Single-engine Class B - Landing — Page 336, Lesson 411

Let’s start with the despatch rule for a single-engine Class B aeroplane landing, because it’s the foundation for everything else here. The rule is simple to apply: you always consider two masses. First, the greatest mass the aeroplane could have in still air. Second, the greatest mass it could have in the forecast wind conditions. Of those two, you take the lesser mass as your despatch mass. In most cases, the still air mass is the lesser one, so that’s what you’d use. But there’s an exception: when you have a tailwind on a unidirectional runway. A unidirectional runway is one whose direction for take-off and landing is fixed in one direction — you can only operate in that single direction. In that tailwind case, the maximum landing mass in the tailwind will be less than the maximum landing mass in still air, so the tailwind mass becomes the limiting one. Now, the reference landing speed, VREF. You may recall that VREF is the regulatory speed at the landing screen height. For a single-engine Class B aeroplane, VREF must be no less than 1.3 times the stall speed in the landing configuration — that’s written as 1.3VS0. The VS0 is the stall speed with the landing configuration set. A pilot must adhere to VREF speeds because those are the speeds used to construct the landing graphs or tables in the aeroplane flight manual. If you deviate from VREF, the required aircraft performance would not be achieved — the landing distance data simply wouldn’t hold. Now let’s look at how landing distance is actually calculated. Every aeroplane will have either a pilot operating handbook or an aeroplane flight manual. Their purpose is twofold: to show how to operate the aeroplane, and to detail the aeroplane’s performance. The example graph we’ll use is figure 2.4 on page 10 of section 2 in CAP 698. When you use any such graph, always look at the associated conditions first — pay particular attention to the power and flap settings shown at the top of the graph. Also notice that this graph assumes a runway which… well, we’ll pick that up next.