When Reverse Sensing Already Is

Many pilots struggle to properly use an HSI when flying a localizer. If youre inbound to a VOR on a given course, pass the station and proceed outbound, you dont change the OBS, right? Likewise, when outbound on a localizer, dont change the OBS, HSI or not. So, similarly, if youre flying the front course-inbound or past the runway-you select the front course by convention for situational awareness, even though a localizer doesnt care where the OBS is.

Frank Bowlin

Thursday, June 25, 2015 at 12:00 AM ET

Verified

Key Takeaways:

For localizer front courses, set the HSI or OBS to the front course for situational awareness, irrespective of direction.
When flying a localizer back course, always set the indicator's course selector (OBS or HSI) to the *front course* of the runway.
On a back course, a conventional VOR/LOC indicator requires correcting by turning *away* from the deviation needle, whereas an HSI automatically provides reverse sensing, allowing pilots to steer *towards* the depicted CDI.
Regardless of the indicator type (conventional or HSI), autopilots must be engaged in a "back course" mode for proper reverse sensing on a back course approach.

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Many pilots struggle to properly use an HSI when flying a localizer. If you’re inbound to a VOR on a given course, pass the station and proceed outbound, you don’t change the OBS, right? Likewise, when outbound on a localizer, don’t change the OBS, HSI or not. So, similarly, if you’re flying the front course—inbound or past the runway—you select the front course by convention for situational awareness, even though a localizer doesn’t care where the OBS is.