General Principles - Landing — Page 289, Lesson 361

Let's pick up right where the landing technique leaves off, because the next part of the book is about a serious hazard: microbursts and windshear during the landing phase. First, I want to frame why this matters. Of all the phases of flight, it's the landing phase that is the most susceptible to severe weather conditions. The reason is a combination of factors: the low altitude, the low speed, the low thrust settings, and the high drag during the landing phase. All of those together mean the aeroplane is at its most vulnerable. You have very little altitude to recover, very little speed margin, and the engines are spooled down, so you have almost no energy to work with. Now, the book gives you a clear operational rule here. Landing when windshear is observed or forecast should be avoided. That's the primary instruction — if you know it's there, don't go in. But if conditions are within limits, then you land at a higher speed. And here's the caution that comes with that: the higher landing speed will greatly increase the distance of the airborne section and the ground roll of the landing. So you're trading safety margin against runway length — you need to be very aware of that trade-off. Let me define the terms precisely, because these are exact technical terms. Windshear is a change in wind speed or direction over a short distance — it can be vertical or horizontal. A microburst is a specific, intense form of downburst — a concentrated column of descending air that hits the ground and spreads out violently in all directions. The book shows you an illustration of a microburst at an airfield in Figure 6.9. The danger of a microburst during landing is that you fly into the outflow — the air spreading outward from the downburst. You get a sudden headwind increase, which raises your indicated airspeed and makes the aeroplane balloon. Then you pass through the core and hit the tailwind on the other side, which suddenly reduces your airspeed and your lift — exactly when you're low, slow, and configured for landing. That's why the book tells you to avoid it entirely if observed or forecast. So the key takeaway from this section is the decision sequence: avoid landing if windshear is observed or forecast. If you must land because conditions are within limits, increase your landing speed — but understand that this increases both the airborne distance and the ground roll, so you need the runway to accommodate it. And remember the vulnerability: low altitude, low speed, low thrust, high drag. That's the whole reason this phase is the most susceptible. That's the core of the microburst and windshear section.