Chapter 14

Power Plant

Main Menu

SYSTEM DESCRIPTION

 

GENERAL

 

The airplane is equipped with two Pratt and Whitney JT8D-217A/C axial-flow, bypass turbofan engines. The normal thrust rating is 20,000 lbs and a maximum thrust rating is 20,850 pounds. An automatic reserve thrust (ART) system increases the thrust on the remaining engine from normal to maximum if an engine fails during a max thrust takeoff. The ART system is not simulated. The light, switches, and EPR bugs work as described in this manual, but there is no actual increase in thrust.

 

ENGINE INSTRUMENTS

 

Aircraft use either mechanical engine instruments or electronic displays in a dial/digital format for EPR, N1, N2, and EGT.

 

EPR INDICATOR

 

Engine Pressure Ratio (EPR) indicators receive input from respective engine air inlet and low-pressure turbine discharge pressure probes. Computed EPR provides a relative indication of the engine's thrust.

 

When the set knob on the EPR indicator is in the automatic (in) position, servo-driven chevrons drive to the EPR limit value computed by the thrust rating indicator (TRI) - STEAM & COMBO and the thrust rating panel (TRP) - GLASS.

 

N1 AND N2 INDICATORS

 

The low-pressure compressor (N1) and high-pressure compressor (N2) tachometers show compressor rotor RPM as a percentage. 

 

GLASS - The digital display flashes if RPM is above the max limit.

 

EGT INDICATOR

 

The exhaust gas temperature (EGT) indicators display temperature measured by probes in the exhaust gas path at the turbine exit. 

 

GLASS - The digital display flashes if EGT is above the max limit or is rising too rapidly during start.

 

FUEL FLOW INDICATOR

 

Fuel flow indicators show in pounds per hour to each engine. A fuel-used readout on each indicator displays total amount of fuel used by the engine since the last reset. A fuel used reset switch resets both fuel-used indicators to zero.

 

GLASS - The digital fuel flow display flashes if fuel flow is excessive during start.

 

GLASS - The same digital display is used for fuel flow and fuel used. A push button changes fuel flow to fuel used for approximately 10 seconds.

 

FUEL TEMPERATURE INDICATOR

 

Both fuel temperature indicators are in a single instrument. Each indicator shows the temperature downstream from the fuel sender.

 

GLASS - Fuel temperature is a digital display on the systems display panel.

 

OIL INDICATORS

Each engine has an oil pressure, oil temperature, and oil quantity indicator.

 

GLASS - Oil instruments are digital displays. The oil pressure digital display flashes if oil pressure is above normal range. The oil pressure and temperature indicators have a red and amber lights that come on if the indicator is in the danger or caution range respectively. These lights go out after 5 minutes if the aircraft is on the ground and the respective hydraulic system pressure is less than 500 psi.

 

 

THRUST RATING INDICATOR/THRUST RATING PANEL

 

STEAM & COMBO - Have a thrust rating indicator (TRI) for selecting modes. The TRI also displays RAT (ram air temperature) and EPR LIM (limit) values. 

 

GLASS - Have a thrust rating panel (TRP) for selecting modes. RAT and EPR LIM are displayed on the systems and engine display panels.

 

 

TRI/TRP selections are as follows:

 

    T.O.         - Maximum Thrust Takeoff

    T.O. FLX - Standard Thrust Takeoff

    GA           - Go-Around

    MCT        - Maximum Continuous Thrust

    CL            - Climb

    CR            - Cruise

 

When a mode is selected, the mode selector switch latches in and the mode light comes on The TRI/TRP is connected to the RAT probe and the digital flight guidance computers (DFGCs). The DFGC supplies data for the selected mode to the EPR limit display window.

 

TRI/TRP NO MODE

 

The NO MODE light comes on and a red bar (dashes in the engine display panel on GLASS) appears in the EPR LIM display under the following conditions:

 

    - No mode is selected.

    - Engine anti-ice is selected above 10C RAT on the ground.

    - Wing or engine anti-ice is selected above 14C RAT in flight.

    - Airfoil anti-ice is selected when engine anti-ice is off.

