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

Let’s start with the en route requirements for a multi-engine Class B aeroplane. I want to walk you through exactly what the regulations demand, because this is where the multi-engine aeroplane really separates itself from the single-engine machine. First, the definition of the en route stage. 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 moment you climb through 1500 ft above your departure field, you are officially en route, and you stay en route until you descend to 1000 ft above the destination. That is the window we are talking about. Now, where do these rules live? As with all the other requirements we have come across, the en route and descent requirements are written in EU-OPS and incorporated into CAP 698. EU-OPS is the European operating rules, and CAP 698 is the Civil Aviation Publication that brings those performance requirements together for the examiner and the operator. If you open CAP 698, section 3, page 17, you will see the en route requirements at the top. The first sentence simply reminds you what the en route stage of flight is — that 1500 ft to 1000 ft definition I just gave you. Then come the actual requirements, and I want to read the key one to you carefully, because every word matters. 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 sentence piece by piece, because it is dense. First, "the meteorological conditions expected for the flight." That means you are not planning for a clear blue sky — you must account for the actual weather you expect, including cloud, wind, and temperature. The performance must hold in those conditions. Second, "in the event of the failure of one engine." This is the core scenario. One engine has failed. The remaining engines — and note the plural, because a multi-engine aeroplane may have more than two — must be operating within the maximum continuous power conditions specified. Maximum continuous power is the highest power setting the engine can sustain indefinitely without damage, as opposed to a take-off power that is time-limited. So after the failure, the good engines run at maximum continuous power, and that is the assumption for the whole en route requirement. Third, the capability. With that one engine failed and the others at maximum continuous power, 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 is a floor — a minimum safe altitude — written in the operations manual, and the aeroplane must be able to stay at or above it. Fourth, the destination of that continued flight. The aeroplane must be able to get to a point 1000 ft above an aerodrome at which the performance requirements for landing can be met. So it is not enough to just keep flying — you must be able to reach an aerodrome, climb or maintain to 1000 ft above it, and be in a position where the landing performance requirements can actually be satisfied. Now, here is the key contrast with the single-engine aeroplane. This requirement is almost identical to the single-engine aeroplane requirement, with one crucial difference. The single-engine aeroplane, after engine failure, has to be capable of landing in a suitable field — a forced landing in open terrain. The multi-engine aeroplane must achieve a higher performance level. It must continue flight and land at a suitable airfield. So in the event of engine failure, the multi-engine aeroplane should have a level of performance such that it can, even with an engine failed, get to an airfield to land. That is the whole point of having more than one engine — redundancy that buys you the ability to reach a proper runway rather than a field. And the excerpt ends by noting that, as with other requirements we have covered, the en route requirements — and that sentence is cut off, but the point is that these en route rules follow the same regulatory pattern you have seen elsewhere in the syllabus. Let me also point you to the figures, because they show the obstacle clearance climb profile. shows the profile when there is no cloud, and shows the profile when there is cloud. The difference matters because cloud affects how the obstacle clearance is applied — but that is the climb side of the picture, and it ties directly into the en route capability we have just discussed. So, to summarise the en route requirement in one line: with one engine failed and the rest at maximum continuous power, in the expected weather, the multi-engine Class B aeroplane must be able to stay at or above the minimum safe altitude and reach an aerodrome where it can land, 1000 ft above it. That is the standard.