General: Fundamentals, Weight & Balance, and the Regulations
What this section actually tests
The General section is the shared-knowledge pool for every mechanic task: basic math and physics (lever arms, mechanical advantage, stress and strain, the difference between work, power, and torque), aircraft drawings and symbols, weight and balance, ground handling and safety, corrosion control, inspection fundamentals and NDI methods, hand tools and precision measuring instruments (micrometer, vernier caliper, torque wrench), fluid lines and fittings, safety wiring, and the rules in 14 CFR Parts 43 and 65.
Weight and balance is the highest-yield topic
Three terms drive every problem: datum (the reference plane), arm (horizontal distance from datum in inches, positive aft), and moment (weight × arm, in pound-inches, usually divided by 1,000 before plotting). Compute empty-weight CG from the equipment list, then add each load at its own arm.
Traps to expect: converting gallons with the wrong density (avgas 6 lb/gal, jet fuel about 6.7, oil about 7.5); forgetting that items forward of the datum give negative arms and negative moments; checking total weight but never checking that the CG falls between the forward and aft limits at that weight; and confusing maximum takeoff weight with maximum landing weight.
Worked example
Empty weight 1,200 lb at +40 in; pilot 170 lb at +37 in; fuel 30 gal at +48 in. Fuel = 30 × 6 = 180 lb. Moments: 48,000 + 6,290 + 8,640 = 62,930 lb-in. Total weight = 1,550 lb. CG = 62,930 ÷ 1,550 = 40.6 in aft of datum. Compare 40.6 to the limit lines at 1,550 lb, not at gross weight.
Regulation bait
Preventive maintenance is limited to the items in Part 43 Appendix A and, for pilots, to aircraft not operated for compensation or hire. A 100-hour inspection applies only to aircraft carrying persons for hire or used for hire for flight instruction; the annual inspection applies to all. Airworthiness Directives are mandatory and must be recorded regardless of use.