Air India 787 crashes on take off 1

[LittleInch]

A full 787-8 has crashed shortly after take off in ahmedabad.

Basically barely got off the ground then look like its trying to land in this video.

Air India flight to London Gatwick crashes in Ahmedabad with more than 240 people onboard – latest updates

Plane for flight AI171 was carrying 242 people including 169 Indians and 53 Britons, says Air India

www.theguardian.com

Specualtion that they pulled flaps up instead of gear up and basically didn't have enough lift so it looks like a gentle stall right into a built up area.

Looks to be flaps up, slats/ nose flaps down and gear down which is very odd.

 

[Alistair_Heaton]

It definitely doesn't solely, its one of these triple redundancy systems for FBW.

Although quite how it works I have no clue. I am actually hoping that someone that does, is going to show up and explain.

 

[TugboatEng]

I can't believe the FADEC takes 3 separate throttle inputs simultaneously and votes on them like other critical sensors such as air speed or AoA.

 

[Alistair_Heaton]

They are digital inputs. And there is a voting system which then links to the EICAS.

Its called the EEC (electronic engine control).

Which we have 2 channels per engine with a 3rd emergency. And if 2 go leaving only the emergency the other engine can support the other with its spare. You can still depart with 1 channel down gives an engine redundancy loss I think. Its a B MEL item 3 days to fix I think . If you get down to emergency channels in use its land at nearest suitable I think. Haven't checked the manuals so maybe incorrect. Its all in a EICAS checklist.

This is the problem with running multiple MEL failures there is no way all the combinations can be predicted and the interactions and response on the software.

What's in the lever quadrant in the 787 I really don't know.

This was the problem with the A220 dual engine shut down on landing .

We don't need to know how it works. Or what has a vote in things.

“A subsequent investigation determined that the sequence of the auto-throttle increasing throttle to maintain Mach number, immediately followed by pilot command to decrease throttle to idle, caused a transient disagreement between actual and commanded thrust. This disagreement triggered the thrust control malfunction (TCM) detection logic and resulted in dual engine shutdown once the weight on wheels signal was activated upon landing”, the FAA AD says.

It adds: “The installed EEC Full Authority Digital Engine Control (FADEC) software version latches the fault and allows the engine to continue operation as commanded but shuts down the engine upon landing.”

The FAA notes that P&W has identified the situation that could trigger a fault in the TCM logic and has come up with a software update. “This software update makes corrective improvements to the TCM logic, including revised criteria for triggering the TCM logic and establishing criteria that permit the TCM logic to unlatch during flight.”

 

[1503-44]

I have run videos above, the one with AI flight passing above to the left and another one I found of a flying 787 with with the RAT deployed, for testing purposes, through a sound analysis app called Spectroid. Spectroid makes a waterfall plot of all frequencies and amplitude. I think I see similarities.I believe the RAT WAS DEPLOYED.

As I mentioned previously, the 14 seconds up and 14 seconds down would point to a highly kinetic launch. I'm going with power loss within seconds after, or even before liftoff.

 

[1503-44]

I just saw that Captain Steve's latest video has amended his opinion to the same.

 

[Alistair_Heaton]

Can people keep an eye out for anything to do with the hydraulic isolation valve.

There are 2 valves away the engine which stop fuel and hydraulic fluid going past the fire wall each side.

That valve which is used in the event of engine fire is my prime suspect for the one that shuts down the engine so quickly. If both it and the hydraulic valves are shut then it's a emergency shutdown trigger.

Don't ask me how that works I just know it's different from the normal shutdown sequence.

 

[Garbage1]

There is already an 2023 air worthiness directive concerning .

"Risk of foreign object debris in 787 fire switches prompts FAA action"​

This AD was effective January 18, 2023, and required parts swapping. Federal Register link below.

"The proposal, made public on 7 July, warns that “foreign object debris could have been introduced during rework of certain engine fire shut-off switches” on 787s."
"The debris could cause “uncommanded activation of the engine fuel shut-off function”, or prevent pilots from pulling the engine fire handle, the proposed AD says."

Risk of foreign object debris in 787 fire switches prompts FAA action

The risk of foreign object debris in Boeing 787 engine fire shutoff switches has prompted action by the US Federal Aviation Administration.

www.flightglobal.com

From Federal Register it says "and uncommanded activation of the fuel shutoff function for an engine, combined with in-flight shutdown of the remaining engine, could lead to total loss of engine thrust."

