Thread: Air India crash

Originally Posted by Tins

Can't speak to the veracity of this. Can't really say I even understand a lot of it on one viewing, but you may find it interesting. Also the comments.

One huge flaw in the video. The FADECs on the 787 have 3 not 2 power sources. The video is correct in that there are 2 on-board DC busses that supply the FADECs, and yes both of those could have failed for the reasons he outlined. The FADECs on the 787 donks have a tertiary power source, which is a permanent magnet alternator on each engine.

Once those engines are started, all they require is air, fuel and a throttle input. That's it. No different in principle to QF32 where the uncontained turbine failure in #2 severed the control and power inputs to engine 1, which meant it continued to run and could not be shut down (a mate works for RR in the UK and was part of the investigation and remediation process). Once running, it requires a positive signal to the FSOV to cut the fuel supply to the engine. The FSOV is latching and requires a signal to change state. No power, no change state. Even totally disconnected from the aircraft systems, it will continue to run as long as it has fuel. The worst possible outcome is the throttle lever is returned to idle and the engine will respond by powering down to idle. It still won't stop unless something catastrophic happens and it trips the TCMA software. Even an engine at flight idle will still generate both power and hydraulic pressure to control the aircraft and prevent the RAT from deploying. Also, the RAT on the 787 is spring loaded (thus the bang on deployment). It can only be retracted on the ground by maintenance staff, so even if the APU had fired up, the RAT would still be out.

The throttle input is literally a hard-wire from the throttle lever to the FADECs. Not networked and not subject to any other part of the aircraft systems. So it would take physical cable damage to disconnect the link between the lever and the engine.

Now, if both 28VDC busses went down that's going to impact the data recorded by the FDRs, even though the front recorder will have at least captured the cockpit audio because al that has a 10 minute battery backup. But a massive aircraft electrical failure won't have stopped both engines provided there wasn't an issue with the TCMA software. The TCMA is an integral part of the FADEC and there is a lot of speculation around that. The TCMA is only active when both the WoW (Weight on Wheel) and radar altimeters *both* say the aircraft is on the ground. Yes, perhaps a failure there, but the FDR should illustrate that if it was a problem.

This is a complex and nuanced investigation. There is a lot of internet conjecture by people who shoot from the hip.
I'm not an expert by any means, but before I judge a source I tend to do a bit of digging to understand the underlying systems. I'd put a nice bottle of red on this fellow being wrong.

At the moment if I had to posit a theory, it'd have to lie somewhere between a catastrophic simultaneous FADEC software issue or some form of contamination causing thrust rollback and engine failure on climbout. Then again, I'm not a pilot and have about 1.5 hours behind the stick of a Cessna 152, so aside from complex system theory and integration and a couple of years working around Emirates Engineering services, what would I know?

Originally Posted by BradC

what would I know?

More than me, clearly. Thanks for that breakdown. As I said, I can't vouch for any of the vids, which is why I usually say FYI. . I would listen to Juan above most of the pundits, but he is a pilot, not a maintenance engineer, far less a designer. Of course, with something of this nature speculation will be rife until the NTSB report comes along to fill the vacuum. That could take years, although I would expect a prelim in the next few months.

I'm not a pilot either, Brad. Learned to fly in a 150 Aerobat and a Piper PA 28, but do not have a ppl. But flight has always fascinated me. The complexity of modern airliners is intimidating. As John says, we need to hope that this one cannot be laid at the door of Boeing, unless it leads to a restructure of that company and a return to the engineering excellence they were famous for.

One troubling development I have seen, which has nothing to do with Air India or Boeing, is the plethora of AI clickbait videos which have sprung up trying to piggyback on a tragedy to build a YT channel. Life(s) really can get low sometimes. There are plenty of examples of this tactic all over, from  or Android phone "releases" to Sasquatch vids. It's ruining the experience and I wish it would stop. But this one, and the 737 MAX stuff, is beyond the pale.

I'm not promoting the views expressed in this video, posting purely for consideration and discussion.

I won't buy into any clickbait, let alone one that has tucker carlson on it.

We have a small pile of known facts which would all point toward a double engine failure. We have 2 EAFR recovered, both of which are readable. Now we wait.

I thought it was a bit clickbaity, but surely if it was purely speculative or downright untrue, Boeing could crush him legally.
I've never heard of Tucker Carlson, does he have a sensationalist reputation?

Tucker was on the FOX news channel, until they parted ways, and recently went to Russia to interview Putin.

Originally Posted by V8Ian

I've never heard of Tucker Carlson, does he have a sensationalist reputation?

Does the Pope wear a funny hat, a bear **** in the woods or the Trojan horse have a wooden dick?