Chapter 12

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SYSTEM DESCRIPTION

 

ATTITUDE SYSTEM

 

Signal Sources

 

Inertial Reference System (IRS) - GLASS & COMBO GPS

 

The IRS supplies attitude and heading to navigation instruments and aircraft position to the FMC. It also supplies magnetic heading, ground speed, and wind information. The IRS employs two Inertial Reference Units. (IRUs). Each IRU senses attitude changes through three ring-laser gyros, one gyro for each axis of rotation. Attitude signals from the IRS are the sole sources of attitude information to the primary aircraft systems.

 

Attitude Heading Reference System (AHRS) - COMBO NO GPS 

 

Aircraft attitude information is supplied by AHRS. AHRS-1 supplies the captains ADI, and AHRS-2 supplies the first officer's ADI and the flight recorder. Both AHRS supply attitude information to both flight guidance computers.

 

Vertical Gyros (VG) - STEAM

 

These aircraft have 3 vertical gyros: VG-1, VG-2, and AUX VG. Normally VG-1 supplies the captain's ADI, and VG-2 supplies the first officer's ADI and the flight recorder. All gyros supply attitude data to both flight guidance computers. 

 

ATTITUDE DIRECTOR INDICATOR (ADI)

 

The attitude director indicator (ADI) provides attitude reference, flight director command bar, localizer deviation, glide slope, and slow fast speed reference. A bank pointer at the top of the instrument is marked at 10, 20, 30, 45, and 60 degrees of bank. At the bottom of the ADI, a ball in a liquid-filled race provides slip indications. 

 

GLASS & COMBO - The ADI appears on a CRT screen as part of the primary flight display (PFD). ADI design and symbology are similar, but the digital format allows for additional information. 

 

STEAM - These aircraft utilize conventional analog ADIs.

 

The ADI utilizes a fixed delta-shaped aircraft symbol displaying pitch and roll attitude against a moving scroll. When the flight director is operating, V-shaped command bars indicate desired roll and pitch attitude. Chapter 3 describes the flight director system. 

 

Glide slope scale is on the left side of the instrument. A slow-fast indicator (described in chapter 3) is on the right  side. 

 

STEAM - A decision height light on the upper right corner of the ADI comes on when the aircraft is at or below the selected radio altitude decision height. 

 

Fail Flags

 

Fail flags monitor the following functions:

 

    FLAG            CONDITIONS

 

    ATT                Attitude data unreliable

 

    FD                  Flight director unusable (command bars may drive out of view)

 

    SPEED           Slow-fast display unusable

 

    GS                  Glide slope unusable (Must be tuned to ILS frequency)

 

    RUNWAY     Localizer or radio altimeter unusable (Must be tuned to ILS frequency)

 

 

HEADING SYSTEM

 

Two separate systems provide magnetic heading to the autopilot/flight director systems, flight recorder, ND/HSI/RDMI/RMI/CI compass cards, and VHF NAVs. The normal heading signal flow crosses the cockpit, with each ND/HSI receiving the same signal as the RDMI/RMI/CI on the opposite side.

 

HORIZONTAL SITUATION INDICATOR (HSI)

 

The horizontal situation indicator (HSI) displays magnetic heading, VOR/LOC/GS deviation, VOR to-from ambiguity, DME distance, and selected course. Glide slope and to-from indicators appear when appropriate frequencies are set. 

 

GLASS & COMBO - The HSI appears on a CRT screen as part of the Navigation Display (ND). HSI design and symbology are similar, but the digital format allows for additional features.

 

Heading and course setting

 

The heading select knob on the flight guidance control panel (FGCP) positions the ND/HSI heading bugs. The course selector on the NAV radio control panel positions the course pointer.

 

DME Display

 

GLASS & COMBO GPS - DME information is displayed on top of each RDMI and is also displayed on the upper left and right sides of the ND when in the ROSE or ARC modes (distance to waypoint (DTW) is displayed in MAP mode).

 

COMBO NO GPS - DME information is displayed on the upper left and right sides of the ND.

 

STEAM - Display DME-1 and DME-2 in windows at the top of each HSI.

 

Glide Slope Display

 

Glide slope scale is on the left side of the instrument.

 

ADF Bearing Pointers

 

GLASS & COMBO - When selected, a blue pointer on the ND indicates bearing to/from the station. A small pointer symbol labeled ADF-1 appears on the lower right of the display

 

ND/HSI Flags

 

Flags for heading, glide slope, and/or navigation (VOR/LOC) appear in the ND/HSI if the respective signals are unusable.

