According to one aspect, a lubricant level sensing system for an actuator is provided. The lubricant level sensing system includes a pressure port in an outer housing of the actuator, a pressure sensor, and a pathway from the pressure port to the pressure sensor. The pathway establishes fluid communication between the pressure sensor and a free volume of an internal cavity of the outer housing relative to a lubricant level in the internal cavity such that the pressure sensor detects a pressure of the free volume used to derive the lubricant level.

A method of selectively preventing flapping of a rotor hub includes providing a flapping lock proximate to a rotor hub and shaft assembly and moving the flapping lock from an unlocked position to a locked position, the flapping lock operable in the locked position to prevent at least some flapping movement of the rotor hub relative to the shaft, the flapping lock operable in the unlocked position to allow the at least some flapping movement of the rotor hub relative to the shaft.

A method of selectively preventing flapping of a rotor hub includes providing a flapping lock proximate to a rotor hub and shaft assembly and moving the flapping lock from an unlocked position to a locked position, the flapping lock operable in the locked position to prevent at least some flapping movement of the rotor hub relative to the shaft, the flapping lock operable in the unlocked position to allow the at least some flapping movement of the rotor hub relative to the shaft.

A linear actuator is provided. The linear actuator comprises: a body; a shaft adapted to move linearly relative to the body; a driver adapted to drive the linear movement of the shaft; and a shape memory alloy component configured to compensate for thermal expansion or contraction of the linear actuator due to a change in temperature thereof.

A linear actuator is provided. The linear actuator comprises: a body; a shaft adapted to move linearly relative to the body; a driver adapted to drive the linear movement of the shaft; and a shape memory alloy component configured to compensate for thermal expansion or contraction of the linear actuator due to a change in temperature thereof.

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.

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 gurney flap arrangement includes: an airfoil 2 with a trailing edge 6 and an opening 14 in a surface 8 of the airfoil 2; a gurney flap 1 having a first position in which at least a portion of the gurney flap 1 extends through the opening 14 and projects outwardly from the airfoil surface 8, and a second position in which the gurney flap 1 does not project from the airfoil surface 8 or projects outwardly from the airfoil surface 8 to a lesser extent; and a gurney flap actuator 3 for moving the gurney flap 1 between at least the first position and the second position.

A gurney flap arrangement includes: an airfoil 2 with a trailing edge 6 and an opening 14 in a surface 8 of the airfoil 2; a gurney flap 1 having a first position in which at least a portion of the gurney flap 1 extends through the opening 14 and projects outwardly from the airfoil surface 8, and a second position in which the gurney flap 1 does not project from the airfoil surface 8 or projects outwardly from the airfoil surface 8 to a lesser extent; and a gurney flap actuator 3 for moving the gurney flap 1 between at least the first position and the second position.

According to one aspect, a lubricant level sensing system for an actuator is provided. The lubricant level sensing system includes a pressure port in an outer housing of the actuator, a pressure sensor, and a pathway from the pressure port to the pressure sensor. The pathway establishes fluid communication between the pressure sensor and a free volume of an internal cavity of the outer housing relative to a lubricant level in the internal cavity such that the pressure sensor detects a pressure of the free volume used to derive the lubricant level.