Development of a Pitch Control System for a Hybrid Electric Propulsion System

A propeller pitch control system enables mid-fight adjustment of the propeller blade angle. This improves propulsion system efficiency, allows for reverse thrust and improves safety by reducing propeller drag in anengine-out emergency scenario. In this master thesis project, conducted at electric airplane manufacturer Heart Aerospace, a concept of a pitch control system for the ES-30 was developed, a hybrid-electric regional airliner in development by Heart Aerospace. Five potential concepts were generated, including two hydraulic pitch control systems and three fully electric. These were compared and scored, before a single concept was selected for further development by designing a demonstrator. It was determined that hydraulic pitch control systems could be easier to integrate and certify for flight. Electric pitch control could however reduce the weight and energy consumption of the system. When scoring the concepts based on multiple factors such as cost, weight, maintenance needs, energy efficiency and ease of certifcation it was concluded that fully electric pitch control systems are more suitable for the Heart Aerospace ES-30. It was chosen to move forward with an electric concept that involved an electric linear actuator placed in the propeller hub. For the demonstrator design we decided to create the linear electric actuator using a rotary servo motor and a ball screw mounted along the axle of the propeller hub. The nut of the ballscrew is attached to a maneuvering plate, which in turn pushes on metal pins attached to each blade root, which results in a blade angle change. This system was simulated and CAD models were made.