Showing content mapped to EASA Part-66. Change authority in the header.
Arithmetic essentials
Mechanics regularly convert between fractions, decimals and percentages when reading torque values, tolerances and mix ratios. Remember BODMAS/BIDMAS for the order of operations. When converting fractions to decimals, divide the numerator by the denominator. Percentages express a value out of 100 — a 2% tolerance on a 500 lb·in torque is ±10 lb·in.
Ratios & proportion
Ratios compare two quantities of the same kind (e.g. gear ratio 3:1). Direct proportion: as one quantity increases, so does the other. Inverse proportion: as one increases the other decreases — typical of pressure/volume in a fixed mass of gas at constant temperature.
Algebra
Rearrange equations by performing the same operation to both sides. Solve for the unknown, transpose formulae for Ohm's law (V=IR → I=V/R → R=V/I), lift (L=½ρv²SCL) and thrust equations. Indices: aⁿ × aᵐ = aⁿ⁺ᵐ, aⁿ ÷ aᵐ = aⁿ⁻ᵐ.
Geometry & trigonometry
Areas: rectangle L×W, triangle ½·b·h, circle πr². Pythagoras: a² + b² = c². Right-triangle trig — SOH CAH TOA: sin = opp/hyp, cos = adj/hyp, tan = opp/adj. Used for control-cable rigging angles and structural repair geometry.
Binary & number systems
Digital systems use binary (base 2), octal (base 8) and hexadecimal (base 16). Convert 1101₂ to decimal: 1·8 + 1·4 + 0·2 + 1·1 = 13. Hex F = 15, so 0xFF = 255.