At 1.08 in to the video, notice the blank panel for the window aperture on the starboard side last row of the window belt. There is some material trapped by the window blank and the fuselage skin. Has this material [possibly part of a seal] failed in the air, not impact damage. See

Rescuers recover transmitter installed near second black box. CNGT 26TH march

ywagd
If you go to the Eaton.com website and search on B737 stabilizer trim upgrade there is a sales type technical description of 6355C trim motor. Not sure what your getting at in the context of this event though.

CGTN actually reported on 26th March that the recorder itself had been found, not just the ULB.

Video shows where second black box from MU5735 was discovered - CGTN

Probably it is not of significant here.

But, if we in a few weeks from now learn that this accident started with a runaway nose down trim where the plane initially was kept from diving with elevator, then this could be of significance.

I think other scenarios are more likely, but when we get FDR data we will know more.

/ywagd

For the above to happen you would need a series of events that is hard to imagine. First the trim motor would need to begin a runaway. As soon as that happened the autopilot or pilot flying would counter that with elevator movement activating the trim brake. If the trim brake failed which would be a completely different failure from the initial runaway the pilots would need to not notice the autopilot disconnect warning, nose pitching down, change in G forces, spinning trim wheels. If any off the above was noticed the pilots would simply hit the trim disconnect switches. They would also intuitively trim counter to the runaway. Either action should stop the runaway. They could then continue the flight using manual trim. The trim brake is a robust system we checked on the first flight of the day so it’s tested often.

Yes, the left roll is quite clear.

I was not thinking ”rudder hardover” as necessarily not controllable failure.
A uncommanded rudder movement ( or A/T failure like Sriwijaya) and a A/P disconnection and spatial desorientation.

Sriwijaya 182 seems to have rolled left without noticing it, at least initially. Might be the same this time?
An uncontained engine failure could possibly damage the aircraft and cause something like this, but my guess is that if you get a uncontained engine failure you will wake up and get on your toes quite quickly…

To posters with the view that it can not be a rudder hardover/uncommanded movement or Eng failure: What would cause the aircraft to perform a left roll + second half of a barrel roll?
Any ideas?

"Dormant" may be the key word. Certainly some ex-Boeing people blew the whistle some years ago on manufacturing shortcuts that could enhance fatigue & erosion. Which would take time. Meanwhile, landing mishaps have caused the NG fuselage to break lethally into sections that some experts say represents excessive damage for the forces involved.
How "endemic" it was would depend on whether Boeing cleaned up its act when people started blowing whistles.
If so, it would still be worth following the fate of that batch of aircraft.

Most laughable paragraph I have read in awhile. Get out of the house and stop reading spy novels. No country has DNA samples of its entire population. Especially a country so populous as China. There are no “biometric devices “ scanning you on aircraft entry either. There maybe facial recognition in the terminal but that is about it. And even then it isn’t gathering data about you. But scanning you against a database.

Runaway trim... doesnt it says on the memory items not to reengage the autopilot? Could this be the case when it level off and reengaged the autopilot leading to another freefall?

But not yet because the Chinese have only just issued visas (surprise surprise). And they still have the quarantine card to play if they wish to be obstructive for a little while longer.

you are naive or misinformed about the Peoples republic. Not only do they gather their own peoples dna, they are purchasing western databases as well.

Maybe not the place to have this discussion as it is completely irrelevant to the topic.
Genotyping (even 10s of thousands) of recovered tissue samples on a forensic STR kit is trivially easy. Genotyping 300 samples from relatives is trivially easy. Statistical matching of STR profiles for identification is trivially easy. Whether you have a pre-existing database would have next to no influence on the technical process. As someone else pointed out above, the difficult bit is finding and collecting the tissue samples.

There is perhaps a slight relevance - one way of reading the official Chinese government statement on the DNA identification is that none of the expected passengers and crew were (last minute?) missing; and that no DNA other than that expected was found. Somebody on the investigating teams will have been tasked with checking those two possibilities out.....

Was just updating some notes on China. Found this one in my notes (long time ago, but a fmr sr NTSB lead says 'there are no new accidents'). An event like this was discussed as an option by some posters.

Case is 24th of November 1992, all fatal accident, 737-300 China Southern Airlines, flight CZ3943, Guangzhou-Guilin, B-2523.
I could not find a final report, but my notes say cause was reported as: "asymmetric thrust, crew failed to recognize roll condition, gave wrong control inputs,.."

I can't put my finger on the official Final Report either, but there's a decent Wiki ( https://en.wikipedia.org/wiki/China_...es_Flight_3943 ) and a useful ASN Summary ( https://aviation-safety.net/database...?id=19921124-0 ).

I think something like this could easily have been the triggering cause for the crash. Except no clutch slippage but some other reason for asymetric thrust. Or at least one of several more likely causes.

There's a fairly comprehensive summary of the investigation report here.

Even if it was, it still becomes pilot error, and not a reason to ground planes..Has occurred too many times the pilots don't notice the spinning wheel with the alerts going off..

That is incorrect. The Chinese language sources are clear on the following:

The Captain had 6k hours.

The first First Officer had 32k hours.

The 2nd First Officer had ~500 hours.

The reason for this seemingly odd crew composition was also clearly stated in the Chinese language reporting:

The 32k-hour pilot was one of the most experienced civil aviation pilot in China. He was one of the first Chinese pilots who started flight training as a civilian, rather than military. He started his career just as the Chinese civil aviation was taking off in the early 80s. He was scheduled to retire this year. The reason he had so many hours but yet was not flying as Captain was the airline had retired the 767 on which he was rated as Captain, so he was now being converted to 737.

The young 2nd First Officer was in the third seat. He was assigned to this flight in order to "gain experience." That's all the Chinese language reporting said about this pilot. No further explanation was given how sitting in the third seat could help gain experience.

