ICAO 000000

FlightAware ADS-B Flight Tracking
1

Every day I get several messages with hex address 000000–no positions, just random squawks and bogus altitudes. I assume these are decoding errors? Or something else sending bad messages? It seems to happen throughout the day, so it’s not just one passing aircraft with a bad transponder.

I’m running dump1090-mutability v1.15~dev with --oversample --fix --phase-enhance

some examples:


*05da3a0cfe1929;
CRC: 000000
RSSI: -19.2 dBFS
Time: 224932633561.50us (phase: 0)
DF 0: Short Air-Air Surveillance.
  VS             : Ground
  CC             : 0
  SL             : 6
  Altitude       : 109200 feet
  ICAO Address   : 000000

*2cd5d1859b3761;
CRC: 000000
RSSI: -18.3 dBFS
Time: 224994292427.25us (phase: 180)
DF 5: Surveillance, Identity Reply.
  Flight Status  : ALERT & Special Position Identification. Airborne or Ground
  DR             : 26
  UM             : 46
  Squawk         : 4056
  ICAO Address   : 000000

*059a7485a4aacc;
CRC: 000000
RSSI: -19.2 dBFS
Time: 225169564748.67us (phase: 120)
DF 0: Short Air-Air Surveillance.
  VS             : Ground
  CC             : 0
  SL             : 4
  Altitude       : 70400 feet
  ICAO Address   : 000000

*2ed5d3b9d1bff5;
CRC: 000000
RSSI: -18.0 dBFS
Time: 225212410499.17us (phase: 120)
DF 5: Surveillance, Identity Reply.
  Flight Status  : Reserved
  DR             : 26
  UM             : 46
  Squawk         : 6355
  ICAO Address   : 000000

*2cd709e797ed1e;
CRC: 000000
RSSI: -10.7 dBFS
Time: 225216488553.08us (phase: 60)
DF 5: Surveillance, Identity Reply.
  Flight Status  : ALERT & Special Position Identification. Airborne or Ground
  DR             : 26
  UM             : 56
  Squawk         : 5546
  ICAO Address   : 000000

*2cd70f4c4a9f10;
CRC: 000000
RSSI: -19.8 dBFS
Time: 225237805729.75us (phase: 180)
DF 5: Surveillance, Identity Reply.
  Flight Status  : ALERT & Special Position Identification. Airborne or Ground
  DR             : 26
  UM             : 56
  Squawk         : 3262
  ICAO Address   : 000000




