Control of Aircraft — Page 340, Lesson 450

I want to walk you through the control of aircraft during approaches — specifically the visual approach and the instrument approach. This is where we move from en-route control into the final phase of getting an aircraft safely onto the ground. Let's start with the visual approach. The formal definition is this: a visual approach is an approach by an IFR flight when either part or all of an instrument approach procedure is not completed, and the approach is executed with visual reference to terrain. Let me unpack that. IFR means instrument flight rules — flying by reference to the instruments rather than by looking outside. Normally an IFR flight would fly a full instrument approach procedure, which is a precisely defined path using navigational aids. But a visual approach lets that IFR flight abandon part or all of that procedure and instead fly the approach by looking at the ground. The key condition is that the pilot must have visual reference to the terrain — they must actually be able to see the ground and orient themselves to it. Now, when can an IFR flight be cleared for a visual approach? There are two alternative conditions. First, the pilot can maintain visual reference to the terrain, and the reported ceiling is at or above the approved initial approach level for the aircraft so cleared. The ceiling is the height of the base of the lowest cloud layer covering more than half the sky. The initial approach level is the altitude at which the instrument approach procedure begins. So if the cloud base is at or above that starting altitude, and the pilot can see the terrain, a visual approach is permissible. The second condition is that the pilot reports — either at the initial approach level or at any time during the instrument approach procedure — that the meteorological conditions are such that, with reasonable assurance, a visual approach and landing can be completed. In other words, the pilot themselves declares that the weather is good enough that they're confident they can see the ground and complete the approach and landing visually. Now, separation. This is critical. Separation shall be provided between an aircraft cleared to execute a visual approach and other arriving and departing aircraft. So even though the pilot is flying visually, air traffic control still has a duty to keep that aircraft separated from everyone else in the vicinity. For successive visual approaches — meaning one visual approach following another — radar or non-radar separation shall be maintained until the pilot of a succeeding aircraft reports having the preceding aircraft in sight. So the following aircraft must actually see the aircraft ahead before separation responsibility can be relaxed. Once that sighting is reported, the aircraft shall be instructed to follow and maintain separation from the preceding aircraft. So the pilot takes over the job of keeping their own distance from the aircraft in front. There's also a communication requirement. Transfer of communications should be effected at such a point or time that clearance to land, or alternative instructions, can be issued to the aircraft in a timely manner. In plain terms, the handover from one controller to another must happen early enough that the pilot can still receive landing clearance or any changed instructions without delay. Now let's move to the instrument approach. This is the opposite end of the spectrum — the approach flown by reference to instruments. Instrument approaches are carried out under the supervision of the approach controller. That's the controller responsible for the arrival phase. But there's a delegation option. Where radar vectoring and monitoring of approaches is carried out, control may be delegated to a radar director or radar final controller. Radar vectoring means the controller gives the pilot specific headings to fly, guiding them onto the approach path. Monitoring means the controller watches the aircraft's progress on radar. In that situation, the approach controller can hand control to a radar director or a radar final controller — these are specialist controllers who manage the final stages of the approach using radar. Now, the key point on speed control. The method of maintaining separation during sequenced instrument approaches using radar is by asking the aircraft concerned to fly at a specified speed. Sequenced means multiple aircraft arriving one after another on the same approach. Because they're all following the same path, separation is maintained by controlling their speeds. The controller asks each aircraft to fly at a specific speed, which spaces them out along the approach path. And it's usual for an aircraft to start — and that's where the excerpt cuts off. But the principle is clear: speed control is the primary tool for spacing aircraft on a sequenced radar approach. Let me just tie this together. The visual approach is about letting an IFR flight fly visually when conditions permit, with separation maintained until the pilot sees the aircraft ahead. The instrument approach is the fully procedural, radar-supervised approach where speed control is the method of maintaining separation between successive aircraft. Both are about the same thing — getting aircraft safely onto the runway in sequence — but they use completely different tools: visual reference in one case, radar and speed control in the other.