Avionics Bending: COLLINS Attitude Director Indicator (ADI) (Analysis)

Thanks to Lee King at Boneyard2U I found a set of original L-1011 ADIs. The ADIs are made by Collins Radio Company of Cedar Rapids, Iowa and are from the early 1970s. Unlike the SFENA ADIs that I blogged about several months ago these ADIs do not use the ARINC 429 protocol. They are purely driven by synchs and resolvers which makes them a lot less friendly to connect to modern computers than the SFENA ARINC 429 devices. The exact type of the instruments are 622-1389-001. Power input for the device is rated at 115VAC 400Hz with 5VAC/DC for lighting and the decision height (DH) annunciator.  

The pictures below show the ADI with the radio altitude indicator. Not all ADIs had this feature ... the instruments that I have do not have the Radio Altitude Shutter and the associated indicator as shown below.

A really interesting feature is the APPROACH GATE target. This is somewhat unique to this ADI. In other words you used this target to fly the aircraft down the ILS approach path ... just point the fixed aircraft symbol at the target and your there.  Below is an image of what that target looks like in real life:

Approach Gate in Magenta

Let's open the instrument up. The first image is the instrument from the top. What you can see right away is that there is no big sphere in the instrument as we had in the SFENA. The pick indication is accomplish with a "tape". 

Image 1: TOP

The top image shows the electronics in the back of the instrument and the large pointer for the Roll Out Pointer. The flight director bars, which are the yellow pointers on the left of the image, are actually biased out of sight in the top view. 

Image 2: Left

The left hand side pictures shows the square box for the pitch tape (in the right hand third of the instrument). 

Image 3: Bottom 

In the bottom view we can see the large pointer for the FAST/SLOW indicator. On the right hand side we see the underside of the bus board for the electronics.

Below are two more images of the box with the attitude tape in it and the mechanics that drive it. It's a very interesting mechanism. One limitation that this mechanism has is that you can not "roll" through the complete pitch regime. In other words the range of the instrument is +/- 90º pitch and 360º roll.