Hello QNH1013...The current procedure for descent speeds are worked out by the FLOW Controller. He calculates landing times of all arriving acft based on a 100NM ring from VKL. Once this time has been established, he/she will work out the restrictions. Examples wud be like this : MH123 X ISTAN AT XXXXUTC or MH123 speed 270kts. on descent or Cruise and Descend 250kts. All these is done to achieve spacing for the Approach Ctler. Hence when a speed or crossing a waypoint restriction appears on the radar screens, the sector Ctler will abide by it. Remember, these timings are worked out for all Sectors by a single Ctler. While all these are being set, someone arriving from the south or west or north may have done a manouvere which may have resulted in say a minute lost. Hence the sudden decision made by FLOW to now give a descent speed to someone else who was actually told earlier to maintain High Speed. All these decisions are made by the FLOW Controller which every Sector CTler has to follow.This is Radar Procedure. Of course, sector ctlers can also vector out an acft from a normal profile to help out the Apch Ctler. These all depends on real time traffic management. Then again weather plays a part. Drop by my friend at the ACC at Subang. We welcome u with open arms and a good strong handshake.
