Under what condition will the Flight Management System (FMS) not autotune?

The Flight Management System (FMS) will not autotune primarily when the system indicates green needles on the display. Green needles signify that the system is actively engaged in navigation but may not be set to autopilot or may require manual input for navigation corrections. In this state, the FMS relies on preselected waypoints or flight paths that the crew has independently verified, and therefore, it does not automatically update or autotune to different frequencies or navigation sources.

This scenario contrasts with other conditions presented. For instance, in standby mode, the system is not operational, while in manual mode, the crew might be handling navigation inputs directly, but these do not preclude autotuning per se. During engine startup, the system may not be fully operational but could still engage in certain autotuning processes once initialized. Thus, the presence of green needles is the most definitive condition indicating that autotuning will not occur.