be from curious causes, Silkair being one, or the Classic loss out of Jakarta last year with the autothrottle clutch pack issue, or from entry into turbulence, or from instrument failures, like Stansteds B747-200F loss, or Adam Air with the INS's attitude being reset in IMC... that'll do it every time. When the aircraft rolls to a high bank level or inverted, the longitudinal stability will tend to drop the nose as the plane enters a spiral at high bank angles or tries to do a split S if inverted. The planes stab trim doesnt need to be altered and the outcome is a degrading flight path. What doesn't happen is the plane going to 0.3 g or other, it is trying to get back to the trimmed alpha, and that means it will tighten at the high bank angles, so g loadings increase. Tracking data if it is reasonably high resolution may show that a track change has occurred, but getting the nose down without changing the trim needs the roll.

On the morning of this accident, I was planning a medevac into China for the following day, and the plane involved had a recent radar issue that had resulted in a radar swap. As part of the planning, I looked at the weather in southern and eastern China, about 4 hrs before the accident and there was convective weather forecast near Guangzhou and to the west, and otherwise the area was quite clear. tops above FL260 were not significant except in that area, and the lightning strikes were being displayed in that area, then next closest area was over Pusan/Pohang and south of Vladivostok.

The grounding of 200 plus B738s seems to be premature. Unless there is clear evidence of a stab tab or other item falling off around the top of the drop, there is not much likelihood int his case that a structural failure was involved. Parts that separated part way down were unlikely to be the cause, they are the consequence.

Having said all of that, occasionally stuff really is surprising. I recall one investigation where the crew got 12,500FPM upwards, busted the assigned altitude by 4000' topped out at 0.2g, and then got 12000FPM on the down side and busted the assigned altitude a second time for good measure. The pull up was 1.3g, the over the top was 0.2, and the pull out was 1.3g. That got a spot on the wall, for the rest of the day until the next incident surpassed it. During the rollercoaster, the Captain managed to complete the full multi language PA to the passengers welcoming them on board and thanking them for choosing to fly brand X. The FO has the misfortune to be in a spritely climb in a light plane and to encounter an entry into a jetstream that increased the headwind by well over 100kts over 4000' and he elected to stay in FCLH targetting Mach.... so the latter climb was all done with the thrust levers at idle, and one very confused FO. The cabin crew continued their excellent, long suffering service, and didn't leave any dents in the ceiling.

TBs maths is OK for a wings level entry, using a dFPV/dt, V input, to determine a g loading, but anything that achieves that in a wings level condition is a seriously catastrophic event, the fact that the aircraft had any reduction in the severity of the dive angle suggests it was still responsive to control un until the time it then wasn't. 73 drivers don't often do push overs, recall that they drivers are sitting a fair arm forward of the CG, and the rate of pitch needed to go to zero g gets the drivers up close and personal with the fuel panel and the pressurisation control panel unless well strapped in.

Pushing to zero g and holding it for any time is a good push on the prong, gonna get tired doing that for long, and to hold it, without running the stab trim, that is a big ask

[CodyBlade]

https://www.youtube.com/watch?v=KhfxEjnsOd0

[henra]

TBs maths is OK for a wings level entry, using a dFPV/dt, V input, to determine a g loading, but anything that achieves that in a wings level condition is a seriously catastrophic event,
And a bizzare one for that matter. I do not see many mechanical ways to end up with a proper wings level 0g nose dive from cruise. Trim runaway with full ND deflection and then the AP letting go would rather end up with negative g and seems also extremely unlikely. Why would the trim want to do that? Mis- trim scenarios did happen in the past but that was typically at low speeds, e.g. during approach but at cruise speed???
Losing Vertical tail will involve yaw/roll (could potentially be the case but the trajectory speeds >M0,9 do not smell like any kind of tumbling). Losing horizontal tail at cruise speeds would lead to massive negative g and shedding wings downward. Terminal angle being 90°ish. Jackscrew nut leeting go. That might hypothetically be possible. But in a seven y/o aircraft?? And then, why exactly at TOD? why suddenly and fully in one go without any prior 'warning'? In the case of the Alaska MD the failure developed over some time. The flight profile here appeared absolutely clean until the drop.
I'm somewhat struggling to conceive a 'hard' mechanical failure leading to the profile we apparently have seen here.

