Calculate Aircraft Range
Aircraft are limited in the amount of time they can spend in the air by how much fuel they are carrying and how quickly the aircraft consumes that fuel. Aircraft also have varying airspeed capabilities, with speed translating into distance traveled. Factoring in fuel load, fuel consumption and airspeed, aircraft can only travel a certain maximum distance before they must land to refuel. This is known as the range of the aircraft. It is important for one-way travel to carry cargo and passengers safely from point to point while traveling as far as possible without stopping for fuel. It is vital for combat aircraft to travel to the combat area, spend time in combat, and still be able to make it back to base. Use these tips to learn how to calculate aircraft range.
Contents
Steps
Obtain the Manufacturer Specifications
- Determine the variables for the velocity needed to cruise. This will be a velocity at which the weight of the aircraft and the load equals the lift generated by the velocity. The manufacturer specification will give the lift coefficient (Cl) and the drag coefficient (Cd). The manufacturing specification will give the wing area (A).
- Figure out the flying weight. The manufacturer specification will give the unloaded weight of the aircraft. The calculation of range will depend on the total weight (W) of the aircraft, which is the unloaded weight plus the load placed on the aircraft.
- Find the fuel consumption rate. The manufacturer specification will give the Thrust Specific Fuel Consumption (TSFC) rate of the aircraft propulsion system.
- Note the fuel capacity. The manufacturer specification will give the fuel capacity of the aircraft's fuel tanks. This fuel load should be expressed as a weight (M). It is common that a small auxiliary tank be added for emergency use, but the emergency fuel should not be considered when determining range.
Calculate Aircraft Range
- Derive the cruising velocity. Cruising velocity (V) is when lift (L) equals weight, or W = L. From aerodynamic equations, V equals the square root of W divided by (0.5 times Cl times r times A), where r is the air density at the altitude chosen for flight.
- Find the fuel consumption. In cruising, thrust (F) equals drag (D). By aerodynamic equations, at cruising conditions F equals W times Cd divided by Cl. TSFC determines the fuel consumption at this thrust, so the maximum time the engines can operate is M divided by (TSFC times F).
- Determine ground speed. The ground speed is the air speed V plus a tail wind or minus a head wind.
- Complete the range calculation. Aircraft range is ground speed times the maximum time the engines can operate.
Tips
- Piloted military aircraft never (intentionally) fly one-way missions. Commanders can only use the aircraft out to the point where the aircraft can get back to base. This is half of the range, commonly referred to as combat radius.
