[jhb_airlines] Re: Christmas Present List

  • From: "Bones" <bones@xxxxxxx>
  • To: <jhb_airlines@xxxxxxxxxxxxx>
  • Date: Fri, 5 Aug 2005 15:56:30 +0100

The transponder data is a simple binary stream so it can be easily decoded
once someone knows the format. Encryption was discussed but there are too
many other means of finding aircraft position - such as ACARS where you only
need an airband radio next to your PC and use ACARS decoding software (such
as the freebie at http://www.acarsd.org/).

The case of failures is valid - transponder DO fail and, as you will
remember with 9/11, they were deliberately turned off. Radars also fail and
there is no backup for these - all we do in ATC is revert to procedural
control (that is the old ones like me that remember how to do this). A radar
feed is actually a very easy target - just a fibre optic cable - and it
wouldn't need much to put a whole radar system out of action. I guess they
worked out that transponders and ADSB have a failure rate higher than radar.

If the satellite went down the aircraft signals would still be received but
you'd be back to line of sight range only. No great deal for TMA's but I
then think that ADSB will allow Oceanic to have a radar picture across the
Atlantic (and Pacific) for the very first time and they'd really find it
hard if they lost this.

I'd also agree about redundancy. In the US they are retiring VOR's and NDB's
as they become too aged to repair - they have scrapped the replacement
program. In Fiji they have already announced that airspace will by fully GPS
in the future and no ground based aids will be kept. It's the cheap option
and it's too appealing for politicians. So, in the future when radar and
navaids are gone and everything is running via GPS or ADSB, all you need is
one really good solar flare and aircraft have lost their navigation kit and
ATC their eyes.


-----Original Message-----
From: jhb_airlines-bounce@xxxxxxxxxxxxx
[mailto:jhb_airlines-bounce@xxxxxxxxxxxxx] On Behalf Of Alastair
Sent: 05 August 2005 09:12
To: jhb_airlines@xxxxxxxxxxxxx
Subject: [jhb_airlines] Re: Christmas Present List

As a complete layman, as far as ATC matters are concerned, a few things
strike me:-

1. I think that they are crazy not to encrypt this data. I would imagine
that this type of information would be very useful to a potential
terrorist, or some nut! that had managed to get hold of an air band
portable transceiver.

2. What happens if you have done away with all the radar screens and the
transponder goes down, or worse the satellite. Aparently satelites can
get subjected to very high levels of solar radiation if the sun is
particularly active, and the satellite may have to shut down temporarily.

3. As with GPS, I don't think that is very wise to put all your eggs in
the one basket, we all know what the Americans can do to the GPS system,
should they so decide.

Just my 1d worth.


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