The VSKYLABS C-47/DC-3 is equipped with the R-1830-90C engine installed. The engine is provided with a single stage, 2-speed supercharger with a low blower ratio of 7.15 to 1 and a high blower ratio of 8.47 to 1. The high gear ratio allows the engine to maintain higher power at greated altitudes than would be possible with only the low ratio.
A two position handle, mechanically connected to a hydraulic control valve, is located below the side window, to the left of the pilot’s seat. The handle has the following positions: LOW BLOWER and HI BLOWER. When the handle is moved to the HI BLOWER position, hydraulic fluid pressure from the main hydraulic system actuates a small hydraulic cylinder located on the rear crankcase of each engine. The actuating cylinder positions an engine oil selector valve, which directs engine oil under pressure to the high blower clutch to shift the clutch into the high ratio position. When the handle is moved to the LOW BLOWER position, the hydraulic fluid pressure actuates the hydraulic cylinders, moving the engine oil selector valves to direct engine oil under pressure to shift the low blower clutches into the low ratio position.
High Blower Indication Lights:
Two 28-volt DC high blower indicator lights are located forward to the supercharger control valve handle. Failure to one or both of these lights to illuminate when the control valve handles are in the HI BLOWER position, is an indication that the supercharger control hydraulic system is not functioning properly.
