They're related but not the same thing — Page 456, Lesson 581

This is the index page of the book — the "R" section, listing every topic that starts with the letter R and the page where you'll find it. I want to walk you through it, because even an index teaches you the structure of the powerplant syllabus. Let's start with the propeller family. You have Propeller itself at pages 25 and 163, Propeller Control Unit — PCU at 175, Propeller Efficiency at 167, and Propulsive Efficiency at 211. Note the distinction: propeller efficiency is about how well the propeller converts shaft power into thrust power, while propulsive efficiency is the broader term for how efficiently the whole propulsion system converts energy into forward motion. They're related but not the same thing. Then we have the engine types. Pure Straight Turbojet Engine at 206 — that's the simplest jet, no bypass, all the air goes through the core. Radial Engine at 13 — the piston engine with cylinders arranged in a circle around the crankshaft. And PV Diagram at 19 — that's the pressure-volume diagram showing the thermodynamic cycle of the engine. Now the piston engine mechanical parts. Rings at 26 — the piston rings that seal the combustion chamber. Rocker Arms at 28 and Rocker Pad at 28 — the rocker arm is the lever that opens the valves, and the rocker pad is the surface where it contacts the valve stem. Reduction Gearbox at 31, Reduction Gearing at 182, and Reduction Gear Types at 182 — all about gearing the propeller down from engine speed. The cooling system: Radiator at 58 and Refrigeration Ice at 118 — the radiator cools the engine coolant, and refrigeration ice is the ice that forms on the evaporator of an air conditioning or refrigeration system. Performance terms: Rated Altitude, Rated Boost, Rated Power, and Rated rpm — all at page 145. These are the manufacturer's certified limits: the altitude, the boost pressure, the power, and the rpm at which the engine is rated to operate. The physics: Reaction Law at 5 — Newton's third law, for every action there's an equal and opposite reaction, the basis of thrust. Resistance at 9 — the force opposing motion. Ram air terms: Ram Air Turbines at 354 — the little propeller-driven generator that deploys in an emergency to provide hydraulic or electrical power. Ram Effect at 219 and Ram Pressure Recovery at 219 — the pressure rise from the forward speed of the aircraft compressing the incoming air. Ram Recovery at 318 — recovering that ram pressure in the intake. Reverse thrust: Reverse at 168, Reverse Pitch at 176 — for propellers, changing blade angle to push air forward. Reverse Thrust at 327, Reverse Thrust lever at 329, and Reverse Thrust Warning Lights at 328 — the jet engine thrust reverser system, the lever that deploys it, and the warning lights that tell you it's armed or deployed. Finally, the turbine section: Rotor Blades at 228 and 235 — the rotating blades in the compressor and turbine. rpm Limiter at 378 — a device that prevents the engine from exceeding its maximum rpm. And Rundown Time at 359 — the time it takes for the engine to spool down to a stop after shutdown. That's the whole R section of the index. It's a map of where everything lives in the powerplant book.