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Also people were making voice calls and texting from the aircraft that crashed when the passengers overcame the hijackers on 9/11, so it is technically possible to use your mobile on an aircraft if you are overflying a mobile network.
AIUI (from watching the film). They were using the phone system build into seats - which uses a satellite link off the plane.
Radio masts do not 'point' in any direction. Radio waves radiate in all directions.
Hmm, I can tell you're not a Radio engineer as people spend a *lot* of money making sure that antennas are directional. It's a very large and complex business. The measurement units of directionality, or gain, is 'dBi' which is [i]deciBels relative to an Isotropic antenna[/i]. An Isotropic antenna is one which radiates uniformly in all directions and is a theoretical construct as you can't actually make one...
If you still don't believe me, have a look here: http://en.wikipedia.org/wiki/Sector_antenna
NB one of my first jobs after graduating was working on the design of a re-spin of the BSkyB 'Squariel' antenna for Nortel. I did the matching circuit in microstrip in case you asked. Used to see them in the UK 20 odd years ago. It was highly directional, as had it not been you'd have never got a TV signal! http://en.wikipedia.org/wiki/Squarial
I did hear something about possibly recover via passive scanning. I would imagine/hope that it is fitted with something similar to the RECCO system used in ski/snow wear which reflects an incoming signal without requiring on-board power.
They are a pinger that starts transmitting when it enters the water. Relatively high frequency too so pretty short range underwater. If they were fitted active transponder instead then you could ping them and get a response.battery would last much longer too.
I did hear something about possibly recover via passive scanning. I would imagine/hope that it is fitted with something similar to the RECCO system used in ski/snow wear which reflects an incoming signal without requiring on-board power.
Passive scanning is pretty lossy, hence very limited range - similar to radar, you need a lot of power to cover an area.
Recco isn't quite a reflector, there are two antennas in the device and a diode (non linear element). The Search device sends out a signal on one frequency, which energises the first antenna. The diode, being non linear, create a harmonic spread, and the second antenna, being tuned to the wavelength of twice the original frequency, will transmit a week frequency doubled signal back.
The reason for the complexity is that it eliminates reflections, which would come back at the original 'search' frequency. If you pick 2x f coming back, you know there must be a RECCO device under the snow.
[quote=footflaps ]NB one of my first jobs after graduating was working on the design of a re-spin of the BSkyB 'Squariel' antenna for Nortel. I did the matching circuit in microstrip in case you asked. Used to see them in the UK 20 odd years ago. It was highly directional, as had it not been you'd have never got a TV signal! http://en.wikipedia.org/wiki/Squarial
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Ah - you trump me on professional knowledge of this (I've worked with people who designed antennas, but never been into that sort of thing myself - mainly modelling and protocol stuff, though a bit of real world propagation and coverage testing). I figured as much from your previous replies.
I note that I've always measured antenna gain using plain old dB units, and I think even those people who were proper RF engineers did the same, though it's kind of a minor point.
Passive scanning is pretty lossy, hence very limited range - similar to radar, you need a lot of power to cover an area.
Yep agreed.
Got to help when searching for a black box that has lost power and stopped transmitting though eh?
How did they find the black box form that French one mentioned earlier that took ages to find?
How did they find the black box form that French one mentioned earlier that took ages to find?
They found the wreckage using AUV's with multibeam and sidescan sonar. It took a while
I note that I've always measured antenna gain using plain old dB units
But dB is unit less, it's just a ratio. So they're just being sloppy and ignoring the 'i'.
In the RF world it's either dBm for dB milliwatts dBW for dB Watts (if referring to power), or dBi for dB relative to Isotropic for antenna gains. An amplifier can have a gain in dB as gain is a ratio (power out to power in).
[quote=footflaps ]
I note that I've always measured antenna gain using plain old dB units
But dB is unit less, it's just a ratio. So they're just being sloppy and ignoring the 'i'.
