Mathematical Correlations, Method for the Preliminary Sizing, Design and Tests of an Ultralight All-Electric Aircraft

Abstract

Aviation has a great impact on climate change, resource depletion, and human health. Sixty billion gallons of jet fuel are annually consumed worldwide, and more than 781 tons of CO2 were emitted in 2015. Tetraehtyl lead remains an additive to general aviation fuel; which causes neurotoxic effects, pollution, encephalopathy, low intellectual capacity, and renal tubular damage. 16 million of Americans live and 3 million of children study close to a general aviation airport. Although there have been improvements in fossil fuel motors efficiency, CO2 emissions, and biofuels; all-electric aircraft exceeds those improvements. The advantages of all-electric aircraft are lower noise, pollution, vibration, maintenance, and energy cost; instantaneous and reliable startup; no altitude effects; torque-speed characteristics; and distributed propulsion. Their main disadvantages are its cost, availability, maturity, low range, and endurance (due to the low specific energy of the batteries). Norway plans all short-haul flights (15-30 min) to be on electric 25-to-30 seat aircraft by 2040. The Swedish flight-shaming movement is causing passengers to move by train. Although several all-electric aircraft prototypes have been built and tested, there are no mathematical correlations and equations that allow the designer to estimate the motor power, and take-off, battery, and motor weight. Mathematical correlations and equations were elaborated based on the data obtained from the manufacturers of 34 all-electric aircraft. This paper presents the continuous power, weight, and power density of 19 electric aircraft motors that have been used in all-electric aircraft, and are available for new designs. The Predator 50-6 Evo electric motor produces 19 kW of continuous power and has a specific power of 8.3 kW.kg-1, while Siemens SP260D produces 261 kW and has a specific power of 5.2 kW.kg-1; and the Magnix Magni500 produces 560 kW and has a specific power of 4.1 kW.kg-1. Similarly, the voltage, capacity, energy, weight, and specific energy of five high specific energy lithium batteries are presented. LiNiMnCo and LiS batteries have obtained specific energies of 260 Wh.kg-1. Additionally, a preliminary approach was defined to estimate the weight and power of all-electric aircraft during cruise, take-off, and climb. Based on Michael Sandlin’s Goat 4 and Dale Kramer’s electric Lazair, a single-seat ultralight-glider all-electric aircraft was designed and built with a tricycle fixed landing gear. 6061T6 aluminum tube, aviation hardware, and uncertified Dacron 2.97 oz.yd-2 fabric was used to build the structure. The wing span is 36 ft, the wing area is 174 ft2, and the empty weight is 109 kg. 626 INR-18650-35E Samsung 3500 mAh lithium ion cells were spot welded in series and parallel to form two battery packs of 14S, 58.8 V, 78.2 Ah, and 4.5 kWh each. These packs are protected by two 300 A 14S Li-ion bluetooth MOS-screen Battery Management System (BMS). Two Turnigy Dlux 250A HV 60 V 14S opto Electric Speed Controllers (ESC) run two Turnigy CA-120-70-15 9.8 kW brushless permanent magnet DC out-runner motors. These motors are coupled to two Xoar 30 x 12 inch wood propellers. Two Juntek VAT-4300 400 V 300 A Watt meters were used in each circuit to measure DC voltage, current, power, charge and discharge capacity, Watt-hour, and temperature. This setup provides an estimated endurance of 27 minutes, and a cruise velocity of 30 knots.