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.
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