In the RF world it's either dBm for dB milliwatts dBW for dB Watts (if referring to power), or dBi for dB relative to Isotropic for antenna gains. An amplifier can have a gain in dB as gain is a ratio (power out to power in).
Nope - don't see why it's a problem, as unlike with dBm or dBW there isn't actually a baseline unit, what you're specifying is a ratio, not a quantity. The i is just a convenience notation rather than having the same significance as the m or the W (isotropic not being an SI unit 😉 )
I'm no expert in RF comms but I know enough to understand that radio waves do reflect off objects and the atmosphere which is why you don't need perfect line if sight for radio to work. Even radar that is focussed by a parabolic dish can be detected from a variety of angles - something the military exploits with great effect, the strength of the signal may be very weak and diminished, but it's there. When I've sent texts from an aircraft it may very well have been at a very low level, it was certainly after takeoff, so not a handful of feet from the ground, but my point is that it's possible.
I'm not so sure all the 9/11 calls were made from the on-board in-seat system. I've never known those systems to be even functioning when I've had a play with them and I doubt they are even installed on a clapped out aging American Airlines B757/767. Have you ever flown AA in economy? The last time I flew them in 2003 ish they still had roof mounted CRT TVs above the isle rather than individual seat mounted LCD screens. Their idea of inter-seat communication is a couple of polystyrene cups and a length of string. They're refreshing their fleet now, but back in 2000 they had a very very tired fleet.
The explanation I read was that in 2001 mobiles and base stations were more powerful, so had greater potential range. No idea if that's accurate.
I think in 11th sept 2001 the plane was flying low and slow whilst the baddies worked out what there next move would be.
The explanation I read was that in 2001 mobiles and base stations were more powerful, so had greater potential range. No idea if that's accurate.
Possibly true, the early analogue systems had better range in the UK. America always was different though and used their own systems e.g. Ignoring GSM for years and letting Ericsson and Nokia dominate the world market whilst US manufacturers just focussed on the home market.
The US analogue system, AMPS, was still in use in 2001: http://en.wikipedia.org/wiki/Advanced_Mobile_Phone_System
Actually my post above is wrong this [url= https://www.hsdl.org/?view&did=478665 ]report[/url] has the plane cruising at 35kft when the hijack occured and climbing to 41 k. Then diving. The calls are a mixture of in seat and mobile, they must have made the mobile calls somehow.
reading what passes for detail in the Aus Herald Sun pretty good chance got a fix of sorts on a black box 4500m down
goes back to reading aussie rules footie results
So have the Chinese found the needle in the haystack.
[quote=avdave2 ]So have the Chinese found the needle in the haystack.
It certainly seems quite likely, as it's hard to imagine what else the signal they're detecting could be from - unlike all the debris spotted - though I guess it's possible it's just their instrumentation playing up. If they have then that's quite incredible given the size of the haystack - you have to wonder whether they have some extra information.
you have to wonder whether they have some extra information.
Indeed, lets see if Sir Dickie trips them up.
If they have then that's quite incredible given the size of the haystack
would need to go and look for it (no that's not a joke) there was a quote from the Aus' guy running the search out of Perth that went something like "they say its like searching for a needle in a haystack - the problem is we haven't found the haystack"
think that Chinese vessel is pretty much state of the art technology
edit but it being in the right place can't be just luck
[img] 
[/img]
That's a great graphic, kimbers.
following on from Kimber's graphic its pretty obvious that a guy in a snorkel mask will be the best way to find the plane
picture caption "A fast response craft from Australian Defence Vessel Ocean Shield tows Able Seaman Clearance Diver Michael Arnold as he searches the ocean for debris in the search zone in the southern Indian Ocean for the missing Malaysian Airlines flight MH370"
link to story and pics
http://www.theage.com.au/world/missing-malaysia-airline-jet-ocean-debris-would-depend-on-angle-speed-experts-20140409-zqsg6.html
Wow - two more hits from an FDR. They must have found the haystack at least. 🙂
interesting report in the guardian today about an unrelated incident, galley fire on a [url= http://www.theguardian.com/world/2014/apr/10/british-airways-jet-fire-re-ignited-crew-jumbo ]BA 747.[/url]
What makes it relavent to our discussion here is that the crew had difficulty putting the fire out with extinguishers, and did not follow correct procedures (ie not wearing oxegen masks, not electrically isolating the area etc) .