    - MCT, CL, CR is selected with both air conditioning packs off.

    - TO FLX is selected with the ART sWitch in AUTO.

 

TRI/TRP TEST

 

Pushing and holding the test switch on the TRI/TRP disengages and selected thrust mode and inserts a test signal. This drives the RAT to PLUS 12 and the EPR limit display to 2.04. When the test switch is released, the NO MODE light comes on and a red bar (dashes in the engine display panel on GLASS) appears in the EPR LIM display until an active thrust mode is selected.

 

ASSUMED TEMPERATURE CONTROL

 

The assumed temperature selector panel on the center instrument panel is used in conjunction with the TO FLX mode. This mode computes derated thrust for the assumed temperature.

 

GLASS - Assumed temperature is set from the TRP and displayed in the FMA autothrottle window.

 

 

START SYSTEM

 

An electrically controlled, pneumatically actuated valve controls the engine starter. start switches on the overhead engine panel control the start valves. The ignition selector must be out of the OFF position to supply electrical power to the start switches. The associated START VALVE OPEN annunciator light indicates that the valve is open. The engine starter is pneumatically operated by air pressure from the APU or an operating engine. 

 

IGNITION SYSTEMS

 

There are two types of ignition systems used. They are identified with a rotary or lever-lock style switch.

 

ROTARY-SWITCH IGNITION SYSTEM - GLASS & COMBO

 

The aircraft is equipped with a rotary-switch ignition system. It has two independent high-energy ignition systems available to each engine. The systems are labeled A or B and are selected using a single rotary knob located on the overhead panel. The system is powered by the respective left or right AC bus. If normal AC power is not available, the emergency inverter automatically provides ignition power.

 

 

The following ignition system selections and functions are available:

 

    - SYS A 

        or

      SYS B - Supplies power to the selected ignitor (A or B) when the respective fuel lever is on.

    - BOTH - Supplies power to both ignitors when the respective fuel lever is on.

    - OVRD - Bypasses fuel levers and supplies power directly to both ignitors on both engines.

    - OFF    - Removes power from both ignition systems. Removes electrical power to start switches.

 

 

LEVER-LOCK IGNITION SYSTEM - STEAM

 

These aircraft have a three-position, lever-lock ignition selector switch. Ground start and override ignition is powered by the DC System. Continuous ignition is powered from the respective AC bus.

 

The following ignition system selections and functions are availabe:

 

    OVRD               - Provides high energy to all ignitors regardless of start control switches or fuel lever position.

 

    OFF                  - No energy to ignitors.

 

    GRD START

    AND CONTIN - Provides high energy to both ignitors with start switch and fuel lever ON. Provides low energy to one ignitor with start switch

                                OFF and fuel lever ON.

 

 

ENGINE FUEL SYSTEM

 

Tank boost pumps send fuel through a fire shutoff valve on the rear wing spar to the inlet of the engine-driven fuel pump. Fuel pressure is monitored at this point by the INLET FUEL PRESSURE LOW annunciator. Fuel then passes through the two-stage, engine-driven pump.

 

FUEL HEATER

 

The fuel heater is an air-to-fuel heat exchanger between the first and second stages of the engine-driven pump. It is used as required to prevent or remove ice buildup at the fuel filter.

 

Fuel heaters are controlled by fuel heat switches on the overhead panel. Placing a fuel heat switch ON (momentarily) supplies high pressure bleed air to the heater for one-minute cycle. The FUEL HEAT ON annunciator light comes on when the valve opens and goes off when the valve closes. Fuel temperature is measured between the fuel heater and the filter. 

 

FUEL CONTROL

 

The engine-driven pump pressurizes fuel prior to entering the fuel control. Fuel flow is blocked off at the fuel control until the fuel lever is moved out of the off position. The fuel flow transmitter measures fuel delivered to the engine from the fuel control and displays the reading on the fuel flow meter. Heat from engine oil is transferred to the fuel through the fuel/oil cooler.

