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

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.

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/3764...ml#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.

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.

Fair and valid comment! I do agree.

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/...und-10km-away/

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.

Second black box found

https://www.channelnewsasia.com/asia...-found-2589126

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.

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:
Not only a negative post, but already discussed in earlier contributions.

Senior Pilot

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.

Using the granular data from this accident in a software that allows for a 3D view of the data points in position and altitude we can se things that we can not when just looking at the table.

This aircraft started the departure from stable flight with a roll to the left, and this roll got more and more like a barrel roll from about inverted. Probably due to a about 1G postitive load during the roll.
The aircraft seem to have performed at least one complete roll, completed about when the aircraft briefly gained altitude again. There is a possibility that the aircraft continued to roll after the first barrel roll.

Sriwijaya 182 had a A/T failure that put #1 Engine to idle. It made a similar left barrel roll.

Maybe something similar A/T or engine failure or a rudder hardover( I know they aren't supposed to happen these days but…)

I have had a catastrophic engine failure in cruise flight in a 767-300 ER. Instant loss of all thrust. In cruise flight it’s actually a very benign maneuver. You would have to be dead asleep to let it rollover. It’s also unlikely a rudder hard over would cause a upset as rudder travel is limited by dynamic pressure at cruise speeds. Rudder hardcovers normally are a problem at low speeds where full throw is available.

Correct. The accidents after the rudder hard over with the 737 happened at rather low speed during the approach. At higher speeds there is enough aileron authority to overcome the rolling moment caused by the rudder. One of the "fixes" was to apply higher speeds for flaps 1-10 to avoid the speed envelope where a hard over could not be counteracted by the ailerons (called crossover speed).

There were also some incidents with the rudder PCU that happened in cruise flight. They were recoverable.

That's very true... Under normal conditions and presuming the RTL performs as expected. Look at the the 747 lower rudder valves malfunctions that have occurred and you will see that is not always the case. The rudder may travel beyond the RTL limits resulting in LOC.

The 737's trim does make a very noticeable clatter when running. But if there is also cacophony of alerts, plus a stick shaker simultaneously making noises and distracting the pilots from listening to trim wheels, I'm not sure we can count on trim system noise to provide sufficient a human factors warning when things are off nominal. The trim brake is another issue.... So many unknowns at this time. Anxiously awaiting for actionable FDR data....

[pax] I think any proposed cause has to account for the timing of the event ie at or about start of descent. A random occurrence, eg collision or mechanical failure could otherwise have occurred with equal probability at any earlier time in the cruise. More likely to be associated with a circumstance specific to that phase of flight surely.

I don't agree. That is making an assumption it was changing from cruise to descent at that point and something in that process went catastrophically. It could be a multitude of reasons this flight went horribly wrong. Probabilities are fortunately something the investigation team will ignore unless it backs up FACT. If the recorders are readable, they will give a far better insight than any assumptions can.

Could this be similar to Southwest B737-700 flight 1380 in 2018 whose incident report can be found at https://data.ntsb.gov/carol-repgen/a...ort/93897/pdf? https://en.wikipedia.org/wiki/Southw...es_Flight_1380

Uncontained engine failure with a sudden left roll of a 41° bank angle leading to decompression of the aircraft, emergency descent and damage to, amongst other parts of the aircraft, wing tip and horizontal stabilizer?

I made an argument the left roll (there can be no doubt that a left roll was the start of the flight path deviation) could most likely be caused by either an uncommanded rudder movement or an engine malfunction causing the left engine to lose thrust and taking the crew by surprice. ie crew not taking action before AP disconnect in an out of trim state. Alternatively an uncontained engine failure also damaging rudder cables/controls and/or wing surfaces.
However that post have since been deleted by the mods.

I was surpriced by the number of cracked fan blades found acording the the report you are linking. That another fan blade could depart an 737NG engine can hardly come as a surprise, however I do not say with any certainty that an engine malfunction did actually happen in this accident, only that such a failure is one of the more likely reasons for this accident.

Dave it means that on the photo and video material that I have seen, there was only one engine visible (suprisingly - with the fan side up) next to a pool of water that they called the 'first pond', the circumference appeared quite intact, but the engine somewhat flattened. I did not observe the removal of that engine from the mud. And did not see the other engine. Indeed nobody commented on this then or later. So we dont know if it is the left or right hand engine that was found.

I did observe for example the removal of the outerwing/winglet from the deep mud, and the removal of a top of one big MLG fragment including trunnions. And observed the handling of the FDR 'can' just after it was found. The CVR can was a Honeywell.

The investigation reports things like 24,000 earlier and yesterday 33,777 pieces found in their press conferences, but does not make statements on the four corners or main components that have been found, apart from the CVR and FDR. They appear to have established a pretty thorough process chain for filtering, handling and identifying parts, so that information should be available by now. That they dont make that public may or may not be surprising.

Am guessing at least one non-Chinese party (Boeing) will take part in this investigation.
A collision may be unlikely, but suppose that were the case. The Chinese would be reluctant, putting it mildly, to admit this.
Interesting dynamics in multinational investigation team, a bit like the WHO looking into the lab-leak hypothesis.

No guesswork required. It has already been announced that the NTSB will participate in the investigation, supported by Boeing and CFM.

The future of Boeing is at stake let’s not forget that.
They’ve barely recovered from the Max debacle and a potential fleet wide problem with the -800 series could very well be the end of it.

