China Eastern 737 Crash: What Caused the Unusual Cruise Phase Tragedy?

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In summary: No, it's a specific condition where you have a flow separation over the top surface due to too high of an angle of attack. Diving toward Earth and having the wing produce no lift because zero effective angle of attack is not a stall.
  • #36
russ_watters said:
There was one I vaguely remember where part came off but it mostly remained intact while it nosed-over into the ground. I can't remember if it was the nose or tail though...
Googling tells me the front section of TWA 800 ripped off and it continued flying for a bit (even climbing) after its center tank explosion. I don't think that's the one I was thinking of though.
 
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  • #37
russ_watters said:
Googling tells me the front section of TWA 800 ripped off and it continued flying for a bit (even climbing) after its center tank explosion. I don't think that's the one I was thinking of though.
And AF447 crashed because the pilots were actively working against the machine confused by their misinformation. Or think of AQ243 when parts of the roof went off and the pilots still landed safely. Or JL123 were the heck broke away and the pilots were still flying for quite some time.
 
  • #38
fresh_42 said:
And AF447 crashed because the pilots were actively working against the machine confused by their misinformation.
Yes, that's the one I was referencing when I said "riding a stall all the way down". The first officer held the stick all the way back throughout almost the entire sequence of events after the angle of attack sensor airspeed indicator failed. Inexplicable actions.
 
  • #39
russ_watters said:
Yes, that's the one I was referencing when I said "riding a stall all the way down". The first officer held the stick all the way back throughout almost the entire sequence of events after the angle of attack sensor airspeed indicator failed. Inexplicable actions.
I recall that, isn't that the one that the ground crew forgot to remove the airspeed indicator cap prior to take off ?
 
  • #41
Oldman too said:
I recall that, isn't that the one that the ground crew forgot to remove the airspeed indicator cap prior to take off ?
No, it just flew through the top of a thunderstorm and iced-up a little.
 
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  • #42
Oldman too said:
I recall that, isn't that the one that the ground crew forgot to remove the airspeed indicator cap prior to take off ?
AFAIK one of the two Pivot tubes was iced due to washing the machine before the start and water came in.
 
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  • #43
fresh_42 said:
AFAIK one of the two Pivot tubes was iced due to washing the machine before the start and water came in.
No, that one was an aoa sensor on a different plane:
https://en.wikipedia.org/wiki/XL_Airways_Germany_Flight_888T

[edit] This one had implications for the Boeing 737 Max/MCAS issue as two sensors froze in the same position, one didn't and the computer rejected the functioning sensor because it was the outlier.
 
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  • #44
Oldman too said:
I recall that, isn't that the one that the ground crew forgot to remove the airspeed indicator cap prior to take off ?
At the risk of one more irreverent sidebar...

I recently designed a spaceship for a sci-fi game whose ship name, emblazoned in red on its flank, was "Remove Before Flight".
 
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  • #45
Quite a few years back a commercial airliner augered into swampland in Florida IMS. The impact crater of this flight reminded me of that event. Data recording boxes eventually recovered. Seem to remember a cargo fire severed controls to the tail or the flight crew was attempting to fix an errant indicator lamp, as mentioned above.

Learned a new term today for cockpit monitors listening to video from @anorlunda 's post: 'glass'.
 
  • #46
fresh_42 said:
Honorable. However, the B737 is a workhorse for decades. Mid-flight almost rules out a maintenance problem, an intact plane rules out a bomb or other causes for physical breaks. The fire rules out a fuel problem. The stall almost rules out a steering or trim problem.

There is not much left for reasonable causes.
From what I saw, it looked like a good portion of the tail was missing. Is that enough for an aircraft to come down so extremely?
 
  • #47
valenumr said:
From what I saw, it looked like a good portion of the tail was missing. Is that enough for an aircraft to come down so extremely?
Where did you see that?

Airplanes are nose-heavy. A broken-off horizontal stabilizer will make a plane pitch down toward the ground.
 
  • #48
russ_watters said:
Where did you see that?

Airplanes are nose-heavy. A broken-off horizontal stabilizer will make a plane pitch down toward the ground.
I saw this, but I can't really testify to it's veracity:
fark_IxtwyaYTTL16CLrpTPK_pUk2QkA.jpg
 
  • #49
valenumr said:
I saw this, but I can't really testify to it's veracity:
Where? Please provide the source.

