Pilot/Controller Glossary

c. As otherwise authorized by the Administrator
or assigned by ATC.

published procedures as "Emergency Safe
Altitudes."

(See MINIMUM CROSSING ALTITUDE.)
(See MINIMUM EN ROUTE IFR ALTITUDE.)
(See MINIMUM OBSTRUCTION CLEARANCE
ALTITUDE.)
(See MINIMUM SAFE ALTITUDE.)
(See MINIMUM VECTORING ALTITUDE.)
(Refer to 14 CFR Part 91.)

MINIMUM SAFE ALTITUDE WARNING
(MSAW)- A function of the ARTS III computer that
aids the controller by alerting him/her when a tracked
Mode C equipped aircraft is below or is predicted by
the computer to go below a predetermined minimum
safe altitude.

MINIMUM OBSTRUCTION CLEARANCE ALTITUDE (MOCA)- The lowest published altitude in
effect between radio fixes on VOR airways,
off-airway routes, or route segments which meets
obstacle clearance requirements for the entire route
segment and which assures acceptable navigational
signal coverage only within 25 statute (22 nautical)
miles of a VOR.

MINIMUM SECTOR ALTITUDE [ICAO]- The
lowest altitude which may be used under emergency
conditions which will provide a minimum clearance
of 300 m (1,000 feet) above all obstacles located in
an area contained within a sector of a circle of 46 km
(25 NM) radius centered on a radio aid to navigation.

(Refer to 14 CFR Part 91.)
(Refer to 14 CFR Part 95.)

MINIMUM RECEPTION ALTITUDE (MRA)- The
lowest altitude at which an intersection can be
determined.
(Refer to 14 CFR Part 95.)

MINIMUM SAFE ALTITUDE (MSA)-
a. The minimum altitude specified in 14 CFR
Part 91 for various aircraft operations.
b. Altitudes depicted on approach charts which
provide at least 1,000 feet of obstacle clearance for
emergency use. These altitudes will be identified as
Minimum Safe Altitudes or Emergency Safe
Altitudes and are established as follows:
1. Minimum Safe Altitude (MSA). Altitudes
depicted on approach charts which provide at least
1,000 feet of obstacle clearance within a 25-mile
radius of the navigation facility, waypoint, or airport
reference point upon which the MSA is predicated.
MSAs are for emergency use only and do not
necessarily assure acceptable navigational signal
coverage.
(See ICAO term Minimum Sector Altitude.)

2. Emergency Safe Altitude (ESA). Altitudes
depicted on approach charts which provide at least
1,000 feet of obstacle clearance in nonmountainous
areas and 2,000 feet of obstacle clearance in
designated mountainous areas within a 100-mile
radius of the navigation facility or waypoint used as
the ESA center. These altitudes are normally used
only in military procedures and are identified on

(Refer to AIM.)

MINIMUMS- Weather condition requirements
established for a particular operation or type of
operation; e.g., IFR takeoff or landing, alternate
airport for IFR flight plans, VFR flight, etc.
(See IFR CONDITIONS.)
(See IFR TAKEOFF MINIMUMS AND
DEPARTURE PROCEDURES.)
(See LANDING MINIMUMS.)
(See VFR CONDITIONS.)
(Refer to 14 CFR Part 91.)
(Refer to AIM.)

MINIMUM VECTORING ALTITUDE (MVA)-
The lowest MSL altitude at which an IFR aircraft will
be vectored by a radar controller, except as otherwise
authorized for radar approaches, departures, and
missed approaches. The altitude meets IFR obstacle
clearance criteria. It may be lower than the published
MEA along an airway or J-route segment. It may be
utilized for radar vectoring only upon the controller"s
determination that an adequate radar return is being
received from the aircraft being controlled. Charts
depicting minimum vectoring altitudes are normally
available only to the controllers and not to pilots.
(Refer to AIM.)

MINUTES-IN-TRAIL- A specified interval between aircraft expressed in time. This method would
more likely be utilized regardless of altitude.
MIS-
(See METEOROLOGICAL IMPACT
STATEMENT.)

MISSED APPROACH-
a. A maneuver conducted by a pilot when an
instrument approach cannot be completed to a