Good day,
I will try my best to explain.
You are correct in routing directly to ERDAS. Upon entering the Cape Town FIR, an aircraft would be given a clearance for an arrival, in this case “ZS-XYZ route ERDAS for the ERDAS 1A arrival for runway 01”.
With most commercial aircraft these days you are able to program the arrival in to the Flight management computer or GPS. But essentially to fly the arrival procedurally, you would route to ERDAS, then fly towards CTV on the 065 Radial inbound which would mean a course of 245. At 8DME, turn left on to a heading of 190 degrees for radar vectoring for the ILS.
You mentioned the part about routing towards CTV at 6500ft etc. If you see written just above on the plate, it mentions that is part of the communication failure procedure. You would only follow those instructions should your radios fail.
As for the descent profile, that all depends on the type and size of aircraft you are flying. But essentially, approaching from the ERDAS side, and having flown this approach many times, the radar controller will only descend you below 9000ft having past 30DME inbound. Then past that, depending on traffic, you will be descended all the way down to the initial approach altitude of 2000ft while getting vectored for the ILS, where the Final approach fix is at 5.8nm CTI.
I hope that helps!
Last edited by macdaddy2; 25th Jan 2018 at 09:32.