DEDICATED DISPLAY SYSTEMS

Description

Display Driver Unit

Attitude Director Indicator (ADI)

Horizontal Situation Indicator (HSI)

Alpha/Mach Indicator

Altitude/Vertical Velocity Indicator

Surface Position Indicator

Reaction Control System Command Lights

G-Meter

Head-Up Display

Dedicated Display Systems Summary Data

 

Description

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 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:

Dedicated Display and Control System

Dedicated Display and Control System

 

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

Display Driver Unit

The display driver unit (DDU) is an electronic mechanism that connects the GPCs and the primary flight displays. The display driver unit receives data signals from the computers and decodes them to drive the dedicated displays. The unit also provides dc and ac power for the attitude director indicators and the rotational and translational hand controllers. It contains logic for setting flags on the dedicated instruments for such items as data dropouts and sensor failures.

All display parameters, regardless of their origin, are ultimately processed through the dedicated display subsystem operating program (SOP) software (except 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 (MDM); DDUs send data to the attitude director indicator, horizontal situation indicator, alpha/Mach indicator, and altitude/vertical velocity indicator displays; MDMs provide data for the surface position indicator and reaction control system activity lights. In addition, the HUD electronic units generate video symbology for the head-up display.

The orbiter contains three display driver units: at the commander’s station, at the pilot’s station, and at the aft station. One unit interfaces with the attitude director indicator, horizontal situation indicator, altitude/vertical velocity indicator, and alpha/Mach indicator 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 interfaces with the attitude director indicator at the aft flight station.

Each display driver unit has an associated DATA BUS rotary switch. The commander’s switch is on panel F6, and the pilot’s is on panel F8. The switch for the aft flight station is on panel A6U. Switch 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 display driver unit and its dedicated displays. (Because the flight-critical data buses are assigned to specific orbiter GPCs, 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. See Section 2.6 for detailed data bus information.)

DATA BUS Switch on Panel F6

DATA BUS Switch on Panel F6 

The commander’s attitude director indicator is powered from the MN A DDU LEFT circuit breaker on panel O14 and the MN B DDU LEFT circuit breaker on panel O15 through DDU 1 power supply D, which provides ac and dc power. The pilot’s attitude director indicator is powered from the MN B DDU RIGHT circuit breaker on panel O15 and the MN C DDU RIGHT circuit breaker on panel O16 through DDU 2 power supply D, which also provides ac and dc power. The aft flight station attitude director indicator is powered from the MN A DDU AFT circuit breaker on panel O14 and the MN C DDU AFT circuit breaker on panel O16 through DDU 3 power supply D, which provides ac and dc power.

DATA BUS Switch on Panel F8

DATA BUS Switch on Panel F8 

DATA BUS Switch on Panel A6U

DATA BUS Switch on Panel A6U 

MN A DDU Circuit Breakers on Panel 014

MN A DDU Circuit Breakers on Panel 014 

MN B DDU Circuit Breakers on Panel 015

MN B DDU Circuit Breakers on Panel 015 

MN C DDU Circuit Breakers on Panel 016

MN C DDU Circuit Breakers on Panel 016 

The INSTRUMENT POWER switch on panel F6 supplies main bus A power to the commander’s horizontal situation indicator, alpha/Mach indicator, and altitude/vertical velocity indicator displays, the single surface position indicator, and the main propulsion instruments when positioned to FLT/MPS. The INSTRUMENT POWER switch on panel F8 supplies main bus B power to the pilot’s horizontal situation indicator, alpha/Mach indicator, and altitude/vertical velocity indicator displays and the hydraulic and auxiliary power unit displays. The switch on panel F8 is a two-position ON/OFF switch.

The reaction control system activity lights receive power from annunciator control assemblies.

Attitude Director Indicator (ADI)

The commander’s and pilot’s attitude director indicators are supported throughout the mission; the aft attitude director indicator is active only during orbital operations. The indicators give the crew attitude information as well as attitude rate and attitude errors, which can be read from the position of the pointers and needles.

Power for Alpha/Mach Indicator, Altitude/Vertical Velocity Indicator,

Power for Alpha/Mach Indicator, Altitude/Vertical Velocity Indicator, Horizontal Situation Indicator, and Surface Position Indicator 

INSTRUMENT POWER Switch on Panel F6

INSTRUMENT POWER Switch on Panel F6 

INSTRUMENT POWER Switch on Panel F8

INSTRUMENT POWER Switch on Panel F8 

Attitude Director Indicator

Attitude Director Indicator 

The orbiter’s attitude is displayed to the flight crew by an enclosed ball (sometimes called the eight ball) that is gimbaled to represent three degrees of freedom. The ball, covered with numbers indicating angle measurements (a 0 is added as the last digit of each), moves in response to software-generated commands to depict the current orbiter attitude in terms of pitch, yaw, and roll.