The vertical stabilizer is so-named because it is oriented vertically, so it obviously has nothing to do with vertical motion. American 587, which crashed in Queens just two months after 9/11 did so because its vertical stabilizer separated. It lost lateral stability as a result. A plane would act like a lawn dart if the horizontal stabilizer detached. The description in the image is basically technobabble.
 
  • #50
russ_watters said:
Where? Please provide the source.

The vertical stabilizer is so-named because it is oriented vertically, so it obviously has nothing to do with vertical motion. American 587, which crashed in Queens just two months after 9/11 did so because its vertical stabilizer separated. It lost lateral stability as a result. A plane would act like a lawn dart if the horizontal stabilizer detached.
It was a repost in a forum from a tweet from a blog or something. I don't have the original source, thus I have little faith in it's truth. It is claimed to be a zoom from the live video (which happened) of the plane crashing. But it could just be a photoshopped picture of a plane rotated 90 degrees.

My question was, that if the plane lost most of the tail section, would it lose so much lift that it would just go straight down?
 
  • #51
valenumr said:
It was a repost in a forum from a tweet from a blog or something. I don't have the original source, thus I have little faith in it's truth. It is claimed to be a zoom from the live video (which happened) of the plane crashing. But it could just be a photoshopped picture of a plane rotated 90 degrees.
Ok. I think it's likely to be fake.
valenumr said:
My question was, that if the plane lost most of the tail section, would it lose so much lift that it would just go straight down?
As I said above, the vertical section of tail (shown broken off in the likely fake pic) doesn't do anything for up/down motion. But if the horizontal section broke off, yes, it could go straight down. As I said, planes are nose-heavy. The tail (horizontal stabilizer) doesn't add lift directly, it pushes down to push the nose up.
 
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  • #52
valenumr said:
My question was, that if the plane lost most of the tail section, would it lose so much lift that it would just go straight down?
It would not lose lift, no. It would lose attitude control.
 
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  • #53
Update
1648072103561.png

1648072238379.png

Blue, airspeed
Grey, Vertical speed
Yellow, Ground speed

The source says that they appeared to pull up at some point. It is possible that they stalled the wings during the pull-up.

He also talks about the picture of a plane diving with no tail (the one discussed earlier in this thread.) He says, that picture is not the accident aircraft, it comes from a TV show about some other accident.

Misinformation abounds.

My source:
 
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  • #54
anorlunda said:
...
The source says that they appeared to pull up at some point. It is possible that they stalled the wings during the pull-up.

He also talks about the picture of a plane diving with no tail (the one discussed earlier in this thread.) He says, that picture is not the accident aircraft, it comes from a TV show about some other accident.

Misinformation abounds.
...
The video in this interesting post clears up misapprehensions concerning stalls, attitude and their relation to angle of attack. Descriptions of inflight data recording also excellent.

Learned that air traffic controllers speak Mandarin communicating with pilots on these internal flights, presuming the voice record is authentic. English standard on international ATC comms?

[edited meandering post. Thanks, Mike :wink:]
 
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  • #55
anorlunda said:
Misinformation abounds.

My source:
Great info, thanks anorlunda. I like your source -- he seems very straightforward and knowledgeable. It's great that they are finding the flight recorders, and seems very significant that there was an attempt near the end of the descent to recover the aircraft.
 
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  • #56
berkeman said:
the radio report of the crash, the commentator (CBS? NBC?) said
Oldman too said:
From the NYPost article.
MSM never gets this aviation stuff right initially. We'll just have to wait a bit and see. But if you want good reporting try this guy:

 
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  • #57
Referencing the video in post #53 (https://www.physicsforums.com/posts/6613522) by @anorlunda:

Around 7:46 of the video, the presenter asks for help removing the music from the recording.
The voice comes thru rather clear with the following equalizer settings:
Code: 
 Hz      db
100     -12
200      +2
600      +3
1k      -12
3k      -12
You may want to optimize the higher frequencies a few db.

I do not have a good way to extract and save the audio here. Hopefully someone reading this can use the above settings for extraction.
Also I could not find a way to directly commumicate to the author of the video. With over 700 comments it's probably useless to post there.

Hope it helps.

Cheers,
Tom
 
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  • #60
Yeah, that PPE is not just to keep them from contaminating the crash site...
 
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  • #61
berkeman said:
They just found the Flight Data Recorder, 1.5m down in the dirt in the crater:
DaveE said:
Oof, that's got to be an awful job. Digging into a crater with 132 pulverized bodies mixed in.

