Right at the top, under A, we have Abbreviations on page 11 — Page 535, Lesson 646

We're looking at the index of the Oxford ATPL Mass and Balance and Performance book. This is the map of the whole subject, and I want to walk you through what it tells us about the territory we're about to cover. Right at the top, under A, we have Abbreviations on page 11. That's where you'll find the shorthand for all the key terms. And you can already see some of them listed here: ACN, ASD, ASDA, ASDR, AUW. These are the acronyms you'll be using constantly in performance work. Let me decode those for you now, because they're fundamental. ACN stands for Aircraft Classification Number — that's a number that tells you how a particular aircraft interacts with a pavement, used for runway strength. ASD is Accelerate-stop Distance — the distance required to accelerate to a decision speed and then stop if you abort. ASDA is Accelerate-stop Distance Available — what the runway actually offers you. ASDR is Accelerate-stop Distance Required — what the aircraft needs. And AUW is All-Up Weight, the total weight of the aircraft at any moment. Now, notice the distinction the index is drawing. We have "Accelerate-stop Distance Available" on pages 3 and 23, and separately "Accelerate-stop Distance Requirements" on page 217. That's a critical split in this subject: what the aerodrome provides versus what the aircraft demands. You'll be comparing those two constantly. Then we have a cluster of definitions on page 3 — the foundational terms. Absolute Ceiling, Aerodrome, Aerodrome Elevation, Aerodrome Reference Point, Aerodynamic Ceiling, Aeroplane, Aircraft, Aircraft Classification Number, Airframe, Air Minimum Control Speed, Alternate Airport. Page 3 is where the book pins down the precise meaning of each of these, because in performance work, a word like "aeroplane" versus "aircraft" has a specific regulatory meaning you must respect. Let me give you a few of these now. Absolute Ceiling is the altitude at which the aircraft can no longer climb — the maximum altitude achievable. Aerodynamic Ceiling, on page 325, is related but distinct — it's the ceiling set by aerodynamic limits rather than engine power. Aerodrome Elevation is the elevation of the highest point of the landing area. Aerodrome Reference Point is the designated geographical position of the aerodrome. Air Minimum Control Speed is the minimum speed at which the aircraft can be controlled in the air with one engine inoperative — that's a safety-critical number. Then we move into the performance physics. Aerodynamic Drag on page 28, Air Density on page 29, Airframe Contamination on page 31. Drag is the resistance the air offers to the aircraft's motion. Air density is how thick the air is — it directly affects both lift and engine performance. Airframe Contamination is when the aircraft's surfaces get dirty — frost, ice, snow — and that degrades performance, which is why it gets its own entry. We also have Air Gradient on page 65 — that's the slope of the climb path. Angle of Attack on page 4 — the angle between the wing's chord line and the relative airflow. Angle of Climb on page 43 — the angle of the flight path during a climb. Angle of Descent on page 93 — the corresponding angle during descent. And notice Anti-skid Inoperative on page 294 — that's a failure condition. When the anti-skid system, which prevents wheel lock-up during braking, is not working, your stopping performance changes, and the book treats that as a separate case you must account for. So what this index is really showing you is the structure of the whole subject: definitions first, then the physics of drag and density, then the climb and descent geometry, then the runway distance concepts, then the failure conditions. That's the skeleton we'll be building on.