Let’s pick this up right where the take-off flight path rules left off — Page 433, Lesson 533

Let’s pick this up right where the take-off flight path rules left off. We’ve just covered the vertical clearance margins — 35 ft normally, and the “or 50 ft whichever is greater” condition. Now I want to walk you through the bank angle limits that come with those clearances, because they’re tightly coupled. Here’s the rule: Up to 400 ft, bank angle may not be more than 15°. Above 400 ft, the limit relaxes to 25°. So think of 400 ft as the dividing line — below it, you’re restricted to a shallower 15° bank; above it, you can go to 25°. Now, EU-OPS 1.495 does allow operators to exceed those bank angles, but only under strict conditions. The operator must use special procedures, and those procedures must be approved by the relevant authority. The special procedures have to account for the gradient loss that results from such bank angles — meaning the steeper you bank, the more climb gradient you lose, and that loss must be quantified. And critically, these special procedures must be published in the aeroplane flight manual. What are the maximum bank angles these special procedures permit? Between 200 and 400 ft, you may go up to 20°. Between 400 and 1500 ft, you may go up to 30°. So notice the pattern — the special procedures give you extra bank capability, but only within those defined altitude bands, and only with the approved, published procedures in place. Now here’s a key interaction with the clearance margins. If any turn of more than 15° is required at any point in the take-off flight path, then the vertical clearance is increased from 35 ft to 50 ft. So the 15° bank angle isn’t just a limit — it’s also a trigger. Exceed it, and your obstacle clearance requirement jumps up to 50 ft. Let me pause there and make sure the logic is clear. The normal clearance is 35 ft. If you need to turn more than 15° anywhere in the take-off path, that clearance becomes 50 ft. And the bank angle limits themselves — 15° up to 400 ft, 25° above — can be exceeded only with those special approved procedures, which themselves cap at 20° between 200 and 400 ft, and 30° between 400 and 1500 ft. Now, working out the obstacle clearance capability of the aeroplane manually — that’s a long, lengthy calculation. There are so many points to bear in mind. So thankfully, most operators and manufacturers have produced rapid look-up tables or graphs to quickly let the pilot determine whether an obstacle in the take-off climb will be cleared by the relevant vertical margins following engine failure. These tables or graphs produce a mass. That mass is called the obstacle limit mass. It’s the maximum mass that will allow the aeroplane, in the event of engine failure, to clear the obstacle by the relevant vertical margin. So you enter the graph with your obstacle and your conditions, and it gives you a mass — if your actual take-off mass is at or below that obstacle limit mass, you clear the obstacle. If you’re above it, you don’t. There’s an example of this in Figure 16.2, which you can also find in CAP 698, on pages 36 and 37 of section 4. Now, notice that winds are included on the graph. This is important because obstacle clearance calculations must use ground gradients, and ground gradients are dependent on wind. Let me explain that — the aeroplane’s climb gradient relative to the ground is what matters for clearing an obstacle, and wind affects that. A headwind improves your ground gradient; a tailwind degrades it. And here’s the EU-OPS rule about wind that you must remember: when using winds to work out the ground gradient, only use 50% of headwinds and no less than 150% of tailwinds. So you don’t get full credit for a headwind — only half of it. And a tailwind is penalised — you must use at least one and a half times the reported tailwind. Now look at the slope of the headwind and tailwind lines on the graph. That slope shows that the graph applies the wind rule for you. So if you enter the graph with the actual reported wind, the graph corrects it automatically — you do not need to apply the 50% headwind or 150% tailwind rule yourself. The graph does that work for you. So to tie it all together: the take-off flight path has bank angle limits tied to altitude — 15° up to 400 ft, 25° above, with special approved procedures allowing up to 20° between 200 and 400 ft, and 30° between 400 and 1500 ft. Any turn over 15° raises your clearance from 35 ft to 50 ft. And to check obstacle clearance after engine failure, you use the obstacle limit mass from the graph, which automatically applies the wind rule — 50% of headwind, 150% of tailwind — so you enter with actual wind and get the correct ground gradient-based answer.