Pilot/Controller Glossary
3/29/18
PCG M1
M
MAA
(See MAXIMUM AUTHORIZED ALTITUDE.)
MACH NUMBER The ratio of true airspeed to the
speed of sound; e.g., MACH .82, MACH 1.6.
(See AIRSPEED.)
MACH TECHNIQUE [ICAO] Describes a control
technique used by air traffic control whereby turbojet
aircraft operating successively along suitable routes
are cleared to maintain appropriate MACH numbers
for a relevant portion of the en route phase of flight.
The principle objective is to achieve improved
utilization of the airspace and to ensure that
separation between successive aircraft does not
decrease below the established minima.
MAHWP Missed Approach Holding Waypoint
MAINTAIN
a. Concerning altitude/flight level, the term
means to remain at the altitude/flight level specified.
The phrase “climb and” or “descend and” normally
precedes “maintain” and the altitude assignment;
e.g., “descend and maintain 5,000.”
b. Concerning other ATC instructions, the term is
used in its literal sense; e.g., maintain VFR.
MAINTENANCE PLANNING FRICTION
LEVEL The friction level specified in
AC 150/5320-12, Measurement, Construction, and
Maintenance of Skid Resistant Airport Pavement
Surfaces, which represents the friction value below
which the runway pavement surface remains
acceptable for any category or class of aircraft
operations but which is beginning to show signs of
deterioration. This value will vary depending on the
particular friction measurement equipment used.
MAKE SHORT APPROACH Used by ATC to
inform a pilot to alter his/her traffic pattern so as to
make a short final approach.
(See TRAFFIC PATTERN.)
MAN PORTABLE AIR DEFENSE SYSTEMS
(MANPADS) MANPADS are lightweight,
shoulderlaunched, missile systems used to bring
down aircraft and create mass casualties. The
potential for MANPADS use against airborne aircraft
is real and requires familiarity with the subject.
Terrorists choose MANPADS because the weapons
are low cost, highly mobile, require minimal setup
time, and are easy to use and maintain. Although the
weapons have limited range, and their accuracy is
affected by poor visibility and adverse weather, they
can be fired from anywhere on land or from boats
where there is unrestricted visibility to the target.
MANDATORY ALTITUDE An altitude depicted
on an instrument Approach Procedure Chart
requiring the aircraft to maintain altitude at the
depicted value.
MANPADS
(See MAN PORTABLE AIR DEFENSE
SYSTEMS.)
MAP
(See MISSED APPROACH POINT.)
MARKER BEACON An electronic navigation
facility transmitting a 75 MHz vertical fan or
boneshaped radiation pattern. Marker beacons are
identified by their modulation frequency and keying
code, and when received by compatible airborne
equipment, indicate to the pilot, both aurally and
visually, that he/she is passing over the facility.
(See INNER MARKER.)
(See MIDDLE MARKER.)
(See OUTER MARKER.)
(Refer to AIM.)
MARSA
(See MILITARY AUTHORITY ASSUMES
RESPONSIBILITY FOR SEPARATION OF
AIRCRAFT.)
MAWP Missed Approach Waypoint
MAXIMUM AUTHORIZED ALTITUDE A pub-
lished altitude representing the maximum usable
altitude or flight level for an airspace structure or
route segment. It is the highest altitude on a Federal
airway, jet route, area navigation low or high route,
or other direct route for which an MEA is designated
in 14 CFR Part 95 at which adequate reception of
navigation aid signals is assured.
MAYDAY The international radiotelephony distress
signal. When repeated three times, it indicates
Pilot/Controller Glossary 3/29/18
PCG M2
imminent and grave danger and that immediate
assistance is requested.
(See PAN-PAN.)
(Refer to AIM.)
MCA
(See MINIMUM CROSSING ALTITUDE.)
MDA
(See MINIMUM DESCENT ALTITUDE.)
MEA
(See MINIMUM EN ROUTE IFR ALTITUDE.)
MEARTS
(See MICRO-EN ROUTE AUTOMATED RADAR
TRACKING SYSTEM.)
METEOROLOGICAL IMPACT STATEMENT
An unscheduled planning forecast describing
conditions expected to begin within 4 to 12 hours
which may impact the flow of air traffic in a specific
centers (ARTCC) area.
