01/09/2024
Further Discussion About FLS APPR
Airbus Strategy for Straight-In approaches ILS, GLS (GBAS Landing System), SLS (Satellite Landing System) and now also FLS?
Airbus target (as example in our case) was to standardize the way of flying all approaches down to the published approach minima, whatever the airport, and whatever the equipment on the ground are.
The FLS (FMS Landing System) is part of that concept and today, it is an Airbus option offering a solution to fly 99% of approaches that are not ILS/MLS, with a barometric vertical profile. It offers lateral and vertical guidance for a straight-in instrument approach, referenced from the aircraft position, along a trajectory retrieved from the FMS navigation database.
In fact FLS replicates the ILS beam concept, but using only the onboard navigation sensors with no need for additional ground aids. The FMS constructs a “pseudo beam” which has an anchor point on RWY, approach course and Flight Path Angle (FPA), and which overlays the final segment of an instrument approach with a temperature compensation on final segment for the indicated altitude. (See FLs beam image) FLS approaches can be loaded from the FMS database like any other approach. The approach is selected and executed similarly to an ILS approach, but it does not require tuning a specific frequency since it’s an onboard-generated system.
For not making mistakes between ILS and FLS, crew must train a distinctive symbology for the non-precision approach flown with FLS ! (See FLS on PFD image)
Combining RNP AR with FLS offers an additional layer of safety, particularly in low-visibility conditions or when approaching airports with complex terrain. The enhanced precision reduces the likelihood of deviations from the intended flight path and ensures a stabilized approach, which is critical for safe landings.
So why is FLS APPR so important? It is especially useful for approaches to runways that do not have traditional ILS, providing a higher level of precision than standard non-precision approaches (such as VOR or NDB approaches). During an RNP AR approach, the FMS handles the lateral navigation based on the RNP AR procedure, while the FLS system provides vertical guidance. The FLS generates a virtual glide path that the autopilot or pilot can follow, ensuring a continuous and stabilized descent to the runway.
I prefer to simulate commercial flights in XP12 with ToLiss Airbus airliners because they are designed with high-fidelity systems that accurately simulate real-world Airbus operations, including advanced approach capabilities like FLS.
I know that Boeing has a similar capability known as the Integrated Approach Navigation (IAN) system, which is akin to Airbus's FMS Landing System (FLS), but I don't know if XP12 Boeing models have this capabilities. The IAN system allows Boeing aircraft to fly precision-like approaches using the aircraft's Flight Management System (FMS) and onboard navigation data, without relying on traditional ground-based navigation aids like the Instrument Landing System (ILS).
User with FLS/IAN experience are invited to discuss about and to present such approaches...