Each attitude director indicator has a set of switches by which the crew can select the mode or scale of the readout. The commander’s switches are located on panel F6, the pilot’s on panel F8, and the aft switches on panel A6U.

The ADI ATTITUDE switches determine the unit’s frame of reference: INRTL (inertial),  LVLH (local vertical/local horizontal), and REF (reference). The INRTL position allows the flight crew to view the orbiter’s attitude with respect to the inertial reference frame, useful in locating stars. The LVLH position shows the orbiter’s attitude from an orbiter-centered rotating reference frame with respect to Earth. The REF position is primarily used to see the orbiter’s attitude with respect to an inertial reference frame defined when the flight crew last depressed the ATT REF pushbutton above the ADI ATTITUDE switch. The REF position is useful when the crew flies back to a previous attitude or monitors an OMS burn for attitude excursions. The switches on panels F6 and F8 are active during ascent, orbital, and transition flight phases but have no effect during entry, the latter part of a return to launch site, or when the backup flight system is driving the attitude director indicators. The switch on panel A6U, like the aft attitude director indicator, is operational only in orbit.

Commander’s ADI Switches and ATT REF Pushbutton on Panel F6

Commander’s ADI Switches and ATT REFPushbutton on Panel F6

Each attitude director indicator has a set of three rate pointers that provide a continuous readout of vehicle body rotational rates. Roll, pitch, and yaw rates are displayed on the top, right, and bottom pointers respectively. The center mark on the graduated scale next to the pointers shows zero rates; the rest of the marks indicate positive (right or up) or negative (left or down) rates. The ADI RATE switch for each indicator unit determines the magnitude of full-scale deflection. When this switch is positioned to HIGH (the coarsest setting), the pointer at the end of the scale represents a rotation rate of 10° per second. When the switch is positioned to MED, a full-range deflection represents 5° per second. In the LOW position (the finest setting), a pointer at either end of the scale is read at a rate of 1° per second. These pointers are “fly to” in the sense that the rotational hand controller must be moved in the same direction as the pointer to null a rate.

Pilot’s ADI Switches and ATT REF Pushbutton on Panel F8

Pilot’s ADI Switches and ATT REF Pushbutton on Panel F8

Aft ADI Switches and ATT REF Pushbutton on Panel A6U

Aft ADI Switches and ATT REF Pushbutton on Panel A6U

Attitude director indicator rate readings are independent of the selected attitude reference. During ascent, the selected rates come directly from the solid rocket booster or orbiter rate gyros to the attitude director indicator processor for display on the rate pointers. During entry, only the pitch rate follows the direct route to the attitude director indicator display. The selected roll and yaw rates first flow through flight control, where they are processed and output to the attitude director indicator as stability roll and yaw rates. (This transformation is necessary because, in aerodynamic flight, control is achieved about stability axes, which in the cases of roll and yaw differ from body axes.) The rate needles strictly display vehicle rate information in all major modes except while in TAEM (MM 305, 603). For ascent, orbit, and most of entry, the HIGH position represents 10° per second, MED represents 5° per second, and LOW represents 1° per second. During TAEM, the ADI rate needles can be used to help fly the proper HAC profile as long as the rate switch is in MED (see table A).

Three yellow needles on each attitude director indicator display vehicle attitude errors. These needles extend in front of the attitude director indicator ball, with roll, pitch, and yaw arranged just as the rate pointers are. Like the rate indicators, each error needle has an arc-shaped background scale with graduation marks that allow the flight crew to read the magnitude of the attitude error. The errors are displayed with respect to the body axis coordinate system and, thus, are independent of the selected reference frame of the attitude display.

The attitude director indicator error needles are driven by flight control outputs that show the difference between the required and current vehicle attitude. These needles are also “fly to,” meaning that the flight crew must maneuver in the direction of the needle to null the needle. For example, if the pitch error needle points down, the flight crew must manually pitch down to null the pitch attitude error. The amount of needle deflection indicating the number of degrees of attitude error depends upon the position of the ADI ERROR RATE switch for each attitude director indicator and the flight phase. For ascent, orbit, and transition, in the HIGH position, the error needles represent 10°, MED represents 5°, and LOW represents 1°. For entry, the needles signify different errors in different phases (see table B).