METER FIX ARC A semicircle, equidistant from
a meter fix, usually in low altitude relatively close to
the meter fix, used to help CTAS/ERAM calculate a
meter time, and determine appropriate sector meter
list assignments for aircraft not on an established
arrival route or assigned a meter fix.
METER FIX TIME/SLOT TIME (MFT) A
calculated time to depart the meter fix in order to
cross the vertex at the ACLT. This time reflects
descent speed adjustment and any applicable time
that must be absorbed prior to crossing the meter fix.
METER LIST
(See ARRIVAL SECTOR ADVISORY LIST.)
METER LIST DISPLAY INTERVAL A dynamic
parameter which controls the number of minutes
prior to the flight plan calculated time of arrival at the
meter fix for each aircraft, at which time the TCLT is
frozen and becomes an ACLT; i.e., the VTA is
updated and consequently the TCLT modified as
appropriate until frozen at which time updating is
suspended and an ACLT is assigned. When frozen,
the flight entry is inserted into the arrival sectors
meter list for display on the sector PVD/MDM.
MLDI is used if filed true airspeed is less than or
equal to freeze speed parameters (FSPD).
METERING A method of time-regulating arrival
traffic flow into a terminal area so as not to exceed a
predetermined terminal acceptance rate.
METERING AIRPORTS Airports adapted for
metering and for which optimum flight paths are
defined. A maximum of 15 airports may be adapted.
METERING FIX A fix along an established route
from over which aircraft will be metered prior to
entering terminal airspace. Normally, this fix should
be established at a distance from the airport which
will facilitate a profile descent 10,000 feet above
airport elevation (AAE) or above.
METERING POSITION(S) Adapted PVDs/
MDMs and associated “D” positions eligible for
display of a metering position list. A maximum of
four PVDs/MDMs may be adapted.
METERING POSITION LIST An ordered list of
data on arrivals for a selected metering airport
displayed on a metering position PVD/MDM.
MFT
(See METER FIX TIME/SLOT TIME.)
MHA
(See MINIMUM HOLDING ALTITUDE.)
MIA
(See MINIMUM IFR ALTITUDES.)
MICROBURST A small downburst with outbursts
of damaging winds extending 2.5 miles or less. In
spite of its small horizontal scale, an intense
microburst could induce wind speeds as high as 150
knots
(Refer to AIM.)
MICRO-EN ROUTE AUTOMATED RADAR
TRACKING SYSTEM (MEARTS) An automated
radar and radar beacon tracking system capable of
employing both short-range (ASR) and long-range
(ARSR) radars. This microcomputer driven system
provides improved tracking, continuous data record-
ing, and use of full digital radar displays.
MID RVR
(See VISIBILITY.)
MIDDLE COMPASS LOCATOR
(See COMPASS LOCATOR.)
MIDDLE MARKER A marker beacon that defines
a point along the glideslope of an ILS normally
located at or near the point of decision height (ILS
Category I). It is keyed to transmit alternate dots and
dashes, with the alternate dots and dashes keyed at the
rate of 95 dot/dash combinations per minute on a
Pilot/Controller Glossary
3/29/18
PCG M3
1300 Hz tone, which is received aurally and visually
by compatible airborne equipment.
(See INSTRUMENT LANDING SYSTEM.)
(See MARKER BEACON.)
(Refer to AIM.)
MILES-IN-TRAIL A specified distance between
aircraft, normally, in the same stratum associated
with the same destination or route of flight.
MILITARY AUTHORITY ASSUMES RESPONSI-
BILITY FOR SEPARATION OF AIRCRAFT
(MARSA) A condition whereby the military
services involved assume responsibility for separa-
tion between participating military aircraft in the
ATC system. It is used only for required IFR
operations which are specified in letters of agreement
or other appropriate FAA or military documents.
MILITARY LANDING ZONE A landing strip used
exclusively by the military for training. A military
landing zone does not carry a runway designation.
MILITARY OPERATIONS AREA
(See SPECIAL USE AIRSPACE.)
MILITARY TRAINING ROUTES Airspace of
defined vertical and lateral dimensions established
for the conduct of military flight training at airspeeds
in excess of 250 knots IAS.
