Missing Malaysian Aircraft – is it possible…

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 deciBels relative to an Isotropic antenna. 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.

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).

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).
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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 report 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

http://www.heraldsun.com.au/news/world/second-signal-heard-during-search-for-black-box-from-missing-malaysia-airlines-flight-mh370/story-fni0xs61-1226875948524

goes back to reading aussie rules footie results

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

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 BA 747.

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.

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.

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.

I disagree that the confirmed radar track is “supposition”

no the suppostion part is that

making several controlled turns

implies that they were deliberate, and or nefarious.

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.

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.

Again, convince me. 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…