12/09/2010

A day (almost) without aircraft

When the airport was closed on the day of the snow (1 December) it was interesting to see what activity was registered by the ARAG aircraft monitoring system!


When there is a day where the standard events don't happen, it is always interesting to look at what is left: the non-standard events that generally stay (literally and figuratively) under the radar. I used that day to see how little aircraft movement was registered around Geneva airport.

The first surprise was that there were still a lot of aircraft passing above us, with the monitoring system dealing with about 65 aircraft transponder transmissions per second (against a normal average of about 90).Particularly strange, however, were two objects which claimed to be stationary way above all other passing aircraft: callsigns FMDOLSA1 at 61000 feet and FMDOLSB1 at 60000 feet. Flying saucers?

The next was that there were very many such ttransmissions coming from things on the ground at Geneva airport. I say "things" because, although their identification numbers indicated Switzerland, they did not correspond to known aircraft. They did, however, quite often include call signs appropriate to the day: I particularly liked Iceberg, Igloo, Frigo, Yeti, Glacier and Esquimau.

Some emissions were actually from real aircraft on the ground, with my favourite being the easyJet Airbus A319 registered as HB-JZU and sending out the callsign EZS1409 (a flight to Barcelona) at 3.45 am. Slightly optimistic, unfortunately.

The real oddity, however, was that one particular aircraft jet aircraft had sent messages saying that sometimes it was on the ground, whilst at other times it was airborne at a constant altitude of 1875 feet. OK, we know that the altitudes registered are often very inaccurate, so maybe it was bumping over snowdrifts or being transported around.

These transmissions did fool the aircraft movement recognition program. This program operates in real time, so has to make quick decisions, and it thought that the aircraft had gone up and down a couple of times. There is actually an off-line verification program which runs at a later stage, and which would normally eliminate it, but I have stopped that for the curiosity value.

I am told that in France an airport does not say that it is closed, but rather that flights are suspended. A rose by any other name.

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