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How to Ensure Obstacle Clearance during IFR Descent

Asked by: 1959 views Instrument Rating

If you’re planning an IFR XC and the destination airport does not have a STAR, how do you ensure obstacle between the last waypoint on the airway and the IAF? Would you have to just stay above the OROCA until you’re on a segment of the approach? Some approaches wouldn’t give you much time to descent from cruising altitude and not all approaches have holding patterns to lose altitude. 

1 Answers



  1. John D Collins on Jul 29, 2022

    Most approaches will have feeder routes with published minimum altitudes from airways to an IAF if the IAF is not a fix on an airway. For many RNAV approach procedures and some conventional ILS approaches, there is a TAA which publishes minimum sector altitudes that may be used within 30 NM of a specific IAF. Otherwise, radar surveillance allows aircraft to descend to a MVA. Centers also make use of MIA which provide an altitude that aircraft may be descended to that is often below the OROCA altitude. The OROCA is a crude indication of a minimum altitude based on a 1 degree grid. It is not used by ATC. ATC will assign an altitude based on the MIA/MEA/MVA/MOCA or procedure altitude.

    From the AIM, this note is published:

    NOTE−
    OROCA is a published altitude which provides 1,000 feet of terrain and obstruction clearance in the US (2,000 feet of clearance in designated mountainous areas). These altitudes are not assessed for NAVAID signal coverage, air traffic control surveillance, or communications coverage, and are published for general situational awareness, flight planning and in−flight contingency use.

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