The Chinese government and media outlets are reporting that all 132 victims have been 'identified' through DNA testing, cross-matched with samples taken from their relatives. That seems quite a tall order, given the accident only occurred a week ago and the difficulty of recovering remains from the crash site.

http://english.www.gov.cn/news/topne...3353285ed.html

Given the airframe has been around for 24 years it would be very rare if an endemic problem that causes catastrophic uncontrollable states has been lying dormant and undiscovered that whole time.

The difference with the MAX is the MCAS problems were detected at the start of the aircraft’s operational service life.

Except this airframe wasn’t 24 years old.

Changes in production methods, materials, quality control etc etc etc.
Boeing is certainly not in the clear.
The Max is still not re-certified for Commercial operations in China and they may delay even further.

If anyone thinks the Max will ever fly in China again they are dreaming.

Something the newer 737 ng have in common with 737 MAX
All 737 MAX and most 737 ng manufactured 2014 or later (I'm not sure about date) are equipped with a new model of the motor and motor driver that is used for electric trim.

There could be a difference in how the newer motor and motor driver is able to restore normal trim after a runaway trim. Compared with older motors.

The new trim motor and driver that came around 2014 is from Eaton and is called Model 6355C. Among what is new is:
– Brushless three phase motor
– Dual current limit (torque) control circuits

I have not been able to find any information about when the current limit/torque limit kicks in. The strong force required to recover from e.g. a runaway trim if the mistrim is compensated for by elevator, have been shown that it can be impossible to fix with the cockpit wheels. Even if both pilots try to, manually. Unless a maneuver like the "roller coaster maneuver" is used.

There is not so much information about Eaton Stabilizer Trim Motor 6355C available, but here is some.

Search for:
Eaton Stabilizer Trim Motor 6355C

I'm not allowed to post links.

/ywagd

That can be everyone's guess. But since the FDR and CVR data are most likely available in a few days, there is no need to speculate. I am sure the reason will come out regardless what face saving by whatever party might be involved. FDR and CVR data can be sent by email so no need for NTSB or Boeing people on site waiting for any Covid clearance.
China has grounded a lot -800 so they have some interest to figure this out.

PCR genetic analysis has come down massively in cost and time lately. I find this only mildly surprising.

Sure, but given the aircraft was pulverised by the high-speed impact, I'm surprised they've been able to find and identify DNA material from ALL of the occupants in such a short space of time.

My guess is that the hundreds of workers that have been working for days to collect everything, including parts and fragments from the plane, and body parts, soon had collected many thousands of fractions from both the plane and from victims. When 132 different DNA profiles had been found the next step was to identify the individuals. Often through DNA from relatives.

I read that headline and am in disbelief.... to isolate 132 individual DNA in that wreckage...especially the souls in the back of the plane who probably ended up far down the hole. I can't fathom how they could do this.

Also given the high surveillance in China, probably all were scanned on a/c entry by various biometric devices and they knew everything irrespective of the manifest. Likely have the DNA on record of all the passengers as well. Probably the most intrusive place in the world so not surprising I agree.

Not to get too morbidly graphic, but do you think the souls in the front of the plane fared better than the ones in the back?

The point was those in back of plane would end up far into hole, and harder to access/isolate their DNA, vs those in the front, as the impact would scatter on the surface, this notion further makes me doubt their claim of identifying 132 distinct DNA.

Based on what I have seen the aircraft is fragmented and the fragments are bent and torn with no sign of fire on them (there was a fire in the trees above the crash site, so apparently some fuel has been thrown forward and up).The largest pieces are parts (top and or bottom panel fragments) of the wing(s) which are a few meters long and say half to one meter wide. One of the engines (bare engine only, no cowlings) was easily identifiable, the other may have been found too as there are two stacks of engine components. Another parts seems to be a part of the THS and another part of the wing. Both are a few meters long, but can be carried by say 6-7 guys. Until now I have only seen one piece of wiring of about 20cm long. No instruments shown at all, but reported that manuals from the cockpit had been recovered. Next to that many white bins with fragments.

In one of the early press conferences they mentioned that all the passengers were Chinese nationals. So there was no need to go into the more lengthy process of asking foreigners to come forward. Based on this you might say that there is a difference in identification time between an all nationals flight and a flight with a mix of (inter-)national passengers.
China makes extensive use of facial recognition, a BBC video showed they could find a reporter in Shanghai or similar within 7 minutes, so they might have used that to take a look at images at the airport to confirm who actually entered the aircraft. On the first day they mentioned one more passenger than thereafter.
Many countries have identification processes in place these days to enable quick identification. The area was hot (30C) and very humid (heavy rain for days), so they had to work fast.

During the weekend the investigation and authorities declared all PoB deceased. From that point on they start making more use of heavy machinery and are building and widening roads to support the recovery effort. The continuous rain has made this a big effort.

FWIW: Given how they used to identify people in this scenario prior to DNA, it would definitely seem plausible with todays DNA/computer technology to ID their remains much quicker and probably with better accuracy. The human body doesn't simply vaporize on impact.

No, it doesn't vaporize, but it is organic and burns and is consumed. I simply do not believe they identified all 132, and no less before they found the second black box. Maybe I am wrong, and maybe they had a big group focused on just DNA sampling. I saw the images of the fires and the heavy rains, and such and just don't believe the claim.