Descent Forecast
The descent forecast page is used to enter wind data for descent, and the altitude at which anti-ice use is anticipated for more accurate descent path calculation.
The primary entries are wind direction and speed for up to four descent altitudes, and the altitude that anti-ice is turned on.
TRANS LVL - Shows the transition level. The transition level can be specified by the arrival procedure. The default transition level is FL 180. Above transition level, altitudes are in flight levels. Below transition level, altitudes are in thousands of feet. Valid entry is an altitude or flight level.
ALT - Enter altitude of forecast wind data. Altitudes and flight levels can be entered in any order. Entries are not sorted. Execute not necessary.
TAI/ON ALT - Enter the altitude where anti-ice is first turned on during the descent. The FMC calculates the descent profile based on the higher thrust caused by thermal anti-ice operation below this altitude.
WIND DIR/SPD - Enter the wind direction/speed for the specified altitude. Initial entry must have wind direction and speed, subsequent entries may have one or the other. Execute not necessary.
DES - Shows the DES page.