All right, let's pick this up right where the en-route requirements leave off — Page 349, Lesson 431

All right, let's pick this up right where the en-route requirements leave off. We've established that after an engine failure, you need to be able to get to an airfield to land. But the regulation isn't just a vague wish—it has specific compliance rules, and they're very similar to the ones we saw in the single-engine en-route lesson. Here's the core problem: to prove you can always reach an airfield, you need to know two things. First, the descent range with one engine inoperative—how far you can glide or descend with one engine out. Second, the one engine inoperative cruise range—how far you can fly level with one engine out. Once you've calculated both, you plot a flight track that guarantees an airfield is always within the total one engine inoperative descent distance. That's the goal. Now, the compliance rules are all about how you calculate that descent range. There are two of them, and they're strict. The first rule: The aeroplane must not be assumed to be flying at an altitude exceeding that at which the rate of climb equals 300 ft/min with all engines operating within the maximum continuous power conditions specified. Let me unpack that. You cannot claim extra altitude to gain extra range. Specifically, you can't assume you're flying higher than the altitude where your rate of climb—with all engines working, at maximum continuous power—is exactly 300 feet per minute. That 300 ft/min altitude is your ceiling for planning purposes. You can't use any altitude above that to stretch your descent distance and make it look like you can reach an airfield when you really couldn't. The second rule: The assumed en route gradient with one engine inoperative shall be the gross gradient of descent or climb, as appropriate, respectively increased by a gradient of 0.5%, or decreased by a gradient of 0.5%. So, you take the gross gradient—that's the raw, unadjusted slope of your descent or climb with one engine out. Then you apply a 0.5% penalty. If it's a descent, you increase the gradient by 0.5%—making it steeper, which is worse for range. If it's a climb, you decrease the gradient by 0.5%—making it shallower, which is also worse. Either way, you're making your performance look worse than the gross figures suggest. That's the safety margin built into the regulation. So, to tie it together: the first rule caps your starting altitude at the 300 ft/min point, and the second rule worsens your gradient by half a percent. Both work together to ensure you don't overestimate your ability to reach an airfield after an engine failure. The whole point is conservative planning—you assume the worst, so that in reality, you always have a margin. Let's look at the obstacle clearance climb profiles to see how this plays out visually. shows the profile when there's no cloud, and shows it when there is cloud. These figures illustrate how the gradient and altitude assumptions we just discussed fit into the actual climb path you'd plan. That's the heart of it: the compliance rules force you to plan conservatively, using the 300 ft/min altitude cap and the 0.5% gradient penalty, so your en-route track always keeps an airfield within reach.