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Expert Was Needed to Disable Malaysia Airlines Jet Systems

136 points by pzaich 13y ago

deleted 13y ago
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waterlesscloud 13y ago
I was reading up on the Primary Flight Computer (PFC) of the 777, just out of curiosity. It's a triple redundant system, that is there's 3 separate PFC systems. That's not too surprising. What did surprise me was that each of the 3 PFCs has 3 channels, and each channel is a CPU from a different manufacturer (AMD, Motorola, Intel). The reasoning is that any flaw in any particular cpu design would be outvoted by the other two. They appear to use 3 different compilers for this reason (Ada), one for each processor. Seems like the I/O and endianness of the various chips would add complexity too. I wonder if the added complexity makes it a net win or loss for safety? I guess a win, since that's what they do.
- aaron695 13y ago
  Sounds interesting. Link?
  - GigabyteCoin 13y ago
    http://www.scribd.com/doc/212547313/Primary-Flight-Computer-PFC-of-the-777 http://www.scribd.com/doc/212547313/Primary-Flight-Computer-...
- wyager 13y ago
  >They appear to use 3 different compilers for this reason (Ada) I understand why Ada is used for safety-critical applications, but I have to wonder: Does the fact that Ada is a relatively old and unfriendly language lead to more bugs than it prevents? My mind would probably go blank if I had to stare at Ada code for 8 hours a day. What if we used Haskell for all non-realtime safety-critical functionality in aircraft? With a few extra rules to prevent stack overflows, I think I'd trust a million-line Haskell program over a million-line Ada program (although it would probably be more like ten-thousand-line Haskell program vs million-line Ada program).
  - protomyth 13y ago
    Ada is proven in this area and generates fast, efficient code that is suitable for embedded systems. Ada's last revision is 2012. What do you find unfriendly? I would most certainly not trust Haskell over Ada in embedded system work.
    - wyager 13y ago
      >Ada is proven in this area and generates fast, efficient code that is suitable for embedded systems. So does coding in assembly. The idea is to create fast, efficient code that is also simple and easy to understand. >I would most certainly not trust Haskell over Ada in embedded system work. If the system does not have hard realtime requirements and has a decent resources, why wouldn't you trust Haskell?
      - akiselev 13y ago
        >> If the system does not have hard realtime requirements and has a decent resources, why wouldn't you trust Haskell? Because that doesn't describe cars, a jet, space shuttles, or ... well anything I'd trust my life to. Hell, Haas CNCs still run DOS 8.0
        comex 13y ago
        Yeah, I would avoid trusting something hard-realtime to a language with lazy evaluation and garbage collection, even if it's quite trustworthy for other purposes. (IIRC, these programs don't even use malloc, let alone garbage collection :)
        akiselev 13y ago
        MISRA discourages use of malloc (because you can deviate with clear documentation as to why) but it's not at all unheard of. That said, many embedded systems don't come with a usable implementation of malloc so the safe default is to write your own memory manager (safer but not always possible: use a well tested one) that uses static memory pools to allocate dynamic memory.
- TheLoneWolfling 13y ago
  Hard to say. It means that there's an increased chance of bugs overall, yes, but a decreased chance of bugs that affect the overall flight, as it means that many more bugs will be caught and dealt with before they start affecting things majorly. It doesn't save you from flaws in the design specs, though, or if everyone made the same faulty assumption. As I've found myself: the best way to test an implementation of a data structure is to compare it against another implementation (preferably the simplest implementation possible - singly linked list, anyone?) and assert that they exhibit identical behavior.
- chaz 13y ago
  This reminds me of an article I read about the Space Shuttle's flight control system. Five computers on board, with 4 running redundantly and the fifth on backup. > Q. How are actuators controlled? > A. For the aerosurface actuators, each of the four computers sends out an independent command on an independent bus. With no failures, the commands should be identical. The voting is done at the actuator using a hydraulic voting mechanism, called a force-fight voter. In it, there are four hydraulic ports called secondary ports, each commanded by one of the four GPCs. The secondary ports go into the primary ports, which are heavy-duty actuators that connect to what's called a "summing bar," which is no more than a massive steel rod. If there are three good computers and one bad one, the three good commands physically out-muscle the fourth. This limits the control authority a little bit--we don't get the total force we'd like to get, but there's still enough power to control the vehicle. If you have a large enough pressure differential for a large enough time, the port is hydraulically bypassed, which relieves the pressure in that one port. The remaining three ports then regain their full authority. The whole article is worth a read: http://klabs.org/DEI/Processor/shuttle/shuttle_primary_computer_system.pdf http://klabs.org/DEI/Processor/shuttle/shuttle_primary_compu...
  - qwerty_asdf 13y ago
    Homer: Well, today's the day for Homer J. I know I'm gonna win this time. Lenny: Yeah? How come? Homer: Union Rule 26: "Every employee must win Worker of the Week at least once regardless of gross incompetence, obesity or rank odor." Mr. Burns: Compadres, it is imperative that we crush the freedom fighters before the start of the rainy season. And remember, a shiny new donkey for whoever brings me the head of Colonel Montoya... Hmm? What? Oh! ...and by that I mean, of course, it's time for the Worker of the Week Award. I can't believe we've overlooked this week's winner for so very, very long. We simply could not function without his tireless efforts. So, a round of applause for this inanimate [steel] rod.
    - qbrass 13y ago
      It was a carbon rod. That was the episode where Homer went into space, where another carbon rod became a hero. http://simpsons.wikia.com/wiki/Inanimate_carbon_rod http://simpsons.wikia.com/wiki/Inanimate_carbon_rod
- WalterBright 13y ago
  This has been normal practice on airline computers for decades. The 757 used dual systems (the third being the pilot). Each channel: 1. used a different CPU architecture and brand 2. used different circuits 3. used different algorithms 4. used different languages 5. were developed by independent teams 6. with a third independent team to verify there were no inadvertent similarities If the two channels disagreed, they were automatically electrically isolated, and the pilot was notified and was expected to take over.
  - doxydexydroxide 13y ago
    And this is why the 757 systems failed far too often, because taking N-Modular Redundancy to this level causes a great deal of false positives. For this reason it was rejected for use on the 777 by the FAA Chief Scientific and Technical Advisor for Flight Controls. With regard to the 777 Flight Control System Design, "Bob Yeh" released a number of documents on the system. http://www.citemaster.net/get/1472830e-8785-11e3-9b63-00163e009cc7/yeh98_777-fbw.pdf http://www.citemaster.net/get/1472830e-8785-11e3-9b63-00163e...
