Many have probably heard about China Eastern Airlines Flight MU5735 that crashed near Wuzhou, China on March 21, 2022. Something caused the plane to enter a steep dive while the flight was straight and level at its cruising altitude and impact the ground minutes later. Airplane accidents are extremely rare events, and it is extremely rare for an accident to happen in this way. This post reports what is currently known about the accident and discusses possible causes.
Flgihtradar24 has disseminated much information about the flight. Flightradar24 is a Swedish company that continually collects Automatic Dependent Surveillance–Broadcast (ADS–B) data in real time about airline flights world wide. ADS-B has replaced radar as the primary tool used by air traffic control tool for tracking commercial airliners.
China Eastern Flight MU5735
China Eastern Airlines (MU) flight 5735 was scheduled to depart Kunming at 13:10 local time (05:10 UTC) and arrive in Guangzhou at 15:05 local time (07:05 UTC). (UTC refers to Universal Coordinated Time which was previously known as Greenwich Mean Time.) The flight was operated by a Boeing 737-800. This model is different than the 737MAX and is not equipped with the MCAS system that was determined to be the primary cause of two 737MAX crashes a couple of years ago.
The flight crew was very experienced. The captain had almost 7,000 flying hours, while the first officer had more than 31,000 hours of experience. A third pilot was on board as an observer and had 556 flying hours.
MU5735 departed Kunming at 05:16 UTC and reached a cruising altitude of 29,100′ 11 minutes later. The flight continued normally until 06:20 UTC when the aircraft began a rapid descent to 7425 ft amsl (above mean sea level) before recovering to 8600′ amsl. At which point the aircraft entered another steep dive. The last ADS-B message was at 06:22:35 UTC at an altitude of 3225′ amsl.
Flightradar24 prepared this graph depicting the final 150 seconds of ADS-B data on altitude, ground speed and vertical speed.
This information is illustrated below.
After a normal flight, MU5735 suddenly and rapidly descended and crashed within a span of about two minutes.
Possible Causes
The cause is undetermined at this time. There are, however, clues about what may or may not have happened. I’m not an airline pilot. This analysis relies on knowledge of other airline accidents and my private pilot training and experience.
Aerodynamic Stall
The airspeed (speed of the plane relative to the air through which it is moving) has not been publicly available although the airspeed can be presumed to have been relatively constant because of the constant groundspeed (the horizontal speed of an aircraft relative to the Earth’s surface). If airspeed was constant, that rules out loss of lift from an aerodynamic stall as the cause of the initial dive.
It is possible that the plane could have lost enough airspeed during the recovery from the initial dive at about 8500′ amsl and 5,000′ agl (above ground level) to enter a stall. Pulling the nose up to stop the initial rapid descent and establish a positive rate of climb would certainly reduce airspeed. A stall might explain the second rapid descent. If the aircraft stalled at an altitude only 5,000′ above the terrain, recovery would be more challenging but not impossible by any means.
Engine Failure
Engine failure is an unlikely cause of the crash even in the unlikely event of a simultaneous double engine failure. From 29,000′ the pilots could have maintained a slight nose-down attitude and glided for a great distance. Engine failure would not explain the second dive either.
Inflight Break Up
In extremely rare cases, planes have broken apart in midair for various reasons including metal fatigue. A strip of metal that may have come from the plane was found 10 km from the crash site. The final descent and impact was recorded on a security camera at a nearby industrial site. The plane appears to be intact.
Elevator Malfunction
Steep dives might indicate a problem with the elevator, the flight-control surface on the tail that raises and and lowers the nose. If a problem with the elevator or its trim control caused the first dive, that problem must have been fixed, at least temporarily, because the plane pulled out of the initial dive at about 7,500′ AMSL.
Intentional Act
A pilot intentionally crashing a plane has happened only a handful of times in the history of commercial aviation. The most recent known example is Germanwings Flight 9525 in 2015 where a pilot crashed an Airbus A320 into the French Alps. At this point, an intentional act by the pilots or someone else on board cannot be ruled out.
Radio communication with the aircraft was normal during the flight. But there were no radio calls from the aircraft, and the pilots did not respond to calls from air traffic control during the incident. The lack of communication from the flight deck might be evidence of an intentional act by someone.
The possibility of sabotage of equipment or systems can’t be ruled out either at this point.
Status of the Investigation
Information from the flight data recorder (FDR) and cockpit voice recorder (CVR) will be crucial in determining what caused this crash. The CVR has been recovered. It has been taken to Beijing where it is being examined. The FDR should be found soon. The information from the FDR will shed light on any mechanical problems the aircraft experienced.
Chinese investigators have invited representatives from the U.S. National Transportation Safety Board (NTSB) to join the investigation because the plane was manufactured in the U.S. It may take them a couple of weeks to take part because of Chinese quarantine requirements.
Participation of the NTSB may alleviate concerns over transparency in the investigation. In a few instances, countries have gone to great lengths to avoid assigning any blame for crashes to their own pilots.
Final Thoughts
Airline travel is the safest form of travel and commercial airlines are the safest form of air travel. This commercial airline accident is the first one in China since 2010. The 737-800 is one of the most widely used airliners and has compiled an outstanding safety record.
China Eastern is a decent airline although it has some customer service problems. I’ve flown on China Eastern 737-800s several times. I’d do so again without hesitation except I’m now reluctant to visit or transit through the People’s Republic for reason unrelated to aviation safety.
If there was an intentional act by anyone on board, that should be identified by the CVR rather quickly. Otherwise, identifying the cause may take quite some time. In either case, the release of an official accident report will take months.
