I want you to picture the arrival flow first — Page 316, Lesson 411

Let’s pick this up right where the coordination between the Approach Controller and the Aerodrome Controller gets interesting. I want you to picture the arrival flow first. For arriving IFR traffic — that’s instrument flight rules traffic, flying in IMC, which is instrument meteorological conditions, meaning the pilot can’t see the runway visually — the Approach Controller will transfer control of the aircraft to the Aerodrome Controller at a point during the approach. The reason for that transfer is so that separation from departing traffic can be achieved, and so that sufficient time is available to issue a landing clearance. So the handover isn’t just administrative; it’s timed so the aerodrome controller can sequence the arrivals against the departures and still have time to clear the aircraft to land. Now, there’s an exception. For certain types of approach — PAR, which is Precision Approach Radar, or SRA, which is Surveillance Radar Approach — the aircraft will remain under control of the Approach Radar Controller throughout the entire approach. That means the radar controller has to obtain the landing clearance from the aerodrome controller and pass it to the pilot during the latter stages of the approach. So the radar controller becomes the relay for the landing clearance. Then there’s the sequencing responsibility. The Aerodrome Controller, in co-operation with the Approach Controller, will be responsible for sequencing departures during low visibility IFR operations. So when visibility is low and everyone is flying instrument procedures, the two controllers work together to decide the order in which departures leave. Now here’s the meat of it — two situations are considered for how a departure can be released relative to an arriving aircraft. First, the Complete Approach. If an aircraft is making a complete instrument approach — that means it’s flying the full procedure, including the turns that position it onto final — a departing aircraft may take off in any direction until the arriving aircraft has started its procedure turn or base turn leading to final approach. So before that turn starts, the departure can go in any direction at all. But once the arriving aircraft has started its procedure turn or base turn leading to final approach, the departure may only take off in a direction which is different by at least 45 degrees from the reciprocal of the direction of approach. The reciprocal is the opposite direction — 180 degrees away. So if the approach is toward the north, the reciprocal is toward the south, and the departure must be at least 45 degrees off that reciprocal. And there’s a time condition too: the take-off must be made at least 3 minutes before the arriving aircraft is estimated to be over the beginning of the instrument runway. So you have both a direction constraint and a time constraint working together. Second, the Straight-in Approach. If an aircraft is making a straight-in approach — no procedure turn, it comes directly onto final — a departing aircraft may take off in any direction until 5 minutes before the arriving aircraft is estimated to be over the instrument runway. So that’s a longer lead time, 5 minutes, because the arriving aircraft is coming straight in and closing faster. Alternatively, the departure may take off in a direction which is different by at least 45 degrees from the reciprocal of the direction of approach of the arriving aircraft until 3 minutes before the arriving aircraft is estimated to be over the beginning of the instrument runway. So again, the 45-degree-off-reciprocal rule applies, but with a 3-minute lead time. And there’s a third option: the departure may take off before the arriving aircraft crosses a designated fix on the approach track, as determined by the ATS authority — that’s the Air Traffic Services authority. So the fix gives you a geographic reference point instead of a pure time calculation. Now, let me show you this visually — Figure 16.22 illustrates exactly these two cases, the complete approach and the straight-in approach, with the timing and direction constraints laid out. Next, there’s a provision about information to arriving aircraft. If a pilot requests it, or if it’s apparent to ATC that the pilot is not familiar with the procedures for an instrument approach, information will be passed to enable the approach to be flown. So the controller gives the pilot what they need to fly the procedure. And here’s a nice detail: if the aircraft has been cleared for a straight-in approach, only details of the final approach track need be passed. So for a straight-in, you don’t need the full procedure briefing — just the final track. Finally, missed approach tracks. This is the Heathrow case — parallel runway segregated operations. When those are in progress, a missed approach to the landing runway creates a simultaneous departure situation where procedures for Mode 3 are not in force. Mode 3 is a specific set of procedures, and in this situation they don’t apply. To overcome the problems this creates, procedures are to be implemented to ensure that the missed approach track diverges from the normal departure track by at least 30 degrees. So the missed approach path must be angled at least 30 degrees away from the departure path, so the two don’t conflict. Figure 16.23 shows that divergence. So to tie it together: you have the handover timing, the PAR/SRA exception where the radar controller keeps control, the sequencing responsibility in low visibility, the two departure-release scenarios with their direction and time constraints, the information provision for unfamiliar pilots, and the 30-degree divergence requirement for missed approaches in parallel runway operations. That’s the full picture of how arrivals and departures are coordinated.