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Instrument Rating

Instrument Approach Systems – Other

Navigation Systems

Simplified Directional Facility (SDF) The SDF provides a final approach course similar to the ILS localizer. The SDF course may or may not be aligned with the runway and the course may be wider than a standard ILS localizer, resulting in less precision. Usable off-course indications are limited to 35° either side of the course […]

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Instrument Approach Systems – ILS Errors

Navigation Systems

The ILS and its components are subject to certain errors, which are listed below. Localizer and GS signals are subject to the same type of bounce from hard objects as space waves. Reflection. Surface vehicles and even other aircraft flying below 5,000 feet above ground level (AGL) may disturb the signal for aircraft on the […]

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Instrument Approach Systems – ILS Function

Navigation Systems

The localizer needle indicates, by deflection, whether the aircraft is right or left of the localizer centerline, regardless of the position or heading of the aircraft. Rotating the OBS has no effect on the operation of the localizer needle, although it is useful to rotate the OBS to put the LOC inbound course under the […]

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Instrument Approach Systems – Approach Lighting Systems (ALS)

Navigation Systems

Normal approach and letdown on the ILS is divided into two distinct stages: the instrument approach stage using only radio guidance, and the visual stage, when visual contact with the ground runway environment is necessary for accuracy and safety. The most critical period of an instrument approach, particularly during low ceiling/visibility conditions, is the point […]

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Instrument Approach Systems – Instrument Landing Systems (ILS)

Navigation Systems

The ILS system provides both course and altitude guidance to a specific runway. The ILS system is used to execute a precision instrument approach procedure or precision approach. [Figure 7-34] The system consists of the following components: A localizer providing horizontal (left/right) guidance along the extended centerline of the runway. A glide slope (GS) providing […]

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Inertial Navigation System (INS)

Navigation Systems

Inertial Navigation System (INS) is a system that navigates precisely without any input from outside of the aircraft. It is fully self-contained. The INS is initialized by the pilot, who enters into the system the exact location of the aircraft on the ground before the flight. The INS is also programmed with WPs along the […]

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Local Area Augmentation System (LAAS)

Navigation Systems

LAAS is a ground-based augmentation system which uses a GPS reference facility located on or in the vicinity of the airport being serviced. This facility has a reference receiver that measures GPS satellite pseudo-range and timing and retransmits the signal. Aircraft landing at LAAS-equipped airports are able to conduct approaches to Category I level and […]

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Wide Area Augmentation System (WAAS)

Navigation Systems

The WAAS is designed to improve the accuracy, integrity, and availability of GPS signals. WAAS allows GPS to be used, as the aviation navigation system, from takeoff through Category I precision approaches. The International Civil Aviation Organization (ICAO) has defined Standards for satellite-based augmentation systems (SBAS), and Japan and Europe are building similar systems that […]

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Differential Global Positioning Systems (DGPS)

Navigation Systems

Differential global positioning systems (DGPS) are designed to improve the accuracy of global navigation satellite systems (GNSS) by measuring changes in variables to provide satellite positioning corrections. Because multiple receivers receiving the same set of satellites produce similar errors, a reference receiver placed at a known location can compute its theoretical position accurately and can […]

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