Microsoft Flight Simulator, Episode 10 – Aerodynamics

In the latest Feature Discovery series, Sebastian Wloch from Asobo Studio discussed the recent aerodynamic improvements in Microsoft Flight Simulator, the development tools and future improvements.

The aircraft are undergoing continuous improvements with adjustments to the fuel capacity, engine performance and better stability in turbulence.

For ground handling, the braking power and the tyre friction have been adjusted, resulting in more realistic braking distances and ground friction on wet surfaces.

Additionally, the input mapping over the control surfaces has been adjusted for more realistic handling at different speeds, so controlling the aircraft on short final and during flare is easier.

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For the control inputs, an upper dead zone and a reactivity setting has been added to the input sensitivity menu for more realistic handling with different controllers. The amplitude and speed of movement of the control surfaces can now be reduced when moving the yoke, allowing you to be more precise when controlling the aircraft.

Stall physics have been added to the rudder and elevator control surfaces so they can be stalled when applying extreme or sudden inputs. This significantly reduces the aerodynamic forces on these surfaces once they are stalled. The rotation rates and inertia of most aircraft has also been adjusted, including aerobatic types such as the E330 and Pitts Special. Additionally, the negative wing lift simulation and stall has been improved when in inverted flight.

One of the main goals for the new flight model was also to increase the level of realism and to simulate manoeuvres such as stalls, spins, adverse yaw and induced roll.

The air mass over terrain and objects is modelled and represented as updrafts and wind changes caused by heat, mountains, lakes, etc. For example, when the wind blows up a mountain, there is a strong impact on the aircraft's vertical speed. Once over the mountain, the air is very turbulent followed by a downdraft on the leeward side.

In the FSX legacy mode, the flight model is based on a single point, positioned at the centre of the aircraft. It generates one big force and momentum vector that makes the aircraft roll, yaw or pitch based on performance tables in the flight model file.

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In the modern flight model, there are now hundreds of force vectors that affect the flight dynamics of the aircraft. There is a subset of 1,306 vectors and each one has different forces acting on it depending on where it is positioned and how it interacts with the airflow and nearby objects.

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This surface simulation is fully optimised for modern multi-core CPUs and is able to simulate all 1,306 surfaces via a chip system with more than 32 threads and at 100 frames per second in less than 100 milliseconds. This new architecture allowed Asobo to push up the complexity of the simulation by a factor of 1,000.

Airflow accelerated by the engines and propellers is also correctly simulated with propwash and engine effects. This allows for a more accurate simulation of these effects, for example during aerobatics.

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All surfaces have their own aerodynamic simulation in a 3D space.  Surfaces can stall independently from each other, causing stalls and spins if one wing stalls and not the other.

Asobo has added tools to allow aircraft developers to create aircraft directly within the sim and adjust the geometry and surfaces. Parameters can be changed by the click of a button and the results can be seen immediately in the simulator. Sebastian said the authoring tools for the aircraft are being continuously improved.

The propeller performance curve plotting system has been updated and the system to define the propeller performance data has been improved. Aircraft creators can now either use the propeller performance tables or implicit performance curves.

In upcoming updates, the flap definition system is being improved, increasing control over how the flaps surfaces move when they are deployed. Aircraft developers will be able to more accurately specify how the surfaces move forwards or backwards or how the surface angles change when the flaps are deployed. This provides more control over the pitch movement generated by the flaps.

An issue that was causing a lack of performance on twin-engine propeller aircraft at low speed, such as during take-off is currently being fixed. There will also be an update to the aircraft selection menu, enabling users to adjust the limits of the aircraft's control surfaces, fuselage wear and adjust the aircraft's centre of gravity.

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Moving forward, Asobo plans to focus more on turboprop engines, supersonic flight and the interaction of surfaces with supersonic airflow. Developer tools will also be improved to allow a more accurate definition of aircraft surfaces and increase the number of surfaces simulated.