It's been a while now but I seem to remember a speed restriction for max speedbrake on some of our -700s that had been retrofitted with winglets, but not on all of them.

In mixed fleets it's alway important to know if a 700 is referred to as a hard wing or soft wing. Slang but effective differential especially for emergency descents. Learned that flying BBJ's where all airframes were wingletted.

Rob

IIRC, all the purpose built 737-700 BBJs had the 737-800 wing (for higher gross weight/more fuel for longer range). I suspect that's what would be the 'hard wing'. If someone converted a regular 737-700 into a BBJ, then it would still have the normal -700 wing.

The preliminary report is out, referenced here: 关于“3•21”东航MU5735航空器飞行事故调查初步报告的情况通报 (variflight.com)

To my understanding, it does not discuss any causes at the moment, only declares the established facts that were debated here in much detail.

useful online translators:
百度翻译-200种语言互译、沟通全世界！ (baidu.com)
https://translate.google.com/
https://www.deepl.com/translator
https://www.bing.com/translator

Be vigilant, sometimes the negative "not" can go missing without a warning.

???3?21???MU5735??????????????????

Use Google Chrome to get a passable translation into English.

Most interesting parts

- The trailing edge of the right wingtip winglet was found approximately 12 kilometres from the main impact point. There were traces of fire in the forest vegetation at the scene of the accident. Major wreckage including horizontal stabilizer, vertical tail, rudder, left and right engines, left and right wings, fuselage parts, landing gear and cockpit parts were found at the scene

- the qualifications of the flight crew, cabin crew and maintenance release personnel meet the requirements; the airworthiness certificate of the aircraft in the accident is valid; There is no fault report and no fault reservation before the flight and short-term parking on the same day; there is no cargo declared as dangerous goods on the plane; the navigation and monitoring facilities and equipment along the route involved in this flight are not abnormal, and there is no dangerous weather forecast

-the radio communication and control command between the crew and the air traffic control department were not abnormal, and the last normal land-air call was at 14:16; the two recorders on the aircraft were severely damaged due to the impact, and the data restoration and analysis work is still in progress .

"No anomalies before they left the cruising altitude". How about afterwards? And how about showing the FDR readings?

From Tokyo Geoff's link, the announcement on CAAC website (not the report itself though)

