Autopilot — Page 381, Lesson 463

We're starting a brand-new topic now: the autopilot, and how it fits into the wider aircraft systems. Let's begin with the big picture. The autopilot can form part of the overall Flight Management System, which we call the FMS. Now, this same system might be given different names depending on the aircraft manufacturer. It may also be designated the Automatic Flight Control System, or AFCS, or the Flight Management and Guidance System, which is the FMGS. So when you hear any of those three acronyms—FMS, AFCS, FMGS—understand they're all referring to this same integrated family of systems. What does this system actually do? It provides manual or automatic modes of control throughout the entire flight envelope, from take-off to landing and roll-out. That's a key phrase: the entire flight envelope. It means the system is designed to assist or take over control at every phase of flight, from the moment you start the take-off roll, all the way through the climb, cruise, descent, approach, landing, and even the roll-out on the runway after touchdown. Now, a critical design principle here is that all the subsystems of the FMS are fully integrated. They don't work in isolation; they share information and work together as one cohesive unit. And because this system is so critical to the safe operation of the aircraft, it has levels of redundancy to achieve a high level of reliability. Let me explain what redundancy means in this context. Redundancy is accomplished by providing two or more systems of each type, so that a failure of one system will not affect the operation of the complete system. In other words, if one computer or one sensor fails, there's a duplicate standing by to take over, and the overall system keeps working normally. This is how we achieve that high reliability—by building in backups. Now, before we even get airborne, there's a critical ground procedure. The AFCS and FMS will be checked completely during the preflight checks. During these checks, all the automated systems will be engaged, tested, and their various safety devices tested. So we don't just switch it on and hope it works—we actively engage every automated system, run tests on them, and verify that all the safety devices function correctly. Additionally, the FMS will be checked for the correct information, and any additional information will be entered. This means the pilots verify that the navigation database, the flight plan, and all the relevant data loaded into the system are correct, and they input any new or missing information before departure. So to summarize what we've covered: the autopilot is part of a larger, integrated system called the FMS, which may also be called the AFCS or FMGS. It provides control throughout the entire flight envelope, relies on redundancy—multiple systems of each type—to ensure reliability, and undergoes a complete check during preflight, where all systems are engaged, tested, and updated with correct information. That's the foundation. Next, we'll move into the specifics of how the autopilot itself works and the components that make it function.