Air India B787 crash Ahmedabad

[JohnM]

Let’s hope there was power to the black boxes!

Wouldn't they have battery backup?

 

[TheRealTMA]

Let’s hope there was power to the black boxes!

Aren’t they supposed to have 30 min battery backup?

 

[MEL_Traveller]

Supposed to, yes, but we saw from Jeju air that that doesn’t always happen.

The Jeju aircraft was 15 years old. The AI aircraft 11.5. They may have been advancements in the technology in those few years.

 

[RSD]

It's interesting that Captain Steve, and Juan, are now firmly in the RAT is deployed camp. I'm in the software issue camp, but apparently by myself.

Because it all looks so normal, right through to the end of rotation, the time prior to that has been discounted. Even the aircraft would keep quiet about most failures after 80 knots, and all after V1. Any issue here would probably have been transmitted in real time, and would be on the FDR. The point at which it starts to go wrong coincides with the point where gear retraction should happen...which is why everyone locked on to that. But what else happens at that time? Well one thing that does happen around there, is that the aircraft switches from ground to air mode. For the life of me, I can't see how that could directly cause this, but there would be some degree of reconfiguring in many systems happening with the mode change.

You + they may both be right in a way - software issue caused the engines to stop - dual engine failure causes RAT to deploy. The RAT deployment is caused by the failure - not the failure itself - so Captain Steve and Juan now need to work backwards into what caused the RAT to deploy.

From the lack of engine noise in the video, and the F/O's mayday call about lost thrust it seems that both engines have shut down - an inadvertent retraction of the flaps shouldn't cause that (if they were even retracted by mistake), so really now the focus needs to be on what caused the loss of thrust in both engines. Given that so few things can cause a dual engine failure then a software issue is something that could be a potential cause - but then why has it taken 11+ years to appear? A few more rabbit holes to be looked into.

Bird strike was mentioned very early on but that thought seems to have been discounted by everyone now, so we are back to a major dual engine failure - of unknown cause at the moment.

 

[oz_mark]

From the lack of engine noise in the video, and the F/O's mayday call about lost thrust it seems that both engines have shut down - an inadvertent retraction of the flaps shouldn't cause that (if they were even retracted by mistake), so really now the focus needs to be on what caused the loss of thrust in both engines. Given that so few things can cause a dual engine failure then a software issue is something that could be a potential cause - but then why has it taken 11+ years to appear? A few more rabbit holes to be looked into.

Latent software issues can take ages to appear. Consider how long it took the issues with QF72 to show up.

 

[RSD]

Latent software issues can take ages to appear. Consider how long it took the issues with QF72 to show up.

Very true - and we all know that software updates can introduce problems too!

 

[flyer89]

It really seems like the RAT did deploy, all rather circumstantial but it appears you can hear it on the video.

You can hear the RAT on 787’s that have both engines operating of which there are a few examples on YT. Someone has even posted a video of the 787’s RAT deploying which does come with a thud which would amplify in the cabin and could back up the lone survivor’s comment.

 

[SYD]

Very true - and we all know that software updates can introduce problems too!

Sometimes due to poor configuration control where it’s critical to match a certain hardware configuration update with a new version of SW.

But wasn’t this aircraft just cycling through several routine ops. So it would be odd that a sw glitch just randomly manifested itself.

The reports of faulty/flaky electricals on previous flights would be of concern and how that could impact onboard sensors and computer controls?

 

[DejaBrew]

An exceedingly uneducated question here...

If I recall correctly, the Angle of Attack sensor(s) was one of the contributing factors in the 737MAX crashes. Is there any possibility that a failed or faulty AoA sensor could feed incorrect data to the extent that it could adversely affect engine thrust?

 

[kangarooflyer88]

Something to consider: Do jet engines require electrical power to continue running? The reason I ask is that if the electrical bus cut out on the airplane that could potentially be why they encountered dual engine failure. And I believe RATs deploy at either electrical failure and/or dual engine failure.

 

[RooFlyer]

And I believe RATs deploy at either electrical failure and/or dual engine failure.

The Juan Browne video posted here covers the RAT issue pretty well, for lay-people at least.

 

[kangarooflyer88]

The Juan Browne video posted here covers the RAT issue pretty well, for lay-people at least.

Fair enough but the question still remains: do engines need to have a constant supply of electrical power to keep running? The more I think about it the more such a thing seems likely. I mean even if the engine could spin and do its thing with the fuel supplied, well those engines will eventually run dry of fuel is the fuel pump requires electrical power which I suspect it does. And just to be clear I am no aircraft mechanic or pilot. I have no idea how the electrical system on a modern jet like the 787 World and how it interfaces with other safety critical items like the engine and flight surfaces. However, I have yet to see any of the pilots on YouTube be it Juan or Pieter or anyone else examine this possibility either

 

[jb747]

Snipped this from Captain Steve, but wondering if it indicates anything about the flaps?

