Fuel Consumption Calculations

Understanding Fuel Consumption Calculations

Fuel consumption calculation is a core navigation skill for pilots, allowing you to determine how much fuel is needed for a flight, how much has been used, and how efficiently the aircraft is burning fuel. The process often involves:

• Calculating fuel burned over a given time or distance.
• Converting between units (litres, kilograms, pounds, gallons) using specific gravity.
• Determining hourly fuel flow from a known consumption over a shorter period.
• Estimating fuel efficiency (e.g., pounds per nautical mile).

Using Navigation Computers

Most pilots use a navigation computer (such as the CRP-5) for rapid, accurate fuel consumption calculations. These devices have dedicated scales for fuel flow, allowing you to:

• Find fuel burned in a set time: Align 60 (minutes) with the hourly burn rate, then read off the fuel used for your specific time interval.
• Calculate hourly burn from a partial-period consumption: Align the time interval with the fuel used, then read the hourly rate at 60 minutes.
• Convert between mass and volume using specific gravity: For example, to convert kilograms per hour to litres per hour, align the burn rate with the specific gravity, then read the corresponding value.

Practical Steps

1. Estimate mentally before using the computer to avoid decimal errors.
2. Align scales as required (time, fuel quantity, specific gravity).
3. Read results directly, checking units and reasonableness.

Common Scenarios

• Calculating fuel required for a flight segment given burn rate and time.
• Determining fuel remaining after a certain period.
• Converting between gallons, litres, kilograms, and pounds for fuel uplift or consumption.

Accurate fuel consumption calculations underpin safe flight planning and effective in-flight management.