The SENSE switch on panel A6U allows the flight crew to use the aft attitude director indicator, rotational hand controller, and translational hand controller in a minus X or minus Z control axis sense. These two options of the aft attitude director indicator and hand controllers correspond to the visual data out of the aft viewing (negative X) or overhead viewing (negative Z) windows.

Each attitude director indicator has a single flag labeled OFF on the left side of the display whenever any attitude drive signal is invalid. There are no flags for the rate and error needles; these indicators are driven out of view when they are invalid.

(A) ADI Rate Switch vs. Full Range Deflection

(B) ADI Error Switch vs. Full Range Deflection

(B) ADI Error Switch vs. Full Range Deflection

SENSE Switch on Panel A6U

SENSE Switch on Panel A6U

Horizontal Situation Indicator (HSI)

The horizontal situation indicator for the commander (panel F6) and pilot (panel F8) displays a pictorial view of the vehicle’s position with respect to various navigation points and shows a visual perspective of certain guidance, navigation, and control parameters, such as direction, distance, and course/glide path deviation. The flight crew uses this information to control or monitor vehicle performance. The horizontal situation indicators are active during the entry and landing and ascent/return to launch site phases.

Each horizontal situation indicator provides an independent source to compare with ascent and entry guidance, a means of assessing the health of individual navigation aids during entry, and information needed by the flight crew to fly manual ascent, return to launch site, and entry.

HSI Ascent Displays

During ascent major modes 102 and 103 (first and second stage) and return to launch site, the horizontal situation indicator provides information about the target insertion orbit. The compass card displays heading with respect to target insertion orbit, and north on the compass card points along the target insertion orbit plane. The heading of the body plus X axis with respect to the target insertion orbit is read at the lubber line.

The course pointer provides the heading of the Earth-relative velocity vector with respect to the target insertion orbit plane. The course deviation indicator deflection indicates the estimated sideslip angle, the angle between the body X axis and the relative velocity vector.

The primary bearing pointer during major modes 102 and 103 (pre-TAL abort) is fixed on the compass card at a predetermined value to provide a turnaround heading in the event of a return to launch site (RTLS) abort. During RTLS major mode 601, or post-TAL abort, MM103, the pointer indicates the heading to the landing site runway. The secondary bearing provides the heading of the inertial velocity vector with respect to the target insertion orbit plane.

HSI Entry Displays

The commander’s horizontal situation indicator switches are on panel F6, and the pilot’s are on panel F8. The HSI SELECT MODE switch selects the mode: ENTRY, TAEM, or APPROACH. These Area Navigation modes are different from the Guidance phases with virtually identical names (Entry, TAEM, and Approach and Landing). The ENTRY position enables HSI mode auto switching from Entry through Approach. The HSI SELECT SOURCE switch selects TACAN, navigation, or microwave scanning beam landing system (MLS); the SOURCE switch selects TACAN, navigation, or microwave scanning beam landing system (MLS); the 1,2,3 switch selects one of the three TACAN or MLS units. When the HSI SELECT SOURCE switch is positioned to NAV, the HSI is supplied with data from the navigation processor, and the 1,2,3 switch is not used.

In TACAN or MLS, the horizontal situation indicator is supplied with data derived from the unit specified by the 1, 2, 3 switch.

1, 2, 3 switch selects one of the three TACAN or MLS units. When the HSI SELECT SOURCE switch is positioned to NAV, the HSI is supplied with data from the navigation processor, and the 1, 2, 3 switch is not used.

Horizontal Situation Indicator

Horizontal Situation Indicator

Commander’s HSI SELECT Switches on Panel F6

Commander’s HSI SELECT Switches on Panel F6

Pilot’s HSI SELECT Switches on Panel F8

Pilot’s HSI SELECT Switches on Panel F8 

HSI Display Parameters

Each horizontal situation indicator displays magnetic heading (compass card), selected course, runway magnetic heading, course deviation, glide slope deviation, primary and secondary bearing, primary and secondary range, and flags to indicate validity.

Each horizontal situation indicator consists of a case-enclosed compass card measuring 0° to 360°. At the center of the card is an aircraft symbol, fixed with respect to the case and about which the compass card rotates.

The magnetic heading (the angle between magnetic north and vehicle direction measured clockwise from magnetic north) is displayed by the compass card and read under the lubber line located at the top of the indicator dial. (A lubber line is a fixed line on a compass aligned to the longitudinal axis of the craft.) The compass card is positioned at 0° (north) when the heading input is zero. When the heading point is increased, the compass card rotates counterclockwise.

