Control of Aircraft — Page 333, Lesson 435

I want to walk you through radar vectoring now — this is the heart of how a radar controller actually steers you around the sky. Let's start with the definition, because everything else hangs off it. Radar vectoring is the passing of navigation information to a pilot by a radar controller, with the aim of getting the aircraft to fly a required track. So the controller isn't just watching you — they're actively telling you where to go. The purpose can be simple: to avoid weather, or to manoeuvre around another aircraft that shows up as a radar contact. Once the aim of the vectoring has been achieved, the pilot is told to "Resume own navigation," and at that point the controller gives you your position and any appropriate instructions. That phrase is the signal that radar vectoring has ended — you're back in charge of your own navigation. Vectoring can also be used to position the aircraft so that a straight-in instrument approach can be achieved. But here's a key restriction: radar vectoring for approach control purposes is only carried out inside a radar vectoring area, which we abbreviate RVA. And importantly, obstacles are marked on an RVA chart — that chart is your reference for what's in the area. Now let's look at the vectoring procedure itself, because there are strict rules about when it can start. Radar vectoring will not begin until the aircraft radar contact is determined to be within the RVA. So the controller has to positively establish that you're inside the area before they start steering you. The RVA is displayed on the radar display as a video map — that's an image electronically generated within the radar display software. So it's not a physical chart; it's drawn on the screen by the software itself. Now, a critical safety margin. Because of possible inaccuracies — and the technical term here is 'slippage' — aircraft will not be radar vectored closer to the edge of the RVA than half the applicable radar separation standard, or 2.5 nautical miles, whichever is greater. Let me unpack that. Slippage refers to the small errors or drift in the radar position information. To guard against that, the controller keeps you a safe distance from the boundary — at least half the radar separation standard, but never less than 2.5 nautical miles. So if the separation standard is, say, 5 nautical miles, half of that is 2.5, so you'd use 2.5. If the standard is larger, you use half of that larger figure. Normally, radar vectoring will begin at a fix at MSA — that's Minimum Safe Altitude. But it may begin at any time after the aircraft has been identified on radar and the aircraft altitude is known to the ATCO, the Air Traffic Control Officer. So the normal case is starting at a fix at MSA, but the controller has flexibility once you're identified and your altitude is known. The RVA chart displays the obstacles in the area together with the elevation of the terrain. So you know what's down there. Now, how does the controller actually steer you? The radar controller will pass magnetic headings to the pilot to steer, to make good a desired track over the ground. This is a crucial distinction. The pilot flies the heading — that's the compass heading you steer. But the controller adjusts the heading for the wind. So the controller is doing the wind correction calculation, and you just fly what you're told. The heading you fly is not necessarily the track you make good over the ground — the controller has already compensated for wind when they give you the heading. Then there's a hard altitude restriction. The aircraft will not be given clearance to descend below the RVA safe altitude until one of three conditions is met: you're established on the ILS localizer course, or you're on the final approach track, or the pilot reports that he or she is continuing the approach visually. Let me define that RVA safe altitude — it's the highest obstacle in the RVA plus MOC, which is Minimum Obstacle Clearance, rounded up. So the controller cannot clear you below that safe altitude until you're on the localizer, on the final approach track, or you've reported visual. And throughout the whole procedure, the radar controller must be aware of two things: the elevation of the terrain and the aircraft configuration. Why? To avoid spurious GPWS warnings — that's the Ground Proximity Warning System. If the controller isn't thinking about terrain and your configuration, you could get a false GPWS alert, which is distracting and dangerous. Let me also point you to the figure — Figure 17.3 shows the radar vectoring area, and you can see the RVA boundary, the MSA outside the RVA, and the safety altitude inside the RVA. That visual really ties together what I just described. So to summarise the whole picture: the controller vectors you inside the RVA, keeps you clear of the boundary by at least half the separation standard or 2.5 NM, starts normally at a fix at MSA, steers you with magnetic headings adjusted for wind, and won't let you descend below the RVA safe altitude until you're established on the localizer, on the final approach track, or visual. And all the while they're watching terrain and your configuration to keep GPWS quiet. That's radar vectoring in full.