CDU Steer Modes

[MayKii]

Hello everybody,

 

There are four different steer modes such that to-from, to-to, direct and scs in cdu. I only understood direct mode but have confused about the differences of to-from and to-to steer modes. I watched related videos on youtube and read manual but they have not clarified the differences of this two modes in my mind.

 

Could you please explain what are these two modes ? I'm creating flight plan in CDU but don't know which modes should be used for which waypoints.

 

Thank you

[kontiuka]

In a nutshell ...

 

To-To keeps you on course between 2 waypoints. For example, if waypoint 2 is east of waypoint 1, the To-To mode will steer you onto the 90 degree radial. Changing the course on the HSI has no effect on the course deviation indicator when you're in this mode. You can also specify your 'from' waypoint in the WAYPOINT page of the CDU so you can, for example, fly to waypoint 2 from waypoint 4 instead or from the bullseye, etc.

 

To-From allows you to specify the radial that you'll approach a waypoint from. So, for example, if you wanted to approach a target at mark point A from the north, you'd go into To-From mode and enter a course of 180 on the HSI to place the target south of you.

 

So, to sum up, in To-To, you're locked into a course line. In To-From, you're free to choose you're course line.

 

Here's a pretty good tutorial link:

 

[MayKii]

Hi kontiuka,

 

Your explanation clarified everything for me now. Thank you very much.