(See IFR MILITARY TRAINING ROUTES.)
(See VFR MILITARY TRAINING ROUTES.)
MINIMA
(See MINIMUMS.)
MINIMUM CROSSING ALTITUDE (MCA) The
lowest altitude at certain fixes at which an aircraft
must cross when proceeding in the direction of a
higher minimum en route IFR altitude (MEA).
(See MINIMUM EN ROUTE IFR ALTITUDE.)
MINIMUM DESCENT ALTITUDE (MDA) The
lowest altitude, expressed in feet above mean sea
level, to which descent is authorized on final
approach or during circle-to-land maneuvering in
execution of a standard instrument approach
procedure where no electronic glideslope is provided.
(See NONPRECISION APPROACH
PROCEDURE.)
MINIMUM EN ROUTE IFR ALTITUDE (MEA)
The lowest published altitude between radio fixes
which assures acceptable navigational signal cover-
age and meets obstacle clearance requirements
between those fixes. The MEA prescribed for a
Federal airway or segment thereof, area navigation
low or high route, or other direct route applies to the
entire width of the airway, segment, or route between
the radio fixes defining the airway, segment, or route.
(Refer to 14 CFR Part 91.)
(Refer to 14 CFR Part 95.)
(Refer to AIM.)
MINIMUM FRICTION LEVEL The friction level
specified in AC 150/5320-12, Measurement, Con-
struction, and Maintenance of Skid Resistant Airport
Pavement Surfaces, that represents the minimum
recommended wet pavement surface friction value
for any turbojet aircraft engaged in LAHSO. This
value will vary with the particular friction
measurement equipment used.
MINIMUM FUEL Indicates that an aircraft’s fuel
supply has reached a state where, upon reaching the
destination, it can accept little or no delay. This is not
an emergency situation but merely indicates an
emergency situation is possible should any undue
delay occur.
(Refer to AIM.)
MINIMUM HOLDING ALTITUDE The lowest
altitude prescribed for a holding pattern which
assures navigational signal coverage, communica-
tions, and meets obstacle clearance requirements.
MINIMUM IFR ALTITUDES (MIA) Minimum
altitudes for IFR operations as prescribed in 14 CFR
Part 91. These altitudes are published on aeronautical
charts and prescribed in 14 CFR Part 95 for airways
and routes, and in 14 CFR Part 97 for standard
instrument approach procedures. If no applicable
minimum altitude is prescribed in 14 CFR Part 95 or
14 CFR Part 97, the following minimum IFR
altitude applies:
a. In designated mountainous areas, 2,000 feet
above the highest obstacle within a horizontal
distance of 4 nautical miles from the course to be
flown; or
b. Other than mountainous areas, 1,000 feet above
the highest obstacle within a horizontal distance of 4
nautical miles from the course to be flown; or
Pilot/Controller Glossary 3/29/18
PCG M4
c. As otherwise authorized by the Administrator
or assigned by ATC.
(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 OBSTRUCTION CLEARANCE ALTI-
TUDE (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.
(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
published procedures as “Emergency Safe
Altitudes.”
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.
(Refer to AIM.)
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.
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 controllers
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 be-
tween 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
Pilot/Controller Glossary
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PCG M5
landing. The route of flight and altitude are shown on
instrument approach procedure charts. A pilot
executing a missed approach prior to the Missed
Approach Point (MAP) must continue along the final
approach to the MAP.
b. A term used by the pilot to inform ATC that
he/she is executing the missed approach.
c. At locations where ATC radar service is
provided, the pilot should conform to radar vectors
when provided by ATC in lieu of the published
missed approach procedure.
(See MISSED APPROACH POINT.)
(Refer to AIM.)
MISSED APPROACH POINT (MAP) A point
prescribed in each instrument approach procedure at
which a missed approach procedure shall be executed
if the required visual reference does not exist.
(See MISSED APPROACH.)
(See SEGMENTS OF AN INSTRUMENT
APPROACH PROCEDURE.)
MISSED APPROACH PROCEDURE [ICAO] The
procedure to be followed if the approach cannot be
continued.
MISSED APPROACH SEGMENT
(See SEGMENTS OF AN INSTRUMENT
APPROACH PROCEDURE.)
