Various embodiments of an airfoil and machines with airfoils are disclosed. The airfoils include a thicker leading airfoil portion and a thinner trailing airfoil portion. In one embodiment, the leading airfoil portion is formed by bending a body of the airfoil back toward itself. In another embodiment, the leading airfoil portion has a solid geometry and includes two elliptic surfaces. To prevent detachment of airflow, the leading airfoil portion includes at least two arc portions or surfaces that act to direct the airflow down to the trailing airfoil portion in a manner that stabilizes vortexes that may form in the region of changing thickness.

A stoppable rotor, which includes a first and second blade and rotates about a substantially vertical axis, is stopped with the first blade pointing forward and the second blade pointing backward while the aircraft is mid-flight. Anti-torque is provided using a set of one or more combination rotors in a first mode of operation in order to counter torque produced by the stoppable rotor when the stoppable rotor is rotating where the set of combination rotors rotate about a substantially longitudinal axis. Forward thrust is provided using the set of combination rotors in a second mode of operation when the stoppable rotor is not rotating.

A stoppable rotor, which includes a first and second blade and rotates about a substantially vertical axis, is stopped with the first blade pointing forward and the second blade pointing backward while the aircraft is mid-flight. Anti-torque is provided using a set of one or more combination rotors in a first mode of operation in order to counter torque produced by the stoppable rotor when the stoppable rotor is rotating where the set of combination rotors rotate about a substantially longitudinal axis. Forward thrust is provided using the set of combination rotors in a second mode of operation when the stoppable rotor is not rotating.

While an aircraft is mid-flight, a braking start point associated with a stoppable rotor is calculated where the stoppable rotor includes a first and second blade and the stoppable rotor is configured to rotate about a substantially vertical axis. A process to stop the stoppable rotor is started, while the aircraft is mid-flight, when the stoppable rotor reaches the braking start point, where the stoppable rotor is stopped with the first blade pointing forward and the second blade pointing backward.

A trim tab for use in a blade housing includes a cavity connected to an opening extending from the cavity out a trailing edge of the blade housing, the cavity has a first dimension which is greater than a second dimension of the opening at a same spanwise location of the blade housing. The trim tab has a trim portion, a head portion having a head dimension substantially similar to the first dimension, and a tail portion connecting the trim portion and the head portion. The tail portion has a tail dimension substantially similar to the second dimension such that the trim tab is retainable by the blade housing when the head portion is disposed within the cavity and the tail portion is disposed within the opening.

Various embodiments of an airfoil and machines with airfoils are disclosed. The airfoils include a thicker leading airfoil portion and a thinner trailing airfoil portion. In one embodiment, the leading airfoil portion is formed by bending a body of the airfoil back toward itself. In another embodiment, the leading airfoil portion has a solid geometry and includes two elliptic surfaces. To prevent detachment of airflow, the leading airfoil portion includes at least two arc portions or surfaces that act to direct the airflow down to the trailing airfoil portion in a manner that stabilizes vortexes that may form in the region of changing thickness.

Various embodiments of an airfoil and machines with airfoils are disclosed. The airfoils include a thicker leading airfoil portion and a thinner trailing airfoil portion. In one embodiment, the leading airfoil portion is formed by bending a body of the airfoil back toward itself. In another embodiment, the leading airfoil portion has a solid geometry and includes two elliptic surfaces. To prevent detachment of airflow, the leading airfoil portion includes at least two arc portions or surfaces that act to direct the airflow down to the trailing airfoil portion in a manner that stabilizes vortexes that may form in the region of changing thickness.

A propeller includes a blade free to rotate. A first stop is positioned to mechanically engage one or both of a first portion of the blade and a first structure coupled to the blade when the blade is in a first position at a first end of the rotational range of motion. A second stop is positioned to mechanically engage one or both of a second portion of the blade and a second structure coupled to the blade when the blade is in a second position at a second end of the defined rotational range. The blade rotates to the first position against the first stop when the propeller is rotated in a first direction and to the second position against the second stop when the propeller is rotated in a second direction.

A propeller includes a blade free to rotate. A first stop is positioned to mechanically engage one or both of a first portion of the blade and a first structure coupled to the blade when the blade is in a first position at a first end of the rotational range of motion. A second stop is positioned to mechanically engage one or both of a second portion of the blade and a second structure coupled to the blade when the blade is in a second position at a second end of the defined rotational range. The blade rotates to the first position against the first stop when the propeller is rotated in a first direction and to the second position against the second stop when the propeller is rotated in a second direction.

A main rotor blade assembly for a rotary wing aircraft is provided including a main rotor blade root region, a main rotor blade inboard region arranged outboard of said main rotor blade root region, a main rotor blade main region arranged outboard of said main rotor blade inboard region, and a main rotor blade tip region arranged outboard of said main rotor blade main region. At least one of chord, twist, sweep, airfoil shape, and thickness/chord of the main rotor blade assembly has been optimized to achieve balanced high speed forward flight and hover relative to both efficiency and high thrust capability.