China Eastern 737-800 MU5735 accident March 2022
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The military have never stopped me deviating for weather in China. When ATC can’t approve your weather deviation request.
” Pan Pan, Pan Pan, Pan Pan, avoiding weather, will fly offset 30 nm miles right “
Incredibly my colleagues have said “ oh they won’t like that ! “
do I really care ?
My priority is the safety of my customers and colleagues, not the controller’s feelings who
maybe has their hands tied, with many rules.
Fortunately the throttles and flight controls are not interlinked.. With over 10K hours on the 737 including the 8oo and Max, and some training in accident investigation, I'd like to offer a few observations. First off, I dont believe it is possible to reach the ground in two minutes without the throttles pushed up. No one keeps power in , in a dive. Its instinctive for anyone thats been flying for any period of time to reduce power to idle. Now with power at idle I dont think even vertical you can descend 29K feet in two minutes. Now to get vertical, you would have to have a condition where not only are the flight controls unresponsive but they have had to go into a full nose down position by themselves, and be resisting input to reduce the angle of descent. which without some kind of assistance would not normally occur on their own. OR you would have have to a failure of the flight control system as well. So we are talking two separate events, by systems not related. except by the person flying. I could be grossly mistaken, but I dont believe you will find much data coming out of China that isn't manufactured. The airplane has been in service 7 years, so bugs have been worked out. This leaves one of several possibilites. Crew action, maintenance or some external factor.
Fortunately the throttles and flight controls are not interlinked.. With over 10K hours on the 737 including the 8oo and Max, and some training in accident investigation, I'd like to offer a few observations. First off, I dont believe it is possible to reach the ground in two minutes without the throttles pushed up. No one keeps power in , in a dive. Its instinctive for anyone thats been flying for any period of time to reduce power to idle. Now with power at idle I dont think even vertical you can descend 29K feet in two minutes. Now to get vertical, you would have to have a condition where not only are the flight controls unresponsive but they have had to go into a full nose down position by themselves, and be resisting input to reduce the angle of descent. which without some kind of assistance would not normally occur on their own. OR you would have have to a failure of the flight control system as well. So we are talking two separate events, by systems not related. except by the person flying. I could be grossly mistaken, but I dont believe you will find much data coming out of China that isn't manufactured. The airplane has been in service 7 years, so bugs have been worked out. This leaves one of several possibilites. Crew action, maintenance or some external factor.
An aircraft seven years old isn’t one that has the bugs worked out. Its one, especially if barely used in two years, that will develop the
usual litany of defects and rectifications.
27 years all variants 737 on four continents.
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29000 feet in two minutes is only about 150kts - I would have thought that would be easily achievable in a vertical dive with power off . .
Last edited by common toad; 24th Mar 2022 at 08:37.
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Unplanned descent speeds
There is a common misconception on this and other threads relating to max achievable rates of descent.
An excellent post by ‘ fdr’ explained in some detail about the aerodynamic effects of subsonic airliners exceeding their certified Mach No.
I think that post or a previous post also explained that flight simulators are not programmed to accurately simulate these situations outside the normal certified flight envelope.
If you inadvertently roll more than 90 degrees of bank in the cruise, and stay in trimmed flight there is no lift up, it’s sideways. If you manage to roll near to inverted, then all the lift of the wing will be towards the ground.
As the speed builds up rapidly, the lift also increases rapidly, accelerating you down.
If you happen to notice the unusual attitude you unload the wings and roll to the nearest horizon, and begin a smooth pullout.
If you’re still distracted, planes will normally enter a spiral descent, but if fully inverted (180 degrees of bank ) you basically start flying the second half of a loop. Without any pilot input, just from the trimmed state of the aircraft.
In these situations the engine thrust is almost irrelevant, full thrust is nowhere near the weight of the aircraft. In the cruise at altitude full thrust is maybe just above 1/20 of the aircraft weight. Airliners have a lift drag ratio of maybe 1/20. Maybe a bit better with more modern aircraft.
But you get the idea, the weight of the aircraft is significantly more than thrust from the engines.
As the plane approaches high transonic speeds , approaching Mach 1.0 you get a dramatic drag build up, Critical Mach drag rise, or whatever you wish to call it.
Airliners are bluff objects designed to fly subsonically, so this extreme drag makes going supersonic very difficult.
