Chapter 7

Flight Instruments & Air Data

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SYSTEM DESCRIPTION

PITOT STATIC

All aircraft have three pitot and five static systems.  All pitot probes and static ports are electrically heated. The captain's pitot-static system supplies CADC-1 and the first officer's system supplies CADC-2. Auxiliary and cabin static systems control cabin pressurization. The aux pitot and alternate static systems supply the standby altitude/IAS indicator.

 

AIR DATA SYSTEMS

Two central air data computers (CADCs) use pitot-static inputs to compute Mach, airspeed, altitude, vertical speed, and temperature. CADC outputs support primary flight instruments, the SAT/TAS indicator, and related aircraft systems. Primary flight instruments (airspeed/Mach, altimeter, and vertical speed indicator) are electrically driven by their respective CADCs.

CADC-2 normally operates the SAT/TAS indicator. While the TAT switch is pressed, temperature display converts from static air temperature (SAT) to total air temperature (TAT). OFF flags cover the readouts if a failure occurs. 

If power to a primary flight instrument is lost, OFF flags appear in  that instrument.

CADC SWITCHING

A CADC select switch on the overhead panel provides the option of operating both sets of flight instruments and the SAT/TAS indicator from one CADC. With the switch in either the BOTH ON 1 or  BOTH ON 2, the CADC light illuminates on the main panel. 

 

FLIGHT INSTRUMENTS

AIRSPEED/MACH INDICATORS

Electrically driven airspeed/Mach indicators have an IAS scale on their circumference and an IAS indicator needle. Mach is displayed in a drum readout at the top of the indicator. A barber-pole Vmo pointer indicates maximum permissible airspeed for the current altitude. Airspeed failure is indicated by an A/S flag and a Mach failure is indicated  by an OFF flag over the Mach readout. There are five airspeed bugs that are located on the outer edge of the airspeed indicator (4 white and 1 orange) These bugs can be set individually or you can set them using the "SET BUGS" button on the TPS report or the Speed Cards. Information on the speed bugs can be found in the Performance Section

The pilots standby altimeter/airspeed indicator displays IAS on a drum, barometric altitude with a drum and a 100 foot pointer, and is a purely pneumatic instrument. 

PRIMARY ALTIMETERS

Primary altimeters display altitudes from -1,000 to 50,000 feet with a drum readout and a 100 foot pointer. Altimeters are electrically driven. Barometric pressure is set by a knob on the front of the instrument. An OFF flag covers the drum readout when altitude data is invalid.

VERTICAL SPEED INDICATORS

Vertical speed indicators display vertical speed from 0 to 6,000 feet per minute, up or down. A VSI FAIL message appears in the top section when vertical data is unusable.

STANDBY HORIZON INDICATOR

A standby horizon indicator provides a standby attitude reference in normal power fails. An adjustment knob erects the horizon and adjust the display. A power flag appears when DC power is lost.

 

OVERSPEED WARNING

The two CADCs operate dual overspeed warning systems. If speed exceeds maximum operating speed, the central aural warning system alternately sounds a clacker followed by "Overspeed" or "Slat Overspeed" until airspeed is reduced to within allowable limits. A test switch permits testing of each overspeed warning system.

 

STANDBY MAGNETIC COMPASS

The standvy magnetic compass is recessed in the ceiling at the right rear of the cockpit. Hinged mirrors on the glare shield can be adjusted for viewing.

 

RADIO ALTIMETERS

The radio altimeter system has an operating range from the surface to 2,500 feet AGL. The system is powered by the Left AC system and supplies data to the GPWS and flight guidance systems. When and ILS is tuned, the radio altimeter system drives a rising runway indicator in the respective ADI/PFD to indicate the last 200 feet AGL.

EFIS RADIO ALTIMETER - GLASS & COMBO

The radio altimeter is displayed as a vertical tape on the right side of the PFD.  The radio altitude tape disappears above 2,500 feet. From 2,500 feet to 500 feet the tape is grey. Below 500 feet it is solid green until within two hundred of ground level. During the last 200 feet a narrow yellow stripe appears on the right side, becoming wider as altitude decreases until the stripe is more yellow than green at ground level. 

