Class A - Landing — Page 478, Lesson 588

Let’s start with the regulatory heart of Class A landing performance: EU-OPS 1.515, the landing distance requirement. This is the rule that tells you, for a destination or an alternate aerodrome, how much runway you are legally allowed to need versus how much runway actually exists. The key phrase is “landing distance required,” and it’s measured from 50 feet above the threshold to a full stop. That 50-foot point is the screen height — the height at which the aeroplane crosses the runway threshold in the landing configuration. The required distance, from that 50-foot point to a complete stop, must not exceed a fraction of the landing distance available. For a turbojet aeroplane, that fraction is 60%. For a turboprop aeroplane, it’s 70%. So if you have 2,000 metres of landing distance available, a turbojet may require no more than 1,200 metres, and a turboprop no more than 1,400 metres. There’s a note about short landing and steep approach procedures. Those may be approved based on lower screen heights, but never less than 35 feet. So the standard screen is 50 feet, and an approved procedure can bring that down, but the floor is 35 feet. Now, what is the landing distance required actually based on? The rule lists six factors. First, the aeroplane must be in the landing configuration — flaps and gear set for landing. Second, the speed at 50 feet must not be less than 1.23 times VSR0, or VMCL. Third, the aerodrome pressure altitude. Fourth, standard day temperature, which is ISA. Fifth, factored winds — and here’s a critical detail: you factor the wind as 50% of the headwind and 150% of the tailwind. That means you only credit half the headwind you might get, but you penalise yourself with one and a half times any tailwind. And sixth, the runway slope, but only if it’s greater than plus or minus 2%. So a slope within 2% is ignored; beyond that, it must be accounted for. Let me define those two speeds precisely, because they’re exam favourites. VSR0 is the stall reference speed in the landing configuration. VMCL is the minimum control speed during approach and landing with all engines operating. The full definition: it’s the calibrated airspeed at which, when the critical engine is suddenly made inoperative, it is possible to maintain control of the aeroplane with that engine still inoperative, and maintain straight flight with an angle of bank of not more than 5° towards the live engines. So if you lose the critical engine on approach, you must still be able to keep the aeroplane straight and controlled, banking no more than 5° into the good engines, at or above that speed. Next, runway selection and despatch rules. You must consider landing both in still air and in the forecast wind. In still air, you may select the most favourable runway. In forecast wind, you select the runway most likely to be used in that forecast wind. Then you take the lower of the two masses obtained from those two cases — the still-air case and the forecast-wind case — and that lower mass becomes your limiting mass for the field lengths available. So you compute a permissible landing mass for each scenario, and the more restrictive one governs. Now, non-compliance. If the still-air requirement cannot be met at an aerodrome with a single runway — meaning you can only land if there’s an adequate wind component — then the aircraft may still be despatched, but only if you designate two alternate aerodromes at which full compliance is possible. If instead the forecast-wind requirement cannot be met, the aeroplane may be despatched if you designate one alternate at which all the landing requirements are met. So the remedy differs: two alternates for a still-air failure, one alternate for a forecast-wind failure. Finally, wet runways. If the runway is forecast to be wet at the estimated time of arrival, the landing distance available must be at least 115% of the required landing distance. So you need 15% more runway available than required. However, a lesser factor may be used, provided it is published in the aeroplane flight manual and the authority has approved that factor. So 115% is the default, and a smaller factor is only allowed if it’s in the AFM and approved. That figure shows the landing performance climb limit — the climb capability you need during the landing phase, which ties into that 50-foot screen and the ability to go around if needed. And this second figure shows a typical presentation of landing distance data — the graph you’ll work through in CAP 698, section 4, page 46, with the worked example on page 40. You’ll need to read these graphs both in the normal direction, following the arrow heads, and in reverse. The questions at the end of the chapter give you practice. That’s the complete landing distance requirement for Class A aeroplanes — the 60/70% factors, the six basis factors, the two speed definitions, the runway selection logic, the non-compliance remedies, and the wet runway 115% rule.