An example of a steep approach would be London City Airport (EGLC). However, there are also steep approaches performed at some airports (usually 5 degrees). This is typically a 3 degree gradient at most airports. Glideslope – abbreviated as the GS, the Glideslope provides the aircraft with vertical guidance to the runway.Localizer – as discussed above, the LOC provides the lateral guidance to the aircraft in relation to the centreline of the runway.There are several components that form an ILS system, each component’s respective function corresponds to a specific phase of the approach. This is generally activated via the pertinent button located on the aircraft’s autopilot panel.īy engaging APPR mode, there is now capability for the aircraft to intercept the Glideslope (GS) component of the approach if it is an ILS approach. Upon intercepting the localizer, it is then possible to switch to Approach Mode (APPR). Due to surrounding terrain, ATC instructions, and noise abatement procedures specific to the arrival airport, the LOC is usually intercepted and followed ahead of the Glideslope (GS). Like a LOC approach, VOR/LOC only concerns the lateral guidance of the aircraft in relation to the runway.Įssentially, the aircraft is flying the localizer via a VOR located in close proximity. This typically occurs when the aircraft flies on an inbound radial of a VOR followed by subsequently intercepting the localizer. In some instances, VOR/LOC may be encountered. This is particularly ideal when flying in low visibility conditions. LOC approaches are rarely performed due to these limitations, ILS approaches are the preferred form of instrument approaches due to the low decision heights. This means that there are greater limitations for performing a LOC approach in poor weather conditions. However, the lack of vertical guidance to the runway in this form of approach will greatly increase the Decision Height (DH) required. When the localizer has been captured or intercepted, this hollow magenta diamond will then become a solid magenta, as a form of confirmation.Ī LOC approach may be performed in an instance where there is no ILS available for the arrival runway. The hollow magenta diamond indicates the aircraft’s position in relation to the path of the localizer. Localizer Magenta Cue on the PFD (Airbus)Īs can be seen above, the lateral guidance (localizer) is being provided on the lower portion of the PFD. The course for the runway in which an approach is being conducted will be preselected in either the Flight Management System (FMS) and/or on the autopilot control panel under the CRS section. The lateral cues are usually displayed on the bottom half of the PFD, in a magenta-like format. In the cockpit of modern commercial aircraft, the localizer portion is given typically on the Primary Flight Display (PFD). These lateral cues correspond to the centreline of the runway being approached. As mentioned above, there is only a horizontal or lateral component present in this form of approach. LOC ApproachĪ LOC approach can be defined as a non-precision approach, in which there is no vertical guidance or descent profile provided to the runway. An ILS approach consists of both the lateral (localizer) and vertical (glideslope) components. The difference between an ILS and LOC approach is that a LOC consists only of lateral/horizontal guidance to the runway centreline. Two forms of instrument approaches are an ILS – short for Instrument Landing System, and LOC – which stands for the localizer. The theory, hardware description, and performance of the low cost localizer system is discussed with conclusions drawn from system performance data and with recommendations for system improvements.Under Instrument Flight Rules (IFR), there are a number of different instrument approaches which may be performed, depending on the airport’s infrastructure and the aircraft’s capabilities. Additional low cost localizer equipment was added to provide for specialized remote monitor and control functions, including standby equipment with transfer unit. These arrays are commissioned and operating with existing FAA localizer equipment. Additional V-Ring Antenna Arrays were delivered for upgrading existing marginal localizer sites. Mechanical modulation is employed in conjunction with a low power transmitter and solid state monitor for long term reliable service. System performance is equivalent or better than ICAO Category I standards. A wide aperture antenna array with suitable directivity about the course line is provided in order to reduce the influence of siting errors. Abstract: The objectives of the contract were to design, develop, fabricate, and deliver a complete low cost localizer system which would be suitable for secondary airports and still provide for all the basic operations of a localizer system.
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