Development of "Aria," a Compact, Ultra-Quiet Personal Electric Helicopter

Abstract

This paper describes the development and flight testing of a personal air vehicle by team Harmony for the Boeing GoFly X-prize challenge. For the $1mil grand prize, aircraft were scored by compact size, speed, low noise, and endurance. The team chose a coaxial electric helicopter configuration to maximize rotor area and reduce disk loading for efficiency and acoustic benefits. The rotors were designed through an extensive parametric study using an in-house performance code. Air loads were modeled in HPCMP CREATE™-AV Helios for validation, then used in an inhouse acoustics solver to estimate sound pressure levels. A quiet electric power train was developed, as well as a custom 11kWh, 200lb (90.7kg) battery pack. The flight dynamics of the configuration were modeled and the stability analyzed. Structural analysis was utilized in designing key load-bearing parts. Flight control was implemented with dual, independent, electronically coupled swashplates. First, a 1/3rd scale prototype aircraft was developed to validate the design and acoustic predictions. Then a full-scale, 520lb (235.4kg) prototype with an 8.5ft (2.59m) rotor diameter was developed and accumulated 19.5hrs of testing time. During hovering, the sound pressure levels at 50ft (15.24m) were 73dBA, remarkably low for a rotorcraft. The results of this study underscored the endurance limitation of electric flight due to poor battery performance, as well as the need for reliable, lightweight hardware for such applications.

Design, development, and flight testing of a tube-launched coaxial-rotor based micro air vehicle

“…Another advantage is the lower disk loading of the coaxial configuration that can offer longer endurance and lower noise signature compared to a multi-rotor such as a quad-rotor of the same footprint. 3 To further reduce the complexity and for ease of blade folding, a gimbaled-hub based thrust-vectoring mechanism is used in place of mechanically complex swashplates to control pitch and roll in conjunction with fixed-pitch rotors. This reduced complexity should improve the overall reliability of the system when subjected to launch accelerations.…”

“…1,2 For example, the energy density of commercial lithium-ion cells can reach 200 Wh/kg in ideal settings; however, this energy density can decrease to 150 Wh/kg at the pack level in real conditions. 3–5 Limited battery capacity places more stringent constraints on rotary-wing systems compared to fixed-wing aircraft due to the higher power requirement for hovering. Often, rotary-wing MAVs have a hover endurance of less than 20 minutes, 1,2,6 making it imperative to consider unconventional approaches to improve the effectiveness of hover-capable platforms for ISR missions.…”

Archives of Thermodynamics

“…The structure was modernized and its various variants were analysed as actual models were created [16]. The latest achievement in the field of propulsion is the Aria project [17], which resulted in the construction of a fully flying model. The results of the study highlighted the limitation of the flight electric endurance due to poor battery performance, as well as the need for reliable, lightweight equipment for such applications.…”