FIG 1 − 1 − 8 GLS Standard Approach Service Volume AIM 3/15/07 1/30/20 8/15/19  7110.65R CHG 2 AIM 12/31/20 1 − 1 − 20. Precision Approach Systems other than ILS and GLS a. General b. Special Instrument Approach Procedure c. Transponder Landing System (TLS) 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. Approval and use of precision approach systems other than ILS and GLS require the issuance of special instrument approach procedures. 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. 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. 1 − 1 − 37 Navigation Aids