What is the recommended way to calculate cruise fuel consumption?

Using specific fuel consumption rates along with power settings is the recommended method for calculating cruise fuel consumption because it provides a more precise estimation based on the performance characteristics of the specific aircraft and its engine configuration. Specific fuel consumption rates are typically expressed in terms of pounds of fuel burned per horsepower per hour or similar units that correlate fuel usage with engine power output. By incorporating the actual power setting during cruise, pilots can derive a fuel consumption rate that aligns with the conditions of the flight, including altitude, airspeed, and engine performance.

This approach is preferable as it accounts for variations in fuel efficiency that can occur due to different power settings or environmental conditions. Estimating based on previous flight data lacks the consideration of changes in weight, weather, and operational parameters that could affect fuel efficiency. Relying solely on the weight of the aircraft does not provide a complete picture because it ignores how engine performance may vary at different power settings. Similarly, using a standard fuel flow rate for all aircraft can lead to inaccuracies, as different aircraft types and configurations have unique fuel usage characteristics. Therefore, employing specific fuel consumption rates aligned with power settings delivers the most reliable and accurate method for calculating cruise fuel consumption.