Flight Planning and Fuel Management
Core concepts
Fuel planning rests on a hierarchy of reserves that must be understood as separate, additive quantities. Start with trip fuel (taxi-out to touchdown at destination), then add contingency (commonly 5% of trip fuel, or 3% with an approved en-route alternate), alternate fuel (destination to the nominated alternate), final reserve (typically 30 minutes holding at 1500 ft above the alternate in a turbine aircraft), and additional/extra fuel at the commander's discretion. Taxi fuel is accounted separately and is not part of trip fuel. Total fuel on board must never be less than taxi + trip + contingency + alternate + final reserve + additional.
You must be fluent in the performance side too: take-off and landing mass limits, climb and cruise gradients, drift-down and depressurisation, and the effect of temperature, pressure altitude and wind on all of them. Cruise planning uses the specific range concept (air miles per unit fuel); the optimum is where the tangent from the origin touches the fuel-distance curve, and questions often ask you to compare a tailwind case with a headwind case. A headwind shifts the optimum toward a lower speed; a tailwind shifts it higher.
Traps
Watch for units: kg versus lb, US gallons versus litres, and fuel density assumptions. Distinguish still-air from moving-air distances. Beware questions that give reserve fuel in minutes but ask for a mass - you must convert using the holding fuel flow at the stated mass. Also watch "fuel remaining at destination" versus "fuel at start of approach".
Worked example
Trip fuel 4000 kg, contingency 5% = 200 kg, alternate 700 kg, final reserve 30 min at 1200 kg/h = 600 kg, taxi 150 kg. Minimum ramp fuel = 150 + 4000 + 200 + 700 + 600 = 5650 kg. If the aircraft burns 1300 kg/h in the cruise, the trip time is about 3 h 05 min.