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-   -   China Eastern 737-800 MU5735 accident March 2022 (https://www.pprune.org/rumours-news/645805-china-eastern-737-800-mu5735-accident-march-2022-a.html)

Cool banana 21st Mar 2022 18:54


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....99cc1c747b.jpg
Right Wing tip.

Let see what the investigating team comes up with.

kenparry 21st Mar 2022 18:58

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 21st Mar 2022 19:45

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 21st Mar 2022 20:02


Originally Posted by Compton3fox (Post 11203467)
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....8d4046b0fb.png

C2H5OH 21st Mar 2022 21:42

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 21st Mar 2022 22:00

Weather at crash time, sat pic, lightning
 
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

IR Sat pic

Lightning detection

tubby linton 21st Mar 2022 22:16


Originally Posted by weatherdude (Post 11203543)
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

IR Sat pic

Lightning detection

Any CAT or mountain wave forecast?

weatherdude 21st Mar 2022 22:21

300 hPa wind at the time
 
Some decent tailwind, but nothing out of the ordinary afaik

A320 Glider 21st Mar 2022 22:22


Originally Posted by tubby linton (Post 11203550)
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 21st Mar 2022 22:35


Originally Posted by 777JockeyIN (Post 11203512)
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 21st Mar 2022 22:40


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

The investigation concluded that the vertical stabiliser came off first.

clark y 21st Mar 2022 22:55

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 21st Mar 2022 23:00


Originally Posted by pattern_is_full (Post 11203561)
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 21st Mar 2022 23:12

[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....e2818dfce.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 21st Mar 2022 23:16

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 21st Mar 2022 23:37


Originally Posted by Consol (Post 11203582)
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 21st Mar 2022 23:46

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 21st Mar 2022 23:52

Let's let facts and Data rule - not idle speculation
 
- 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 22nd Mar 2022 02:35

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...=1599550692168

PAXboy 22nd Mar 2022 03:12

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.


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