Starting with X-Plane 12, traffic injected into X-Plane using the TCAS datarefs casts wake turbulence that interacts with the user airplane. For your traffic to generate wake turbulence, your plugin must use the APIs introduced with X-Plane 11.50. If you haven’t already done so, read up on XPLMInstance on how to draw your traffic models in X-Plane in a Vulkan-compatible manner, and read about the TCAS API on how to tell X-Plane the state of your traffic targets.

New Datarefs to influence wake generation

By default, a traffic target will generate the wake appropriate for a small business jet, an aircraft weighing about 10 tons and having a wing span of about 12 meters. This will cause upset if the user flies into it with a C172 or other light plane, but will not cause a lot of disturbance if the user is flying an airliner. This is to minimize possible user frustration if dealing with a plugin that does not update X-Plane about the finer details of wake generation. If the plugin however supplies more information about the traffic it provides, X-Plane can fine tune the wake generation to be more appropriate for the exact type of traffic that is displayed. Keep in mind that wakes are strongest if the aircraft is slow, clean, and high AoA. X-Plane uses the lift force generated by the wing to determine the strength of the wake, and takes AoA into account that was used to generate that lift. With lower speed a higher AoA is needed to generate the same lift force, which causes a stronger wake. On the other hand, with flaps a lower AoA is needed to generate the same lift force, which causes a weaker wake.

sim/cockpit2/tcas/targets/wake/wing_span_m	float[64]	y	meter	wing span of the aircraft creating wake turbulence
sim/cockpit2/tcas/targets/wake/wing_area_m2	float[64]	y	meter	wing area (total area of both wings combined) of the aircraft creating wake turbulence
sim/cockpit2/tcas/targets/wake/wake_cat	int[64]	y	enum	wake category of the aircraft. This is for information purposes only and is not used to calculate the actual strength of the turbulence. 0 = Light, 1 = Medium, 2 = Heavy, 3 = Super
sim/cockpit2/tcas/targets/wake/mass_kg	float[64]	y	kg	actual mass of the aircraft creating the wake
sim/cockpit2/tcas/targets/wake/aoa	float[64]	y	degrees	angle of attack of the wing creating the wake
sim/cockpit2/tcas/targets/wake/lift_N	float[64]	y	Newton	instantaneous lift force of the whole wing generated right now, in Newtons

Wake reset

If a target moves by more than 200 meters in one frame (i.e. the 3d distance of the sim/cockpit2/tcas/targets/position/{x,y,z} triplet between two frames is greater than 200 meters) its wake is immediately cleared and reset. This is to avoid leaving a wake trail in space if a new aircraft is represented by the same TCAS slot and the target moves to a different point in space to represent a different aircraft.