    - WalterBright 13y ago
      I didn't know this. It makes sense, and the reference indicates they did some solid statistical work on the experiences with those methods.
- csel 13y ago
  Interesting bit here: There were 20 Freescale Semiconductor engineers on that MH 370 plane. Story is getting interesting by the day. http://www.reuters.com/article/2014/03/09/us-malaysia-airlines-freescale-idUSBREA280T020140309 http://www.reuters.com/article/2014/03/09/us-malaysia-airlin...
- userbinator 13y ago
  > I wonder if the added complexity makes it a net win or loss for safety? I guess a win, since that's what they do. The chance of one or more of the systems failing actually triples (OR), but the chance of all three failing (AND) decreases, which is what redundancy provides. Basic probability.
- jballanc 13y ago
  Probably an overall win for safety, redundancy, and (maybe more importantly) security. That said, considering the number of different exploits that have been assembled for large attacks in the past (how many zero-days were in Stuxtnet?), I wouldn't completely rule out the possibility that the flight systems were hacked. This flight may not even have been the primary target, but rather a test of the attack vector, with the attacker finally directing the aircraft out over a big, deep body of water where it would eventually run out of fuel and eliminate most of the evidence.
- noir_lord 13y ago
  Where was you reading this?, I love that type of stuff.
- RA_Fisher 13y ago
  More components obviously reduce the reliability, but if the likelihood of failure of each of those redundant systems are independent (and to some degree even if they are dependent), at a high-level I believe it's just P(failure of system 1)P(2)P(3), so the likelihood of failure could pretty easily be made infinitesimal. On the other hand, there are lots of plane flights. :-)
bhouston 13y ago
Some people say that the parallels to this ghost plane incident a decade ago are increasing: http://en.wikipedia.org/wiki/Helios_Airways_Flight_522 http://en.wikipedia.org/wiki/Helios_Airways_Flight_522
- fourstar 13y ago
  Pretty sure that was posted by a single redditor (for 3 hours) http://www.reddit.com/r/AskReddit/comments/20fmd0/serious_malaysia_airlines_flight_370_megathread/cg2uo2v http://www.reddit.com/r/AskReddit/comments/20fmd0/serious_ma.... Who else is saying this and where?
  - Sniffnoy 13y ago
    Charlie Stross wrote a blog post mentioning it a few days ago: http://www.antipope.org/charlie/blog-static/2014/03/a-hypothesis.html http://www.antipope.org/charlie/blog-static/2014/03/a-hypoth...
  - deleted 13y ago
    [deleted]
uptown 13y ago
This article alludes to one circuit killing both transponders, but I'd seen reported elsewhere that there was a 14 minute gap between when the transponders became innactive. Wouldn't that gap lend credibility to them not being disabled by a single circuit?
- joering2 13y ago
  jamed by AWACS? Owners of this patent [1] were all aboard the plane. The only remaining owner is Freescale Semiconductor, owned by Rothschild family. [1] http://truthnewsinternational.files.wordpress.com/2014/03/us008671381.pdf http://truthnewsinternational.files.wordpress.com/2014/03/us...
  - _delirium 13y ago
    That patent seems like a thin hook to hang a conspiracy theory off of. It looks like a run-of-the-mill "optimize placement of stuff in a slightly different way than other people have done" patent, of which there are at least hundreds yearly.
    - joering2 13y ago
      um, "optimize placement of stuff in a slightly different way than other people have done" and save billions of dollars over the span of time, due to very high price of silicon wafers? ok.
      - _delirium 13y ago
        Most likely not; it's just another minor process variation, like the thousands of such patents that exist. Is there evidence that this patent is a particularly novel or important one? And furthermore, what motive would someone have to knock off the inventors when they no longer even own the patent? If you look in the document, you can see that it has an single Assignee, Freescale Semiconductor. When a patent has been "assigned", the original inventors give up any proprietary rights in the invention to the Assignee, which is the normal process with corporate patents.
threeseed 13y ago
Makes you wonder about the logistics of this all. Moving around the plane opening hatches and tinkering with equipment requires there to be at least a few people. One to do the work, one inside the cockpit managing the flight and one looking after the passengers. All of them you would assume would have guns to keep the passengers from simply rushing them. Getting multiple weapons past security surely means an inside job. And then what is the motivation for multiple people wanting to hijack this particular plane ?
- Qworg 13y ago
  The best I can offer for that is the 20 Freescale employees on board.
- will_asouka 13y ago
  Flight deck doors are secure also, and the first action on attempted hijack is divert to the nearest suitable. It looks increasingly likely that one or both pilots remained in control.
- baq 13y ago
  150 Chinese on board. Maybe a kid of some high Chinese party official was on board?
- shimon_e 13y ago
  Cargo. The cargo list has still not been released. It is speculated that the cargo was heavy as the max amount of passengers was 50 less than the number of seats.
jevinskie 13y ago
Does anyone know of a plot of the hourly satellite ping locations? The article made it sound like they contained GPS coordinates.
- analog31 13y ago
  From what I've read, there's no GPS in the satellite ping data, but apparently some rough estimate can be made from signal strengths.
  - dylz 13y ago
    The article also says >Until just a few years ago, the satellite communication system used by jetliners didn't include data on an aircraft's location in the pings, the electronic equivalent of handshakes used to establish initial contact.
    - analog31 13y ago
      I have a personal rule to date-time stamp all data collected from experiments. I'd add GPS if my experiments weren't all stationary. The extra bit of meta-data is a lifesaver if I do something dumb and have to reconstruct what I was doing when I collected the data, for instance correlating the data with my notes or other information that I gather.
- ams6110 13y ago
  One is posted here. http://www.pprune.org/rumours-news/535538-malaysian-airlines-mh370-contact-lost-175.html#post8376066 http://www.pprune.org/rumours-news/535538-malaysian-airlines...
  - deleted 13y ago
    [deleted]
gkoberger 13y ago
EDIT: Currently it looks like I'm completely wrong: http://hosted.ap.org/dynamic/stories/A/AS_MALAYSIA_PLANE?SITE=AP&SECTION=HOME&TEMPLATE=DEFAULT&CTIME=2014-03-15-00-22-45 http://hosted.ap.org/dynamic/stories/A/AS_MALAYSIA_PLANE?SIT... ------------------------ Disclaimer: I know nothing about planes. That being said, this seems like fodder for conspiracy theories and click throughs. Under normal circumstances, yeah, I bet it's hard to disable. However, if we assume the plane crashed, we know there was a massive malfunction -- seems more likely to me that it was a part of that.
