China Airlines goes down with 132 souls on board

Tools said:
Well... don’t all airplanes REQUIRE the horiz stab to provide down force to balance nose in a stable condition? So when it’s gone, the plane goes STRAIGHT down. I’ve seen this in practice with model airplanes A LOT.

Not like sort of start diving, but STRAIGHT down, right now. Lawn dart.

The bleriot might have been a “lifting tail”, but all “normal” airplanes are not. The tail works basically against the “spring” of gravity. In other words, down pitch is achieved in a controllable fashion with less down force... Never actually up force, unless you’re doing weird acro or flying upside down, which really doesn’t count.

So that straight down condition makes perfect sense (in my tiny pilot brain) without a horiz stab.
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I can think of only one off hand that produces lift rather than downforce.

https://en.m.wikipedia.org/wiki/Piaggio_P.180_Avanti
 
There was mention this happened at/near a normal TOD(top of descent) profile to descend for landing? I didn’t look to see if that’s accurate. If that’s true, could be a factor in how the descent was commenced.
 
The DTSB has weighed in and has declared it is a German Wings style event.
 
I'll guess. Guess 1 - Rapid descent, either intentional because of some problem, or unintentional similar to flight 006 above, followed by an attempted recovery at far higher than Vmo at near max control input, which resulted in structural failure of something important. Like maybe part of the tail. Which resulted in a near vertical descent.

Guess 2 - Poor maintenance led to a problem with the horizontal stabilizer, and it went nuts in flight, they thought they fixed it, but whatever they did, didn't work.

I'd bet on guess 1, but throwing out guess 2 out of respect for the crew.

And I don't even have a youtube channel.
 
benyflyguy said:
How does a black box withstand that kind of impact. Plus with that kind of impact I imagine death had to be as quick as it gets.
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I have this bookmarked to show college interns when they visit our office. It's dated, but interesting. See ->
 
sourdough44 said:
Just skimming through. I don’t envision much of a ‘coffin corner’ at 30k, likely somewhat lite also.

Most any system problem/failure will give you notice in the cockpit, pitot heat failure & such.

I’m still in the ‘human factors’ camp at this early point. Even with most any system or aircraft deficiency, with redundancy & intervention, no reason to nose dive.

I saw cloud cover in the video, no mention of extreme weather in the area.
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Whatsa coffin corner
 
dmspilot said:
Margin between stall buffet and Mach buffet
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Mach buffet I take it is just before the 'boom'? Is this kinda like a Va type thing? You want it stall before the plane breaks? Except now you want it to stall before breaking the sound barrier? I'm not getting the picture how it applies here?
 
The plane looks remarkably intact for a nose dive at 30,000ft per minute. I suppose it could have oversped without breaking up, but I would expect the plane would have way more damage. Looks like a horizontal stabilizer / elevator departed the plane or someone was trying to cash their life insurance check.

Edit: the flight track shows barely any change in airspeed. Almost like someone just dialed the autopilot to 0 feet.
 
luvflyin said:
Whatsa coffin corner
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https://en.wikipedia.org/wiki/Coffin_corner_(aerodynamics)

It's not a factor at FL291 in a 737-800.

luvflyin said:
Mach buffet I take it is just before the 'boom'?
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There is no boom. There is a constant pressure wave moving along with the supersonic airplane formed by the transition between sub-sonic and super-sonic flow--the shockwave. As this pressure wave passes those outside the airplane, they perceive the rapid change in pressure as a sonic boom.

The high-speed or mach stall is when the shockwave disrupts airflow above the wing in a manner very similar to a low-speed stall. The result is the same. Loss of airflow causes the wing to stall.

Coffin corner is when your low-speed, and high-speed stall speeds converge. Going faster, or slower, results in a stall. The only way out of it is to descend.

The 737 is thrust-limited so it doesn't have the power to climb to an altitude where it becomes an issue. Or, at least, it would be very difficult to get to such an altitude.
 
Larry in TN said:
https://en.wikipedia.org/wiki/Coffin_corner_(aerodynamics)

It's not a factor at FL291 in a 737-800.


There is no boom. There is a constant pressure wave moving along with the supersonic airplane formed by the transition between sub-sonic and super-sonic flow--the shockwave. As this pressure wave passes those outside the airplane, they perceive the rapid change in pressure as a sonic boom.

The high-speed or mach stall is when the shockwave disrupts airflow above the wing in a manner very similar to a low-speed stall. The result is the same. Loss of airflow causes the wing to stall.

Coffin corner is when your low-speed, and high-speed stall speeds converge. Going faster, or slower, results in a stall. The only way out of it is to descend.

The 737 is thrust-limited so it doesn't have the power to climb to an altitude where it becomes an issue. Or, at least, it would be very difficult to get to such an altitude.
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Ah. Got it. It literally changes the flow of the air over the wing. Thx
 
Larry in TN said:
https://en.wikipedia.org/wiki/Coffin_corner_(aerodynamics)

It's not a factor at FL291 in a 737-800.


There is no boom. There is a constant pressure wave moving along with the supersonic airplane formed by the transition between sub-sonic and super-sonic flow--the shockwave. As this pressure wave passes those outside the airplane, they perceive the rapid change in pressure as a sonic boom.

