All Weather Operations — Page 65, Lesson 106

I want to walk you through Category II operations now. This is a precision approach category that sits between the standard Cat I and the more demanding Cat III, and it has very specific limits you need to know cold. Let me start with the definition. A Category II operation is a precision instrument approach and landing that uses either ILS or MLS — Instrument Landing System or Microwave Landing System. The key numbers are: the decision height is below 200 feet but not lower than 100 feet, and the runway visual range must be not less than 300 metres. So you're going lower than Cat I, but you still have a hard floor at 100 feet and 300 metres RVR. Now, the operator — that's the airline or the company you fly for — must ensure that the decision height for a Cat II operation is not lower than the highest of several values. Let me walk through them one by one. First, the minimum decision height specified in the Airplane Flight Manual, if one is stated. Second, the minimum height to which the precision approach aid can be used without the required visual reference — that's a technical limitation of the ILS or MLS itself. Third, the Obstacle Clearance Height or Obstacle Clearance Level for the category of aeroplane. Fourth, the decision height to which the flight crew is authorized to operate — that's a crew qualification limit. And fifth, 100 feet. So the actual decision height you use is the highest of all these values, and it can never go below 100 feet. Now, the visual reference requirement for Cat II is very precise. You may not continue an approach below the Category II decision height unless you have visual reference containing a segment of at least three consecutive lights. Those lights must be from the centre line of the approach lights, or the touchdown zone lights, or the runway centre line lights, or the runway edge lights, or a combination of these. And that visual reference must include a lateral element of the ground pattern — that means an approach lighting crossbar, or the landing threshold, or a barrette of the touchdown zone lighting. There is one exception: if the operation is conducted using an approved HUDLS — that's a Head-Up Display Landing System — to touchdown, then that lateral element requirement doesn't apply. Let me now give you the actual minima table for Category II operations. I'll read it as a range of decision heights and their corresponding RVR values. For a decision height between 100 and 120 feet, the RVR is 300 metres for Category A, B, and C aeroplanes. For Category D aeroplanes, it's 300 metres with a note — note 2 — or 350 metres. I'll explain that note in a moment. For a decision height between 121 and 140 feet, the RVR is 400 metres for all categories — A, B, C, and D. For a decision height of 141 feet and above, the RVR is 450 metres for all categories. Now, note 1 in the table says this applies when the approach is autocoupled or uses an approved HUDLS to below the decision height. That means the autopilot or the head-up display is flying the approach down past the DH. And note 2 — the one that gives the 300 metre option for Category D at the lowest DH band — that's a specific allowance you'd need to check in the operator's documentation. So to summarise what you need to remember: Cat II takes you down to a minimum of 100 feet DH and 300 metres RVR. The visual reference must include at least three consecutive centre-line-type lights plus a lateral element, unless you have an approved HUDLS. And the RVR increases as your decision height goes up — 300 or 350 metres for the lowest band, 400 for the middle, and 450 for the highest.