- yukichan 13y ago
  I am not sure the WSJ cares much about click throughs. They are a subscription based-service. There are no ads on that page, at least not when I open up a browser with no adblocker.
- jeswin 13y ago
  I reach for occam's razor almost reflexively; I am inclined to think that the plane will be found around the area we lost contact. However, the fact that India and the US is deploying so many assets on the other side makes me suspect they might have some credible leads. I am guessing India is possibly working more with the US than anyone else; given that India wouldn't want China to know what capabilities they have there.
  - InclinedPlane 13y ago
    Occam's razor only applies to theories that actually explain all the available evidence. That theory does not.
    - tomelders 13y ago
      It's getting to the point where whenever I see someone invoke Occam's Razor, I stop reading. People seem to think it means "The explanation is always simple", but what it actually means is "the hypothesis with the fewest assumptions should be selected." On the disappearance of MH730 it seems a lot of people are happy to make the unfathomably large assumption that this was "probably" a catastrophic mechanical failure and that the plane has crashed into the sea, despite the conspicuous absence of any evidence for this scenario such as mayday calls, or a wreckage and now, in the face of overwhelming evidence that directly contradicts the theory that the plane has crashed (because it appears to have been under the control of a skilled pilot for five hours after it went missing, and skilled pilots are usually pretty good at landing planes) people are still positing the notion that the plane has crashed and that Occam's Razor somehow supports this point of view. In short, "the most likely explanation" in this case, is the one that makes a boat load of wild assumptions.
Thiz 13y ago
Occam's razor, the plane exploded in mid air. Not even time to mayday.
- cavejohnson 13y ago
  How does that explain the four hours of satellite pings after the transponders cut out?
  - sorahn 13y ago
    Yeah, and where is the plane? Even in a million pieces, some of them should be somewhere.
    - rosser 13y ago
      All of them are somewhere. They're just somewhere in a really big ocean.
- LoganCale 13y ago
  No. The latest evidence shows that it flew on for hours afterwards and continued responding to satellite pings. If it exploded at the point where the transponder went offline, debris would have been found in that area by now.
- logicallee 13y ago
  Occam's razor is that nuclear power plants don't exist, they're just coal power plants (which already existed) with a story about nuclear power being possible. After all, do you have any idea how complicated controlled fission would have to be? It's easier if it doesn't exist. The problem with this "theory" is that it doesn't explain all the evidence. Sure, a hijack would have to be way more complicated than a mid-air explosion, just like a nuclear power plant would have to be way more complicated. But a complicated set of transponders turning off with sudden radio silence is exactly what happened. Plus, if it was a mid-air explosion - where are the pieces?
  - 13y ago
mutagen 13y ago
Anyone interested in this event or feeling inclined to speculate on the cause, mechanisms, and outcomes of the disappearance of Flight 370 should read a couple of the most recent threads on the topic over at airliners.net[1]. Their forums are the equivalent of HN for pilots and other aircraft professionals and are a fascinating read anytime an aircraft event is worth discussing. [1] http://www.airliners.net/aviation-forums/general_aviation/read.main/6024376/ http://www.airliners.net/aviation-forums/general_aviation/re... - Currently the most recent thread.
- ams6110 13y ago
  pprune.org is another one
hindsightbias 13y ago
You don't need an expert if there's a fire in the cockpit: http://www.avherald.com/h?article=44078aa7&opt=0 http://www.avherald.com/h?article=44078aa7&opt=0 Answers are in the past.
kayoone 13y ago
Or it might have just malfunctioned because of other fatal malfunctions leading up to the Crash.
ronnier 13y ago
Malaysian investigators conclude flight hijacked. http://www.cbsnews.com/news/malaysia-airlines-flight-370-more-sinister-theories-still-no-answers-in-search-for-missing-plane/ http://www.cbsnews.com/news/malaysia-airlines-flight-370-mor...
romanrage 13y ago
Well, the question is still is Missing Malaysia Airline Plane MH370, Where It Disapear ? http://feedingnew.wordpress.com/2014/03/13/mystery-of-missing-malaysia-airline-plane-mh370-where-it-disapear/ http://feedingnew.wordpress.com/2014/03/13/mystery-of-missin...
bdonlan 13y ago
The article talks about needing to pull a circuit breaker to kill the transponder - I thought the transponder had a mode selection switch on the pedestal that could be set to standby; is there something else to it that I'm missing?
- choult 13y ago
  Presumably it needed total disabling, not just switching off...
lazyjones 13y ago
The 777 is fully FBW apparently and many (all?) sensors communicate wirelessly. What are the chances that it was hacked by a passenger or remotely and taken over this way?
- noir_lord 13y ago
  None-zero but then most events are.
- gvb 13y ago
  Wireless sensors? [Citation needed] I don't have direct experience with the 777, but do with the 787 and other aircraft systems. I am not aware of any wireless sensors. There are a lot of sensors which communicate with the various computers over multiplexed wired data buses. ARINC 429 is a legacy, but still heavily used, digital data bus. ARINC 629 is used on the 777. ARINC 664 is used on the 787 (and Airbus A380). The military systems and some commercial systems also use MIL-STD-1553 and other digital busses. All wired. Ref: http://en.wikipedia.org/wiki/ARINC http://en.wikipedia.org/wiki/ARINC
- snom380 13y ago
  It's fly-by-wire not fly-by-wireless.
joyofdata 13y ago
If this was a movie plot it would be bashed for being unrealistic ... "It doesn't make any sense somebody could hijack a plane that easily - you know, just deactivate the transponder and be gone - it's not that simple, of course - that would be ridiculous - and there is radar everywhere. Also the earth is covered with photo satellites - they would find the plane in no time - you know, a plane is a pretty big thing - haha - so anyway, bit naive, but the acting was alright - so if it wasn't about the transponder plot hole I'd give it a solid 8 ..."
- heartbreak 13y ago
  If? You mean when this story becomes a movie plot. I give it one year after they find it.
  - tomelders 13y ago
