Parallel or Near-parallel Runway Operation — Page 231, Lesson 309

Right, let’s get into the meat of this. We’re looking at Simultaneous Operation on Parallel or Near-parallel Runways, and the first thing I want you to grasp is why this whole concept exists. The driving force is capacity. At a major aerodrome handling IFR traffic — that’s Instrument Flight Rules traffic, aircraft flying on instruments — in IMC, which is Instrument Meteorological Conditions, poor visibility and low cloud, the number of aircraft you can land per hour is strictly limited. The whole point of parallel runways is to increase that capacity. If an aerodrome already has dual, parallel precision approach runways — and by precision approach I mean an ILS, an Instrument Landing System, or an MLS, a Microwave Landing System — then it could increase its capacity if those runways could be operated safely at the same time, independently, even in IMC. Now, this isn't a theoretical idea. There's real pressure on major aerodromes, like Stansted, to build a second parallel runway, and virtually all new aerodrome constructions — Chek Lap Kok in Hong Kong is the classic example — are built with parallel runway configurations. And it's not just two runways. It's common to see three or even four parallel, or near-parallel, runways all in operation together. In this section, we're going to bias the discussion towards pure parallel arrangements, but I want you to understand the procedures are the same, or similar, for all other arrangements. Here's the single most important rule to lock in right now: all parallel runway operations require the provision and use of radar. No radar, no parallel runway operation. That's non-negotiable. Now, there are two basic modes of operation possible for simultaneous parallel instrument approaches. Let's take Mode 1: Independent Parallel Approaches. In this mode, approaches are made to parallel runways where radar separation minima between aircraft using adjacent ILS and/or MLS are not applied. Let me unpack that. Normally, air traffic control uses radar to keep a minimum distance between aircraft. In independent parallel approaches, that radar separation minimum is not applied between aircraft on the adjacent runways. That's what makes it "independent" — each approach is handled as if the other runway's traffic isn't a factor for separation purposes. But — and this is critical — regardless of the weather conditions, all approaches are to be radar monitored, with radar controllers specifically detailed for that duty only. That means there's a dedicated controller whose sole job is watching the radar picture for these approaches. They're not doing anything else. And those radar controllers are allocated dedicated discrete RTF frequencies. RTF is Radio Telephony — the voice radio channel. "Discrete" means a frequency dedicated solely to that controller, not shared. So the pilot talks to that specific radar controller on a specific frequency. Now, the operational restriction: only straight-in approaches are permitted with parallel runway operation. Track reversal procedures are not permitted. Track reversal — that's a procedure like a procedure turn or a holding pattern that reverses your direction to align with the runway. Not allowed here. You must be coming straight in, aligned with the runway. Now let's look at the separation in Mode 1. Each pair of parallel approaches will have a 'high' side and a 'low' side. This provides vertical separation until aircraft are established inbound on the respective ILS localizer course. The high side will be 300 m (1000 ft) above the low side. So one aircraft is flying 1000 feet higher than the other until they're both established on their localizer. Here's the key condition: before vertical separation can be reduced below 300 m (1000 ft), both aircraft on a simultaneous parallel approach must be established on the ILS localizer centre line or MLS final approach track. So the moment they're both locked onto their respective localizer centre lines, the controller can bring them down from that 1000-foot vertical split. And once that 300 m separation is reduced, the radar controller will issue instructions if the aircraft deviates significantly from the localizer course. So the radar controller's job is to watch for that deviation and correct it. Let me tie this together for you. The whole system is built on a foundation of radar monitoring with dedicated controllers. The aircraft are vertically separated by 1000 feet until they're both established on their localizers. Only then can that vertical separation be reduced, and from that point on, the radar controller is watching for any significant deviation from the localizer course and will issue instructions to correct it. And remember, straight-in only — no track reversals, ever. That's the foundation of independent parallel approaches. Next we'll look at the second mode of operation.