Wait one. FDR mounted near tail? Ugh.
 
  • #62
berkeman said:
Yeah, that PPE is not just to keep them from contaminating the crash site...
Not to go off topic, my father, while in the Marine Corps, when stationed in the Aleutian Islands had to investigate plane crashes. He told me stories. The smell, as there was usually fire involved, was one that he never forgot.
 
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  • #63
Klystron said:
Wait one. FDR mounted near tail? Ugh.
Yes. https://www.spoonfeeding.in/2011/03/whats-black-box.html

"Another factor important to the survivability of the black boxes is their installation in the tail of the aircraft. The exact location often varies depending on the plane, but the FDR and CVR are usually placed near the galley, in the aft cargo hold, or in the tail cone. The recorders are stored in the tail since this is usually the last part of the aircraft to impact in an accident. The entire front portion of the plane acts like a crush zone that helps to decelerate the tail more slowly."

But my favorite part:
"Current regulations require the black boxes to survive an impact of 3,400 g's for up to 6.5 milliseconds. This rapid deceleration is equivalent to slowing from a speed of 310 miles per hour (500 km/h) to a complete stop in a distance of just 18 inches (45 cm). This requirement is tested by firing the CSMU from an air cannon to demonstrate the device can withstand an impact force at least 3,400 times its own weight. The black boxes must also survive a penetration test during which a steel pin dropped from a height of 10 ft (3 m) impacts the CSMU at its most vulnerable point with a force of 500 pounds (2,225 N). In addition, a static crush test is conducted to demonstrate that all sides of the CSMU can withstand a pressure of 5,000 pounds per square inch (350 kg/cm2) for five minutes. The fire resistance of the CSMU is further tested by exposing it to a temperature of 2,000F (1,100C) for up to an hour. The device is also required to survive after lying in smoldering wreckage for ten hours at a temperature of 500F (260C)."

Holy c#$@, I thought the satellite stuff I did had high g requirements; not even remotely close to this! It would be really interesting to talk to the MEs that did these designs.
 
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  • #64
dlgoff said:
Not to go off topic, my father, while in the Marine Corps, when stationed in the Aleutian Islands had to investigate plane crashes. He told me stories. The smell, as there was usually fire involved, was one that he never forgot.
Yeah, I've smelled dead bodies, and burned bodies. Very difficult triggers.
 
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  • #65
The orange "black box" was invented in Australia.
 
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  • #66
Well, the latest update is pretty disappointing. If true, it sounds like the data and voice recorders are so damaged that they have not been able to recover useful information from them (so far)...

https://abc7news.com/no-abnormalities-found-in-china-plane-crash-investigators/11773222/

The "black boxes" -- the flight data recorder and the cockpit voice recorder -- that can tell exactly what was going on aboard the aircraft were badly damaged in the crash, authorities said, and investigators are still trying to recover data from them to determine what happened.

1650549130992.png
 
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  • #67
berkeman said:
Well, the latest update is pretty disappointing. If true, it sounds like the data and voice recorders are so damaged that they have not been able to recover useful information from them (so far)...
Those flight recorders are an amazing example of engineering but there are limits, those limits would have been put to a real acid test in that crash. I don't know beans about recovering damaged digital data but if they are getting "all systems normal" that's got to be cr@p. considering radar data as well as the video I've seen those recorders would have to be screaming with alerts. I'm guessing "No Abnormalities" got lost in translation somewhere or there just isn't anything to recover. :frown:
 
  • #68
Oldman too said:
Those flight recorders are an amazing example of engineering but there are limits, those limits would have been put to a real acid test in that crash. I don't know beans about recovering damaged digital data but if they are getting "all systems normal" that's got to be cr@p. considering radar data as well as the video I've seen those recorders would have to be screaming with alerts. I'm guessing "No Abnormalities" got lost in translation somewhere or there just isn't anything to recover. :frown:
I'm pretty sure the "No abnormalities" thing is for the externally accessible data -- radar tracking and comms before the deviation in the flight.

At least the NTSB seems to be tied into this investigation, so I'm hopeful that there will be full disclosure of whatever data they can find.

I have a personal theory about the 3rd pilot who was allowed into the cockpit, but per the PF rules on speculation, I will hold my tongue for now. Very sorry for the terrible loss of life...
 
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