Aircraft fuel contributes to the weight carried by the airplane, and its mass is expressed in pounds. Jet A-1, the kerosene grade used by most turbine aircraft, weighs around 6.7 pounds per gallon, whereas 100LL avgas, the gasoline burned by piston trainers, is about 6 pounds per gallon. Because a Boeing 747 can depart with more than 350,000 lbs. of jet fuel, the difference between empty weight and maximum gross weight is largely the difference between tanks that are dry and tanks that are full. For any flight, accurate fuel planning converts the required energy density into the correct number of pounds so that the aircraft weight and balance envelope is respected from take-off to landing.
How much does airplane fuel weigh?
Aircraft fuel is stored in tanks whose weight depends on the fuel type. Avgas for piston-engine aircraft averages 6.5 lb/US gal (2.95 kg/L), while jet fuel for turbine engines is around 6.7 lb/US gal (3.04 kg/L). On a practical scale, thirty gallons of fuel weighs more than one passenger, and a typical wide-body jet flight departs with over one hundred thousand pounds of fuel loaded.
What is the density of airplane fuel?
Airplane fuel density at 15°C is 0.804 kg/L (6.71 lb/US gal). ASTM D1655 specification sets Jet A-1 density between 775.0 and 840.0 kg/m (6.47-7.01 lb/US gal), equivalent to 0.747-0.84 g/cm (0.747-0.84 g/cm ). In performance calculations airliner manufacturers use a density of jet fuel around 0.8 kg/L (6.68 lb/gal). Jet fuel density is the mass of fuel per unit volume. Fuel’s specific gravity varies with temperature, so density correction uses the VCF method.
What is the density of airplane fuel energy? Jet fuel energy density is 34.7 MJ/L (9.6 kWh/L) for Jet A-1 and 35.3 MJ/L (9.8 kWh/L) for Jet A. The high-energy density of Jet A-1 is 43.15 MJ/kg (11.99 kWh/kg). ATJ SAF energy density is 44.0 MJ/kg.
Why is airplane fuel measured by weight?
Airplane fuel is measured by weight because the volume of fuel changes with temperature, while weight does not change with temperature or pressure. Jet fuel, like any liquid, expands when warm and contracts when cold, so a liter of fuel at one temperature weighs a different amount at another. Because fuel is burned by mass, not by volume, weight gives a reliable, constant measure of energy content. Airlines therefore require fuel information in weight, and pilots rely on this data to calculate range, balance, and fuel burn rates. Accurate fuel level data in weight units is also vital for compliance with aviation safety standards.
What is airplane fuel load?
Fuel load refers to the total quantity of fuel carried by an aircraft, including all tanks and reserves, measured in lbs. Fuel load is an expendable part of the load of the aircraft. Fuel load directly influences the aircraft's weight, range, and center of gravity. Fuel load divided by fuel mass flow rate equals maximum flight time.
Fuel includes all usable fuel aboard the aircraft. Usable fuel is lower than the designed fuel tank capacity because of safety margins. Fuel capacity is a fixed design specification. Maximum allowable fuel must not exceed fuel capacity.
Fuel is stored in multiple tanks and is burned from the center tank first and then from the wing tanks. Minimum fuel carried in the wings is deemed ballast to prevent excessive wing bending. Fuel distribution shifts center of gravity. Useful load consists of the weight of the pilot, crew, passengers, baggage, usable fuel, and drainable oil.. Payload does not include fuel.
What is the Zero Fuel Weight of an airplane?
Zero Fuel Weight is the weight of the aircraft with everything loaded for that flight minus usable fuel. It refers to the total weight of the airplane and all its contents excluding any fuel. This weight includes the aircraft's basic operating weight, crew, passengers, baggage, cargo, and any additional items onboard, but excludes consumable fluids like oil.
Zero fuel weight is an operating limitation intended to protect the wing spar structure. It sets a maximum allowable weight that can be carried in the fuselage, limiting the concentration of load relative to the all-up weight borne by the wings. This prevents destructive wing-bending stress and ensures the aircraft remains within structural limits during flight. For example, a zero fuel weight of 4,400 pounds (1,995.8 kilograms) represents the maximum zero fuel weight for a particular aircraft configuration.
Maximum Zero Fuel Weight is a published MZFW value found in the approved Aircraft Flight Manual or the aircraft Type Certificate Data Sheet. This value is entered into flight planning applications and is vital for accurate weight and balance calculations. If the total weight of the aircraft without fuel exceeds this limit, passengers or cargo must be reduced to bring the weight at or below the maximum Zero Fuel Weight.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
