Overview

The dedicated displays provide the flight crew with information required to fly the vehicle manually or to monitor automatic flight control system performance. The data on the dedicated displays may be generated by the navigation or the flight control system software or more directly by one of the navigation sensors. The dedicated displays are located in front of the commander's and pilot's seats and on the aft flight deck panel by the aft-facing windows.

The dedicated displays are the attitude director indicators on panels F6, F8 and A1; horizontal situation indicators on panels F6 and F8; alpha Mach indicators on panels F6 and F8; altitude/vertical velocity indicators on panels F6 and F8; surface position indicator on panel F7; reaction control system activity lights on panel F6; g-meter on panel F7; and head-up display on the glare-shield in front of the commander's and pilot's seats.

Not all of the dedicated displays are available in every operational sequence or major mode. Their availability is related to the requirements of each flight phase.

The display driver unit is an electronic mechanism that connects the general-purpose computers and the primary flight displays. The DDU receives data signals from the computers and decodes them to drive the dedicated displays. The unit also provides dc and ac power for the ADIs and the rotational and translational hand controllers. It contains logic for setting flags on the dedicated instruments for such items as data dropouts and failure to synchronize. The orbiter contains three DDUs: one at the commander's station, one at the pilot's station and one at the aft station.

All display parameters, regardless of their origin, are ultimately processed through the dedicated display processor software (except for the g-meter, which is totally self-contained). The display parameters are then routed to the respective displays through either a DDU or multiplexer/demultiplexer; DDUs send data to the ADI, HSI, AMI and AVVI displays, while MDMs provide data for the SPI and RCS activity lights.

There are three display driver units. One interfaces with the ADI, HSI, AVVI and AMI displays on panel F6 at the commander's station, and the second interfaces with the same instruments on panel F8 at the pilot's station. The third unit interfaces with the ADI at the aft flight station.

Associated with each DDU is a data bus select switch. The commander's switch is on panel F6, and the pilot's is on panel F8. The select switch for the aft flight station is on panel A6. Positions 1, 2, 3 and 4 allow the flight crew to select any one of four forward flight-critical data buses (FC1 through 4) as the data source for that DDU and its dedicated displays. Because the flight-critical data buses are dedicated to specific orbiter general-purpose computers, the data bus select switch also provides a means of assessing the health of individual computers, if they are assigned to FC1, 2, 3 or 4.

The commander's attitude director indicator is powered from the main bus A and B DDU circuit breakers on panels O14 and O15 through DDU 1 power supply D, which provides ac and dc power. The pilot's ADI is powered from the main B and C DDU circuit breakers on panels O15 and O16 through DDU 2 power supply D, which also provides ac and dc power. The aft flight station ADI is powered from the main A and C DDU circuit breakers on panels O14 and O16 through DDU 3 power supply D, which provides ac and dc power.

The instrument power flt MPS/off/flt switch on panel F6 supplies main bus A power to the commander's HSI, AMI and AVVI displays; the single SPI; and the main propulsion instruments when positioned to flt MPS . The instrument power on/off switch on panel F8 supplies main bus B power to the pilot's HSI, AMI and AVVI displays and the hydraulic and auxiliary power unit displays.

The RCS activity lights receive power from annunciator control assemblies.

The DDU contractor is Rockwell International, Collins Radio Group, Cedar Rapids, Iowa.