Originally Posted by urfix: FMS SEL ALT 0 ft was set, a few seconds before the impact FMS SEL ALT 8000 ft was selected.
Originally Posted by Central Scrutinizer
Just curious: how do you know that?
Mode S Enhanced Surveillance (EHS) extended squitter transponders, with
ADS-B out can broadcast some Downlink Aircraft Parameters (DAP), some of these parameters may be displayed on
globe.adsbexchange.com, such as :
a. Magnetic Heading
b. Indicated Airspeed and/or Mach No.
c. Vertical Rate (climb/descend)
d. MCP/FCU Selected Altitude
e. Ground Speed
f. Roll Angle
g. Track Angle Rate (or True Airspeed if Track Angle Rate is not available)
h. True Track Angle
i. Barometric Pressure Setting
(MCP - Mode Control Panel / FCU - Flight Control Unit / FGP - Flight Guidance Panel in this case with Pro Line 21 avionics)
The requirements of EHS are fulfilled by data provided in the Extended Squitter message from a Mode S transponder. The format to provide the data that is defined in the RTCA documents that are used to certify ADS-B transponders. (RTCA - Radio Technical Commission for Aeronautics).
RTCA DO-260B references DO-181E and EUROCAE ED-73C for those message formats and specific bits.
FAA AC 20-165B specifies
ADS-B out requirements for certification.
EHS requires an interrogation from the ground for specific data (DAPs) and the reply format is carried in the Comm-B. The requested data from the interrogators is different in Europe and the Americas. Interrogators in the U.S. request less DAPs, therefore the same aircraft might display less or more parameters depending upon where it is flying.
FMI:
https://nbaa.org/aircraft-operations...-transponders/
https://mode-s.org/decode/