Which opens the mind to various scenarios on mh370.
[quote=toys19 ]Which opens the mind to various scenarios on mh370.
Well apart from the aircraft keeping flying for hours and making several controlled turns obviously.
The metal objects they've found off the coast of Australia aren't the plane, they are Rolf Harris' laptops.
making several controlled turns
This is supposition.
Well I suppose it is also supposition that the plane ever existed. I mean it's not like I've seen it with my own eyes - it could all be a conspiracy. I could just ignore all available information on that in the same way you appear to be ignoring the confirmed radar tracks and final location area.
I could just ignore all available information on that in the same way you appear to be ignoring the confirmed radar tracks and final location area.
I am not ignoring it, given that they have likely found the black boxes due to the pinger contact, I'm just wondering how it got there. Jeez you are looking for an argument/disagreement when there isn't one.
[quote=toys19 ]I'm just wondering how it got there.
Presumably it followed the confirmed radar track and then turned left once out of radar range and not needing to overfly anywhere else with radar coverage.
[quote=toys19 ]Jeez you are looking for an argument/disagreement when there isn't one.
I disagree that the confirmed radar track is "supposition"
no the suppostion part is that
implies that they were deliberate, and or nefarious.making several controlled turns
Well you suggest a plausible scenario in which the aircraft follows the confirmed radar track and keeps flying for several hours, where the turns (and subsequent return to straight and level) aren't deliberate.
"The metal objects they've found off the coast of Australia aren't the plane, they are Rolf Harris' laptops"
all the way from Henley on Thames ?
Well you suggest a plausible scenario in which the aircraft follows the confirmed radar track and keeps flying for several hours, where the turns (and subsequent return to straight and level) aren't deliberate.
Of course , it is most likely to be person or persons on baord deliberately crashing the plane.
I'm just trying to point out that outlier occurrences happen on aircraft, that is why we lose them. And the link I referenced above shows how despite the training and the protocols, people forget all that and make big mistakes.
I'm not looking for a row, merely a discussion of pissibolities.
[quote=toys19 ]I'm just trying to point out that outlier occurrences happen on aircraft, that is why we lose them.
They do, but not in this case. I'm not sure of the point in raising or discussing aircraft failure when it's so clear from the known evidence that's not what happened. Beyond reasonable doubt.
Beyond reasonable doubt.
Really? Convince me.
How about you provide some reasonable doubt if you think there is some? In this case that would be providing a plausible explanation of aircraft failure resulting in the known evidence, as I asked for above...
So if they DO find the plane (Bits of) but not the Blackbox- down near Australia its safe to assume that the people onboard were overcome with smoke etc no?
If it was pilot action- he wouldn't fly to nowhere. He'd chose somewhere/have an agenda.
reasonable doubt if you think there is some
yes, there is very little evidence either way
Science does not work by proving something did not happen, where is the evidence that it was a deliberate act? Or that it was an accident? There is not any in either case, it is inconclusive. You just cannot draw any conclusions from what we know.
I dunno where you get your beyond reasonalbe doubt from. I previoulsy showed you that they were not sure that the comms were turned off before or after the last radio contact, which you accepted. I think that was what you based your idea that it was defo deliberate. Otherwise it is all conjecture. I see no evidence that it was deliberate or not.
[b]Again, convince me.[/b] You are so convinced, what is it that convinces you? What am I missing that you can see?