    This seems like a great place for me to add my wild and crazy crack pot 99.99% likely to be total nonsense theory to the cacophony of other similar theories... which would make a great plot device for a movie none the less. I'll give you the cliff notes version When handing over from one ATC to another, MH370 adopted the identity of another plane in the area, and the other plane switched off it's transponders (let's call this other plane AB123). Leading to a scenario where the whole world is looking for a plane in the sea when it's actually airborne, but just happens to look like another plane on radar, and they landed it at some backwater airport (AB123's destination) that's under terrorist control (for example, how big a team would you need to take over Port Blair Airport on the Andaman islands? I'm guessing not very many, and no would be any wiser if you ran it as normal) But why do this? Because whoever stole this plane needs to be able to fly MH370 into someones airspace unnoticed to do something bad, and flight AB123 is scheduled to fly into that airspace sometime soon, but if flight AB123 had been hijacked, or had gone missing, it would raise alarms. But to the outside world, flight ABC123 is fine, it's MH370 that everyone is worried about... but flight AB123 is MH370. So where is AB123? I don't know. Maybe thats the plane the oil rig worker saw crash, or maybe they figured out some other way to hide it. Perhaps both planes flew to AB123's destination, but with one flying directly above the other so that it looks like one plane on radar (I don't know how Radar works but this would work for a movie) Also, AB123 might not be a passenger jet, it could be a cargo plane, or some other kind of plane that doesn't come with a bunch of passengers that people would miss. Anyhoot, that's my crazy theory and even I don't believe it, but a small part of me hope's it's right because the people on Flight MH370 could still be alive. At the very least, I think this is a good plot for a movie.
mstrem 13y ago
I get the feeling no one has a clue yet. It is easy to come up with theories... e.g. Malfunction in plane - transponder turns off - cabin loses pressure (and everyone on plane goes unconscious or similar) - because cockpit is locked crew does not manage to do anything in time - plane keeps on going - fuel runs out. of course that is probably totally wrong. One thing though - if it did fly low over land - I would expect at least someone would have used their cell phone - so I would rule out that option.
vannevar 13y ago
Everyone seems to be jumping on the hijacker theory, but I have yet to see any evidence to contradict the theory of a fire aboard the plane. It explains the sudden course change, the failure (or deliberate shutdown) of some electrical circuits, and the altitude change (an effort to starve the fire of oxygen in the unpressurized regions of the aircraft). It seems like aircraft fires occur more often than hijackings. Is there any reason at this point to prefer the hijacking theory, other than that it's a bit more sensational?
- TrevorJ 13y ago
  The engines 'phoned home' long after the plane went off the radar so to speak. The altitude data has also been said to be unreliable.
  - vannevar 13y ago
    That doesn't contradict the fire theory, though. It simply means that the fire didn't directly bring the plane down, but it could still have incapacitated some of the systems and possibly the crew.
- mpyne 13y ago
  But it doesn't explain why none of the flight crews bothered to let any of the ATCs know that they had a fire on the plane...
- hga 13y ago
  Responding to mpyne: you can envision scenarios where the fire took out their radios. TrevorJ is a lot closer to the mark, although it wasn't the engine system phoning home, it was some sort of generic hourly "ping" with no other content (since the airline didn't sign up for the service that would have done more). Since these were pings from or to IMARSAT geosync satellites, very rough estimates of where the plane could be have been were made from them. I assume based on which satellites heard them (vs. ones over the horizon), perhaps comparing time-stamps and transit times to 22,000 miles in orbit, etc. But of course the bottom line is that these pings went on for hours, which evidently would only stop when the engines stopped for whatever reason. That makes a plausible fire scenario more complicated.
georgeecollins 13y ago
Here is my conspiracy theory: If you were the FSB, you would want to distract popular attention from events in the Ukraine. A lack of news coverage of the events in Crimea takes the heat off Western leaders to look tough.
Myrmornis 13y ago
I haven't seen any explanation of the statement that the plane's location was thought to be within one of two "corridors" in completely different places -- a northern one extending to Kazakhstan and a southern one extending into the southern Indian Ocean. Is this indeterminacy expected? Is it the result of some sort of geometrical symmetry? I imagine someone here knows?
- hga 13y ago
  It's based on the reception of the pings at the IMMARSAT geosync satellite. Look at a picture, e.g., here: http://en.wikipedia.org/wiki/File:MH370_last_ping_corridors.jpg http://en.wikipedia.org/wiki/File:MH370_last_ping_corridors.... The "corridors" are actually geometrically symmetrical arcs as you suspect, somewhere around which it's believed the plane traveled until the pings stopped, presumably because the engines stopped running.
  - hga 13y ago
    The map I directed to you was apparantly an enhanced one from the NYT; here's one with many more details figured in: http://www.nytimes.com/2014/03/17/world/asia/malaysia-airlines-flight.html?hp http://www.nytimes.com/2014/03/17/world/asia/malaysia-airlin... although I wouldn't treat those boundaries as gospel, there's likely more slop in the real estimates derived from the satellite.
  - Myrmornis 13y ago
    Thanks! According to sources [1, 2] there was a period of time during which it was pinging multiple satellites. Surely this symmetry doesn't persist in a dataset comprising pings at different times to different satellites (which themselves are moving)? [1] https://en.wikipedia.org/wiki/Malaysia_Airlines_Flight_370 https://en.wikipedia.org/wiki/Malaysia_Airlines_Flight_370 [2] http://edition.cnn.com/2014/03/14/world/asia/malaysia-airlines-plane/index.html?hpt=ias_c1 http://edition.cnn.com/2014/03/14/world/asia/malaysia-airlin...
    - hga 13y ago
      They're in geosynchronous orbit, so they rotate with the earth, are always over the same spot on earth at the equator. Don't know which satellite series is used for this service, but the Inmarsat constellations aren't particularly large: http://en.wikipedia.org/wiki/Inmarsat#Satellites http://en.wikipedia.org/wiki/Inmarsat#Satellites, so it could be they only got solid data---and it's not very specific---from one satellite. I also wouldn't put much confidence in mass media reports saying "satellites", and the Wikipedia plural use is probably based on them.
cfreeman 13y ago
Is there any legitimate reason for the pilot to disable the transponder? It seems like they should make it more difficult than just throwing a breaker in the cockpit.
- lutusp 13y ago
  > Is there any legitimate reason for the pilot to disable the transponder? Yes, of course -- any piece of electronic equipment might (a) begin to misbehave and interfere with other equipment or produce misleading results, or (b) catch fire and emit smoke into the flight deck, or (c) both. It's common sense to have a way to disable any piece of equipment on short notice. I played a small part in the design of NASA's Space Shuttle many years ago, and we definitely kept the possibility of equipment failure in mind at all times. > It seems like they should make it more difficult than just throwing a breaker in the cockpit. On board an aircraft, the pilot has the highest authority. You don't expect to have to protect the aircraft from him -- more the reverse. That is why, when a pilot goes crazy, the results are usually catastrophic.

