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8 Answers

IFR Departure

Asked by: 1937 views Airspace, FAA Regulations

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Reference WAGGE TWO Departure (KRNO):

The use of the localizer (I-RNO  110.9) for 34L is used to fly outbound on 16R departure and is listed as “back course” on the DP. Yet 34L localizer is a front course approach---there is no published back course approach. The localizer symbol is also shaded as back course on the DP which contradicts the 34L approach front course shading.

Assume an aircraft is equipped with a standard VOR/ILS receiver (no HSI):

As you know using a standard VOR/ILS receiver (no HSI)  when you fly outbound on a back course you have correct sensing. But in this DP case this is not correct because you are flying outbound on the 34L localizer front course and have reverse sensing. My concern is that if you are not paying attention one could fly outbound on this DP and misinterpret the VOR/ILS receiver needle deflections because of the “back course” language.

In summary, why would TERPS use the term back course when the front course 34L localizer is utilized?

Any feedback appreciated.

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8 Answers

  1. Rusty Allen on Dec 05, 2013

    Simple, You are departing in the opposite direction to standard ILS for 34L. Thus, the ILS indentations will be those of a BACK coarse. Of note is that the ILS sensitive will decrease as you depart rather increase. (I am not a CFI but have spent several hours sitting in a plane with one 😉 )

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  2. Rusty Allen on Dec 05, 2013

    As a second go at the subject, the LOC component of the ILS system provides center line guidance. The LOC radios signals in truth define an “A” and “B” sides divided by the runway center line (arc 340-120 is “A”, Arc 120-340 “B”) The LOC does not provide direction of travel down the center for the aircraft. It is merely convention that make the “A” left of center line and “B” right when flying a “front” of the LOC. All is good when flying a heading 340 for the 34L LOC but on a heading of 120 you get the “BC” indentations. The “A” and “B” sides of the LOC physically remain the same but where you are in relationship to the center line has change when you are on the “A” side. Left and Right is a mater of where you are facing. A heading of 120 for LOC 34L is a “backward” facing to the LOC and thus the reversal of left and right.

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  3. John D Collins on Dec 05, 2013


    Check out the frequency and the Ident. The back course on WAGGE Two is associated with the ILS 16R, 110.9 I-RNO localizer path 162 degrees. Since it is on the localizer path south of the runway, it is called the back course. Flying the front or back course in the direction of the front course (162 degrees), is correct sensing, conversely flying the front course or the back course in the direction opposite of the front course (342 degrees), sensing is reversed.

    The terminology front course or back course is with respect to the location of the localizer antenna which is located 500 to 1000 feet off the departure end of the runway. On the runway side of the antenna, it is called the front course. On the side away from the runway is called the back course. Regardless, anytime you are in the shaded side of the localizer depiction, you will have a fly left on the CDI, so if your general direction is aligned with 162 degrees, you have correct sensing on either the front or back course.

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  4. Dan Chitty on Dec 05, 2013


    I see now. I completely overlooked the details you mention. Lesson learned.

    So all localizer antenna signals transmit in both directions even if there is no published back course approach. Is this Correct?

    Thank you for the help.

    Thank you Rusty also for the input.

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  5. Wes Beard on Dec 05, 2013

    All localizer antennas have the ability to transmit in each direction. Some localizers installations block the back course signal. Reference KPHX ILS 7R and ILS 25L. Both procedures land on the same runway on opposite ends. Both localizer frequencies are 110.75 and both are front course signals.

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  6. Dan Chitty on Dec 05, 2013


    Thank you as well for this detail. Much appreciated.

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  7. John D Collins on Dec 06, 2013


    The back course signals are not blocked. The same frequency is used for the KPHX ILS 7R and 25L, but each has its own localizer antenna, GS antennas, and equipment. Only one of the two systems is active at a time and controlled by a switch in the tower, so they reuse the frequency. Each has its own unique Ident code, so here is a case where the switch might be in the wrong position, but the pilot should detect it if they verify the ID code,

    The back course can be used on a missed approach or on departure for guidance. Whether it is used or not, it is there.

    At Aspen, see the LOC/DME-E approach. A separate back course that is not part of the airport is used as part of the missed approach procedure where the localizer is on a mountain south of the airport and oriented so that its back course guides the aircraft away from the mountains. You intercept the back course and track it outbound and of course, the sensing is normal and does not require reverse sensing. If you have an HSI, you align it with the arrow in the front course direction which is the same as the back course in the outbound direction.

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  8. Wes Beard on Dec 06, 2013


    You’re right. I forgot that piece of information. A good reason to ident and also to learn how to determine what the expected deflection should be on the VOR or HSI for your location in relation to the station.


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