Semi-automatic collective pitch mechanism for a rotorcraft

Disclosed is a jump take-off rotorcraft rotor head comprising: (i) a rotor head control frame; (ii) two or more rotor blade attachment means, wherein said rotor blade attachment means are rotatably attached to said rotor head control frame to rotate about a rotor axis, and pivot through a flapping and/or teetering hinge, and have a pitch angle; (iii) pitch angle changing means for collectively changing said pitch angle; (iv) centrifugal pitch stop mechanism having an activation point and comprising: (a) one or more centrifugal plates, and (b) a pitch stop, wherein (a) or (b) is attached to or incorporated into the pitch angle changing means; and (v) means for directing a control input to said pitch angle changing means; wherein said centrifugal pitch stop mechanism is configured to attain an activated state such that the centrifugal plates are provided for interaction with said pitch angle changing means through said pitch stop; wherein said activated state must be provided when simultaneously: the rotational speed about said rotor axis is greater than said activation point and when a control input is provided; wherein said activation point is less than the minimum rotational speed about said rotor axis that is required for flying the rotorcraft; and wherein said interaction with said pitch angle changing means through said pitch stop facilitates and collectively maintains said pitch angle such that rotor blades attached to the rotorcraft rotor head can be sustained at a predetermined pitch angle which is suitable for sustained flight of the rotorcraft. Also disclosed are rotor systems comprising a rotor head as defined above and two or more rotor blades. Rotorcraft and gyroplane type aircraft comprising the rotor head are also provided. The rotor head does not utilise a swash-plate, and the moving parts of the collective are only required when there is a need to perform an ultra-short take-off. The rotor head therefore has mechanical simplicity, reliability and prolonged lifetime facilitated through reduced mechanical wear. The rotor head also provides flight at fixed collective pitch in a similar manner to a conventional fixed pitch gyroplane. This therefore makes it compatible with existing pilot training regimes, and places less burden on the pilot as for fully collectively adjustable autorotative rotor heads known from the prior art.