136 points by pzaich 13y ago

deleted 13y ago

[deleted]

I was reading up on the Primary Flight Computer (PFC) of the 777, just out of curiosity. It's a triple redundant system, that is there's 3 separate PFC systems. That's not too surprising. What did surprise me was that each of the 3 PFCs has 3 channels, and each channel is a CPU from a different manufacturer (AMD, Motorola, Intel). The reasoning is that any flaw in any particular cpu design would be outvoted by the other two. They appear to use 3 different compilers for this reason (Ada), one for each processor. Seems like the I/O and endianness of the various chips would add complexity too. I wonder if the added complexity makes it a net win or loss for safety? I guess a win, since that's what they do.

aaron695 13y ago
Sounds interesting. Link?
- GigabyteCoin 13y ago
  http://www.scribd.com/doc/212547313/Primary-Flight-Computer-PFC-of-the-777 http://www.scribd.com/doc/212547313/Primary-Flight-Computer-...
wyager 13y ago
>They appear to use 3 different compilers for this reason (Ada) I understand why Ada is used for safety-critical applications, but I have to wonder: Does the fact that Ada is a relatively old and unfriendly language lead to more bugs than it prevents? My mind would probably go blank if I had to stare at Ada code for 8 hours a day. What if we used Haskell for all non-realtime safety-critical functionality in aircraft? With a few extra rules to prevent stack overflows, I think I'd trust a million-line Haskell program over a million-line Ada program (although it would probably be more like ten-thousand-line Haskell program vs million-line Ada program).
- protomyth 13y ago
  Ada is proven in this area and generates fast, efficient code that is suitable for embedded systems. Ada's last revision is 2012. What do you find unfriendly? I would most certainly not trust Haskell over Ada in embedded system work.
  - wyager 13y ago
    >Ada is proven in this area and generates fast, efficient code that is suitable for embedded systems. So does coding in assembly. The idea is to create fast, efficient code that is also simple and easy to understand. >I would most certainly not trust Haskell over Ada in embedded system work. If the system does not have hard realtime requirements and has a decent resources, why wouldn't you trust Haskell?
    - akiselev 13y ago
      >> If the system does not have hard realtime requirements and has a decent resources, why wouldn't you trust Haskell? Because that doesn't describe cars, a jet, space shuttles, or ... well anything I'd trust my life to. Hell, Haas CNCs still run DOS 8.0
      - comex 13y ago
        Yeah, I would avoid trusting something hard-realtime to a language with lazy evaluation and garbage collection, even if it's quite trustworthy for other purposes. (IIRC, these programs don't even use malloc, let alone garbage collection :)
        akiselev 13y ago
        MISRA discourages use of malloc (because you can deviate with clear documentation as to why) but it's not at all unheard of. That said, many embedded systems don't come with a usable implementation of malloc so the safe default is to write your own memory manager (safer but not always possible: use a well tested one) that uses static memory pools to allocate dynamic memory.
TheLoneWolfling 13y ago
Hard to say. It means that there's an increased chance of bugs overall, yes, but a decreased chance of bugs that affect the overall flight, as it means that many more bugs will be caught and dealt with before they start affecting things majorly. It doesn't save you from flaws in the design specs, though, or if everyone made the same faulty assumption. As I've found myself: the best way to test an implementation of a data structure is to compare it against another implementation (preferably the simplest implementation possible - singly linked list, anyone?) and assert that they exhibit identical behavior.
chaz 13y ago
This reminds me of an article I read about the Space Shuttle's flight control system. Five computers on board, with 4 running redundantly and the fifth on backup. > Q. How are actuators controlled? > A. For the aerosurface actuators, each of the four computers sends out an independent command on an independent bus. With no failures, the commands should be identical. The voting is done at the actuator using a hydraulic voting mechanism, called a force-fight voter. In it, there are four hydraulic ports called secondary ports, each commanded by one of the four GPCs. The secondary ports go into the primary ports, which are heavy-duty actuators that connect to what's called a "summing bar," which is no more than a massive steel rod. If there are three good computers and one bad one, the three good commands physically out-muscle the fourth. This limits the control authority a little bit--we don't get the total force we'd like to get, but there's still enough power to control the vehicle. If you have a large enough pressure differential for a large enough time, the port is hydraulically bypassed, which relieves the pressure in that one port. The remaining three ports then regain their full authority. The whole article is worth a read: http://klabs.org/DEI/Processor/shuttle/shuttle_primary_computer_system.pdf http://klabs.org/DEI/Processor/shuttle/shuttle_primary_compu...
- qwerty_asdf 13y ago
  Homer: Well, today's the day for Homer J. I know I'm gonna win this time. Lenny: Yeah? How come? Homer: Union Rule 26: "Every employee must win Worker of the Week at least once regardless of gross incompetence, obesity or rank odor." Mr. Burns: Compadres, it is imperative that we crush the freedom fighters before the start of the rainy season. And remember, a shiny new donkey for whoever brings me the head of Colonel Montoya... Hmm? What? Oh! ...and by that I mean, of course, it's time for the Worker of the Week Award. I can't believe we've overlooked this week's winner for so very, very long. We simply could not function without his tireless efforts. So, a round of applause for this inanimate [steel] rod.
  - qbrass 13y ago
    It was a carbon rod. That was the episode where Homer went into space, where another carbon rod became a hero. http://simpsons.wikia.com/wiki/Inanimate_carbon_rod http://simpsons.wikia.com/wiki/Inanimate_carbon_rod
WalterBright 13y ago
This has been normal practice on airline computers for decades. The 757 used dual systems (the third being the pilot). Each channel: 1. used a different CPU architecture and brand 2. used different circuits 3. used different algorithms 4. used different languages 5. were developed by independent teams 6. with a third independent team to verify there were no inadvertent similarities If the two channels disagreed, they were automatically electrically isolated, and the pilot was notified and was expected to take over.
- doxydexydroxide 13y ago
  And this is why the 757 systems failed far too often, because taking N-Modular Redundancy to this level causes a great deal of false positives. For this reason it was rejected for use on the 777 by the FAA Chief Scientific and Technical Advisor for Flight Controls. With regard to the 777 Flight Control System Design, "Bob Yeh" released a number of documents on the system. http://www.citemaster.net/get/1472830e-8785-11e3-9b63-00163e009cc7/yeh98_777-fbw.pdf http://www.citemaster.net/get/1472830e-8785-11e3-9b63-00163e...
  - WalterBright 13y ago
    I didn't know this. It makes sense, and the reference indicates they did some solid statistical work on the experiences with those methods.
csel 13y ago
Interesting bit here: There were 20 Freescale Semiconductor engineers on that MH 370 plane. Story is getting interesting by the day. http://www.reuters.com/article/2014/03/09/us-malaysia-airlines-freescale-idUSBREA280T020140309 http://www.reuters.com/article/2014/03/09/us-malaysia-airlin...
userbinator 13y ago
> I wonder if the added complexity makes it a net win or loss for safety? I guess a win, since that's what they do. The chance of one or more of the systems failing actually triples (OR), but the chance of all three failing (AND) decreases, which is what redundancy provides. Basic probability.
jballanc 13y ago
Probably an overall win for safety, redundancy, and (maybe more importantly) security. That said, considering the number of different exploits that have been assembled for large attacks in the past (how many zero-days were in Stuxtnet?), I wouldn't completely rule out the possibility that the flight systems were hacked. This flight may not even have been the primary target, but rather a test of the attack vector, with the attacker finally directing the aircraft out over a big, deep body of water where it would eventually run out of fuel and eliminate most of the evidence.
noir_lord 13y ago
Where was you reading this?, I love that type of stuff.
RA_Fisher 13y ago
More components obviously reduce the reliability, but if the likelihood of failure of each of those redundant systems are independent (and to some degree even if they are dependent), at a high-level I believe it's just P(failure of system 1)P(2)P(3), so the likelihood of failure could pretty easily be made infinitesimal. On the other hand, there are lots of plane flights. :-)

