Air India 787 crashes on take off 3

[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]

Must admit i know very little about the air cycle machines. Or the difference between bleed air and clean air types.

Most of the fluid is from exhaled breath and pax sweating.

 

[LittleInch]

There's increasing noise about an initial report being issued end this week / early next, but don't expect much other than the simple facts (4/5 pages) seems to be the news.

They still seem to be going for 3 months before issuing anything of depth.

 

[Alistair_Heaton]

https://jtsb.mlit.go.jp/eng-air_report/JA828A.pdf

This had some good information about the 787 aircycle machines.

Boeing 787 Suffers Rare Dual Engine Failure on Landing - The Points Guy

ANA flight NH985 suffered a dual engine failure when it touched down at Osaka Itami (ITM) on Jan. 17.

thepointsguy.com

And a dual engine shutdown on RR engines

 

[Garbage1]

This had some good information about the 787 aircycle machines.

I don't mean to drift off topic with my response to your post, however after reading your link, I did some research, and it appears that Boeing uses air to air heat exchangers for the compressed air-air conditioning/pressuration system. 737 is bleed air feed from engine for air conditioning/pressuration, whereas 787 uses fresh air inlet in front of engines. The images posted below are a 737 example but would expect similar water management as 787. The water collectors/separators are located in the duct system right before conditioned air enters supply side mixing manifold. Therefore a clogged drain line in the water collector, could carry the moisture with the air into the supply mixing manifold where it would collect and perhaps drain or overflow or continue in supply duct towards supply registers? I would expect supply duct to be air tight past the mixer, but not necessarily water tight, and perhaps duct joint separated? This could be one source of rain coming from ceiling of 787 Air India flight.

Your thoughts of hot humid air inside cabin and cold outside temperatures causing condensation on inside of fuselage, seems viable too, however the 787 being a carbon fiber fuselage would provide a better thermal break than aluminum. The other difference I discovered is that 787s manage to a target higher relative humidity goal than typical bleed air systems.

Not the same water problem that potentially could have affected AI171, but another sign of design or maintenance issues on 787s?

 

[TugboatEng]

How is circuit breaker sequencing managed on these types of aircraft? Can a dead short on a load on a distribution panel cause a magnetic trip of an upstream bus-tie breaker? Without sequencing, such a fault may trip both generator circuit breakers simultaneously.

 

[Garbage1]

How is circuit breaker sequencing managed on these types of aircraft? Can a dead short on a load on a distribution panel cause a magnetic trip of an upstream bus-tie breaker? Without sequencing, such a fault may trip both generator circuit breakers simultaneously.

Good Question. I posted a couple of articles earlier about the generator power lug incorrect orientation, could cause a short that would increase load on 1 or more VFSG's.

The Bus Transfers are handled by the "Generator/Bus Power Control Unit (GCU/BPCU)" which decides when to close other BTB's switches, when an excess load is detected on a bus. Normally 4 isolated busses with quick transfer capability. No idea what the software logic is within the BPCU, and if a short on one bus could get automatically transferred across all busses......? But it sure looks plausible.....



This 2016 Service Bulletin addresses software upgrades wGPU /BPCU and other modules. Noting if GPU update not done, loss of electrical power could result. Now this is a very old update, and likely many more since, but loss of electrical power due to software decisions is not new.


I also read where if two generators went down, system wiuld reconfigure automatically to handle load, but with two down system would start load shedding automatically.

 

[TugboatEng]

The short doesn't need to be transferred to other busses. If both generators are on and then busses are tied together, both generators are going to be pushing fault currents simultaneously and their protection breakers may trip simultaneously without software intervention. Perhaps generator circuit breakers should be thermal only.

 

[LittleInch]

The news seems to be that they are taking it to the limit of 30 days to officially release anything.

So 11th July and not much data expected.

This remains very odd. Modern airliners are not expected to simply fall out of the sky without warning.

 

[Alistair_Heaton]

I suspect this is a cultural difference.

I am always surprised how quickly and in what detail some seem to expect information to be given to them when there isn't any reason why there is a need for them to have it.




