Adjustable propeller unit which can be hydraulically reversed

A hydraulically reversible, adjustable propeller unit for aircraft, land vehicles and watercraft, with a propeller with at least two blades, the blade pitch of which is controllable by means of a control unit, whereby a hydraulic connection exists between the rotating propeller and the stationary control unit for controlling the blade pitch, with a spring-preloaded piston which can be actuated by means of a hydraulic fluid in two different pressure ranges, and with adjustable mechanical stop means for the start position, the brake position and the cruising or sailing position, characterized in that the piston (4) is designed as a spring-preloaded double piston consisting of an inner piston (19) and a ring piston (21) arranged around the inner piston, said two pistons being lockable with each other by means of a centrifugal-force locking mechanism (22);

• that the stop means (6) for the start position is designed for limiting the setting range of the locked double piston (4) in order to prevent unintentional reversing at speeds above about 1500 rpm;
• and that the brake position can be reached only when the inner piston is unlocked and the propeller revolutions are below about 1500 rpm when the propeller controller is in the high-pressure range.