Look at the structure — Page 125, Lesson 140

This is the table of contents for the mass and balance portion of your ATPL ground training series. I want to walk you through what's in here, because this index is actually a map of the entire subject you're about to learn. Look at the structure. The chapter opens with the regulatory foundation — EU-OPS 1, and specifically Subpart J, which is the section that governs mass and balance for commercial air transport operations. That's your legal baseline. Everything else in this chapter hangs off those rules. Then you have the core definitions. Design Limit Load and Design Ultimate Load — those are the structural strength limits the aircraft is built to. The Design Limit Load is the maximum load the structure is expected to withstand in normal service, and the Design Ultimate Load is the load it must survive without failure — typically 1.5 times the limit load. These matter because they set the absolute structural boundaries your mass calculations must respect. You'll see the Flight Manual referenced — that's the authoritative document for each aircraft type, containing the certified limits and performance data. And there's a section on Drag and Fuel Consumption, which connects your mass to how much fuel you burn. Now the heart of the subject — Centre of Gravity. You have the Datum, which is the reference point from which all arm measurements are taken. Then Centre of Gravity Limits — the forward and aft boundaries within which the CG must lie for safe flight. The index shows you the consequences of exceeding those: CG Outside the Forward Limit, CG Outside the Aft Limit, and the critical cases of CG ON FWD LIMIT and CG ON AFT LIMIT. Each of those conditions has distinct handling and stability implications you'll need to understand. There's also CG Position as a Percentage of Mean Aerodynamic Chord — that's how we express CG location relative to the wing's aerodynamic reference, which is the standard way pilots and engineers communicate CG position. Then you have the mass definitions. Dry Operating Mass — that's the aircraft's mass including crew, catering, and standard equipment, but excluding traffic load and fuel. Fleet Mass is a simplified value used for a group of aircraft. And Dry Operating Index — that's the moment index value for the dry operating mass, used in load sheet calculations. The load sheet itself — Compiling a Document — that's the formal mass and balance document you produce for each flight. You'll see the fuel sections: Contingency Fuel and Final Reserve Fuel, both defined under EU-OPS rules. Cargo handling is covered — Concentrated Loads, Containerized Cargo, Floor Loading limits, and Flap Position effects on loading. There's Electronic Equipment as a mass item, and Conversion Factors for switching between units. Finally, the passenger cabin classes — First Class, Club/Business, Economy — each with standard mass values assigned for load calculations. So this index is telling you the full scope: regulations, structural limits, CG control, mass definitions, fuel requirements, cargo constraints, and passenger loading. That's the complete mass and balance picture you'll be tested on.