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3 Answers

Use of MOCA during IFR Flight

Asked by: 4225 views Airspace, General Aviation, Instrument Rating

Hi everyone, I have a question about using the MOCA during IFR flight-According to 91.177 the MOCA may be used provided the applicable navigation signals are available (meaning within 22 nm of a VOR if using a VOR for navigation). If I'm using a GPS for navigation (and filed myself as a "/G" with FSS) could I use the MOCA even if I'm more than 22nm from a VOR (assuming ATC allows me to have it of course). Thanks! Matt

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3 Answers

  1. Lucas on Jun 20, 2013

    Short answer: Yes.

    Long answer: safety should always come first in aviation. Accidents happen and changes are made. When you can’t see the ground, would you be comfortable being close to it?
    MOCA means Minimum Obstruction Clearance Altitude. If your GPS fails you might find yourself in a very uncomfortable position.


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  2. Wes Beard on Jun 20, 2013

    I don’t know if you can fly at the MOCA altitude while using GPS as the primary navaid or not. It is an interesting question.

    There are new MEAs just for GPS equipped aircraft. These are typically lower altitudes than the current MEAs based on VOR airways.

    From KARLO to PRC on V105 has one of these GPS MEAs.

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  3. Mark Kolber on Jun 26, 2013

    I don’t see any regulatory reason why not. Most of the procedural texts describe the 22 NM VOR limitation but, according to the reg, the only requirement is the availability of a reliable navigational signal. The 22 NM limittaion only applies when VOR navigation is being used. Here’s what the applicable reg says (with my emphasis):


    91.177(a) Operation of aircraft at minimum altitudes. Except when necessary for takeoff or landing, or unless otherwise authorized by the FAA, no person may operate an aircraft under IFR below–

    (1) The applicable minimum altitudes prescribed in parts 95 and 97 of this chapter. However, if both a MEA and a MOCA are prescribed for a particular route or route segment, a person may operate an aircraft below the MEA down to, but not below, the MOCA, provided the applicable navigation signals are available. For aircraft using VOR for navigation, this applies only when the aircraft is within 22 nautical miles of that VOR (based on the reasonable estimate by the pilot operating the aircraft of that distance); or

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