Localizer
Encyclopedia
In aviation, a localizer (LLZ) is one of the components of an Instrument Landing System
(ILS), and it provides runway centerline guidance to aircraft. In some cases, a course projected by localizer is at an angle to the runway (usually due to obstructions around the airport
). It is then called a Localizer Type Directional Aid
(LDA). Localizers also exist in stand-alone instrument approach installations and are not always part of an ILS. The localizer is placed about 1,000 feet from the far end of the approached runway. Its useful volume extends to 18 NM for the path up to 10 degrees either side of the course. For an angle of 35 degrees either side of the course the useful volume of the localizer extends up to 10 NM. Horizontal guidance gets more accurate the closer you fly to the localizer station. Localizer approaches have their specific weather minimums found on approach plates.
Instrument Landing System
An instrument landing system is a ground-based instrument approach system that provides precision guidance to an aircraft approaching and landing on a runway, using a combination of radio signals and, in many cases, high-intensity lighting arrays to enable a safe landing during instrument...
(ILS), and it provides runway centerline guidance to aircraft. In some cases, a course projected by localizer is at an angle to the runway (usually due to obstructions around the airport
Airport
An airport is a location where aircraft such as fixed-wing aircraft, helicopters, and blimps take off and land. Aircraft may be stored or maintained at an airport...
). It is then called a Localizer Type Directional Aid
Localizer Type Directional Aid
A Localizer Type Directional Aid is a type of localizer-based instrument approach to an airport. It is used in places where, due to terrain and other factors, the localizer antenna array is not aligned with the runway it serves. In these cases, the localizer antenna array may be offset A Localizer...
(LDA). Localizers also exist in stand-alone instrument approach installations and are not always part of an ILS. The localizer is placed about 1,000 feet from the far end of the approached runway. Its useful volume extends to 18 NM for the path up to 10 degrees either side of the course. For an angle of 35 degrees either side of the course the useful volume of the localizer extends up to 10 NM. Horizontal guidance gets more accurate the closer you fly to the localizer station. Localizer approaches have their specific weather minimums found on approach plates.
See also
- AN/MRN-1AN/MRN-1The AN/MRN-1 was an instrument approach localizer used by the Army Air Force during and after World War II. It was standardized on 3 July 1942. It replaced the SCR-241, and was a component of SCS-51.-Use:...
- Andrew AlfordAndrew AlfordAndrew Alford was an American electrical engineer and inventor.Born in Samara, Russia, Alford invented and developed antennas for radio navigation systems, now used for VHF omnidirectional range and instrument landing systems....
- Instrument approachInstrument approachFor aircraft operating under instrument flight rules , an instrument approach or instrument approach procedure is a series of predetermined maneuvers for the orderly transfer of an aircraft under instrument flight conditions from the beginning of the initial approach to a landing, or to a point...
- Instrument landing systemInstrument Landing SystemAn instrument landing system is a ground-based instrument approach system that provides precision guidance to an aircraft approaching and landing on a runway, using a combination of radio signals and, in many cases, high-intensity lighting arrays to enable a safe landing during instrument...
- Simplified Directional FacilitySimplified Directional FacilitySimplified Directional Facility or SDF is a localizer-based instrument non-precision approach to an airport, which provides final approach course similar to Instrument Landing System and Localizer Type Directional Aid approaches, although not as precise.The SDF signal is fixed at either 6 or 12...
- Localizer Type Directional AidLocalizer Type Directional AidA Localizer Type Directional Aid is a type of localizer-based instrument approach to an airport. It is used in places where, due to terrain and other factors, the localizer antenna array is not aligned with the runway it serves. In these cases, the localizer antenna array may be offset A Localizer...