So if they DO find the plane (Bits of) but not the Blackbox- down near Australia its safe to assume that the people onboard were overcome with smoke etc no?If it was pilot action- he wouldn't fly to nowhere. He'd chose somewhere/have an agenda.
Who knows. It's impossible to know what the state of a pilot who'd choose that course of action is, mentally speaking.
He'd chose somewhere/have an agenda
what if he chose the middle of the indian ocean...
yeah I reckon if you are suffciently mental enough to take over the plane with a view to ditching it, you might be mental enough to do something unpredictable like fly to australia.
[quote=hora ]If it was pilot action- he wouldn't fly to nowhere. He'd chose somewhere/have an agenda.
The whole point is that pilot action is the only way to end up where they did.
The evidence we have is that the plane made a number of controlled turns, in between which it followed a steady course and followed exactly the course you would choose if you intended to avoid detection (for as long as possible) and end up in the middle of nowhere. It also flew on for hours. All after the transponder and ACARS stopped transmitting and there were no more voice comms (despite the satcom clearly working) all coincidentally happening at the point where it would take longest to be missed.
What I was suggesting is beyond reasonable doubt is that this was not the result of aircraft failure. I do not have to provide an explanation of what actually happened for that assertion. Let's just for a moment consider what you are suggesting if aircraft failure is actually a plausible scenario:
The failure is of sufficient severity to take out all other comms, yet leave the satcom sending keep alive messages. This all happened so fast that it was impossible for the crew to send a distress message. The crew were either disabled or unable to control the aircraft. Yet the failure isn't sufficient to stop the aircraft flying for hours largely flying straight and level and making a number of uncommanded turns, each of which it recovers from to straight and level flight rather than going into a spin.
There is no feasible aircraft failure which would result in that - the vast majority would not allow the aircraft to continue flying for hours. There is no possible failure mode which would result in uncommanded turns of the type recorded. In contrast the only thing we are missing from the scenario of deliberate pilot actions is a motive and I could find plenty of examples we know about of people doing unlikely things. In order to have reasonable doubt that this was not a result of aircraft failure there would have to be a plausible scenario where it is as a result of aircraft failure. There is not one.
I'm still not sure why people place so much importance on the lack of obvious motive. This does not have equal weight with the physical impossibility of any other scenario.
I pretty much agree with aracer - still think it could have been hijacked by somebody semi-trained. Lack of motive just means we haven't understood someone's motive yet.
I agree, I'm not concerned about lack of motive. I also do not think that striking out the idea of pilot suicide because he didn't do it straight away is valid either. Jumpers spend hours deciding wether to go or not. He/she may well have vaccilated until the fuel ran out.
I guess reading aracers post, his assumptions are the most plausible. BUT they are still assumptions. We know very little. We do not know that they were deliberate turns.
As an avid flying phobic I have read many many NTSB/AAIB reports and can tell you that truth is stranger than fiction.
Given that flight safety is so locked down and there are protections, procedures and redundancy in palce. Whn a plane crashes by accident the causes are often very obscure.
So all I am saying is, whislt Aracer is enjoying his sense of certainty, I am happy to leave my mind open that it might have been aracers theory or some other incredible/black swanish that caused this incident.
[quote=toys19 ]We do not know that they were deliberate turns.
We know that they look like deliberate turns and that there is no known aircraft failure mechanism which would result in that.
or some other incredible/black swanish that caused this incident.
That's the thing - any other possibility is incredible. We come back to my post at the top of this page - to some extent we can never be totally certain about anything - even eyewitnesses are unreliable. It's also worth bearing in mind that in courts of law, an awful lot of evidence is "circumstantial". Is there actual reasonable doubt - with emphasis on the word "reasonable"?
Though it's nice to be able to have a sensible debate on this, and I don't think there's actually much difference in our positions 🙂
Though it's nice to be able to have a sensible debate on this, and I don't think there's actually much difference in our positions
yeah I agree, I think we just place more weight on different things.