The course pointer is driven with respect to the horizontal situation indicator case rather than the compass card. Therefore, a course input (from the display driver unit) of zero positions the pointer at the top lubber line, regardless of compass card position. To position the course pointer correctly with respect to the compass card scale, the software must subtract the vehicle magnetic heading from the runway azimuth angle (corrected to magnetic north). As this subtraction is done continuously, the course pointer appears to rotate with the compass card, remaining at the same scale position. An increase in the angle defining runway heading results in a clockwise rotation of the course pointer.

Course deviation is an angular measurement of vehicle displacement from the extended runway centerline. On the HSI, course deviation is represented by the deflection of the deviation bar from the course pointer line. Full scale on the course deviation scale is ±10° in terminal area energy management and ±2.5° during approach and landing. The course deviation indicator is driven to zero during entry. When the course deviation input is zero, the deviation bar is aligned with the end of the course pointer. With the pointer in the top half of the compass card, an increase in course deviation to the left (right) causes the bar to deflect to the right (left). Therefore, the course deviation indicator is a fly-to indicator for flying the vehicle to the extended runway centerline. Software processing also ensures that the course deviation indicator remains fly to, even when the orbiter is heading away from the runway.

Horizontal Situation Indicator Heading Geometry

Horizontal Situation Indicator Heading Geometry

In course deviation geometry, if the orbiter is to the left of the runway, it must fly right (or if the orbiter is to the right of the runway, it must fly left) to reach the extended runway centerline. The corresponding course deviation bar would deflect to the right (or to the left in the latter case). The reference point at the end of the runway is the microwave landing system station. The sense of the course deviation indicator deflection is a function of vehicle position rather than vehicle heading.

Glide slope deviation, the distance of the vehicle above or below the desired glide slope, is indicated by the deflection of the glide slope pointer on the right side of the horizontal situation indicator. An increase in glide slope deviation above (below) the desired slope deflects the pointer downward (upward); the pointer is a fly-to indicator.

The “desired glide slope” is actually only a conceptual term in horizontal situation indicator processing. At any instance, glide slope  deviation is really the difference between the orbiter altitude and a reference altitude computed by Area Nav. This reference altitude may be slightly different than the reference altitude computed by Guidance. Also included in the reference altitude equation are factors for a “heavy orbiter” and for high winds.

Course Deviation Geometry

Course Deviation Geometry

The glide slope indicator computation is not made during entry or below 1,500 feet during approach and landing; therefore, the pointer is stowed, and the glide slope indicator flag is displayed during those intervals.

The primary and secondary bearing pointers display bearings relative to the compass card. These bearings are angles between the direction to true or magnetic north and to various reference points as viewed from the orbiter. For the bearing pointers to be valid, the compass card must be positioned in accordance with vehicle heading input data.

When the bearing inputs are zero, the pointers are at the top lubber line, regardless of compass card position. Like the course pointer, the bearing pointer drive commands are developed by subtracting the vehicle heading from the calculated bearing values. This allows the pointers to be driven with respect to the horizontal situation indicator case but still be at the correct index point on the compass card scale.

Horizontal Situation Indicator Bearing and Range Geometry

Horizontal Situation Indicator Bearing and Range Geometry

When the bearing inputs are increased, the pointers rotate clockwise about the compass card. The pointer does not reverse when it passes through 360° in either direction.

For example, if the primary bearing is 190°, and the secondary bearing is 245°, the bearing reciprocals are always 180° from (opposite) the pointers. The definition of primary and secondary bearing varies with the flight regime.

The horizontal situation indicator is capable of displaying two four-digit values in the upper left (primary range) and right (secondary range) side of its face. Each display ranges from zero to 3,999 n. mi. (4,602 statute miles). Although their meaning depends on the flight regime, both numbers represent range in nautical miles (n. mi.) from the vehicle to various points relative to the primary and secondary runways.

The horizontal situation indicator has four flags –– OFF, BRG (bearing), GS (glide slope), and CDI –– and two barberpole indications that can respond to separate display driver unit commands, dentifying invalid data. OFF indicates that the entire horizontal situation indicator display is invalid because of insufficient power. BRG indicates invalid course, primary bearing, and/or secondary bearing data. GS indicates invalid glide slope deviation. CDI indicates invalid course deviation data. Barberpole in the range slots indicates invalid primary or secondary range data.

When the HSI SELECT SOURCE switch on panel F6 or F8 is positioned to NAV, the entire horizontal situation indicator display is driven by navigation-derived data from the orbiter state vector. This makes the horizontal situation indicator display dependent on the same sources as the navigation software (IMU, selected air data, selected navigational aids), but the display is independent of guidance targeting parameters. When the switch is in the NAV  position, the SOURCE 1, 2, 3 switch is not processed.

