Single-engine Class B - En Route and Descent — Page 317, Lesson 395

Let’s pick this up right where the forced-landing rule left off, because there’s one final twist the regulations force on us. We’ve been working with a gradient of descent of 7% in our example. But EU-OPS 1.542 (b) (2) — that’s the specific paragraph of the European operating rules — says that to comply with the safe forced landing rule, the assumed en route gradient shall be the gross gradient of descent, increased by a gradient of 0.5%. So the regulations will not let us use that 7%. They force us to add half a percent, giving us 7.5%, as shown in Figure 9.4. Now, two terms here you need to lock in. The 7% — the actual performance the aeroplane can genuinely achieve — that’s the gross gradient. But the 7.5% — the deteriorated value the regulations insist we use — that’s the net gradient. So the net gradient is always the gross gradient plus 0.5%. And notice what this does: it lowers the assumed descent performance of the aeroplane. We’re deliberately assuming the aeroplane performs worse than it really does. Why does that matter? Because it shrinks the glide distance. With the gross gradient the aeroplane might glide 23.5 NM after an engine failure. But with the net gradient forced on us, the glide distance reduces to 22 NM. So even though the aeroplane could physically reach 23.5 NM, we must assume it only glides 22 nautical miles. That’s the conservative assumption baked into the rule. Now look at Figure 9.5. Because the glide range has shrunk, the circles around each safe forced landing area must reduce to a radius of 22 NM. And that means the planned track has to change slightly. At every point along the route, the aeroplane must be no further than 22 NM from a safe forced landing area. The track shown in Figure 9.5 meets the entire set of requirements as stated in EU-OPS. Now, where do you actually find all this in the real documentation? I mentioned earlier that CAP 698 — that’s the Civil Aviation Publication that contains the en route regulations — has these rules scattered through the manual, not conveniently collected in one place. So let me point you to exactly where. On page 1 of section 2, in the general requirement paragraph, point c) is the regulation about ensuring the aeroplane is not operated unless surfaces are available which permit a safe forced landing to be carried out in the event of engine failure. That’s the overarching rule. But the other regulations about complying with this rule are a few pages further on. You’ll find the remaining en route requirements at the bottom of page 8 of section 2. And there are two key requirements there. The first states that the aeroplane may not be assumed to be flying above the altitude at which a rate of climb of 300 feet per minute can be achieved. So we cap the assumed altitude at the point where the aeroplane can still climb at 300 feet per minute. Underneath that rule, you’ll see the requirement we’ve just been discussing — that the net gradient of descent, in the event of engine failure, is the gross gradient plus 0.5%. Now, one more thing before we move on. Although the concepts of range and endurance have been covered in a previous lesson, it’s important for the pilot to be able to use the information in the aeroplane flight manual so that he may calculate the range and endurance of the aeroplane. In the aircraft manual there are — and that’s where we’ll pick up next, the actual data in the flight manual that lets you do these calculations.