 

 

RADIO DISTANCE MAGNETIC INDICATOR (RDMI) - GLASS & COMBO GPS

 

 

Each RDMI displays distance information from DME-1 and DME-2 distance and heading information from the respective IRU. The left VOR/ADF selector references the single-line bearing pointer to either VOR-1 or ADF-1. The right VOR/ADF selector references the double-line bearing pointer to either VOR-2 or ADF-2. If the selected ADF is not available the pointer parks at the 3 o'clock position.

 

A HDG flag comes into view when heading information is unusable. When VOR is selected, bearing pointer failure flags come into view if the signals are unusable or ILS frequency is selected.

 

RADIO MAGNETIC INDICATOR (RMI) - COMBO NO GPS

 

 

AHRS equipped aircraft have radio magnetic indicators (RMIs). The bearing pointers have push button selector switches. An indicator above the switch points to the selected source. If the selected ADF is not available the pointer parks at the 3 o'clock position. The left VOR/ADF push-button references the single-line bearing pointer to either VOR-1 or ADF-1. The right VOR/ADF push-button references the double-line bearing pointer to either VOR-2 or ADF-2.

 

A HDG flag comes into view when heading information is unusable. When VOR is selected, bearing pointer failure flags come into view if the signals are unusable or ILS frequency is selected.

 

COMPASS INDICATOR (CI) - STEAM

 

 

These aircraft have compass indicators (CI) which display magnetic heading and radio bearings. The left VOR/ADF selector references the single-line bearing pointer to either VOR-1 or ADF-1. The right VOR/ADF selector references the double-line bearing pointer to either VOR-2 or ADF-2. If the selected ADF is not available the pointer parks at the 3 o'clock position. 

 

An OFF flag comes into view when heading information is unusable.

 

 

ELECTRONIC FLIGHT INFORMATION SYSTEM (EFIS) - GLASS & COMBO

 

 

ADI, HSI, radio altimeter, and marker beacon indications are similar to those on the analog aircraft except they are displayed on CRT screens called Display Units (DUs). The ADI, radio altimeter, and marker beacon appear on the upper DU, called the Primary Flight Display (PFD). The HSI and FMS navigational information (GLASS & COMBO GPS) appear on the lower DU, which is called the Navigational Display (ND). These displays, along with their associated components, are referred to as the ELECTRONIC FLIGHT INSTRUMENT SYSTEM (EFIS). 

 

 

 

EFIS Control and Dimming Panel

 

The PFD and ND are controlled by the EFIS Control and Dimming Panel to the right of the PFD. 

 

 

Clicking the middle knob will change the displays to "compacted" format, where essential elements of both the PFD and CD are combined on a PFD display. This feature is used if the ND fails. 

 

The DH knob on the upper right selects a decision height. Decision height indications are explained in chapter 7.

 

 

Primary Flight Display (PFD)

 

The PFD is dominated by the digital ADI that is similar in design to the mechanical ADI, with the same bank indicator, pitch scales, and a similar delta shaped airplane symbol. For navigation, the PFD has a single-cue flight director V-bar and a localizer deviation indicator with a rising runway. The GPS equipped aircraft also have a Cross Track deviation Scale located in the same position as the Localizer Deviation Indicator. The PFD also has a slow-fast scale and a standard glide slop deviation display.

 

Marker Beacon Symbols

 

Marker beacon passage is indicated by the appearance of color-coded circles on the PFD to the lower right of the ADI. These circles enclose the appropriate letter to indicate the marker being passed: "O" for outer marker, "M" for middle marker, and a white "I" for inner marker. The marker symbol flashes like other marker beacons and standard aural tones feed through the audio control panel.

 

EFIS Radio Altimeter

 

The radio altimeter is displayed on the right side of the PFD. Radio altimeter is described in chapter 7.

 

 

Navigation Display (ND)

 

GLASS & COMBO GPS - Each ND can be selected to present displays of ROSE, ARC and MAP modes. The MAP mode is presented in a format similar to an aeronautical chart. 

 

COMBO NO GPS - Each ND can be selected to present displays of ROSE and ARC modes only.

 

ROSE Mode Display

 

The ROSE mode display is almost identical to a conventional HSI.

