People and Authorities
CAA | Civil Aviation Authority. The UK’s aviation regulator.
AO | Aircraft Operator Individuals or organizations that own or manage the tools, procedures, and data necessary for the aircraft’s overall missions.
PIC | Pilot in Command The pilot is tasked with the control and operation of the aircraft during flight.
SIC | Second in Command The co-pilot is designated to take over the controls under the direction of the pilot in command.
FBO | Fixed-Base Operator An entity that provides services such as fuel, maintenance, and flight training, among others, at an airport.
FSS | Flight Service Station Facilities that offer pilot briefings and routine en-route communications.
EFAS | En Route Flight Advisory Service Technology that provides en-route aircraft with crucial flight updates and weather alerts.
GA | General Aviation This term refers to civil aviation flights excluding military, scheduled airline and cargo flights.
Operational Acronyms
VFR | Visual Flight Rules These guidelines govern flights flown by visual references only.
IFR | Instrument Flight Rules These are guidelines for flights in conditions that require more than just visual references.
VMC | Visual Meteorological Conditions These are weather conditions that permit VFR.
IMC | Instrument Meteorological Conditions These are weather conditions that necessitate IFR.
AVGAS | Aviation Gasoline This is the fuel used in piston aircraft.
MEL | Minimum Equipment List This is a catalogue of the necessary instruments, equipment, and procedures for piloting a specific aircraft.
UNICOM | Universal Communication This is a shared radio frequency used at non-tower airports for local pilot communication.
METAR | Meteorological Aerodrome Report This report details observed weather conditions at an airport.
ATD | Actual Time of Departure This is when a pilot departs from an airstrip or airport.
ETD | Estimated Time of Departure This is the planned departure time from an airstrip or airport.
ATA | Actual Time of Arrival: When a pilot lands at a destination.
ETA | Estimated Time of Arrival This is the planned arrival time at a destination.
ATIS | Automated Terminal Information Service This is a continuous broadcast of important information, including wind direction, velocity, atmospheric pressure readings, and active runway assignments.
Instrumentation Acronyms
A/C | Aircraft This refers to the aircraft, not air conditioning.
ADI | Attitude Direction Indicator This instrument shows the aircraft’s orientation relative to the horizon, showing the roll and pitch of the aircraft.
DME | Distance Measuring Equipment This instrument measures slant range distance from a navigational aid.
ALT | Altimeter This instrument measures the aircraft’s altitude.
HDG | Heading This refers to the direction the aircraft’s nose is pointing.
NAV | Navigation System This is the aircraft’s directional system.
GPS | Global Positioning System This is a satellite-based navigation information system.
VSI | Vertical Speed Indicator This instrument displays an aircraft’s rate of ascent or descent.
OAT | Outside Air Temperature Gauge This instrument shows the temperature of the air immediately outside the aircraft.
EHSI (or HSI) | Electronic Horizontal Situation Indicator This combined instrument displays heading information and course deviation.
VOR | VHF Omnidirectional Range This is a short-range, ground-based radio navigation system for aircraft.
Common In-Flight Terms
CAS | Calibrated Airspeed This is the indicated airspeed of an aircraft, corrected for position and instrument errors.
IAS | Indicated Airspeed This is a direct instrument reading uncorrected for position and instrument errors.
CAT | Clear Air Turbulence refers to turbulent conditions without visible cues, such as clouds.
CAVU | Ceiling and Visibility Unlimited This term describes ideal flying weather.
AGL | Above Ground Level This measures altitude above a specific land mass.
MSL | Mean Sea Level This is the average height from the sea surface for all tide stages.
ALS | Approach Light System This is a lighting system on the approach end of the airport runway.
AGR | Air-Ground Ranging This refers to the straight-line distance from the aircraft to a point on the ground.
