Let’s pick this up right where the radar vectoring leaves off — Page 340, Lesson 451

Let’s pick this up right where the radar vectoring leaves off. I want to walk you through the speed control that ATC uses during an instrument approach, and then the rules that govern how a pilot executes that approach. First, the speed control. When ATC is sequencing aircraft on an instrument approach using radar, they manage the spacing by asking the aircraft to fly at a specified speed. The usual starting speed for an instrument approach, measured from the Initial Approach Fix — that’s the IAF — is 210 knots indicated airspeed, which we write as IAS. So a typical clearance might sound like: “Speedbird 289 leave Ockham heading 290 speed 210 kt.” That heading and speed instruction is the controller telling you exactly what to fly. Why 210 knots? Because that’s a speed most commercial aircraft can achieve without having to deploy drag or lift-enhancing devices — meaning no flaps, no slats, no speed brakes. It keeps the aircraft clean and efficient while still giving the controller a predictable speed to work with. Now, if a following aircraft is catching up, ATC will reduce its speed to maintain the necessary time/distance interval between the two aircraft. Here’s the key detail: speed adjustments are made in intervals of no more than 20 knots, and the required speeds are always multiples of 10. So a controller might say “Speedbird 289 maintain 180 kt” — that’s a multiple of 10, and it’s within 20 knots of your previous speed. You won’t be told to fly 187 knots, and you won’t be asked to drop from 210 straight to 160. But there’s a limit to this speed control. During the latter stages of the approach, the pilot needs to reduce speed to Vat — that’s the threshold speed, the target speed for crossing the threshold. So no further speed control will be applied after the aircraft has passed 4 nautical miles from touchdown. Inside that 4-mile point, the pilot owns the speed and configures the aircraft for landing. Now let’s move to the rules about how the approach itself is flown. First, unfamiliar procedures. If a pilot-in-command reports — or if it’s clearly apparent to the ATC unit — that he or she is not familiar with an instrument approach procedure, then ATC must specify several things: the initial approach level, the point at which the procedure turn will be started — and that point is given in minutes from the appropriate reporting point — the level at which the procedure turn shall be carried out, and the final approach track. However, there’s an exception: if the aircraft is to be cleared for a straight-in approach, then only the last item — the final approach track — needs to be specified. And the missed approach procedure shall be specified when deemed necessary. Next, visual reference to terrain. If the pilot establishes visual reference to terrain before the approach procedure is complete, the entire procedure must nevertheless be executed — unless the aircraft requests and is cleared for a visual approach. So you can’t just abandon the procedure the moment you see the ground; you either fly the full procedure or you formally request a visual approach and get cleared for it. Finally, the choice of procedure. A particular approach procedure may be specified by ATC to expedite traffic. But if no specific approach procedure is specified, that omission indicates that any authorized approach may be used at the discretion of the pilot. So the default is pilot’s choice; the controller only dictates a specific procedure when traffic flow demands it. Let me tie that together. You’ve got speed control from the IAF at 210 knots, stepped down in 20-knot increments to multiples of 10, and released at 4 nautical miles from touchdown so you can slow to Vat. And you’ve got the execution rules: unfamiliar pilots get the full brief, visual reference doesn’t let you skip the procedure unless you request a visual approach, and the choice of procedure defaults to the pilot unless ATC specifies one to expedite traffic. That’s the complete picture of how radar-controlled instrument approaches are flown.