So generally the max rate of descent will be about Mach 1.0
As an aside, using the FlightRadar24 altitude readouts, the rate of descent corresponds to about a 1,000 ft a second. 5,000 ft lost in 5 seconds if I read the numbers correctly. Or 60,000 ft a min or 685 mph. Local speed of sound is 707 mph assuming a standard atmosphere and a temperature of -25 C.
So vertical speed M 0.97 , this is only the vertical speed using the data. As stated by previous posts the data from FR24 can be smoothed or assumed. When you allow for the horizontal ground speed to get the true airspeed and Mach No. the numbers are higher.
With previous Jet upsets when the data is pulled and all the circumstances are allowed for, the max speeds always seem to be subsonic, or mildly supersonic.
As ‘ fdr ‘ stated as you descend into thicker air it is also warmer, which means the local speed of sound increases too. So for a given speed, the aeroplanes Mach No will decrease. As you descend into warmer air you should get more control.
There are two big issues with these high speed descents.
1:you can rapidly exceed the aircrafts design max speed which can lead to structural failure.
2: you need a lot of sky to pull out of a high speed descent.
Lastly, I have read that most ‘ Jet upsets ‘ that occur in visual conditions are survived, but those in cloud or at night with a limited visual reference are not.
From my aged memory the CAL 747 that had a ‘ jet upset ‘ was only flown correctly when the crew got a visual horizon at about 20,000 ft. I note that for this unfortunate flight, the cloud base was much lower.
P.S. My credentials; I can’t spell but have flown commercially for far too long.
An excellent post by ‘ fdr’ explained in some detail about the aerodynamic effects of subsonic airliners exceeding their certified Mach No.
I think that post or a previous post also explained that flight simulators are not programmed to accurately simulate these situations outside the normal certified flight envelope.
If you inadvertently roll more than 90 degrees of bank in the cruise, and stay in trimmed flight there is no lift up, it’s sideways. If you manage to roll near to inverted, then all the lift of the wing will be towards the ground.
As the speed builds up rapidly, the lift also increases rapidly, accelerating you down.
If you happen to notice the unusual attitude you unload the wings and roll to the nearest horizon, and begin a smooth pullout.
If you’re still distracted, planes will normally enter a spiral descent, but if fully inverted (180 degrees of bank ) you basically start flying the second half of a loop. Without any pilot input, just from the trimmed state of the aircraft.
In these situations the engine thrust is almost irrelevant, full thrust is nowhere near the weight of the aircraft. In the cruise at altitude full thrust is maybe just above 1/20 of the aircraft weight. Airliners have a lift drag ratio of maybe 1/20. Maybe a bit better with more modern aircraft.
But you get the idea, the weight of the aircraft is significantly more than thrust from the engines.
As the plane approaches high transonic speeds , approaching Mach 1.0 you get a dramatic drag build up, Critical Mach drag rise, or whatever you wish to call it.
Airliners are bluff objects designed to fly subsonically, so this extreme drag makes going supersonic very difficult.
So generally the max rate of descent will be about Mach 1.0
As an aside, using the FlightRadar24 altitude readouts, the rate of descent corresponds to about a 1,000 ft a second. 5,000 ft lost in 5 seconds if I read the numbers correctly. Or 60,000 ft a min or 685 mph. Local speed of sound is 707 mph assuming a standard atmosphere and a temperature of -25 C.
So vertical speed M 0.97 , this is only the vertical speed using the data. As stated by previous posts the data from FR24 can be smoothed or assumed. When you allow for the horizontal ground speed to get the true airspeed and Mach No. the numbers are higher.
With previous Jet upsets when the data is pulled and all the circumstances are allowed for, the max speeds always seem to be subsonic, or mildly supersonic.
As ‘ fdr ‘ stated as you descend into thicker air it is also warmer, which means the local speed of sound increases too. So for a given speed, the aeroplanes Mach No will decrease. As you descend into warmer air you should get more control.
There are two big issues with these high speed descents.
1:you can rapidly exceed the aircrafts design max speed which can lead to structural failure.
2: you need a lot of sky to pull out of a high speed descent.
Lastly, I have read that most ‘ Jet upsets ‘ that occur in visual conditions are survived, but those in cloud or at night with a limited visual reference are not.
From my aged memory the CAL 747 that had a ‘ jet upset ‘ was only flown correctly when the crew got a visual horizon at about 20,000 ft. I note that for this unfortunate flight, the cloud base was much lower.
