Single-engine Class B Aircraft - Take-off — Page 302, Lesson 376

We're starting a new topic now: single-engine Class B aircraft take-off performance, straight out of the CAP 698 methodology. Let me walk you through the first key correction and how the data is presented. First, the slope correction. At the top of page 2, section 2, under the table, point "d" tells you what to do if the runway has a slope. The rule is: you must increase the take-off distance by 5%, or multiply by a factor of 1.05, for every 1% of upslope. So if you have a 2% upslope, you take your calculated distance and multiply it by 1.05 twice — that's a 10% increase overall. The upslope makes the aeroplane work harder to accelerate, so the distance grows. But here's the critical part: the rule states that no factorization is permitted for downslope. That means if the runway slopes downwards, you apply no correction factor at all. You don't reduce the distance. Why? Because a downslope actually decreases the take-off distance — gravity helps you accelerate. But the regulation deliberately ignores that benefit. The reason is safety: by not crediting the downslope, you build a little extra margin into your take-off distance calculation. So the calculation stays conservative. Now, how is the take-off distance required actually presented? It's usually given in graphical form. Look at Figure 2.1 on page 3 of section 2 in CAP 698. The title of that graph tells you it's for calculating the gross take-off distance with no flaps selected. If you need a different flap setting, you'll have to consult a different graph — this one is specific to the no-flap configuration. Pay close attention to the associated conditions at the top of the graph, especially the power and flap settings. And notice this: the graph assumes a runway that is paved, level, and dry. Those are the baseline conditions. If your actual runway differs from any of those — say it's wet, or grass, or sloped — then you must apply corrections to the values the graph gives you. We touched on those correction factors earlier. There's also a small box in the middle of the graph that highlights the rotation speed and the screen height speed for different weights. These are the speeds used to construct the graph, so you must adhere to them accurately. If you rotate at the wrong speed, the graph's assumptions no longer hold, and your calculated distance becomes invalid. So those speeds are not optional — they're part of the graph's construction. That's the core of it: the slope rule with its 5% per 1% upslope and the no-downslope credit, plus the graphical presentation with its fixed conditions and mandatory speeds.