Single-engine Class B - Landing — Page 327, Lesson 406

Right, let's pick this up with the landing performance corrections for a single-engine Class B aeroplane. We've already covered the regulation requirements for the maximum landing distance that must be available at a destination or alternate airfield. Now we're going to look at how we actually calculate the gross landing distance when conditions aren't standard — specifically grass, wet, and sloping runways. Let's start with grass. In CAP 698, Section 2, page 9, under point (b), we read that if the runway is grass up to 20 cm high, the landing distance should be multiplied by a factor of 1.15. So that's a 15% increase in the landing distance. The key qualifier here is "up to 20 cm high" — that's the condition that triggers the factor. Next, wet runways. If there is an indication that the runway may be wet at the estimated time of arrival, the landing distance should again be multiplied by a factor of 1.15 — another 15% increase. But there's an important caveat here: if the aeroplane flight manual gives additional information on landing on wet runways, that information may be used, even if it gives a lesser distance than the 1.15 factor. So the manual's data can override the generic factor, provided it's in the manual. Now for slope — this is point (d). The regulation states that no allowance is permitted for upslope. Let me explain why. An upslope will reduce the landing distance — the aeroplane decelerates more quickly going uphill. If a pilot were to ignore that reduction, then the landing distance calculation would incorporate a margin of safety. In other words, by not crediting the upslope, you're being conservative — you're planning for a longer landing than you actually need. So no credit is taken. But for downslope, the landing distance must be increased by 5% for each 1% of downslope. So for a 1% downslope, you multiply the landing distance by a factor of 1.05. For a 2% downslope, the factor is 1.1. That's a linear relationship — 5% per 1% of slope. Now, the despatch rules. Point (e) states that there must be compliance with the despatch rules for scheduled or planned landing calculations, and these are found in EU-OPS 1.550 (c). Let me walk you through what those rules require. For despatching an aeroplane, it must be assumed that: - The aeroplane will land on the most favourable runway at the destination airfield in still air, and - The aeroplane will land on the runway most likely to be assigned, considering the probable wind speed and direction. Let me unpack the first assumption. "Most favourable runway" in still air — that means, assuming zero wind at the destination, you select the runway which would accommodate the largest possible landing mass. That's the most favourable runway — the one that gives you the greatest landing mass capability. Now, the second assumption — the runway most likely to be assigned, considering probable wind. If this second assumption cannot be met, then the aeroplane may be despatched only if an alternate aerodrome is designated, at which full compliance with the regulatory despatch requirements can be met. So the alternate provides the safety net when the most-likely runway assumption fails. So to summarise the whole picture: you take your gross landing distance, apply the correction factors — 1.15 for grass up to 20 cm, 1.15 for a wet runway unless the manual says otherwise, and 1.05 per 1% downslope, with no credit for upslope — and then you ensure your despatch planning complies with EU-OPS 1.550 (c), which requires you to consider both the most favourable runway in still air and the most likely assigned runway, with an alternate as the fallback.