Fuel Calculation Procedures

033-03-03Pablo Asensio Martínez2026-04-011 min

Specific Gravity (SG) / Density

Fuel is sold by volume (liters/gallons) but calculated by mass (kg/lbs) for performance.

  • Formula: $Mass = Volume \times Density$
  • Jet A1 Density: Typically around 0.8 kg/L (varies with temperature).
  • Hot fuel is less dense (more volume for same weight).
  • Cold fuel is more dense (less volume for same weight).

Fuel Flow Calculation

Integrated Range

For long flights, fuel consumption reduces aircraft weight, which in turn reduces fuel consumption.

  • Calculation: Done step-by-step (typically hourly) or using accumulated tables (Flight Planning Tables).
  • Nautical Air Miles (NAM): Distance flown through the air mass.
    • $NAM = TAS \times Time$
    • $Fuel = NAM \times (Fuel Flow / TAS)$
  • Nautical Ground Miles (NGM): Distance over ground (corrected for wind).
    • $NGM = GS \times Time$

Holding Fuel

Calculated at "Holding Speed" usually at 1,500 ft above destination elevation (for Final Reserve) or at cruise altitude (for Contingency holding).

  • Holding speed is usually lower than cruise speed ($V_{MD}$ usually for max endurance) to minimize flow.

Computer Flight Plans (CFP)

Modern systems automate these calculations, providing a log with:

  • Zone Fuel: Fuel for each leg.
  • Min Fuel: Regulatory minimum.
  • Take-off Fuel: Actual fuel on board at T/O.
  • Burn-off: Expected consumption.