Final Modifications of NPS Hummingbird Remotely Piloted Helicopter in Preparation for Flight

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Final Modifications of NPS Hummingbird Remotely Piloted Helicopter in Preparation for Flight

A. J. Booth

The goals of this thesis were to make final design modifications and perform static testing to prepare the Hummingbird, a 150 pound, remotely piloted helicopter (RPH), for untethered flight. The major elements involved were: (1) The adaptation of a suitable, permanently-dedicated test stand for use with large-scale RPH/RPV (remotely piloted vehicle) aircraft; (2) A major rotor drivetrain improvement to the helicopter to enable it to autorotate and safely land in the event of an in-flight engine failure, thus avoiding potential loss of the helicopter due to crash; (3) Complete break-in and testing of a replacement engine for a mechanically-seized first engine; and (4) Limited hover testing while secured to the tether test stand. Test stand modifications include design and implementation of a compression spring to offset the weight of the new mounting assembly and a restricting collar to confine mobility of the stand's universal joint. The mechanical change to the drivetrain consists of replacement of a conventional belt-drive sprocket with a one-way sprague clutch bearing inside the gear. This provides the Hummingbird with the critical capability to autorotate. The new engine, correctly broken in, and the subsequent static testing provide the Department of Aeronautics and Astronautics with an operational platform ready to perform subsequent in-flight testing.