I'm reading about it in the manual but I'm not getting a sense of when it is supposed to be most useful. In other words, could somebody write up a scenario or two in which you describe when you enable Flight Director mode and why? Or is there a video out there that shows it being used? Thanks.

The flight director provides the pilot with computed lateral and vertical steering commands to fly the helicopter along a desired lateral and vertical flight path. It directs the pilot in satisfying the flight parameters needed to get from point A to point B to point C etc etc in accordance with the set flight plan. In other words, rather than relying on the Autopilot to aid you in reaching your destination at a given heading, attitude and/or altitude, you are 'directed' by means of visual cues in the HUD in order to stay within your flight plan parameters.

Without the Flight Director, the AP will keep you on your heading, attitude and altitude automatically. With Flight Director you as Pilot are 'directed' to do it yourself by flying the Helo as indicated in the HUD, ie by obeying the 'instructions' of the altitude, pitch-bank and other director cues.

As for practical implementation - Training tool is one. Would also depend on the mission flown I would suppose: The free-flight scenario would be better suited for FD for some as it neutralises the AP influence whilst maintaining the SAS. For structured missions with fixed flight plans one might favour FD off for reliance on the AP assists, thus alleviating pilot workload.

You can learn to fly the heli with FD ON. Since we don't have a training heli in the game, this is the best approximation.

Actual cases where FD might be needed would likely have to do with equipment malfunctions where the AP cannot use all channels for example, whether because its servos are broken or because the sensor information coming into the AP is faulty.