HSI Flight Path Geometry-Top View

HSI Flight Path Geometry-Top View

HSI Flight Path Geometry-Side View

 

HSI Flight Path Geometry-Side View

The TACAN or MLS position of the HSI SELECT SOURCE switch should be used only when TACAN or microwave landing system data are available. TACAN data are used during entry to update the navigation state, and are usually acquired about 300 n. mi. from the landing site. MLS has a range of 20 n. mi. and would be selected after the orbiter is on the heading alignment cone.

The glide slope deviation pointer is stowed when the entry mode is selected, and the off flag is displayed. The glide slope indicator in TAEM indicates deviations from the guidance reference attitude ±5,000 feet. The glide slope indicator during approach and landing indicates guidance reference altitude ±1,000 feet. The glide slope indicator is stowed below 1,500 feet and the off flag is in view.

In the entry mode, the compass card heading indicates the magnetic heading of the vehicle’s relative velocity vector. In terminal area energy management and approach, the compass card indicates magnetic heading of the body X axis. In the entry mode, the course deviation indicator is driven to zero with no flag. In terminal area energy management, the course deviation indicator indicates the deviation from the extended runway centerline, ±10°. In approach, the course deviation indicator indicates the deviation from the extended runway centerline, ±2.5°.

In the entry mode, the primary bearing indicates the great circle bearing to the heading alignment cone (HAC) tangency point (way point 1) for the nominal entry point at the selected landing runway. The secondary bearing provides identical data relevant to the secondary landing runway. In terminal area energy management (TAEM), the primary bearing indicates the bearing to way point 1 on the selected HAC for the primary runway while the secondary bearing indicates the center of the HAC for the primary runway. In approach, the primary and secondary bearings indicate the bearing to the touchdown point at the primary runway (way point 2).

In the entry mode, the primary range indicates the spherical surface range to way point 1 for the primary runway via the HAC for the nominal entry point. The secondary range provides identical information relevant to the secondary runway. In TAEM, the primary range indicates the horizontal distance to way point 2 on the primary runway via way point 1. The secondary range indicates the horizontal distance to the center of the selected HAC. In approach, the primary and secondary ranges indicate the horizontal distance to way point 2 on the primary runway.

HORIZ SIT Display (SPEC 50)

HORIZ SIT Display (SPEC 50)

The HORIZ SIT display (SPEC 50) allows the flight crew to configure the software for nominal winds or high head winds. The “XEP” item 7 entry determines the distance from the runway threshold to the intersection of the glide slope with the runway centerline or aim point. The high-wind aim point or close in aim point pushes the intercept point closer to the threshold. The distance selected is factored into the computation of reference altitude from which the glide slope deviation is derived.

Alpha/Mach Indicator

The two alpha/Mach indicators are located to the left of the attitude director indicators on panels F6 and F8. The alpha Mach indicators consist of four tape meters displaying angle of attack (ALPHA), vehicle acceleration (ACCEL), vehicle velocity (M/VEL), and equivalent airspeed (EAS). The two units are driven independently but can have the same data source.

ALPHA displays vehicle angle of attack, defined as the angle between the vehicle plus X axis and the wind-relative velocity vector (negative wind vector). ALPHA is displayed by a combination moving scale and moving pointer. For angles between -4° and +28°, the scale remains stationary, and the pointer moves to the correct reading. For angles less than -4° or greater than +28°, the pointer stops (at -4 or +28°), and the scale moves so that the correct reading is adjacent to the pointer. The ALPHA tape ranges from -18° to +60° with no scale changes. The negative scale numbers (below zero) have no minus signs; the actual tape has black markings on a white background on the negative side, and white markings on a black background on the positive side.

The M/VEL scale displays one of the following: Mach number, relative velocity, or inertial velocity. Mach number is the ratio of vehicle airspeed to the speed of sound in the same medium. The relative velocity is in feet per second in relation to the launch site. Inertial velocity is in feet per second and does not consider the rotational speed of the surface. The actual parameter displayed is always Mach number; the tape is simply rescaled above Mach 4 to read relative velocity (MM 102, 304, 305, 602, 603) or inertial velocity (MM 103, 601). The scale ranges from zero to 27, with a scale change at Mach 4.

