Looking at an article in Flight magazine from March 1945 titled "Sperry Attitude Gyro" that you can find online, the picture of the instrument is interesting: enter image description here

It seems that the orientation of the sphere was upside-down compared to current convention. The dark "earth" was the top part of the sphere and the light "sky" the bottom. Back in those days, the sphere apparently contained the actual rotating gyroscope, so for instance the last illustration in the picture, 30 degree climb, is how it indeed would show up when the sphere is held in constant orientation by the gyroscope and the aircraft is in 30 degrees climb.

At some point this was mechanism and convention apparently changed, because nowadays there is just a partial sphere surface that obviously does not contain the gyro, and the coupling to the gyro is such that it works the other way in the vertical direction. I guess this indeed more natural, with the "sky" being in the upper part of the partial sphere surface. Am I right?

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    $\begingroup$ Related: Why are the colors of the MiG-15's attitude indicator inverted? $\endgroup$
    – ymb1
    Nov 8 '21 at 15:42
  • $\begingroup$ Attitude indicators (AIs) in Soviet Bloc aircraft operated opposite to the way western AIs worked, and cause numerous accidents in pilots converting to western designed aircraft after the fall of the Soviet Union. In these AIs, the background remained fixed, and the little aircraft moved around. In a dive with a left bank, the little aircraft symbol would move lower, over the dark (ground) background, and roll to the left. $\endgroup$ Nov 13 '21 at 15:25

Yes top and bottom were reversed, and there were labels to indicate climb and dive directions. Sperry advertisement circa 1959:

enter image description here


However such indicators were competing with another design from RC Allen, a black background with a white horizontal line:

enter image description here


The white line moved like the AI we know today. So both indicators were showing pitch in an opposed way:

Sperry F3 vs conventional attitude indicator

Sperry F3 vs conventional attitude indicator, source

These confusing conventions may have been a contribution in the Beechcraft Bonanza accident in which Buddy Holly died in 1959: See this video.

The Sperry indicator from this video:

enter image description here

The pitch display of this instrument is the reverse of the instrument [the pilot] was accustomed to; therefore, he could have become confused and thought that he was making a climbing turn when, in reality, he was making a descending turn.


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    $\begingroup$ Initially I had a hard time believing that the illustrations attached to the question could be accurate. I've added a comment to this related answer aviation.stackexchange.com/a/73772/34686 that may help folks understand why the instrument gives "backwards" indications in pitch but not roll. I still feel that this sort of instrument would be incredibly confusing and unintuitive to use. So, for roll, you are supposed to image that the line on the ball represents the horizon and the fixed bar represents the aircraft, but in pitch you are supposed to image the opposite? Yikes! $\endgroup$ Nov 13 '21 at 11:55

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