The wreckage images seem to discount the flaps being in the wrong place. You can definitely see the slats, and the break line for the flaps is also visible in the original (clearest) video. I don't think flaps are part of this at all.

An exceedingly uneducated question here...

If I recall correctly, the Angle of Attack sensor(s) was one of the contributing factors in the 737MAX crashes. Is there any possibility that a failed or faulty AoA sensor could feed incorrect data to the extent that it could adversely affect engine thrust?

The AoA issues with the MAX occurred because Boeing installed two, but was only taking MCAS data from a single probe. Single source is always bad! I don't think Boeing has an equivalent to the Airbus alpha floor, but in the AB if you have too much AoA, the aircraft will apply full power (irrespective of the position of the throttles, and even if auto thrust is not engaged). It won't pull the power off due AoA.

Something to consider: Do jet engines require electrical power to continue running? The reason I ask is that if the electrical bus cut out on the airplane that could potentially be why they encountered dual engine failure. And I believe RATs deploy at either electrical failure and/or dual engine failure.

Electrical or hydraulic failures. Of course the dual engine case gives you both of them as well. A jet should continue to run without electrical power, using gravity feed from the fuel tanks. TOGA probably wouldn't be available. Hard to say just how much power there would be. The fuel control units probably don't work without power but they should have some sort of integrated power generation. One would hope that their no power default is lots of power, but who knows. I think the reason the QF32 ended up on the ground with an engine they couldn't shut down was related the fuel valves having a power off default of open. Irrespective of where the defaults are, gravity feed at high power is unlikely to give you a normal fuel flow.

 

[kangarooflyer88]

Electrical or hydraulic failures. Of course the dual engine case gives you both of them as well. A jet should continue to run without electrical power, using gravity feed from the fuel tanks. TOGA probably wouldn't be available. Hard to say just how much power there would be. The fuel control units probably don't work without power but they should have some sort of integrated power generation. One would hope that their no power default is lots of power, but who knows. I think the reason the QF32 ended up on the ground with an engine they couldn't shut down was related the fuel valves having a power off default of open. Irrespective of where the defaults are, gravity feed at high power is unlikely to give you a normal fuel flow.

Well here’s the question, supposing it was an electrical fault that was the root cause of the accident for a moment and the engines not performing as they spills was a side effect for just a moment, what sort of performance could we expect here? You mention the engines could be gravity fed fuel but performance would likely be less than TOGA power. Well we know the aircraft crashed at take off, so then the question is when departing an airport like AMD with the aircraft loaded as it was, what was the minimum amount of engine power required to maintain a safe take off? It seems unlikely that the full TOGA power would be required since there is always a safety margin built into these calculations since the cost of getting it wrong can be huge. Another point, in Boeings design of the jet did they account for a failure mode where the entire electrical bus was non operative to the point where a RAT is less useful than an indoor fan? My theory is based on the idea that the jet was so poorly maintained that electrical power distribution degraded to the point where you couldn’t count on power being delivered anywhere. Again that’s an insane failure mode and one I suspect not even Boeing would design for in their wildest dreams.

 

[Quickstatus]

Is the aircraft rego usually on the underside of the wing?

 

[Quickstatus]

Landing gear position:
Normally when landing gear is down, the rear is tilted down, then when it is stowed, it first moves so the front tilts down before being stowed

See this YT video for the normal 787 gear swing

The videos suggests that the front of the landing gear is tilted down....?? maybe in preparation for stowage when power then hydraulics lost??

 

[Daver6]

Is the aircraft rego usually on the underside of the wing?



View attachment 450860

View attachment 450863

Yes

 

[Quickstatus]

Yes

Though the pictures suggest the top of the wing is where the rego is printed.

 

[oz_mark]

Top of the wing

 

[jb747]

Though the pictures suggest the top of the wing is where the rego is printed.

Top of one wing, and bottom of the other. Common enough.

Post automatically merged: Yesterday at 7:17 PM

Landing gear position:
Normally when landing gear is down, the rear is tilted down, then when it is stowed, it first moves so the front tilts down before being stowed

See this YT video for the normal 787 gear swing

The videos suggests that the front of the landing gear is tilted down....?? maybe in preparation for stowage when power then hydraulics lost??

I think you’ll find that it’s just the rest position that it assumes without pressure holding it elsewhere.