Google translate version
 

On March 21, 2022, the Boeing 737-800 B-1791 of China Eastern Airlines Yunnan Co., Ltd. was carrying out the MU5735 Kunming-Guangzhou flight. When cruising in the Guangzhou control area, the cruising altitude of the self-route dropped rapidly from 8900 meters, and finally crashed in Guangxi Near Mocong Village, Conan Town, Teng County, Wuzhou City, Zhuang Autonomous Region. The plane disintegrated after hitting the ground, killing all 123 passengers and 9 crew members on board.
According to the provisions of the "Convention on International Civil Aviation", within 30 days from the date of the accident, the investigating organization country must send the investigation preliminary report to ICAO and participating countries. and conclusions. At present, the "3.21" China Eastern Airlines MU5735 Aircraft Flight Accident Investigation Preliminary Report has been completed, and the report mainly includes factual information such as flight history, crew and maintenance personnel, airworthiness maintenance, and wreckage distribution. The main situations are as follows:
The aircraft took off from Runway 21 of Kunming Changshui Airport at 13:16 Beijing time, rose to a cruising altitude of 8900 meters at 13:27, entered the Guangzhou control area along the A599 route at 14:17, and at 14:20:55 Guangzhou area control radar showed a "deviation" Command altitude" warning, the aircraft left the cruise altitude, the controller called the crew immediately, but received no reply. At 14:21:40, the last recorded aircraft information by the radar was: standard pressure altitude of 3380 meters, ground speed of 1010 km/h, and heading of 117 degrees. Subsequently, the radar signal disappeared.
The accident scene is located in a valley running from southeast to northwest near Mocong Village, Conan Town, Teng County, Wuzhou City, Guangxi Zhuang Autonomous Region. A puddle with an area of ​​about 45 square meters and a depth of 2.7 meters can be seen at the scene, which is determined to be the main impact point, located at 23°19′25.52″ north latitude and 111°06′44.30″ east longitude. The debris of the aircraft wreckage was mainly found on the ground and underground in the azimuth range from 0° to 150° of the impact point. The trailing edge of the right wingtip winglet was found approximately 12 kilometers from the main impact point. There were traces of fire in the forest vegetation at the scene of the accident. Major wreckage including horizontal stabilizer, vertical tail, rudder, left and right engines, left and right wings, fuselage parts, landing gear and cockpit parts were found at the scene. After all the wreckage was searched and collected from the scene, it was uniformly transported to a special warehouse for cleaning and identification, and placed according to the actual size and position of the aircraft, which was convenient for subsequent inspection and analysis.
After investigation
1. The qualifications of the flight crew, cabin crew and maintenance and release personnel on duty meet the requirements;
2. The airworthiness certificate of the aircraft in the accident is valid, the last A inspection (31A) and the last C inspection (3C) of the aircraft did not exceed the inspection time limit specified in the maintenance plan, and there was no fault report before the flight and short-term parking on the same day, and no fault reservation;
3. There are no goods declared as dangerous goods on board;
4. There is no abnormality in the navigation and monitoring facilities and equipment along the route involved in this flight, and there is no dangerous weather forecast;
5. Before deviating from the cruising altitude, the radio communication and control command between the crew and the air traffic control department were not abnormal. The last normal land-air call was at 14:16; the two recorders on the aircraft were severely damaged due to the impact, and the data was restored and Analysis work is still in progress.
In the follow-up, the technical investigation team will continue to carry out in-depth investigations such as wreck identification, classification and inspection, flight data analysis, and necessary experimental verification in accordance with relevant procedures, and scientifically and rigorously identify the cause of the accident.

end of translation

—/—
So a factual preliminary report as might be expected according to SOP.

Pity if they don’t publish an English version, that would limit translation errors, as pointed out above. Every languages has its specific complexities and ordinary and technical language in cases like these add to that.

No early AD’s or other statements.
At this stage, as you would expect, using a 2D layout for reference.
Damage to the recorders appears more severe than expected. IIRC one was found on the surface and the other about 2 m deep, the ‘can’ memory containers seemed quite good but had folded edges at one side, so maybe water entered the cans.

Perhaps this is the only concrete information that the Chinese have so far, derived only from radar observations of the flight and the FDR and CVR have not been read (or able to be read) so far. Just speculation on my part.

I presume the issue must have been that the affected -800s were already built with the provisioned wing, while the -700s were the pre-modification unprovisioned wings. According to the winglet manufacturer 300 man-hours needed for a provisioned wing, 850-1200 for an unprovisioned wing.

Well, we'll see what "restored" really means.

Interesting terminology (with allowances for Google auto-translate).

The phrase "deviation command altitude" sounds like a reference to Selected Altitude - a parameter that is increasingly available to ATC in many (most?) parts of the world via Mode S/EHS, intended to allow controllers to pick up discrepancies between selected FL and cleared FL.

I think this is just a translation issue, commanded should be understood as cleared. In China (and ex-USSR, etc.) ATC "commands" a/c to do this or that.

Winglets are highly susceptible to flutter. A 737-800 at cruise is already near VNE. A pushover would quickly result in putting the winglets into the flutter zone and separation from the aircraft. Flutter is primarily a TAS issue and it doesn’t take much speed increase at altitude to exceed VNE. Most aircraft with retrofit winglets have their VNE reduced for this reason. With high altitude winds the distance is very plausible.

A useful point and something that I get the impression is rarely understood (having had to intervene from the back seat as a passenger in a light twin when the pilot decided to do a descent at VNE into Phoenix with a 45C OAT).

the pilot decided to do a descent at VNE

Why on earth would anyone want to do a VNE descent ?

