Avionics Bending: COLLINS ADI Functional Analysis

I was able to located quite a lot of information on the Collins ADIs used on the L-1011. First up is a functional diagram that shows how the approach gate is being driven. I am actually quite fascinated with this concept of the approach gate because it is such a rather unusual feature.

As you can see in the schematic above, the gate is driven by a number of reference systems. Namely the YAW computer, the PITCH computer and the VHF NAV radio. After all the signal processing, the gate is driven by two motors; one for up and down and another one for left and right. You can see the mechanical linkages for the gate in the pictures of the Collins ADI that I posted yesterday. Another interesting feature of this ADI is the Roll Out pointer. See the schematic for the roll-out pointer below:

The roll out pointer receives data only from the Yaw Computer. The pointer movement is actually driven by Left and Right signal that is combined in an OpAmp.

Lastly, here is a schematic that shows how the Roll and Pitch displays in the ADI are controlled. This is completely synchro driven:

The system has one synchro transmitter for pitch and one for roll. There is a primary and an alternate channel for the pitch and roll source which are: (1) Vertical Gyro 1 and (2) Vertical Gyro 2. The source is selected via the ALT Source panel on both the Captains' and F/Os main instrument panel.