Airfoil system

A vertical take-off-and-landing aircraft comprising:

• a body;
• a propulsion system coupled to the aircraft;
• and airfoils, each airfoil having a compound control surface at a trailing edge of the that airfoil, each compound control surface comprising a flap and an aileron disposed directly above the flap, the aileron and the flap being simultaneously operable with each other;
• a flight control system configured to operate the aircraft in a hovering flight mode and a horizontal cruising flight mode;
• wherein, when the aircraft is operated in the hovering flight mode:
• the propulsion system generates downward thrust;
• the flaps of each airfoil are pivoted about leading edges of those flaps such that trailing edges of those flaps are angled downward with respect to the trailing edges of that airfoil;
• the ailerons of each airfoil are pivoted about leading edges those ailerons such that trailing edges those ailerons are angled downward with respect to the trailing edge of that airfoil, wherein the leading edge of the flap of each airfoil is extended away from a trailing edge of that airfoil, forming an open space wider than a chord of the aileron of that airfoil and longer than a span of the flap of that airfoil;
• wherein, when the aileron of each airfoil is pivoted about the leading edge of the aileron of that airfoil;
• a trailing edge of the aileron of that airfoil passes through the open space;
• and
• the trailing edge of the aileron of that airfoil extends below the leading edge of the flap of that airfoil and allows air to flow through an aperture formed between a top surface of aileron of that airfoil and a top surface of the flap of that airfoil;
• and
• wherein, when the aircraft is operated in the horizontal cruising flight mode:
• the aileron of each airfoil is configured to be deflected upward only beyond a neutral position of that aileron;
• and
• the flight control system responds to a control input indicating a banking turn by:
• actuating an aileron of an airfoil nearest a direction of the banking turn upward with respect to that airfoil;
• and
• maintaining ailerons of other airfoils in neutral position with respect to those airfoils.

A method of controlling a vertical take-off-and-landing aircraft, comprising:

• determining, at a first time, that the aircraft has entered a hovering flight mode and, when the aircraft enters the hovering flight mode, causing a flight control system of the aircraft to perform the steps of:
• causing a propulsion system of the aircraft to generate downward thrust in a direction substantially perpendicular to a plane defined by a first wing of the aircraft and a second wing of the aircraft;
• pivoting a first flap disposed at a trailing edge of a first wing of the aircraft about a leading edge of the first flap;
• and pivoting a second flap disposed at a trailing edge of a second wing of the aircraft about a leading edge of the of the first and second flap such that trailing edges of the first and second flaps are angled downward with respect to the trailing edges of the first and second wings;
• and
• pivoting a first aileron disposed directly above the first flap about a leading edge of the first aileron;
• and pivoting a second aileron disposed directly above the second flap about a leading edge of the second aileron, such that the trailing edges of the first and second ailerons are angled downward with respect to the trailing edges of the first and second wings;
• wherein placing the aircraft in the hovering flight mode includes causing the flight control system to perform steps of:
• extending leading edges of the first flap away from the trailing edge of the first wing and extending the second flap away from the trailing edge of the second wing, thereby forming:
• a first open space deeper than a chord of the first aileron and wider than a span of the first aileron between the first wing and the leading edge of the first flap;
• and a second open space deeper than a chord of the second aileron and wider than a span of the second aileron between the second wing and the leading edge of the second flap and the second aileron;
• and
• causing the flight control system, while pivoting the first and second ailerons about the leading edges of the first and second ailerons, to:
• cause the trailing edge of the first aileron to pass through the first open space and cause the trailing edge of the second aileron to pass through the second open space;
• and
• cause the trailing edges of the first and second ailerons to extend below the leading edges of the first and second flaps, respectively, thereby allowing air to flow through apertures formed between top surfaces of the first and second ailerons and top surfaces of the first and second flaps;
• and
• determining, at a second time, that the aircraft has entered a horizontal cruising flight mode and, while the aircraft is in the horizontal cruising flight mode, causing the flight control system of the aircraft to prevent the first and second ailerons from rotating downward past neutral positions of those ailerons.