Feature Review: MCDU/FMGS

Hey everyone!

We have had an absolutely incredible response to the announcement of the Fenix Simulations A320 – over 5000 members on our Discord in a little over 24 hours. Needless to say, it’s been a wild week.

We’re going to kick off our feature reviews with a look at our MCDU and its associated functions. This will be quite a dense update, but I hope you guys enjoy this deeper dive into what our airplane can do.

To start with, I will cover the navigation environment our A320 is working with. As initially outlined in our first announcement, the Fenix A320 creates a navigation composite. We do this by utilising ARINC424 data from the Navigraph cycles, along with navaid position data from the same. We then add magnetic variation from WMM2020 code, and of course, the oft spoken about GPS ephemeris data.

The navaid signals mentioned above are then synthesized, meaning we calculate the reception of the signal and use it to provide a blend of audio and static, so if you’re ever flying the Fenix A320 – you may be able to hear VORs at a distance, but you will certainly need to listen very carefully! All stations, if audible, will have a calculated signal reception.

The Fenix A320’s FMGS then uses this technology to calculate its position by gathering multiple position sources and mixing them together to come up with a final best effort location – just like the real aircraft. If you start poking around the depths of the MCDU’s position monitoring page, you will eventually find yourself on a NAVAID selection page which shows you exactly which navigational aids the airplane is automatically tuned to – and should you wish, you may deselect and inhibit certain radio beacons in order to observe the navigational accuracy degrade. You know, just to make sure we weren’t pulling a fast one! The final row on this page also gives you an estimated error value on each IR. The longer and further the aircraft flies, the more these degrade. At the end of each flight in real life, these are checked for degradation outside of a certain tolerance. The Fenix A320 models this degradation accurately – so keep an eye out for this if you like doing turnarounds or multi sector legs, just like they need to do in the real world, or you may find yourself in some trouble.

All this work culminates in an incredibly accurate and reliable navigation environment for our FMGS to take advantage of, ensuring the Fenix A320 always does what you ask of it.

It’s quite difficult to demonstrate relatively simple FMGS functions (like lateral and vertical managed modes) via text – so for a hands on idea of what this will do, you will have to wait until we come to the autoflight feature review, where plenty of media will be shared of the aircraft handling full autoflight. Suffice to say, however, every single autoflight mode is modelled, and complete. You can fly the absolute most complex RNAV/RNP procedures, or if the mood strikes, use the MCDU and FMGS to aid you in flying non-precision (or even visual) approaches. We’ve built this specifically so you can go out and do everything the real A320 does, without worrying about whether or not a specific function is modelled. It’s covered.

ANPOV3A out of Queenstown, New Zealand. Famously a rather convoluted RNP departure. I recommend looking at the chart of it if you can!
A quick look a the FPLN page for the ANPOV3A

For now, we will cover some interesting MCDU functions that will help give you all an idea of quite how extensive the MCDU/FMGS modelling on board our A320 really is.

We will start with a personal favorite, the FLS. We’ve modelled a relatively new Airbus option on board the A320 – the FMS Landing System. The FLS guidance mode is a non-precision approach aid which computes a virtual glideslope and localiser, thereby constructing a “pseudo-beam” by combining Flight Path Angle, approach course, and a selected “anchor point”. From the images provided, you may notice some rather distinctive symbology, unique to this new autoflight mode. The FLS mimics the ILS concept, however, this guidance mode relies only on the onboard navigation sensors, and does not require any additional ground aids. Being able to generate a virtual glideslope and localiser is definitely a fascinating twist on shooting a classic visual approach.

RNAV approach into a visual, aided by the FLS, seen drawn in magenta!
F-LOC, waiting on F-G/S!

RTA (Required Time of Arrival), a common tool in an A320’s substantial arsenal of pilot aids, has also been modelled. This is something those of you who love flying on VATSIM (or just oceanic!), would probably enjoy, as it heightens your immersion and allows you to operate the airplane similarly to how it is truly done in the real world. Whilst RTA may seem like a simple enough system, in reality there is a considerable amount of math involved in making it work correctly. It also has multiple different modes!

For example, should you be sitting on the ground with your engines shut down, preparing to depart – your flight plan page starts with a zero value for time, incrementing it by the minutes and seconds it takes for you to reach your next waypoint, and the successive ones thereafter. Should you choose, however, on the Fenix A320 – you can input an ETT (estimated takeoff time), in which case the MCDU will begin giving you UTC time of arrival for each waypoint. Now, this is amongst RTA’s absolute most basic functions – but diving a little deeper, if you don’t know when you’ll be departing, but know that you must reach your destination at a specific time, you can input this over your destination instead – and the MCDU will not only tell you when you need to depart in order to achieve this, but will also prompt you when you are close to the computed takeoff time in order to let you know that you really must get going, else you risk running late. But, what if you end up running late? Or perhaps leave a little early? Well, RTA will then switch into active mode, take over, and overwrite your cost index – replacing it with a dynamic RTA cost index that will do the math (including the wind speeds!) and figure out how quickly (or slowly) you need to fly in order to reach your destination or selected waypoint exactly when you want to, and appropriately vary managed speed mode. 

