An Apollo Guidance Computer (AGC) unit was installed in both the LM and Command Module. The AGC handled all of the navigation and automatic control functions on the spacecraft. Not only did it act as a navigational instrument but it also served as a digital autopilot. Propulsion and RCS were controlled by the AGC. The interface to the AGC was through the Digital Display Keyboard (DSKY).
EL3D faithfully represents the primary flight instruments. These instruments include the Flight Director Attitude Indicator (FDAI) ball, X-Pointer, Altitude Tape and Altitude Rate Tape.
The LM was controlled in manual flight with a joystick, just like the one on your desktop. In fact, the LM joystick was much like the ‘new’ joysticks with a twisting yaw axis. In addition, another joystick was mounted perpendicular to the first and located near the left hand of the astronaut. This joystick was known as the Thrust/Translation Controller Assembly (TTCA).
The LM had two primary propulsion systems: Ascent Propulsion System (APS) and Descent Propulsion System (DPS). The DPS was located in the bottom stage and used for braking and landing. The APS was in the upper stage and used to ascend from the moon into lunar orbit.
Guidance operated through the AGC. Each phase of flight was assigned a different computer program. Each of these programs provided guidance and flight control for the specified flight phase.
Landing on the moon safely within a small distance of a predetermined location required massive planning. As the lunar surface loomed closer the need to make adjustments to the flight path to maneuver around craters and boulders became critical. Once a safe landing site had been picked the commander flew the LM manually following prescribed procedures for rate of descent and trajectory. Fuel management was a critical factor.