Top two panels: modeled variations of the knot’s ejection position angle with its ejection time and the modeled relation between the ejection position angle vs. its ejection viewing angle. Bottom two panels: observed variations of the knot’s ejection position angle with ejection time and the observed distribution of the knot’s ejection position angle vs. its ejection viewing angle. The curves and the quantities are calculated by using the precession jet nozzle model for core separation r_n = 0.15 mas. The viewing angle ranges from 1.22° to 1.48° (jet-A) and from 1.17° to 1.76° (jet-B).