[belter]

That matches the flight data posted from mlex reference:

Everything looks ok until:

6:19 AM UTC with the flight at 29100 ft (aprox 9 Km)

as of

6:22 AM UTC it's already at 9.000 ft (aprox 3 Km) dropping at vertical speed of -6,016 fpm

Excluding Terrorism, probably catastrophic Horizontal Stabilizer failure due to incorrect maintenance procedures.

Edit: Data available from past flights, shows this specific airplane in almost constant daily use, since at least Nov 2021. So it does not look like this was a flight after coming out of any recent major maintenance event.

[anon2020dot00]

If there is a lesson from the Boeing Max debacle, it is don't jump to conclusion of "incorrect maintenance procedures" like what Boeing did after the first crash with the Indonesian airline.

A lot of possibilities like Human/Pilot error, Equipment failure, Engineering design flaw, Freak bird collision accident, etc..

[belter]

I agree with you. Since this is not a MAX just the most likely to cause this vertical drop. But yes, you are correct, lots of other causes need to be considered.

[GekkePrutser]

They didn't jump to that conclusion. They almost immediately knew it was MCAS but blamed the Indonesians anyway as a distraction.

Source: the recent documentary that came out

Jumping to conclusions is one thing, deliberate disinformation is another.

[pc86]

Saying it's "probably" anything based off of two lines of text (even with a correlating video) is ridiculous irresponsible, and will almost always be wrong. Not to mention the fact there are a whole host of things that can cause a 6kfpm descent, both controlled and uncontrolled, that are neither terrorism nor the horizontal stabilizer.

[belter]

I already acknowledged this was a speculative line of thought. Don't think any air crash investigators are looking into a nobody on the internet for accident clues, so it's a kind of very limited irresponsibility.

However there are actually not that many causes, that could explain the vertical drop either than, and in order of decreasing probability:

- Suicide/Terrorism

- A Jackscrew Mechanism Failure: https://www.wikiwand.com/en/Jackscrew

- Accidental Deployment of the Reverse Thrusters.

The accidental deployment of the reverse thrusters, is something that requires multiple mechanical failures, is not supposed to happen but Boeing already has a past history with it, although on a different model. The Niki Lauda/Boeing controversy.

"What if the reversers OPEN in flight?!"

Video at correct time: https://youtu.be/OguKthkuaT4?t=1026

[GekkePrutser]

If the reversers open, wouldn't just shutting down the engines lead to a better scenario than this? I recall a 737 gliding too a nearby airport in Canada when it ran out of fuel.

I suppose it depends on whether the crew would have been aware of it.

[benjaminwai]

Can the reversers be opened independently on left and right side? From some of the 3D plots on various threads it looks like the plane took a sharp left before diving. Could it be the left reverser malfunctioned or be accidently opened mid flight causing the plane to swirl left and lose the aerodynamic?

[belter]

They can. Although incredibly rare. There are a few military airplanes that use reversers in flight to quickly drop altitude, but not used in any commercial passenger airplane that way. That scenario of only one opening, is also addressed in the video from Mentour Pilot that I linked. A few minutes earlier in the video. They have a checklist for it.

[belter]

It all happened in less than 2 minutes. The airplane could be in a unrecoverable nose dive faster then could even realize what is happening.

[piva00]

Do you work in the aerospace industry?

[throwaway0a5e]

>Saying it's "probably" anything based off of two lines of text (even with a correlating video) is ridiculous irresponsible

And as long as the number in the corner keeps getting bigger people will keep doing it.

You get what you incentivize. The purpose of a system is what it does.

[GekkePrutser]

I think it was more than 6kfpm. The plane dropped from 22000 in 2 minutes. Especially the end was fast. The dash cam footage looks almost vertical.

Maybe the VSI was reporting incorrect data due to the crazy fast descent. Or it was a report from the beginning of the dive?

[jacquesm]

> probably catastrophic Horizontal Stabilizer failure due to incorrect maintenance procedures.

That is highly speculative at this point, this airline has a very good safety record.

[belter]

Speculative yes. Highly speculative maybe not as much. You need to explain a 20,000 feet vertical drop in less than 2 min. Might not be the fault of the airline. Could be Boeing unclear instructions or a Supplier providing a faulty piece.

[GekkePrutser]

I bet that kind of drop will inevitably exceed the Vne because this plane does not have adequate speed brakes for this kind of maneuver (and why would it). I'm surprised it was still even intact when it hit the ground but according to the dash cam videos it was.

But I also think there's many things that can cause this. A terrorist taking over, the FBW system seriously messing up.

Anyway the investigation will tell us. Maybe soon because the black boxes won't be far away.

[belter]

Not sure if they black boxes survive this type of drop. On the Air Lauda crash one could not be recovered.

[GekkePrutser]

Good point. This was really extreme. I hope for the families that they will be found and everyone will get closure soon.

[jacquesm]

Not such a good point, given that one indeed survived, and that in that particular case it wasn't the impact that destroyed the other one but the post crash fire.

[jacquesm]

> Could be Boeing unclear instructions or a Supplier providing a faulty piece.

What is it with the senseless speculation?