[PJ2]

The reliance upon FR24 data as an investigative, diagnostic or even theorizing tool is significantly beyond its design, conception and utility.

While "realistic" results may obtain on occasion, its equivalence to reality is largely stochastic.

The process of building a theory and then going to data to find support is essentially what is occurring through the use of FR24 data. The method is faulty simply because the data isn't good enough to do so. FR24 data is not validated through testing to the same precise standards & legal requirements that DFDR data is. It has its uses, but not in the manner being sought here.

The only tools registered and recognized for such work are the SSCVR & SSFDR, and even then, as we have seen, from such a point there can still be a number of valid theories & interpretations, some ultimately critical to understanding what actually occurred.

If scientists had gone about validating MRNA vaccines in the same manner, we would not be as eager to use them and the FDA would have trouble justifying their wide public use. The principle here and elsewhere in other investigative endeavours is the same.

Respect for the data and for accuracy is paramount as many lives have been affected.

PJ2

[MLHeliwrench]

Something very sudden and catastrophic must of happened to go from stable cruise to becoming a barely controllable missile.

an earlier update from searchers said there is no sign of a second engine (having found only one).

At least one part has been found 10 km away.

an engine falling off would definitely cause an upset! What was the maintenance done in the preceding couple days?

[A0283]

MLHeliwrench

If you refer with your #215 to my #193 update on the search ? ... I have to say that it mixes official statements, statements of the reporter on-site (who do seems to talk to the investigators and police that are present on site), and my own observations based on the photos and videos that I found.

Your ... "So when an earlier update from searchers said there is no sign of a second engine (having found only one)."
In my post that means that I have only seen one engine (100% sure, seems complete but with hi spd impact flattening). As far as I know, pity I dont speak Chinese, there have not been any official statements on the engines, or the four corners for that matter.

Your ... "At least one part has been found 10 km away."
Officials reported that a1.3m x 10cm wide piece was found by a farmer in his field. Up till now I have not heard any confirmation that it actually belonged to a plane or the plane. A bit odd that it takes so long.

There is a big piece reported to be part of the THS (I have a photo that seems to be the one they mean, still have to check that), both by the reporters and repeated by officials. No reports on elevators.

There was a report on a big piece that was found yesterday morning, the reporter said they thought it was the tail, but at the end of the day it was still sitting there and not completely dug out. Very hard to get heavy pieces from there. The winglet and part of the outer wing was removed by using a kind of bamboo sled on a bamboo road. After they had moved it, the bamboo road was unuseable.

So, very important information that can reduce the number of possible scenario's is still missing.

There is one remaining row of blue tents were all the parts are collected, cleaned and sorted. The other row has been removed to make way for the excavators. They now have so many fragments (I can't call them parts) that they are going to create a special area in the next few days for the processed ones. Another next step is taking the 'mud' (it was still raining) and filtering that in two stages to try to filter out everything. The 'gulley' is now being dug out both North to South and sideways. As officially stated the main impact area had a radius of 30m and a depth of 20m. With rain starting about 2 days after the crash but continuing, makes it a heck of a job, they are now removing part of the bamboo forest, working even harder on drainage, etcetera.

So a lot of hard work still going on.

The engine scenario is an interesting one. People will say unlikely, but would be interesting to factor in asymmetry and loss of thrust.

[meleagertoo]

Why would they not simply disconnect the trim or just grab the trim wheels? Both those fixes assume the system that automatically shuts down a runaway trim if the control column moves opposite the trim direction has failed. A runaway trim at cruise altitude should be a non event.
Well, we got shouted down asking that question of the two MAX accidents as it somehow implied the pilots hadn't done their job properly and was taking some of the heat off the anti Boeing witchunt that was the only politically acceptable cause in town..
What's different here?
But of course you're right, with a runaway trim you do the drills and circumvent it. Easily.

[A0283]

From official reports: "Rescuers have found the emergency locator transmitter (ELT) installed near the second black box <the FDR> of the crashed plane. .. Search in the main impact area … More orange pieces were found at the core search area that experts later verified are parts of the black box."

Next to that, a photo shows that a 3D model of the impact site is being prepared. There is no information on either a photogrammetry or LIDAR basis. But I think this will certainly become a standard tool in the accident investigation toolbox. Especially useful in remote and uncharted locations like these.

[sikeano]

Nor do I;

reading the follow on posts, here is some physics for pondering for the other posts....

