ANPC’s technology uses transponder multilateration with ground-based sensors to track an aircraft’s precise location in vertical position (elevation), horizontal position (azimuth), and range, with very high accuracy. This is done by measuring the arrival time and phase of radio signals transmitted from the aircraft’s radar beacon transponder. The transponder is the same device used by Air Traffic Control radar systems to track aircraft during flight, and every aircraft equipped to fly in Instrument Meteorological Conditions (IMC) must have one installed. TLS is compatible with transponder Modes 3/A, Mode C, Mode S and Mode 5.
The guidance appears to the pilot as needle movements on the ILS course deviation indicator in the cockpit that are identical to an ILS and can be flown down to the minimum descent altitude.
The TLS is a ground-based system designed to provide precision approach guidance utilizing the aircraft ILS localizer, glide slope, and transponder equipment.
TLS ground equipment consists of a secondary surveillance interrogator, sensor arrays to detect aircraft lateral and vertical position, and UHF/VHF guidance transmitters. The TLS detects all aircraft within the service volume by interrogating Mode-A/C transponders. After ATC clears an aircraft for TLS approach, the pilot must tune and identify the TLS localizer frequency on the approach plate that matches the approach clearance just as they would with a traditional ILS. TLS broadcasts RF signals to the aircraft ILS equipment to provide Category I approach. The pilot will not observe any difference in needle movement from a traditional ILS approach.
Approach guidance on the TLS frequency pair is valid for one aircraft cleared by ATC for the approach.The TLS can be purchased in a four transmitter configuration for guidance to four aircraft at a time.
The TLS ground equipment tracks aircraft based on their transponder code and provides localizer course and glide path based on the position of the tracked aircraft. Navigation fixes based on conventional NAVAIDs or GPS are provided in the instrument approach procedure for crosscheck.
The aircraft position can also be displayed on ground console with a format matching a Precision Approach Radar display for use in Ground Controlled Approach operations.
The approach path is configured using virtual point technology. The TLS can inherently support offset and non-linear approach procedures where a straight-in approach is not feasible due to noise abatement or obstacle clearance issues. The approach profile for TLS is not a function of alignment between the approach path and antennas like a traditional ILS that radiates the signal without tracking the aircraft position.
Virtual point technology also allows the TLS to provide localizer signal that complies with ICAO tolerances regardless of the runway length or obstacles at the end of the runway. TLS can be configured for the standard 700 foot tailored width at threshold with 6 degree course width from the normal TLS equipment siting near the approach end of the runway. This is a configuration file setting available to the TLS technician.
ANPC delivers TLS technology in several product packages that all use the same core software and electronics. The product package is the only difference in how the system is transported for the following product lines: Rhino, Firefly, ANPC D-ILS, TLS and TTLS.