Multi-engine Class B - Landing — Page 368, Lesson 442

Let’s pick up with the landing side of multi-engine Class B aeroplanes. I want to walk you through the climb requirements you must meet when you’ve lost an engine and you’re going around, or when you’re demonstrating this capability for certification. Here’s the core rule: with the critical engine inoperative, the gradient of climb must not be less than 0.75% at an altitude of 1500 ft above the landing surface. Let me unpack that. The critical engine is the one whose failure is most adverse to the aeroplane’s performance and handling — the one that gives you the worst outcome if it quits. The gradient of climb is the ratio of vertical height gained to horizontal distance travelled, expressed as a percentage. So 0.75% means for every 100 units of horizontal distance, you climb 0.75 units vertically. And this must be achieved at an altitude of 1500 ft above the landing surface — that’s your reference height for this requirement. Now, the conditions under which this gradient must be achieved are very specific. You have the critical engine inoperative and its propeller feathered — feathered means the propeller blades are rotated to present minimum drag, so a dead engine doesn’t create excessive resistance. The live engine is set at maximum continuous power — that’s the highest power you can sustain for an extended period without damaging the engine. The landing gear, which we also call the undercarriage, is retracted. The flaps are retracted. And the climb speed must not be less than 1.2 VS1. VS1 is the stalling speed in a specified configuration — the speed at which the wing stops producing enough lift. So 1.2 VS1 means you must be climbing at least 20% above that stalling speed to maintain a safe margin. Notice something important here: for this certification and operational demonstration, the undercarriage and wing flaps are assumed to be retracted — the aeroplane is in a clean configuration. Why is the critical engine inoperative gradient requirement so much less than the all-engine climb gradient requirement, and why is the configuration cleaner? Because the failure of the critical engine results in an approximate 75% loss of climb gradient. That’s a huge hit. If the regulation set too high a level, it would impact the operational capability of the aeroplane in terms of its payload. Think about it — if the aeroplane can’t attain these gradients, you’d have to reduce the weight of the aeroplane to an amount that allows the gradient requirements to be met. That would mean carrying less payload, which hurts the operator. The term used to describe the maximum mass that can be carried and still attain the minimum gradient is called the Landing Climb Limit Mass. That’s your limiting weight for this climb condition. Now, a scope note: these climb gradient requirements are specific to aeroplanes in the normal, utility, and aerobatic category of more than 2722 kg. So they only represent a portion of the requirements for multi-engine Class B aeroplanes — not the whole picture. Let me also point you to a practical example. There’s a landing climb performance graph on page 19 of section 3 in CAP 698. This graph is for the baulked landing — in other words, an all-engine full power go-around. That’s when you abort the landing and climb away with all engines running at full power. But here’s the catch: the graph only gives you a rate of climb — that’s vertical speed, like feet per minute. To know if the aeroplane is achieving the minimum required gradient of 2.5%, you must convert the rate of climb into a gradient. An example of such a calculation is shown at the bottom of page 18 of section 3 in CAP 698. So you take the rate of climb, relate it to your ground speed, and express it as a percentage gradient. Now let’s move to the landing distance requirements under EU-OPS 1.550. The landing distance requirements for multi-engine Class B aircraft are the same as for single-engine aircraft — you saw those in Chapter 10. You can see these requirements in CAP 698 in the middle of page 17 of section 3. Here’s what EU-OPS 1.550 states: an operator must ensure that the landing mass of the aeroplane, for the estimated time of arrival, allows a full stop landing from 50 ft above the threshold within 70% of the landing distance available at the destination aerodrome and at any alternate aerodrome. Let me break that down. The landing mass is the weight of the aeroplane at the moment of landing, and you must consider it for the estimated time of arrival — the time you expect to arrive. A full stop landing means you come to a complete halt. You start from 50 ft above the threshold — that’s the point where you cross the runway threshold at 50 ft altitude. And you must be able to stop within 70% of the landing distance available. The landing distance available is the length of runway declared available and suitable for landing. So the aeroplane must be able to land within 70% of that distance. The factor to use for such calculations is 1.43 — that’s the reciprocal of 0.7, so you divide the landing distance available by 1.43, or equivalently, you ensure your required landing distance is no more than 70% of what’s available. So to tie it together: you have two distinct landing-related climb requirements — the critical engine inoperative gradient of 0.75% at 1500 ft, and the all-engine baulked landing gradient of 2.5% — plus the landing distance requirement under EU-OPS 1.550, which caps your landing mass so you can stop within 70% of the available distance. Each one protects a different phase of the approach and go-around.