20.
Ground Based Augmentation System (GBAS) Landing System (GLS)

20.1 General
20.1.1 The GLS provides precision navigation guidance for exact alignment and descent of aircraft on approach to a runway. It provides differential augmentation to the Global Navigation Satellite System (GNSS).
20.1.2 LAAS was developed as an “ILS look.alike” system from the pilot perspective. LAAS is based on GPS signals augmented by ground equipment and has been developed to provide GLS precision approaches similar to ILS at airfields.
20.1.3 GLS provides guidance similar to ILS approaches for the final approach segment; portions of the GLS approach prior to and after the final approach segment will be based on Area Navigation (RNAV) or Required Navigation Performance (RNP).
20.1.4 The equipment consists of a GBAS Ground Facility (GGF), four reference stations, a VHF Data Broadcast (VDB) uplink antenna, and an aircraft GBAS receiver.
20.2 Procedure
20.2.1 Pilots will select the five digit GBAS channel number of the associated approach within the Flight Management System (FMS) menu or manually select the five digits (system dependent). Selection of the GBAS channel number also tunes the VDB.
20.2.2 Following procedure selection, confirmation that the correct LAAS procedure is loaded can be accomplished by cross checking the charted Reference Path Indicator (RPI) or approach ID with the cockpit displayed RPI or audio identification of the RPI with Morse Code (for some systems).
20.2.3
The pilot will fly the GLS approach using the same techniques as an ILS, once selected and identified.

21.
Precision Approach Systems Other Than ILS, GLS, and MLS

21.1 General
Approval and use of precision approach systems other than ILS, GLS, and MLS require the issuance of special instrument approach procedures.
21.2 Special Instrument Approach Procedure
21.2.1 Special instrument approach procedures must be issued to the aircraft operator if pilot training, aircraft equipment, and/or aircraft performance is different than published procedures. Special instru-ment approach procedures are not distributed for general public use.  These procedures are issued to an aircraft operator when the conditions for operations approval are satisfied.
21.2.2 General aviation operators requesting ap-proval for special procedures should contact the local Flight Standards District Office to obtain a letter of authorization. Air carrier operators requesting approval for use of special procedures should contact their Certificate Holding District Office for authori-zation through their Operations Specification.

21.3 Transponder Landing System (TLS)
21.3.1 The TLS is designed to provide approach guidance utilizing existing airborne ILS localizer, glide slope, and transponder equipment.
21.3.2 Ground equipment consists of a transponder interrogator, sensor arrays to detect lateral and vertical position, and ILS frequency transmitters. The TLS detects the aircraft’s position by interrogating its transponder. It then broadcasts ILS frequency signals to guide the aircraft along the desired approach path.
21.3.3 TLS instrument approach procedures are designated Special Instrument Approach Procedures. Special aircrew training is required. TLS ground equipment provides approach guidance for only one aircraft at a time. Even though the TLS signal is received using the ILS receiver, no fixed course or glidepath is generated. The concept of operation is very similar to an air traffic controller providing radar vectors, and just as with radar vectors, the guidance is valid only for the intended aircraft. The TLS ground equipment tracks one aircraft, based on its transponder code, and provides correction signals to course and glidepath based on the position of the tracked aircraft. Flying the TLS corrections com-puted for another aircraft will not provide guidance relative to the approach; therefore, aircrews must not use the TLS signal for navigation unless they have received approach clearance and completed the required coordination with the TLS ground equip-ment operator. Navigation fixes based on convention-al NAVAIDs or GPS are provided in the special instrument approach procedure to allow aircrews to verify the TLS guidance.
21.4 Special Category I Differential GPS (SCAT.I DGPS)
21.4.1 The SCAT.I DGPS is designed to provide approach guidance by broadcasting differential correction to GPS.
21.4.2 SCAT.I DGPS procedures require aircraft equipment and pilot training.
21.4.3 Ground equipment consists of GPS receivers and a VHF digital radio transmitter. The SCAT.I DGPS detects the position of GPS satellites relative to GPS receiver equipment and broadcasts differen-tial corrections over the VHF digital radio.
21.4.4
Category I Ground Based Augmentation System (GBAS) will displace SCAT.I DGPS as the public.use service.

22.
Area Navigation
　
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