DECISION HEIGHT SETTING

STEAM

A DH knob on the radio altimeter indicator positions an index and digital display to the desired decision height. It also references the DH lights on the radio altimeter and ADI to the set DH value. During descent on a steady tone comes on at 50 feet above decision height. At decision height, the tone stops and both DH lights come on. Fail flags appear on both the radio altimeter and ADI rising runway indicator if the displays are not valid. 

GLASS & COMBO

The DH knob on the EFIS control panel sets the decision heights. The set value appears in green text on the upper-right of the PFD and a green triangular pointer appears at the set value on the radio altitude tape. A tone comes on approaching decision height. At decision height, the green DH is replaced by a large amber DH which flashes and the green pointer on the radio altitude tape turns amber.

 

FLIGHT RECORDER

A flight data recorder in the aft cargo compartment collects information on the flight conditions. The unit is powered by the Left AC system. The FLT RECORDER OFF annunciator light comes on if the system is powered or the recording tape is broken. A test switch on the overhead panel powers the recorder for ground test. Normally the digital flight data recorder (DFDR) operates when the parking brake is released and a fuel lever is on. Trip number, flight leg, and trip date are inserted via the flight data entry panel on the overhead. 

 

ALTITUDE ALERT

 

The altitude alert system alerts the cockpit crew by visual and aural signals when approaching, reaching, and/or departing a pre-selected altitude. Desired altitude is set in the altitude window of the digital flight guidance panel. Approaching the set altitude, an amber altitude alert light on the barometric altimeter comes on within 750 feet of the altitude and a tone sounds. The light goes out within 250 feet of the altitude. Subsequent deviation from the set altitude in excess of 250 feet causes the light to flash and a aural  "ALTITUDE" warning. The flashing altitude light and aural warning can be cancelled by selecting a new altitude, by right clicking the altitude select knob, or returning to within 200 feet of the selected altitude.

 

GROUND PROXIMITY WARNING SYSTEM

The GPWS provides visual and aural warning of dangerous conditions of excessive descent rates, excessive terrain closure rates, altitude loss after takeoff, descent without gear or flaps in the landing configuration, and excessive deviation below glide slope.

GPWS SOUNDS

        BANK ANGLE: If the aircraft bank angle exceeds 40 degrees. Will reset when the bank falls below 30 degrees. Accompanied by the

                                     GPWS light.

 

        DON'T SINK: This warning is active during the takeoff mode and is active until the aircraft is above 700 feet. If the aircraft looses 10% of its

                                 altitude, the warning will sound every 5 seconds until the aircraft climbs back above that altitude. Accompanied by the GPWS

                                 light.

 

        GLIDE SLOPE: This mode is active when a glide slope frequency is available and the aircraft is below 1000 feet. When the aircraft descends

                                    below 1 1/2 dots low, the warning will sound every 5 seconds until the condition is corrected. Accompanied by the BELOW

                                    G/S light. This warning can also be canceled using the BELOW G/S button.

 

        SINK RATE: If the aircraft is below 2500 feet and the vertical speed is between -2500 to -3500 fpm, the advisory will sound every 5

                                seconds until the condition is corrected. Accompanied by the GPWS light.

 

        PULL UP: If the aircraft is below 2500 feet and the vertical speed is more that -3500 fpm, the advisory will sound every 5 seconds until the

                          condition is corrected. Accompanied by the GPWS light.

        TOO LOW FLAPS:  Accompanied by the GPWS light. Will sound every 5 seconds when the following conditions are met:

            Radar Altitude less than 200 feet.

            Flaps less than 26 degrees.

            Airspeed less than 190 knots.

        TOO LOW GEAR:  Accompanied by the GPWS light. Will sound every 5 seconds when the following conditions are met:

            Radar Altitude less than 400 feet.

            Gear Up.

            Airspeed less than 190 knots.

        TOO LOW TERRAIN:  Accompanied by the GPWS light. Will sound every 5 seconds when the following conditions are met.:

            Radar Altitude less than 900 feet.

            Airspeed above 250 knots.

            Flaps less than 25 degrees.

            Gear Up.

        ALTITUDE CALL OUTS: The GPWS will make several altitude call outs when you are approaching the landing. The call outs are as

                                                     follows:

            1000, 500, 300, 100, 50,  30 ,10

GPWS CONTROL SWITCHES

A three position control switch on the overhead panel has an OVRD position for inhibiting flap warning during approaches with flaps less than 26 degrees of flaps. NORM position, and a TEST position for checking visual and aural warnings.