Federal Register :: Request Access

www.federalregister.gov

I also attached the 2020 Boeing Requirements Bulletin, concerning Engine Fire Protection and it references a 2019 Air Worthiness Directive. This appears to be an internal document issued prior to the 2023 AWD?

Point to all of this, is there has been supplier issues with the emergency engine fuel shut off system, in case of engine fire, prior to this incident. FAA issued AWD Jan 18, 2023 for affected serial numbers. What did Air India do as result of FAA directive, if anything?

 

[thebard3]

That article is from 3 years ago. No action items came from it?

 

[Sym P. le]

Landing gear retraction was initiated.

As explained by Greg's Airplanes and Automobiles, the retraction sequence tilts the main gear forward prior to lateral movement into the stowed position. Video footage clearly shows the main gear in the forward tilt orientation. The full retraction sequence for a 787 is seen in the Youtube short here.

 

[Alistair_Heaton]

It's almost as if the gear handle being used started a sequence.

I can't see the debris occuring at exactly the same time to both engines.

 

[TugboatEng]

When is the APU secured if used for a startup? On the ground, in the air? If an engine has a generator out would the APU be used during the takeoff?

The 787 advertising claims multiple variable speed generators per engine all feeding a central distribution panel. Hopefully there isn't a single controller operating all of those variable speed controllers.

We're the wild West with regards to redundancy in the tugboat industry. Our philosophy is that doubling the number of components doubles redundancy... Meanwhile, we have backup power systems that can latch onto dead sources, dual ECM's that allow a failed controller to take command, unannounced control source changes, and broken steering potentiometer shafts that take out both pots simultaneously. I work for the premier company and we buy from the premier manufactures and I still get stuck with sh*t.

Rant over. When I see the advertising for the 787 electrics I see trouble. Each engine and control surface should have direct signal to the cockpit, left and right.

 

[Alistair_Heaton]

Normally if not required for departure performance or to cover something like a generator unserviceable we would shut it down before taxi.

There are a few reasons to have to keep it on. Some are type specific. It is also possible to operate with it unserviceable.

 

[PirateFoxy]

Normally if not required for departure performance or to cover something like a generator unserviceable we would shut it down before taxi.

There are a few reasons to have to keep it on. Some are type specific. It is also possible to operate with it unserviceable.

It was quite hot and reportedly there were AC issues on the ground, if that would change anything about APU use.

 

[TugboatEng]

Im digging because this picture shows all power routing through the aft electronics bay. That's where the APU start battery is located. The general backup battery is located in the forward electronics bay near the cockpit. However, according to this image all power to the engines routes through the aft electronics bay so there is a common fault location that could take everything down.

Our Navy is experiencing similar design issues with their modern warships. The invention of Ethernet has inspired engineers to always try to put everything on a common bus at some point.

 

[Alistair_Heaton]

I think that's a dumbed down diagram for none maintenance.

We have similar in my manuals but if your one of the rare pilot types that goes and has a look these areas are firewalled between sections and systems.

Here is a 787 bus schematic

 

[Alistair_Heaton]

It was quite hot and reportedly there were AC issues on the ground, if that would change anything about APU use.

Type specific and also company dependent. I don't know about either.

I think the Aircon and pressurisation is electrically powered on the 787. But could be wrong.

They would need it on for bleed air to start the engines. They would have reported it needed an air starter and cross bleed start by now.

 

[LittleInch]

Virtually everything is electric on the 787, hence why they need such a large set of generators, reported elsewhere as up to 1.5MW...

I think CAC on the electrical diagram is Cabin Air Conditioning.

Engines are electric start and then that doubles back as the generator (starter generator as shown on tugs schematic)

The current theory as to status is that whilst they got the rear data recorders, they died when the engines died. The forward one ( reported as the CVR, but they are duplicate CVR/ FDR units) is independently powered for 10 minutes with a cockpit area microphone, but no idea what else it picks up in terms of data if the main power supply has collapsed.

I'm beginning to get a nasty feeling that the data will not really say why something happened a bit like that crash in Korea as when the engines die so does all the data recording, though it might pick up some isolated bits once the RAT gets into its minimum power supply.

