The SDU Re-logon: A Small Detail That Tells Us So Much About the Fate of MH370

MCS 6000
The Honeywell/Thales MCS6000 Satellite Data Unit is the middle of the three boxes shown here.


One of the peculiarities of the MH370 mystery is that, while we have only a very small handful of clues about the fate of the plane, some of them often get overlooked due to their highly technical nature. Today I’d like to revisit a topic that I’ve touched on before but which I feel continues to be get short shrift: the re-logon of the  MH370 Satellite Data Unit, or SDU. Just on its own, this little data point tells us a great deal about what happened to the missing plane.

First, some basic background. Flight MH370 took off from Kuala Lumpur International airport at 16:42 UTC on March 7, 2014 bound for Beijing. At 17:07:29, the plane sent an ACARS report via its satcom. At 17:20:36, five seconds after passing waypoint IGARI and a minute after the last radio transmission, the transponder shut off. For the next hour, MH370 was electronically dark. The next ACARS transmission, scheduled for 17:37, did not take place. At 18:03 Inmarsat attempted to forward an ACARS text message and received no response, suggesting that the satcom system was turned off or otherwise out of service. At 18:22, MH370 vanished from primary radar coverage over the Malacca Strait. Three minutes later the satcom system connected with Inmarsat satellite 3F-1 over the Indian Ocean and inititated a logon at 18:25:27.

The question is, by what mechanisms could MH370’s satcom have become inactive, then active again?

Logging on and off the satcom is not something airline pilots are trained to do. A pilot can deselect the satcom as a mode of transmission for ACARS messages so that they go out over the radio instead, but this is not what seems to have happened in the case of MH370. According to the ATSB report issued in June of 2014,

A log-on request in the middle of a flight is not common and can occur for only a few reasons. These include a power interruption to the aircraft satellite data unit (SDU), a software failure, loss of critical systems providing input to the SDU or a loss of the link due to aircraft attitude. An analysis was performed which determined that the characteristics and timing of the logon requests were best matched as resulting from power interruption to the SDU.

Like most of us, I’d never heard of an SDU before MH370 happened.

It’s a piece of equipment which processes the signals that are transmitted and received between the plane and the satellite network. The SDU lives above the ceiling of the passenger cabin, toward the back of the airplane, near the rear emergency exit. The reason it’s there is that in order for it to work efficiently, it needs to be located as close as possible to the satellite antennae, which protrude from the top of the airplane just above it. Imagine an electronic version of an old-timey ham radio operator sitting underneath a radio tower. Bear in mind that the SDU doesn’t generate information per se; it’s just providing the link between the aircraft and the satellite. A useful analogy is to think of your smart phone. When you turn it on, it connects to the cell network, but it doesn’t communicate with anyone until you send a text message, make a phone call, or activate an app.

The SDU is a very important piece of equipment in the MH370 saga because the seven pairs of BTO and BFO values, which together comprise all that we know about the final six hours of the flight, depend on computations carried out in the SDU.

How could the SDU power interruption have occurred? For one thing, it couldn’t have happened accidentally. Independent researchers have spent months trying to figure out a way that the SDU could have logged off and back on again without human intervention, without success. So it must have been intentional. However, there is no on/off switch for the SDU in a 777 cockpit. A person wanting to turn the SDU off has two options. The first is to descend into the electronics and equipment bay (E/E bay) through a hatch at the front of the first-class cabin and flip three circuit breakers located there. I call this the “easy way.” The second method, which can be accomplished directly from the cockpit, is to isolate the portion of the plane’s electrical system which feeds the SDU, the left AC bus. I call this the “hard way.” Since it’s quite complicated, I’d like to discuss it in greater detail.

According to IG member Barry Martin, the left main AC bus can receive its electrical power from any one of four sources:

  • left main engine IDG via a left generator circuit breaker
  • right main AC bus via both left and right bus tie breakers
  • auxiliary power unit generator via an auxiliary power breaker and the left bus tie breaker
  • backup generator converter which connects to the left transfer bus via a left converter circuit breaker, and the left transfer bus connects to the left main AC via a left transfer bus breaker.

In order to prevent any of these from supplying electrical power, Martin writes, a multi-step process is required:

The left IDG can be disconnected in a couple of ways via the flight deck electrical power system control panel. The preferred method would be via the left generator control switch. The second method is by use of the guarded drive disconnect switch, which permanently disconnects the IDG and the connection can only be remade on the ground. The L GEN CONT switch will open the left generator circuit breaker, but the left bus tie breaker would then automatically close to re-energise the left main bus so the left BTB must be switched to ISLN on the electrical control panel before attempting to disconnect the IDG.