China Daily Report 20 April 2022
 

Headline: "No abnormalities yet discovered..."

"According to information disclosed by the CAAC, the exterior of the flight recorder was seriously damaged and the storage units also had a certain degree of damage. But the device remained in relatively good shape.

"It takes time to decode the flight recorder. If the storage units were damaged, it may take longer. After decoding the device, it will provide strong evidence as to the cause of the accident," said Zhu Tao, head of aviation safety for the CAAC, at an earlier news conference."

Concur, with caveat. The winglet (in fact all winglets) reduces the flutter boundary of a wing. The B737 took additional mass addition and stiffening in order to get a stable Nyquist plot of the system to a perturbation. The chance that there was a problem with the winglet that caused the upset is remote, the flutter of a winglet is much more likely to be a resultant symptom of an overspeed of the aircraft in an upset, or an overspeed by some other unknown cause. The plane jane wing doesn't have any particular issue with flutter. The older wings of the stumpy classics are not bad at all. Any wing if pushed enough will have an aeroelastic issue at some point. One B734 splash showed that the abuse of the boundary of the design was so severe that there was evidence of roll control reversal, which was adding to the disastrous condition the drivers got themselves into. On the day of this accident, there was some isolated buildups in a line E-W around Guangzhou- Xiamen, and there was moderate jetstreams to the north by recollection. Flutter often gives an interstitial tear failure in a composite when it finally lets loose, which was what the winglet looked like having from the start.

AFAICS, there are not any obvious situations that come to mind that a winglet that would cause a flutter event within the normal envelope of the aircraft, assuming the structure did not have a history for structural damage and a poorly conducted repair...

Caveat: The effect of a winglet is well established as far as aeroelastic effects go. TBC was aware of the effect on the early wing structure as was APB, and the structure was amended to restore the boundary to a reasonable margin. The approved envelope was also amended (by memory, a while ago) and TBC had separately published a pretty good AERO article on the subject. The aircraft meets the certification requirements and the operational boundary was set as a result. There is no "safety" issue related to having winglets that are correctly designed and certified. That flutter likely occurred indicates that the envelope was either exceeded severely, or the structure had an issue that lowered the flutter boundary, which would be something like undetected damage or am inadequate repair of known damage.


Boeing AERO 17 BLENDED WINGLETS

Apologies if this has already been cited, but Xinhua (the official Chinese State Press Agency) has put out a press release that I believe is an accurate and complete English-language version of the Mandarin-only Prelimary Report.

Press release - https://english.news.cn/20220420/b3e...4da45dc/c.html

Original Mandarin CAAC Prelim Report - http://www.caac.gov.cn/XXGK/XXGK/TZT...20_212895.html

Nothing added - but better than Google Translate, I think!

Interesting, the horizontal stabiliser is not mentioned.

On AvHerald it is....

On Apr 20th 2022 the CAAC released a statement indicating, the preliminary report has been submitted to ICAO. The data restoration of the data of CVR and FDR is still in progress. The aircraft left assigned cruise altitude of 8900 meters at 14:20:55L. At 14:21:40L radar recorded the last position at 3380 meters altitude, speed over ground at 1010 kph at a heading of 117 degrees, the radar signal was lost at that point. The main wreckage was found in a puddle of 45 square meters and a depth of 2.7 meters at position N23.3238 E111.1123 and included horizontal stabilier, vertical tail, left and right engines, left and right wings, fuselage parts, cockpit parts as well as landing gear. Those recovered parts were transported to a warehouse for further analysis. Traces of fire were in the forest surrounding the crash site. The trailing edge of the right winglet was recovered about 12km from the main impact site. Flight and Cabin Crew qualification and certification was without flaw, the aircraft was airworthy with no deferred entries in the tech log, there was no hazardeous cargo on board. Ground based navigation facilities all operated normally, no dangerous weather was forecast for the area when the aircraft departed its cruising altitude. Radio communication with the aircraft was normal until 14:16L (the last radio communication).