 

 

ENGINE OIL SYSTEM

 

Oil quantity in the tank is displayed on the oil quantity indicator. Oil pressure is displayed on the oil pressure indicator. A pressure regulating valve normally maintains engine ail pressure at approximately 55 psi. If pressure drops below normal, the L (or R) OIL PRESSURE LOW annunciator and MASTER CAUTION lights come on. The fuel/oil cooler transfers heat from the oil to the fuel. The oil temperature indicator displays the temperature of the oil leaving the cooler.

 

 

THRUST REVERSER SYSTEM

 

Reverse thrust is provided by hydraulically powered, target-type reversers with an actuation time of approximately two seconds. Each engine has a reverser with two deflector doors which form the aft nacelle fairing when stowed. When extended, the doors direct exhaust gasses over and under the nacelle. 

 

Hydraulically-actuated latched on both reverser doors prevent movement out of the stowed position until the thrust reverser lever is moved toward the reverse thrust position. As the thrust reversers unlatch, latch switches turn on the R and L ENG REVERSE UNLOCK lights on the center instrument panel. When the reversers are fully extended, the R and L ENG REVERSE THRUST lights also come on.

 

 

ENGINE SYNCHRONIZATION SYSTEM 

 

When selected, the engine synchronizer system automatically matches N1 or N2 speed of both engines. The system includes an engine sync selector, an annunciator light, and control box. 

 

The engine sync selector switch on the overhead panels has OFF, N1, and N2 positions. In N1 or N2, the control box adjusts the left engine throttle linkage to match left RPM to the right engine. If the selector is in N1 or N2 with the landing gear down, the ENG SYNC ON annunciator light comes on. 

 

When the selector is OFF with the autothrottles engages, engine EPRs are automatically synchronized. The control box trims left EPR within its adjustment range to match the right engine. 

 

 

 

AUTOMATIC RESERVE THRUST (ART)

 

This system detects and engine failure during takeoff and automatically increases the thrust on the operating engine without moving the throttle lever. ART is controlled by the DFGC and can be used with manual throttles or autothrottles. An ART switch with AUTO and OFF positions is on the engine instrument panel.

 

The ART system is a self testing system and requires no action by the pilot. If the self-test fails, the ART INOP annunciator light comes on. Placing the ART switch OFF disables the ART system. The ART INOP annunciator comes on with the switch off. With ART AUTO or OFF, both EPR bugs go to the EPR value computed by the thrust rating indicator or thrust rating panel. 

 

The ART system has a dual-indication light on the center instrument panel. The READY light indicates that the self-test was successful and the ART system is ready to operate. The ART light indicates that ART has activated. ART is activated by a 30% differential in N1 RPM. When ART activates, the DFGC calculates a new EPR limit for the thrust increase commanded by the ART system. The EPR reference bug for the operating engine and the EPR limit readout reset to the new value. 

 

 

Power Plant

 

CONTROLS AND INDICATORS

 

START, IGNITION, AND FUEL HEAT

 

 

LOCATION: Overhead Panel

 

ROTARY SWITCH IGN SELECTOR

 

    SYS A 

      or

    SYS B - Supplies power to the selected ignitor (A or B) when the respective fuel lever is on.

 

    BOTH - Supplies power to both ignitors when the respective fuel lever is on.

 

    OVRD - Bypasses fuel levers and supplies power directly to both ignitors on both engines.

 

    OFF    - Removes power from both ignition systems. Removes electrical power to start switches.

 

LOCK-LEVER IGN SELECTOR

 

    OVRD               - Provides high energy to all ignitors regardless of start control switches or fuel lever position.

 

    OFF                  - No energy to ignitors.

 

    GRD START

    AND CONTIN - Provides high energy to both ignitors with start switch and fuel lever ON. Provides low energy to one ignitor with start switch

                                OFF and fuel lever ON.

 

FUEL HEAT SWITCHES

 

    ON - (momentarily) supplies high pressure bleed air to the heater for one-minute cycle. The FUEL HEAT ON annunciator light comes on 

              when the valve opens and goes off when the valve closes.

 

    OFF - Removes power from fuel heat circuit.

 

ENGINE START SWITCHES

 

    OFF - Removes power from engine start valve.

 

    ON - Provides power to open start valve. When start valve is open, START VALVE OPEN annunciator comes on.

