Thanks HD for the reply. So the Directors juggle the speeds and altitudes to maintain a sequence, then convey that information by voice RTF to the aircraft. What I am wondering is, is there a telemetry link, such as ACARS, that keeps the aircrews informed of the required airspeeds and altitudes... ( Much the same as in Formula 1, where drivers have a 'Delta' to follow so they are on schedule for a fast lap.)
I was thinking that any information sent by telemetry, would reduce the amount of voice transmissions required. However I realise this could create a clash, if the telemetry said one thing and the Director said another.
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