ILS

From HFUnderground

Instrument Landing System, the "NAV" part of the VHF aircraft band "NAV/COM" 108-137 MHz band. NAV is 108.0 MHz to 117.95 MHz. VHF navigation band is shared between the localizer portion of ILS and the VOR system.

VHF/UHF based landing beacon system designed to provide vertical (height, or altitude) guidance (glideslope - a beam that the aircraft can follow or "ride" down to the runway, following the glideslope indications (if the aircraft is too high, too low or on track to land) and horizontal guidance (localizer) (if the aircraft is to the left of the runway centerline, to the right of the runway centerline, or aligned with the runway) as well as positional guidance (markers - indicating to the pilot his location in relation to the runway threshold).

All of these services are considered radionavigation or radiodetermination services. They operate as aircraft radio navigation beacons and permit navigation in poor weather or at night. Development of these various systems dates back to the 1920s and 1930s, with the development of the low frequency radio range (LFRR) - referred to as just the range, the VHF low band Lorez blind landing beam system or "Lorenz Beam" (which operated in the 30-33 MHz band) and other similar systems.

The onset of World War II spurred the development of radar as well as numerous short-range and long-range radio navigation beacon and beam systems for bombing, including hyperbolic navigation (the beginnings of what would become the LORAN and LORAN-C systems), single-beacon and transponder based systems (which functioned the same way as the modern DME system), blind landing systems, etc. The "Battle of the Beams" focused mainly on the RAF and the Luftwaffe developing competing systems and countermeasures for those systems.

Aeronautical radionavigation service, usually considered a fixed service.

The ILS is very gradually being supplanted in day to day use by GPS (SATNAV or RNAV) based systems, but is maintained (along with the VOR system) as a backup and secondary navigational tool.

-Will be updated at a later date, see also:

• VOR
• VHF airband
• HF airband and MWARA
• NDB
• DME

ILS frequencies:

• Marker beacons: 75.000 MHz (75 MHz)
• Localizer: 108.100 MHz - 111.950 MHz VHF nav sub band 108 - 117.95 MHz (shared with VOR stations, see list below)
• Glideslope: 329.150 MHz - 335.000 MHz UHF - part of the 225-400 MHz military UHF aircraft band

• Localizer / Glide slope frequency pairs:

Note how the UHF glideslope (glidepath) frequency is never the third harmonic of the VHF localizer frequency.

• 108.10 MHz / 334.70 MHz
• 108.15 MHz / 335.55 MHz
• 108.30 MHz / 334.10 MHz
• 108.35 MHz / 333.95 MHz
• 108.50 MHz / 329.90 MHz
• 108.55 MHz / 329.75 MHz
• 108.70 MHz / 330.50 MHz
• 108.75 MHz / 330.75 MHz
• 108.90 MHz / 329.30 MHz
• 108.95 MHz / 329.15 MHz
• 109.10 MHz / 331.40 MHz
• 109.15 MHz / 331.25 MHz
• 109.30 MHz / 332.00 MHz
• 109.35 MHz / 331.85 MHz
• 109.50 MHz / 332.60 MHz
• 109.55 MHz / 332.45 MHz
• 109.70 MHz / 333.20 MHz
• 109.75 MHz / 333.05 MHz
• 109.90 MHz / 333.80 MHz
• 109.95 MHz / 333.65 MHz
• 110.10 MHz / 334.40 MHz
• 110.15 MHz / 334.25 MHz
• 110.30 MHz / 335.00 MHz
• 110.35 MHz / 334.85 MHz
• 110.50 MHz / 329.60 MHz
• 110.55 MHz / 329.45 MHz
• 110.70 MHz / 330.20 MHz
• 110.75 MHz / 330.05 MHz
• 110.90 MHz / 330.80 MHz
• 110.95 MHz / 330.65 MHz
• 111.10 MHz / 331.70 MHz
• 111.15 MHz / 331.55 MHz
• 111.30 MHz / 332.30 MHz
• 111.35 MHz / 332.15 MHz
• 111.50 MHz / 332.90 MHz
• 111.55 MHz / 332.75 MHz
• 111.70 MHz / 333.50 MHz
• 111.75 MHz / 333.35 MHz
• 111.90 MHz / 331.10 MHz
• 111.95 MHz / 330.95 MHz