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7 Answers

G1000 Intercept Maximum Range

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Aircraft Systems

Using a G1000 in Autopilot, what is the maximum distance that I can be either from a VOR radial or an active GPS leg before NAV mode will navigate to and intercept the radial or leg?

So, say I have a VOR radial in the CDI and CDI is set to VOR but I am pretty far from and off the radial. What I would normally do is use Heading mode to get me closer to and at a good intercept angle with the radial. Once I am close (needle starts moving), I will switch to NAV move and have the Autopilot intercept and fly the radial. The question is, how far can I be (max distance) from the radial before the autopilot will steer the plane to intercept the radial. Is it the same for a VOR radial as an active leg GPS?

Thx!!

 

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7 Answers



  1. John D Collins on Sep 15, 2022

    From the G1000 pilot guide:

    The selected navigation receiver must have a valid VOR or LOC signal or active GPS
    course before NAV or APR Key press activates flight director

    So this is not a specific distance and for VOR depends on receiving a valid VOR or LOC signal. Although there are standard service volumes for VOR and LOC in which one can expect to reliably receive these signals, other factors such as altitude, line of sight, angular position, and receiver sensitivity will determine the maximum distances these signals can be received. See the AIM sections 1-1-8 and 1-1-9 for VOR and LOC service volume definitions respectively.

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  2. Andre Venter on Sep 15, 2022

    Thanks John,

    That makes sense. I failed to say \”assuming the VOR is identified and the identifier is showing\”. My primary training CFI happened to show up at my office today, and the first thing he pulled out on his phone was service volumes. He did say, use HDG until you are reasonably close and then switch to NAV for intercept.

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  3. Russ Roslewski on Sep 16, 2022

    What autopilot do you have? (I don’t claim to know the whole history, but while the GFC700 is now “standard” with the G1000, didn’t earlier 172’s, and maybe others, come with a King autopilot?)

    If it’s the GFC700, then there’s no reason to be in HDG and then “wait” to engage NAV, you should have them both engaged and it will stay in HDG with NAV armed until it intercepts the course and NAV goes active. That would be the more ideal way to fly this. The same method is also used for vectors-to-final on an approach, with HDG active and APPR armed.

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  4. Mark Kolber on Sep 18, 2022

    @Russ. Yes. The early G1000s had a KAP 140. Both Cessna and Diamond (an probably a few others) had that configuration.

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  5. Andre Venter on Sep 19, 2022

    Thanks Russ, it is a GFC700.

    I’m not exactly sure how to have both HDG and NAV engaged at the same time. I believe those 2 modes show up in the same spot, unless memory fails me right now and they show up side by side, white and green. It would be great to fly in HDG and have NAV automatically intercept the radial when it is close enough to do so. Would it be possible for you to expand on the execution of this, please?

    Thanks !!

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  6. KSands on Dec 09, 2022

    It would have to be within the appropriate range of the VOR being used, so the stated service volumes for Terminal , Low, and High , VORs needs to be accounted for.

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  7. John D Collins on Dec 09, 2022

    Service volumes should be accounted for, but the service volume really only applies to a random radial not on an airway or procedure for a VOR and is a “use” limitation imposed on the pilot, not the auto pilot. The G1000 is not going to know the service volume, it will be determined by the actual signal levels available at the time. There are also new service volumes defined that will apply to new classes of VOR, VL and VH, and these are often highly stratified. See this for the MQP VORTAC which includes the VH service volume, which supposedly provides a 70 NM SSV for VOR for 5000 feet above, but it has the following limitations as published in the Chart Supplement (I don’t think a pilot is going to know this stuff or where to find it.):

    MILLSAP (VH) (H) VORTACW 117.7 MQP Chan 124

    VOR unusable:

    004º–009º byd 40 NM 010º–054º byd 40 NM blo 3,800´ 010º–054º byd 46 NM blo 5,000´ 010º–054º byd 56 NM 055º–066º byd 40 NM blo 3,800´ 055º–066º byd 50 NM 230º–247º byd 40 NM 248º–258º byd 40 NM blo 3,700´ 248º–258º byd 53 NM 259º–270º byd 40 NM blo 6,000´ 259º–270º byd 63 NM 271º–285º byd 40 NM 312º–316º byd 40 NM 325º–340º byd 40 NM blo 3,000´ 325º–340º byd 46 NM blo 5,000´ 325º–340º byd 66 NM 353º–003º byd 40 NM blo 18,000´

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