The left main bus can still be powered from the left transfer bus which picks up power from a solid-state variable-speed constant-frequency backup generator converter. The easiest method of preventing this is by simply opening the left transfer bus breaker, which allows the left transfer bus to remain energised to ensure the left transformer rectifier unit stays powered. However, I don’t see an option on the flight deck control panel to manually open the left transfer bus breaker. A second option would be opening the left converter circuit breaker, connecting the left transfer bus to the backup generator. Again, there’s no L CCB switch on the panel. Therefore the third option is to switch both backup generators off, which is possible via the panel.

This explanation is somewhat above my paygrade but my takeaway is that isolating the left AC bus requires some technical savvy—indeed, technical savvy beyond the ambit of 777 pilots. When I asked Patrick Smith, a 777 pilot who is one of the most well-regarded aviation commentators in the US, about the SDU reboot, he replied, “The what?” After I explained, he answered: “There isn’t a 777 pilot alive, I’ll bet you, who has the remotest clue as to what the SDU is.” I’ve brought up the topic with many other 777 pilots I respect and have gotten essentially the same response.

I would add that while it seems clearly possible to power the SDU on and off my isolating and then reconnecting the left AC bus, to do so would be a risky undertaking. In a fascinating blog post on an airline pilot who goes by the handle “Ken” describes going through a simulated left AC bus failure in the course of a training session. He notes that among the systems lost were Window Heat (Left) and a Primary Hydraulic Pump (Left). “No biggie,” he writes, but adds that in addition:

…there are a whole host of ancillary services lost. Many of these are reflected by the amber lights on the overhead panel. Having looked at the roof – you later discover even then that it’s not the whole story. In this particular scenario we decided to return to KLAX. Part of the return process was fuel jettison down to maximum landing weight. Guess what? Without the Left Bus – the main tank jettison pumps are failed. You’ll be advised of this… when you start the fuel jettison. I didn’t give this a second thought… but the discussion we had afterwards that included a talk about this little quirk of the Boeing EICAS/ECL was interesting. There are no EICAS/STATUS messages to advise you of everything you’ve lost, and in many cases, until you attempt to use something that’s failed – you won’t know about it. Older aircraft used to publish a Bus Distribution List (Electrical and Hydraulic) so that you’d know exactly what you’d lost with a particular electrical bus failure – but not on the 777. My fellow pilots were vaguely disturbed by the lack of information.

It’s not impossible to imagine that one of the pilots cooked up a plan that involved switching off the satcom by isolating the left AC bus, but to do so they would have had to do intensive research into the issue, without any way of knowing if their research was complete. “ It can be difficult to find out just what equipment is powered by a particular bus,” says Smith, “so if you start isolating buses you’ll likely wind up shutting down things you don’t mean to or expect to.” All told, this would be a complicated and risky strategy.

And to what end? Why would anyone want to depower the SDU anyway?

One might imagine that the SDU was powered down for the same reason that the other forms of electronic communication were shut down around the time MH370 reached IGARI: to slip away from ATC surveillance in order to pull a 180 and slip away undetected. One doesn’t need to depower the SDU to go dark, however.  If the satcom was deselected for ACARS and the IFE was switched off (both of which are easily accomplished from the cockpit) then there would be no reason for a pilot to fear that the satellite would give away his position.

Some have raised the possibility that whoever took MH370 didn’t want to turn off the SDU per se, but wanted to turn something else that was on the left AC bus and wound up taking the SDU along with it as an uintended consequence. If so, the crucial question then becomes: What else is powered by the left AC bus? It wasn’t easy to find out, but after months of painstaking digging, a number of independent researchers were able to collectively determine that some of the other systems fed by the AC bus are:

  • TCAS (Traffic Collision Avoidance System)
  • Cockpit door lock
  • The centre tank override and jettison pumps
  • Some galley equipment
  • IFE (in-flight entertainment system, which includes passenger satellite phone service)
  • One of the high-frequency radios
  • The main passenger cabin lighting system (the night, cabin and cross-aisle lights remain powered)
  • The Cockpit Voice Recorder (CVR)

There is only one piece of equipment on this list that someone who is in the process of stealing a plane might be strongly motivated to shut off, and that is the cockpit voice recorder. Recall that in December, 1997, the pilot of Silkair Flight 185 apparently got up out of his seat and pulled the circuit breakers for the CVR before returning to the cockpit and flying the plane into the ground. Because the CVR wasn’t working, investigators couldn’t tell exactly what happened in the cockpit in the moments before the crash, so the pilot’s guilt was impossible to establish conclusively. Which presumably was the point.

