Design and Construction of a Compound Coaxial Tilting-Head Rotorcraft

Open Access
- Author:
- Bennink, James
- Graduate Program:
- Aerospace Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- July 01, 2024
- Committee Members:
- Jacob Willem Langelaan, Thesis Advisor/Co-Advisor
Edward Smith, Committee Member
Amy Pritchett, Program Head/Chair
Joseph Francis Horn, Committee Member - Keywords:
- compound helicopter
rotorcraft
tilt-head
coaxial - Abstract:
- This thesis describes development and initial flight testing of a compound coaxial tilting-head rotorcraft. A coaxial tilting head rotorcraft (CAT-HR) comprises a pair of coaxial, contra-rotating propellers to provide lift thrust and (through differential shaft speed) yaw control; roll and pitch control are achieved by tilting the rotorhead (on a gimbal) with respect to the vehicle body. This configuration removes complexity associated with a swashplate (that provides collective and cyclic blade pitch control). A thruster is added in an effort to increase speed in forward flight, resulting in a compound coaxial tilting--head rotorcraft (CCT-HR). The focus of this work is the longitudinal dynamics of the vehicle, which fully define the integration of the thruster with the CAT-HR architecture. The steady state flight performance is compared across airspeeds and flight path angles to determine power--optimal flight conditions. These results influence the development of a fully integrated control system that blends the control of the thruster with that of the gimbal and coaxial rotors in forward flight. Flight testing of the CCT-HR proves the effectiveness of the design near hover, but also reveals stability challenges in forward flight. Rotor flapping of the coaxial fixed pitch propellers is determined to cause pitch instabilities in forward flight, even at this scale. Proposed solutions are presented to integrate the thruster's control for high speed zero--pitch flight.