 

 

ROSE mode is a 360-degree compass rose with aircraft position at the center. A digital readout of the heading is above the lubber line. The Heading Select Cursor is a green symbol. It is positioned by the FGCP Heading Knob.

 

DME information is presented in the upper left and right corners of the ND in ROSE or ARC modes.

 

GLASS - Distance to waypoint (DTW) is displayed in MAP mode.

 

A VORor ILS annunciation just below the DME-1 readout indicates which signal is tuned on the associated VHF NAV radio. 

 

GLASS -NAV1 annunciation replaces VOR or ILS when MAP mode is selected.

 

The course pointer is set with the CRS select knob on the associated VHF NAV control panel.

 

The ROSE mode has standard course deviation, to-from, and glide slope displays.

 

The ADF-1 bearing pointer can be selected on the EFIS Mode Select Control Panel. The ADF bearing pointer is identified by a readout on the lower right on the display. 

 

 

ND ARC Mode Display

 

The ND ARC mode is an expanded view of the top third of the ROSE mode display. This provides greater detail and facilitates interpretation.

 

 

In the ARC mode, the aircraft symbol is at the bottom of the display. A 100-degree segment of the compass rose is at eh top of the display. The green heading cursor is the same symbol as in the ROSE display, but is connected to the aircraft symbol by a dotted line. The line extends slightly beyond the center of the aircraft symbol to aid in locating the cursor when it is aft of the aircraft. When the cursor is being moved, an additional cursor symbol appears on the right of the display along with a digital readout of the selected heading. Once the cursor is stationary, the additional cursor and readout disappear after a few seconds. 

 

The course pointer is set with the CRS select knob on the associated VHF NAV control panel. As the course pointer is being set, a digital readout of the course pointer position (similar to the heading cursor position readout) appears on the right of the display. It disappears a few seconds after the course pointer stops moving.

 

In ARC mode, the to-from VOR pointers are replaced by TO and FROM messages. Otherwise, symbology is the same as in the ROSE mode.

 

 

ND Mode Select Control Panel

 

The ND Mode Select Control Panel is located on each pilots sidewall.

 

 

LOCATION: HIS Control Panel

 

The left knob selects the ROSE, ARC, and MAP modes.

 

The center knob selects the ADF-1 bearing pointer.

 

The right knob selects ranges for the MAP mode from 10 to 320 miles.

 

The N-AID controls the display of the two VOR-DME navaids.

 

 

EFIS Compacted Mode

 

If the ND fails, both PFD and ND information can be displayed on the PFD in a compacted format. 

 

 

The compacted mode is basically the PFD display with the top half of the ND ROSE mode display at the bottom. Aside from the fact that both displayed are somewhat miniaturized, their appearance and symbology are the same as in the normal displays. The only difference is that the ADI does not have the rising runway symbol. 

 

Use the center knob on the EFIS Control and Dimming Panel to select the compacted mode. 

 

 

INERTIAL REFERENCE SYSTEM 

 

The IRS supplies attitude and heading to navigation instruments and aircraft position to the FMC. It also supplies magnetic heading, ground speed, and wind information. The IRS employs two Inertial Reference Units. (IRUs). Each IRU senses attitude changes through three ring-laser gyros, one gyro for each axis of rotation. Attitude signals from the IRS are the sole sources of attitude information to the primary aircraft systems. 

 

Each IRU has a 24 VDC back-up battery, independent of the aircraft battery, and will provide 30 minutes of IRS operation if the primary power source is interrupted or fails. If primary power is lost on the ground and the IRUs are not OFF, a mechanic call horn will sound continuously to warn ground personnel that the IRU batteries are being depleted. 

 

Mode Select Unit (MSU)

 

 

 

Mode Selectors

 

The Mode Select Unit has a four position control switch for each IRU: OFF, ALN, NAV and ATT.

 

All power is removed when OFF is selected. 

 

Selecting ALN (align) permits the IRU to enter and complete alignment. This position is normally used at through stations for quick alignment and is referred to as Align Downmode.

 

Selecting NAV (navigation) permits the IRU to accomplish a full alignment for and automatically enter the navigation mode for normal flight, once the alignment is complete. All normal operations are in the NAV mode. 

 

ATT (attitude) is selected when IRU navigation outputs fail. In this mode only valid attitude information is provided by the IRU. Heading information must be obtained from the RDMI/RMI/CI.

 

 

Annunciation Lights

 

ALIGN Annunciator -  Indicates the IRU is in the alignment or Align Downmode. It flashes when the IRU cannot enter the NAV mode. 