The idea that MH370’s pilot isolated the left AC bus in order to shut down the CVR is problematic, however. For one thing, it would be far simpler to depower the CVR the “easy way,” by going down into the E/E bay and pulling the circuit breakers. But maybe the pilot had locked the co-pilot out of the cockpit, and so wasn’t free to leave to go down into the E/E bay? In that case, isolating the left AC bus would have had the reverse of the desired consequences. Anyone savvy enough to know how to depower the left AC bus would also understand that the CVR over-writes itself every two hours. Therefore cutting power to the CVR would result in the preservation of the recording of whatever was said and done when the pilot talked the copilot out of the cockpit and locked the door.

Of course, if the pilot planned to fly the plane six hours into the middle of the southern Indian Ocean, he’d have no reason to shut down the CVR anyway, since its contents would be come erased during the long flight into oblivion.

To sum up, the fact that the SDU logged back on with Inmarsat three minutes after leaving primary radar coverage is one of the most significant clues that we have to the fate of MH370. By itself, it rules out the possibility that MH370 went dark due to fire or electrical malfunction (which remains a popular theory despite being impossible for several other reasons as well) and it strongly suggests that the plane was not hijacked by one of its own pilots for the purposes of committing suicide (another popular theory). Instead, the SDU re-logon suggests the plane was taken over by a passenger or passengers with a sophisticated knowledge of aircraft electrical systems.

This may well be one of the reasons that the French judicial authorities are treating MH370 as a terrorist investigation.

131 thoughts on “The SDU Re-logon: A Small Detail That Tells Us So Much About the Fate of MH370”

  1. @Gysbreght

    For once I am agreeing with you on something.
    Yes, it would obviously be quite an easy thing to isolate the LH Main AC bus from the cockpit. A senior captain with many years experience on the type – you would expect him to know what every switch was for, what was possible and what was not.

    Now the Boeing design philosophy: due to the level of automation and redundancy on the B777, the designers moved a lot of circuit breakers from the cockpit, and put them in the EE bay, so that flight crew couldn’t meddle with them. So it follows that all the circuit breakers and switches still located in the cockpit are there because the flight crew might need to use them in an emergency. It naturally follows that the pilots would probably want to know what can and what cannot be controlled from the cockpit.

  2. @Jeff. In addition to the sdu I think we should look at the entire electrical system for clues including the transponder. Time sequencing their behavior may help us to see what is increasingly looking like a hijacking. Remember in 911 the transponder shut off just seconds after the last radio contact.

  3. @Nederland

    Re the IFE question: Yes, If the LHMain AC bus supplies the IFE, then it is logical to assume it also supplies the surveillance video system, as power to them is routed through the same switch.

    So the follow on question might be; would the video surveillance cameras (and the IFE) remain powered up if a backup generator was the sole source of electrical power?

    Agreed, as many if not more questions than answers now on the significance of the 18:25 SDU log on.

  4. @ DennisW
    I don’t have a credible link, but I follow this from day 1 and I never saw a single photo of a passenger boarding the plane or a person settled in a seat. Friends and relatives would have shown the messages and photos they had received from the plane. It could be explained by the human trafficking scenario I mentioned. Or the plane was already taken over on the ground and the passengers handed over their devices upon entering the plane. The latter would suggest there were more than just one or two hijackers on board. If so, it’s very unlikely that investigations on the ground did not come up with anything. I would think the total ‘silence’ also speaks against a technical failure at waypoint IGARI. People would have behaved ‘normal’ until the supposed failure incident occured. The pilots sounded normal in the beginning. Could it be they only realized the plane was taken over at IGARI?

  5. @ROB

    It could also be the other way round: the hijacker(s) (whoever it was) needed to restore power to get the surveillance camera going or to switch the intercom on, couldn’t it? Perhaps in response to passengers or crew trying violently to gain access to the cockpit.

