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OBS setting on VOR approaches

Asked by: 1607 views Instrument Rating

When flying outbound on a VOR approach, is it better to set the outbound course into the OBS and then switch it to the inbound course during the procedure turn? Or is it better to set the inbound course and fly the outbound course with reverse sensing? I can’t find anything in the Instrument Procedures Handbook that says how this should be done. Ive always flown it by setting the inbound course and then flying outbound with reverse sensing, but I’m not sure what the proper method is. 

3 Answers



  1. Bryan on May 24, 2022

    The Instrument Flying Handbook doesn’t say much about reverse sensing…but it says enough.

    “If the VOR is set to the reciprocal of the intended course, the CDI reflects reverse sensing. To correct for needle deflection, turn away from the needle. To avoid this reverse sensing situation, set the VOR to agree with the intended course.”

    Later, under VOR Operational Errors, the 4th error is “Failure to check the ambiguity (TO/FROM) indicator, particularly during course reversals, resulting in reverse sensing and corrections in the wrong direction.”

    The FAA does not want you flying using reverse sensing unless it’s part of an ILS procedure because there is too much chance to correct the wrong direction.

    Take the VOR RWY 3 at Pocatello Regional (PIH) for example. The profile view wants you to fly outbound on the 235 radial on heading 235, then do a procedure turn to the right, heading 280, back to the 235 radial via heading 100, then inbound on the 235 radial on heading 055, before turning over the VOR to the final approach course of 033.

    ATC would clear you direct to the VOR to begin this approach. Once there, your OBS goes to 235 with a FROM flag, which will match the heading bug. Staying within 10 miles, you will turn to 280 using only the heading bug, fly out for a minute, then fly back in on 100 again using the heading bug. During that turn, you will reset your OBS to 055 and make sure it has a TO flag. You fly heading 100 on the heading bug until the needle comes in and then you fly the needle on heading 055 to the station. Once you get into the cone of confusion, you fly 033 using the heading bug and adjust the OBS again to 033 and you will make sure you are back to the FROM flag–then once the needle is behaving, intercept it and RWY3 awaits less than 3 NM away. Notice that the OBS matches the heading bug all three times we’re flying radials off of the VOR.

    Flying with reverse sensing should be considered an error unless a procedure (usually ILS) calls for it and the aircraft is capable of it (see page 9-40 in the Instrument Flying Handbook). Notice it doesn’t say the pilot is capable of it–the aircraft has to be capable of reverse sensing. We learn about it as pilots so that we can detect it and correct it when we set it up wrong–not so that we can fly that way.

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  2. Russ Roslewski on May 26, 2022

    I have a hard time understanding why you would voluntarily want to use reverse-sensing when you don\’t have to. Especially in a high-workload phase of flight, you could easily forget it was reverse, and turn the wrong way.

    To save yourself a couple of seconds of twisting? Sounds like a bad idea all around.

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  3. Mark Kolber on May 27, 2022

    Russ, that goes double for me!

    Sorry.

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