Helicopter Electric Tail Rotor Drive
Navy SBIR FY2013.1

Sol No.: Navy SBIR FY2013.1
Topic No.: N131-069
Topic Title: Helicopter Electric Tail Rotor Drive
Proposal No.: N131-069-0438
Firm: LaunchPoint Technologies, Inc.
5735 Hollister Ave, Suite B
Goleta, California 93117
Contact: Michael Ricci
Phone: (805) 683-9659
Web Site: www.launchpnt.com
Abstract: LaunchPoint Technologies Inc. proposes to develop an electric drive system for a Bell 206 helicopter tail rotor. The Navy variant of this helicopter is the TH-57. The system will be designed to retrofit existing aircraft. The drive system will consist of a permanent magnet (PM) generator attached to the tail rotor output of the turbine gearbox and a direct drive PM motor replacing the tail rotor gearbox. Power electronics and electric cables connect the generator to motor. LaunchPoint Technologies will use its ironless dual Halbach array axial flux motor/generator technology and electric motor/generator drive technology to achieve significant weight savings and efficiency gains over designs based on conventional iron core motors; thus enabling a technically and commercially viable solution that has eluded the aviation industry in the past. The drive system is estimated to add 7 to 9 kg to the vehicle while increasing vehicle efficiency, reliability, flyability, and operational performance. Within the phase I activity this estimate will be confirmed with detailed engineering design and modeling. Additional design optimizations and features will be evaluated that have the potential to further reduce the mass or increase the utility of the system.
Benefits: Anticipated Benefits: An electric tail rotor drive for a helicopter can add operational flexibility and increase overall machine efficiency and reliability. Unlike a mechanically driven tail rotor, the electric tail rotor speed can be set independently of main rotor speed. This leads to a benefit where the tail rotor speed can be decreased in forward flight, which will decrease tail rotor drag and increase overall flying efficiency. Decoupling the main rotor and tail rotor speed can prevent the tail rotor from stalling in conditions where the main rotor speed suddenly drops due to a large collective control input (such as the response to a sudden change in a load while lifting),thus preventing loss of control of the aircraft. A variable speed tail rotor can improve the operational regime of the aircraft by adjusting tail rotor speed to prevent loss of tail rotor effectiveness in conditions where main rotor and tail rotor vortices interact with the incident wind at specific angles and velocities to reduce tail rotor thrust and aircraft control. The electric tail rotor can be run at high speed during initial startup to counter main rotor start-up torque which would allow operation of a helicopter on floats/pontoons or low traction icy landing surfaces. The electric tail rotor system will be designed with redundancy built in and should be able to achieve a higher MTBF and safer degraded performance failures than gearbox tail rotor drives which fail catastrophically. Commercial Application: This technology will find its way into commercial use in a number of applications. Initially this technology could be offered as a retrofit product for existing helicopters to increase performance, efficiency, and safety; adding value to older aircraft. Eventually this technology will be licensed for use in new helicopter designs and incorporated into the product offerings of major aerospace companies. More generally the research and development in this project is applicable to the propulsion of all electric and hybrid electric aircraft. There is intense interest in hybrid electric unmanned aerial systems (UAS) right now and this technology will undoubtedly make its way into some of the prototype systems being designed. Some of these prototypes will eventually make it into production for a robust commercial market. The UAS market is expected to expand greatly into civil aviation as well as into military aviation over the next 5 to 10 years as the FAA drafts rules allowing UAS operations in civil airspace.