2000’ or 150 seconds after lift-off and the command bars will — Page 348, Lesson 403

We're in the middle of the take-off sequence now, right after lift-off. Let me pick up with what happens at 2000 feet or 150 seconds after lift-off — whichever comes first — and the command bars will automatically appear. That's the moment the Flight Director takes over the pitch control. So here's the sequence. The FD provides pitch commands after lift-off. It continues to command 15 degrees nose-up pitch until sufficient climb rate is achieved. Then it switches to commanding pitch to maintain the MCP speed plus 20 knots indicated airspeed. That speed — the MCP speed plus 20 — is calculated and set during the pre-flight. Now, next: when either autopilot is engaged, or when the MCP speed selector is rotated, that 20 knots IAS is added automatically to the MCP IAS display. So you don't have to dial it in manually — the system does it for you. Now for roll. The FD roll commands keep the wings level from take-off mode engagement all the way through to the take-off climb-out. To terminate the take-off mode below 400 feet radio altitude, both of the FD switches must be turned off. Above 400 feet RA, you can terminate the take-off mode by selecting other FD pitch modes, or by engaging an autopilot. Let me explain what happens when you engage an autopilot after an FD take-off. It automatically engages the autopilot and FD in LVL CHG — that's level change — for pitch, and HDG SEL — heading select — for roll. Now, if the FD mode had been changed from TO/GA to LNAV, HDG SEL, or VOR/LOC, the autopilot initially engages in the same roll mode as the FDs. And when LVL CHG engages, the MCP IAS/MACH display and the airspeed cursors change to V2 plus 20 knots. Now, engine failure during take-off — this is critical. If an engine fails before reaching V2 speed, the FD pitch commands are referenced to V2. If the engine failure occurs after reaching V2, but less than V2 plus 20 knots, the reference speed is that at which the engine failure occurred. If the failure occurs at or above V2 plus 20 knots, then V2 plus 20 knots is the commanded speed. And here's the key limitation: reference speed is never less than V2 for the current flap setting. Roll control remains the same as for all engines operating. Now let's move to the cruise phase — altitude acquire and altitude hold. In cruise we require to fly at a constant level, and the FDS — the Flight Director System — can help achieve this. Signals from the ADC — that's the Air Data Computer — through the FDS mean that when we are at the selected level, the FD command bars indicate a neutral position. If the aircraft were to deviate above the desired altitude, the command bars would indicate a pitch down command, and vice versa — if you deviate below, you get a pitch up command. Let me show you the mode annunciators and the altitude acquire/hold behavior on the PFD. So to summarize the key numbers: 2000 feet or 150 seconds, 15 degrees nose-up, MCP speed plus 20 knots, 400 feet radio altitude for the take-off mode termination threshold, and V2 as the never-below reference speed for engine failure. Those are the numbers you need to hold onto.