BACKGROUND OF THE INVENTION

Embodiments of the invention generally relate to a control system of a rotary wing aircraft, and more particularly, to power management between a propulsor and a coaxial rotor of a helicopter.

A rotary wing aircraft with a coaxial contra-rotating rotor system is capable of higher speeds as compared to conventional single rotor helicopters due in part to the balance of lift between advancing sides of the main rotor blades on the upper and lower rotor systems. To still further increase airspeed, supplemental translational thrust is provided by a translational thrust system including an integrated propulsor unit with a propulsor (e.g., a propeller) oriented substantially horizontal and parallel to the aircraft longitudinal axis to provide thrust for high speed flight.

In a rotary-wing aircraft application, engine anticipation may be part of the engine control system to maintain rotor speed within a relatively narrow range in response to demanded torque from the rotary-wing aircraft rotor system. The capability of the engine control system to correctly anticipate changes in power required directly impacts rotor speed governor performance. Engine anticipation conventionally focuses on collective changes affecting main rotor power demand. On a helicopter with an integrated propulsor unit, the propulsor contributes a significant fraction of the total power required in many flight regimes, and collective-based anticipation is insufficient to adequately control rotor speed.

Therefore, a need exists for an improved control for engine anticipation for propulsor loads on a helicopter.

BRIEF DESCRIPTION OF THE INVENTION

According to one embodiment, a flight control system for a rotary wing aircraft that includes a main rotor system, a translational thrust system, and an engine control system is provided. The flight control system includes a flight control computer configured to interface with the main rotor system, the translational thrust system, and the engine control system. The flight control computer includes processing circuitry configured to execute control logic. The control logic includes a primary flight control configured to produce flight control commands for the main rotor system and the translational thrust system. The control logic also includes main engine anticipation logic and propulsor loads engine anticipation logic. The main engine anticipation logic is configured to produce a rotor power demand associated with the main rotor system. The propulsor loads engine anticipation logic is configured to produce an auxiliary propulsor power demand associated with the translational thrust system. The flight control computer providing the engine control system with a total power demand anticipation signal based on a combination of the rotor power demand and the auxiliary propulsor power demand.

In addition to one or more of the features described above or below, or as an alternative, further embodiments include where the propulsor loads engine anticipation logic further includes a shaped propeller power demand model configured to produce a propulsor power demand value based on aircraft state data, and the auxiliary propulsor power demand is based on the propulsor power demand value.

In addition to one or more of the features described above or below, or as an alternative, further embodiments include where the translational thrust system has an auxiliary propulsor including a plurality of propeller blades.

In addition to one or more of the features described above or below, or as an alternative, further embodiments include where the aircraft state data includes a propeller pitch command for the propeller blades and a reference rotational rate of the auxiliary propulsor.

In addition to one or more of the features described above or below, or as an alternative, further embodiments include where the propeller pitch command and the rotational rate of the auxiliary propulsor are modeled parameters, and the aircraft state data further comprises: an airspeed of the rotary wing aircraft and a density of air as sensor-based data.

In addition to one or more of the features described above or below, or as an alternative, further embodiments include where the aircraft state data includes a propeller clutch engagement state of a propeller clutch and a propeller speed.

In addition to one or more of the features described above or below, or as an alternative, further embodiments include where the propulsor loads engine anticipation logic includes a filter configured to filter the propulsor power demand value to produce a filtered power demand value, and a drivetrain loss adjustment gain applied to the filtered power demand value to produce the auxiliary propulsor power demand.

These and other features of the systems and methods of the subject disclosure will become more readily apparent to those skilled in the art from the following detailed description of the preferred embodiments taken in conjunction with the drawings.