bhouston 13y ago

Some people say that the parallels to this ghost plane incident a decade ago are increasing: http://en.wikipedia.org/wiki/Helios_Airways_Flight_522 http://en.wikipedia.org/wiki/Helios_Airways_Flight_522

fourstar 13y ago
Pretty sure that was posted by a single redditor (for 3 hours) http://www.reddit.com/r/AskReddit/comments/20fmd0/serious_malaysia_airlines_flight_370_megathread/cg2uo2v http://www.reddit.com/r/AskReddit/comments/20fmd0/serious_ma.... Who else is saying this and where?
- Sniffnoy 13y ago
  Charlie Stross wrote a blog post mentioning it a few days ago: http://www.antipope.org/charlie/blog-static/2014/03/a-hypothesis.html http://www.antipope.org/charlie/blog-static/2014/03/a-hypoth...
- deleted 13y ago
  [deleted]

uptown 13y ago

This article alludes to one circuit killing both transponders, but I'd seen reported elsewhere that there was a 14 minute gap between when the transponders became innactive. Wouldn't that gap lend credibility to them not being disabled by a single circuit?

joering2 13y ago
jamed by AWACS? Owners of this patent [1] were all aboard the plane. The only remaining owner is Freescale Semiconductor, owned by Rothschild family. [1] http://truthnewsinternational.files.wordpress.com/2014/03/us008671381.pdf http://truthnewsinternational.files.wordpress.com/2014/03/us...
- _delirium 13y ago
  That patent seems like a thin hook to hang a conspiracy theory off of. It looks like a run-of-the-mill "optimize placement of stuff in a slightly different way than other people have done" patent, of which there are at least hundreds yearly.
  - joering2 13y ago
    um, "optimize placement of stuff in a slightly different way than other people have done" and save billions of dollars over the span of time, due to very high price of silicon wafers? ok.
    - _delirium 13y ago
      Most likely not; it's just another minor process variation, like the thousands of such patents that exist. Is there evidence that this patent is a particularly novel or important one? And furthermore, what motive would someone have to knock off the inventors when they no longer even own the patent? If you look in the document, you can see that it has an single Assignee, Freescale Semiconductor. When a patent has been "assigned", the original inventors give up any proprietary rights in the invention to the Assignee, which is the normal process with corporate patents.

threeseed 13y ago

Makes you wonder about the logistics of this all. Moving around the plane opening hatches and tinkering with equipment requires there to be at least a few people. One to do the work, one inside the cockpit managing the flight and one looking after the passengers. All of them you would assume would have guns to keep the passengers from simply rushing them. Getting multiple weapons past security surely means an inside job. And then what is the motivation for multiple people wanting to hijack this particular plane ?

Qworg 13y ago
The best I can offer for that is the 20 Freescale employees on board.
will_asouka 13y ago
Flight deck doors are secure also, and the first action on attempted hijack is divert to the nearest suitable. It looks increasingly likely that one or both pilots remained in control.
baq 13y ago
150 Chinese on board. Maybe a kid of some high Chinese party official was on board?
shimon_e 13y ago
Cargo. The cargo list has still not been released. It is speculated that the cargo was heavy as the max amount of passengers was 50 less than the number of seats.

jevinskie 13y ago

Does anyone know of a plot of the hourly satellite ping locations? The article made it sound like they contained GPS coordinates.

analog31 13y ago
From what I've read, there's no GPS in the satellite ping data, but apparently some rough estimate can be made from signal strengths.
- dylz 13y ago
  The article also says >Until just a few years ago, the satellite communication system used by jetliners didn't include data on an aircraft's location in the pings, the electronic equivalent of handshakes used to establish initial contact.
  - analog31 13y ago
    I have a personal rule to date-time stamp all data collected from experiments. I'd add GPS if my experiments weren't all stationary. The extra bit of meta-data is a lifesaver if I do something dumb and have to reconstruct what I was doing when I collected the data, for instance correlating the data with my notes or other information that I gather.
ams6110 13y ago
One is posted here. http://www.pprune.org/rumours-news/535538-malaysian-airlines-mh370-contact-lost-175.html#post8376066 http://www.pprune.org/rumours-news/535538-malaysian-airlines...
- deleted 13y ago
  [deleted]

gkoberger 13y ago

EDIT: Currently it looks like I'm completely wrong: http://hosted.ap.org/dynamic/stories/A/AS_MALAYSIA_PLANE?SITE=AP&SECTION=HOME&TEMPLATE=DEFAULT&CTIME=2014-03-15-00-22-45 http://hosted.ap.org/dynamic/stories/A/AS_MALAYSIA_PLANE?SIT... ------------------------ Disclaimer: I know nothing about planes. That being said, this seems like fodder for conspiracy theories and click throughs. Under normal circumstances, yeah, I bet it's hard to disable. However, if we assume the plane crashed, we know there was a massive malfunction -- seems more likely to me that it was a part of that.

