• Flight Director Attitude Indicator (FDAI) with housing removed.
• Indicator mounts a ball with three axes of rotation, showing the spacecraft attitude in yaw, roll and pitch.
• Short needles on the outer scales indicate attitude rates.
• Longer needles over the indicator face show commanded attitudes from the spacecraft guidance system.

• Red circles centered at yaw 0 and 180 degree poles indicate where the inertial guidance gimbals are in danger of locking (gimbals from two axes aligning with each other) causing loss of attitude reference.

Also see:

Flown Apollo 15 FDAI: