Decoded 2-bit Surveillance Status (SS) subfield of an ADS-B airborne
position message (type codes 0, 9-18, and 20-22), per RTCA DO-260B: the one
condition, if any, the transponder is flagging alongside the position.
The field holds a single value and an alert outranks an ident, so
permanentAlert and temporaryAlert say nothing about whether an ident
is active at the same time.
none - no alert and no ident.
permanentAlert - an emergency condition (squawk 7500, 7600, or 7700).
temporaryAlert - the squawk was recently changed to a code other than
an emergency one; the transponder holds this for about 18 seconds.
ident - the SPI (Special Position Identification) condition: the
pilot has pressed Ident.
Decoded 2-bit Surveillance Status (SS) subfield of an ADS-B airborne position message (type codes 0, 9-18, and 20-22), per RTCA DO-260B: the one condition, if any, the transponder is flagging alongside the position. The field holds a single value and an alert outranks an ident, so
permanentAlertandtemporaryAlertsay nothing about whether an ident is active at the same time.none- no alert and no ident.permanentAlert- an emergency condition (squawk 7500, 7600, or 7700).temporaryAlert- the squawk was recently changed to a code other than an emergency one; the transponder holds this for about 18 seconds.ident- the SPI (Special Position Identification) condition: the pilot has pressed Ident.