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6/17/21 

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GLS Standard Approach Service Volume 

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20.  Precision Approach Systems other 

than ILS and GLS 

a.  General 

Approval and use of precision approach systems 
other than ILS and GLS require the issuance of 
special instrument approach procedures. 

b.  Special Instrument Approach Procedure 

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. 

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 authoriz-
ation through their Operations Specification. 

c.  Transponder Landing System (TLS) 

1. 

The TLS is designed to provide approach 

guidance utilizing existing airborne ILS localizer, 
glide slope, and transponder equipment. 

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. 

Navigation Aids 

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