Essentially there are two companies, Immarsat and Iridium. Immarsat is the better of the two and offers a much better path to support the move from ACARS (which is painfully outdated) to ATN. The provider associated with a particular airplane is associated with the gear installed on board. I'm not nuts and bolts enough to know that end of the business, but I know that if an airline switched from Immarsat to Iridium, they'd have to rip out some gear and replace it with other stuff.

The actual sat link is very low level -- think of internet backbone companies. I believe that the airlines actually buy from intermediaries which would be like your ISP -- called CSPs in airlines (Communications Service Providers). Big CSPs are ARINC and SITA.

My favorite ACARS tidbit is that there are two flavors, POA and AOA. An engineer explained to me that POA meant "Plain Old ACARS" and I thought he was bull****ting me, but apparently that is the truth. AOA was ACARS over something (some kind of alternate and better radio).

It is my impression that every US based airline has sat hookups for their planes. If not every plane they fly, certainly every ETOPS bird. Until this episode, I didn't realize that foreign carriers went dark over water.

This isn't exactly right either. Engine health data is one of the things that would be transmitted over the network, just like ACARS data and company specific messaging traffic. The comm gear itself is mounted in the fuselage.

One possible source of confusion (and I have no specific knowledge about this at all) is that the satellite companies aren't the only people who have a keen interest in monitoring sat transmissions. There are parts of the world's intelligence communities who are very adept at collecting satellite communications and recording them. It is at least possible that someone in this world initially identified the transmissions and pointed Immarsat at the information (or even had Immarsat claim that it was their own analysis to protect the true source of the information).

This is correct (I'm learning to accept that people are going to call it a ping). The gear is normally mounted aft, but probably varies by type.

The fire theory requires a lot of coincidences. jjshabado has pointed them out already, but the one that I have a really hard time believing is the ATC handoff.

To believe the fire theory, you have to believe that the communications were damaged within a VERY short time frame (perhaps just a couple seconds) -- between "all right good night" and when they should have checked in with the next ATC person.

That, combined with the other things mentioned, makes the fire theory a longshot imo.

I think pilot suicide is the most likely explanation given the info we have right now.

NoSoup4U, very interesting stuff.

How is this stuff exposed to the pilots (if at all)? I assume there has to be circuit breakers and stuff available for it since you'd think there would be a way to disable it in case of an electrical issue.

W0X0F would be better to ask than I. I would assume that any gear that is in the cockpit probably has a mechanism to turn it off or disable it in the event of a fire. I'm more of a computer / network guy, I can't even splice a wire.

In the implementation I'm familiar with, the low level sat gear would be mounted in a cabinet connected to the rear galley. Crew could access it and shut it down in the event of a fire (although they'd presumably just blast it with an extinguisher). I don't think the pilots could shut it down without coming back to the rear of the plane.

I suspect that this kind of low level information (that the plane continued to send an authenticating transmission periodically to the satcom) would be something that virtually no pilot would have known before this incident. It just isn't the kind of thing they'd usually need to know or care about.

Apparently France used a space-based radar system to identify debris from the crash.

Seems to me like everything changes if it turns out the stuff about the plane's route and route plan turn out to be misinformation. While some things are more believable than others (the ping data is solid), it wouldn't be surprising at this point to find out any supposed facts turn out to be bogus.

I was on board with it being some kind of human action 100%, but I think some kind of catastrophic occurrence has gained massive equity in the last day or so with a hypoxia-related event being most likely.

Basically, ChrisV has pretty much owned this thread and has probably been the best person on the internet for interpreting the information. I just wonder how many "facts" he is working with will turn out to be false.

Pretty cool but I would assume a few countries have that, whether they talk about it or not.

The main problem with the hypoxia theory is that my understanding is that it doesn't last long (before being incapacitated) and the pilots turned off a bunch of stuff and changed course without making any strange communications or doing anything that would crash the plane.

Agreed its possible but I'd still put it well below foul play.

Thanks. Yeah it's annoying how many apparently credible facts are later walked back. I'm tinfoiling about this one a little still because I don't see how such a specific thing gets completely made up, but I'll accept that it's true for the moment.

I think think human action is by far the most likely since the facts which are a huge problem for other theories (no attempt to contact the ATC they were handed off to, no mayday call, transponder going dead 2-3 mins after last ATC contact) are exactly what we would expect under a human action theory. The only mystery under the theory that a pilot flew the plane out into the middle of the ocean to hide it is why he would want to do that. That is admittedly a big mystery, but I'd rather have a theory that has one completely baffling mystery than one which has like 5 of them.

I also put a fair bit of weight in the fact that everyone investigating - including Malaysian authorities, who have a large incentive to invent some accident theory of why the plane went down - have human action as almost certain. This means that whatever the actual facts of the case are, they obviously support a human action theory pretty strongly.

Yeah foul play still the lead theory for sure, but since there's only circumstantial evidence of it now, gotta consider other possibilities.

This thread has taken a decidedly good turn for the better. Thanks for joining NoSoup and keep up the fine work jj and Chris.

From what I understand the voice recorder saved on the black box is for a limited time frame. Since the plane continued to fly for hours, it's unlikely the black box will have voice recordings from when the problem arose.

That's right, I think all the stuff on the black box is like that. We may never know then.

It's true but on a 777 there will likely be enough data on the data recorder to tell us if it was on purpose or not. Things like if anybody was giving the plane commands, if systems failed, in what order they failed/were disabled, and so on.

It's pretty crazy what they can reconstruct from this data.

I think the boxes contain much more than just voice recordings. Things like what altitude they were at, what systems were running/not running, whether systems failed or had false readings, whether they were turned off/on by a person or system failure, fire warnings, decompression warnings etc.

Plus the wreckage itself may hold clues as to whether or not there was a fire or explosion.

I asked upthread, but - what's the procedure for trying to find this plane if the 30ish days pass when the transponder stops sending out pings?

There are two separate boxes. One is the voice recorder, it's the one that only records for a limited amount of time (30-120 minutes being the common lengths). Although I certainly wouldn't rule out the ability to recover some audio that was overwritten.

The second black box stores data about the plane. This records for a much longer period of time and will probably have everything from before the flight took off.

Yeah. I was just saying they are not likely to get anything from the voice recorder like "omg fire" or "omg terrorists."

or "omg I don't want to live"

Or "omg aliens"

Unless performing an ATC handoff has some fire suppressing qualities the chance of it happening then is the same as the chance of it happening at any other time

The underwater locator beacon doesn't actually stop at 30 days. The specification requires that the battery pack be tested to provide a minimum of 30 days of pings at the end of its rated battery lifecycle (which will be something like 6 years). If the battery is newer, it could conceivably last quite a bit longer. I'd imagine that colder temps would extend the battery life as well.

They found the AF recorders a couple of years after the crash. They are more likely to find a debris field than the beacon anyhow.

I don't think you understand his point.

I will say though that W0X0F outlined a number of innocent explanations for why pilots sometimes miss the handoffs. It's still a circumstantial piece of evidence that it was malicious but it's far from definitive. There could be situations where the crew misses the hand off for unrelated innocent reasons and that increases the window of time that something could have gone wrong.

even if they find the black box it is not going to help because the alien could have disguised his voice an pretended to be the pilot.