First, you'll see abbreviations like A/P — that's Autopilot — Page 653, Lesson 753

This is the index of the book — the map of everything we're going to cover. Let me walk you through what's here, because the way this index is laid out tells you a lot about the structure of the course. First, you'll see abbreviations like A/P — that's Autopilot. And GA — that's Go-Around. So A/P GA Pitch control and A/P GA Roll control are the autopilot's pitch and roll commands during a go-around, both on page 383. Then A/P Go-around Mode is the full mode itself, also page 383. Next, Apparent wander — this is a gyroscopic term, page 156. It's the apparent movement of a gyro's axis due to the Earth's rotation. You'll see it again at pages 142, 157, and 235. APPR is the abbreviation for Approach. You'll see Approach (APP) mode on pages 381 and 384, and Approach/Land Mode on page 374. These are the autopilot's approach and landing modes. APU — that's the Auxiliary Power Unit, page 29. That's the small gas turbine that provides electrical and pneumatic power on the ground. ARINC — this is a big one. It stands for Aeronautical Radio Incorporated, page 318. This is the organization that sets the standards for avionics data buses — how instruments talk to each other. Arithmetic Logic Unit — page 308. That's the part of a computer's CPU that performs arithmetic and logic operations. This is in the section on digital computers. ARM Mode — page 395. This is an autopilot mode where a function is armed — ready to engage — but not yet active. ARPT — that's Airport, page 286. Artificial Horizon (AH) — page 169. This is the primary attitude indicator — the instrument that shows you the aircraft's pitch and roll relative to the horizon. ASI — that's Airspeed Indicator, page 41. And you'll see ASI ACCURACY TOLERANCE on page 45 — the allowable error in the airspeed reading. And ASI Colour Coding — the coloured arcs on the airspeed indicator — also page 45. A Single Axis System — page 356. This is an autopilot that controls only one axis — typically roll. Aspirator — page 29. This is a device that creates suction — used in the vacuum system that drives gyroscopic instruments. Assembly Language — page 309. This is a low-level programming language — one step above machine code. Then you have the go-around sequence — this is a critical one. Look at these entries: - At 45 Feet Gear Altitude (GA)/ 50 ft RA — page 382. That's the point where the gear altitude is 45 feet, or radio altitude is 50 feet. - At 1500 Feet Radio Altitude (RA) — page 382. - At about 1 foot GA — page 382. - At about 5 feet GA — page 382. These are the trigger points in the autopilot's go-around and landing sequence. GA here is Gear Altitude — the height of the landing gear above the ground. RA is Radio Altitude — measured by the radio altimeter. So the autopilot performs specific actions at each of these heights during the approach and flare. And finally, ATC — that's Air Traffic Control — the entry is cut off, but you'll encounter it throughout the book. Now, here's the key thing about this index. Look at the page numbers — they're not sequential. You have page 41, then 45, then 120, 121, 142, 156, 157, 169, 235, 286, 308, 309, 318, 319, 356, 374, 380, 381, 382, 383, 384, 395. This tells you the book is organised by topic, not by page order. The instrumentation chapters come first — air data, gyroscopes, compasses — then the digital systems, then the autopilot and flight management systems. So when you're studying, this index is your navigation tool. If you need to look up a specific instrument or mode, you find it here, and it tells you exactly where to go. That's the purpose of this page — it's the roadmap for the entire course.