Apollo CM Flight Director Attitude Indicator

Apollo Command Module Flight Director Attitude Indicator (FDAI), commonly called the '8 ball,' measuring 7Ë in diameter and 10Ë long, with a partially intact Honeywell label on the side: "Indicator, Attitude Flight [Director], NAA/S & ID Control No. ME432-0168-0011;" the manufacturer's serial number is difficult to discern, but appears to read "10028FSN000[?]." The unit is marked on the housing in orange, "For Engineering Test Only," retains its two umbilical cables, and has several research and development notes on the body: "Bad Pitch Attitude" is written in felt tip on the side; a white label reads, "Bad Pitch, 10-12-82"; and pieces of aluminized tape applied to the bottom read: "OK 8-23-79" and "OK 10-25-82."

Inside the Command Module, the red, black, and white â€Ëœ8 ballâ€â„¢ was used to define the relative position of the spacecraft in three-dimensional space. Pitch and yaw can be read off the ball directly; roll is shown by a pointer around the edge of the 8-ball. Three meters around the display show the rate of rotation around the three axes. Three additional yellow needles in front of the ball graphically display the difference between the current and desired attitude of the spacecraft. Originally designed to be three different panel instruments, the astronauts, many of whom were pilots, lobbied for an all-in-one device similar to the artificial horizon indicator in airplanes.

The later markings and notations on this engineering test unit are likely associated with the early Space Shuttle program; the Lunar Module FDAI was ultimately adapted for implementation on the Orbiters. A distinctive and important navigational instrument from the legendary Apollo spacecraft.