Radio Compass in the VSKYLABS C-47B and Real World Operations.
The Radio Compass indicator (RCI or RBI for Radio Bearing Indicator) is tied to ADF#1, while the Radio Magnetic Indicator (RMI - the one with the VOR/ADF) is tied to VOR#1+2/ADF#1+2.
The main difference between the Radio Compass Indicator and the RMI is that the RMI is equipped with a rotating compass card while the RBI is an old-school homing indicator.
The Radio Compass Indicator (RBI/RCI...whatever...) was the simplest form of homing indication. In real-world operations, once the Radio Compass control box was set for homing, the pilot had to maneuver the aircraft until the radio compass indicator read zero. That was the indication that the aircraft is heading for the transmitting station. Then...if he needed to know the Magnetic Bearing...he had to work it out, as followed:
The simplest homing indication was quite complex to use (to understand) because the magnetic bearing is not shown (better say, not being calculated) as it is with the RMI indicator. The pilot must read the relative bearing from the RBI/RCI and then to calculate the Magnetic bearing each time he needed to.
The method is: Magnetic bearing equals relative bearing + aircraft heading.
So, for example, if the aircraft is flying to the West (aircraft heading 270), while the station is exactly Northbound (360), the RBI/RCI will show 090. Then, the pilot must calculate: Relative bearing (090) + aircraft heading (270) = Magnetic bearing (360).
Another example:
Flying heading 300.
Station is Northbound....RMI showing Magnetic Bearing: 360.
Radio Compass Indicator showing 060.
Pilot calculates: 300+060 = 360!
So in the VSKYLABS C-47 these two indicators are indeed biased to the same receiver, however the Radio Compass Indicator allows you to fly in the simplest form of homing navigation, as they did back in the '30s/'40s. RMI is a more advanced instrument which entered service during these years too...
JMH
