First, the failure case — Page 337, Lesson 447

Let’s pick this up right where the landing clearance obligation ends, because that’s the exact point this passage is built on. I want to walk you through what happens when an aircraft that’s been cleared to land doesn’t actually land, and then we’ll move into the whole structure of Approach Control Service. First, the failure case. If an aircraft has been cleared to land and then fails to do so within 5 minutes after that landing clearance was issued — or alternatively, if it fails to contact the aerodrome controller after having been transferred to them — then the aerodrome controller has a mandatory duty. He will report the fact immediately to the ACC or the FIC. ACC is Area Control Centre, FIC is Flight Information Centre. And the moment that report goes out, the Alert Phase will be declared immediately. So this is a hard, time-limited trigger: five minutes, no contact, report, Alert Phase. That’s the safety net that catches an aircraft that’s gone silent or failed to complete the landing. Now let’s step back and look at the bigger picture — Approach Control Service. This is the service that provides ATC, Air Traffic Control, to traffic departing from, and arriving at, aerodromes. So it’s the bridge between the aerodrome environment and the wider airspace system. Here’s the key relationship. Where IFR traffic is departing to join airways, the approach controller is the link between the aerodrome departure procedures and the airways joining procedures. And vice versa for arriving traffic — the approach controller links the airways exit procedures back down to the aerodrome arrival procedures. So think of the approach controller as the hand-off point: he takes the aircraft from the aerodrome and hands it to the airways system, or takes it from the airways system and hands it back to the aerodrome. Now, the technology. It’s usual nowadays for radar to be used in approach control. But — and this is important — procedural approach control still exists. The passage gives you a concrete example: here at Oxford, for the VDF and NDB approach procedures. VDF is VHF Direction Finding, NDB is Non-Directional Beacon. So even without radar, approach control can be done procedurally, using these radio navigation aids. Now the regulatory structure. Where an aerodrome is in a CTR — that’s a Control Zone — approach control is mandatory. And in that case, the controller may be known as the zone controller. So the name changes with the environment. Also, if there’s more than one aerodrome in the CTR, the approach office — that’s the approach control room — may be located at another aerodrome. So the physical location of the controller isn’t necessarily at the aerodrome he’s serving. Now contrast that. Where an aerodrome is outside of a CTR, approach control — where it’s established, as here at Oxford — is advisory. So inside a CTR it’s mandatory, outside a CTR it’s advisory. That’s a fundamental distinction you need to hold onto. Next, delegation. Where procedures are established for instrument approaches, the approach controller may delegate radar vectoring — and monitoring of self positioning — to a radar director. So the radar director is a separate role that can take over the radar guidance duties. Finally, two specific responsibilities of the approach controller. First, at aerodromes in CTRs where the met conditions are IMC — that’s Instrument Meteorological Conditions — or where the criteria for VMC take-off cannot be met, the approach controller will be responsible for giving clearance for take-offs. So in poor weather, the approach controller issues the take-off clearances. Second, it will also be the approach controller’s responsibility to obtain clearance to land from the aerodrome controller for IFR flights carrying out low visibility instrument approaches. So in low visibility, the approach controller has to go get the landing clearance from the aerodrome controller on behalf of the IFR flight. So to tie it all together: the approach controller is the middleman between the aerodrome and the airways, mandatory in CTRs, advisory outside them, radar-based normally but procedural where needed, and he carries specific clearance responsibilities in poor weather and low visibility conditions.