                                    This will occur if the present position is not entered before the end of alignment period or the aircraft was moved

                                    during alignment.

 

ON BATT Annunciator - Indicates that back-up battery power is being used.

 

BAT FAIL Annunciator - The IRU back-up battery voltage is less than 21-VDC and is inadequate to sustain IRS operation during back-up

                                         battery operation.

 

FAULT Annunciator - Indicates an IRS fault. IRU operation is unreliable.

 

 

ALN (Alignments) and NAV Modes

 

Full Alignment

 

ALN mode is initiated by rotating the Mode Selectors from OFF to NAV. Normal ground alignment in the NAV mode takes approximately 2.5 to 10 minutes to accomplish. If the aircraft is moved during the alignment, the IRUs must be turned off and alignment re-accomplished. The ALIGN lights are on until the IRUs transfer to the NAV mode. 

 

Once the alignment process has been initiated, and as long as the aircraft has not been moved, enter present position. This is done through the MCDU, normally during FMC preflight. Refer to the FMC chapter for more information on the FMC position. With the alignment complete and present position entered, the IRUs automatically enter the NAV mode (if the Mode Selectors are in NAV), horizon and heading displays appear on the PFD and ND, and the ALIGN lights extinguish. 

 

Align Downmode (Quick Align)

 

A quick alignment may be accomplished if a realignment is desired and the normal 10-minute period is not available. If a full alignment has been previously completed, this quick alignment may be accomplished by rotating the MSU mode select switch from Nav to ALN and then back to NAV. 

 

NOTE: A quick fix option has been included for those simmers that don't want to mess with aligning the IRS system. Placing the mouse over the IRS annunciator lights and clicking will align the IRS's immediately. You will still have to complete the FMC position initialization if it is not done. Refer to the FMC chapter for information on position Initialization.

 

 

NAVIGATION

 

CONTROLS AND INDICATORS

 

INERTIAL REFERENCE SYSTEM MODE SELECT UNIT - GLASS & COMBO GPS

 

 

LOCATION: Overhead Panel

 

ADVISORY LIGHTS

 

    ALIGN - Indicates IRU is in alignment mode. Light flashes if the position data has not been entered after alignment time completed or if the

                    aircraft was moved prior to alignment completion. 

 

    ON BAT - Comes on anytime IRU primary power is supplied from its back-up battery source. 

 

    BAT FAIL - Indicates back-up battery voltage is insufficient.

 

    FAULT - Indicates that the associated IRU is incapable of continued operation in the present mode.

 

IRS MODE SELECTORS

 

    OFF - Deenergizes system three seconds after selection.

 

    ALN - Initiates alignment mode. IRU aligns its reference axis to local vertical. Provides down-mode "Quick Alignment" capability.

 

    NAV - Normal "ON" position. IRU wull automatically function through alignment mode and enter navigation mode once position data has

                been entered.

 

    ATT - Selects back-up attitude mode for degraded in flight abnormal procedures only.

 

- Indicates respective IRU is providing attitude information only.

 

 

RADIO DISTANCE MAGNETIC INDICATOR (RDMI) - GLASS & COMBO GPS

 

 

 

RADIO MAGNETIC INDICATOR (RMI) - COMBO NO GPS

 

 

 

COMPASS INDICATOR (CI) - STEAM

 

 

 

PRIMARY FLIGHT DISPLAY - GLASS & COMBO

 

 

BANK INDICATOR & HORIZON BAR

 

Bank angle is displayed by a pointer against bank angle index. Roll attitude is shown by horizon bar rotation relative to the fixed airplane sysmbol

 

COMMAND BAR

 

Displays pitch and roll commands from the flight guidance computer.

 

GROUND SPEED INDICATOR - GLASS & COMBO GPS

 

PITCH LIMIT INDICATOR

 

Shows relationship between airplane angle of attack and stick shaker angle of attack. Appears when aircraft is below 1,500 feet AGL or slats are extended.

 

BANK ANGLE INDEX

 

Marked at 10, 20, 40, 45 and 60 degrees.

 

SLOW/FAST POINTER

 

SLOW/FAST indication is referenced to autothrottle SPD/MACH selections. Full deflection either side of center equals approximately 10 knots. 

 

RADAR ALTIMETER DISPLAY

 

Indicates 0 to 2,500 feet.

 

NAV ANNUNCIATOR

 

Indicates NAV source. 

