737-8 max plane goes down (2018) - new not Max crash Indonesia

west didsblue said:
Was there a second JAL 747 that crashed?
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I thought they’d been involved in a high altitude stall, but I was conflating my carriers. My apologies.

I had mentioned that as an initiator of loss of control.

I thought people were referencing that. Never crashed, but it fell out of the sky for miles, IIRC.

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In 1985, a 747SP operating as China Airlines 006 descended 30,000 ft (9,100 m) in under two and a half minutes. The cause was an engine failure where the aircraft stalled when the autopilot in control was attempting to maintain the altitude and wings level. As the speed bled off, the aircraft entered an asymmetric stall. This then developed into a spin.

In 2018 a Qantas Jumbo jet fell for ten long seconds from 30,000 feet after being caught in a cross-vortex of other flights. An aircraft wake is made up of two vortexes spinning in opposite directions. In certain conditions, such vortexes can remain for up to three minutes.
 
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Cheesy said:
The only thing that can really cause a nosedive like this is the horizontal stabiliser. There's not many things that can cause the stabiliser to go full nose-down... complete hydraulics failure (highly unlikely - although has happened in the past), software failure or deliberate input from the pilot.
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Well a departed tailplane would probably cause a catastrophic shift in the centre of gravity and turn the thing into a dart pointing directly down. All limit speeds would be exceeded causing bits to break / snap off, increasing the speed down in all probability.

Tailplanes don’t just snap off though and I’m not sure even full nose down elevator would necessarily give a truly vertical dive as is being speculated. I won’t be holding my breath for an open and transparent investigation so who knows if we’ll ever find out…
 
PannickAtTheDisco said:
Surely you'd be pinned by the G forces?
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If you are pinned by G forces, what about the other guy?

And when you’re going down like a bat out of hell, those G forces are working AGAINST you push the aircraft down, no?

Once again, unless there is definitive proof this is a murder-suicide, I’d start looking at CAUSE & EFFECT.

What can cause an airplane flying along at 29,000 feet to create the effect of it hitting the ground almost vertically, and seemingly without all its control surfaces intact?

I’d suggest upset of some kind, as either the initial cause or initial effect of something else, leading to a loss of control. During such an event, pilots and the airplane itself can exert forces on the aircraft outside its design envelope.

During my own “upset training” we do multiple scenarios to help pilots understand where that control envelope is and just how easy, given a wrong input at the wrong time, one can exert forces beyond design limits upon control surfaces, such as wings, elevator, rudder/tail.

It would be almost impossible to create an airplane that couldn’t experience such a thing, even though modern FBW automation attempts to do that.

Indeed, the 787 pilot inputs are normally REQUESTS! The pilot tells the aircraft to do something (turn right, for instance, by turning the yoke to the right. The aircraft then takes that electronic input and first checks it, then agreed it’s within limits, and then sends signals to the control surfaces to make the aircraft turn. That happens in a split second, and the pilot doesn’t control which control surfaces the aircraft uses! It decides which control surfaces and how far to make it the most efficient right turn possible.

The 737-800 is NOT FBW, so direct pilot inputs are sent to control surfaces. In extremis, these can be an over control.

Conversely, in a loss of control effectiveness (due to failure or having the surface depart the aircraft), the pilot may not be able to do anything to save the aircraft regardless of skill or competency.

Cause & effect.
 
davealvers said:
Well a departed tailplane would probably cause a catastrophic shift in the centre of gravity and turn the thing into a dart pointing directly down. All limit speeds would be exceeded causing bits to break / snap off, increasing the speed down in all probability.

Tailplanes don’t just snap off though and I’m not sure even full nose down elevator would necessarily give a truly vertical dive as is being speculated. I won’t be holding my breath for an open and transparent investigation so who knows if we’ll ever find out…
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If you had a “loss of the ‘tail plane’” (if I understand what you mean by that), the least of your problems would be any minor shift in CG!!!

Think of an aircraft as a seesaw, where the wings are the fulcrum.
If the side where the tail is suddenly departs the seesaw, what happens to the side where the pilots sit?

The “tail plane” has a far greater impact on the aircraft than any weight shift (which is what creates a change in CG). It makes it flyable…or not.
 
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