Rotorcraft, dynamic, CG management apparatus and method
An aircraft is disclosed having an engine and a propeller mounted to a fuselage. An empennage mounts to the aircraft and includes first and second horizontal stabilizers separated by a distance greater than the diameter of a stream tube of the propeller at the horizontal stabilizers. A rudder extends between the horizontal stabilizers and is positioned within the stream tube of the propeller. A bulkhead is positioned rearward from the cockpit and oriented perpendicular to a longitudinal axis of the airframe. A tailboom and engine are mounted to the airframe by means of the bulkhead having the engine mounted between the tailboom and a lower edge of the bulkhead. Landing gear may mount to the bulkhead proximate a lower edge thereof. Systems and methods redistribute fuel among laterally, vertically, and longitudinally opposed fuel tanks to maintain a center of gravity in a dynamically stable position.
1. A rotorcraft comprising:
an airframe defining a center plane extending in longitudinal and vertical directions;
a rotor mounted to the airframe and defining a rotor thrust vector;
a propulsion source mounted to the airframe and defining a propulsion thrust vector;
a plurality of fuel tanks distributed in one or more of laterally opposed positions, longitudinally opposed positions, and vertically opposed positions;
the airframe further comprises a pair of tailbooms and an empennage mounted to the airframe by means of the tailbooms;
the plurality of fuel tanks comprises fuel tanks positioned within the tailbooms;
a fuel distribution system coupled to the plurality of fuel tanks;
one or more pumps in fluid communication with the fuel distribution system; and
a control system configured to actuate the one or more pumps effective to redistribute fuel among the plurality of fuel tanks to provide a distribution effective to urge a center of gravity of the aircraft closer to a dynamically stable position.
2. The aircraft of claim 1 , wherein the dynamically stable position is positioned vertically based on the propulsion thrust vector and longitudinally forward of a trajectory of the rotor thrust vector.
3. The aircraft of claim 2 , wherein the dynamically stable position is positioned on the center plane.
4. The aircraft of claim 1 , wherein the dynamically stable position is positioned vertically below the propulsion thrust vector and longitudinally aft of a trajectory of the rotor thrust vector.
5. The aircraft of claim 4 , wherein the dynamically stable position is positioned on the center plane.
6. The aircraft of claim 1 , wherein:
the control system is programmed to redistribute fuel among the plurality of fuel tanks effective to urge the center of gravity closer to the center plane.
7. The aircraft of claim 1 , wherein:
the control system is further programmed to redistribute fuel among the fuel tanks distributed in vertically opposed positions at a rate effective to urge the center of gravity toward the propulsion thrust vector; and
the control system is further programmed to redistribute fuel among the fuel tanks distributed in longitudinally opposed positions at a rate effective to urge the center of gravity forward of a trajectory of the propulsion thrust vector.
8. The aircraft of claim 1 , wherein:
the control system is further programmed to redistribute fuel among the fuel tanks distributed in vertically opposed positions at a rate effective to urge the center of gravity below a trajectory of the propulsion thrust vector; and
the control system is further programmed to redistribute fuel among the fuel tanks distributed in longitudinally opposed positions at a rate effective to urge the center of gravity rearward of a trajectory of the propulsion thrust vector.
9. The aircraft of claim 1 , wherein:
the airframe further comprises wings extending laterally therefrom; and
the plurality of fuel tanks comprises fuel tanks positioned within the wings.
10. The aircraft of claim 1 , wherein:
the rotor is mounted to the airframe by means of a pylon; and
the plurality of fuel tanks comprises at least one fuel tank mounted to the airframe adjacent the pylon.
11. A method for operating a rotorcraft comprising:
selecting a rotorcraft comprising
a rotor mounted to an airframe, the rotor defining a rotor thrust vector,
a propulsion source mounted to the airframe and defining a propulsion thrust vector, and
a plurality of fuel tanks distributed in one or more of laterally opposed positions, longitudinally opposed positions, and vertically opposed positions;
an airframe comprising a pair of tailbooms and an empennage mounted to the airframe by means of the tailbooms, the fuel tanks being positioned within the tailbooms;
detecting a shift in a center of gravity of the rotorcraft to a first position;
redistributing fuel among the plurality of fuel tanks at a rate effective to shift the center of gravity to a second position that is more dynamically stable than the first position.
12. The method of claim 11 , wherein the second position is located at a position selected from:
beneath a trajectory of the propulsion thrust vector and longitudinally behind a trajectory of the rotor thrust vector; and
proximate the trajectory of the propulsion thrust vector and longitudinally forward of the trajectory of the rotor thrust vector.
13. The method of claim 11 , wherein the second position is positioned on a vertical and longitudinal center plane of the rotorcraft.
14. The method of claim 11 , wherein the plurality of fuel tanks comprises fuel tanks distributed in laterally opposed positions, longitudinally opposed positions, and vertically opposed positions.
15. The method of claim 11 , wherein:
the rotorcraft further comprises wings mounted to the airframe and extending laterally therefrom; and
the plurality of fuel tanks comprises fuel tanks positioned within the wings.
16. The method of claim 11 , wherein:
the rotor is mounted to the airframe by a pylon; and
the plurality of fuel tanks comprises at least one fuel tank mounted to the airframe adjacent the pylon.
17. A method for operating a rotorcraft comprising:
selecting a rotorcraft comprising
an airframe,
a rotor mounted to the airframe, the rotor defining a rotor thrust vector,
a propulsion source mounted to the airframe and defining a propulsion thrust vector, and
a plurality of fuel tanks mounted to the airframe, the tanks of the plurality of fuel tanks being distributed in laterally opposed positions, longitudinally opposed positions, and vertically opposed positions;
detecting a shift in a center of gravity of the rotorcraft to a first position;
evaluating the first position relative to a second position, the second position being a more dynamically stable position for the center of gravity than the first position;
laterally redistributing fuel among the plurality of fuel tanks whenever the first position is laterally offset more than a predetermined distance from the second position;
vertically redistributing fuel among the plurality of fuel tanks whenever the first position is vertically offset more than a predetermined distance from the second position; and
longitudinally redistributing fuel among the plurality of fuel tanks whenever the first position is longitudinally offset more than a predetermined distance from the second position.