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China Eastern 737-800 MU5735 accident March 2022

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China Eastern 737-800 MU5735 accident March 2022

Old 24th Mar 2022, 15:53
  #181 (permalink)  
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Originally Posted by B2N2 View Post
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.

The question that remains is what got them there?
Prior to doing Mdive testing I ran LED and DES simulations using STAR CCM+ of high-resolution 3-D BAC447 series of sections and variants, and found that the Cl collapses at extreme mach numbers, well above MMo. That was also associated with a very large shift in the Cm. The wing works fine within the design envelope. Any extended time in an extreme nose low atitude is going to compromise the ability to generate adequate aoa to get a good recovery pitch rate going. This isn't grandads pitch problems in his P-38 or Spitfire IX, its not even the P-80's discomfort at high speed, and it isn't reflected in the QTG if you go play in the B737 sim. This isn't specific to the B737, it is just one of those things, doing supersonic aerobatics is bad enough if you can pull 9 G if you start from M0.8 vertical downwards.

[ before discounting the loss of g capability at high speed ask any phabulous phantom driver what the g available was supersonic, or how much real estate gets used up with a supersonic dive from 45K, due to the limited g available to pull out in such a case. And that is a wing that arguably was designed for high-speed flight and dogfighting. Some may unkindly argue that the Phantoms wings were only used to have a place to hang MERs and fuel tanks].

The speed buildup just from gravity is ~20 kts/sec at -90 FPA, at 45, is around. 15 knots/sec, without the engine thrust, which adds about another 4kts a sec in a vertical dive. Drag increase is a fair bit but is still low order, the B737 total drag at M0.8 at average weighs is around 5,000-7,000 lbs roughly, it isn't a large amount, compared to acceleration available from gravity. Most speed brakes reduce lift, and that increases the aoa that has to be set to get adequate g loading, and that increases buffet and shock effects. Now this is not what the FAA espouses on aerodynamics, but then the FAA still demands we teach Bernoulli's principle for lift which just ain't so. Move your hand across the sink full of water and soapy bubbles, and you will find that the circulation theory/ bound vortex is visible, including the start vortex, the bound vortex and a stop vortex. What you won't find is what we are supposed to teach pilots about how their plane actually flies, which while simple to explain is fundamentally wrong, and gets wrongerer the more that compressibility comes into play.

Mods; remove or not this post, it is your choice. It is factually correct, and the insistence of our industry to put it's head in the sand means we are bound to repeat the same mistakes needlessly.

What happened to this aircraft, 50/50 the CAAC will not find a cause, and won't agree with Boeing. There is a guy in Denver that worked on kinematic reconstruction of some flight paths by a different method to the one I used in the same accidents, both being variants of MLE to match the couple of data points that existed. In one case, the CVR was able to give the engine RPM from the broad band FFT, and the actual acceleration and deceleration was able to be found from the harmonic lines of the AC system which ran fans in the cockpit; The CSD has a lag function and the overspeed or underspeed of the CSD is traceable on the CVR. The CVR in this case may ahve survived, the EEC memories are most likely to have survived, the DFDR had a less than 50% chance of surviving for various reasons.

it is possible that the debris dispersion analysis with prevailing winds will prove or disprove that any component departed early in the event. It is unlikely, but it would be reavealing if ever found. Components of the stabiliser/elevator and tail will very likely be found from a failure point in the mid dive case, and would be evident as missing components from the local debris field. The military search radar from around Wuxu airbase may have tracked the debris from the aircraft, it is about the right range to have tracked targets.

Last edited by fdr; 24th Mar 2022 at 16:06.
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Old 24th Mar 2022, 17:41
  #182 (permalink)  
 
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Originally Posted by Capn Bloggs View Post
Not if you don't pull too hard. And neither will, in every case, cause you to run out of altitude (as appears to be the case here, if indeed the leveloff was deliberate).
Civilian airliners are not rated for high G maneuvers, the 737 is +2.5 /-1 in clean configuration so your choice is to either overstress the airframe or run out of altitude or both if the initial loss of control was at even medium altitudes.
In the sim we do our upset recovery training starting at 20,000’ and I’ve frequently seen recovery as low as 4000’.
Vertical your choice is push or pull, negative or positive G. Anything less then vertical upright you pull, anything less then vertical but inverted would require rolling upright then pull.
I mean we’re talking aerobatic maneuvers here.
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Old 24th Mar 2022, 18:03
  #183 (permalink)  
 
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Standard procedure, thrust to idle, wings level, pull to nearest horizon.
With a -1 limit I would not being doing anything negative, it would be the last thing you do.
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Old 24th Mar 2022, 18:19
  #184 (permalink)  
 
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Am I seeing this correctly that there are two crash sites? The plane looked fairly intact in the videos, at least you could see both wings. Would a single engine have enough force to create the crater in this picture?

