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6 Answers

Back Course Localizer

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Instrument Rating

Is horizontal navigation information available on the back side of all the localizers or is that information only available for those localizers that have a published back course approach?

Thanks

 

 

6 Answers



  1. Russ Roslewski on Jun 21, 2017

    You are only guaranteed usable back course navigational guidance when it is published. That means it has been flight inspected and determined to be usable. When a back course is NOT published, it still may or may not exist, and may or may not provide a good signal for guidance, but you won’t know that.

    But the big question might be, WHY would you want to follow a back course signal that isn’t published? I have done this for training, but other than that can’t think of a useful case for doing this.

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  2. Charles22 on Jun 21, 2017

    Russ,

    Thanks for your reply.

    I do not intend to follow a back course signal that is not published. On a simulator I have seen that the red flag appears on the HSI, when the airplane is on the back side of the localizer for which there is no published BC approach. I just wanted to know how the system works. Based on your reply, I understand that there may or may not be a signal. I totally agree that, even if the signal is there, it shall not be used.

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  3. Russ Roslewski on Jun 21, 2017

    Okay, I see. That red flag is just an artifact of the simulation, and is not how it would really behave. More detail: Electromagnetically, every localizer has a back course – there is some signal being radiated in that direction on every localizer antenna out there. However, due to objects in the way and reflections from buildings, vehicles, and even the ground, it may or may not provide any useful signal in that direction. Even if not published, sometimes this back course works just fine, and I’ve used the back course of a local Localizer for training this way many times.

    Finding published back course approaches, on the other hand, is getting difficult as there just aren’t that many of them around anymore. I see 34 LOC BC and 34 LOC/DME BC approaches in the U.S. inventory (https://www.faa.gov/air_traffic/flight_info/aeronav/procedures/ifp_inventory_summary/) – I think those numbers are just coincidentally identical. They are going away for what I think are obvious reasons – tricky to fly, and can usually be replaced with an LPV with better minimums. In fact, there are none at all within my home state of Oklahoma.

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  4. Charles22 on Jun 21, 2017

    Thanks for the additional information, Russ!

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  5. Max on Jun 23, 2017

    Every localizer installation I’ve seen has about 8 to 12 yagi antennas at the far end of the runway configured as a phased array. The strongest signal will be down the runway for the localizer, with very little signal coming off the sides of the antenna. However the second strongest signal will be the back course. Due to the nature of these antennas, it would be hard to attenuate a back course signal, so you should expect to find one on most any localizer. But as Russ said, there is Zero guarantee as to the quality of that signal.

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  6. Charles22 on Jun 23, 2017

    Noted. Thanks, Max.

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