The propeller HO-V 123() is a three bladed single acting fully hydraulically controlled constant speed propeller. The hub is made from forged aluminium alloy to fit to the Lycoming, Teledyne engines, but different flanges are also available. The blades are wood - composite with FRP-covering and leading edge guard.
The pre-selected propeller RPM will be kept constant in the normal operating range by a propeller governor. This propeller uses oil pressure to increase pitch. The travel of the propeller blades is limited by mechanical stops.
In the event of an oil pressure failure the propeller blades automatically return to the low pitch stop and the propeller can be used as a fixed pitch unit. The propeller RPM has to be adjusted and controlled by the throttle only, but the flight may be continued.
For special applications the propeller uses oil pressure to decrease pitch. In this case counterweights have to be used to turn the propeller blades towards coarse pitch. In the event of oil pressure failure the propeller blades automatically go to the high pitch or feathering stop.