The Captain was hired as a 737 captain in January, 2018. Nothing remarkable was reported about him.

CAAC promises a preliminary report within 30 days. https://www.scmp.com/news/china/poli...mpaign=3172492

Probably the worst thing you could have is a cockpit full of pilots.

Well, I think it is generally accepted that the third pilot on the Qantas A380 uncontained engine incident was extremely usefull in securing a positive outcome and bringing the aircraft safely down on a runway.

The same can be said about the third pilot in the cockpit on the first Lion Air Max incident with the MCAS runaway where also that aircraft was brought to a safe landing. Acording to reports it was input from the third pilot that possibly saved that flight.
The two other known MCAS malfunctions had only two pilots in the cockpit, and both crashed catastrophically.

Al Haynes would have staunchly disagreed with you on that one.

Interesting. CES only operated three B767s, and they left the fleet more than a decade ago (2011).

It’s possible he went to the 737 after the retirement of the 767 and was still a check Captain giving a check ride. If so nothing to see here. That would not however be the normal career path.

I'm not a pilot.

If it was a check ride, I wonder if the check captain perhaps simulated some sort of emergency which was incorrectly handled and got out of control? I am well aware that it's not SOP to practise simulated emergencies with a plane load of passengers, however.......
Just a thought to add to the many others.

There are more options, e.g. the LHS PIC needing an instructor for reasons of recency.

Yet the Chinese official media are typically correct about what they are trying to say. F/O sounds like an F/O, especially if announced on the CAAC News website (did not check myself). Link click here.

Some is easier to imagine, such as a long-time LH instructor having enough of surfing the timezones and coming back to 737 i.s.o. 777/787, some harder. How does 31k hours fit within one lifetime?

I'm curious about this number also. Over 20 years that's flying about 30 hours/week.......every week.

Starting from early 80's, that's almost 40 years. So maybe 15-20 hrs/week

It says somewhere above that he was about to retire, so how about 40 years!? :hmm:

From the deleted files:

Joined Yunnan Airilnes 1985
Received 737 at Seattle 1988
Become captain 1991
Flew the 767 for more than 10 years

A post above claims CEAir retired 767 in 2011. That's at least 4 big trainings (5 months around) plus the last 2 years of COVID.

35 years gives 888 per annum without missing one. Tough love (or?).

I can’t conceive of that happening especially in China where every flight aspect is monitored. Line checks are to observe normal operations. Emergencies are practiced in the simulator.

I watched a "Lei's Real Talk" video in which she says she has information that the "award winning" 30k+ hours 767 captain "with unparalleled safety record" moved to 737s when the 767 fleet was retired (in 2011), then was involved in an incident last year where he flew "out of a terrain warning zone at an airport" which the company recorded as a "serious safety mistake" and demoted him from Captain to First Officer following a simulator test.

You are right. When I read the original Chinese stories, I didn't check the timeline. Now that you mentioned it, I went back and read that he had already started flying 737 many years ago. It's curious he wasn't promoted to captain.

There's rumor that he was promoted, but was then demoted back to FO after an incident. But it's a rumor on social media only.

I haven't flown the B737 but have flown & taught on the A320 & other Airbussi (as well as Lockheeds, McD's & Boeings); I am familiar with the Sriwijaya accident & earlier pitch-down accidents resulting from loss of crew situational awareness where it concerns a loss of engine thrust.

A loss of thrust at cruise power would result in some yaw but not an uncontrollable yaw and certainly good control over any roll, and if engine thrust had been set for the descent, (idle thrust) and the aircraft was descending normally, (about 2000fpm or so), there would essentially be no yaw at all.

I like what fdr has had to say on the subject and I think it is wise to consider this accident from what he observes as possible. I take seriously what he says about the few causes of significant pitch-downs occurring without the crew's roll input. As he says and provides examples for, we should look elsewhere and, unless seriously mishandled, not engine failure for the source of roll & pitch-down. Whether this is similar to the China Airlines B747-SP incident or not remains to be seen.

Would a real 737 pilot care to comment on the likelihood of a thrust reverser opening in flight...?

We've had a real Boeing propulsion engineer comment on that. Who has seen the investigation of Lauda 767 from the inside.

Nope, unimaginable (my wording).

FlightDetent, you called? :)
Actually, I don't recall commenting on the TR deployment on this thread.
After Lauda, Boeing added a 'third lock' to the reverser system on all aircraft (I believe the 737 NG uses a 'sync lock' that locks the device that synchronizes the movement of the T/R actuators). It would require three independent failures - of which two are non-dispatchable faults that should result in the reverser being locked out prior to flight. There have been issues in the past with improper lockout procedures on the 737 NG (basically it was possible to insert the lockout pin without it actually engaging) - memory says Boeing issued a fix for that (which was promptly AD'ed by the feds) maybe 15 years ago.
The probability of all three faults allowing a reverser to deploy in flight is something like 10-13/hr (i.e. one in 10 trillion flight hours), and even when dispatched with a latent failure of one the locks is something like 10-8/hr. So possible, but very, very unlikely.

All that being said, the reported flight profile of this accident does have a striking resemblance to what happened to Lauda.
At the risk of being called a racist again, I'd really like to know what was done to that aircraft as it sat on the ground for the two days prior to event flight.

Just to put that into perspective, it is roughly 1 billion flight hours for every 737 ever made...

Crew make up
 

it’s a few years ago now since I trained pilots on the BAe 146 for China North West. Maybe things have changed but the F/O’s easily adapted to EFIS while the captains, ex Russian aircraft, struggled.

As the F/O’s pointed out, they were condemned to be just radio operators for the next several years before being offered a command.

There was nothing I could do to change the system. Maybe things have changed.