China Eastern 737-800 MU5735 accident March 2022

[FlightDetent]

Originally Posted by jewitts

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]

Originally Posted by 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...

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

[tdracer]

Originally Posted by Capt Kremin

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]

Originally Posted by Capt Kremin

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

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]

I flew in China for ten years

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]

Originally Posted by A-3TWENTY

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]

Originally Posted by A-3TWENTY

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/poli...ox-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]

Originally Posted by A-3TWENTY

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]

Originally Posted by tupungato

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]

Data recorder found

“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/poli...ox-found-plane

[MikeSnow]

Originally Posted by TwoHeadedTroll

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.