The whole take-off flight path starts once the take-off is complete — Page 426, Lesson 526

Right, let's pick this up with the take-off climb segments for a Class A aeroplane. We're looking at Figure 16.1, which shows the four distinct segments of the take-off climb path. Let's start with the reference point. The whole take-off flight path starts once the take-off is complete. That means at 35 feet above the runway, with the aeroplane at V2 — that's the take-off safety speed — and with one engine deemed inoperative. That 35-foot height is called the screen, and it marks the start point of segment 1. Now, the objective at this point is to climb as expeditiously as possible. That's difficult, because of the lack of excess thrust. The gear and flaps are creating a large amount of drag, and we've lost one engine. So the strategy is to retract the gear and flaps as soon as possible. But retracting flaps at low speeds close to the ground is dangerous, so the only option is to retract the gear. Once the gear is up and locked, the first segment is finished. During this segment, the steady gradient of climb must be positive — greater than zero percent. Segment 2 starts at the end of segment 1, when the gear is up. The objective now is to retract the flaps. However, flap retraction is not permitted below 400 feet. So the pilot's action is simply to climb, at no less than V2, until 400 feet is reached. Once 400 feet is reached and flap retraction can commence, segment 2 ends. Because the main source of drag — the gear — has been removed, the minimum gradient requirement is more severe here: no less than 2.4 percent. Segment 3 starts at or above 400 feet, and this is the flap retraction and acceleration segment. Retracting the flaps will increase the stall speed, which reduces the aeroplane's safety margin. So the aeroplane must accelerate during flap retraction, from V2 to the zero flap speed, and then to the final take-off speed. The final take-off speed is also called the final segment speed, and it's intended to be the one-engine-inoperative best angle of climb speed. Once this acceleration is done, thrust can be reduced from maximum take-off thrust — that's TOGA — to maximum continuous thrust, MCT. Maximum take-off thrust is limited to only 10 minutes, so acceleration and flap retraction must be complete by then. We require excess thrust to climb or accelerate, and since our priority in this segment is to accelerate, there is no minimum climb gradient required. Now, looking at the figure, you can see the gradients for each segment. For segment 1, the gradient must be greater than zero percent. For segment 2, it's greater than 0.3 percent for 4 engines, 0.5 percent for 3 engines, and 0.5 percent for 2 engines — wait, let me re-read that. Actually, the figure shows: for segment 2, the gradient is greater than 0.3 percent for 4 engines, greater than 0.5 percent for 3 engines, and greater than 0.5 percent for 2 engines. Hmm, let me look again. Actually, looking at the figure more carefully: Segment 1 shows "> 0%" for the gradient. Segment 2 shows "≥ 2.4%", "≥ 2.7%", and "≥ 3.0%" for 4, 3, and 2 engines respectively. Segment 3 shows "≥ 1.2%", "≥ 1.5%", and "≥ 1.7%". And segment 4 shows "> 0.3%", "> 0.5%", and "> 0.5%" — wait, I need to be careful here. Let me re-read the figure data. The figure shows: Segment 1: Gradient > 0%, starts at 35 ft with V2, action is "Select Gear Up", ends when gear is up. Segment 2: Gradient ≥ 2.4% (4 engines), ≥ 2.7% (3 engines), ≥ 3.0% (2 engines). Starts at gear up, climbs to > 400 ft AGL at V2, action is "Climb to > 400 ft AGL", ends at 400 ft. Segment 3: Gradient ≥ 1.2% (4 engines), ≥ 1.5% (3 engines), ≥ 1.7% (2 engines). Starts at > 400 ft AGL, speed goes from V2 to VZF to VFTO, action is "Retract Flaps, Accelerate to VFTO, Set MCT", ends at 1500 ft AGL. Segment 4: Gradient > 0.3% (4 engines), > 0.5% (3 engines), > 0.5% (2 engines). Starts at 1500 ft AGL, speed is VFTO, action is "Climb to 1500 ft AGL" — wait, that doesn't make sense. Let me re-read. Actually, segment 4 starts at 1500 ft AGL with VFTO, and the action is to climb. The gradient requirements are > 0.3% for 4 engines, > 0.5% for 3 engines, and > 0.5% for 2 engines. So to summarize the gradients: - Segment 1: > 0% (positive gradient required) - Segment 2: ≥ 2.4% (4 engines), ≥ 2.7% (3 engines), ≥ 3.0% (2 engines) - Segment 3: ≥ 1.2% (4 engines), ≥ 1.5% (3 engines), ≥ 1.7% (2 engines) - Segment 4: > 0.3% (4 engines), > 0.5% (3 engines), > 0.5% (2 engines) Now, segment 4 — the excerpt cuts off before fully describing it, but from the figure we can see it starts at 1500 ft AGL with the flaps up, at VFTO, with MCT set. The action is to climb to 1500 ft AGL — wait, that's the end point. Let me re-read the figure. The figure shows segment 4: "Flaps Up, VFTO, MCT" with the action "Climb to 1500 ft AGL". So segment 4 starts at 1500 ft AGL and continues climbing. The gradient requirements are > 0.3% for 4 engines, > 0.5% for 3 engines, and > 0.5% for 2 engines. So the four segments are: 1. Segment 1: From 35 ft at V2, gear down, one engine inoperative. Retract gear. Gradient > 0%. 2. Segment 2: Gear up, climb at V2 to 400 ft. Gradient ≥ 2.4% (4 engines), ≥ 2.7% (3 engines), ≥ 3.0% (2 engines). 3. Segment 3: From 400 ft, retract flaps, accelerate from V2 to VZF to VFTO, set MCT. Gradient ≥ 1.2% (4 engines), ≥ 1.5% (3 engines), ≥ 1.7% (2 engines). 4. Segment 4: From 1500 ft AGL, climb at VFTO with flaps up and MCT. Gradient > 0.3% (4 engines), > 0.5% (3 engines), > 0.5% (2 engines). The key speeds are V2 (take-off safety speed), VZF (zero flap speed), and VFTO (final take-off speed, also called final segment speed — the one-engine-inoperative best angle of climb speed). The key thrust settings are TOGA (maximum take-off thrust, limited to 10 minutes) and MCT (maximum continuous thrust). The key heights are 35 ft (screen), 400 ft AGL (where flap retraction can begin), and 1500 ft AGL (where segment 4 begins). Let me make sure I've covered everything. The excerpt defines each segment, the figure shows the gradients for each engine configuration, and the key actions and speeds are all specified. I think we've got it all.