Drone footage shows they are a few hundred yards apart. Sorry can't post a damn picture for some reason. Google image search "mu5735 aerial", Pictures 1+2 are a few hundred yards from 3+4

Last edited by Noober; 24th Mar 2022 at 19:25.
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Old 24th Mar 2022, 19:53
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This looks like the set of pictures that Noober was referring to.
https://www.google.com/search?q=mu57...&bih=923&dpr=1
@Noober,: Was that right?

Pictures 1 & 2

Pictures 3 & 4
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Old 24th Mar 2022, 20:05
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Yep that's correct. There's drone footage floating around on twitter that shows these two locations are about 300-400 yards apart. Seemed a little odd for a plane hitting at that angle.

Bottom picture I believe in the main fuselage.
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Old 24th Mar 2022, 21:29
  #187 (permalink)  
 
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Originally Posted by Noober View Post
Am I seeing this correctly that there are two crash sites? The plane looked fairly intact in the videos, at least you could see both wings. Would a single engine have enough force to create the crater in this picture?

Drone footage shows they are a few hundred yards apart. Sorry can't post a damn picture for some reason. Google image search "mu5735 aerial", Pictures 1+2 are a few hundred yards from 3+4
The press conferences yesterday were reporting two main impact sites both sides of a hill, within 1sq km. They also reported some debris had been found 6 miles away and they were extending their search area as a result.
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Old 24th Mar 2022, 23:02
  #188 (permalink)  
 
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Good Grief
I spent nearly my entire career working jet turbine engines. While the technically correct term is "Thrust Lever", even I use the terms "Thrust Lever", "Throttle Lever", and "Throttle" pretty much interchangeably when talking the subject (I'm rather more careful when writing). Even Boeing people call the automatic thrust control feature "Auto-Throttle" even though those levers it moves are correctly referred to as "Thrust Levers" (and the group that was responsible for the function was always called the "Auto-Throttle Group"). Seriously, is there anyone on this forum who doesn't know what we're talking about when some writes "Throttles" or "Throttle Levers"? Sheese.
Can we possible quit the semantics discussions and get back to the topic of what may have caused this aircraft to crash?
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Old 24th Mar 2022, 23:09
  #189 (permalink)  
 
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Originally Posted by tdracer View Post
Good Grief
I spent nearly my entire career working jet turbine engines. While the technically correct term is "Thrust Lever", even I use the terms "Thrust Lever", "Throttle Lever", and "Throttle" pretty much interchangeably when talking the subject (I'm rather more careful when writing). Even Boeing people call the automatic thrust control feature "Auto-Throttle" even though those levers it moves are correctly referred to as "Thrust Levers" (and the group that was responsible for the function was always called the "Auto-Throttle Group"). Seriously, is there anyone on this forum who doesn't know what we're talking about when some writes "Throttles" or "Throttle Levers"? Sheese.
Can we possible quit the semantics discussions and get back to the topic of what may have caused this aircraft to crash?
It's actually very relevant to this thread, as non english speaking crew can be bamboozled by calling the same thing several names. It's very important when teaching ESL crews that the terminology is spot on. Airbus knows this as parts of the group come from non english speaking nations, hence why a lot of thought is in it's terminology. Boeing, well they just do things and put names that makes it sound different to the competition.
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Old 25th Mar 2022, 01:36
  #190 (permalink)  
 
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Fixed links from previous post:

Rescue underway after China air crash
Rescue work continues at plane crash site in mountain forests
Recovered black box believed to be cockpit voice recorder: official
Experts investigate plane crash site as rain hinders rescue work
Black box of MU5375 recovered at crashed site
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Old 25th Mar 2022, 01:42
  #191 (permalink)  
 
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Very preliminary impression part2

Photos are not good enough yet, but, Lonewolf_50 's two photo's.

The top photo has a gulley shape, it is not littered with fragments like the bottom photo. The top photo has blackened area's, which may refer to the initial fire. Some parts of the treeline in the bottom photo also appear to have some fire damage.
Based on this my first impression is that the top photo is land erosion and the bottom photo the impact area of the aircraft. So, still one main impact area. And based on official reports also possible but not yet confirmed items shedded earlier, but much further away.