  6. @VictorI you wrote: Falsified satellite data would require the complicity of Inmarsat. The acceptability of this scenario correlates to acceptability that Inmarsat is dishonest.

    Not necessarily, IMO. The data > 18:25 might have been manipulated ex post or inserted into Inmarsat’s systems without them realizing it, at least for the time being. This could have been accomplished from inside their networks by individuals with access to the data or even from outside, depending on network hardness (which is very hard to assess for us). In both cases there were no need to put into question the honest effort of those people at Inmarsat which were involved in the case.

    If it actually happened and they figured it out later we would for sure not have heard a single word about it. I can readily imagine the “big bang” that would have occurred if they had to admit it after so much effort and money have been spent on the search, mainly based on the data provided by them.

  7. @DL

    If the few items are to be found then i know what happened. If there is nothing down there then i dont know what happened.

  8. 1/left ac breaker could have triped .
    due to electrical fault creating smoke and turned back on by pilots when smoke disapated . left ac breaker could have been interperated as air conditioning breaker.

  9. @Oleksandr

    1> Pure statistics. Data shows only 20% of hull losses are due to aircraft failures of all kinds.

    2> Item 1> above is further reduced by the aircraft remaining flying for several hours.

    3> No communications of any kind since IGARI. There was ample opportunity to communicate a malfunction event.

    An aircraft failure is so remote given what is known about this flight that it can be safely discarded from consideration. A complete non-starter for me.

  10. @ROB

    >But don’t you think it’s rather coincidental that he was working on a door when in a few hours time he would be using one to hijack a plane?

    You clearly have not given enough serious consideration to the many ‘coincidences’ to be found in Zaharie’s youtube video productions.

    All joking aside, they are a treasure trove. If you really have not taken more than a passing interest, have a go. One little nugget, verbatim: “Jet wash”.

  11. Oleksandr

    ”Why? Frankly, I think what you summarized in your excellent paper, makes a technical failure even more plausible than ever before.

    Didnt you claim the japanese space rocket part found near thailand was part of MH370 cargo door (with rest of the aircraft flying to the SIO) ?

    Why stick to the ”technical failure” scenario ? But i admit i prefer this theory over the spoofing nonesense.

  12. I believe the passengers were loaded onto a military type plane thinking they were loading MH370 and were brought to safety, MH370 was flown out to nomansland because of whatever was in the cargo bay!

  13. @DL I agree , my years of flying around China and the rest of Asia , the whole row would be lit up with cell phones on taxi and take off and hidden when attendants passed by . As a EMC instrument guy this behavior scared the … out of me ! Therefore if no-one made any calls/text it would be most a unusual flight.

  14. I think Jeff would know what I meant if I said the media is beset with intellectual laziness like never before, and he is the only one I know of happy to dig into the the issue of the reboot. It’s the second big pivot in the story – the turnaround being the first. The msm has done a hands off with the second, I believe because the official narrative remains comparatively coy on the subject.

    Imagine being a detective on this trail. Is it a simple step to conclude it was deliberate interference, in light of everything else that went on? It’s accepted at high levels the plane was diverted yet plenty of crunchers were happy to go technically in depth to account for the reboot as incidental loss of power among others things. The behaviour of the plane does not point to cascading issues or on-board calamity; it’s points to the opposite.

    If you were planning to take a plane with stealth you would need to do some homework on the SDU(wherever it was) – even I would know that. But the fact that it coming back on did not seem to bother the ISAT purists, bothered me a lot. Especially the timing, then the turn. To an investigator it’s a plank in the head.

  15. @Gysbreght,JeffWise,

    Barry Martin’s assertion that the Left AC bus can be powered by the Left Transfer bus is wrong!

    To isolate Left AC:

    – L GEN CTRL L Main switch to OFF
    – L BUS TIE switch to ISLN.

    That’s it!


  16. I rather like Gysbreght’s reference to a hijacker wanting to restore power to the A/C bus and thus re-energize the galley to secure a cup of coffee. Funny.

    If cutting power to the SDU was an element of the hijacking, the pulling of the three breakers in the E/E bay could conceivably have been done as a precautionary measure, ensuring that could not be any satellite communications originating from the aircraft, either from the the flight deck or the IFE system. In other words, Jeff’s “easy way” of cutting power to the SDU would likewise be the “easy way” of ensuring silence.