Planes fly nicely unless they are either -

commanded to do something else; or
upset by external factors; or
the fundamental stability of the toy gets upset.

A plane that is happily bumbling along at 1.0g doesn't suddenly decide to go to 0.3g. the trim solution is to an angle of attack, and it is not going to have a large excursion from that to some other value just because the autopilot decided to turn off. If the autopilot elected to enter a wild ride, then as long as the autotrim function is running the plane will happily retrim to the new angle of attack and do what the errant autopilot computer is commanding. The plane continues otherwise doing its short period or long period oscillations around the mean trim alpha. Yaay. has been like that since Wilbur and Orville decided that the world needed flight attendants to make it a more palatable life.

A pilot pushing on the prong will drop the nose, as long as he (or she, but most she's are not stupid enough to do what the boys do) is pushing. As soon as he (or she) lets go of the input, the plane is going to revert to the trimmed alpha, and it will do a recovery all on its lonesome. Not just nice to have, it is a mandatory design requirement, even for unstable designs, the 1's and 0's have to be able to guarantee that is always the case.

getting to a seriously nose low condition takes a lateral excursion in order to occur unless the tail has gone its own way, and as was previously mentioned, with Lauda 004, "Mozart?" when the inadvertent thrust occurred on an engine in the mid climb, the PW4060 issue resulted in a huge disruption of the flow over the wing section immediately behind the nacelle, and that caused a large lift loss as well as yaw. As the aircraft rolled from the loss of lift, and from the secondary effect of the yaw, eventually the structure got to a point of exceeding the strength of the tail and the tail failed, by memeory with an asymmetric failure of the horizontal stab/elevator and then complete failure of the vertical stab, whatever, shortly thereafter, from the loss of the horizontal stab, the Cm from the wing and the CG shift of losing a stack of weight at the tail resulted in a rapid pitch down, that ended up with an overload of the main wing from an excessive negative g loading, after which the wings departed, and what was left was not much at all. A full on failure of the tail usually ends with the sky filled with chaff, an inflight breakup is almost always the outcome. JAL103 was an exception to that.

An aircraft that has a lateral upset is the most common means of getting into a nose low attitude. This can be from curious causes, Silkair being one, or the Classic loss out of Jakarta last year with the autothrottle clutch pack issue, or from entry into turbulence, or from instrument failures, like Stansteds B747-200F loss, or Adam Air with the INS's attitude being reset in IMC... that'll do it every time. When the aircraft rolls to a high bank level or inverted, the longitudinal stability will tend to drop the nose as the plane enters a spiral at high bank angles or tries to do a split S if inverted. The planes stab trim doesnt need to be altered and the outcome is a degrading flight path. What doesn't happen is the plane going to 0.3 g or other, it is trying to get back to the trimmed alpha, and that means it will tighten at the high bank angles, so g loadings increase. Tracking data if it is reasonably high resolution may show that a track change has occurred, but getting the nose down without changing the trim needs the roll.

On the morning of this accident, I was planning a medevac into China for the following day, and the plane involved had a recent radar issue that had resulted in a radar swap. As part of the planning, I looked at the weather in southern and eastern China, about 4 hrs before the accident and there was convective weather forecast near Guangzhou and to the west, and otherwise the area was quite clear. tops above FL260 were not significant except in that area, and the lightning strikes were being displayed in that area, then next closest area was over Pusan/Pohang and south of Vladivostok.

The grounding of 200 plus B738s seems to be premature. Unless there is clear evidence of a stab tab or other item falling off around the top of the drop, there is not much likelihood int his case that a structural failure was involved. Parts that separated part way down were unlikely to be the cause, they are the consequence.

Having said all of that, occasionally stuff really is surprising. I recall one investigation where the crew got 12,500FPM upwards, busted the assigned altitude by 4000' topped out at 0.2g, and then got 12000FPM on the down side and busted the assigned altitude a second time for good measure. The pull up was 1.3g, the over the top was 0.2, and the pull out was 1.3g. That got a spot on the wall, for the rest of the day until the next incident surpassed it. During the rollercoaster, the Captain managed to complete the full multi language PA to the passengers welcoming them on board and thanking them for choosing to fly brand X. The FO has the misfortune to be in a spritely climb in a light plane and to encounter an entry into a jetstream that increased the headwind by well over 100kts over 4000' and he elected to stay in FCLH targetting Mach.... so the latter climb was all done with the thrust levers at idle, and one very confused FO. The cabin crew continued their excellent, long suffering service, and didn't leave any dents in the ceiling.

