Widebody; Low Wing; 3 Turbojet Eng
Flight Crew Air Transport Pilot (ATP)
Communication Breakdown; Confusion; Human-Machine Interface; Situational Awareness; Workload
ATC Issue All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert; Air Traffic Control Issued New Clearance; Flight Crew Returned To Clearance
Airport; Human Factors; Procedure
Airport using runways 20L & 20R for landing. The Controller was very busy. No arrival given to us until past IGONO; our last fix on our FPL. They gave us IGONO 1X RNAV arrival after we had passed IGONO. I had loaded the IGONO 1X arrival which puts [aircraft] on the same course as the Y arrival. So already we were behind the curve; and luck would have it that we were on course after the First Officer loaded the new arrival. Numerous aircraft landing ZGGG; frequency congested. About 30 miles out; we were given a heading of 190 to intercept the localizer on 20R; (the Controller turned us right at the course line) I selected 190; and the localizer needle was showing an off flag and very erratic; but close to centered. I immediately selected my pre-tuned frequency for 20R and armed the localizer; and asked the First Officer if he had an off flag; and he said he did. Immediately the off flag went away; and were drifting north of course; (as confirmed by the magenta line). I turned another 10 degrees left to re-intercept; and we got localizer alive and the autopilot turned to intercept the localizer. In the meantime; there were numerous speed and altitude; frequency changes; so the First Officer was very busy. We were cleared for the ILS now; about 18 miles out so I pressed approach/land. Next thing I know the autopilot had us drifting south of course; then ATC instructed us to turn right to re-intercept the localizer again. The reason the FMS never autotuned the ILS was because we got intercept instructions and clearance about 28 miles from the field. We re-intercepted 20R and landed uneventfully.This was very confusing from the beginning of the arrival. We asked for an arrival and runway earlier on the other side of IGONO; and we received no answer other than a frequency change. Numerous aircraft landing and using different runways. We received our runway information and arrival after passing the first fix on the arrival. I have been to ZGGG numerous times in the past; I was aware of how late clearances are assigned; but this was the worst I had seen. Obviously; we got off course; I could have done a better job monitoring the autopilot; but the scenario was very challenging with all the altitude assignments and airspeed changes; all within an area of about 10 miles. Just to mention; the First Officer was very busy putting an arrival in after we passed the fix; and had his hands full with all the frequency changes in a short period of time.
A widebody inbound to ZGGG from the northeast and cleared for the ILS to Runway 20R was unable to receive the localizer and deviated from course.  ATC provided ameliorative handling.