This looks the same as post 437. Which is a press release not the report itself, which is said to be 'sent to ICAO'.
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Apologies - it is indeed the press release concerning the report sent - as per regs - to ICAO. Though the prerss release does contain a summary of findings so far, there's no obligation for the Chinese to publish the actual submitted report, and ICAO can only do so if the submitting power asks.

It is a tad odd that the Madarin and English press release summaries of the report have some small but significant differences (which I had not spotted!). My sense of course would be that the Mandarin is the better version, and the AV Herald summary of the that report is (so far as I can tell) pretty accurate as to its contents. Either the "official" English version is simply slightly incorrect (which, even in China, is not unknown!) or we must await news of any significance in the differences.

@gearlever - “Interesting, the horizontal stabiliser is not mentioned. On AvHerald it is....”

Finding the horizontal stabiliser was reported, first by journalists on-site and then by officials involved in the investigation, from early on and repeated since.

For the impact that occurred here, it is not surprising that the horizontal stab was identified in the wreckage. It will have less fragmentation than the forward parts of the aircraft. The wings would have substantial fragmentation, but inner span sections of the spar will be identifiable, The engine cores (shafts, gears, not necessarily aux cases) actuators, control, gear, flap drives etc, would be usually in identifiable components, the further back in the structure the less fragmentation of associated quadrants/cranks etc.

The presence of the stabilizer doesn't rule out some control issues, but it still remains a remote possibility for initiating events. Had parts of the stab been found 12km away it would be a point of interest, but absent that it is not indicative of cause. Even if found 12km away, the failure mode would be of significance, as would be the trajectory analysis of the part to determine when it would have separated. Controls are not indicating a factor as yet other than the obvious fact that the plane didn't get to its destination, so presumably, at some point, the flight path was not as desired, or not.

I don't know what was the cause of the accident. What I DO know is the Chineses already know the cause of the accident, for two reasons:

1.I flew 10 years in China until the pandemic came, and, I know that all airplanes in China continually download both CVR and FDR through out the flight and send it to the cloud. They then keep it for 3 month. So, the bulls..t that the "black boxes"are severely damaged is just an excuse to not spread the real causes of this accident.
I had a small incident during the taxi departing for an 8 hour flight. By the time I landed (8 hours afterwards) they already had both fdr and cvr data in hands.

2. IF they had any doubt it was a plane failure , they would never have put the 738 back in service again.

Assuming that's true, why don't all airlines/countries do that? It would avoid some of the recent situations where there was fear that a recorder might not be found following an accident.

Do all the Boeings and Airbuses flying in China have custom modifications that allow them to stream CVR/FDR data?

All this conspiracy about the Chinese release of the FDR/CVR findings when both are in Washington (have been for weeks) being analysed by the US. As for streamed CVR/FDR, yeah good one.... pretty good evidence that you may have no idea what FOQA /FDM or ACARS is.

After the MAS disappearance which has become a bit of a 'landing on the moon' conspiracy event in E Asia, PRC implemented 4D/15 mandate.
4D is the position and 15 min s the maximum or target reporting latency. For the 737 class and above, sure all B-reg have it, national security matters. Airborne connectivity is not a problem, definitely not on widebodies.

QCVR is also a fact since around 2019 at the latest. During the various Safety Warfare Weeks (=bonus punishment periods) the culprits breaching sterile flight deck with chatter would be named and shamed with an internal memo, for instance.

Wireless QARs (LTE modems) have been the standard on Airbii for at least 10 years. The units I was familiar then with had 3 SIM card slots BTW.

The story above may have a more trivial explanation if the taxi mixup was in China. Viewed as a breach of an ATC command this lands the pilot in very hot water. It's not beyond imagination the report from ATC reached the company and the 8 hours of elapsed time was used to plan exactly what to do. After landing the standard LTE WQAR+CVR sent the data to the mothership and decision was reached swiftly, especially with a foreigner pilot to blame.. ATC supplying their audio inside the given time frame is also very feasible.


