My question relates to speed control.
An aircraft like the A330 begins descent very early, then generally flies much slower (groundspeed) through the mid levels FL200- 10,000'. But every now and then you'll get one that behaves like a 'normal' plane. Who or what decides this profile? Obviously the crew can alter what the FMS is doing, but how is the descent profile calculation done? Is it active, different for each flight (considering wx, weight etc), or simply passive- a design thing? For a given miles-to run, the A330 is usually about 10,000' lower than other types (B777, A310, B747), making sequencing harder because of the groundspeed differential.