Yikes!
Scary. 
I have seen conflicting information about this.
One of the pilots on youtube (blancolirio) showed the publicly available ADS-B data which does not show any leveling off at 7,000 feet but instead shows a constant descent into the ground. I have also seen another graph which shows a leveling off of sorts around 7,000 feet (more of a brief recovery and slight increase in altitude, not really level) before a final descent into the ground.
The plane diving like that would likely be caused by either the elevator (controlled by the pilot pushing the yoke forward) or the stabilizer trim. All 737s (like most planes) have a stabilizer trim system. The idea behind it is that you trim the stabilizer up or down until the plane flies level so that the pilots aren’t forced to constantly put pressure on the yoke to keep the plane level.
The 737-Max’s infamous MCAS system tied into the already existing stabilizer trim system to automatically force the stabilizer trim down, so that it could automatically lower the plane’s nose to simulate the handling of previous 737 models. While MCAS caused the problem on the 737-Max there are other types of failures with the stab trim that can cause the stabilizer to runaway. I am not a pilot but my understanding of it is that on the 737-800 if you end up with a stab trim runaway you just switch off the stab trim system, then spin the trim wheels on either side of the console manually to adjust the trim back to where it should be. I think part of the problem with the MCAS system was that if MCAS misbehaved, Boeing thought that pilots would just treat it as a normal stab trim runaway (that they were supposed to already know how to handle) when in reality it was a bit of a different beast and needed some additional training to learn how MCAS differed from the normal stab runaway that pilots train for.
Again I am not a pilot, but if this does end up as some kind of stab trim runaway then my understanding is that this is still a bit of a pilot error sort of thing since pilots are supposed to be trained to handle this. It’s not the type of failure that you would expect to result in a loss of the airplane.
It could also be a mechanical problem with the stabilizer like what caused the Alaska Airlines crash a couple of decades ago. That one was caused by the airline skimping on the maintenance which resulted in failure of the jackscrew that moves the stabilizer up and down.
Here are some of the procedures for dealing with uncommanded stabilizer trim and stab trim runaway. From what I’m seeing in these procedures, in general the first step is to disengage the autopilot and address the problem via yoke and electric trim, and if the runaway condition persists, disengage the electric trim via the cutoff switches as a last resort.
So your description is correct, but I believe the problem is that beyond a certain airspeed the manual trim wheels just don’t exert enough force to operate a deflected stabilizer against the high dynamic pressure. So it seems like an electric trim malfunction that results in a big stabilizer deflection and isn’t dealt with promptly could potentially result in unrecoverable loss of control.
Can China read the black box data without the help of an American entity?
My cousin was killed in that crash.
Sorry about that. I wasn’t sure if I made that up or not and considered not bringing up the subject.
If it’s an issue for you, I have no problem if a mod wants to remove that last paragraph or break/remove the link.
No issue at all, it’s one of my more interesting stories to tell with that visual aid. I’ll probably watch the Mentour video later tonight.
If you’re not familiar with him, most of his videos are pretty similar to this. Very well explained, very detail oriented and, oddly enough, designed for other [usually newer] pilots but more than accessible to ‘regular’ people.
If you like his videos, Captain Joe and 74Gear (Kelsey) are both really good as well.
In any case, once you watch that video, you’ll be able to tell that story even better.
If the plane was at cruise speed and nosed over for any reason then it would quickly accelerate paste it’s structurally safe speed. And by quickly it would be measured in seconds and not minutes. If that was the case parts would separate.
Based on the video It looked like a steep angle into terrain so it may have gone supersonic. Impact would be tough on the black boxes.
They’ve reportedly found the CVR; it’s damaged, but they seem to think they can recover the recording from it. No word yet on the FDR.
Yes, that’s better news:
My earlier post was that investigators said it was so badly damaged that it might not have recoverable data. I’m glad that’s not correct. Still horrible overall.
Saw a report that some damaged aircraft parts were found six miles from the crash site. If it’s confirmed these parts came from this aircraft, it could mean the aircraft experienced some catastrophic damage while in flight.
Is a wing completely breaking off a realistic thing that could happen in flight? If one did, would the other most likely soon follow?
If the plane were suffering from extreme metal fatigue, maybe, but this was a relatively young airliner.
the 737-800 was experiencing cracks in the “pickle fork” which connects the body to the wings.
A terrible crash. So far a likely cause is, unfortunately, pilot suicide. It’s a sad state of things when wiki has a page listing the pilot suicides that have been “confirmed”.
Yes, a wing or wings could separate if the plane exceeds it’s rated structural speed. Basically they’re designed to fly within a speed that does not cause parts to resonate.
It’s hard to explain what it’s like when that happens. I once had a car with a bad wheel bearing. When it hit a certain frequency note from the exhaust it would violently shake the whole car in a matter of seconds. I had a truck pass me on the highway whose exhaust frequency triggered it. I replaced the bearing and it went away.
A 737-800 cruises at 530 mph. If it exceeds the maximum rated speed and flutter occurs imagine what those kind of wind forces would do to it. Those are wind forces many times greater than the worst tornado. It gets bad instantly. Imagine how fast microphone feedback occurs and then apply that to a physical structure. It’s a couple of seconds. If that resonant frequency is above the speed of sound you’re still left with control surfaces that lock up from the pressure wave created from hitting Mach 1.
I am reminded of USAir 427, which also fell out of the sky when things appeared to be going okay. That was also a 737. The cause of it and a similar accident a few ears prior was uncommanded full rudder.
If the weather was cloudy and they were IFR, I could see spatial disoriention as a cause. It seems like those kinds of upsets at altitude, especially as they often involve a roll, can easily put a swept wing aircraft in a steep nose-down postion.
For example, here’s a report on West Air Sweden 294 (I remember seeing it recently on Air Disasters) that went straight in from 30000ft. The flight went from smooth to terrifying to over in just under 2 minutes. The pilot flying was chasing a bad artificial horizon while the first officer tried to figure out what was going on.