The previous lesson built the low-visibility machine; this one reads its price list. Everything here comes from the acceptable means of compliance to the minima rule and to the LVO approval, and nearly every number is a table entry the exam quotes back. One distinction from the previous module is worth restating once: planning minima decide whether an aerodrome may be put on the plan, while the operating minima priced in this lesson decide what the crew may actually fly when they arrive.
Taking off into the murk
The commander's take-off gate is the rule the commander lesson taught: satisfied that the weather and the runway condition will not prevent a safe take-off, minima consistent with equipment, systems, performance and qualifications. The minima themselves come from the guidance. Take-off minima should be expressed as visibility or RVR limits, with additional conditions such as a ceiling specified where obstacles must be seen and avoided on departure or a forced landing provided for. The selected values must give enough visual reference to control the aircraft through both a rejected take-off in adverse circumstances and a continued take-off after failure of the critical engine, and for night operations the prescribed runway lights should be in operation.
Performance splits the tables. An aeroplane that can, after a critical engine failure at any point, either stop or continue to 1,500 ft above the aerodrome clearing obstacles uses the standard facilities table below. One that cannot may need to re-land immediately and see obstacles, so its minima are built from the height at which its one-engine-inoperative net take-off flight path begins, using the engine-failure-height table as well. Single-engined turbine aeroplanes approved for SET-IMC carry one more caveat: unless the operator makes use of a risk period, where the surface ahead of the runway does not allow a safe forced landing, the RVR should not be below 800 m.
Runway lights price the take-off
Without an LVTO approval, the facilities buy the visibility down in three steps:
500 m by day with no facilities at all, provided the pilot can continuously identify the take-off surface and hold direction.
400 m by day with centre line markings, runway edge lights or runway centre line lights.
400 m at night, which needs runway end lights, or colour-coded edge or centre line lights in their place, plus edge or centre line lights.
For the aeroplane that may need to re-land, the assumed engine-failure height sets a floor of its own: up to 150 ft it stays at 400 m, from 151 to 200 ft it is 500 m, from 201 to 300 ft it jumps to 1,000 m, and above 300 ft, or when no positive take-off flight path can be built at all, it is 1,500 m. With the LVTO approval of the previous lesson, the ladder continues downward:
300 m by day with centre line markings and runway edge lights; at night, runway end lights or centre line lights as well.
150 m with centre line markings, edge, end and centre line lights together.
125 m when the centre line lights close up to 15 m spacing and the edge lights to 60 m or less.
Below 125 m — only with a certified take-off guidance system, centre line lights at 15 m, signal protection to category III standard, and an RVR no lower than the AFM's minimum or, failing a stated one, 75 m.
One kindness runs through every band: the reported RVR for the initial part of the take-off run can be replaced by pilot assessment, and the required value must be met for all reporting points from the commencement of the take-off to the calculated accelerate-stop distance, or, below 125 m, the greater of that and the take-off distance.
The floor under every approach
The height side of any approach minimum is a highest-of computation. The DH for a 3D operation, or a 2D operation flown with the continuous descent final approach (CDFA) technique, should not be lower than the highest of: the obstacle clearance height for the aircraft category, the published procedure DH or MDH, the system minima, the runway-type minimum, and any AFM minimum. A 2D approach flown without CDFA uses the same computation for its MDH. The system minima are a table sorted by the honesty of the guidance:
200 ft — ILS, MLS, GLS, PAR, and GNSS/SBAS flown as LPV, though LPV earns 200 ft only where the published vertical alert limit is at most 35 m, and otherwise stands at 250 ft.
250 ft — LP, LNAV, LNAV/VNAV, localiser with or without DME, SRA terminating at half a mile, and VOR/DME.
300 ft — SRA terminating at 1 NM, VOR without DME, and NDB/DME.
350 ft — SRA terminating at 2 NM or more, NDB alone, and VDF.
The runway type adds its own floor: 200 ft on a category I precision approach runway, 250 ft on a non-precision approach runway, and circling minima on a non-instrument runway. And where the DA/H or MDA/H is barometric, it should be adjusted when the ambient temperature falls significantly below ISA; the cold-temperature arithmetic itself belongs to the altimetry chapters of other subjects.
Below the minimum descent
The commander lesson taught when an approach may not continue past 1,000 ft, and its rule finishes the story at the bottom: a missed approach at or before the DA/H or MDA/H unless the required visual reference is established, and a prompt go-around if it is lost afterwards. What this lesson adds is the list itself. For Type A operations and CAT I, at least one of the following should be distinctly visible and identifiable to the pilot at the minimum:
elements of the approach lighting system;
the threshold, its markings, its lights, or its identification lights;
the visual glide path indicator;
the touchdown zone, its markings or its lights;
the runway edge lights; or
other references specified in the operations manual.
CAT I and its RVR
CAT I is the Type B operation flown to a DH not below 200 ft, and its visibility minimum is a greatest-of computation across three tables: the runway-type floor, an RVR of 550 m on a category I precision runway and 750 m on a non-precision runway; the lighting-class table, which at a DH of 200 to 210 ft reads 550 m with full approach lighting (FALS), 750 m with intermediate (IALS), 1,000 m with basic (BALS) and 1,200 m with none (NALS), the classes cut by approach-light length at 720 m, 420 m and 210 m; and the aids-and-equipment table. That last one is where crew and kit buy visibility: with touchdown-zone and centre line lights there is no table limitation for a 3D operation on a small track offset, whatever the crew complement. Without those lights, the crew starts to matter: a single-pilot operation should never use less than 600 m with a HUDLS or an autopilot or flight director flown to DH, and 800 m otherwise, against 750 m for a multi-pilot crew in the same unguided case. Two adjustments close the section: category A and B aeroplanes cap their computed requirement at 1,500 m, and an approach with a level segment at or above the MDA/H adds 200 m for categories A and B and 400 m for C and D.
When no RVR is reported, a converted meteorological visibility may stand in for it, with two absolute exceptions the exam guards jealously: never to satisfy take-off minima, and never to continue an approach in low-visibility operations. The conversion multiplies the reported visibility by 1.5 by day and 2.0 by night with high-intensity approach and runway lights, by 1.0 and 1.5 with any other lighting, and by 1.0 by day only with no lights; for flight planning the factor is always 1.0. And where the required RVR exceeds the maximum value the aerodrome operator can assess, CMV should be used in its place.
CAT II, priced
CAT II lives between DHs of 100 and 199 ft, the DH determined by radio altimeter or equivalent and never lower than the highest of the AFM minimum, the obstacle clearance height for the category, the DH the crew is qualified to, and 100 ft. Its lowest RVR follows the DH band: 300 m at a DH of 100 to 120 ft, though a category D aeroplane needs 350 m unless it lands automatically or by HUDLS to touchdown; 400 m from 121 to 140 ft; and 450 m from 141 to 199 ft.
CAT III, priced
CAT III prices by the failure manners the previous lesson classified. With a DH of 50 to 99 ft and no roll-out guidance required, the lowest RVR is 175 m. Below 50 ft, or with no DH at all, the roll-out system, the same failure classes applied past touchdown, decides: 125 m with a fail-passive system and 75 m with a fail-operational one, and an AFM may authorise lower values for a certified fail-passive or HUD roll-out system, never below 75 m. A no-DH operation needs three things: the AFM specifies it, no published information says the aid or aerodrome cannot support it, and the crew is qualified for it. The DH, where one is used, again comes from the radio altimeter and sits no lower than the AFM minimum and the crew's qualification.