Enhanced flight control systems and methods for a jet powered tri-mode aircraft

A method for scheduling canard positions and horizontal tail positions of a jet-powered tri-mode aircraft as a function of the speed of the aircraft to achieve smooth unloading of a rotor blade of the aircraft, the method comprising:

• providing closed loop control of the pitch attitude using a pitch moment command having a low frequency component and a high frequency component;
• providing open loop control of the horizontal tail position using the pitch moment command;
• determining the horizontal tail position relative to its position limit;
• and
• if the horizontal tail position is not approaching its position limit, then scheduling the elevon position using the high frequency component and scheduling the horizontal tail position using the sum of the open loop control and the low frequency component;
• if the horizontal tail position is approaching its position limit, then scheduling the elevon position using a large portion of the low frequency component and the high frequency component and scheduling the horizontal tail position using a small portion of the low frequency component;
• and
• if the horizontal tail position has reached its position limit, then scheduling the elevon position using the pitch moment command and scheduling the horizontal tail position to be fixed at its position limit.

A method for scheduling, as a function of aircraft speed, the transition from a helicopter mode to a compound mode to a fixed-wing mode of a jet-powered tri-mode aircraft having a rotor blade, a mast valve, a cruise nozzle, a canard wing, and a horizontal tail, the method comprising:

• scheduling a rotor speed reference as a function of aircraft speed;
• scheduling the mast valve to open and the cruise nozzle to close in the helicopter mode;
• scheduling the mast valve to gradually close and the cruise nozzle to gradually open in the compound mode;
• and
• scheduling the mast valve to close, the cruise nozzle to open, and the tilt of the canard wing to gradually decrease in the fixed-wing mode.

A method for performing an automatic autorotation of a rotor blade of a jet-powered tri-mode aircraft in the event of an engine failure, the method comprising:

• setting a horizontal speed reference for the aircraft using modulation of pitch attitude;
• maintaining the rotor speed using collective position modulation;
• computing a flare altitude using an acceptable vertical acceleration;
• and
• setting a terminal vertical speed reference for the aircraft using the acceptable vertical acceleration.

A method for stabilizing a jet-powered tri-mode aircraft as the jet-powered tri-mode aircraft travels in a compound mode, which is between a helicopter mode and a fixed-wing mode, the method comprising:

• receiving a plurality of velocity vector component values, a plurality of velocity vector commands, and a rotor speed reference value;
• generating a pitch attitude command and a roll attitude command using the plurality of velocity vector component values, the plurality of velocity vector commands, and the rotor speed reference value;
• generating a plurality of acceleration commands using the pitch attitude command and the roll attitude command and a plurality of vertical acceleration commands using a commanded array of waypoints or pilot control stick commands;
• and
• scheduling the rotor blade speed, a canard of the aircraft, and a horizontal tail of the aircraft as a function of a forward speed of the aircraft.

A method for controlling the vertical flight path of a jet-powered tri-mode aircraft having a rotor blade, a mast valve, and a cruise nozzle as the jet-powered tri-mode aircraft travels in a compound mode, which is between a helicopter mode and a fixed-wing mode, the method comprising:

• generating a throttle command to control the forward speed of the aircraft;
• generating a collective command to control the rotor speed of the rotor blade;
• and
• generating pitch attitude and angle of attack commands to control the vertical flight path of the aircraft.