This parameter is displayed on some aircraft, notably French (Mirage 2000 & Rafale) which display the longitudinal acceleration (labelled Jx) in the headup disp

This parameter is displayed on some aircraft, notably French (Mirage 2000 & Rafale) which display the longitudinal acceleration (labelled Jx) in the headup display. Part of the takeoff procedure for the pilot is to confirm the Jx is nominal with regards to the takeoff parameters (loadout, density altitude, etc.).