TBs maths is OK for a wings level entry, using a dFPV/dt, V input, to determine a g loading, but anything that achieves that in a wings level condition is a seriously catastrophic event, the fact that the aircraft had any reduction in the severity of the dive angle suggests it was still responsive to control un until the time it then wasn't. 73 drivers don't often do push overs, recall that they drivers are sitting a fair arm forward of the CG, and the rate of pitch needed to go to zero g gets the drivers up close and personal with the fuel panel and the pressurisation control panel unless well strapped in.

Pushing to zero g and holding it for any time is a good push on the prong, gonna get tired doing that for long, and to hold it, without running the stab trim, that is a big ask



Thank you that is very informative

[sopwithnz]

'Your ... "At least one part has been found 10 km away."
Officials reported that a1.3m x 10cm wide piece was found by a farmer in his field. Up till now I have not heard any confirmation that it actually belonged to a plane or the plane. A bit odd that it takes so long.'

Maybe not confirmed, but it was reported in the presser about 12 hours ago that they have dispatched four full search teams in that direction for 10 kms away from main crash site.

What a massive and terrible task .. highest respect for them all.

[sopwithnz]

Bloomberg reporting:China said it hasn’t found any evidence of explosive materials in the wreckage of a China Eastern Airlines (https://www.bloomberg.com/quote/600115:CH) flight that crashed with 132 people on board.

“Lab tests taken of 66 samples, 41 of which have been completed, showed no major common inorganic explosive or common organic explosive substances have been found,” fire official Zheng Xi said at a briefing in the southern city of Wuzhou on Saturday.

Zhu Tao, an official with the Civil Aviation Administration of China, added that investigators found a transmitter installed close to a missing black box that records flight data, but haven’t retrieved the device itself. A black box that captures voices in the cockpit was found earlier.

Some 24,000 pieces of wreckage have been retrieved, officials said, and remains of 120 people have been identified. The search is focused on an area with a radius of 300 meters (about 330 yards) from the main crash site, though part of a wingtip was found (https://www.bloomberg.com/news/articles/2022-03-24/china-crash-mystery-deepens-as-evidence-suggests-midair-breakup) 12 kilometers away.

More at link .. https://www.bloomberg.com/news/articles/2022-03-26/china-says-no-trace-of-explosives-found-in-jet-crash-samples?srnd=premium-asia

[JanetFlight]

If a wing tip was found 12 kms away, imho this very case has some similarities with both Ceiba 738 and GOL 738 (both coliding with exce/biz jets) but however with different outcomes...in GOL case survived the Bizjet, in CEIBA survived the 738.
Could it be the case and being China such a military country they had some midair colision with an UAV, Drone, mil device, etc?

[Lake1952]

Well, we got shouted down asking that question of the two MAX accidents as it somehow implied the pilots hadn't done their job properly and was taking some of the heat off the anti Boeing witchunt that was the only politically acceptable cause in town..
What's different here?
But of course you're right, with a runaway trim you do the drills and circumvent it. Easily.

Forgive my ignorance, but I thought that there were regimes where runaway nose down trim causes the autopilot to say "it's yours" and given the resultant high speed dive, it can be nearly impossible to manually dial back the trim wheel without resorting to a phugoid yo-yo maneuver.

[cncpc]

Credentials:
15 years Royal Australian Air Force. Qualified on PC9, C-130, Macchi MB-326, F/A-18, Hawk-127. Qualified Flying Instructor, Instrument Rating Examiner, Low Level Demonstration Pilot, Flying Safety Officer.
15 years airline pilot. Captain on A350, A330.

Causative Factors:
Absolutely no idea. How could I offer an opinion before the data is in?


My deepest condolences to the families of those involved.

Lol, saved me the effort. Well said, indeed cleverly , and aimed at the man on the high horse.

I like to hear what the "amateurs" say.

[theFirstDave]

The trim system in the 737 is very obvious if not annoying when running. That includes when the autopilot trims. If in fact they ignored the spinning trim wheels and noise as soon as the autopilot moved the elevator to counter the incorrect trim input the trim brake would engage and stop the runaway.

