Sim/graphics/animation/lights/airplane landing light flash
RGB form a 3-part normalized direction vector - see PluginsAndObjects.
A is the index of the landing light number.
Alpha is set to 1.0 or 0 if it's off. RGB is set to white.
The size of the light is modulated based on the view angle.
This light will turn off if the landing light is off.
This provides another directional landing light, except the light will "flash" - that is, it grows bigger with view angle rather than more opaque.