Firstly I'd like to offer thoughts and prayers for all of the souls on the missing aircraft. The not knowing must be incredibly difficult.
Does anyone with any knowledge of such things know how its possible to "lose" an aircraft. I understand the limitations of radar etc, but do modern aircraft not have the equivalent of a GPS tracker... I've one built into my phone, or an EPIRB as has been fitted to all ships for decades now.
Ben, not sure at all, but does it not depend upon the ground based receivers capability/range. Line of sight also may also come into it.
Are there as many radars in Asia as there are in Europe for example?
Reports today though do mention radar may have shown it to do a 180°.
Keith
There are various trackers on aircraft, can't remember the exact term but one of them broadcasts maintenance data back to base fairly regularly for one thing so faults can be fixed on landing. However they're generally not continuous hence the delay in realising the aircraft has gone missing, I'm fairly sure at least one of them uses a frequency band that goes beyond line of sight. Of course you also need power to the radios.
As for EPIRB, they are fitted but depending on how the aircraft reaches the ground they may not work, e.g. if it hits it at terminal velocity.
ACARS is the maintenance and general info system. Transmits on VHF around 130Mhz and is further than line of sight.
ADSB is used for position tracking by ATC (what you see on FR24). That is line of sight (transmitted at 1090Mhz) but at 30,000 feet typical range can be up to 200 miles. Sounds a lot in the UK but in the Far East I suspect that is not enough to always be within range of ground stations.
Re crashes of B777, don't forget the Heathrow incident where both engines stopped producing power just before landing. Everyone survived but if it had happened 5 minutes earlier, who knows?
Last edited by ianhind on 09 Mar 2014, 17:52, edited 1 time in total.
The general rule as to line of sight range ( as with e.g. radar and ground based VHF radio aids) is the range in NM is 1.3 times the square root of the height in feet . Thus at 35000 feet AMSL the theoretical maximum distance at which primary returns can be received is about 240 NM . However, it requires a very powerful radar to achieve that and reception is also heavily compromised by e.g. heavy rainfall such as is common in those latitudes, and thus the likelihood is that the aircraft would not have descended far before its primary trace disappeared entirely . In any event, if this was a sudden event, as seems likely , it is probable that transponder power would be instantaneously disconnected and thus any signal would be wholly dependent upon primary returns
Thanks Chris, I did a lot of this stuff at college years ago, but primarily with a maritime slant. I just think its incredible in 2014 that a mobile phone can be set to log your GPS position every 5 minutes, but the same isn't done as a matter of course for an airliner or ship.
It looks like wreckage has been spotted, maybe a door but as it is dark in the search area they will start at first light,
Looks sinister to me, what with these passports that have been found that were stolen, time of course will tell and whether they can find the boxes if they are transmitting,
Nobody that i have heard have said how deep it is in that part of the South China Sea.
I have just looked at Wikipeda and the area seems to be around 148ft to a max of 260 ft.
Roger.
Better to remain silent and be thought a fool than to speak out and remove all doubt.