Do you have thoughts or questions about MU5735? Don’t let this unfortunate incident deter your travel plans.
the day after they were talking on the radio about it and thoughts were definitely that it might have been a deliberate act, possibly by the pilot. it’s such a steep descent it must have been a terrifying way to go. I dont know if the steep descent would have rendered people unconscious, but probably better if it had. Never flown china eastern, i have flown China Southern and it was a basic experience for an international flight but not the worst either. I’ve also flown Spring Airlines, a local budget carrier dont know if they still exist but i didnt enjoy air travel in China, it’s really packed and busy and well, it is what it is because of the demand.
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It appears that the MU5735 CVR may be damaged and require some repairs. Assuming the info is recovered, it should answer the question about an intentional act. I like China Southern. Through a bit of a quirk in the rules, I’ve been able to use Delta SkyMiles to get a taste of China Sothern’s international first class product on the A380 and B777-300 on domestic flights in China.😃
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Some interesting insight here John. As you say air travel is, on the whole, super safe. But how terrifying these disasters are, especially to someone like me who is a bit nervy in general with flying.
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Thanks for sharing your views Leighton. Although it may take sometime, the cause will be uncovered. Having some anxiety is understandable. I used to be nervous about flying myself.
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Thanks so much for such a great informative description John.
Maybe it’s just be but I’ve been thinking intentional all along..
Maybe it’s it’s just everything we’re going through.. IDK.
💖🌻🙏🌈
“The lack of communication from the flight deck might be evidence of an intentional act by someone.”
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Great that you’re thinking of some international travel, Cindy! The good news is crashes are incredibly rare because so much effort is devoted to safety. The results of this investigation will make things even safer in the future. Be well and safe 🧡😊
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Wait.. did I say that?
Ha!
I said I think it was intentional with no merit to that.
But you’re
So right John!
The same way surfing is safer than most sports is the same way that flying is safer than most transportation.
Never stopped me tho from crying at the dye of the beach worrying while my son surfed!
🙏☺️😱
Most of the time it’s totally safe and then I just do happen to know Thais that have had catastrophic injuries. He was surfing the LA waves 🌊 today. 💕🙏♥️
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I admire surfers and like to snorkel and scuba dive. For some reason surfing scares me not knowing what is under the surface. Intentional international travel is the way to go.🤣
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I often forget that planes are so much safer than cars, trains, boats, etc. yet everyone is most terrified of planes crashing. Hope they can figure out the cause of the crash quickly, I’m sure it will help bring a tiny bit of closure to the victims families.
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I have a fear of crashing. Flying is no problem. There could be many possible causes for the MU5735 crash. It will take a little time but we should no the real cause eventually. Thanks for your comments, Lyssy!
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A detailed and very interesting analysis. I saw the news coverage of the crash in the immediate aftermath but haven’t seen anything since – perhaps because there’s nothing to report until the investigation concludes but also because something else is understandably dominating our news broadcasts right now.
No, this won’t put me off flying any more than any previous crash has done. I know it’s incredibly safe, on the whole, and I enjoy it 🙂 I used to tell my mother, who flatly refused to fly and had a love of donkeys, that more people were killed by donkeys than in plane crashes. I don’t know if that’s true but it wouldn’t surprise me!
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Ha ha! I don’t know about donkeys but in America the most deadly animal for humans is a deer (auto accidents) and in Africa the mosquito is the deadliest (malaria). It turns out that the CVR is damaged and seems to need repairs. We’ll wait a while for that info to be made public.
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After hearing about this accident, I went to the “Mentour Pilot” website. He’s a 737 Captain and instructor. He has plenty of background to analyze such situations. His page has a good summary of his thoughts regarding the disaster.
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Thanks for the info on Mentour Pilot. It notes that the CVR memory chip is damaged and needs repair. We’ll wait a bit longer for the clues it holds to be revealed.
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So sorry to hear about this plane crash, I didn’t know anything about it. The circumstances are certainly strange plus generally with plane crashes is always quite difficult to know for sure what caused the plane to crash. Let’s hope there is more information available soon, but for the time being your post really helps to get a more clear idea of the possible causes.
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Thanks for reading Blanca. This accident is highly unusual. I hope the investigation isn’t tainted by political issues. I’ll post about the findings when they come out.
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This will be great, I´ll stay tuned!
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The CVR memory chip was damaged and may need repairs before they can get that info. Keep up the great posts, Blanca.
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Wow I just didn’t know about this crash . We will see if this occurs ..YIKES!
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Oops! Forget I mentioned it. 😊
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thanks for this analysis. hopefully you will keep us informed as new information is released…
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I’ll keep an eye peeled for new info.
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🙂
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A very odd situation. I’m not one who grasps for conspiracy theories every time something strange happens. No, this accident will not change my travel habits. It’s far more dangerous to drive an automobile, but most people are undeterred by that.
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I understand those who aren’t impressed by the statistics. It is hard to imagine that putting people in a pressurized metal tube and hurling them through the air at .8 the speed of sound at 35,000′ is safe.
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“Airline travel is the safest form of travel and commercial airlines are the safest form of air travel.”
This is what I repeat in my head as my fear of flying takes hold whenever I’m on a plane.
“Don’t let this unfortunate incident deter your travel plans.”
OK. (That’s what whiskey is for.)
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Ha ha! A pre-departure beverage is just what the doctor ordered to relive the stress of travel and I bet it works wonders for those who are anxious about flying. Thanks for adding to the discussion.😊
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