Does not the 737 AP trim via moving the stabilizer, not the elevator?

[camel]

FDR recovered.

https://www.youtube.com/watch?v=BlGrTB2ivy4

[sopwithnz]

https://cimg5.ibsrv.net/gimg/pprune.org-vbulletin/522x324/capture_59c2cecb9c79f96b1f744095a376c42e695dce88.jpg

[finestkind]

Lol, saved me the effort. Well said, indeed cleverly , and aimed at the man on the high horse.

I like to hear what the "amateurs" say.

Tend to agree especially if someone states this is the reason. Maybe I missed that but most appear to have indicated along the lines of this "may have happened".
.
In respect to offering an opinion, "Causative Factors:
Absolutely no idea. How could I offer an opinion before the data is in?.

An opinion is "a view or judgement formed about something not necessarily based on fact or knowledge". So by all means offer your opinion and if outside the bounds of reasonability standby to receive.

[Spotted Reptile]

10km radius around the crash site.
https://cimg0.ibsrv.net/gimg/pprune.org-vbulletin/2000x1242/crash_site_10km_radius_158ba995e63b9c76476c0544c06918b8f4733 101.jpg
10km radius around crash site
According to SCMP News article (https://www.scmp.com/news/china/article/3171854/china-eastern-flight-5735-suspected-debris-found-10km-crash-site-search) the farmer who found the piece lives at Yatang which is SW of Tangbuzhen on a hill. On the image above it is where the red line crosses that industrial complex to the right of the Yandong town label next to the river.

[pattern_is_full]

Well, the 737 series did have a problem in the early 1990s that caused several hard-over events (and two crashes). Jamming of a valve in the rudder hydraulic power unit.

However, to the original question, that was fixed with a new part design, and there have been no recurrences in 26 years. So no reason at all to think it especially probable in a 737 built in this century.

[sopwithnz]

reporting more wreckage has been found today 8 kms away from main site ... https://www.youtube.com/watch?v=8q0YVV3khaM

[Sailvi767]

Does not the 737 AP trim via moving the stabilizer, not the elevator?

You are correct.

[Sailvi767]

Well, we got shouted down asking that question of the two MAX accidents as it somehow implied the pilots hadn't done their job properly and was taking some of the heat off the anti Boeing witchunt that was the only politically acceptable cause in town..
What's different here?
But of course you're right, with a runaway trim you do the drills and circumvent it. Easily.

Because MCAS on the Max does not act quite like a normal runaway trim and defeats the trim brake.

[etrang]

Tend to agree especially if someone states this is the reason. Maybe I missed that but most appear to have indicated along the lines of this "may have happened".
.
In respect to offering an opinion, "Causative Factors:
Absolutely no idea. How could I offer an opinion before the data is in?.

An opinion is "a view or judgement formed about something not necessarily based on fact or knowledge". So by all means offer your opinion and if outside the bounds of reasonability standby to receive.
No, there's no reason to preclude it, but no reason to include it either. There are countless possible causes, so its not helpful to raise them all without some sort of supporting evidence. This is probably why your earlier post was deleted.

[PJ2]

While I do agree from a technical perspective, historically in past accidents the ADS-B data rarely if ever painted a really different picture regarding trajectory/flight path and velocities than were leater determined by the proper tools.Thank you for your response.

FR24 began in 2009, so there was nothing available from AF447 at the time, but we did use the ACARS messages to read the tea leaves in the AF447 accident and got quite a bit from that source until the recorders were located two years later. But until we had the side-stick parameters, the stall-warning parameter plus pitch/roll, it was not possible to say where the problem originated and why; from the AF447 thread in Tech Log on ACARS: https://www.pprune.org/tech-log/376433-af447-2.html#post4975184

Data is not opinion, nor is validated data stochastic. That's really my only argument. There can be a form of equivalence between FR24 information and the eventual results from the recorders but the former cannot be turned into action nor legitmately be included as part of any final report / recommendations.

[DaveReidUK]

While I do agree from a technical perspective, historically in past accidents the ADS-B data rarely if ever painted a really different picture regarding trajectory/flight path and velocities than were later determined by the proper tools.

That has certainly been true - up to a point - for the dozens of accidents/incidents that have featured in these columns over the years and where FDR traces have subsequently been published in the investigation report (including the two Max accidents).

