Multi-engine Class B - Landing — Page 368, Lesson 445

I want to walk you through the landing distance calculation for a multi-engine Class B aeroplane, which is a light aircraft category under CS-23. This is where we turn the theoretical maximum landing distance into a practical, safe figure that accounts for the real world. First, let's establish what the regulations demand. CS-23 states that when we calculate the gross landing distance, we must account for several specific details. Think of this as the mandatory checklist of conditions that go into the calculation. The gross landing distance shall take account of: - The pressure altitude at the aerodrome — that's the altitude corrected for the standard atmosphere, which affects air density and therefore landing performance. - Standard temperature — the calculation assumes the standard temperature for that pressure altitude. - The runway surface conditions and the type of runway surface — whether it's hard, grass, wet, and so on. - The runway slope — whether the runway slopes uphill or downhill. - Not more than 50% of the reported headwind component, or not less than 150% of the reported tailwind component. This is a safety margin: we only credit half the headwind that helps us stop, but we penalise ourselves with one and a half times the tailwind that hurts us. - And finally, the despatch rules for scheduled or planned landing calculations, which are found in EU-OPS 1.550 (c). Now, let's look at the correction factors. These are the multipliers we apply to the gross landing distance when conditions are non-standard — like grass, wet, or sloping runways. Starting with grass. In CAP 698, section 3, page 17, point (b), we read that if the runway is grass up to 20 cm high on firm soil, we multiply the landing distance by a factor of 1.15. That increases the landing distance by 15%. The reason is simple: grass creates more rolling resistance, but it also means the surface is less predictable, so we need more distance to be safe. Next, wet. Point (c) says that if there's an indication the runway may be wet at the estimated time of arrival, we again multiply the landing distance by 1.15 — another 15% increase. However, there's an important caveat: if the aeroplane manual gives additional information on landing on wet runways, we may use that instead, even if it gives a lesser distance than the 1.15 factor. So the manual's data can override the generic factor if it's more favourable. Now for slope. Point (d) states that the landing distance should be increased by 5% for each 1% downslope. So for a 1% downslope, we multiply by 1.05. For a 2% downslope, the factor is 1.1. A downslope means the runway slopes downward in the direction of landing, which makes the aeroplane accelerate and need more distance to stop. Crucially, point (d) also states that no allowance is permitted for upslope. Why? Because an upslope reduces the landing distance — it helps you stop. If a pilot were to ignore that reduction and still use the longer distance, then a margin of safety would be incorporated into the calculation. So we never credit the upslope benefit; we just don't penalise ourselves with it. Finally, point (e) brings us back to the despatch rules. There must be compliance with the despatch rules for scheduled or planned landing calculations, and these are found in EU-OPS 1.550 (c). This ties the landing distance calculation into the operational rules that govern whether an aeroplane can be despatched to a particular destination or alternate. So the full picture is this: we start with the gross landing distance, then we apply the mandatory factors — pressure altitude, standard temperature, surface conditions and type, slope, and the headwind/tailwind limits. Then, for non-standard conditions, we apply the correction factors: 1.15 for grass up to 20 cm on firm soil, 1.15 for a wet runway (unless the manual says otherwise), and 5% per 1% downslope with no upslope credit. And we always ensure compliance with EU-OPS 1.550 (c) for despatch. That's the complete landing distance calculation for a multi-engine Class B aeroplane.