Federal Airways & Airspace
 Airspace Obstacle Management Software & Consulting Services
 Web Resources
 General Resources
Acronyms / Definitions
VFR Definitions
Private Airports
Links to State DOTs
 Obstruction Standards
 FAA Publications
 Software How-to
 State Filing Forms
Related Links
Request a brochure
TowAir admits errors
Software Products
Consulting Services

Aviation Acronyms

 Acronym Meaning Additional Information
AMSL Above Mean Sea Level  
ARP Airport Reference Point  
FAA Federal Aviation Administration  
FCC Federal Communication Commission  
GPS Global Positioning System  
IAP Instrument Approach Procedure  
ILS Instrument Landing System  
LOC Localizer  
MLS Microwave Landing System  
NDB Non-Directional Beacon Allows the pilot to fly between two locations using ground based transmitters and airborne receivers. NDBs emit a continuous radio signal, like spokes coming from the hub of a wheel. Each spoke (bearing) is a path to the NDB Aircraft use an automatic direction finder to locate the NDB by following the "spokes" (bearing) to the NDB. Each NDB has its own identifier or ident.
NOAA National Oceanic & Atmospheric Administration  
OMS Obstacle Management System  
PAR Precision Approach Radar  
RNAV Area Navigation  
VOR Very High Frequency Omni Directional Range  
 Term Definition
Horizontal Surface The plane 150’ above the established ARP for utility or visual runway surface extends 5000’ all others 10,000’
Conical Surface Extends 4000’ past where the horizontal surface ends – slope is 20/1 – every 20 ‘ in horizontal surface distance increases in height by 1’.
Transitional Surface Connects obstacle surfaces together -- connects approach surface to horizontal and conical.
Runway types
Visual No instrumental procedures – intended solely for aircraft using visual approach procedures w/no straight-in instrument approach procedures (existing or planned)
Non-Precision Instrument Runway has an existing or planned instrument approach procedure utilizing air navigation facilities with only horizontal guidance or area type navigational equipment (VOR, NDB, GPS) Straight-in only.
Precision Has existing or planned instrument approach procedure utilizing an ILS, MLS or PAR. Horizontal & vertical guidance.
Types of VORs
VOR Basic Navigational facility provides lateral information signals
VOR/DME Lateral information and distance (DME) straight line distance from station
TACAN Tactical Air Navigation – used by military – requires airborne military TACAN receivers
50/1 Precision
34/1 Non-Precision
20/1 Conical
A localizer is one component of an ILS or Instrument Landing System. The localizer usually provides runway centerline guidance to aircraft. In some cases a localizer is at an angle to the runway usually due to obstructions around the airport. Localizers also exist in stand-alone instrument approach installations and are not always part of an ILS or Instrument Landing System
Airport Surface Detection Equipment-- enables air traffic controllers to detect potential runway conflicts by providing detailed coverage of movement on runways and taxiways, by collecting data from a variety of sources.
Remote Transmitter/Receiver
Airport surveillance radar systems are capable of reliably detecting and tracking aircraft at altitudes below 25,000 feet (7,620 meters) and within 40 to 60 nautical miles (75 to 110 km) of their airport.
A ground radio station consisting of a collocated very-high-frequency Omnidirectional radio range (VOR) and TACAN facility; this station permits obtaining polar coordinates by the use of VOR receiver and distance-measuring equipment, or by TACAN equipment alone.