A bistable pitch propeller includes a ball, a spring, and a clutch module where the clutch module has a range of rotational movement between a locked end position and a released end position. The clutch module includes a detent, where the ball sits inside and outside of the detent when the clutch module is in the locked end position and released end position, respectively. In response to an input torque and a spring force from the spring, the clutch module rotates toward the released end position and the locked end position, respectively. The bistable pitch propeller also includes an aircraft blade where the aircraft blade is at the first pitch angle and the second pitch angle when the clutch module is in the locked end position and the released end position, respectively.

The invention relates to a compressible and expandable blade for the rotor of a fluid pump having at least two lamellae which are disposed adjacently, are pivo table respectively relative to an axis of rotation of the rotor and moveable relative to each other, and abut against each other in the expanded state of the blade such that they form together a continuous blade surface.

The invention relates to a compressible and expandable blade for the rotor of a fluid pump having at least two lamellae which are disposed adjacently, are pivo table respectively relative to an axis of rotation of the rotor and moveable relative to each other, and abut against each other in the expanded state of the blade such that they form together a continuous blade surface.