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Instrument Landing Systems
The TLS is an 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. Onboard ILS receivers simply compare the aircraft’s current position with static signals from antennas aligned with the desired localizer and glideslope course for the approach, and display corrections 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 tracks the precise location of all aircraft within 120nm of an airfield, with an unprecedented update rate of 22Hz. This location data is then converted into guidance for an aircraft that has been cleared for and tuned to the ILS 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 and/or have sloping terrain or obstacles adjacent to or underneath the approach path, or those without the real estate required to install antennas and marker beacons on either end of the runway. Additionally, traditional ILS localizer performance can be diminished by multipath (RF reflections) from large buildings located on the airport property, and restrictions to aircraft and vehicular movements can significantly reduce airport throughput when critical area protective measures are in effect. The majority of the world’s airports have such limitations.
The TLS was designed to alleviate these problems by providing a virtual approach path, compensating for multipath and minimizing the equipment footprint, which can be adjacent to or astride the approach end of any runway.
To the pilot and operators, the TLS is identical to any other ILS and requires no additional avionics or pilot training. All IFR-equipped aircraft have the necessary avionics to fly an ILS and therefore a TLS approach. It’s designed to be installed at any airport that can support an approved Instrument Approach Procedure, without extensive ground conditioning or other civil works. The TLS is also capable of supporting multiple and varying approach paths including offset and segmented approaches, steeper glideslope angles for rotary-wing aircraft, and approaches to offshore oil rig drilling platforms. No other system in the world has this flexibility.
The Federal Aviation Administration has granted the TLS regulatory approval, and the TLS complies with the 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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