Control of Aircraft — Page 340, Lesson 448

I want to walk you through what happens to an aircraft the moment it departs — because that's exactly what this part of the book covers. We're looking at the control of departing aircraft, and the rules here are precise, so let's take them one by one. First, paragraph 17.28. When air traffic control is based on clearances — that is, when the control of traffic is built around an air traffic control clearance — that clearance has to specify certain things. Think of this as the legal minimum content of a departure clearance. It must specify: - The direction of take-off and the turn after take-off. - The track to be made good before proceeding on the desired heading. That means the path you must fly along the ground before you're allowed to turn onto your planned heading. - The level to maintain before continuing the climb to your assigned cruising level. So there's an intermediate altitude you hold first. - The time, point, and/or rate at which the level change shall be made. In other words, when you climb, where you climb, and how fast you climb are all things the clearance can dictate. - And any other necessary manoeuvre consistent with the safe operation of the aircraft. So the clearance isn't just "cleared for take-off" — it's a full instruction set covering direction, track, levels, and the timing of changes. Now, paragraph 17.29, take-off direction. Here's an interesting point: departing aircraft may be expedited by suggesting a take-off direction which is not into the wind. Normally you'd want to take off into the wind for better performance, but ATC can suggest a different direction to speed things up. However — and this is the key responsibility — it is the responsibility of the pilot-in-command to decide between making such a take-off, or waiting for a normal take-off in the preferred direction. So ATC can suggest, but the captain makes the final call. Next, paragraph 17.30, delays. To avoid excessive holding at the destination, aircraft may be held at the departure aerodrome prior to take-off. So instead of circling at the destination, you wait on the ground at your departure point. But there's a duty on ATC here: ATC is required to advise operators — or their nominated representative — of substantial delays, and in any case where the delay is expected to exceed 30 minutes. So if the delay is going to be more than half an hour, the operator must be told. Finally, paragraph 17.31, information for departing aircraft. This is about what the approach controller must pass to departing aircraft. The first item is meteorological information. Specifically: information regarding significant changes in the meteorological conditions in the take-off or climb-out area, obtained by the unit providing approach control service, is to be transmitted to departing aircraft without delay — except when it is known that the aircraft already has received the information. Now, what counts as a significant change? The book lists them: changes relating to surface wind direction or speed, visibility, runway visual range, or air temperature — and note, air temperature specifically for turbine engined aircraft — and the occurrence of thunderstorm or cumulonimbus. So if any of those change significantly in the take-off or climb-out area, the approach controller must tell the departing aircraft immediately, unless the aircraft already knows. Let me tie this together. The departure phase is tightly controlled: the clearance defines your path and levels, the pilot-in-command owns the take-off direction decision, delays on the ground are managed to avoid holding at the destination with a 30-minute notification threshold, and the approach controller has a duty to pass significant weather changes without delay. Each of these is a distinct responsibility, and as a professional pilot you need to know exactly who does what and when.