Multi-engine Class B - En Route and Descent — Page 349, Lesson 430

I want to walk you through the multi-engine Class B performance requirements for the en route and descent stages. This is a new part of the book, so let's set the scene properly. First, let's define what the en route stage actually is. For a multi-engine Class B aeroplane, the en route part of the flight is considered to be from 1500 ft above the airfield from which the aeroplane has taken off, to 1000 ft above the destination airfield. So the en route phase doesn't start at the runway — it starts once you're 1500 ft above your departure field, and it ends when you're 1000 ft above your destination field. Everything between those two points is what we're regulating here. Now, as with all the other requirements we've come across, these en route and descent requirements are written in EU-OPS and incorporated into CAP 698. CAP 698 is the UK CAA document that consolidates these performance rules, and EU-OPS is the European regulation they come from. So when you're looking at the en route requirements, you'll find them in CAP 698, section 3, at the top of page 17. The first sentence in that section simply reminds you what the en route stage of flight is — exactly what I just described, from 1500 ft above take-off to 1000 ft above destination. Now here's the core requirement, and I want you to read it carefully because it's dense. An operator shall ensure that the aeroplane, in the meteorological conditions expected for the flight, and in the event of the failure of one engine, with the remaining engines operating within the maximum continuous power conditions specified, is capable of continuing flight at or above the relevant minimum altitudes for safe flight stated in the operations manual, to a point 1000 ft above an aerodrome at which the performance requirements for landing can be met. Let me unpack that for you. There are several conditions bundled into that one sentence. First, we're considering the meteorological conditions expected for the flight — so the weather you actually anticipate, not a standard day. Second, we're assuming the failure of one engine. Third, the remaining engines are operating within the maximum continuous power conditions specified. Maximum continuous power is the highest power setting an engine can sustain indefinitely without damage — it's not take-off power, which is time-limited, but the continuous limit you can hold for the whole flight. Given those conditions, the aeroplane must be capable of continuing flight at or above the relevant minimum altitudes for safe flight stated in the operations manual. So there's a floor — the minimum safe altitude — and you must stay at or above it. And you must be able to do this all the way to a point 1000 ft above an aerodrome at which the performance requirements for landing can be met. In other words, you need to reach a proper airfield, at 1000 ft above it, where you can legally and safely land. Now, this requirement is almost identical to the single-engine aeroplane requirement. The only difference is the key contrast I want you to hold onto. For a single-engine aeroplane, after engine failure, it has to be capable of landing in a suitable field — a forced landing in open terrain. But the multi-engine aeroplane must be capable of a higher performance level. It must continue flight and land at a suitable airfield. So the performance bar is higher: with one engine failed, the multi-engine aeroplane should have a level of performance such that it can still get to an airfield to land, rather than being forced down into a field. That's the heart of the en route requirement. The excerpt cuts off mid-sentence as it starts to say "however, as with other requirements we have covered, the en route requirements…" — so we'll pick that thought up next. But for now, the essential picture is this: one engine failed, remaining engines at maximum continuous power, expected weather, and you must maintain at or above the minimum safe altitude all the way to 1000 ft above a suitable landing aerodrome. Let me show you the obstacle clearance climb profiles, because they illustrate exactly what this looks like. shows the obstacle clearance climb profile if there is no cloud. shows the same profile if there is cloud. These figures show how the climb path must clear obstacles — and the presence of cloud changes the profile you must achieve. We'll dig into those profiles in detail as we continue.