HSI Function Matrix

HSI Function Matrix

The ACCEL scale displays vehicle drag acceleration, which is the deceleration along the flight path, normal acceleration, which is acceleration in the normal axis, or total load factor. This is a moving tape upon which acceleration is read at the fixed lubber line. The tape range is –50 to +100 with a scale change at zero feet per second squared. Minus signs are assumed on the ACCEL scale also; the negative region has a black background and the positive side has a white background. (Normal acceleration and total load factor are measured in g’s, with 10 equal to 1 g, 20 equal to 2 g’s, etc.)

The EAS scale is used to display equivalent airspeed. On the moving-tape scale, equivalent airspeed is read at the fixed lubber line. The tape range is zero to 500 knots, and scaling is 1 inch per 10 knots.

Each scale on the alpha/Mach indicator displays an OFF flag if the indicator malfunctions, invalid data are received at the display driver unit, or a power failure occurs (all flags appear).

Acceleration

Acceleration

Alpha/Mach Indicator display

Alpha/Mach Indicator

The AIR DATA switch on panel F6 for the commander and panel F8 for the pilot determines the source of data for the alpha/Mach indicator and altitude/vertical velocity indicator. The NAV position of the AIR DATA switch displays the same parameters (ALPHA, MACH, and EAS) that are sent to guidance, flight control, navigation, and other software users; ACCEL comes from navigation software.

The LEFT and RIGHT positions of the AIR DATA switch select data from the left or right air data probe assembly after successful deployment of the left and right air data probes at Mach 5 for ALPHA, M/VEL, and EAS display. However, the data will not be accurate until the velocity is less than Mach 3.5, due to calibration of the probes. ACCEL is always derived from navigation software during entry. It is driven to zero during terminal area energy management and approach and landing.

Commander/s AIR DATA switch on Panel F6

 

Commander/s AIR DATA switch on Panel F6

Pilot’s AIR DATA Switch on Panel F8

Pilot’s AIR DATA Switch on Panel F8

Altitude/Vertical Velocity Indicator

The altitude/vertical velocity indicators (AVVIs) are located on panel F6 for the commander and panel F8 for the pilot. These indicators display vertical acceleration (ALT ACCEL), vertical velocity (ALT RATE), altitude (ALT), and radar altitude (RDR ALT).

The ALT ACCEL indicator, which displays altitude acceleration of the vehicle, is read at the intersection of the moving pointer and the fixed scale. The scale range is –13.3 to 13.3 feet per second squared, and the scaling is 6.67 feet per second squared per inch. Software limits acceleration values to ±12.75 feet per second squared.

The ALT RATE scale displays vehicle altitude rate, which is read at the intersection of the moving tape and the fixed lubber line. The scale range is –2,940 to +2,940 feet per second with scale changes at –740 feet per second and +740 feet per second. The negative and positive regions are color-reversed: negative numbers are white on a black background and positive numbers are black on white.

The ALT scale, a moving tape read against a fixed lubber line, displays the altitude of the vehicle above the runway (barometric altitude). The scale range is –1,100 feet to +165 n. mi., with scale changes at –100, 0, 500 feet, and +100,000 feet. The scale is in feet from –1,100 to +400,000 and in n. mi. from +40 to +165. Feet and nautical miles overlap from +40 to +61 n. mi..

The RDR ALT scale is a moving tape read against a fixed lubber line. It displays radar altitude (corrected to wheels) during major mode 305, below 9,000 feet (normally not locked on until below 5,000 feet; prior to radar altimeter lock-on, the meter is “parked” at 5,000 feet). The scale ranges from zero to 9,000 feet with a scale change at 1,500 feet. Each scale on the altitude/vertical velocity indicator displays an OFF flag in the event of indicator malfunction, invalid data received at the display driver unit, or power failure (all flags appear).

With the AIR DATA source switch in the NAV position, the ALT ACCEL, ALT RATE, and ALT scales are navigation-derived. The RDR ALT indicator is controlled by the RADAR ALTM switch on panel F7 for the commander and panel F8 for the pilot. RADAR ALTM positioned to 1 selects radar altimeter 1; 2 selects radar altimeter 2.

Altitude/Vertical Velocity Indicator

Altitude/Vertical Velocity Indicator

Commander’s RADAR ALTM Switch on Panel F7

Commander’s RADAR ALTM Switch on Panel F7

The AIR DATA switch is positioned to LEFT or RIGHT to select the left or right air data probe after air data probe deployment at Mach 5. The ALT and ALT RATE scales receive information from the selected air data probe. ALT ACCEL receives navigation data. The RDR ALT scale receives data based on the RADAR ALTM select switch position.