 

Flight Instruments & Air Data

CONTROLS AND INDICATORS

ALTIMETER

ALTITUDE ALERT LIGHT

Comes on when approaching or departing a selected altitude.

READOUT

Indicates baro altitude from -1,000 to 50,000 feet in 20 foot increments. The first digit position of the left hand drum is green below 10,000 feet.

100 FOOT POINTER

Makes a full circle for each 1,000 feet.

BARO SET KNOB

Selects barometric pressure values. Sets value to same side CADC readout on the altimeter.

OFF FLAG

Indicates the altimeter readout is invalid or CADC input is lost.

NEG FLAG

Obscures digital readout when altitude is less than zero.

BUG SET KNOB AND INDEX

Sets altitude index bug to desired value.

 

AIRSPEED

 

 

Vmo POINTER

 

Indicates maximum permissible airspeed as related to altitude. 

 

AIRSPEED POINTER

 

Indicates computed airspeed

 

AIRSPEED COMMAND BUG

 

Displays autothrottle selected speed

 

MAX SPD WARN TEST

 

Clacker sound alternates with spoken word "Overspeed". Momentary switch checks captain's (system 1) or first officer's (system 2) warning.

 

MACH READOUT

 

Indicates computed Mach. Minimum readout is .150. OFF flag appears when data is unusable.

 

A/S FLAG

 

Appears when airspeed unusable.

 

AIRSPEED REFERENCE BUGS

 

The airspeed bugs can be set automatically using the button on the TPS report or the Speed Cards. The bugs can also be set one at a time to any value. The right side of the airspeed indicator has 10 mouse areas to adjust the airspeed bugs. Each bug has 2 mouse areas, one for increasing the value and one for decreasing the value.

 

 

 

VERTICAL SPEED

 

 

VSI needle dissapears and a VSI FAIL message appears when the vertical data is unusable. Driven by the air data computer.

 

 

AIR DATA SWITCHING

 

 

LOCATION: Light is on Main Panel and Switch is on the Overhead.

 

CADC SWITCH

 

When switch is in NORM, captain's altimeter and VSI driven by CADC-1; first officer's Mach/IAS, altimeter, VSI are driven by CADC-2. All instruments can be selected to either CADC.

 

CADC LIGHT

 

Indicates air data instruments switched to alternate source.

 

 

CLOCK

 

 

                                       LOCATION: Main Panel                        LOCATION: Clock panel

 

STEAM

 

ELAPSED TIME KNOB

 

Pressing knob starts, stops, or resets clock.

 

GLASS & COMBO

 

CHR SWEEP SECOND HAND

 

Indicates seconds for stop watch function.

 

CHRONOGRAPH SWITCH

 

Stops, starts, and resets stop watch (CHR) function.

 

GMT INDICATOR

 

Displays UTC in 24 hour format.

 

ELAPSED TIME/CHR INDICATOR

 

Displays elapsed time or stop watch readout. Stop watch readout is displayed if both functions are activated.

 

ELAPSED TIME SELECTOR

 

Controls elapsed time readout in the ET/CHR indicator.

 

    RUN - Elapsed timer starts.

 

    HLD - Stops and holds elapsed time.

 

    RESET - Returns elapsed time readout to zero. Selector trips to HLD when released.

 

 

STANDBY INSTRUMENTS

 

STANDBY MAGNETIC COMPASS

 

 

LOCATION: Top of Glareshild

 

Indicates magnetic heading when viewed through mirrors.

 

The mirror is located on the top of the glareshield. To open the mirror click on the mouse area at the base of the closed mirror (shown in green). To close the mirror, click anywhere on the mirror.

 

 

STANDBY ALTITUDE/AIRSPEED INDICATOR

 

 

LOCATION: Main Panel or Standby Instrument Panel

 

Operates directly from auxiliary pitot and alternate static system.

 

100 FOOT POINTER

 

Pointer indicates a full circle for each 1000 feet of altitude. Indication must be added to the digital readout. 

 

BARO SET KNOB

 

Selects barometric pressure in MB and IN HG windows.

 

DIGITAL READOUT

 

Indicates barometric altitude from -1000 to 50,000 feet in 1000 foot increments. The first digit position of the left hand drum is green below 10,000 feet.

