Which equation correctly defines specific range (SR)?

Specific range (SR) is an important measure in aviation that indicates the efficiency of an aircraft in terms of distance traveled per unit of fuel consumed. The correct definition of specific range states that it should be calculated using the true airspeed and total fuel flow.

True airspeed is defined as the actual speed of the aircraft relative to the surrounding air, taking into account factors such as altitude and temperature, making it a more accurate measure when assessing performance in terms of thrust and drag in various flight conditions. By dividing true airspeed by total fuel flow, one obtains the specific range, which provides a clear picture of how efficiently the aircraft is operating in relation to fuel consumption.

When considering the aspects of the other options, while ground speed is the speed over the ground, it does not account for wind effects, making it less suitable for calculating specific range. Indicated airspeed measures the aircraft’s speed directly, but it does not consider altitude or temperature, making it less effective for this calculation. Mach number, representing the ratio of the aircraft's speed to the speed of sound, is also not directly applicable for specific range calculations. Thus, using true airspeed in conjunction with total fuel flow provides a comprehensive and effective means of assessing operational efficiency.