project logo   Aero Acronyms and Abbreviations 
inside the flightdeck

Compiled by Manuel Bessler

A/C     AirCraft, or simply airplane
A/P     Autopilot, electronic aid that can fly the A/C, mostly used during cruise to keep the A/C flying on course without having the Pilot keep his hands on the controls all the time.
A/T     Autothrottle, A/P Subsystem that controls the throttle
MSL     Mean Sea Level, Standardized height figure, Altimeters show the current A/C height over MSL
AGL     Above Ground Level, height above the Ground over which you are currently flying
MSA     Minimum Safe Altitude, provides minimum of 1000ft clearance from obstructions and terrain
MDA     Minimum Descend Altitude, during an approach, this specifies the minimum Altitude (MSL) before the runway is in sight and a safe landing can be made
MEA     Mean Enroute Altitude
MOCA    Minimum Obstruction Clearance Altitude
WCA     Wind Correction Angle
DH      Decision Height, point on G/S where to decide to continue landing or missed approach, similar to MDA, for precision approaches, determined by altimeter, lowest height where an approach can be flown by instrument alone
ATIS    Automatic Terminal Information Service
PD      Primary Display
ND      Navigation Display
EICAS   Engine Indication and Crew Alerting System
DG      Directional Gyro
FD      Flight Director, horizontal and vertical bars on your PD
DME     Distance Measuring Equipment, measures the distance(slant, not on-ground distance) to the tuned in VOR,
SDF     Simple Directional Facility,
ADF     Automatic Direction Finder, tuned to NDB
RMI     Radio Magnetic Indicator
NDB     Non Directional Beacon, LW, sends out Morse code of its ID, reception only reliable > 1000ft AGL
VOR     VHF Omnidirectional Range
OBS     Omni Bearing Selector, part of a VOR gauge, used to rotate the course card
CDI     Course Deviation Indicator, part of a VOR gauge, a needle showing whether you are on course (centered) or not (left or right)
IFR     Instrument Flight Rules, 0-179: odd thousands, 180-359: even thousands
VFR     Visual Flight Rules, 0-179: odd thousands+500ft, 180-359: even thousands+500ft
SID     Standard Instrument Departure, for takeoffs, specifies the route from the runway to the first waypoint
STAR    Standard Terminal Arrival, for landings, speciefies the route from the last waypoint down to the runway
IAF     Initial Approach Fix
FAF     Final Approach Fix
MAP     Missed Approach Point, touch down zone of runway
Precision Approach      Approach system that provides vertical guidance (eg. glide path), ILS is one
Non-Precision Approach  Approach system that does not provide vertical guidance (glide path),
GPS     Global Positioning System, allows a very exact measuring of location all over the world, based on satellites
LNAV    Lateral Navigation,
RNAV    Area Navigation, flying by longitude/latitude points that are not radio navigation aids, GPS or IRS is usually used.
VNAV    Vertical Navigation, A/P
LOC     Localizer, provides lateral guidance during ILS, VHF, always goes together with G/S, usable 18NM from field
LOC-A   an approach plate that ends with a letter indicates that a circling approach is required
G/S     Glideslope, provides vertical guidance during ILS, UHF, always goes together with LOC, usually 3deg, usable 10NM from field
OM      Outer Marker, part of ILS, beacon that provides range information, 4-7NM from runway threshold
MM      Middle Marker, part of ILS, beacon that provides range information, 3500ft from runway threshold
IM      Inner Marker, part of ILS, beacon that provides range information, only for Cat II where it is the DH point, 100ft from runway threshold
BC      Back Course, part of ILS, beacon that provides range information, like OM/MM/IM, specifies FAF for back course, a back course is non-precison since no G/S associated
LDA     Localizer-type Directional Aid, similar to LOC, but offset from runway heading, the approach path is not lined up with runway
RTO     Rejected Takeoff
Approach Plate  Charts containing information on approaching a specific Airport,
Terminal Procedures     new name for IAP
Navaid  Helper for navigation, eg: NDB, Fixes, VOR, GPS
TDZE    Touch Down Zone Elevation, the MSL of the touch down point of a runway
Apt Elev        Airport Elevation, the MSL of a central point of an airport
IAP     Intstrument Approach Plate, see Approach Plate, aka. Terminal Procedures
ICAO    , an Airport Designator, used for Navigation
IATA    , an Airport Designator, used on Flight Tickets, Baggage,...
MALSR   Medium intensity Approach Lighting System with Runway alignment indicator lights, a type of Runway Approach lighting
MIRL    Medium Intensity Runway Lights
VASI    Visual Approach Slope Indicator, an approach lighting system, typically two lights left of the runway,
PAPI    Precision Approach Path Indicator, similar to VASI, but more precise, uses four lights
CTAF    Common Traffic Advisory Frequency, only available at airfields with no control tower
ASOS    Automated Surface Observation System, measures and broadcasts surface wheather info automatically
RVR     Runway Visibility Range,
TACAN   Tactical Air Navigation, military
VORTAC  VHF Omni-Directional Range/Tactical Air Navigation, military
MLS     Microwave Landing System
TAT     Total Air Temperature, this is derived by correcting the RAT for position. Still contains an error due to the compressibility of air inside the temperature probe.
RAT     Ram Air Temperature, the raw, non-corrected temp. as measured by the temperature probe. Errors due to the Ram effect (air compressed in the probe) and the position (air may be disturbed by parts of the airplane, and also due to the effect of the air compression in front of the plane)
SAT     Static Air Temperature, same as OAT
OAT     Outside Air Temperature, the temperature of undisturbed air, derived by correcting TAT for compressibility errors
PF      Pilot Flying, the person that currently controls the airplane, can be either Captain or F/O
PNF     Pilot Non-Flying, the person who's not the PF
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