We're starting a brand-new topic now: the Class A take-off climb — Page 426, Lesson 524

We're starting a brand-new topic now: the Class A take-off climb. This is the climb that happens right after you lift off, and for a Class A aeroplane — which is your multi-engine transport category jet — the regulations demand that we account for an engine failure in every phase of flight, and the take-off climb is no exception. Let me define the boundaries first. The take-off climb, or take-off flight path, extends from 35 feet above the take-off surface up to 1500 feet above the take-off surface. That 35-foot point is your "screen" height — the obstacle clearance screen you must clear. But there's an important exception: if you're doing a contaminated runway take-off, the take-off climb begins at 15 feet, not 35 feet. And the point on the ground directly below that 35-foot screen is called "reference zero." So reference zero is your horizontal datum on the ground, directly under the 35-foot screen. Now, within this take-off climb, there are two main requirements, and both are based on an engine failure occurring at VEF — that's the critical engine failure speed, the speed at which we assume the critical engine fails. The first requirement is that the aeroplane must achieve the minimum climb gradients. The second is that it must maintain sufficient obstacle clearance. And here's a crucial distinction I want you to hold onto: the climb gradient requirements are air-based gradients, while the obstacle clearance requirements use ground-based gradients. Air-based means relative to the air mass; ground-based means relative to the ground, which accounts for wind. When assessing compliance, the manufacturer or operator can use either a continuous demonstrated take-off climb or a segmented take-off climb. Segmenting makes the requirements and the procedure easier to comprehend, so most operators and manufacturers use the segmented profile — and that's what we'll use too. So let's look at the segments. The take-off climb is generally split into four unique segments, as shown in Figure 16.1. Each segment is characteristic of a distinct change in aeroplane configuration, speed, and/or thrust, with various actions and climb gradient requirements. You'll need to learn what unique characteristics define each segment. Notice the figure labels the gradient for four engines — that's a hint that the gradient requirements differ depending on how many engines you have, and we'll get into those specifics as we work through each segment. For now, I want you to remember the framework: the take-off climb runs from 35 feet (or 15 feet on a contaminated runway) up to 1500 feet, reference zero is the ground point under the 35-foot screen, the two requirements are minimum climb gradients and obstacle clearance, and we use a four-segment profile to analyse it. That's our foundation — next we'll walk through what defines each of those four segments.