It also looks like the APU inlet duct was open at the point of the crash and this may have been what the passenger heard as an engine "racing" noise or something came back to life for a few seconds once the APU had auto spooled up on loss of power.

Some point soon they will surely have to mandate HD video cameras in the cockpit with an autonomous power supply that can pickup what the instruments are showing on both sides.

And airports routinely videoing take off and landings from the end points and tracking from the end of the runways.

Relying on some kid holding a mobile phone taking a video because he had never seen planes taking off before and a grainy CCTV camera is just nuts for an industry where each plane costs tens of millions of dollars.

 

[thebard3]

I'm sure the data recorders on airliners are insanely expensive. However, it seems like some small simple recorders could be added to an airplane, especially one that is 'fly-by-wire' to provide redundancy. Most control systems have a communication bus that connects to the extents of the equipment, where it should be relatively easy to install several recorders in various areas. That would lessen the likelihood that a single recorder could not be located. The more in use, the less requirement to harden for protection against crash damage. Also, power usage on these would be low, so a small battery backup should keep the recorder operational, even if the data stream fails.
The data recorder concept seems to date back to the early jet age. New ones still look like they always have, although the internal hardware and equipment is completely different.
I'm just looking at it in the light of my experience with industrial process control. Nothing in this field today even resembles anything that was used 40 years ago. It seems to me like the whole concept of data collection and real time monitoring of airliners is not in line with best available technology.

 

[LittleInch]

I appreciate they have the be super reliable and now most of the data is stored on solid state devices and not the old revolving tape or similar from the past.

But the industry really needs to get into the modern age and airports could very very easily video every take off and landing in HD. It would cost virtually nothing and provide so much useful evidence for everyone pretty much instantly.

 

[Garbage1]

This article on the 787's AD to fix software issue from 2015, shows 787's are not just more fly-by-wire, but are much more software controlled, which can have some unique latent defects, once the holes line up.

"According to the AD, if the 787’s power control units are operated for eight months (248 days) continuously, a software glitch can shut down the entire aircraft’s electrical system, which can result in a complete loss of aircraft power. This could even happen mid-flight."

Power-Killing Software Glitch Found in Boeing Dreamliner - Engineering.com

Simulation reveals failure mode without risk to aircraft

www.engineering.com

More on new software power failure, May 1, 2025 article. Not sure if this is same as 2015 AD or not at this point.

"This AD was prompted by the determination that a Model 787 airplane that has been powered continuously for 248 days can lose all alternating current (AC) electrical power due to the generator control units (GCUs) simultaneously going into failsafe mode," the memo stated. "This condition is caused by a software counter internal to the GCUs that will overflow after 248 days of continuous power. We are issuing this AD to prevent loss of all AC electrical power, which could result in loss of control of the airplane."

"The memo went on to say that Dreamliners have four main GCUs associated with the engine mounted generators. If all of them were powered up at the same time, "after 248 days of continuous power, all four GCUs will go into failsafe mode at the same time, resulting in a loss of all AC electrical power regardless of flight phase."

Boeing 787 Dreamliners contain a potentially catastrophic software bug

Beware of integer overflow-like bug in aircraft’s electrical system, FAA warns.

arstechnica.com

And here is another new reboot every 51 days AD from 2020. A lot of timely rebooting seems to be required to keep 787's flying....

Boeing 787s must be turned off and on every 51 days to prevent 'misleading data' being shown to pilots

US air safety bods call it 'potentially catastrophic' if reboot directive not implemented

www.theregister.com

And Radio Software Issues on going. April 2025 article.

Boeing 787 Radio Issues Persist Despite Fix, FAA Drafting New AD

Boeing is facing ongoing challenges with its 787 Dreamliner's radio communication problems, even after attempted software fixes.

aviationa2z.com

I have to hard reboot my wife's robovac periodically when it starts acting erratic.... But risks of loss are low for that failure.......

And then there are reports of AI having maintenance issues. They received the AI-171 plane in 2012.

Air India Dreamliner made emergency landing after 2023 engine failure

Airliner identical to plane that crashed last week was forced to turn back an hour into flight from Mumbai to London

www.telegraph.co.uk