Instrument Landing System
The Instrument Landing System
Up to now, your instrument approach experience has allowed you to land in weather conditions as adverse as an overcast ceiling of 400 ft. and visibility as low as one-half mile.
NDB and VOR approaches, with their lateral guidance to the runway, greatly improve the reliability of flight schedules. But without the capability to provide vertical guidance to the runway they are limited in utility. No vertical guidance classes them as non-precision approaches.
The Instrument Landing System adds glide-slope, or elevation information. Commonly called the ILS, it is the granddaddy of them all when it comes to getting down close to the ground. In every sense it is a precision approach system and with the most sophisticated equipment it can guide you right down to the runway—zero Decision-Height and zero visibility.
If you jumped to this point of the website without proceeding through the earlier sections, I strongly recommend that you return to the Air Navigation section and review the sections on VFR Sectional Charts, IFR enroute low altitude charts, and the basics of plotting a course. Further, you should go to the NDB Approaches/Approach Platessection and read the basics of Instrument Approach Plates, now called Terminal Procedures.
The ILS Components
When you fly the ILS, you're really following two signals: a localizer for lateral guidance (VHF); and a glide slope for vertical guidance (UHF). When you tune your Nav. receiver to a localizer frequency a second receiver, the glide-slope receiver, is automatically tuned to its proper frequency. The pairing is automatic.
There's more to an ILS than the localizer and glide slope signals. The FAA categorizes the components this way:
Guidance information: the localizer and glide slope.
Range information: the outer marker (OM) and the middle marker (MM) beacons.
Visual information: approach lights, touchdown and centerline lights, runway lights.
Descriptions of the ILS components
Up to now, your instrument approach experience has allowed you to land in weather conditions as adverse as an overcast ceiling of 400 ft. and visibility as low as one-half mile.
NDB and VOR approaches, with their lateral guidance to the runway, greatly improve the reliability of flight schedules. But without the capability to provide vertical guidance to the runway they are limited in utility. No vertical guidance classes them as non-precision approaches.
The Instrument Landing System adds glide-slope, or elevation information. Commonly called the ILS, it is the granddaddy of them all when it comes to getting down close to the ground. In every sense it is a precision approach system and with the most sophisticated equipment it can guide you right down to the runway—zero Decision-Height and zero visibility.
If you jumped to this point of the website without proceeding through the earlier sections, I strongly recommend that you return to the Air Navigation section and review the sections on VFR Sectional Charts, IFR enroute low altitude charts, and the basics of plotting a course. Further, you should go to the NDB Approaches/Approach Platessection and read the basics of Instrument Approach Plates, now called Terminal Procedures.
The ILS Components
When you fly the ILS, you're really following two signals: a localizer for lateral guidance (VHF); and a glide slope for vertical guidance (UHF). When you tune your Nav. receiver to a localizer frequency a second receiver, the glide-slope receiver, is automatically tuned to its proper frequency. The pairing is automatic.
There's more to an ILS than the localizer and glide slope signals. The FAA categorizes the components this way:
Guidance information: the localizer and glide slope.
Range information: the outer marker (OM) and the middle marker (MM) beacons.
Visual information: approach lights, touchdown and centerline lights, runway lights.
Descriptions of the ILS components