Range and Endurance Estimates for Battery-Powered Aircraft

T HE utility and cost effectiveness of small unmanned aerial vehicles (UAVs) has seen a large increase in their use, in both civilian and military applications. Depending on the particular requirements, the aircraft may be powered using a piston-gasoline engine or an electric motor. Electric propulsion appears to be favored as the UAV size diminishes or if stealth, in terms of acoustic signature, is a design requirement. Expressions to estimate the range and endurance of piston propeller and jet aircraft are well established [1,2] (the Breguet equations). Estimates for the range and endurance of electric aircraft are less well established [3,4] and may not be presented in a fashion consistent with that typically employed in the aeronautics community. Consideration of the propulsion system would suggest that equating the power delivered by the battery, accounting for losses due to the propeller, motor, and motor controller, to the power required to overcome drag would yield performance estimates. While this approach is sound, the behavior of a battery and its effective capacity, depending on the current draw (the so-called Peukert effect [5]), should be accounted for; otherwise, significant estimation errors may occur. Consequently, in this Note, expressions are derived to estimate the range and endurance of a battery-powered electric aircraft, accounting for battery discharge behavior. The impact of ignoring the Peukert effect is investigated. Parameters affecting performance are examined.