    From here, we know that the hijackers most likely did not reach their intended destination, and that thus their efforts did not culminate in their intended outcome. This, then, would have us logically suppose that there must have been a dynamic event that upset the “hijacking equilibrium”; namely, an attempt was made to retake control of the aircraft. This could have included a descent into the E/E bay (its violation by one of the hijackers having had been witnessed by a crew member or passenger), to investigate what would have been meddled with. The pulled breakers could then have been discovered and returned to their on positions.

    The attempt to wrest control of the aircraft from the hijackers was perhaps partially successful, while perhaps the aircraft suffered crippling damage in the process. Thus do we have the rebooting of the SDU roughly coinciding with the FMT these (two events again indicating the loss of the hijacking equilibrium), followed by the long fight south into the wilderness to the point of fuel exhaustion.

    Control of the main cabin and by extension the E/E bay was perhaps achieved by our would-be heroes, while control of the flight deck was never attained, with the aircraft either intentionally or inadvertently depressurised in the midst of the mele.

  17. @Rand, This kind of hybrid theory, with a hijacking devolving into a ghost ship, was long one of the more favored possibilities, but has been ruled out by the failure of the seabed search. As Dolan himself has now said, someone was in control until the very end, and we know from the Inmarsat data that the satphone was working throughout. So a conscious person with was at the controls until the end and could have called at any time.

  18. @Jeffwise I would disagree that the conclusion of the seabed search is that it has failed. For starters, it is not yet complete, while there are indications that the search is not being pursued in the correct general location.

    The sat phone system was apparently inoperable for a period and then it was reactivated when the SDU rebooted; am I correct here?

    I would agree that the someone could have made a call up until the very end, only I would disagree with Mr. Dolan that someone was in control of the aircraft up until the every end of the flight. If this is an element of the dominant paradigm, then I would say that it is in error. Indeed, that the aircraft never reached whatever intended destination while there wasn’t any attempt to use the sat phone system to communicate distress is rather indicative of there not being anyone at the controls at the end of the flight.

  19. Following on from my comment above, that article seems to have been edited since I heard it on the earlier edition. There was much more from Martin Dolan, about the end of flight assumptions they have been making, and that they seem to be reconsidering them. I will try to find the full interview and will post a link if I can find it.

  20. @jeffwise

    With merry cheer (and a dollop of confrontation), would you not do well to address the not so insignificant matter that OZ has brought to your attention?

    It seems a we bit misleading to not set the record straight.

  21. @Eoghan
    @jeff Wise

    re cockpit door lock. I thought it was answered in the prior post, but a quick glance didn’t produce the goods I was after. So apologies for not attributing the answer to whomever it was.

    I am of the belief that the cockpit door fails to the lock position. IE, lock is a mechanical mechanism, the unlock is an electrical over ride of that mechanical system. Remove the power and the door fails to the lock position.

    IIRC, I first read of this as data supplied by Gerry Mandala in another forum. Happy to be proven correct or wrong.

  22. @Sharkcaver,

    It’s the other way round; power fail reverts to unlock however there is a manual lock that can be engaged.


  23. Radio-interference from pressing a button on a walkie-talkie could unlock the fortified cockpit door on Airbus and Boeing twin-aisle jetliners.

    In December 2003, a Northwest Airlines maintenance mechanic inside an Airbus A330 jet on the ground in Minneapolis pushed the microphone button to talk into his handheld radio. Though he hadn’t touched the cockpit door, he heard the sound of its lock operating.

    Radio interference from his walkie-talkie had scrambled the electronics inside the door’s locking mechanism.

    The discovery sparked a secretive and expensive engineering effort that started with Airbus and eventually hit Boeing, and is only now nearing completion.

    Boeing: All 747, 767 and 777 wide-bodies that had installed a Boeing-designed fortified door — about 1,700 jets worldwide — had to be fixed. The fixes were completed last month, 16 months after Boeing learned of the problem.

    Read the full article from October 2005 here:

  24. It sounds like Flight 93 all over again , where the hijackers took over the cockpit and the passengers tried to take it back , but in so doing the terrorists crashed the plane into the ground. the only difference is that some passenger or more than one knew about electrical and electronic systems.

  25. Oz,

    I did some follow up research. FCOM states you are correct. Power is required for locking. No power, door is unlocked. And it was Gerry that pointed that out.

    Sorry to the pair of you about my poor memory. There has been a lot of water under the bridge in the last 2+ years.