The FPLN page before we enter our ETT using RTA
RTA ETT Entered at 1410z
At 1410z, on our taxi out, the MCDU prompts us with a little message – telling us it’s time to get going!
Blasting out of Graz!

One of our technical advisors and alpha team testers, Fraser, a real world A320 pilot, demonstrates this during a oceanic crossing from Dublin to Madeira. Routed via the T9 airway, Fraser receives his oceanic clearance, and has been asked not to cross LASNO before 14:25z.

Into the VERT REV page at LASNO to start setting up the RTA for ATC compliance.. We click LSK2R for RTA.
As you can see, his current ETA is 14:23z with a managed speed of Mach 0.78 on the left hand side. This is no good, as it does not comply with the instructions issued during his oceanic clearance.
Fraser enters his time restriction of 14:25z in LSK1R, and you will notice that the airplane computes his request and managed speed mode reduces his cruise speed to Mach 0.72 to comply with the entry restriction over LASNO.

Touching on ETPs for a quick moment, these are also modelled in the MCDU and are available for you to use. By default, an ETP is generated between departure and arrival airfields. Should you choose, however, you may manually set up an ETP when crossing large spans of water to help aid with your situational awareness.

Another one of our technical advisors and real world A320 pilot, Katie, demonstrates.

Here, she has created an ETP between Cork, Ireland, and Brest, France. As she progresses further south, she would amend these airports to have a relevant ETP for her closest airports as she makes her way across the ocean.
As you can see, after some time, she has updated her ETP to reflect the closest of either Brest, France, or A Coruña, Spain.

RTAs and ETPs may seem rather banal, but it’s just this sort of thing that gives you the final 5% of your experience on board the Fenix A320. The fact that real pilots can jump into our aircraft and begin using these ancillary tools provided by Airbus, to them, the same exact way they do in real life is a testament to the painstaking attention to detail we have lavished on this aircraft.

With the above in mind, step climbs! There isn’t a great deal of hubbub around this – it’s a relatively basic feature on board these flying computers. We’ve included a quick image of a scheduled step climb at position RIPEL – up to FL340. Notice to the right of the entry the time and distance along the route of the planned step climb.

Rapid fire round, coming up.

DATA > CLOSEST AIRPORTS – Very helpful during non-normals and coming up with diversion options. Gives you a bearing, distance and ETA to the airport, and you can also enter a custom airfield in the last line to see where it is relative to you. Clicking on EFOB/WIND will tell you how much fuel you can expect to arrive with and the head/tailwind component for the route there.

FIX INFO “ABEAM” Functionality – Really helpful if there is a portion of the route where the MSA is above FL100 – you can mark where the terrain starts, enabling you a visual representation of which portion of the route would involve a descent to above FL100 in a depressurisation. It can be used for any reason you want, but is often used to raise situational awareness.

Some fancy ND artwork by Fraser, on his Gibraltar approach.

OFFSETS – Used on oceanics, mostly. Nifty thing to play with in your free time during cruise. Just.. ask the controller first, please.

To round this all off, as it’s getting quite dense – I will leave a collection of photos that show some ATSU functions, along with more detail on things like RTAs, ETPs, etc – and more ND route drawings to show how robust our ARINC424 rendering is.

Predictive GPS function, you need to check this if you shoot an RNP arrival or departure. This is where our satellite tracking is used the most!
A random shot blasting out of Hobart – MSFS is unbelievable sometimes..
The RNAV07 – MEBA2H via EHETE into EPKK
Inserting the APP!
One of the most popular questions! Yes, you can uplink directly from SimBrief. Seamless.
And you can grab the weather, too. We’re working on expanding our AOC and ATSU services out, it is still WIP 🙂
10 points to whoever guesses this visual approach (I’m definitely not doing this because I forgot myself..)

I hope we’ve covered enough detail to leave you all satisfied for the time being – you’ll hear from us once again next Friday for the next feature review!

Have a great weekend, everyone!

p.s Come join us on our Discord! We’re super active and answering questions!

p.p.s Big thanks to Katie (she streams here: www.twitch.tv/katiepilot) and Fraser (who does not stream because he is often grumpy) for the images.

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