Like I am not sure that this is true, it sounds more of an assumption to me
But I see your point, it would have to be pretty coincidental that through some failure mechanism it navigated itself throuhg a couple of well knwon waypoints. But it is possible.that there is no known aircraft failure mechanism which would result in that.
it would have to be pretty coincidental that through some failure mechanism it navigated itself throuhg a couple of well knwon waypoints
Could these turns have been made by the autopilot? i.e. I'm thinking crew incapacitated/dead for some reason and autopilot continues on to bogus waypoints (either by user error, system fault or deliberate interference).
Could these turns have been made by the autopilot? i.e. I'm thinking crew incapacitated/dead for some reason and autopilot continues on to bogus waypoints (either by user error, system fault or deliberate interference).
Exactly.
So the pilot programmed the autopilot to take the plane into the Indian Ocean and then there was an unrelated disaster that killed him, the crew and passengers? Stretches belief a bit.
[quote=atlaz ]So the pilot programmed the autopilot to take the plane into the Indian Ocean and then there was an unrelated disaster that killed him, the crew and passengers? Stretches belief a bit.
Indeed - that would involve both the pilot doing something weird AND the plane having a failure which incapacitated everybody and took out the comms (but left the rest of the avionics alone).
Though I think Graham is actually suggesting the autopilot following a course which hadn't been programmed into it. At which point we're into the realms of an incredible number of coincidences where the aircraft fails in a very specific way, taking out some systems, having unprecedented and unrepeatable faults in others, leaving some running perfectly and incapacitating the crew whilst it's at it. All resulting in the aircraft doing exactly what a pilot wanting to disappear would do. I suppose it s possible, but it fails the "reasonable" test. What's more I don't think anybody has identified a mechanism for the autopilot to generate a new route all by itself - certainly not one which actually keeps the plane flying.
I was mainly just wondering if autopilot might explain the turns and continuing flight, while there was no radio comms etc going on.
No idea what the scenario would be that lead to that situation obviously, but for speculation sake:
1) some kind of weird system failure (or deliberate attack) that incapacitates the crew/passengers and damages/corrupts the navigation equipment causing autopilot to follow a bogus course.
2) psycho crew member kills crew, sets autopilot for the middle of nowwhere then tops himself, leaving the passengers to their fate and unable to enter the cockpit.
3) zombie outbreak on board. Pilot realises that without a handy Brad Pitt they are all doomed, so heroically sets course to take them away from civilisation before the undead break down the door.
3) zombie outbreak on board. Pilot realises that without a handy Brad Pitt they are all doomed, so heroically sets course to take them away from civilisation before the undead break down the door.
Definitely this one.
It's certainly more plausible than option 1.
I freely admit option 1 is extremely unlikely to be a purely accidental system fault (though that doesn't mean it should be ruled out completely).
I am slightly concerned about the attempts to recover the black boxes though. As we know that a Zombie outbreak was the most likely cause of the crash and that the undead can't drown, trying to reach the wreck risks unleashing a zombie apocalypse upon the world.
They are so far down I'm assuming that the Abyss aliens have dealt with them.
I was mainly just wondering if autopilot might explain the turns and continuing flight, while there was no radio comms etc going on.
Helios 522 shows that this is possible, but it doesn't explain the course the plane flew. Gotta be pilot action, I think - everything else is just too outrageous.
[quote=pondo ]Helios 522 shows that this is possible, but it doesn't explain the course the plane flew.
It shows it's possible for an aircraft to keep flying with an engaged auto-pilot when the crew are disabled - but then we knew that already, as that's what the auto-pilot is supposed to do. It's only the latter part which is problematic.
The only way to change the FMC routing the aircraft will follow, is by manual entry by the pilot.
What is possible, is that some new waypoints were entered by a pilot, before being overcome by fumes/decompression.
When the plane reaches the last waypoint in the flight plan, it will continue to fly on the last heading.
