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indicator (RMI) with either one needle or dual needle. Fixed- card ADF (also known as the relative bearing indicator (RBI)) always indicates zero at the top of the instrument, with the needle indicating the RB to the station. Figure 9-3  indicates an RB of 135°; if the MH is 045°, the MB to the station is 180°. (MH + RB = MB to the station.) 

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The movable-card ADF allows the pilot to rotate the aircraft’s present heading to the top of the instrument so that the head of the needle indicates MB to the station and the tail indicates MB from the station. Figure 9-4  indicates a heading of 045°, MB to the station of 180°, and MB from the station of 360°. 

The RMI differs from the movable-card ADF in that it automatically rotates the azimuth card (remotely controlled by a gyrocompass) to represent aircraft heading. The RMI has two needles, which can be used to indicate navigation information from either the ADF or the VOR receiver. When a needle is being driven by the ADF, the head of the needle indicates the MB TO the station tuned on the ADF receiver. The tail of the needle is the bearing FROM the station. When a needle of the RMI is driven by a VOR receiver, the needle indicates where the aircraft is radially with respect to the VOR station. The needle points the bearing TO the station as read on the azimuth card. The tail of the needle points to the radial of the VOR the aircraft is currently on or crossing. Figure 9-5  indicates a heading of 360°, the MB to the station is 005°, and the MB from the station is 185°. 

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## Function of ADF 

The ADF can be used to plot your position, track inbound and outbound, and intercept a bearing. These procedures 