 

STANDBY INDICATED AIRSPEED

 

Read above the lubber line

 

 

STANDBY HORIZON

 

 

LOCATION: Main Panel or Standby Instrument Panel

 

ROLL POINTER

 

Indicates roll attitude on fixed index marks. Index marks are in 10 degree increments.

 

AIRPLANE SYMBOL

 

Indicates pitch attitude against horizon.

 

POWER FLAG

 

Appears when power is lost to indicator or the indicator is caged.

 

PITCH ATTITUDE SCALE

 

Indicates pitch attitude in 5 degree increments up and 10 degree increments down.

 

ERECTION AND TRIM KNOB

 

Click the center of the knob to erect the gyro. Click again to un-cage. Click on either side to adjust the airplane symbol against the horizon.

 

 

RADIO ALTIMETER - STEAM

 

 

DH LIGHTS

 

DH lights on radio altimeter and ADI come on at selected DH. Pressing radio altimeter DH light resets both DH lights.

 

DH BUG

 

Indicates the selected decision height on the radio altitude tape.

 

OFF FLAG

 

Indicates radio altitude is unusable.

 

RA INDEX

 

Fixed index indicates altitude above the ground on a moving tape from 0 to 2,500 feet.

 

DH SET KNOB AND DISPLAY

 

Selects decision height on reference bug and in readout window.

 

RISING RUNWAY

 

Displays last 200 feet AGL by rising to a fixed airplane symbol at touchdown. In view only when an ILS frequency is tuned.

 

 

RADIO ALTIMETER - GLASS & COMBO

 

 

DH SET KNOB

 

Selects decision height on reference bug and DH symbol.

 

DH REFERENCE BUG

 

Indicates the selected decision height on the radio altitude tape.

 

DH SYMBOL

 

DH (green) followed by set value (0-500 feet)

 

At decision height. DH set value is removed, DH symbol changes to separate larger yellow letters and flashes.

 

ALT MESSAGE

 

Appears at 1,000 feet AGL and disappears at 500 feet AGL.

 

RA INDEX

 

Fixed index indicates altitude above the ground on a moving tape from 0 to 2,500 feet.

 

RISING RUNWAY

 

Displays last 200 feet AGL by rising to a fixed airplane symbol at touchdown. In view only when an ILS frequency is tuned.

 

 

ALTITUDE ALERT

 

 

ALTITUDE SELECT KNOB AND DISPLAY

 

Knob selects alert altitude. Clicking cancels preselected altitude and puts out flashing alert light.

 

ALTITUDE ALERT LIGHT

 

Light comes on steady and tone sounds when approaching selected altitude within 750 feet. Light goes out within 250 feet of selected altitude. Light flashes, altitude voice warning, and an aural tone warning sounds when deviating from the selected altitude by 250 feet.

 

 

FLIGHT DATA RECORDER

 

 

LOCATION: Overhead Panel

 

EVENT SWITCH

 

Pressing switch marks DFDR tape to indicate the beginning of an event.

 

INSERT SWITCH

 

Pressing switch enters data selected in display.

 

DATA DISPLAY AND SELECTOR

 

Selects trip number, trip date, and leg for entry on recorder tape.

 

TEST SWITCH

 

Activates the recorder for testing purposes.

 

- Indicates recorder failure or power loss.

 

 

GROUND PROXIMITY WARNING SYSTEM

 

 

LOCATION: Light is on the Main Panel and switch is on the Overhead Panel

 

GPWS CONTROL SWITCH

 

You must click the center of the black cover to open it. Then you click on the upper or lower areas to move the switch.

 

    OVRD - Inhibits flap warnings

 

    NORM - GPWS provides visual and aural warnings of hazardous conditions.

 

    TEST - Provides momentary test of GPWS warnings.

 

BELOW G/S - PUSH TO INHIBIT LIGHT

 

Indicates deviation below glide slope. Accompanied by aural "Glide Slope" warning. Pressing light when between 1,000 feet and 300 feet inhibits the glide slope warning.

 

GPWS LIGHT

 

Indicates an unsafe condition or configuration near the ground. Accompanied by aural warnings that indicate the nature of the unsafe condition.

 

- Indicates GPWS is inoperative.