That air crash in Ahmedabad

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The first hull loss of a Dreamliner happened two days ago, with one survivor walking away from the wreck and the canteen of a medical school hostel crushed beneath it. The Dreamliner was only in the air for thirty seconds, there's no sign birds hit it, but everything points to both engines having stopped after getting airborne. By which I mean it got off the runway at the right place with the right rate of ascent, it reached a maximum of just 650 feet without successfully retracting the wheels and from there drifted as gently as it could to the ground, engines apparently silent, external emergency generator deployed and a Mayday "no thrust, losing power, unable to lift" having been sent. It's hard to think of what might have made that happen, the electrics aren't meant to totally collapse and no other plane that day had issues with fuel contamination. One passenger flying just the previous leg was so bothered about the electrics that she tweeted about it, which is extreme - she said passengers were reduced to reading the flight magazine because the seat display screens were off, along with the air conditioning.

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I expect the black box readout will be close to announcement.

It got remarkably little distance. The take off appeared perfectly normal. If both engines lost all thrust just after the plane began its ascent, there's already enough kinetic energy to get it to the top of the climb that was achieved. In which case, since we don't like coincidences, the start of ascent or the start of lifting the landing gear is relevant to the loss of all electric power on the distribution systems - hence the deployed generator - and the immediate loss of fuel to the engines, and the incomplete stowing of the landing gear. None of those are trivial issues, they're the sort of events that redundancies are meant to prevent. And the mayday suggests the pilots had no indication of why it had happened, just what.

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And as of yesterday, with no official announcements, the interweb is packed full of "fuel switches" posts. As in the two fuel switches, which are safe-proofed by requiring lift from the hole before moving to the off state, both ended up in the off state. And everyone is consequently speculating this is not something anyone should ever have caused to happen, least of all just after a successful take-off.

And it does indeed fit all the listed issues.

The weeks of refusing to comment, when the black box recordings have obviously been transcribed and analysed, is not a sensible protocol.

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Well. The preliminary report is out.

The aircraft air/ground sensors transitioned to air mode, consistent with liftoff at 08:08:39
UTC.
The aircraft achieved the maximum recorded airspeed of 180 Knots IAS at about 08:08:42
UTC and immediately thereafter, the Engine 1 and Engine 2 fuel cutoff switches transitioned
from RUN to CUTOFF position one after another with a time gap of 01 sec. The Engine N1
and N2 began to decrease from their take-off values as the fuel supply to the engines was cut
off.
In the cockpit voice recording, one of the pilots is heard asking the other why did he cutoff.
The other pilot responded that he did not do so.

[...] As per the EAFR, the Engine 1 fuel cutoff switch transitioned from CUTOFF to RUN at about
08:08:52 UTC. The APU Inlet Door began opening at about 08:08:54 UTC, consistent with
the APU Auto Start logic. Thereafter at 08:08:56 UTC the Engine 2 fuel cutoff switch also
transitions from CUTOFF to RUN. When fuel control switches are moved from CUTOFF to
RUN while the aircraft is inflight, each engines full authority dual engine control (FADEC)
automatically manages a relight and thrust recovery sequence of ignition and fuel introduction.
The EGT was observed to be rising for both engines indicating relight. Engine 1’s core
deceleration stopped, reversed and started to progress to recovery. Engine 2 was able to
relight but could not arrest core speed deceleration and re-introduced fuel repeatedly to
increase core speed acceleration and recovery. The EAFR recording stopped at 08:09:11
UTC
At about 08:09:05 UTC, one of the pilots transmitted “MAYDAY MAYDAY MAYDAY”.

https://www.gov.uk/government/news/aaib ... ight-ai171

So, the two fuel cutoff buttons were at OFF for ten seconds before being pushed back to RUN. The engines had insufficient time to regain thrust before the the crash.

The implication of the voice recorder is that neither pilot said they were responsible for the movement to OFF. One explicitly denied it, the other asked why the switch was at the wrong position. Neither accused the other of moving the switches.

If they're to be believed, and there's no reason not to believe them, something three seconds after lift-off caused the switches to move. There's no indication anyone else was in the cockpit.

The switches are independent of each other. Both moved, a second apart. They're meant to be mechanically protected from inadvertent bumps or pressure of any sort.

All of that was known two weeks before the report released it into the public domain. The frenetic online speculation over that period was the direct consequence of that systemic secrecy.

Today marks a month since the crash.