Sim/graphics/animation/lights/airplane landing light
RGBA form a 4-part direction vector - see PluginsAndObjects.
X-Plane 921 and newer: RGB form a 3-part direction vector; A is interpreted as an index number for multiple landing light switches.
Alpha is set to brightness or 0 if it's off. RGB is set to white.
This light will turn off if the landing light is off.
This provides a directional light that follows the airplane's landing lights.