9 00

 

[LittleInch]

Hmmmm. Not giving any information or officially a to what could have caused a modern plane which hadn't crashed before to seemingly lose all engine power on take off is a pretty big reason to me

 

[TugboatEng]

Isn't the data recorder typically sent to the data recorder manufacturer after such an event? The fact that India hasn't done this reads as if they don't want to know or they're too broke to do it.

We know that the gear retraction had initiated, barely. What is the very next button pressed or action taken after that? Is it something that could cause a dead short if wired incorrectly and cause enough fault current to trip generator circuit breakers?

 

[LittleInch]

Isn't the data recorder typically sent to the data recorder manufacturer after such an event? The fact that India hasn't done this reads as if they don't want to know or they're too broke to do it.

We know that the gear retraction had initiated, barely. What is the very next button pressed or action taken after that? Is it something that could cause a dead short if wired incorrectly and cause enough fault current to trip generator circuit breakers?

TBF, India recently opened a new "state of the art" facility to read these units even when severely damaged so it's difficult to say send it to the USA.

The gear up uses quite a bit of electrical power to power the hydraulics in a 787, so this could have been the initiating cause. Or maybe not. Perhaps it was the rotation of the aircraft.

Or something to do with the transition from ground mode to flight mode.

I think the next action above 400 ft on take-off can be engage autopilot?? Alistair??

So many possible triggers for something that should be totally routine and has been undertaken probably hundreds of thousands of times without both engines deciding to shut down. That's why there is so much interest.

 

[TugboatEng]

We can actually pinpoint the moment the power failed. If you watch this video the 787 landing gear carriage pitches forward and then the belly doors open within one second.

In the crash videos we can see the gear pitched forward but no belly doors are open. In that case I would be very suspicious of a short circuit fault in the belly door mechanism.

 

[Garbage1]

Lowering toes part of landing gear prior to retraction would be relative low electrical requirement to opening doors and retracting landing gear.

Landing gear retraction and stress in root area of wing, happening at same time wings are flexing under takeoff loads.

All this motion stresses electrical wiring paths from generator connections through wing and back to electrical panels.

787 wings flex a lot more than aluminum wings, thus creating more movement related stress and wear on electrical wiring and connections. Thus may shorten MTBF of electrical harness in composite wings vs aluminumn.

 

[Alistair_Heaton]

even turboprops we only lift the gear below 400ft agl. You can be required to turn at 300ft 15 Deg left or right of runway track.

If there had been a fight safety reason due risk of life they would have published something by now. Eg there is a dodgy batch of parts out there in the wild.

My gut feeling is it's human factors maintenance linked with software.

 

[LittleInch]

My gut feeling is that they still don't have anything solid to know why they lost power. Probably then too many alarms going off at the same time to work out what was cause and what was effect.

 

[TugboatEng]

I have a feeling there will not have been any alarms. Magnetic trips on breakers are supposed to occur within 1/2 cycle, no? IAC power on the 787 is generated at up to 800 hz. In that case, a hard fault will open circuit breakers in less than 6 ten thousandths of a second?

Or does the half cycle rule only apply to land based breakers?

 

[Alistair_Heaton]

I suspect so also.

I suspect there were very few alarms.

 

[GregLocock]

Maybe not the airline you want to fly with

Aviation authorities raised concerns over an Air India Express Airbus plane's engine in March.

Air India has been under intense scrutiny since a Boeing Dreamliner crashed in Ahmedabad in June, killing all but one of the 242 people onboard.

The airline has aggressively expanded its international flight network but still faces persistent complaints from passengers about broken armrests and dirty cabins.

Air India budget carrier reprimanded over delayed repairs and falsified records

Air India has been under intense scrutiny since one of its Boeing Dreamliners crashed in Ahmedabad in June, killing all but one of the 242 people onboard.

www.abc.net.au

 

[Cool_Controls]

Apparently most of the circuit breakers in the 787 are virtual, it doesnt seem like any real breakers exist on the flight deck any more.

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