 

GLASS & COMBO GPS - NAV1 displayed when GPS is selected NAV source.

 

MARKER BEACON SYMBOLS

 

I - Inner marker (white), M - Middle marker, O - Outer marker.

 

RISING RUNWAY

 

Moves laterally it indicate deviation from localizer course. When actuated by radar altimeter at 200 feet AGL, starts riding until it appears to touch the fixed airplane symbol at touchdown. Removed from view when an ILS frequency is not selected. 

 

COURSE DEVIATION

 

Indicates localizer deviation when an active localizer frequency is selected.

 

GLASS & COMBO GPS - When GPS is active and the NAV display is in MAP mode, the course deviation shows aircraft deviation from active GPS course.

 

 

PFD COMPACTED MODE

 

 

 

NAVIGATION DISPLAY (ND) - GLASS & COMBO

 

 

TRACK INDICATOR - GLASS & COMBO GPS

 

COURSE & HEADING READOUT

 

Appear temporarily while making setting. Disappear after setting is complete.

 

 

NAVIGATION DISPLAY: MAP MODE - GLASS & COMBO GPS

 

 

DISTANCE TO WAYPOINT

 

Indicates FMS computed distance remaining to active waypoint.

 

ESTIMATED TIME OF ARRIVAL

 

Indicates FMS calculated ETA, in ZULU, to active waypoint.

 

NAV ANNUNCIATOR

 

Indicates that GPS is the active NAV source. A box will appear around the box when aircraft is below 10,000 feet MSL.

 

RANGE LINE SCALE

 

Displayed range is 1/2 the range selected in the EFIS range selector. Compass card represents the full range selected.

 

VERTICAL NAVIGATION DEVIATION INDICATOR

 

Displays FMS calculated vertical path error when VNAV is engaged and in the descent phase of flight. Appears automatically when aircraft passes the FMS calculated top of descent point. A diamond travels along a white vertical line. Full scale deflection equals +/- 1,000 feet.

 

ALTITUDE RANGE SCALE

 

Depicts where the selected altitude set on the FGCP will be reached based on current conditions. 

 

WIND DIRECTION/SPEED

 

Indicates FMS computed wind speed in knots and direction relative to aircraft's current track. Also depicted on ROSE and ARC mode of nav display.

 

 

EFIS CONTROL AND DIMMING PANEL AND MODE SELECT PANEL

 

 

LOCATION: Main Panel

 

DECISION HEIGHT KNOB

 

Sets decision height value 0 to 500 feet.

 

COMPACT KNOB

 

Selects the compact mode on the PFD and turns off the ND.

 

 

 

LOCATION: HSI Panel

 

ADF SELECTOR

 

Turns ON/OFF the ADF bearing pointer.

 

MODE SELECTOR

 

    ROSE - Provides a 360 degree compass rose orientated to a heading up display

 

    ARC - Provides a 100 degree compass segment at the top also orientated to a heading up display.

 

    MAP - Similar to ARC mode except that FMS data is displayed instead of nav information. 

 

VOR WAYPOINT SELECTOR

 

Displays VOR-1 and VOR-2 radio aids on the MAP display.

 

RANGE SELECTOR

 

Selects ranges for the MAP mode.

 

 

ATTITUDE DIRECTOR INDICATOR (ADI) - STEAM

 

 

The items on this indicator operate like the ones described in the PFD section above.

 

TEST SWITCH

 

Pushing the switch causes 20 degree right bank and 10 degree nose up display. ATT fail flag appears during test.

 

 

HORIZONTAL SITUATION INDICATOR (HSI) - STEAM

 

 

The items on this indicator operate like the ones described in the ND section above.

 

 

 

RADIOS AND TRANSPONDER

 

Mouse areas are outlined in orange.

 

VHF NAV RADIOS

 

 

LOCATION: Glareshield

 

 

ADF RADIO

 

 

LOCATION: Radio Panel

 

 

TRANSPONDER

 

 

LOCATION: Radio Panel

 

MODE SELECTOR

 

    STBY - Both transponders powered, but not transmitting.

 

    TA/RA and TA - Not simulated.

 

    XPDR - ATC transponder is activated.

 

ALTITUDE REPORTING SWITCH

 

Selects which CADC provides altitude information to the selected transponder.

 

TRANSPONDER SWITCH

 

Selects the active transponder.

 

 

MAKER BEACON - STEAM

 

 

LOCATION: Main Panel