  26. Hi Jeff:

    Most of your new focus on the 18:25 logon is on target and useful, but the narrative trails off into the weeds again due to a few misguided assumptions and bold statements that do not hold up when examined closely.

    Re: “For one thing, it couldn’t have happened accidentally. Independent researchers have spent months trying to figure out a way that the SDU could have logged off and back on again without human intervention, without success. So it must have been intentional.” This statement is simply not true. It certainly could have happened as the result of an accident. No one knows for sure one way or the other. It is not true that independent investigators have had no success identifying potential alternatives to the Left Main AC Bus explanation. ATSB, the IG and I have each identified and published lists of several alternative explanations, some of which are consistent with an accident. So, the conclusion that “… it must have been intentional…” is simply false. The truth is we still do not know what happened.

    Re: “… it rules out the possibility that MH370 went dark due to fire or electrical malfunction… and it strongly suggests that the plane was not hijacked by one of its own pilots for the purposes of committing suicide (another popular theory). Instead, the SDU re-logon suggests the plane was taken over by a passenger or passengers with a sophisticated knowledge of aircraft electrical systems.” Again, none of this is true. Fire or electrical malfunction is very much on the table. There is no evidence to support the claim that it was “impossible”. There is nothing in the factual evidence to “strongly suggest” that a hijack or suicide did or did not take place. We don’t know. Finally, the conclusion that “…the plane was taken over by a passenger or passengers with a sophisticated knowledge of aircraft electrical systems…” is pure conjecture. There is zero evidence to support that conclusion.

    You do have one thing right. If we could crack the puzzle, and figure out why the AES stopped communicating for a while and then logged on again at 18:25, it could provide very valuable clues pointing to the best place to look for MH370.

  27. @Jeffwise, @Rand, @Eric

    With more debris found my thinking tilts toward uncontrolled descent. As to the failure of the underwater search, the debris drift analysis seems to indicate a more northward location than searched so far.

    I believe to be consistent with what we know this would just require a faster fuel exhaustion and could be due to one of several possibilities:
    1)More maneuvers after IGARI than generally assumed.
    2)Jettison of some fuel (I think there was a report of an oil sleek in SCS).
    3) Relatively minor structural damage (such as blown windows, damage to wings from overspeed, etc) leading to greater air resistance and/or smaller lift and therefore faster fuel burn rate. I believe damage approaching the scale of Aloha flight 243 would cut the range by more than a factor of 2.

  28. ALSM states – “There is nothing in the factual evidence to “strongly suggest” that a hijack or suicide did or did not take place. We don’t know.”

    The “we don’t know” seems to get selectively applied with MH370?

  29. @VivtorI @Gysbreght Regarding the flightpath round below Sumatra.

    A contact from way back who has knowledge of what happened and has accurate ping ring plots has sent me the following which I trust helps fill in the detail.
    Overhead BEDAX at 19:28 turning on to 181
    83nm – Crossing 19:40 – 215nm
    Overhead ISBIX at 20:15 turning on to 166
    157nm – Crossing 20:40 – 370nm – Crossing 21:40 – 246nm
    Overhead YPCC at 22:20 turning on to 079
    126nm – Crossing 22:40 – 406nm
    Overhead YPXM at 23:46 turning on to 047
    155nm – Crossing 00:11 – 55nm
    Overhead IPKON (unlikely)

  30. BTW, I did a cursory search on Google for news on the criminal investigation, presumably under the control of the Royal Malaysian Police and its Chief, Khalid Abu Bakar.

    I wasn’t able to find much of anything on the present status of the criminal investigation, other than a reference to Khalid Abu Bakar commenting on the fanciful finding of aircraft debris on a remote island of the Philippines back in October of last year.

    Does anyone have an update on the criminal side of the investigation?

    @Jeff Besides the tug-of-war between the BEA and the judiciary in France over the flaperon, have you run into any similar manifestations of a conflict re MH 370 between ICAO/air safety prerogatives and the RMP or other investigative/judiciary bodies? Or, any reports of the French judiciary attempting to prise open the RMP on its investigation?

    My general take is that, again, a rigorous criminal investigation does not exist, with the Malaysian authorities conflating it rather conveniently into the search (civil) effort.

  31. Jeff,

    Great article and very informative and clearly outlines the AES/SDU reboot mystery. I believe this is a big clue so we all should keep at it.


