I would like to request the addition of GLS (GBAS Landing System) approach support in the sims. I think it might be unlikely to have it in 2020 due to it being later in it’s lifespan, but this should be an addition in 2024 as it is only in the first year of it’s long lifespan. Nevertheless, it would be great if 2020 could benefit from this too.
GLS is a modern precision approach system that is increasingly implemented in airports, as there has been a shift away from ILS approaches towards other approach types that are more flexible in the approach paths.
Currently, MSFS does not support GLS procedures natively in the flight planner, avionics, or navdata - even at airports where they exist in the real world (e.g., Frankfurt EDDF, Sydney YSSY, Newark KEWR). Currently, third-party aircraft usually spoof the approach by using third-party data and converting it into a GPS-type approach instead. The MMR in the Asobo 737 Max would also benefit from the addition of these modern approaches too.
I understand supporting GLS approaches would require some base sim updates such as (could be an incomplete list):
Adding the concept of GBAS emitters to allow for better tracking against the sim scenery layer,
Shipping the LIDO navdata with GLS approaches, and
Adding support for GLS to the relevant avionics suites in the sim.
As a premium flight simulation tool, I think it is important for MSFS2024 to try and keep up with the developments in the aviation sector, positioning itself as a leader in the flight simulation sector. This could also extend to other approach types that would also benefit from native support in the base simulator to avoid the need to spoof the approach type in third-party aircraft.
Thank you for your continued development of the sim, and I hope to see more of the good work done by the team. I hope this could be seriously considered for a future sim update.
We looked at this deeply for MSFS 2024, but right now the main reason that almost no simulations support GLS is that the worldwide ARINC for GLS is woefully incomplete. The reason for this is because the ground transmitters transmit the GLS path points to the receiver in the plane, there is no need for the data to be in the FMS. The only thing the FMS knows about is the station itself, but having that only makes it impossible to know what the GLS path points that will be transmitted are.
The majority of the holdup here is not at the data provider level, but at the national AIP level. Nations and aerodromes are mostly not publishing this data yet for inclusion in the AIP (which is the source of ARINC data ultimately). It’s not a problem just for our simulator, but for professional simulators as well up to the highest level, which is why it has been requested by sim makers for the data to be published.
Ultimately we and everyone else are at the mercy of the various aerodromes’ AIPs and until more data is published it won’t really be possible to implement GLS.
It’s spoofed in more ways than just that, most likely. You don’t really need the sim to support GLS at all at the base for your avionics to support it; most of our avionics in the sim don’t use the MSFS GPS system at all nor its base LNAV, for example. Really the limiting factor is how few GLS path points are actually published compared to the number of approaches that exist. We could fake it for marketing points but that doesn’t feel like what simmers want.
Once the data matures, we definitely want to tackle this in a wholesale way, but we expect that will probably still be a year or two off at least until it reaches that state.
Thanks for the detailed background on the situation. It’s very heartening that it was looked at deeply, and I hope there could be some progress in the future too.
I understand there isn’t much that can be done if national AIPs are excluding the data. But are the few countries that are publishing the data (if any) being included at the data provider level? I think a good first step might be to consider having the ball rolling with the subset of data that is available to see how it can be integrated with the existing aircraft.
I understand that aircraft do not need the sim to support GLS at the base level, but I see the navdata as part of what the base sim provides as well. If the GLS path is provided as part of the sim data, then more aircraft could tap into that as a reliable data source.
My limited understanding is that the GBAS ground emitter also provides some service of possibly “calibrating” and providing additional accuracy compared to satellite GPS? Would that correction factor be something that the base sim would be responsible for? Considering the sim occasionally runs into scenery “drift” issues over time as the magvars get updated but the scenery (specifically handcrafted airports) might not be updated in a timely fashion. It was in my mind that is something the base sim would be responsible for simulating, as the emitters could be aligned to core airport features.
It’s a very very small subset. We could technically include it but it would be confusing for users, as the majority of GLS approaches that would be in the data would have no path points in the data. So they could be selected but not flown.
The GPS aircraft position in the sim is always 100% accurate to your actual aircraft position in the sim, so there could not be any increase in positional accuracy.
GLS is not really at all like ILS, despite the similar names. The ground transmitter does not guide the plane in via any kind of beam, so the position of the transmitter on the ground is just wherever they found space to install it. It isn’t referenced to any airport features; instead the ground station sends both the GPS correction data and the lat/lon/altitude points the aircraft is to fly through. But the ground station doesn’t track your aircraft or tell it how far off from the path the aircraft is. Instead, just like SBAS, the avionics use GPS to fly through the transmitted path points.
The ground station is just there to increase the accuracy of the GPS solution (already perfect in the sim) and give you the path points (the data that is mostly missing from the AIPs).
Hopefully all of that helps explain why we are opting to wait.
Fully understand the reason for waiting. Hopefully, the situation will change within the 2024 lifecycle, and it could be added later on. I know it might be too much work to filter out the GLS approaches that do not have path points in the data and only include the ones that do too. Maybe things would improve next year.
I was under the impression there might be room to enhance the GPS signal simulation with the inclusion of ground transmitters but that might complicate things too much for some devs that don’t necessarily want to deal with it.
Looks like it’s just a waiting game for the path points data situation to be changed. Hope to see this kept on the MSFS radar and thanks to you and your team for the great work so far on the avionics and navdata!