Autorotation Modeling, Simulation, and Analysis of a Generic Lift-Offset Coaxial Compound Rotorcraft

Publication Date

1-1-2023

Document Type

Conference Proceeding

Publication Title

FORUM 2023 - Vertical Flight Society 79th Annual Forum and Technology Display

Abstract

Lift-offset coaxial compound rotorcraft designs have been proposed for the U.S. Army Future Vertical Lift (FVL) programs. Without a need for the tail rotor and equipped with a pusher-propeller, the coaxial compound configuration is capable of achieving high airspeeds and perform maneuvers not feasible for the conventional rotorcraft. To facilitate an independent assessment of the lift-offset coaxial configuration by the U.S. Army, a physics-based flight dynamic model of a 14,000 lbs gross weight configuration was developed using open source data and implemented into the HeliUM-A comprehensive analysis code. This paper evaluates the coaxial configuration for autorotation performance in case of an engine failure. The HeliUM-A code is enhanced to simulate a steady descending autorotative trim condition with and without the pusher-propller declutched from the main rotor. Minimum descent angle and sink rate occur at approximately 70-80 kts airspeed. The declutched case with pusher-propeller speed reduced by 75% yields the lowest sink rate and descent angle. Flight dynamics responses in steady descending autorotation are analyzed with the yaw rate response showing significant differences compared to a steady level flight condition.

Department

Research Foundation

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