    In your #6, if navigational data is restored to the AES, then are we talking about an ADIRU problem prior to that restoration? Your #5 is intriguing, the “software initiated manual reboot” with no power loss, which is what I have been saying that the AES/SDU never was off, but how are they getting into the Classic Aero software system, what holds this non-volatile memory the software or the AES/SDU unit itself?


    I have been posting that for 2 years that Zaharie repaired his bathroom door the afternoon or day of the flight. A bathroom door is hardly a cockpit door though.

    Still perplexing is “load shedding” possibility, why Phil never called Sarah from his seat as he usually did, engine related event at IGARI causing power losses, Left AC bus manually connected for what, fuel pumps, communication that never happened, reverse load shedding or none of them?

  32. Rand – “My general take is that, again, a rigorous criminal investigation does not exist with the Malaysian authorities”

    I think that is a common perception and probably very close to the reality. The French see it differently maybe?

  33. Trond,

    I’d say it was the cell cos. who hold the voice mail or the ringing and decide what a caller hears when attempting to call a number. Ringing doesn’t mean the phone is ringing, it may be the cell co. attempting to contact the number.

  34. Dennis,

    We have bitten this to death. Specifically:

    “1> Pure statistics. Data shows only 20% of hull losses are due to aircraft failures of all kinds.”

    – 20% is significantly high percentage not to be ruled out;
    – I guess technical mulfunctions followed by human error is the major reason.
    – What is percentage of crashes due to mad pilots and what is percentage of crashes due to hijacking?
    – Source of your data?

    “2> Item 1> above is further reduced by the aircraft remaining flying for several hours.”
    Why do you consider only black and white?

    3> No communications of any kind since IGARI. There was ample opportunity to communicate a malfunction event.

    Not really. No power means no SATCOM; 1 of 3 VHFs would be down as well. 1 ELT is portable with the antenna inside – it does not look like it can work from the cabin. The second ’embedded’ ELT can be activated from the cockpit, but its antenna appears to be in the tail section. Other ELTs have no satellite link. Generally I agree that the chance that 4 cables and EE-Bay can be simultaneously damaged is slim; nevertheless it is possible. How probable? I can’t really say.

    Re: “An aircraft failure is so remote given what is known about this flight that it can be safely discarded from consideration.”

    Everything is very remote. Jeff’s summary provides strong arguments against CI or solo-executed suicide. So far technical mulfunction appears to be as plausible as hijacking, so I am wondering how Jeff came to the conclusion that the former can be ruled out. I would not be surprised if FMC is also powered by the left bus, btw.

  35. Jeff,

    Generally you focus on the question why and how SDU became off. But it is equally interesting and important why and how SDU came back.

  36. “Power is required for locking. No power, door is unlocked.”

    Logically, otherwise you would be trapped in the cockpit in case of a power outage.

  37. @Owen Wiseman

    Even when you take into account that it was a redeye flight, the fact (assuming it is a fact) that no cellphone messages got out while the plane was in the air or still on the ground, is extremely unusual. You could be forgiven for saying that such a radio silence would just not happen.

  38. ir1907,

    Re: “Didnt you claim the japanese space rocket part found near thailand was part of MH370 cargo door (with rest of the aircraft flying to the SIO) ?”

    Initially I really thought the fragment was from MH370. Not to say claim. There were suggestions that the fragment is from a boat, but I have never seen the use of such structure in ship-building. I simply missed the possibility that this fragment could be from a space rocket. Anyhow, the photos eventually posted by someone were conviencing that the fragment was from the rocket.

    Re: “Why stick to the ”technical failure” scenario”

    Because each new detail is consistent with it, as opposite to hijacking, mad pilot, etc.

  39. @Sharkcaver

    Re the cockpit door lock: It would be logical for the design to failsafe when the electrical power is removed. Failsafe in this case would be to fail open.

    There is a manual locking provision, should the power fail.

    Understandably, this is a very sensitive subject with airlines, manufacturers and regulating authorities.

  40. @cheryl

    while the cell co tried to connect to the mobile phones they were still online on the chinese social chat apps. Also the cell co must have a logical programming returning a voice saying something like that the mobile phone you are trying to reach has their phones turned off or are not reachable. The system somehow must know that the mobile phones are not connecting. That is how it is in the west. I dont know how it is in asia.

  41. The only mobile phone connecting was from the co-pilot. So how was the chinese still logged in on the social chat app? It doesnt take more than a few minutes top for the connection timeout to kick in, and yet they were still logged in.