Pilot’s RADAR ALTM Switch on Panel F8

Pilot’s RADAR ALTM Switch on Panel F8

Surface Position Indicator

The surface position indicator is a single display on panel F7 that is active during entry and the entry portion of return to launch site. The indicator displays the actual and commanded positions of the elevons, body flap, rudder, aileron, and speed brake.

The four elevon position indicators show the elevon positions in the order of appearance as viewed from behind the vehicle (from left to right: left outboard, left inboard, right inboard, right outboard). The scales all range from +20 to –35°, which are also the software limits to the elevon commands. The pointers are driven by four separate signals and can read different values, but normally the left pair is identical and the right pair is identical. Positive elevon is below the null line, and negative is above.

The body flap scale reads body flap positions from zero to 100 percent of software-allowed travel. Zero percent corresponds to full up (-11.7°); 100 percent corresponds to full down (+22.5°). The small pointer at 34 percent is fixed and shows the trail position.

Rudder position is displayed as if viewed from the rear of the vehicle. Deflection to the left of center represents left rudder. The scale is +30° (left) to –30° (right), but software limits the rudder command to ±27.1°.

Surface Position Indicator on Panel F7

Surface Position Indicator on Panel F7

The aileron display measures the effective aileron function of the elevons in combination. Aileron position equals the difference between the average of the left and right elevon divided by two. Deflection of the pointer to the right of center indicates a roll-right configuration (left elevons down, right elevons up) and vice versa. The scale is –5° to +5°, with –5° at the left side. The aileron command can exceed ±5° (maximum ±10°), in which case the meter saturates at ±5°.

Surface Position Indicator Elevon Travel

Surface Position Indicator Elevon Travel

Surface Position Indicator Rudder Travel

Surface Position Indicator Rudder Travel

Surface Position Indicator Aileron Travel

 

Surface Position Indicator Aileron Travel

Surface Position Indicator Top View of Open Speed Brake

 

Surface Position Indicator Top View of Open Speed Brake

The speed brake position indicator indicates the actual position on the upper scale and commanded position on the lower scale. The position ranges zero to 100 percent; zero percent is fully closed, and 100 percent is fully open, which corresponds to 98° with respect to the hinge lines. The small point at 25 percent is fixed and represents the point at which the speed brake surfaces and the remainder of the tail form a smooth wedge.

The speed brake command is scaled identically to position and has the same travel limits. It always represents the speed brake auto guidance command. The OFF flag is set only for internal meter problems or during OPS 8 display checkout.

Flight Control System Pushbutton Indicators

The flight control system’s pushbutton indicators transmit flight crew moding requests to the digital autopilot (DAP) in the flight control software and reflect selection by illuminating the effective DAP state. These indicators are located on panel F2 for the commander and panel F4 for the pilot.

The pushbutton indicators are used to command and reflect the status of the pitch and roll/yaw control modes. The PITCH and ROLL/YAW indicators transmit moding requests to the digital autopilot and indicate the effective state of the pitch and roll/yaw DAP channels by lighting. AUTO indicates that control is automatic, and no crew inputs are required. CSS is control stick steering; crew inputs are required, but are smoothed by the DAP (stability augmentation, turn coordination).

The SPD BK/THROT (speed brake/throttle) pushbutton indicator has two separate lights, AUTO and MAN, to indicate that the DAP speed brake channel is in the automatic or manual mode. The pushbutton light indicator transmits only the AUTO request.

The BODY FLAP pushbutton indicator also has separate AUTO and MAN lights, indicating the state of the body flap channel. Like the SPD BK/THROT pushbutton indicator, the BODY FLAP indicator transmits only the AUTO request.

Entry Flight Control System Mode Pushbutton Indicator Light Logic

 

Entry Flight Control System Mode Pushbutton Indicator Light Logic

Commander’s Flight Control System Pushbutton Light Indicators on Panel F2

Commander’s Flight Control System Pushbutton Light Indicators on Panel F2

Pilot’s Flight Control System Pushbutton Light Indicators on panel F4

 

Pilot’s Flight Control System Pushbutton Light Indicators on panel F4

Reaction Control System Command Lights

The RCS COMMAND lights on panel F6 are active during OPS 104-106 and OPS 602 and 603. Their primary function is to indicate reaction control system (RCS) jet commands by axis and direction; secondary functions are to indicate when more than two yaw jets are commanded, and when the elevon drive rate is saturated.