P.S. My credentials; I can’t spell but have flown commercially for far too long.
With over 10K hours on the 737 including the 8oo and Max, and some training in accident investigation, I'd like to offer a few observations. First off, I dont believe it is possible to reach the ground in two minutes without the throttles pushed up.
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So, I served as a Captain flying Boeing 747-400, 747-300, 747-200, 737-800 and 737-700, a former lowly US Army helicopter pilot - No Cat Shots. I have landed on ships, but in helicopters (at night). Army-trained Aviation Maintenance Officer and Maintenance Test Pilot, Aircraft Mechanic License, published and paid international Aviation-safety writer, since 1983. At one time I held Airline Transport Pilot License from seven countries, including a Chinese ATPL. The day I sat the CAAC (Chinese ATPL) written examination, I was the only foreign captain in the room to pass and many Chinese pilots including former PLA failed the exam, too. It was still partially written in Chinese. Long retired after 36 years flying professionally.
I was a Contract Captain in China nearly five years. I was the first white boy contracted and the first foreign captain to sign a contract with the airline that merged with China Eastern Airlines. There was a long period of time, maybe as long as a year, I was the only foreign Captain at the airline. I actually flew China Eastern Airlines Boeing 737-800 aircraft, as a Captain. I feel damned upset that I may have known some of the flight and cabin crew. I have not asked. I would not. I almost prefer not knowing.
That said, to all of the above: Without the Flight Data Recorder recovered and analyzed, without the Cockpit Voice Recorder (now recovered and) analyzed, without ACARS QAR Data analyzed, by the CAAC and Boeing and hopefully NTSB, HOW THE HELL CAN ANY OF YOU ASSUME TO KNOW OR GUESS WHAT HAPPENED?!
If you are airline pilots or retired from the airline game, it is damned unprofessional to weigh in what you think might have happened. It contributes nothing to the Final Accident Report.
I will not be sharing anything on this forum, regarding the accident, other than the aforementioned and, rest assured Boeing manufactures great airplanes, designed to be flown well by very average pilots. I was one of them.
I was a Contract Captain in China nearly five years. I was the first white boy contracted and the first foreign captain to sign a contract with the airline that merged with China Eastern Airlines. There was a long period of time, maybe as long as a year, I was the only foreign Captain at the airline. I actually flew China Eastern Airlines Boeing 737-800 aircraft, as a Captain. I feel damned upset that I may have known some of the flight and cabin crew. I have not asked. I would not. I almost prefer not knowing.
That said, to all of the above: Without the Flight Data Recorder recovered and analyzed, without the Cockpit Voice Recorder (now recovered and) analyzed, without ACARS QAR Data analyzed, by the CAAC and Boeing and hopefully NTSB, HOW THE HELL CAN ANY OF YOU ASSUME TO KNOW OR GUESS WHAT HAPPENED?!
If you are airline pilots or retired from the airline game, it is damned unprofessional to weigh in what you think might have happened. It contributes nothing to the Final Accident Report.
I will not be sharing anything on this forum, regarding the accident, other than the aforementioned and, rest assured Boeing manufactures great airplanes, designed to be flown well by very average pilots. I was one of them.
Last edited by FWRWATPLX2; 24th Mar 2022 at 09:17. Reason: spelling
That said, to all of the above: Without the Flight Data Recorder recovered and analyzed, without the Cockpit Voice Recorder (now recovered and) analyzed, without ACARS QAR Data analyzed, by the CAAC and Boeing and hopefully NTSB, HOW THE HELL CAN ANY OF YOU ASSUME TO KNOW OR GUESS WHAT HAPPENED?!
Bonus point if you answered谣言
So why do people indulge in rumour and speculation? In my case it's because I want to learn from the mishaps of others, to hopefully avoid making those same mistakes. Who was it who said:
You must learn from the mistakes of others, because you won't live long enough to make them all yourself?
Last edited by FullMetalJackass; 24th Mar 2022 at 10:57.
It will be very easy to tell if info released is being held back. As Boeing and the NTSB have a right to access the recorders as well. So either they are granted access and will have to be forthright in their reporting or they deny access and everyone knows it’s a whitewash.
I think there is a better than even chance they will play it by the book.
I think there is a better than even chance they will play it by the book.
