Overnight the Wall Street Journal reported (paywall) that the Boeing 777 flying as Malaysia Airlines 370 was transmitting data about its location for five hours after its transponders stopped functioning and it disappeared from normal Air Traffic Control coverage. Thus the forensic mystery I mentioned last night -- that there was no evidence that the plane did keep flying, and no evidence that it didn't -- is clarified. It leaves the disturbing mystery of why and where the plane would have been flying incognito.
This is my Annie Hall/ Marshall McLuhan moment for discussing the topic. At the moment I am sitting aboard a United Airbus A320, which (a) is equipped with WiFi, the third such WiFi moment I've ever had in my thousands of hours and millions of miles on United over the years, and where (b) I am sitting next to a dead-heading United pilot, who is telling me what he has learned and thought about Malaysia 370.
Here are several reactions from readers in light of the overnight news. They began with references to the expert I quoted yesterday, Michael Planey, who argued that there would be no point in requiring live-streaming of "black box" data.
Executive summary before we go further: This latest information obviously works against possibilities that the plane vanished from radar coverage because it blew up -- via bomb, some structural failure, missile strike, meteorite, what have you. The fact that the plane kept flying, with its transponders turned off, also works against any "pilot hypoxia" assumptions. (The idea that the pilots somehow both lost their oxygen supply and passed out, as happened in different circumstances 15 years ago in the Payne Stewart crash and in a crash in Greece in 2005.) If two pilots were simultaneously nodding off at the controls, there is no reason why their last conscious act would be to disable the transponders -- rather than radioing for help, descending into thicker air, reaching for the emergency oxygen bottles, etc. Possibilities involving deliberate destruction -- by the flight crew on its own, or by attackers who got control of the plane -- thus become more likely.
Now, the details. I am erring on the side of leaving in all the arcana, since cases like this often turn on precise interpretation of specifics.
1) On how the whole reporting system works. Reader John Shepley, who has experience in the data-reporting business, writes in to say:
Mr. Planey's analysis is mostly correct, but it was written before the knowledge we now have - that the plane did have electrical power as indicated by the registration 'pings' that the ACARS transmitter periodically sent to the satellites, even though the transmissions did not contain any data. (The operation is similar to the way that cell phones periodically transmit a registration signal to the nearest cell tower, even if the user is not using the phone at the time. That's how inbound calls can find the mobile phone.)
The satellite transceiver, such as the Rockwell Collins SAT-2100 is a metal box that sits in an avionics bay - not accessible from the cockpit. It receives the information that it transmits over a data bus from a control unit that is a similar box. A panel in the cockpit provides control functions, allows the pilots to tune the various radios and manages the many functions that the system performs.
A typical system looks like this:
It's likely that there is no power switch in the cockpit for the Satellite Radio or the VHF datalink radios.As seen in the diagram the CMU-9000 boc collects the data fro the GPS and other sensors and formats that data and sends it to the selected transmitter(s).
Commercial airliners don't typically carry HF radios which have a very long range, and are used mostly for polar regions. The VHF data radios would have an antenna on both the top and the bottom side of the aircraft, allowing line-of-sight transmissions even of the plane is in a steep bank or dive. The satellite radios would have an antenna on the roof of the aircraft that would certainly lose coverage if the plane were in a very steep bank or dive. While cockpit-accessible devices such as the transponder and messaging / control unit have power switches and can be turned off, the out-of-the way boxes are probably powered up whenever the aircraft's engines are running..
The voice recorders can provide more information than just the conversations in the cockpit. Several audio streams are recorded: One each from the pilot's and first officer's headset microphone, one or more wide field microphones that would pick up the ambient noise in the cockpit, and any radio or intercom communications. The ambient sounds can be particularly useful and can be used to determine an approximate origin of a loud noise. For example, if an engine compressor exploded in the right-side engine, the sound would reach the first officer's microphone a tiny bit sooner than it would reach the captain's microphone. These sounds and the subtle differences as recorded by each microphone can be analyzed and provide useful clues to events on the aircraft.
Given that we now know that the satellite radio did periodically ping the satellites and therefore, the plane continued flying for 4 hours, my bet is on the idea that someone took control of the cockpit and turned off the transponder and other cockpit equipment.
2) "It would at least tell you which ocean to be looking in." From another person in the industry:
I'm a former ARINC engineer, still working in the business of aircraft communications and wanted to correct a lot of disinformation out there, some of which made it into your most recent article.
Michael Planey makes some good points but he doesn't seem to understand the types of communications systems that a modern airliner has and the different types of satellite links available.