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Old 25th Mar 2022, 01:43
  #192 (permalink)  
 
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Originally Posted by 43Inches View Post
It's actually very relevant to this thread, as non english speaking crew can be bamboozled by calling the same thing several names. It's very important when teaching ESL crews that the terminology is spot on. Airbus knows this as parts of the group come from non english speaking nations, hence why a lot of thought is in it's terminology. Boeing, well they just do things and put names that makes it sound different to the competition.
Agree. QZ8501 is another example, with the aircraft out of control heading towards the ocean, one told the other to ‘pull down’ on the sidestick, amongst numerous other non standard terms. Hardly helped the situation, in fact most certainly contributed to the end result.
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Old 25th Mar 2022, 02:25
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Originally Posted by PoppaJo View Post
Agree. QZ8501 is another example, with the aircraft out of control heading towards the ocean, one told the other to ‘pull down’ on the sidestick, amongst numerous other non standard terms. Hardly helped the situation, in fact most certainly contributed to the end result.
Hi PoppaJo,

This same sentiment has been expressed by others (re "non-standard" terms) with regard to the accident you mention. I have posted previously on PPRuNe about the problems with judging -- or even trying to understand -- words, phrases and conversations from CVR playbacks. It is something I have experience with, especially in the context of analysing CVR conversations between flight crew with different native languages (as was the case with QZ8501). In the case of QZ8501, the phrase "pull down" is not / was not uttered the way you and others seem to think it was. I was involved in that investigation and I can tell you that specific phrase, in that instance, uttered by that Captain, could easily be the entire subject of a PhD dissertation on multi-language crews in stressful situations. Feel free to PM me if you want to chat about this issue and that particular accident, as discussing it here would quite correctly be considered by the Mods as thread drift.

Cheers,
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Old 25th Mar 2022, 02:27
  #194 (permalink)  

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Originally Posted by 43Inches View Post
It's actually very relevant to this thread, as non english speaking
No it is not, not to this thread. Also not everything is about Airbus doing it better.
​​​​​​Chinese crew couldn't care less about 'rooners having a fit because the hair is too thick.

Most likely, outside of the USA, CEAir is one of the worlds top 5 operators of 737 per total accumulated sectors. This won't be a crisis of misunderstanding.
​​​​

Last edited by FlightDetent; 25th Mar 2022 at 02:48.
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Old 25th Mar 2022, 02:57
  #195 (permalink)  
 
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Originally Posted by 43Inches View Post
Airbus knows this as parts of the group come from non english speaking nations, hence why a lot of thought is in it's terminology. Boeing, well they just do things and put names that makes it sound different to the competition.
Now you're just being silly. Much of Boeing's terminology pre-dates the very existence of Airbus (heck, some of it probably dates back to WWII if not before). More specifically, the Boeing use of the term "Auto-Throttle' dates back to the 1960's - the early 747s had a system called "FFRATS" - Full Flight Regime Auto Throttle System.
Find me a pilot that doesn't know what "pull back the throttle" means, and I'll show you a pilot that has no business in the pointy end of an aircraft.
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Old 25th Mar 2022, 04:27
  #196 (permalink)  
 
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bloomberg reporting ..

"CCTV reported that some parts of the aircraft have been found 255 meters away from the main crash site."
More info here:
https://www.bloomberg.com/news/artic...d=premium-asia

Last edited by T28B; 25th Mar 2022 at 15:55. Reason: clean out color mess
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Old 25th Mar 2022, 05:42
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https://www.ndtv.com/world-news/seco...-media-2842001

FDR not found .Official statement.
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Old 25th Mar 2022, 07:37
  #198 (permalink)  
 
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Live stream
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Old 25th Mar 2022, 07:53
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China Eastern Airlines ground 223 738s

According to CNN (sorry can't post URLs but its front page...)

"The airline and its subsidiaries have temporarily grounded 223 Boeing 737-800 aircraft, airline spokesperson Liu Xiaodong said in a press conference on Thursday. The same type of plane was involved in the crash.".
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Old 25th Mar 2022, 10:33
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Officials at the press conference (in the CGTN live stream linked above) just stated that they were going to release the report(s) in English, as well as Chinese. Chinese is an ICAO working language, so they are not obliged to, but I guess they realise the international importance of this accident.
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