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Precision Approach Guidance
The TLS from ANPC is a transponder-based Instrument Landing System designed to provide precision approach capability at airports with terrain or real estate constraints that render common ILS systems infeasible or cost-prohibitive. The TLS is fully compliant with ICAO and FAA requirements for a Category I ILS, but its underlying architecture is quite different and offers unique benefits that no other system can offer.
Traditional ILS systems are passive in that there is no 2-way communication between the aircraft and the landing system. An onboard ILS receiver simply compares the aircraft’s current position with static signals from antennas aligned with the desired localizer and glideslope course for the approach, and corrections are displayed on an HSI or CDI console in the cockpit. The pilot can then “fly the needles” to the prescribed decision height at which the runway environment must be in view to execute the landing.
The TLS is at its core a highly accurate secondary surveillance system that uses multilateration to track the precise location of all aircraft within 100nm of an airfield,. This location data is then converted into guidance for an aircraft that has been cleared for and tuned to the TLS approach. Because the TLS knows the precise location of both the aircraft and the would-be location of standard ILS transmitters, it’s able to provide precision approach guidance to the desired touch-down point without reliance on the actual placement of the transmitting antennas.
We call this “Virtual Point Technology” and it allows us to guide aircraft based on a virtual emanation point that cannot physically accommodate an antenna array. Such situations include runways that are short, have sloping terrain or obstacles adjacent to or underneath the approach path, or lack the real estate required to install antennas and marker beacons at the end of the runway. Additionally, traditional ILS localizer performance can be diminished by multipath interference from moving or stationary objects located at the airport, and restrictions to aircraft and vehicular movements can significantly reduce airport throughput when critical area protective measures are in effect.
The TLS occupies a small operational footprint of roughly 70 to 100 square meters and can be flexibly sited adjacent to or astride the runway threshold with minimal ground conditioning or other civil works.
To the pilot, the TLS is identical to any other ILS and requires no additional onboard equipment or pilot training, and all IFR-equipped aircraft have the necessary avionics to fly a TLS approach. Because TLS guidance is controlled in software, it can support multiple and varying approach paths including offset and segmented approaches, steeper glideslope angles for rotary-wing aircraft, and approaches to small landing areas such as offshore drilling platforms and helipads on buildings or ships. No other system in the world has this flexibility.
TLS technology is the backbone of all ANPC surveillance and navigation systems including those designed for airspace awareness and rapid deployment applications.
The TLS has been granted system design approval by the FAA, and complies with all ICAO specifications for a CAT. I ILS as well as RTCA DO-178B reliability standard for airborne software and the SAE ARP 4754 certification model for highly-integrated or complex aircraft systems.
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