Fenix Simulations recently published an in-depth blog post about their upcoming A319/A321 expansion package for Microsoft Flight Simulator, covering historical bits, differences, catches, flight model changes, and more.

The first few paragraphs explain why the Airbus A320 came to be and who it was trying to compete against. They then eventually delve into the length differences of each airframe and the many challenges encountered during development, spanning from wingspan to engine thrust and even noise restrictions. 

From there onwards, they also went on in detail about the flight model differences between both, with the A321 suffering to slow down and the A319 slowing down far too much, and how that differs from what one would expect based on their experience flying the A320. 

The differences don’t stop there, though, with the A321 demanding an entirely different landing technique due to its weight and length, significantly increasing the risk of a tailstrike in case of an overflare, and the A319 being the exact opposite due to its 13.5-degree tailstrike clearance. 

While the A319 and A320 share the same fuel system, the A321 has an entirely different layout, using a single, large tank per wing instead of the split-wing design on the smaller siblings. The electrical center tank pumps were replaced by transfer jet pumps, using motive flow to extract fuel from the center tank and move it to the wing tanks. Such a difference makes it so the fuel logic is far from being the same, which they exemplify in a pretend failure scenario, with the A321 being able to have its pumps working - gravitationally -  even in case of an electrical supply failure, whereas the A319/A320 would not.

The ECAM, which is the central nervous system of a modern Airbus, is also objectively different across the variants. Fenix has gone through extensive documentation to ensure accurate ECAM behavior with every possible variant, as certain combinations are exclusive to each type.

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The ELAC (Elevator and Aileron Computer), SEC (Spoiler and Elevator Computers), and FAC (Flight Augmentation Computers) were also altered for A319/A321 conformity, as they are also intrinsically different.

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Their cabin announcement system was changed to support the upcoming expansion, making type-specific cabin announcements possible.

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Fenix has also fed their systems with new data, warranting accurate green dot, VLS computation, and performance application updates to provide proper takeoff and landing distance calculations.

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Each airframe will accompany its own GSX profile, ensuring compatibility with FSDT’s Ground Service X from day one.

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The flight model has undergone massive changes, with a rewritten control translation system that is faster, more performant, and more accurate, running literally 100x faster than before. The “delay” on control input that many users complained about is now a thing of the past. That tweak led them to retune the fly-by-wire logic entirely, with changes to the Alpha Protection PIDs, a complete autopilot rework, and some of the code had to be altered to accommodate the new changes. When flying the aircraft by hand, the outcome is a more natural, direct, and “connected” feel.

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Their flare logic has also been given attention, with the ground effect completely externalized. This gives Fenix Simulations full control over the landing dynamics, ensuring the aircraft’s behavior on the landing and flare portion is closer to the actual thing.

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They highlight that the handling upgrades will also be made available for the A320 on launch day instead of an open-ended promise to back-port the new features “eventually.” 

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The new engines will also follow their XEM (external engine model) system, with all airframes having unique engine variants and thrust ratings. The A319 will feature the CFM56-5B6 engines for the -112 variant and the IAE V2524-A5 SelectOne for the -132. The A321, on the other hand, will feature the CFM56-5B2 engines for the -213 variant and the IAE V2533-A5 SelectOne for the -231.

Their new flight model was built on hundreds of hours of telemetry data fed by their beta team and then compared with real-world performance data, yielding a “wonderfully accurate” result with convincing drag, lift, thrust, flap settings, geometry, fuel flow, ground handling, and gyroscopic precision. 

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They have also solved an issue where their Airbus would lose stability when fully configured and flying close to VLS, often “dropping a wing.” That has since been addressed, and one should be able to fly an extremely heavy A321 fully configured in a tight visual circuit without having a wing drop anymore. These improvements will also be applied to the A320 on launch day.

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There’s no information about the release date yet, but their next development update will showcase some new liveries for the upcoming birds.

Stay tuned to Threshold for more flight simulation news!

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