Look at the entries here — Page 655, Lesson 763

This is the index of the book — the alphabetical list of topics and the page numbers where they appear. I want to walk you through what this tells you, because learning to read an index is part of learning to use your reference material properly. Look at the entries here. We have "DH REF" on page 284, "DH RST" on pages 284 and 286, and "DH SEL" on page 284. These are all related to Decision Height — the altitude at which you must decide whether to continue an approach or go around. The REF, RST, and SEL are the reference, reset, and select functions for that setting on the instrument. Then we have "Digital" appearing on pages 7, 98, and 307. That's a broad topic. Under it, "Digital Computer Components (Hardware)" on page 308, and "Digital Computers" on page 307. Notice the hierarchy — the general term first, then the specific sub-topics indented beneath it. We also have "Digital Flight Guidance System (DFGS)" on page 311 — that's the autopilot and flight director system working together. "Digital Read-out" on page 266. "Digital to Analogue Conversion" and "Digital to Analogue Converter" both on page 311 — that's the process of turning the computer's digital signals into the analogue signals that drive the instrument needles. Now look at the compass entries. "Direct Indicating Magnetic Compass" on page 119, "Direct Reading Compass" on page 211, "Direct Reading Magnetic Compass" on page 204, and "DRMC" — which is the abbreviation for that Direct Reading Magnetic Compass. These are all different names for essentially the same basic instrument, and the index shows you where each term is discussed. We have "Directional Gyro Indicator" on pages 153 and 211, and "Direction indicator (DI)" on page 153 — the DI is the short name for that same gyroscopic heading instrument. "Directive Force" on page 112 — that's the magnetic force that pulls the compass needle toward north. "Direct Reading" on page 26. Then "Displacement Gyros" on page 144 — these are gyroscopes that measure by how much they're displaced from their reference position, rather than by rate of movement. We have "DISPLAY" on page 278, "Display Panels" on page 239, and "Display Units" on page 282 — the screens and units that present the information to you. "Distance and Time" on page 245. "DME" on page 291 — that's Distance Measuring Equipment. "DMU" on page 499 — that's the Data Management Unit. "Downlink" on page 318 — that's the transmission of data from the aircraft to the ground. "Drain Holes" on page 14 — those are the small openings in the pitot-static system that let moisture escape. "Drift" on pages 141 and 256 — that's the angular difference between your heading and your track. "Drift Rate Calculations" on page 163. So what you're looking at is the map of the entire book. When you're studying, you use this to find where a topic is covered. When you see "DH REF . . . 284", that tells you the Decision Height Reference function is explained on page 284. When you see "Digital to Analogue Converter . . . 311", you know that's where the conversion process is detailed. The pattern to notice is the indentation. A topic that's indented under a broader term is a sub-topic of that term. "Digital Computer Components (Hardware)" belongs under "Digital Computers". "Drift Rate Calculations" belongs under "Drift". This structure tells you how the subjects relate to each other. And the page numbers — some entries have one page, some have two or three. That tells you where the main discussion is, and where the topic is mentioned again in passing. "Directional Gyro Indicator" on 153 and 211 — the main treatment is on 153, and it's referenced again on 211. That's the index. It's your navigation tool for the whole book. When you're revising a topic, you come here first to find every page that discusses it.