  42. @Oleksandr

    Oleksandr: You are wrong when you state that material failure cannot be ruled out.

    It can be categorically ruled out in this case, for several reasons.

    When you look at previous accidents involving mechanical failure you notice two things: In cases of serious failure leading to the loss of the aircraft, the aircraft invariably crashes within an hour of the commencement of the emergency (Air Alaska flight 261 included)

    There is almost always a previous non catastrophic incident of the same type (involving the same failure mechanism) that was not properly followed up. An example is the so called “coffin incident” where a cargo door lock failed on a DC10. the second time it happened, 341 people lost their lives – Turkish Airlines Flight 981.

    With MH370, the emergency began precisely at an FIR boundary, immediately following the sign-off. The plane then flew carefully along another FIR boundary, while attempting to evade radar (transponder off) and in radio silence, and then turned south at a 3rd FIR boundary. These facts are unavoidable and can lead to one conclusion only: deliberate, premeditated action by the crew.

    Any other conclusion can only mean one thing, delusional denial.

  43. ROB,

    You are absolutely wrong. You named a few things, which support hijacking/mad pilot scenario. How do they rule out technical failure? Could you elaborate?

    Flying along FIRs coincides with the route in case of an emergency. Chances are 50/50. This was discussed many times.

  44. If all electrical power from the left engine (IDG and BU generator) is disabled during the turn at Igari, due to damage to the Left Aims Cabinet/P100 Left Power Panel, the Left Main AC Bus will be momentarily de-powered.

    When the AC power source changes in flight, a break power transfer will occur, such that the Right IDG will repower both the Right and Left Main AC busses. Load shedding would occur. On the ground a No-break power transfer would occur.

    The Left Transponder would also lose mode S capability because the Left Aims Cabinet feeds air data to it, then fault monitoring would disable the transponder completely.

    The Aims Cabinet interacts with around 130 LRUs. Damage to the Left Aims Cabinet would be a major electrical problem, such that any “left” system has the potential to be disabled or corrupted in some way.
    The crew would be overwhelmed with failures.

    All radio calls depend on the Audio Management Unit which itself depends on the Left System ARINC 629 Bus.

    If the Left HGA is also disabled, satellite communications would only be possible when the Right HGA is exposed to the satellite, eg start of turn at Nilam to Sanob.

    If the aircraft was allowed to continue on in this configuration (ie disabled left engine electrical power) until fuel exhaustion, when the right engine fails, the Left and Right Main AC busses and the Left and Right Transfer Busses would all be depowered.
    The autopilot would disengage and the RAT would be deployed.
    The aircraft would start to descend. The APU would auto start and restore power to the Left and Right Main AC busses.
    The Satcom would be rebooted.
    The aircraft is now flying single engine with flight envelope protections enabled such as over bank, overspeed, stall, TAC.
    The aircraft would continue on until the left engine failed.

    This would mean that the seventh arc is after the first engine failure and not the second.

    And the aircraft could be up to 100 nautical miles from the seventh arc hotspot!

  45. @rob

    Firs, avoiding radars, acting non agressive, all points to getting away, far far away.

    Not for suicide not to land somewhere, but to neutralize the cargo. Clues were left deliberately behind to tell us what did not happen. Someone part of this disappearence that was not on the plane.

  46. @Oleksandr

    Sorry, my dear fellow but flying carefully along an FIR boundary after a material emergency, flying up the centre of the Malacca Strait and avoiding Indonesian territory while at the same time maintaining cruising altitude, above normal cruising speed and also maintaining radio, ACARS silence and with radar transponder switched off, but with navigation systems functioning normally – chances of anything other than premeditated action by the crew has to be several million to one against!

    Sorry, but you’re definitely backing a looser there.

  47. @Rand

    You can modify that scenario a bit (speculation only):

    – hijackers (passengers and/or crew member) take over the plane, shut down coms, demand it to be diverted to Learmonth, Australia via NW Sumatra to avoid radar coverage for most of the flight

    – after it leaves radar coverage, a fight on board occurs (e.g. shooting/explosion) and concomitant pressure loss. Pilots react and descend to 10.000 ft, slow down. Alternatively: the plan was supposed to arrive at daytime to attract more media attention.

    – Hijackers are made aware that fuel is insufficient now, but nevertheless insist on the route (as in Ethiopian Air 961).

    – the route taken could be consistent with the one suggested in the preliminary report and most drift models

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