Navigation Services

The ILS has been the mainstay of landing aids for well over 50 years. The modernized versions used by the FAA provide aircraft with precision vertical and horizontal navigation guidance information during approach and landing. Associated Marker Beacons and/or Low Power Distance Measuring Equipment (LPDME) identify distance to the runway. The attractiveness of ILS lies in the economy of its avionics costs and its wide international acceptance. Technology advances over the years have yielded great improvement in accuracy, dependability, and maintainability.

The FAA continues to support (ground based) ILS and will continue to procure and deploy new and replacement ILS for the foreseeable future. It is expected that ILS (ground based) will be eventually replaced with some type of GPS system in the future (see WAAS and LAAS). Presently the FAA has a contract with Thales, ATM to procure the Mark 20A ILS on a requirements contract. A new Thales 420 ILS system is undergoing OT&E. The 420 ILS will be procured after completion of the In-Service Decision.

The localizer generates and radiates signals to provide final approach azimuth navigation information to landing aircraft. The antenna sends 90-HZ and 150-HZ signals that the aircraft instruments determine as left and right of the centerline. The aircraft interprets the signal and displays them on the cockpit indicator guiding the pilot until the runway is in sight.

In a similar manner as the localizer (just turned 90 degrees on axis), the glide slope sends two frequencies that aircraft instruments determine as above or below the desired glideslope. This is approximately 3 degrees to the horizon which give the aircraft a decent of approximately 500 feet per minute.

For an ILS approach there are several components required. The Mark 20A and 420 ILS are the electronic and antenna component. You also need a runway (with proper lighting and markings) and approach lighting. Other components may be required such as RVR (Runway Visual Range) and Marker Beacons or LPDME. Note on the diagram the more precise the approach is (lower weather minimums) the more ground and airborne equipment may be required.

 

Acquisition Lead:

• ILS-MK20A - Sam Mallipudi
• ILS-420 - Sam Mallipudi