 

 

EPR, N1, EGT, AND N2 - STEAM & COMBO

 

 

LOCATION: Main Panel

 

EPR BUG - Indicates EPR manually selected with knob, or EPR limit mode selected on the thrust rating indicator.

 

CMD READOUT - Indicates EPR selected with knob. Readout is covered with mask when set knob is pushed in.

 

EPR READOUT AND POINTER - Displays actual EPR. A bar bar covers the EPR readout is failure occurs. 

 

EPR SET KNOB - Click on the knob to "pull" it out. Click on the left or right to manually set desired EPR in the CMD readout and on bug. 

                                Click again to "push" it back in and put it back to the auto mode. When pushed in, a mask covers the CMD readout and bug 

                                 is automatically set to EPR limit selected on the thrust rating indicator.

 

N1 TACHOMETER - Small dial is graduated in 1% increments; large dial is graduated in 2% increments. Tachometers are self powered.

 

EGT INDICATOR - Multiply by 100 to get the EGT.

 

N2 TACHOMETER - Small dial is graduated in 1% increments; large dial is graduated in 2% increments. Tachometers are self powered.

 

 

OIL AND FUEL INDICATORS - STEAM & COMBO

 

 

LOCATION: Main Panel

 

OIL PRESSURE - Indicates oil pressure on engine side of main oil filter.

 

OIL QUANTITY - Indicates usable oil in tank.

 

OIL TEMP - Indicates temperature of oil out of fuel/oil cooler.

 

FUEL FLOW/FUEL USED - Dial indicates rate of fuel flow to engine. Digital readout indicates total fuel used by engine.

 

FUEL TEMP - Indicates temperature of fuel after leading the fuel heater.

 

FUEL USED RESET - Momentary. Resets fuel used readout to zero.

 

NOTE - FS does not do a good job of keeping track of fuel when in acceleration mode. For this reason, the fuel used numbers will not be accurate

              when the sim acceleration is above 4X.

 

 

ELECTRONIC ENGINE DISPLAY PANEL - GLASS

 

 

LOCATION: Main Panel

 

EPR LIMIT READOUT - Displays EPR limit for selected operating mode. Dashes appear when EPR limit is unusable.

 

CMD READOUT - Indicates EPR selected with MAN EPR set knob. Readout is blank when set knob is pushed in.

 

EPR BUG - Indicates EPR selected with MAN EPR set knob or EPR limit displayed in EPR LIMIT readout.

 

EPR READOUT AND POINTER - Displays actual EPR. Dashes appear if failure occurs.

 

START LIMIT - Indicates 475C

 

MAN EPR SET KNOB - Click on the knob to "pull" it out. Click on the left or right to manually set desired EPR in the CMD readout and on bug.

                                           Click again to "push" it back in and put it back to the auto mode. When pushed in, CMD readout goes blank and bug is

                                            automatically set to EPR displayed in EPR LIMIT readout.

 

FUEL USED RESET - Momentary. Resets fuel used readout to zero.

 

FUEL FLOW/USED SWITCH - Normally shows fuel flow. When switch is pushed, fuel used displays for 10 seconds.

 

FUEL FLOE/USED READOUT - Normally indicates fuel flow rate to engine. When FUEL FLOE/USED switch is pushed, indicates total fuel

                                                         used by engine.

 

 

ELECTRONIC SYSTEMS DISPLAY PANEL - GLASS

 

 

LOCATION: Main Panel

 

RAT READOUT - Displays ram air temperature in degrees centigrade.

 

FUEL TEMP -  Indicates temperature of fuel after leading the fuel heater.

 

OIL PRESSURE LIGHTS - 40 light comes on below 40 psi. 35 light comes on below 35 psi. Lights go out after 5 minutes on the ground with

                                                hydraulic pressure less than 500 psi.

 

OIL PRESSURE - Indicates oil pressure on engine side of main oil filter.

 

OIL TEMP LIGHTS - 135 light comes on above 135 degrees. 165 light comes on above 165 degrees.

 

OIL TEMP - Indicates temperature of oil out of fuel/oil cooler.

 

OIL QUANTITY - Indicates usable oil in tank.