MLDI
(See METER LIST DISPLAY INTERVAL.)
MM
(See MIDDLE MARKER.)
MOA
(See MILITARY OPERATIONS AREA.)
MOCA
(See MINIMUM OBSTRUCTION CLEARANCE
ALTITUDE.)
MODE The letter or number assigned to a specific
pulse spacing of radio signals transmitted or received
by ground interrogator or airborne transponder
components of the Air Traffic Control Radar Beacon
System (ATCRBS). Mode A (military Mode 3) and
Mode C (altitude reporting) are used in air traffic
control.
(See INTERROGATOR.)
(See RADAR.)
(See TRANSPONDER.)
(See ICAO term MODE.)
(Refer to AIM.)
MODE (SSR MODE) [ICAO] The letter or number
assigned to a specific pulse spacing of the
interrogation signals transmitted by an interrogator.
There are 4 modes, A, B, C and D specified in Annex
10, corresponding to four different interrogation
pulse spacings.
MODE C INTRUDER ALERT A function of
certain air traffic control automated systems designed
to alert radar controllers to existing or pending
situations between a tracked target (known IFR or
VFR aircraft) and an untracked target (unknown IFR
or VFR aircraft) that requires immediate attention/ac-
tion.
(See CONFLICT ALERT.)
MODEL AIRCRAFT An unmanned aircraft that is:
(1) capable of sustained flight in the atmosphere; (2)
flown within visual line of sight of the person
operating the aircraft; and (3) flown for hobby or
recreational purposes.
MONITOR (When used with communication
transfer) listen on a specific frequency and stand by
for instructions. Under normal circumstances do not
establish communications.
MONITOR ALERT (MA) A function of the TFMS
that provides traffic management personnel with a
tool for predicting potential capacity problems in
individual operational sectors. The MA is an
indication that traffic management personnel need to
analyze a particular sector for actual activity and to
determine the required action(s), if any, needed to
control the demand.
MONITOR ALERT PARAMETER (MAP) The
number designated for use in monitor alert
processing by the TFMS. The MAP is designated for
each operational sector for increments of 15 minutes.
MOSAIC/MULTISENSOR MODE Accepts posi-
tional data from multiple radar or ADSB sites.
Targets are displayed from a single source within a
radar sort box according to the hierarchy of the
sources assigned.
MOUNTAIN WAVE– Mountain waves occur when
air is being blown over a mountain range or even the
Pilot/Controller Glossary 3/29/18
PCG M6
ridge of a sharp bluff area. As the air hits the upwind
side of the range, it starts to climb, thus creating what
is generally a smooth updraft which turns into a
turbulent downdraft as the air passes the crest of the
ridge. Mountain waves can cause significant
fluctuations in airspeed and altitude with or without
associated turbulence.
(Refer to AIM.)
MOVEMENT AREA The runways, taxiways, and
other areas of an airport/heliport which are utilized
for taxiing/hover taxiing, air taxiing, takeoff, and
landing of aircraft, exclusive of loading ramps and
parking areas. At those airports/heliports with a
tower, specific approval for entry onto the movement
area must be obtained from ATC.
(See ICAO term MOVEMENT AREA.)
MOVEMENT AREA [ICAO] That part of an
aerodrome to be used for the takeoff, landing and
taxiing of aircraft, consisting of the maneuvering area
and the apron(s).
MOVING TARGET INDICATOR An electronic
device which will permit radar scope presentation
only from targets which are in motion. A partial
remedy for ground clutter.
MRA
(See MINIMUM RECEPTION ALTITUDE.)
MSA
(See MINIMUM SAFE ALTITUDE.)
MSAW
(See MINIMUM SAFE ALTITUDE WARNING.)
MTI
(See MOVING TARGET INDICATOR.)
MTR
(See MILITARY TRAINING ROUTES.)
MULTICOM A mobile service not open to public
correspondence used to provide communications
essential to conduct the activities being performed by
or directed from private aircraft.
MULTIPLE RUNWAYS The utilization of a
dedicated arrival runway(s) for departures and a
dedicated departure runway(s) for arrivals when
feasible to reduce delays and enhance capacity.
MVA
(See MINIMUM VECTORING ALTITUDE.)
Pilot/Controller Glossary 9/13/18