yukichan 13y ago
I am not sure the WSJ cares much about click throughs. They are a subscription based-service. There are no ads on that page, at least not when I open up a browser with no adblocker.
jeswin 13y ago
I reach for occam's razor almost reflexively; I am inclined to think that the plane will be found around the area we lost contact. However, the fact that India and the US is deploying so many assets on the other side makes me suspect they might have some credible leads. I am guessing India is possibly working more with the US than anyone else; given that India wouldn't want China to know what capabilities they have there.
- InclinedPlane 13y ago
  Occam's razor only applies to theories that actually explain all the available evidence. That theory does not.
  - tomelders 13y ago
    It's getting to the point where whenever I see someone invoke Occam's Razor, I stop reading. People seem to think it means "The explanation is always simple", but what it actually means is "the hypothesis with the fewest assumptions should be selected." On the disappearance of MH730 it seems a lot of people are happy to make the unfathomably large assumption that this was "probably" a catastrophic mechanical failure and that the plane has crashed into the sea, despite the conspicuous absence of any evidence for this scenario such as mayday calls, or a wreckage and now, in the face of overwhelming evidence that directly contradicts the theory that the plane has crashed (because it appears to have been under the control of a skilled pilot for five hours after it went missing, and skilled pilots are usually pretty good at landing planes) people are still positing the notion that the plane has crashed and that Occam's Razor somehow supports this point of view. In short, "the most likely explanation" in this case, is the one that makes a boat load of wild assumptions.

Thiz 13y ago

Occam's razor, the plane exploded in mid air. Not even time to mayday.

cavejohnson 13y ago
How does that explain the four hours of satellite pings after the transponders cut out?
- sorahn 13y ago
  Yeah, and where is the plane? Even in a million pieces, some of them should be somewhere.
  - rosser 13y ago
    All of them are somewhere. They're just somewhere in a really big ocean.
LoganCale 13y ago
No. The latest evidence shows that it flew on for hours afterwards and continued responding to satellite pings. If it exploded at the point where the transponder went offline, debris would have been found in that area by now.
logicallee 13y ago
Occam's razor is that nuclear power plants don't exist, they're just coal power plants (which already existed) with a story about nuclear power being possible. After all, do you have any idea how complicated controlled fission would have to be? It's easier if it doesn't exist. The problem with this "theory" is that it doesn't explain all the evidence. Sure, a hijack would have to be way more complicated than a mid-air explosion, just like a nuclear power plant would have to be way more complicated. But a complicated set of transponders turning off with sudden radio silence is exactly what happened. Plus, if it was a mid-air explosion - where are the pieces?
- 13y ago

mutagen 13y ago

Anyone interested in this event or feeling inclined to speculate on the cause, mechanisms, and outcomes of the disappearance of Flight 370 should read a couple of the most recent threads on the topic over at airliners.net[1]. Their forums are the equivalent of HN for pilots and other aircraft professionals and are a fascinating read anytime an aircraft event is worth discussing. [1] http://www.airliners.net/aviation-forums/general_aviation/read.main/6024376/ http://www.airliners.net/aviation-forums/general_aviation/re... - Currently the most recent thread.

ams6110 13y ago
pprune.org is another one

hindsightbias 13y ago

You don't need an expert if there's a fire in the cockpit: http://www.avherald.com/h?article=44078aa7&opt=0 http://www.avherald.com/h?article=44078aa7&opt=0 Answers are in the past.

kayoone 13y ago

Or it might have just malfunctioned because of other fatal malfunctions leading up to the Crash.

ronnier 13y ago

Malaysian investigators conclude flight hijacked. http://www.cbsnews.com/news/malaysia-airlines-flight-370-more-sinister-theories-still-no-answers-in-search-for-missing-plane/ http://www.cbsnews.com/news/malaysia-airlines-flight-370-mor...

romanrage 13y ago

Well, the question is still is Missing Malaysia Airline Plane MH370, Where It Disapear ? http://feedingnew.wordpress.com/2014/03/13/mystery-of-missing-malaysia-airline-plane-mh370-where-it-disapear/ http://feedingnew.wordpress.com/2014/03/13/mystery-of-missin...

bdonlan 13y ago

The article talks about needing to pull a circuit breaker to kill the transponder - I thought the transponder had a mode selection switch on the pedestal that could be set to standby; is there something else to it that I'm missing?

choult 13y ago
Presumably it needed total disabling, not just switching off...

lazyjones 13y ago

The 777 is fully FBW apparently and many (all?) sensors communicate wirelessly. What are the chances that it was hacked by a passenger or remotely and taken over this way?

noir_lord 13y ago
None-zero but then most events are.
gvb 13y ago
Wireless sensors? [Citation needed] I don't have direct experience with the 777, but do with the 787 and other aircraft systems. I am not aware of any wireless sensors. There are a lot of sensors which communicate with the various computers over multiplexed wired data buses. ARINC 429 is a legacy, but still heavily used, digital data bus. ARINC 629 is used on the 777. ARINC 664 is used on the 787 (and Airbus A380). The military systems and some commercial systems also use MIL-STD-1553 and other digital busses. All wired. Ref: http://en.wikipedia.org/wiki/ARINC http://en.wikipedia.org/wiki/ARINC
snom380 13y ago
It's fly-by-wire not fly-by-wireless.

joyofdata 13y ago

If this was a movie plot it would be bashed for being unrealistic ... "It doesn't make any sense somebody could hijack a plane that easily - you know, just deactivate the transponder and be gone - it's not that simple, of course - that would be ridiculous - and there is radar everywhere. Also the earth is covered with photo satellites - they would find the plane in no time - you know, a plane is a pretty big thing - haha - so anyway, bit naive, but the acting was alright - so if it wasn't about the transponder plot hole I'd give it a solid 8 ..."

