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ILS CAT I with Autopilot, RVR reduced to 1800 feet

Asked by: 3365 views General Aviation

AIM 1-1-9 (p.551) states:

(a) Category I. Decision Height (DH) 200 feet and Runway Visual Range(RVR) 2,400 feet (with touchdown zone and centerline lighting, RVR 1,800 feet), or (with Autopilot or FD or HUD, RVR 1,800 feet);

My question is: what exactly is meant by "Autopilot" here? I mean, how should it be used to bring the RVR down to 1,800 feet. As far as I know, Autopilot is always used for instrument approaches at least to some extent, for example, to intercept the localizer or to control thrust. Does it mean that the autopilot system should be used to the full extent throught the approach?

3 Answers

  1. Best Answer


    Russ Roslewski on Feb 05, 2017

    The full note on an approach chart says “RVR 1800 authorized with use of AP or FD or HUD to DA”.

    See KTPA ILS OR LOC RWY 19R for an example:
    https://skyvector.com/files/tpp/1702/pdf/00416IL19R.PDF

    So if you’re using the autopilot to meet that requirement, it must stay on until DA.

    I am curious as to what type of airplane you are flying for training, based on your comment that “As far as I know, Autopilot is always used for instrument approaches at least to some extent, for example, to intercept the localizer or to control thrust. ”

    Many, many airplanes used for instrument flying do not have any kind of autopilot, and that includes many airplanes used for training purposes. Further, you only get into airplanes with auto-throttles to control thrust at the very, very high end of airplanes – airliners and such – again, certainly no training airplanes and not even the vast majority of the airplanes that exist have autothrottles.

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  2. Lemontree on Feb 05, 2017

    Thank you Russ for your clear explanation. I had big commercial jets like Boeing and Airbus in mind when I said aircrafts always use AP for approaches. I should’ve been clearer on that. Thanks.

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  3. Lemontree on Feb 05, 2017

    Russ, could I ask you a follow-up question? I just found out that we can’t lower the minimum to 1800 feet unless there’s a specific note on that on the chart, even if we’re using AP, FD, or HUD to the DA. My question is: does it equally apply to the lower CAT I minimum with “touchdown zone and centerline lights”? I mean, when we have those lights at work, we can lower the minimum to 1800 feet. In this case as well, do we need the note saying something like “RVR 1800 authorized with the use of touchdown zone and centerline lights” on the chart to fly the lower RVR minimum?

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