We have analysed the raw data from the transponder of #4U9525 and found some more data apart from the regular position/altitude data.These are the decoded ModeS (Downlink Format 20) frames which contain replies to interrogating radar requests (Upling Format 20).
09:30:48Z.651 MCP/FMC ALT: 38000 ft QNH: 1006.0 hPa09:30:48Z.936 T,3c6618,43.115341,5.671181,38000,GWI18G09:30:49Z.496 T,3c6618,43.116028,5.671692,38000,GWI18G09:30:50Z.076 T,3c6618,43.117381,5.673065,38000,GWI18G09:30:50Z.111 MCP/FMC ALT: 38000 ft QNH: 1006.0 hPa09:30:50Z.553 MCP/FMC ALT: 38000 ft QNH: 1006.0 hPa09:30:50Z.619 MCP/FMC ALT: 38000 ft QNH: 1006.0 hPa09:30:50Z.626 T,3c6618,43.118408,5.673736,38000,GWI18G09:30:51Z.127 T,3c6618,43.119095,5.674247,38000,GWI18G09:30:51Z.636 T,3c6618,43.120453,5.675092,38000,GWI18G09:30:52Z.386 MCP/FMC ALT: 38000 ft QNH: 1006.0 hPa09:30:52Z.567 T,3c6618,43.122208,5.676482,38000,GWI18G09:30:53Z.036 T,3c6618,43.122894,5.676993,38000,GWI18G09:30:53Z.546 T,3c6618,43.124271,5.678166,38000,GWI18G09:30:54Z.083 MCP/FMC ALT: 13008 ft QNH: 1006.0 hPa09:30:54Z.096 T,3c6618,43.125295,5.678689,38000,GWI18G09:30:54Z.676 T,3c6618,43.125961,5.679421,38000,GWI18G09:30:55Z.156 T,3c6618,43.127157,5.680259,38000,GWI18G09:30:55Z.397 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:30:55Z.453 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:30:55Z.636 T,3c6618,43.128367,5.681109,38025,GWI18G09:30:56Z.186 T,3c6618,43.129211,5.681656,38025,GWI18G09:30:56Z.707 T,3c6618,43.129898,5.682167,38000,GWI18G09:30:57Z.267 T,3c6618,43.131626,5.683201,38000,GWI18G09:30:57Z.312 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:30:57Z.836 T,3c6618,43.132507,5.684020,38000,GWI18G09:30:58Z.050 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:30:58Z.296 T,3c6618,43.133011,5.684403,38000,GWI18G09:30:58Z.767 T,3c6618,43.134559,5.685425,38000,GWI18G09:30:59Z.216 T,3c6618,43.135397,5.685948,38000,GWI18G09:30:59Z.746 T,3c6618,43.136261,5.686575,38000,GWI18G09:30:59Z.988 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:31:00Z.146 T,3c6618,43.137451,5.687149,38000,GWI18G09:31:00Z.165 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:31:00Z.676 T,3c6618,43.137817,5.687660,38000,GWI18G09:31:01Z.676 T,3c6618,43.139866,5.689022,38000,GWI18G09:31:02Z.027 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:31:02Z.238 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:31:02Z.496 T,3c6618,43.141402,5.690199,38000,GWI18G09:31:03Z.030 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:31:03Z.456 T,3c6618,43.143494,5.691429,38000,GWI18G09:31:04Z.376 T,3c6618,43.145731,5.692945,37975,GWI18G09:31:04Z.943 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:31:05Z.346 T,3c6618,43.147430,5.693984,37975,GWI18G09:31:05Z.558 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:31:05Z.993 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:31:06Z.466 T,3c6618,43.149828,5.695365,37975,GWI18G09:31:07Z.164 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:31:07Z.346 T,3c6618,43.151367,5.696539,37950,GWI18G09:31:08Z.256 T,3c6618,43.153427,5.697752,37950,GWI18G09:31:08Z.776 T,3c6618,43.154111,5.698308,37925,GWI18G09:31:09Z.276 T,3c6618,43.154995,5.698962,37925,GWI18G09:31:09Z.712 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:31:09Z.960 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:31:10Z.326 T,3c6618,43.157364,5.700307,37925,GWI18G09:31:11Z.312 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:31:11Z.467 T,3c6618,43.159607,5.701713,37900,GWI18G09:31:11Z.876 T,3c6618,43.160660,5.702415,37900,GWI18G09:31:12Z.102 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:31:12Z.386 T,3c6618,43.161512,5.702885,37875,GWI18G09:31:12Z.846 T,3c6618,43.162211,5.703408,37875,GWI18G09:31:13Z.316 T,3c6618,43.163049,5.704128,37875,GWI18G09:31:13Z.896 T,3c6618,43.164597,5.704970,37875,GWI18G09:31:14Z.401 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:31:14Z.493 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:31:15Z.536 T,3c6618,43.168030,5.707201,37825,GWI18G09:31:16Z.416 T,3c6618,43.169380,5.707921,37825,GWI18G09:31:17Z.028 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:31:17Z.266 T,3c6618,43.171288,5.709294,37800,GWI18G09:31:18Z.196 T,3c6618,43.173019,5.710144,37775,GWI18G09:31:19Z.166 T,3c6618,43.175385,5.711648,37750,GWI18G09:31:19Z.262 MCP/FMC ALT: 96 ft QNH: 1006.0 hPa09:31:20Z.176 T,3c6618,43.177277,5.712891,37725,GWI18G09:31:21Z.216 T,3c6618,43.179202,5.714068,37700,GWI18G
Between 09:30:52 and 09:30:55 we can see that the autopilot was manually changed from 38,000 feet to 100 feet and 9 seconds later the aircraft started to descend, probably with the "open descent" autopilot setting.The reason why the selected altitude is 96ft is that least significant bit for altitude setting equals 16 ft, and we suspect that you can’t set autopilot to 0000 altitude, so the minimum would be 100ft down rounded to 96ft in binary representation in BDS40h register.Any comments or thoughts about this?
Playback: http://www.flightradar24.com/data/fl...u9525/#5d42675
This data has also been handled over to BEA 2 days ago.