heartbreak 13y ago
If? You mean when this story becomes a movie plot. I give it one year after they find it.
- tomelders 13y ago
  This seems like a great place for me to add my wild and crazy crack pot 99.99% likely to be total nonsense theory to the cacophony of other similar theories... which would make a great plot device for a movie none the less. I'll give you the cliff notes version When handing over from one ATC to another, MH370 adopted the identity of another plane in the area, and the other plane switched off it's transponders (let's call this other plane AB123). Leading to a scenario where the whole world is looking for a plane in the sea when it's actually airborne, but just happens to look like another plane on radar, and they landed it at some backwater airport (AB123's destination) that's under terrorist control (for example, how big a team would you need to take over Port Blair Airport on the Andaman islands? I'm guessing not very many, and no would be any wiser if you ran it as normal) But why do this? Because whoever stole this plane needs to be able to fly MH370 into someones airspace unnoticed to do something bad, and flight AB123 is scheduled to fly into that airspace sometime soon, but if flight AB123 had been hijacked, or had gone missing, it would raise alarms. But to the outside world, flight ABC123 is fine, it's MH370 that everyone is worried about... but flight AB123 is MH370. So where is AB123? I don't know. Maybe thats the plane the oil rig worker saw crash, or maybe they figured out some other way to hide it. Perhaps both planes flew to AB123's destination, but with one flying directly above the other so that it looks like one plane on radar (I don't know how Radar works but this would work for a movie) Also, AB123 might not be a passenger jet, it could be a cargo plane, or some other kind of plane that doesn't come with a bunch of passengers that people would miss. Anyhoot, that's my crazy theory and even I don't believe it, but a small part of me hope's it's right because the people on Flight MH370 could still be alive. At the very least, I think this is a good plot for a movie.

mstrem 13y ago

I get the feeling no one has a clue yet. It is easy to come up with theories... e.g. Malfunction in plane - transponder turns off - cabin loses pressure (and everyone on plane goes unconscious or similar) - because cockpit is locked crew does not manage to do anything in time - plane keeps on going - fuel runs out. of course that is probably totally wrong. One thing though - if it did fly low over land - I would expect at least someone would have used their cell phone - so I would rule out that option.

vannevar 13y ago

Everyone seems to be jumping on the hijacker theory, but I have yet to see any evidence to contradict the theory of a fire aboard the plane. It explains the sudden course change, the failure (or deliberate shutdown) of some electrical circuits, and the altitude change (an effort to starve the fire of oxygen in the unpressurized regions of the aircraft). It seems like aircraft fires occur more often than hijackings. Is there any reason at this point to prefer the hijacking theory, other than that it's a bit more sensational?

TrevorJ 13y ago
The engines 'phoned home' long after the plane went off the radar so to speak. The altitude data has also been said to be unreliable.
- vannevar 13y ago
  That doesn't contradict the fire theory, though. It simply means that the fire didn't directly bring the plane down, but it could still have incapacitated some of the systems and possibly the crew.
mpyne 13y ago
But it doesn't explain why none of the flight crews bothered to let any of the ATCs know that they had a fire on the plane...
hga 13y ago
Responding to mpyne: you can envision scenarios where the fire took out their radios. TrevorJ is a lot closer to the mark, although it wasn't the engine system phoning home, it was some sort of generic hourly "ping" with no other content (since the airline didn't sign up for the service that would have done more). Since these were pings from or to IMARSAT geosync satellites, very rough estimates of where the plane could be have been were made from them. I assume based on which satellites heard them (vs. ones over the horizon), perhaps comparing time-stamps and transit times to 22,000 miles in orbit, etc. But of course the bottom line is that these pings went on for hours, which evidently would only stop when the engines stopped for whatever reason. That makes a plausible fire scenario more complicated.

georgeecollins 13y ago

Here is my conspiracy theory: If you were the FSB, you would want to distract popular attention from events in the Ukraine. A lack of news coverage of the events in Crimea takes the heat off Western leaders to look tough.

Myrmornis 13y ago

I haven't seen any explanation of the statement that the plane's location was thought to be within one of two "corridors" in completely different places -- a northern one extending to Kazakhstan and a southern one extending into the southern Indian Ocean. Is this indeterminacy expected? Is it the result of some sort of geometrical symmetry? I imagine someone here knows?

hga 13y ago
It's based on the reception of the pings at the IMMARSAT geosync satellite. Look at a picture, e.g., here: http://en.wikipedia.org/wiki/File:MH370_last_ping_corridors.jpg http://en.wikipedia.org/wiki/File:MH370_last_ping_corridors.... The "corridors" are actually geometrically symmetrical arcs as you suspect, somewhere around which it's believed the plane traveled until the pings stopped, presumably because the engines stopped running.
- hga 13y ago
  The map I directed to you was apparantly an enhanced one from the NYT; here's one with many more details figured in: http://www.nytimes.com/2014/03/17/world/asia/malaysia-airlines-flight.html?hp http://www.nytimes.com/2014/03/17/world/asia/malaysia-airlin... although I wouldn't treat those boundaries as gospel, there's likely more slop in the real estimates derived from the satellite.
- Myrmornis 13y ago
  Thanks! According to sources [1, 2] there was a period of time during which it was pinging multiple satellites. Surely this symmetry doesn't persist in a dataset comprising pings at different times to different satellites (which themselves are moving)? [1] https://en.wikipedia.org/wiki/Malaysia_Airlines_Flight_370 https://en.wikipedia.org/wiki/Malaysia_Airlines_Flight_370 [2] http://edition.cnn.com/2014/03/14/world/asia/malaysia-airlines-plane/index.html?hpt=ias_c1 http://edition.cnn.com/2014/03/14/world/asia/malaysia-airlin...
  - hga 13y ago
    They're in geosynchronous orbit, so they rotate with the earth, are always over the same spot on earth at the equator. Don't know which satellite series is used for this service, but the Inmarsat constellations aren't particularly large: http://en.wikipedia.org/wiki/Inmarsat#Satellites http://en.wikipedia.org/wiki/Inmarsat#Satellites, so it could be they only got solid data---and it's not very specific---from one satellite. I also wouldn't put much confidence in mass media reports saying "satellites", and the Wikipedia plural use is probably based on them.

cfreeman 13y ago

Is there any legitimate reason for the pilot to disable the transponder? It seems like they should make it more difficult than just throwing a breaker in the cockpit.

lutusp 13y ago
> Is there any legitimate reason for the pilot to disable the transponder? Yes, of course -- any piece of electronic equipment might (a) begin to misbehave and interfere with other equipment or produce misleading results, or (b) catch fire and emit smoke into the flight deck, or (c) both. It's common sense to have a way to disable any piece of equipment on short notice. I played a small part in the design of NASA's Space Shuttle many years ago, and we definitely kept the possibility of equipment failure in mind at all times. > It seems like they should make it more difficult than just throwing a breaker in the cockpit. On board an aircraft, the pilot has the highest authority. You don't expect to have to protect the aircraft from him -- more the reverse. That is why, when a pilot goes crazy, the results are usually catastrophic.