Flight Simulator Testing Of A Variable Speed Helicopter Drivetrain Using Electric Variators

Abstract

This paper presents a piloted simulation study evaluating a continuously variable rotor speed drivetrain for helicopters. The objective is to assess the drivetrain's impact on handling qualities, system behavior, and pilot workload both during dynamic rotor speed transitions and at subsequent steady-state rotor speed levels. The drivetrain, based on a compound-split gearbox architecture with electric variators, enables rotor speed adjustments in flight to improve aerodynamic efficiency. Simulation scenarios include cruise flight with systematic variations in rotor speed, while pilot assessments were conducted using standard handling quality and workload rating scales. The study demonstrated that rotor speed transitions of up to 20% can be executed without compromising helicopter controllability. Power and fuel savings of up to 5% were confirmed during rotor speed reductions. The pilot reported acceptable workload levels and manageable control compensation requirements during rotor speed changes with manual collective adjustment, which were further alleviated by a collective compensation controller. The findings validate the drivetrain's potential to enhance helicopter operational efficiency without significantly degrading handling qualities.