(a) This part prescribes altitudes governing the operation of aircraft
under IFR on ATS routes, or other direct routes for which an MEA is
designated in this part. In addition, it designates mountainous areas and
(b) The MAA is the highest altitude on an ATS route, or other direct
route for which an MEA is designated, at which adequate reception of VOR
signals is assured.
(c) The MCA applies to the operation of an aircraft proceeding to a
higher minimum en route altitude when crossing specified fixes.
(d) The MEA is the minimum en route IFR altitude on an ATS route, ATS
route segment, or other direct route. The MEA applies to the entire width
of the ATS route, ATS route segment, or other direct route between fixes
defining that route. Unless otherwise specified, an MEA prescribed for an
off airway route or route segment applies to the airspace 4 nautical miles
on each side of a direct course between the navigation fixes defining that
route or route segment.
(e) The MOCA assures obstruction clearance on an ATS route, ATS route
segment, or other direct route, and adequate reception of VOR navigation
signals within 22 nautical miles of a VOR station used to define the
(f) The MRA applies to the operation of an aircraft over an
intersection defined by ground-based navigation aids. The MRA is the
lowest altitude at which the intersection can be determined using the
ground-based navigation aids.
(g) The changeover point (COP) applies to operation of an aircraft
along a Federal airway, jet route, or other direct route; for which an MEA
is designated in this part. It is the point for transfer of the airborne
navigation reference from the ground-based navigation aid behind the
aircraft to the next appropriate ground-based navigation aid to ensure
continuous reception of signals.