The high-speed or mach stall is when the shockwave disrupts airflow above the wing in a manner very similar to a low-speed stall. The result is the same. Loss of airflow causes the wing to stall.

Coffin corner is when your low-speed, and high-speed stall speeds converge. Going faster, or slower, results in a stall. The only way out of it is to descend.

The 737 is thrust-limited so it doesn't have the power to climb to an altitude where it becomes an issue. Or, at least, it would be very difficult to get to such an altitude.
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Ah. Got it. It literally changes the flow of the air over the wing. Thx
 
luvflyin said:
Mach buffet I take it is just before the 'boom'? Is this kinda like a Va type thing? You want it stall before the plane breaks? Except now you want it to stall before breaking the sound barrier? I'm not getting the picture how it applies here?
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There are areas of airflow that go supersonic well below Mach 1.0, this is what causes Mach buffet, and eventually, Mach tuck as the shockwave effect moves the center of lift rearward and causes a nose-down pitching moment.

The idea is not that "you want it to stall before breaking the sound barrier." The idea is to stay out of the flight region where stall and Mach buffet/Mach tuck converge. Because a stall recovery involves lowering the nose and increasing airspeed, while a Mach buffet recovery involves raising the nose and reducing airspeed. You can see how this would be a problem if these two events occur close together. Thus the name "coffin corner".

Larry in TN said:
The 737 is thrust-limited so it doesn't have the power to climb to an altitude where it becomes an issue. Or, at least, it would be very difficult to get to such an altitude.
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That's under normal operation, which the FAA says is a max of 1.2g. Load factor will increase the stall speed and lower the Mach buffet speed.
 
Therookguy said:
The plane looks remarkably intact for a nose dive at 30,000ft per minute. I suppose it could have oversped without breaking up, but I would expect the plane would have way more damage. Looks like a horizontal stabilizer / elevator departed the plane or someone was trying to cash their life insurance check.

Edit: the flight track shows barely any change in airspeed. Almost like someone just dialed the autopilot to 0 feet.
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Remember the flight track shows ground speed. If the airplane is in a steep descent but the ground speed doesn't change, then the airspeed is almost certainly increasing.
 
The Coffin Corner would be a great name for a smoke shop. Or a discount funeral parlor. Or a motorcycle shop. Probably not a good name for a successful flight school.
 
Catastrophic cabin depressurizing in the cockpit area?

Pilot or copilot got her down to altitude, pulled too many G's then down again?

Spitballing here. Don't want to step on Dan's toes.
 
Per a CAAC press conference: 1 recorder was found heavily damaged, ATC comms were normal, no weather issues, PIC had 6709 total flight hours, SIC had 556 hours, and a check pilot in cockpit had 31,769 hours. Some reports are listing the check pilot as the SIC.
 
No mentions yet of how widely debris was scattered?

I’m guessing the terrain will be hard to search.
 
I'd feel better about getting the actual truth if this wasn't in China. Of course an airline representative is going to say it the aircraft was "stable" prior to flight. And the Chinese government owns the airline.
 
Racerx said:
I'd feel better about getting the actual truth if this wasn't in China. Of course an airline representative is going to say it the aircraft was "stable" prior to flight. And the Chinese government owns the airline.
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FYI: according to other CAAC press releases, the NTSB, Boeing, and the engine OEM has been invited to participate in the accident investigation. Perhaps this process won't be as "clouded" as the SARS2 origin investigation since no outsiders were invited to that party.
 
Bell206 said:
FYI: according to other CAAC press releases, the NTSB, Boeing, and the engine OEM has been invited to participate in the accident investigation. Perhaps this process won't be as "clouded" as the SARS2 origin investigation since no outsiders were invited to that party.
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yea, sure... outsiders invited, doesn’t equate to a free flow of info.
 
luvflyin said:
Did they already know what the 'coffin corner' was then? Or is that when it was discovered?
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That was when they were figuring out how trans-sonic aerodynamics worked. They hadn't get figured out to use a swept wing as the X-1, in which Yeager broke Mach 1, had straight wings.

dmspilot said:
That's under normal operation, which the FAA says is a max of 1.2g. Load factor will increase the stall speed and lower the Mach buffet speed.
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At FL291 with 132 SOB, the margin between low and high-speed buffet is very large. So large, they both don't even show up on the airspeed tape at the same time.
 
I think we’re reasonably likely to get an answer if it’s mx/design related. China isn’t worried about Boeing stock price.
 
Larry in TN said:
At FL291 with 132 SOB, the margin between low and high-speed buffet is very large. So large, they both don't even show up on the airspeed tape at the same time.
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I agreed with you that is large under normal operation. It is not large under abnormal operation. What is the margin at 2g?
 
dmspilot said:
I agreed with you that is large under normal operation. It is not large under abnormal operation. What is the margin at 2g?
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A lot less, but then the question would be what caused them to pull 2g? Lots of things happens after the upset. We want to know what caused the upset.

I'm just saying that if you see hoofprints, think horses. Not Zebras.
 
Not really a player here, in the traditional sense, but here’s a pictorial on the ‘coffin corner’. This is an extreme example.

40759E47-7F63-4F56-B1A3-58588EF8203C.jpeg
 
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