We're starting a brand-new topic now: Class A landing performance — Page 470, Lesson 580

We're starting a brand-new topic now: Class A landing performance. This is the chapter where we take the aircraft from the moment it's on the approach, through the flare, touchdown, and the landing roll, and we make sure the whole thing is legal and safe under the regulations. Let me set the scene. We're dealing with what's called a "Class A" aeroplane — that's the certification category for multi-engine jets and turboprops operating under the performance requirements we use in commercial aviation. Everything in this chapter is about the landing phase, and the very first thing we look at is the landing climb requirement. Here's the core idea: after we've committed to land, we need to be able to climb away again if we have to go around. The regulations demand that a Class A aeroplane, at the moment of landing, has enough climb performance to execute a missed approach safely. This isn't just a nice-to-have — it's a certified limit. The aircraft must be able to climb at a specific gradient with one engine inoperative, because a go-around is exactly the kind of situation where you might have just lost an engine. Now, this is where the figure comes in. I want you to look at Figure 18.1, which shows the landing performance climb limit. What you're seeing is a chart that plots the maximum landing mass against the pressure altitude and the ambient temperature. The chart is built around that climb gradient requirement. As you go up in altitude or temperature, the air gets thinner, the engines produce less thrust, and the wings produce less lift for a given speed. So the maximum mass at which you can still meet the climb gradient gets lower. The chart gives you that limit line — if you're above it, you cannot legally land at that aerodrome with that mass, because you couldn't guarantee the go-around climb. Let me be precise about the gradient itself, because this is a number you need to know cold. For a two-engine aeroplane, the landing climb gradient with one engine inoperative must be at least 3.2%. For a three-engine aeroplane it's 2.7%, and for a four-engine aeroplane it's 2.4%. The more engines you have, the smaller the percentage of total thrust you lose when one fails, so the required gradient is lower. That's the logic — the requirement scales with how much thrust you keep. And there's a critical detail about how this climb is measured. The gradient is calculated with the critical engine inoperative — that's the engine whose failure would have the most adverse effect on performance. The remaining engines are at go-around thrust, which is the maximum thrust you can use for a limited time to get out of trouble. The landing gear is down, because in a go-around you haven't retracted it yet. And the flaps are in the landing configuration — the full landing flap setting, because that's what you'd have selected at that moment. There's also a speed element. The climb is done at a speed no greater than 1.3 times the stalling speed in the landing configuration, which we call Vref — the reference landing speed. So the whole thing is defined: one engine out, gear down, flaps in landing position, go-around thrust, at Vref or less, climbing at that minimum gradient. Now, why does this matter for the pilot in the real world? Because it sets a maximum landing mass for every aerodrome. When you're planning the flight, you check the landing mass against this limit for the destination. If you're too heavy, you have options — you can burn off fuel, you can dump fuel if the aircraft has that capability, or you can divert to an aerodrome where the conditions allow a higher landing mass. But you cannot legally land overweight at that field, because the go-around wouldn't be guaranteed. So let me tie this together. The landing climb requirement is the first gate in landing performance. It's a certified, regulatory limit based on a one-engine-inoperative climb at a minimum gradient, measured in the landing configuration at go-around thrust. The chart in Figure 18.1 turns that requirement into a usable limit line for the crew. That's the foundation — and from here we move on to the landing distance requirements, which is the next gate we have to clear.