Air India B787 crash Ahmedabad

[Quickstatus]

Don’t let the facts get in the way for some great speculation!

I dont think it's speculation - AvH reported Govt officials made that comment. Unverified yes, but not an AvHerald speculation

 

[Saab34]

This is India so expect leaks from all corners. If this was China we probably would never know.

 

[mjt57]

Another YT guy, a "Captain Steeeve", is now postulating the theory of "vapor lock". ie. high temps causing the fuel to start vaporising in the lines.

I don't know what the vapor point of kero is or what type of fuel that they were using in that aircraft but it sounds rather extreme.

I wonder how aircraft go flying out of the likes of Dubai, then?

 

[jb747]

Don’t let the facts get in the way for some great speculation!

It would be speculation if we were attempting to narrow down the start point in this accident chain. But, we’re slowly finding, and pointing out, facts. They point to a couple of issues, but don’t come close to identifying the start.

So, known:
Airborne, and at a couple of hundred feet, prior to the end of the runway (FR24)
Rotation rate and angle appear normal (my zillion flight hours)
Flaps are definitely extended to some degree (images airborne and of wreckage)
Gear not retracted but trucks have translated to ‘nose down’ position (in-flight image)
RAT extended (poor image, mainly acoustics)
APU door open (wreckage image)
Mayday call made, referring to loss/lack of power

One would hope that given they found the black boxes, the video footage and there is a survivor should provide information to sort out the root cause of the incident.

The boxes could be expected to answer everything, assuming it’s not a replay of Jeju. The survivor, on the other hand, would be unlikely to offer a great deal of information.

Good pick up. They could have done a Packs to APU take off given the heat. I’m not sure how heavy they were though. We needed to sometimes do it on the 777 out of AUH…at 10am.

Yes, but you did that (as did we in the 747 and A380) because you were reducing the bleed air load on the engines. The 787 doesn’t use bleed in the same way. You can find the reasons for automatic RAT and APU start with a quick search, and they have a lot of overlap.

For the non pilots, we had three options with regard to take off and APU. In order of preference.

APU off, and bleed supplied to the packs from the engines (normal)​

APU on, and supplying air to the packs. Engine bleed off.​

APU off, and packs off for takeoff. Bleed on, but not being sent to the packs.​

Another YT guy, a "Captain Steeeve", is now postulating the theory of "vapor lock". ie. high temps causing the fuel to start vaporising in the lines.

Cold fuel can become an issue, but I can’t see how it could conceivably be hot enough to become one. High temps can certainly ruin the takeoff performance, but 50 or so tonnes of fuel would have an enormous thermal mass to heat up. Plus, like the contamination theory, you’d expect the effect to be somewhat asymmetric, but there’s no rudder evident in the video. I’m not with Steve in most of his commentary. Try Gary Pilot instead.

 

[DejaBrew]

Another YT guy, a "Captain Steeeve", is now postulating the theory of "vapor lock". ie. high temps causing the fuel to start vaporising in the lines.

I don’t think Steve was saying that this was the problem. Rather, he was responding to viewers who’d asked him to talk about it in the context of AI171.

 

[jb747]

If the sequence is interrupted due to hydraulic failure, does the landing gear then maintain the intermediate nose down attitude?

I've not been able to find a definite answer for that. But, if it rotates to that position for packaging reasons, then any change occurring prior to extension could cause it to hang up on part of the structure, and that would impede the alternate (i.e. gravity) extension. Normal Boeing procedure (on other types) has the gear lever being selected to 'off' once the retraction sequence is complete, removing hydraulic power from the gear until it's needed for extension.

 

[kangarooflyer88]

The boxes could be expected to answer everything, assuming it’s not a replay of Jeju. The survivor, on the other hand, would be unlikely to offer a great deal of information.

That's assuming the black boxes got electrical power to log these activities. If the electrical bus on the aircraft was damaged and could not distribute power to the engines and other equipment, that could explain the whole thing in one fell swoop. How likely is it that the electrical bus coughs out just moment after take off? Very unlikely. But then again, when was the last time we had a serious accident involving a 787 resulting in a complete hull loss?

 

[oz_mark]

That's assuming the black boxes got electrical power to log these activities. If the electrical bus on the aircraft was damaged and could not distribute power to the engines and other equipment, that could explain the whole thing in one fell swoop.

It may explain the 'what happened' part, but we're still stuck with why it happened.

Anyway, we haven't heard one way or the other on the black boxes.

 

[jb747]

That's assuming the black boxes got electrical power to log these activities.

TBA on that, though I'd be tempted to say that we might already have been told if it was the same as Jeju.

If the electrical bus on the aircraft was damaged and could not distribute power to the engines and other equipment, that could explain the whole thing in one fell swoop.

There are four high power buses, each fed by a different generator.

How likely is it that the electrical bus coughs out just moment after take off? Very unlikely.

How likely is it that four do so? Apparently at the same time. I think you need to be looking further upstream for your failure.

But then again, when was the last time we had a serious accident involving a 787 resulting in a complete hull loss?

The fact that the fleet has made it to middle age without a loss is good, but without knowledge of what holes there were in this cheese, it isn't all that relevant. How many 787s have more hours than this particular one (or cycles). Is there another crazy counter within the software. This aircraft was part of a manufacturing group that many airlines refused to accept...is that part of the issue? We simply don't know.

This is a Boeing blurb, but it's interesting reading:

787 Electrical System - Boeing 787 Updates

Boeing has formed teams consisting of hundreds of engineering and technical experts who are working around the clock to get the 787 back to flight status, and all of us continue to assist the NTSB and other government agencies in the 787 investigations. Get to know our teams and people.

787updates.newairplane.com

 

[RSD]

It would be speculation if we were attempting to narrow down the start point in this accident chain. But, we’re slowly finding, and pointing out, facts. They point to a couple of issues, but don’t come close to identifying the start.

So, known:
Airborne, and at a couple of hundred feet, prior to the end of the runway (FR24)
Rotation rate and angle appear normal (my zillion flight hours)
Flaps are definitely extended to some degree (images airborne and of wreckage)
Gear not retracted but trucks have translated to ‘nose down’ position (in-flight image)
RAT extended (poor image, mainly acoustics)
APU door open (wreckage image)
Mayday call made, referring to loss/lack of power

The facts as they slowly come out are also helping to eliminate a lot of things - all of the youtubers that put out "pilot error" videos just after the crash to get clicks and dollars should be a bit ashamed of themselves - I think that the F/O raising the flaps instead of the gear idea can be pretty comfortably ruled out now. It sounds like bird strike can also be ruled out too.

 

[RSD]

The fact that the fleet has made it to middle age without a loss is good, but without knowledge of what holes there were in this cheese, it isn't all that relevant. How many 787s have more hours than this particular one (or cycles). Is there another crazy counter within the software. This aircraft was part of a manufacturing group that many airlines refused to accept...is that part of the issue? We simply don't know.

Did QF / JQ accept any aircraft out of this group?

Definitely something pretty weird going on if they lost all four buses at once - will be very interesting to find out what.

 

[Quickstatus]

high temps causing the fuel to start vaporising in the lines.

Flash point of A1 is 38C (lowest temp at which the vapors of liquid fuel ignite when exposed to a flame) But the boiling point is >150C

Middle east temps consistently approaches mid 40C and there has not been a dual engine failure out of those airport.

If there was a vapor lock it would have formed while the aircraft was at the ramp. How quickly would it have manifested given the massive fuel burn at takeoff? - that would depend on the dead space volume in the fuel line between tanks and engine.