Control of Aircraft — Page 343, Lesson 458

Let’s pick this up right where the controller’s duties get most intense — the final approach and landing phase. I want to walk you through the exact information that must be passed to an arriving aircraft, and then we’ll close with the rule on transferring control between ATC units. First, a note that frames everything: the meteorological information required here is identical to what’s in an ATIS broadcast for arriving aircraft. And it’s to be extracted from meteorological reports disseminated locally at the aerodrome. So the controller isn’t inventing this data — it comes from the local met reports. Now, at the commencement of final approach, the following information shall be transmitted to the aircraft. First, significant changes in the mean surface wind direction and speed. The word “significant” is defined in Annex 3 (Met), but if the controller has access to wind component tables, here are the thresholds: a mean head-wind component change of 10 knots, a mean tail-wind component change of 2 knots, and a mean crosswind component change of 5 knots. Notice the asymmetry — a tailwind change is significant at just 2 knots, because a tailwind is far more critical for landing performance than a headwind. Second, the latest information, if any, on wind shear and/or turbulence in the final approach area. Third, the current visibility representative of the direction of approach and landing, or, when provided, the current runway visual range value(s) and the trend, if practicable, supplemented by slant visual range value(s), if provided. So you have three possible visibility sources: the representative visibility, the RVR with its trend, and optionally the slant visual range. Then, during final approach — and this is a different, more urgent category — the following information shall be transmitted without delay. First, the sudden occurrence of hazards, for example unauthorized traffic on the runway. Second, significant variations in the current surface wind, expressed in terms of minimum and maximum values. Third, significant changes in runway surface conditions. Fourth, changes in the operational status of required visual or non-visual aids. And fifth, changes in observed RVR value(s), in accordance with the reported scale in use, or changes in the visibility representative of the direction of approach and landing. Also note the earlier items that apply generally: current runway surface conditions, in case of precipitants or other temporary hazards, and changes in the operational status of visual and non-visual aids essential for approach and landing. Finally, we have the rule on transfer of aircraft from one ATC unit to another. Transfer of control shall be at such a point, level, or time that information and instructions can be passed to the aircraft in a timely manner. So the handover isn’t arbitrary — it must be timed so the receiving unit can still communicate with the aircraft effectively. That’s the full picture of what the controller must give the pilot as the aircraft comes in, and how control moves between units.