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3 Answers

Altitude for an arc when given altitude below IAF

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Instrument Rating

Reference KRAP Rapid City, SD VOR RWY 14. We were given a lower altitude ~6,800 because of turbulence (somewhere between MUDDY and the West IAF). Then we were cleared for the approach. Are we expected to climb up to 7700 and follow the arc down, or just hold 6800 until R-300?

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3 Answers



  1. R. Anderson on Jul 24, 2017

    Based on your question, I’m assuming your are on a radar vector. (if not, please clarify and disregard my answer).

    If you were being vectored you should have been given a heading that would put you inside of the west IAF on the arc and instructed to maintain a specific altitude until some point on the procedure.

    Normally, ATC would instruct you to maintain an altitude until established on some part of the approach and, once established, you could “descend” as published on the procedure. But since you were already below the altitude of the initial portion of the arc (6800 vs 7700), the controller should have instructed you to maintain a certain altitude until (probably R-300) where you could descend as published.

    The controller’s minimum vectoring altitude can be lower than what is shown on the chart.

    But, your question is a bit unclear as to what additional info/instructions were provided by the controller.

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  2. Mark Kolber on Jul 27, 2017

    It is a rarity, but I have seen other similar situations – a controller brings an aircraft to an altitude and then clears for the approach via a segment with a higher MIA.

    Like, R Anderson, I would expect an altitude instruction in the clearance if the controller wanted me to remain at the lower altitude. “Maintain 6800 until established on the final approach course,” or something like that. In its absence, I would ask for clarification and if, “maintain 6800” was =not= part of it, climb back to the altitude that was TERPS-vefified and flight-checked to ensure clearance from obstructions.

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  3. John D Collins on Jul 27, 2017

    Controllers have guidance on this topic.

    5-8-1 (b)

    For aircraft operating on unpublished routes, issue the approach clearance only after the aircraft is:
    1. Established on a segment of a published route or instrument approach procedure, or
    2. Assigned an altitude to maintain until the aircraft is established on a segment of a published route or instrument approach procedure.

    NOTE−
    1. The altitude assigned must assure IFR obstruction clearance from the point at which the approach clearance is issued until established on a segment of a published route or instrument approach procedure.

    3. An aircraft is not established on an approach until at or above an altitude published on that segment of the approach.

    So a valid clearance to the west IAF could not be issued unless the aircraft was above 7700 MSL. A valid clearance to RAP using the feeder route to FERMI as the IAF could be authorized by the controller as long as the conditions stated above were met, so if there was radar monitoring and terrain clearance at 6800 MSL to RAP (at or above the MVA), you could be cleared direct to RAP, maintain 6800 until RAP, cleared VOR RWY 14 approach

    But I don’t believe you should be cleared for the approach along the western arc IAF below an altitude of 7700.

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