MSG,6,111,11111,000000,111111,2016/04/19,09:46:37.649,2016/04/19,09:46:37.703,,,,,,,,2662,-1,0,-1,
MSG,6,111,11111,000000,111111,2016/04/19,09:50:41.897,2016/04/19,09:50:41.942,,,,,,,,2203,0,0,0,
MSG,7,111,11111,000000,111111,2016/04/19,09:54:33.948,2016/04/19,09:54:33.992,,8450,,,,,,,,,,0
MSG,5,111,11111,000000,111111,2016/04/19,09:57:14.148,2016/04/19,09:57:14.179,,0,,,,,,,0,,0,-1
MSG,6,111,11111,000000,111111,2016/04/19,09:59:29.157,2016/04/19,09:59:29.184,,,,,,,,3325,0,0,0,
MSG,6,111,11111,000000,111111,2016/04/19,10:00:51.041,2016/04/19,10:00:51.095,,,,,,,,2056,0,0,0,
MSG,6,111,11111,000000,111111,2016/04/19,10:00:51.199,2016/04/19,10:00:51.258,,,,,,,,5602,0,0,0,
MSG,6,111,11111,000000,111111,2016/04/19,10:02:56.960,2016/04/19,10:02:56.993,,,,,,,,6436,0,0,0,
MSG,6,111,11111,000000,111111,2016/04/19,10:06:21.527,2016/04/19,10:06:21.574,,,,,,,,5513,0,0,0,
MSG,6,111,11111,000000,111111,2016/04/19,10:06:43.125,2016/04/19,10:06:43.149,,,,,,,,3726,0,0,0,
MSG,6,111,11111,000000,111111,2016/04/19,10:07:01.124,2016/04/19,10:07:01.165,,,,,,,,3666,0,0,0,
MSG,6,111,11111,000000,111111,2016/04/19,10:10:09.844,2016/04/19,10:10:09.902,,,,,,,,5602,0,0,0,
MSG,6,111,11111,000000,111111,2016/04/19,10:11:39.448,2016/04/19,10:11:39.479,,,,,,,,721,0,0,0,
MSG,6,111,11111,000000,111111,2016/04/19,10:14:47.783,2016/04/19,10:14:47.834,,,,,,,,2421,0,0,0,
MSG,5,111,11111,000000,111111,2016/04/19,10:15:40.566,2016/04/19,10:15:40.599,,123500,,,,,,,-1,,-1,
MSG,6,111,11111,000000,111111,2016/04/19,10:17:53.291,2016/04/19,10:17:53.320,,,,,,,,7105,0,0,0,
MSG,7,111,11111,000000,111111,2016/04/19,10:18:16.153,2016/04/19,10:18:16.191,,,,,,,,,,,,0
MSG,6,111,11111,000000,111111,2016/04/19,10:19:05.196,2016/04/19,10:19:05.238,,,,,,,,5701,-1,0,-1,
MSG,6,111,11111,000000,111111,2016/04/19,10:20:00.073,2016/04/19,10:20:00.119,,,,,,,,2421,0,0,0,
MSG,6,111,11111,000000,111111,2016/04/19,10:21:05.819,2016/04/19,10:21:05.870,,,,,,,,3262,-1,0,-1,
MSG,6,111,11111,000000,111111,2016/04/19,10:37:33.514,2016/04/19,10:38:18.729,,,,,,,,2313,0,0,0,
MSG,7,111,11111,000000,111111,2016/04/19,10:38:18.665,2016/04/19,10:38:18.729,,0,,,,,,,,,,-1
MSG,6,111,11111,000000,111111,2016/04/19,10:38:54.323,2016/04/19,10:38:54.345,,,,,,,,1003,-1,0,-1,
MSG,6,111,11111,000000,111111,2016/04/19,10:50:27.702,2016/04/19,10:50:57.802,,,,,,,,1613,0,0,0,
MSG,6,111,11111,000000,111111,2016/04/19,10:50:57.754,2016/04/19,10:50:57.802,,,,,,,,3344,0,0,0,
2

Those message types (DF 5 etc) don’t have good CRC protection; the ICAO address is not explicitly sent in the message data, it is xor-ed into the CRC bits.
To decode them and pair them up with an aircraft you calculate the CRC across the message data and xor that with the received CRC bits, which should recover the aircraft address since xor is its own inverse.

However, the aircraft address you end up with could also be the CRC of random noise, or a damaged address due to damage to the message data or CRC bits.

To filter out the garbage (and there is a lot of it) dump1090 only accepts messages which appear to have an address that has previously been heard in a more reliable format. Most commonly this is DF11 or DF17. Those message types carry the aircraft address in the message data and store the message data CRC directly in the CRC bits, so you can check they are valid messages just by looking at the CRC. Once you know what aircraft are in the area from those messages you can pick the real DF0/5/etc messages from those aircraft out of the random noise.

I would guess there is a (perhaps misconfigured) transponder that occasionally generates DF11/DF17 with an address of 000000; subsequently noise gets decoded as the messages you see. This could affect any address, but if there’s a misconfiguration or a transponder bug then 000000 is more likely than a random address, I suppose - it could be something like the transponder sending messages while it’s powering up before it’s loaded the address.

1 Like
3

Not for nothing I once saw a military flight of two v22s with the icao addresses of 000000 and 000001. Not sure if deliberate or malfunction.

There was a lot of wacky data coming from them - but based on what obj just said, it’s possible that receiving those addresses opened up the floodgates to all sorts of spurious data. The purest speculation, but something similar may be at play here.

4

Interesting, thanks for the details. I’ll keep logging and grepping for 000000 to see if I get any DF11/DF17 or other message types.