During major modes 301 through 304, until the roll jets are no longer commanded (dynamic pressure exceeds 10 pounds per square foot), the ROLL L and R lights indicate that left or right roll jet commands have been issued by the DAP. The minimum light-on duration is extended so that the light can be seen even during minimum-impulse firings. When dynamic pressure is greater than or equal to 10 pounds per square foot, the ROLL lights are quiescent until 50 pounds per square foot, after which time both lights are illuminated whenever more than two yaw jets are commanded on.

The PITCH U and D lights indicate up and down pitch jet commands until dynamic pressure equals 40 pounds per square foot, after which the pitch jets are no longer used. When dynamic pressure is 50 pounds per square foot or more, the PITCH lights, like the ROLL lights, assume a new function: both light whenever the elevon surface drive rate exceeds 20° per second (14° per second if only one hydraulic system is left).

The YAW L and R lights function as yaw jet command indicators throughout entry until the yaw jets are disabled at Mach 1. The yaw lights have no other functions.

RCS COMMAND Lights on panel F6

G-Meter

The g-meter is a self-contained accelerometer and display unit mounted on panel F7. It senses linear acceleration along the Z axis (normal) of the vehicle. A mass weight in the unit is supported vertically by two guide rods and is constrained by a constant-rate helical spring. The inertial force of the mass is proportional to the inertial force of the vehicle and, hence, to the input acceleration, under conditions of constant acceleration. Displacement of the mass is translated to pointer displacement through a rack-and-pinion gear train, the output of which is linear with input acceleration. The display indicates acceleration from –2 g’s to +4 g’s. The g-meter requires no power and has no software interface. Like all the dedicated displays, it has an external variable incandescent lamp.

 

G-METER on Panel F7

Head-Up Display

The head-up display (HUD) is an optical mini-processor that cues the commander and/or pilot during the final phase of entry and particularly in the final approach to the runway. With minimal movement of their eyes from the forward windows (head up) to the dedicated display instruments (head down), the commander and pilot can read data from head-up displays located in the front of them on their respective glare shields. The head-up display presents the same data presented on several other instruments, including the attitude director indicator, surface position indicator, alpha/Mach indicator, and altitude/vertical velocity indicator.

The head-up display allows out-of-the-window viewing by superimposing flight commands and information on a transparent combiner in the window’s field of view. Since the orbiter avionics systems are digital, and minimal impact on the orbiter was paramount, the head-up display drive electronics were designed to receive data from the orbiter data buses. The head-up display drive electronics utilize, to the maximum extent possible, the same data that drive the existing electromechanical display devices. The orbiter display device uses a CRT to create the image, which is then projected through a series of lenses onto a combining glass.

Head-Up Display and Controls on Panel F6 (Identical on Panel F8)

Head-Up Display and Controls on Panel F6 (Identical on Panel F8)

Head-Up Display and Controls on Panel F6 (Identical on Panel F8)

The head-up display has proved to be a valuable landing aid and is considered the primary pilot display during this critical flight phase.

A HUD POWER ON/OFF switch located on the left side of panel F3 provides and terminates electrical power to the commander’s head-up display on panel F6. A second switch is located on the right side of panel F3 for the pilot’s head-up display on panel F8.

Panel F3

Panel F3

WARNING

A generic hardware problem has been identified in several HUD units. At 13 KFT, the flight director symbol is uncaged to become a velocity vector Velocity VectorCycling HUD POWER after this transition may result in erroneous symbol positioning. Flying these false cues would result in landing short of the runway, at a very high sink rate. (Ref: JSC Memo DF6-90-053)

A three-position MODE switch is located below the HUD. In the NORM position, automatic sequencing of formats and symbology is provided. The TEST position forces up a test display for 5 seconds. Selection of the momentary DCLT position initiates a symbol blanking routine. Successive selections of DCLT will serially remove display elements in the following order. The first activation removes the runway symbology. The second activation removes the airspeed and altitude tapes (replacing them with digital values) and the horizon/pitch attitude scales, but leaves the horizon line when within FOV. The third de-clutter level removes all symbology except for the boresight. A fourth de-clutter attempt will return the HUD to its original form with all symbols displayed.

Approach and Land Display (TAEM Heading Phase); No Declutter

Approach and Land Display (TAEM Heading Phase); No Declutter

Approach and Land Display (Declutter Level 1)

Approach and Land Display (Declutter Level 1)

Approach and Land Display (Declutter Level 2)

Approach and Land Display (Declutter Level 2)

Approach and Land Display (Declutter Level 3)

Approach and Land Display (Declutter Level 3)

Dedicated Display Systems Summary Data

 

Panel F6

Panel F6

Panel F8

Panel F8

Panel A6U

 

Panel A6U