We're starting a fresh part of the book — the index — Page 389, Lesson 388

We're starting a fresh part of the book — the index. Now, an index isn't a lesson in itself, but it's a map of the whole syllabus, and I want to walk you through the entries we're looking at so you know exactly what each term means before we ever meet it in the chapters. This is your first exposure to a lot of professional terminology, so let's define them properly. We begin with the Control Display Unit, at page 270. That's the CDU — the pilot's interface panel in a Flight Management System, where you type in routes, altitudes, and performance data. Then the Control Segment, pages 307 and 310 — that's the ground-based part of the GPS system, the master control stations and monitoring stations that keep the satellites accurate. Control Zones, page 184, are the airspace around an airport where air traffic control has authority. Next, Cosecant Squared, page 211. That's a radar antenna beam shape — the beam is shaped so that the signal strength falls off with the cosecant-squared of the elevation angle, giving uniform ground coverage. Then the Course Deviation Bar, pages 125 and 126 — that's the vertical needle on an instrument that shows you how far left or right you are from your selected track. The Course Deviation Indicator, page 155, is the whole instrument that houses that bar. The Course Selector Knob, page 119, is the control you turn to set the desired course into that indicator. Critical Angle, page 27 — that's the angle of incidence beyond which a radio wave is no longer refracted back to Earth but passes through the ionosphere. Crosswind, page 92, is the wind component blowing across your track, not along it. Cruise, page 276, and its abbreviation CRZ, also page 276, is the phase of flight at constant altitude and speed between climb and descent. CVOR, page 116, stands for Conventional VOR — the standard VHF Omni-Directional Range, as opposed to the Doppler version. DAPS, page 237, is the Departure and Approach Procedures — the published routes for leaving and entering the terminal area. Data Link, page 234, is the digital communication system between aircraft and ground. DBVORTAC, page 116, is a Doppler VOR combined with a TACAN — a VORTAC installation using the Doppler principle. Dead Space, page 27, is the region where a radio signal is too weak to be received — often directly over a transmitter. Dead Time, page 187, is the interval after a transmission when a receiver cannot process a new signal. Decision Height, page 147, is the altitude on an approach at which you must decide to continue or execute a missed approach. Descent, page 277, is the phase of flight from cruise down to the approach. Designated Operational Coverage, abbreviated DOC, pages 98, 116, and 251, is the officially guaranteed area within which a navigation aid provides its specified service. Desired Track, page 261, is the exact path you intend to fly over the ground. DGPS, page 319, and Differential GPS, also page 319, are the same thing — a technique where a ground station broadcasts corrections to GPS receivers to improve accuracy. Dilution of Precision, page 318, is a measure of how satellite geometry affects GPS position accuracy. Directivity, pages 20 and 58, is an antenna's property of concentrating radiated energy in a particular direction. Directors, page 58, are the components that control that directivity. Distance Measuring Equipment, abbreviated DME, pages 148, 184, and 243, is the system that measures slant range from the aircraft to a ground beacon. The D-layer, page 25, is the lowest layer of the ionosphere, which absorbs high-frequency signals during the day. Now, one thing I want you to notice — the last entry, DME, lists pages 148, 149, and 17. That "17" is a typo in the index; the real coverage is on 148 and 149. Don't let a printing error throw you off. That's the whole block of D entries. You've now got the professional definitions for every one of these terms — CDU, Control Segment, DOC, DGPS, DME, and all the rest. When we hit them in the chapters, you'll already know what they mean.