1. ACARS data can be transmitted automatically off an aircraft one of four ways: VHF ACARS operating at low speed data to line of sight ground stations, VHF ACARS at high speed using VDL Mode 2 to line of sight ground stations, ACARS over Iridium satellite using short burst data, and HF ACARS where the data is transmitted by ionospheric propagation to one of several ground stations around the world.
2. Iridium satellites operate in low Earth orbit, and links to them do not require high gain directional antennas that are aimed at a particular spot in the sky. A low gain nondirectional antenna on the aircraft would still likely be able to reach an Iridium satellite regardless of the aircraft attitude (ok, maybe, maybe not if inverted). An aircraft in a dive would almost certainly still be able to reach one of the several Iridium satellites overhead.
3. It would be trivial to have all airliners send out a NMEA-coded GPS position report at periodic intervals (1 minute, 2 minutes, 10 minutes? whatever you want) on any of these links if an airline wanted to (or was required to) and transmit them to the airline operations centers or to an en route air traffic control facility (this is what will be coming with newer controller-pilot data link technology).
4. This isn't done because of the cost, not because of the technology. Airlines don't see a need for this and are reluctant to pay for it. That's really it. It is all about the economics. 99.9999+% of aircraft make it on these routes without incident and no companies want to pay costs for communications across the board that don't help their bottom line. Contrast this with how eager they were to know precisely when aircraft lifted off and set back on the runway so they could track crew flight hours (the original business case for ACARS) or tracking engine performance data so they can fix problems early before they become serious and costly. Now, if someone else paid for it they would probably do it.
One thing that would be interesting would be to see that if there had been any ACARS over Iridium messages whether they included any routing information (headers?) that would give the time of the message transmission and the identity of which Iridium satellite originally received it. Since these are LEO satellites that each cover a small part of the Earth, knowing which satellite and what time would allow us to know where that satellite was at the time and its coverage area and potentially narrow down the search area. It would at least tell you which ocean to be looking in.
3) Similarly, in a note that came in before the latest news.
"In that [Air France] case, some system failure reports and warnings were transmitted via ACARS [JF note: a data transmission system linking in-flight airplanes with ground stations] in the last moments before the aircraft crashed into the Atlantic."
"In the current case of MH 370, the same type of location data is available, but the search has been fruitless. "
That's not true. There is no way to know when MH370 crashed into the ocean, or even if it did. While they may not have known exactly where the wreckage of AF 447 was, I think people were certain it crashed into the Atlantic. The same can not be said for MH 370; we don't even know if it crashed into the ocean...
Planey assumes the only way for a plane to transmit data when out of range of land-based communications equipment is via satellite, and that that medium may not always be available in disasters. First of all, not all crashes would be preceded by satellite-disabling failures, so there would still be value in having access to that information. Also, I think there could be other ways for planes to transmit information, just like a radio station or shortwave radio. We would just need receivers scattered around the world continuously recording broadcasts of the relatively low bit-rate data. I don't think that would cost billions of dollars.
But I do agree with your headline, this is profoundly mysterious.
4) More robust flight tracking. From a reader who agrees with Mr. Planey's main argument: that there would be no point in requiring live-streaming of "black box" data.
I agree about the streaming of black box data. It would be hideously expensive, and black boxes are (at least until now) invariably found.
But I hope this episode (regardless of how it ends) leads to more robust flight tracking. It really is not acceptable that airplanes can vanish over water any more; there are simply too many flights over water, and the incidence of catastrophic events on such flights seems to be once every few years, if this and AF447 are any guide. It does not appear that the combination of ELTs and underwater pingers is nearly reliable enough to dependably locate the site of crashes into large bodies of water.
The structure for such tracking is largely in place with all large modern transports fitted with ADS-B; the remaining tasks seem to be around the robustness of the tracking.
5) On Malaysia. Disasters often have entirely unforeseen political and social effects. Chernobyl, Katrina, the Fukushima nuclear breakdown -- these all became shorthand for points about institutions in those countries and their newly revealed vulnerabilities. A reader in Asia introduces a point that's been on my mind, especially considering my oft-pronounced and sincere enjoyment of Malaysia and its people in the years my family lived there. The reader says:
I've lived/worked there 2X. I like it. the people, country, and most of all, food.
But they have serious problems. In two decades, they're falling behind in the region. To me, its 'crony capitalism', which exists in Indonesia as well (lived/worked there for almost 2 yrs)
This is going to be a millstone around their necks for the immediate future. And it was all preventable-if they had just been honest WITH THEMSELVES.
There is a lot this last note implies that needs to be more fully explained for people unfamiliar with Malaysia's strengths, weaknesses, and similarities and differences with Indonesia. That will have to wait for the next time. Thanks to all who wrote in (and thanks to United for ever-so-slowly closing the WiFi gap with Delta, Alaska, and other airlines).
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