But there is an important caveat: ADS-B data (as transmitted by the aircraft) and an FR24 download (however granular) are not the same thing. The latter will be subject to asynchronicity, hysteresis and latency - though many (but not all) of those issues can be mitigated with some work and patience.

So, while I have no sympathy for the knee-jerk "ADS-B is rubbish" view sometimes expressed in these columns, nor do I agree with the "ADS-B is gospel" view when applied to FR24 data.

[henra]

Data is not opinion, nor is validated data stochastic. That's really my only argument. There can be a form of equivalence between FR24 information and the eventual results from the recorders but the former cannot be turned into action nor legitmately be included as part of any final report / recommendations.

Fair and valid comment! I do agree.

[Ka6crpe]

I know this is pure speculation but one report says "One possibility is that this 737 may have previously been involved in a tail strike incident on landing or take-off and the damage done to the rear pressure bulkhead was not noticed or not repaired properly causing it to fail, damaging the tail."

Has there been any evidence to support this or are they just making noise?

https://www.airlineratings.com/news/china-eastern-crash-second-black-box-new-wreckage-found-10km-away/

[DingerX]

The reliance upon FR24 data as an investigative, diagnostic or even theorizing tool is significantly beyond its design, conception and utility.

While "realistic" results may obtain on occasion, its equivalence to reality is largely stochastic.

The process of building a theory and then going to data to find support is essentially what is occurring through the use of FR24 data. The method is faulty simply because the data isn't good enough to do so. FR24 data is not validated through testing to the same precise standards & legal requirements that DFDR data is. It has its uses, but not in the manner being sought here.

The only tools registered and recognized for such work are the SSCVR & SSFDR, and even then, as we have seen, from such a point there can still be a number of valid theories & interpretations, some ultimately critical to understanding what actually occurred.

If scientists had gone about validating MRNA vaccines in the same manner, we would not be as eager to use them and the FDA would have trouble justifying their wide public use. The principle here and elsewhere in other investigative endeavours is the same.

Respect for the data and for accuracy is paramount as many lives have been affected.

PJ2

Of course, that invites its own study. Take the last 10-20 incidents discussed on PPRUNE for which a final report is available. How do the publicly available ADS-B data match the DFDR readout and the reconstruction? What percentage of posts mention technical details or theories considered by the final report, compared to issues not mentioned (and thus probably irrelevant noise)?
How much should we respect the data?
​data?
Since Traditional and Internet news outlets routinely raid forums like this one, maybe we should scientifically assess the information that comes out here. I won't even ask to be principal author.

[B2N2]

Second black box found

https://www.channelnewsasia.com/asia/china-eastern-crash-second-black-box-found-2589126

[WideScreen]

....
Planes fly nicely unless they are either -

commanded to do something else; or
upset by external factors; or
the fundamental stability of the toy gets upset.

......
I like your writing style, full of subtle references to past happenings, as discussed on PP.

Your list of conditions does suggest something "permanent", IE mechanics, though the issue with fundamental toy stability can also be something intermittent. Where mechanical items either work or break, electrical/electronic/software items can easily show intermittent behavior. IE, upset, working again, upset, working again, etc. For MU5735, the FR24 data does show a severe upset, a temporary recovery and again a severe upset, suggesting an intermittent issue with the aircraft.

Of course, FR24 data is not perfect, though it was good enough to determine on PP, what potentially happened with SJ182.

[Sailvi767]

I posted a paragraph from a Chinese site discussing the crew. Everything was deleted for reasons I don’t know.






It was deleted because you started your post with: I don’t place much validity to the following info but it was translated from a Chinese site. I suspect it can be debunked quite quickly by the China hands on here
Not only a negative post, but already discussed in earlier contributions.

Senior Pilot

[Magplug]

With the report that wreckage has been found 8km away reinforces the observation that the airframe breakup was at medium to high level. The multiple negative results of explosives residue negates any suggestion of a bomb.

On the one hand the Chinese are being uncharacteristically open with their press conferences but may still be guarded in their admissions of the possibility of a mid-air collision with an errant mil-jet. Everything outside of airways in China is mil-controlled. Consequently getting co-ordination for wx avoidance is downright impossible. Equally an errant military jet may have infringed civil airspace resulting in a mid-air, survivable for one party but not the other. Without some force-majeure intervening towards the end of a perfectly stable cruise, the likelihood of the tail simply falling off seems very unlikely indeed.