It basically doesn’t matter why you need to discard your visual landing approach and go around. It could be something as routine as another airplane or a vehicle on the runway, a poorly flown approach or configuration error, or a controller’s direction in response to something you can’t even see. But go around you shall, and you “suddenly” have a whole new task to perform, an airplane to reconfigure and a low-speed, high-power maneuver to fly. Did we mention you’re close to the ground?
We put suddenly in scare quotes above because there’s no reason you should be surprised by the need to go around. A landing approach has two outcomes: a successful landing or a go-around. (Supposedly, there’s a third outcome—bending the airplane—but that’s what we’re trying to avoid.) It’s a binary thing, and there’s absolutely no reason to be surprised the thing you desired most isn’t going to happen right away. Let’s look at the sequence of events.
