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Comment by lini | Hacker News Reader

Alleged footage of the crash shows the plane dropping from the sky like a rock: https://twitter.com/aviationbrk/status/1505835466943352836

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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.

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..

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.

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.

> 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.

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.

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.

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

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

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.

Black Boxes are designed to stand 3,400 Gs what is about 300 Mph. Maybe the airplane did hit the ground at close to those speeds.

And the fact that the second one did not survive the crash due to fire, shows they are not indestructible. Fire is actually what they are supposed to survive for at least 1 hour.

This is a very simplistic view of an airplane crash. The whole airplane is the crumple zone for the black boxes mounted in the tail of the aircraft, that's for a pretty good reason so there goes one assumption, it's not like they are in the nose. And for another, those black boxes that were lost usually were lost either because the whole airplane was lost or because of the post impact fire.

There are some instances of flight data recorders and cockpit voice recorders that were destroyed but not a whole lot of those. That said, this was an exceptionally violent impact and it remains to be seen if there is anything usable.

But - again - speculation is utterly pointless there is simply no information to go on other than the angle and speed of impact, which definitely isn't giving hope, but it doesn't rule anything out either. So let's just be patient until there is actual data. Nobody ever said that black boxes are indestructible.

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

What is it with the senseless speculation?

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.

>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.

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

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.

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.

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?

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.

Do you work in the aerospace industry?

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?

2nd camera footage (dashcam) with total nosedive

https://twitter.com/Aviation_NewsTW/status/15058583238279987...

Oof man that's brutal straight down

Is it possible this was suicidal?

My morbid curiosity wonders if the passengers had internet.

Their phones might have but the passengers would be unconscious.

Based on what? As horrific as it might be it wouldn't surprise me if passengers were conscious all the way down. Even if oxygen masks didn't deploy or work, at 26,000 feet you have a few minutes of useful consciousness after rapid decompression [1]. Combined with the fact that the plane would be rapidly descending.

1: https://en.wikipedia.org/wiki/Time_of_useful_consciousness

G forces.

Nonsense. G forces are changes in speed or direction, those were pretty mild based on what we know right now, freefall or powered flight into terrain does not give huge G forces until impact.

I recall a similar nose down crash that saw 5G force before it was recovered at 11000 feet. But you seem to be very sure?

https://en.m.wikipedia.org/wiki/China_Airlines_Flight_006

5g forces on impact would imply the projectile stopped at ~50m/s^2 (numerically 5x the gravitational constant) deceleration. In a free fall, it hardly exceeds 1g, unless the aircraft was powering it to hurtle down faster

Read the accident report. It hit nearly 5gs on a powered descent and roll before the pilot recovered the plane.

Yes, it did. Now what does it tell you that the crew never lost consciousness?

G-forces are not experienced equally based on the axis on which the plane is moving or the speed at which it accelerates/decelerates. The airframe of that plane was deformed with the wings bent permanently indicating non-plastic deformation, and yet the passengers were fine.

Imagine a plane rotating on the axis through the COG nose moving 'down', that would give the pilots negative G, the people near the tail positive G and everybody in between something along a gradient, those near the COG would likely not experience much difference. If the plane came out of a steep dive then there would be a lot of positive G, and if someone were to black out that would likely be only for a moment. A powered descent into terrain would be far less in terms of G's than violent maneuvers such as steep banks or coming out of a steep dive.

Maybe I'm missing something: Why would the passengers be low on oxygen when they go into higher pressure air?

They wouldn't be. As the plane descends and the pressure increases the oxygen levels increase as well.

- JAL 350 - Germanwings 9525

You can't really rule that out a-priori any more and there are a couple where we likely will never know for sure.

anything is possible, it could also disintegrate midflight for whatever reason (bomb, factory/maintenance error), difficult to fly without wings for instance or with plane broken into two pieces

they found piece of wing away from crash site https://na.cx/i/xZu3nE9.jpg

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