The first Apollo Lunar Module Pilot explains gimbal lock with my Apollo 8-ball

His name tag from his Apollo 9 EVA, the first of the Apollo program, is in the background.

At first, they thought they could use the same FDAI in the CM and LM, but on ascent and roll over from the moon, the FDAI would go into gimbal lock when using the CM North axis orientation. So they switched the LM FDAI axis to West.

Photo by Julie Sparenberg
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