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"On Thursday, rescuers said they had found engine components, part of a wing and other “important debris” as they searched the mountainside in a rural part of the Guangxi region for a fourth day. A four-foot-long piece of debris suspected to be from the plane was found more than six miles from the main crash site, said Zheng Xi, the commander in chief of the Guangxi Fire Rescue Corps. As a result, search teams will widen the area they are combing, he added. At the main crash site, a state broadcaster showed the workers digging with shovels around a large piece of wreckage that the reporter described as a wing, which bore part of the China Eastern logo and was perched on a steep, barren slope fringed by dense thickets of now-flattened bamboo."
From the New York Times: debris recovered some distance from the main crash site.
From the New York Times: debris recovered some distance from the main crash site.
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Reuters just now : Debris from the jetliner including engine blades, horizontal tail stabilisers and other wing remnants was concentrated within 30 metres of the main impact point, which was 20 metres deep.
********One 1.3 metre-long fragment suspected to be from the plane was found about 10 km away, prompting a significant expansion of the search area, officials told a news briefing. ********************
Also reporting data accessible on CVR ... https://www.reuters.com/world/china/...et-2022-03-24/
********One 1.3 metre-long fragment suspected to be from the plane was found about 10 km away, prompting a significant expansion of the search area, officials told a news briefing. ********************
Also reporting data accessible on CVR ... https://www.reuters.com/world/china/...et-2022-03-24/
The first CCTV video shows a vertical descent due to camera angle, the dashcam footage shows a steep descent but not vertical.
Its difficult to see if the aircraft is right side up or inverted.
One thing I want to emphasize here, it is entirely possible to regain control after an upset and still be in an unrecoverable situation due to lack of altitude.
As in the airplane is under positive pilot control and still crashes.
Simulator upset training will show you how little time you have before the situation becomes unrecoverable either because the airplane is so far out of the envelope that it will come apart during the recovery or insufficient altitude.
This is obviously a PC simulation freeze frame but it’s the best picture to illustrate a possible scenario. Airplane ends up inverted and nose down. “Pulling through” as if flying a part loop will over stress the airframe and take a tremendous amount of altitude. Rolling upright and pulling out of the dive will overstress the airplane and run out of altitude.
The question that remains is what got them there?
Its difficult to see if the aircraft is right side up or inverted.
One thing I want to emphasize here, it is entirely possible to regain control after an upset and still be in an unrecoverable situation due to lack of altitude.
As in the airplane is under positive pilot control and still crashes.
Simulator upset training will show you how little time you have before the situation becomes unrecoverable either because the airplane is so far out of the envelope that it will come apart during the recovery or insufficient altitude.
This is obviously a PC simulation freeze frame but it’s the best picture to illustrate a possible scenario. Airplane ends up inverted and nose down. “Pulling through” as if flying a part loop will over stress the airframe and take a tremendous amount of altitude. Rolling upright and pulling out of the dive will overstress the airplane and run out of altitude.
The question that remains is what got them there?
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.
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.
Originally Posted by 45989
Did this in the sim as an experiment (800) 15 sec Above 250kts unrecoverable
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If it's a case is was a runaway trim even at extreme you could still get control of the Aircraft. the problem arises that there are 2 ways to do this which is ease the throttle so there's less friction on the elevation controls which they call the "roller coaster" so that you can manually adjust the trim Or increase airspeed to it's maximum threshold this of course makes it more difficult and normally a 2 man job to adjust the trim.
I think this is reason we see them try and gain control at 8000 and a increase in airspeed. Didn't the flight bank to the left?
In an extreme nose-up out-of-trim condition, requiring almost full forward column, decellerate, extend the flaps and/or reduce thrust to a minimum practical setting consistent with flight conditions until elevator control is established. Do not decrease airspeed below the minimum manouvring speed for the flap configuration. A bank of 30 degrees or more will relieve some force on the control column. This, combined with flap extension and reduced speed, should permit easier manual trimming.
I think this is reason we see them try and gain control at 8000 and a increase in airspeed. Didn't the flight bank to the left?
