Hacker News Reader

Comment by joeconway | Hacker News Reader

I appreciate that radar only works above a certain altitude, but can someone explain to me why a vehicle worth > $200m doesn't have a GPS unit broadcasting over longwave radio,satellite connection or some other remote communication means. I feel like I'm missing something fundamental.

View on HN

All modern aircraft are equipped with Mode-S transponders [1] which broadcast several parameters such as altitude, lat/longitude and aicraft ID info. There are also specific messages that signal "emergency status"[2].

You can 'listen' to these messages yourself with very basic radio equipment tuned to 1090 MHz[3].

Even though these signals can reach long distances (I remember getting ~300 Km with my home made antenna) it's possible that the plane was going through an area where no base stations exist.

[1]: http://en.wikipedia.org/wiki/Aviation_transponder_interrogat...

[2]: http://www.faa.gov/air_traffic/publications/atpubs/aim/aim04...

[3]: http://www.rtl-sdr.com/adsb-aircraft-radar-with-rtl-sdr/

Those signals are very much dependant on direct line-of-sight. Transmitted from the ground or on the ocean the range would be very low.

Sure. I find that I easily lose track of planes if they are below a certain altitude. Still, it is very strange that the last recorded altitude is 35000 ft [1].

[1]: http://www.flightradar24.com/data/flights/mh370/#2d81a27

OK, I found a link on reddit[1] that seems to show something more:

http://www.flightradar24.com/2014-03-07/17:20/12x/MAS370/2d8...

[1]: http://www.reddit.com/r/worldnews/comments/1zur6k/malaysia_a...

The deviation from planned flight looks odd to me.

On second thought, looking at other flights, it seems not so odd.

Deviation from planned flight is very, very common.

What looked odd to me at first was not the deviation but the fact that it seemed almost mechanical. As I looked at other flight paths vs actual flights however it became clear that this sort of deviation was relatively common.

It probably does, but if all means of communication are somehow disabled, that could be an indication that something catastrophic happened =/

All those kind of systems can fail or give inconclusive data. What you need to know is the crash site, not the last GPS trace. It would be better to include substances in aircraft that would be released in the event of breakup and be easily visible to remote sensing and radar satellites.

Doesn't longwave require a longish antenna? Plus it wouldn't work when submerged.

Yes but planes are pretty long. It would work underwater, in fact it would be nothing ordinary: http://en.wikipedia.org/wiki/Communication_with_submarines

Reply on news.ycombinator.com