Stiftelsen
DAKOTA NORWAY
7.7.2 Construction The narrow-type propeller blades ( 6505A-18 ) are made of aluminum alloy. The pitch control range is 18°- 89°. Inside the propeller hub there is a cog arc which can be turned by means of a piston which is able to move in the direction of the propeller-shaft. When the piston is moving forward, the propeller pitch will increase and vice versa. The back side of the piston is normally affected by the oil pressure from the governor and the front side by the oil pressure from the engine.
7.7.3 RPM-control The rpm-controlling governor is located in the front section. The governor is supplied by power and lubrication from the upper part of the propeller gearing. The governor is controlled by an rpm-control lever in the control pedestal through cables. In the lower part of the governor (Hamilton Standard 4G8) there is a cog pump which supplies pressure oil behind the piston through a borehole in the propeller axle. This oil flow is proportional to the engine revolutions because of being forced through an overflow valve which is controlled by an centrifugal limiter in the governor. The oil flow from the governor tends to move the piston forward but it is opposed first by oil pressure in front of the piston - which is equal to the engine lubrication oil pressure and secondly by the propeller blade tendency to move towards low pitch. Rpm-controlling-, i . e . the propeller pitch changing is accomplished by moving the rpmcontrol lever which causes resistance to a spring in the governor. The spring controls the opening of a control valve which allows the oil pressure to reach the back side of the pitch changing piston. It will find a way to a new balance and changes the pitch consequently. The propeller governor control range is 1200-2700 rpm. NOTE: If the governor control cable break, the spring will return the control valve to 2400-2500 rpm position.
01 JAN 2010
SECTION 7 – SYSTEM DESCRIPTION
OCM PART B – C-53D Dakota Norway