Tracking the Localizer Outbound

[Mark Hargrove]

So I'm practicing for I6, the full ILS RWY 19R approach from LAX to SNA. I'd flown it a couple of times already with no problems, allowing the autopilot to fly the approach (including the course-reversal) coupled to the GPS.

On my third try, getting a little bored, I decide that my GPS has suffered a failure while inbound from SLI to SAGER and I'll need to use different navaids to help me complete the approach. I switch to tracking the SLI 049 radial outbound from the VOR and set up the KSNA localizer on VOR2 (and also set ISNA as the standby frequency on NAV1). I know that when I cross the localizer I'll be at SAGER (and to double check, I ought to be 17.3 DME from KSNA). I'll turn left to 014 degrees at SAGER, punch NAV1 onto the localizer, and track it outbound on VOR1 for 1 minute while descending to 3500'. After a minutes passes, I'll make the teardrop left turn to re-intercept the localizer and all will be good -- at that point it's a normal ILS approach and the GPS failure wasn't a big deal.

I'm patting myself on the back for being such a clever lad, then as I make the left turn to 014 outbound from SAGER I realize I have no freaking idea how to fly a localizer course in reverse. I'd dialed in 014 as my course, but THAT didn't seem to be working. After wandering left and right like a drunken sailor for about 45 seconds, I just settled on flying a 014 HEADING, made the left teardrop turn and intercepted the localizer. From then on I was fine, but I felt really stupid for forgetting that a localizer wasn't a VOR. I realize that I could have just turned left at SAGER and flown a 014 heading, but that would only work if there was no wind.

What is the correct way to track a localizer in the "wrong" direction?

[steve.huff]

When your flying the back course for a localizer, the CDI will have reverse sensing. Some airports use the Back course as another non-precision approach.
During my instrument training I was lucky enough to have one of these. What works for me is on the front course. Visualize that the center part of the CDI that is deflected is the course I want to be on.
On a Back course, the center part of the CDI that is deflected, is my aircraft and I need to fly to towards the needle head. There are also receivers that have a back course mode, that will adjust the reverse sensing to make it normal sensing.
Steve

[Orest Skrypuch]

Yes, on the back course (whether tracking outbound on a LOC or inbound on a LOC BACK CRS), you are the needle. HSI's of course make this much easier, you just dial in the front course, and it works the same in both directions.

But be careful, newer solid state localizers do not have a back course, they are a front course both ways, and only active in one direction at a time, and with different IDs. You could have a "front" course to both opposing runways. This will be obvious from the indications on the plate - presence/absence LOC (BACK CRS) in the title and usually a BACK COURSE notation in the plan view, and the LOC feather shaded/white orientation.

* Orest

[Keith Smith]

A common way to remember it is to fly towards the needle on the front course, and away from the needle on the back course (or outbound on the front course in this case).

[Mark Hargrove]

Thanks guys!

Does the 'BC' button on the autopilot tell the AP to reverse it's normal sensing of the localizer?

-M.

[Keith Smith]

Yes indeed