Non trackable aircraft

[lorenzo]

Yesterday, 15th January, a friend told me he would fly Cathay pacific Airbus 340 from London, Heathrow to Hong Kong leaving at 2145.
Flightradar24 informed me that Cathay pacific did not have any such flight last night and did not show it on radar! Even though Heathrow departures told me the aircraft got airborne at 17 minutes past the hour there was nothing on radar.
Would someone please explain to me how an Airbus 340 can fly out of Heathrow and not be seen on Flightradar24?

[netjets]

Hi Thats well weird, as I was spotting in my garden today and a Cathy 340 went over head going into heathrow and it did'nt come up on flt radar so couldnt get reg?

[Albin]

That's strange indeed.

However you can see on http://data.flight24.com/flights/cx256/ that it was B-HXK that flew the flight CX256 yesterday (I assume that's the flight we're talking about)

So it is in the logs, that it doesn't show up on Flightradar24, I believe that it's something that is a problem with the airplane, not the website.
It might be that pilots has turned the transponder off, faulty equipment etc.
That's what I believe..

[OFBleeker]

It would most likely be a problem with the aircrfat ADS-B sub function. ADS broadcast is a 'not-required' subfunction of the Mode-S transponder, so if there would have been a failure with any one of the enabling logics, it would not create a dispatch issue (as opposed to the transponder main function). ADS-B is currently not required over Europe (except for some non-radar areas like low level North Sea helicopter operations); perhaps that explains.

[Anmer]

From my own logs, flight CPA256 departing LHR on 15th January 2012 was flown by B-HXK (check the times logged by FR24 and you will see B-HXA was recorded at 01.41 CET on 15th and would have left LHR on 14th).

B-HXK has a Mode-S transponder which provides a callsign but doesn't transmit positional data. That explains why it's in the database but wouldn't have appeared on the FR24 map.

[OFBleeker]

OK yes that confirms (no failure, just not enabled)

[trailfinder]

Hi

The Heathrow to Hong Kong flight at that time is CPA254 normally a 747. This flight is the return flight of CPA253. As my neighbours were on CPA253, I was tracking it, and it arrived late at 11:45. The outgoing flight did not take off until after 1:30am Monday.

Hope this is of help.