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This is a Swissair photo from a DC-7C panel.

enter image description here

Source

I have seen photos on airliners.net of these in DC-6s, VC-118 and Constellations. It appears that other companies besides Bendix made these indicators, but they are similar in appearance and function.

I've searched unsuccessfully for patents, or any other information that would describe what I am asking about:

  1. What are these "45" scales for?
  2. What is the flag in the window used to indicate?
  3. What are these two lines for?
  4. What happens when the test button is pressed, e.g., the loc, glideslope needles move to some position, #5 rotates to some position, #2 flag appears?
  5. What does this "airplane" indicate?
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  • $\begingroup$ If that helps, the reference is MN-97 $\endgroup$ – mins Jun 12 '17 at 7:40
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    $\begingroup$ @mins yes it does! Amazing what you can find when you know what to look for. $\endgroup$ – curious_1 Jun 13 '17 at 0:22
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This is an early version of an HSI. The heading (depicted by the airplane) is either set manually, or it's slaved to a remote compass.

Responding to the question as numbered:

  1. Depicts wind correction angle when tracking a course.
  2. To/From flag
  3. Glide slope reference (too low)
  4. Push to test the warning light. Also push to illuminate while turning to adjust brightness. This may light without a valid heading source from a remote compass/flux valve. It may also be to indicate failure of an internal gyro if so equipped for heading source.
  5. Depicts aircraft the heading
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