OROCA IFR enroute low

[dennyleeb]

On ifr low alt charts you have the oroca. How do you define the area that a specific number represents. Had my rating for a while but normally fly high. This week w possible ice I will have to stay a little lower than normal and my memory on this has slipped.

 

[gismo]

On ifr low alt charts you have the oroca. How do you define the area that a specific number represents. Had my rating for a while but normally fly high. This week w possible ice I will have to stay a little lower than normal and my memory on this has slipped.

THIS CHART CONTAINS OFF ROUTE OBSTRUCTION CLEARANCE ALTITUDES (OROCA). The off route obstruction clearance altitudes shown in quadrangles
bounded by ticked lines of latitude and longitude are represented in THOUSANDS and HUNDREDS of feet above mean sea level. The OROCA is based on information
available concerning the highest known features in each quadrangle, including terrain and obstructions. OROCA provides obstruction clearance with a 1000 foot buffer in
designated non-mountainous areas and a 2000 foot buffer in designated mountainous areas within the United States. For areas in Mexico and the Caribbean which are
located outside of the U.S. ADIZ, OROCA provides obstruction clearance with a 3000 foot buffer. This altitude is provided for obstruction clearance only. It does not
provide for NAVAID signal coverage or communication coverage, and would not be consistent with altitudes assigned by Air Traffic Control.

Basically the same areas as marked on VFR sectionals except OROCA includes a vertical 1000ft (2000 in the mountains) buffer and a 4 mile lateral buffer.

 

[poadeleted20]

Just remember that the OROCA is effectively "emergency use only." Other than that, the minimum altitude you can use when not on a published route will be the MVA for that sector on the controller's scope, which is usually a lot lower than the OROCA anyway.