It is possible that the last leg entered by a pilot before being overcome was in the direction of the southern ocean, without having ever intended to fly there.
As magnetic variation changed over a long period, the ac would have gently turned on the curved flight path seen on most of the graphics.
It is possible that the last leg entered by a pilot before being overcome was in the direction of the southern ocean, without having ever intended to fly there.
This.
As magnetic variation changed over a long period, the ac would have gently turned on the curved flight path seen on most of the graphics.
Not this. The curved line on most of the graphics shows range from the satellite (which was much further west) when contact was lost ie. the aircraft *crossed* that line shortly before it ditched.
As magnetic variation changed over a long period, the ac would have gently turned on the curved flight path seen on most of the graphics.
I think you'll find that's just an artifact of mapping a sphere onto a flat plane.
The only way to change the FMC routing the aircraft will follow, is by manual entry by the pilot.
That is a very definite statement.
What prevents other people changing it? It is securely-protected in some way? Password, key, voice ID? Is the system itself secure and tamperproof at all times (i.e. when the plane is on the ground)? Is it impossible for the system to be faulty (i.e. multiple redundant systems) or does it rely on pilots being conscious to spot issues?
The flight management computer (FMC) of a modern airliner is a standalone computer, with the only data input for navigation via a keypad. There simply isn't any way of manipulating it externally.
If you take a magnetic heading to a point 500nm away in the southern ocean, and fly on that magnetic heading for 500nm, you will miss the point you were aiming at, due to changes in magnetic variation.
Elliptical, you are talking about the arcs showing the satellite range - I am talking about the arrows showing the likely flight path of the ac.
Actually, having just checked a chart, the southern ocean is one of the few places on the planet with little change in magnetic variation - much more relevant somewhere like the North Atlantic.
The flight management computer (FMC) of a modern airliner is a standalone computer, with the only data input for navigation via a keypad. There simply isn't any way of manipulating it externally.
Presumably the pilot can alter it, so are you saying another crew member couldn't change it?
A hijacker couldn't put a gun to the pilots head to change it?
There is no possibility that such a computer could be tampered with while the plane was on the ground (i.e. say dodgy firmware installed on it)?
Anybody in the cockpit could change it. IMHO external hacking isn't possible.
A hijacker with knowledge of flying could do it if they gained access to the flight deck, exactly what happened on 9/11 I believe
IMHO external hacking isn't possible.
Professionally speaking I'd say it is certainly [i]possible[/i], but I agree it is very unlikely.
Well there is an airgap, which is usually considered one of the best forms of security, but not infallible, no.
Yeah I didn't mean someone could hack it from the ground as the plane was flying (assuming it is properly air-gapped). I was more thinking about the potential for someone maliciously tampering with the flight/navigation software while the plane was on the ground (e.g. dodgy maintenance engineer).
Extremely unlikely, but not impossible.
Still think it was a zombie outbreak though.
If anybody managed to hack the software on the ground prior to flight, it would be pointless, as the pilots would just disconnect the autopilot and fly manually.
The only vaguely plausible explanation for the unusual entry of waypoints is a nutter pilot, or an aviation trained hijacker on the flight deck. Hopefully they find the CVR so we can find out.
I think it was an outbreak of snakes on the plane; everyone was running around, screaming and distracted, until the plane flew into the sea.
More likely than some of the tosh in the media!!
heard an interesting titbit this morning.
the pings heard were at 33 KHz not at the 37.5 KHz that the black boxes should operate at.
guess what operates at 33 KHz...
Mobile phones?
Is it the resonating frequency of 650b wheels?
close.
your common echosounder, probably found on every ship in the world.
jam bo - Memberclose.
your common echosounder, probably found on every ship in the world.
So they were chasing the other search ships?
So in summary, they still have no idea where the plane is / was / will be.
Is disappoint.
I'm sticking with my original theory.
Aliens.