Recovery from a Severe Out of Trim
Accelerate or decelerate the airplane to an in-trim airspeed. If a recovery must be initiated from an extreme nose-down out-of-trim requiring a high pull force, an increase in airspeed may relieve enough of the elevator load and control displacement to permit manual trimming. Do not exceed speeed limitation. If a recovery must be initiated from an extreme nose-up out-of-trim requiring a high push force, a decrease in airspeed may relieve enough of the elevator load and control displacement to permit manual trimming. It should be noted that the relationship between airspeed change and trim change do not remain constant. As airspeed is increased, trim change requirements decrease.In an extreme nose-up out-of-trim condition, requiring almost full forward column, decellerate, extend the flaps and/or reduce thrust to a minimum practical setting consistent with flight conditions until elevator control is established. Do not decrease airspeed below the minimum manouvring speed for the flap configuration. A bank of 30 degrees or more will relieve some force on the control column. This, combined with flap extension and reduced speed, should permit easier manual trimming.
Originally Posted by B2N2
Airplane ends up inverted and nose down. “Pulling through” as if flying a part loop will over stress the airframe and take a tremendous amount of altitude. Rolling upright and pulling out of the dive will overstress the airplane and run out of altitude.
Originally Posted by Iknowhighschoolmaths
This gives us a terminal velocity of 170 m/s or 330 knots.
As for your comment You are exaggerating the 4-5 times, 43Inches gave you 5000fpm for an Emergency Descent (which in my experience is about right). You're stating the terminal velocity of a C172 is 330kts. That could be in no other condition except straight down. That's 33,000fpm (and would be much more in a 737). That is MORE than 43Inches "4-5 times".
I doubt your username.
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Very preliminary impression ...
My impression was that Chinese officials declared that parts of the horizontal stabiliser where found at the main crash site. And suggest a 30m diameter main impact zone.
The CVR was found with the 'box' flattened and the memory 'can' scraped but apparently intact. Not indicated where this was found.
Video of the main crash site show a fragmented plane with fragments of metal and composite (with honeycomb) structure overloaded and tubing/lines bent.
One engine was visible in a pit next to a pool of water (the area is very muddy now and more rain is expected - tough job for SAR, my respects - looks they need bamboo matting to get around in some places). The heavy rain appears to have started after the impact.
A bit above the direct impact zone there is a single (right hand) winglet and the trees in that area show a scythe like cut.
Some trees there appear to be about 35cm thick others leg or arm thick.
In the vicinity of the winglet lies what seems part of the top panel of the center section of the aircraft, which sits above the 2nd and 3rd window in front of the forward escape hatch.
A wing panel of a few metres long lies to a side (not sure yet if it was a top or bot panel), with Z-type stringers on one side, which is split spanwise through the lettering and along the edge of the covers.
It looks like the impact was perpendicular to a kind of gulley which has a walking path to at least one side. If true this makes the SAR job even harder. And might explain the landslide risk the Chinese authorities were referring to.
Debris was found a few miles away, no confirmation yet if that belonged to the plane.
So, at max two corners have been found and it seems like the nose section must be dug out.
It seems that the impact was not vertical but under more of a final angle than would be expected from the videos. With the dashcam video looking more representative.
My impression was that Chinese officials declared that parts of the horizontal stabiliser where found at the main crash site. And suggest a 30m diameter main impact zone.
The CVR was found with the 'box' flattened and the memory 'can' scraped but apparently intact. Not indicated where this was found.
Video of the main crash site show a fragmented plane with fragments of metal and composite (with honeycomb) structure overloaded and tubing/lines bent.
One engine was visible in a pit next to a pool of water (the area is very muddy now and more rain is expected - tough job for SAR, my respects - looks they need bamboo matting to get around in some places). The heavy rain appears to have started after the impact.
A bit above the direct impact zone there is a single (right hand) winglet and the trees in that area show a scythe like cut.
Some trees there appear to be about 35cm thick others leg or arm thick.
In the vicinity of the winglet lies what seems part of the top panel of the center section of the aircraft, which sits above the 2nd and 3rd window in front of the forward escape hatch.
A wing panel of a few metres long lies to a side (not sure yet if it was a top or bot panel), with Z-type stringers on one side, which is split spanwise through the lettering and along the edge of the covers.
It looks like the impact was perpendicular to a kind of gulley which has a walking path to at least one side. If true this makes the SAR job even harder. And might explain the landslide risk the Chinese authorities were referring to.
Debris was found a few miles away, no confirmation yet if that belonged to the plane.
So, at max two corners have been found and it seems like the nose section must be dug out.
It seems that the impact was not vertical but under more of a final angle than would be expected from the videos. With the dashcam video looking more representative.
Last edited by A0283; 24th Mar 2022 at 16:12. Reason: additions
