Class A Aircraft - Take-off — Page 372, Lesson 454

Let’s start with the big picture. The specimen aeroplane we use for Class A performance is the Boeing 737-400 series. And just to remind you what Class A actually means: it’s any multi-engine jet, or any turbo-propeller aeroplane with a mass of more than 5700 kilograms, OR 10 seats or more. So if you’ve got a turbo-prop with, say, 12 seats, it’s Class A. If it’s a jet with two engines, it’s Class A. That’s the definition we’re working with. Now, because these aeroplanes carry a lot of passengers and fly fast, they must have the highest safety standards. And those standards are enforced in two ways. First, by the certification requirements, which are laid down in CS-25. Second, by the operational requirements, which are laid down in EU-OPS 1. So CS-25 is about certifying the aeroplane type itself, and EU-OPS 1 is about how the operator actually flies it. Here’s the key difference that makes Class A special compared to Class B. The operational requirements state that for Class A aeroplanes, engine failure must be considered for ALL stages of flight. For multi-engine Class B aeroplanes, engine failure was not assumed below 300 feet. So in Class B, below 300 feet you could assume both engines were fine. In Class A, you must assume an engine can fail at any point, including right at the start of the take-off roll. That adds an extra dimension to understanding and assessing the aeroplane’s performance, and it’s why we’re going to introduce a lot of new terms and concepts you’ll need to become very familiar with. Now let’s look at the operational requirements themselves. EU-OPS 1.490 states that an operator must ensure the take-off mass does not exceed the maximum take-off mass as published in the aeroplane flight manual. So there’s a published limit in the AFM, and you can’t go above it. When calculating that maximum take-off mass, two distances come into play. First, the accelerate-stop distance must not exceed the accelerate-stop distance available. Second, the take-off distance must not exceed the take-off distance available. Let me unpack those terms. The accelerate-stop distance is the distance required to accelerate to a certain speed and then stop safely if you abort the take-off. The accelerate-stop distance available is the physical runway length you have for that manoeuvre. Similarly, the take-off distance is what the aeroplane needs to get airborne and clear an obstacle, and the take-off distance available is the runway length provided. So the rule is simple: what you need must not exceed what you have. I want to pause there, because this is the foundation for everything that follows in Class A take-off performance. The whole point is that engine failure is assumed at the worst possible moment, and we must have enough runway to either stop or continue, whichever we choose.