Abstract: A propeller assembly has a main hub and a propeller hub circumferentially movable relative to the main hub about a main axis of the assembly. Circumferentially spaced propeller blades on the propeller hub are i) circumferentially movable together with the propeller hub relative to the main hub between a first position and a second position against a biasing force, and ii) pivotal about respective radial axes. A pitch linkage mechanism is operatively connected between each propeller blade and the main hub such that each propeller blade is pivotal about the respective radial axis from a first pitch orientation to a second pitch orientation together with movement of the propeller hub relative to the main hub from the first position to the second position responsive to air resistance in the second direction exceeding the biasing force.