Copyright D.P. Browne 2011

The Flight Path Vector (FPV) defines the aircraft’s horizontal and vertical track with  respect to the earth, taking the current wind state into consideration.

The FMGS modes of TRACK and FPA guide the aircraft onto the FCU targets of Track heading and Flight  path angle.

Gamma .

Is the flight path angle

Drift

Is the drift angle between the aircraft’s heading and track angle

F/D Gamma Cmd

Is the difference between the aircraft’s flight path angle and the target FCU FPA value

F/D Phi Cmd

Is the difference between the required roll angle and actual roll angle to meet the track selected on the FCU

This FPV symbol appears on the PFD when the TRK/FPA button is pressed on the FCU, and the FPA mode then engages.

The FPV  represents the  aircraft’s horizontal and vertical track with  respect to the earth

The lateral scale is used to represent the aircraft's track and the vertical scale is used to represent the aircrafts flight path angle, Gamma)

Flight Path Vector (FPV)

The F/D bars change from the two cross hairs to a single Flight Path Director bar. Is Vertical displacement from the FPV symbol represents the command required to archive the FPA  target value in the FCU and the roll angle of the FPD bar represents the command to archive the required roll command.