2.5. Heading and speed (BDS 6,0)

Within the BDS 6,0 message, five different types of aircraft states are given:

  • magnetic heading
  • indicated airspeed
  • Mach number
  • barometric altitude rate
  • inertial vertical rate

The 56-bit MB field is structured as follows:

+---------------------------------------+------+------+
| FIELD                                 | MB   |N-BITS|
+=======================================+======+======+
| Status                                |  1   |  1   |
+---------------------------------------+------+------+
| Sign, 1 -> West                       |  1   |  1   |
+---------------------------------------+------+------+
| Magnetic heading                      |  3   |  10  |
|                                       |      |      |
| range = [-180, 180] degrees           |      |      |
|                                       |      |      |
| LSB: 90/512 degree                    |  12  |      |
+---------------------------------------+------+------+
| Status                                |  13  |  1   |
+---------------------------------------+------+------+
| Indicated airspeed                    |  14  |  10  |
|                                       |      |      |
| range = [0, 1023] knots               |      |      |
|                                       |      |      |
| LSB: 1 knots                          |  23  |      |
+---------------------------------------+------+------+
| Status                                |  24  |  1   |
+---------------------------------------+------+------+
| Mach number                           |  25  |  10  |
|                                       |      |      |
| range = [0, 4.092] Mach               |      |      |
|                                       |      |      |
| LSB: 2.048 / 512 Mach                 |  34  |      |
+---------------------------------------+------+------+
| Status                                |  35  |  1   |
+---------------------------------------+------+------+
| SIGN 1 -> Below                       |  36  |  1   |
+---------------------------------------+------+------+
| Barometric altitude rate              |  37  |  9   |
|                                       |      |      |
| range = [-16384, 16352] ft/min        |      |      |
|                                       |      |      |
| LSB: 32 ft/min                        |  45  |      |
+---------------------------------------+------+------+
| Status                                |  46  |  1   |
+---------------------------------------+------+------+
| SIGN 1 -> Below                       |  47  |  1   |
+---------------------------------------+------+------+
| Inertial altitude rate                |  48  |  9   |
|                                       |      |      |
| range = [-16384, 16352] ft/min        |      |      |
|                                       |      |      |
| LSB: 32 ft/min                        |  56  |      |
+---------------------------------------+------+------+

An example:

MSG:  A000029CFFBAA11E2004727281F1
MB:           FFBAA11E200472

---------------------------------------------------------------------------------
MB BIN:   1 1 1111111011 1 0101010000 1 0001111000 1 0 000000000 1 0 001110010
---------------------------------------------------------------------------------
STATUS:   1
SIGN:       -
HEADING:      1019 (x90/512)
---------------------------------------------------------------------------------
STATUS:                  1
IAS:                       336
---------------------------------------------------------------------------------
STATUS:                               1
MACH:                                   120 (x2.048/512)
---------------------------------------------------------------------------------
STATUS:                                             1
SIGN:                                                +
VERTIVAL RATE - BARO:                                  0 (x32)
---------------------------------------------------------------------------------
STATUS:                                                         1
SIGN:                                                             -
VERTICAL RATE - INERTIAL:                                           114 (x32)
---------------------------------------------------------------------------------
FINAL:      -179.1 deg     336 kt      0.48 Mach     0 ft/min     -3648 ft/min
---------------------------------------------------------------------------------