Having said that, linking the DMU to the SATCOM communication channel does only need technology that is presently available. Pulling larger data on request can also be done, on top of the regular 4D/15. Still, indicriminate streaming broadcast is not realistic, from my point of view. This comes back to the crash discussed, data is in the US and the rest ADS-B is public domain. Probably nothing in between.

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The incident I had was in Australia. Australia authorities called the company during the flight and when I landed in China 8 hours afterwards , the quality control already had the transcription of the CVR. THE DAY AFTER,I was there listening to my voice and the FO's. Just reminding that according to the manual, the CVR records the last 120 minutes. Not in China. In this case it was good, because thanks to that, I was considered not guilty :)

Thanks for the details, one piece of info actually is a bit of a surprise.

Not about technology though.

I checked a couple local news sources, it seems that at least some Chinese airlines have started to use a system called "X-CVR", which can record up to 8000hrs of cockpit voice recordings with "quality higher than MP3".
It has also been suggested that the so-called X-CVR system supports downloading the recordings directly to USB drive, and can even transmit the recordings via 3G/4G wireless network automatically to specific servers.
Reports say Hainan Airlines has started to fit its 737 and A320 fleets with X-CVR as early as 2018. So it looks like such technology already exists in China, although it's unclear whether MU has started to fit their 737s with the system.

We've already been told that all Chinese airlines are already continuously streaming FDR and CVR data - is that not the case ?

Regardless of once or twice, it is not the case. :-) And the anecdotal evidence has a technological explanation without broadcast streaming....

Mobile networks system are dimensioned and designed to provide maximum coverage and capacity on land, not in the air. The antenna are orientated at an angle downwards. (Not necessarily the physical antenna, that might be vertical, but it will transmit downward).

At a typical cruising altitude you won’t have any coverage. Even at much lower cruising altitudes, the coverage would be patchy and handovers (when you move from one cell to the next) can be troublesome. So I doubt 3G/4G or any G for that matter has the capability to provide continues streaming capabilities for planes. It doesn’t do so, when I fly my little single prop planes at much lower altitudes.

Jeroen

just thinking …

If you record while airborne and store while airborne, then you could start to transfer that data from a position that puts you in reach of the ground station.

From the ground station you can then distribute it over higher volume networks.

That would make it possible to have data for analysis before the plane arrives at the gate.

So precise language is needed here … is it continuous any altitude air to ground streaming… or batch/burst when in reach…

the functionality is similar but the performance quite different… bandwidth and range …

the crash area is quite remote and rough by the way and even the SAR had Comms issues …
so even a working batch system would have had coverage issues,

Not streamed, but easily downloadable by 4G as soon as the aircraft is on the ground:
QACVR Solution-DONICA

It’s little wonder that China has a reputation as a ‘surveillance State’. 🙄

Perhaps in-flight 4G is also possible:
IN-FLIGHT BROADBAND REACHES NEW HIGHS WITH 4G SOLUTION FROM THALES

DONICA stuff : very interesting , especially this part :
Totally against the spirit of ICAO incident investigations . and if I read correctly it goes far beyond 3 hours and the CB cannot be pulled on that one ..
I guess the video camera will be next..

Absolutely. Too easily abused, especially in that country.

I wonder what their unions had to say about it. LOL 🤣

If I, as slf, can us the free wifi on QANTAS flights to send text and much larger image files then why is it difficult to send CVR and FDR info back to base?

I think there are two major reasons. First, there simply isn't enough bandwidth available using 'traditional' systems such as VHF datalink and SATCOM. CVRs and FDRs generate a huge volume of data and when you multiply that by the large number of aircraft that might be airborne in the same area at the same time, the available bandwidth isn't sufficient to reliably support data streaming. Second, is cost. Data streaming is expensive and nobody's been able to justify the extra cost on safety grounds. That said, technology is constantly changing and there will no doubt come a time when streaming of CVR and FDR becomes feasible. Mind you, international regulatory change normally take years so it will no doubt be a long time before data streaming becomes the 'norm'.