 

 

THRUST RATING INDICATOR - STEAM & COMBO

 

 

LOCATION: Main Panel

 

RAT READOUT - Displays ram air temperature in degrees centigrade. When a temperature below zero is displayed, the word "minus" follows the

                                numerical value. When a temperature is above zero is displayed, the word "plus" follows the numerical value. A RAT flag

                                appears when RAT is unusable.

 

EPR LIM READOUT - Displays EPR limit for selected operating mode. EPR LIM flag appears when EPR limit is unusable.

 

TEST SWITCH - Pushing switch displays 12 PLUS in RAT readout, and 2.04 in EPR LIM readout. All lights, including the NO MODE light

                              should be off. When switch is released, the EPR LIM flag appears, the NO MODE light comes on, and all the mode switch

                              lights are off. 

 

TO MODE SWITCH - Selects EPR limit for takeoff in the EPR LIM readout. Automatically positions the reference bug on the EPR indicator.

 

TO FLX MODE SWITCH - Selects a reduced EPR limit for flexible takeoff thrust mode in EPR LIM readout and automatically positions the

                                                reference bug on the EPR indicator. Reduced EPR limit is determined by selecting an assumed temperature that is

                                                higher than ambient. ART switch must be OFF.

 

GA MODE SWITCH - Selects EPR limit for go-around mode in the EPR LIM readout. Automatically positions the reference bug on the EPR indicator.

 

MCT MODE SWITCH - Selects EPR limit for max continuous thrust mode in the EPR LIM readout. Automatically positions the reference bug 

                                           on the EPR indicator.

 

CL MODE SWITCH - Selects EPR limit for climb thrust in the EPR LIM readout. Automatically positions the reference bug on the EPR indicator.

 

CR MODE SWITCH - Selects EPR limit for cruise thrust in the EPR LIM readout. Automatically positions the reference bug on the EPR

                                        indicator.

 

NO MODE LIGHT - Indicates that an EPR mode has not been selected or an incorrect engine bleed combination has been selected.

 

 

LOCATION: Main Panel

 

ASSUMED TEMP SELECTOR - click on the upper or lower portion of the readout to set the assumed temperature for a flexible (TO FLX)

                                                         mode. Temperatures from 1 to 59 degrees can be selected.

 

 

THRUST RATING PANEL - GLASS

 

 

LOCATION: Main Panel

 

ASSUMED TEMP SELECTOR - Sets assumed temperature in FMA autothrottle window for takeoff flexible (TO FLX) mode. Temperature 

                                                         can be set from 1 to 59 degrees. The EPR display on EEDP is based on maximum thrust EPR at the assumed

                                                         temperature.

 

TO MODE SWITCH - Selects EPR limit for takeoff in the EPR LIM readout on the EEDP. Automatically positions the reference bug on the 

                                       EPR indicator.

 

TO FLX MODE SWITCH - Selects a reduced EPR limit for flexible takeoff thrust mode in EPR LIM readout on the EEDP and automatically

                                                positions the reference bug on the EPR indicator. Reduced EPR limit is determined by selecting an assumed

                                                temperature that is higher than ambient. ART switch must be OFF.

 

GA MODE SWITCH - Selects EPR limit for go-around mode in the EPR LIM readout on the EEDP. Automatically positions the reference bug

                                       on the EPR indicator.

 

MCT MODE SWITCH - Selects EPR limit for max continuous thrust mode in the EPR LIM readout on the EEDP. Automatically positions the

                                           reference bug on the EPR indicator.

 

CL MODE SWITCH - Selects EPR limit for climb thrust in the EPR LIM readout on the EEDP. Automatically positions the reference bug on 

                                       the EPR indicator.

 

CR MODE SWITCH - Selects EPR limit for cruise thrust in the EPR LIM readout on the EEDP. Automatically positions the reference bug on 

                                        the EPR indicator.

 

NO MODE LIGHT - Indicates that an EPR mode has not been selected or an incorrect engine bleed combination has been selected.

 

TEST SWITCH - Pushing switch displays 12 PLUS in RAT readout on the ESDP, and 2.04 in EPR LIM readout on the EEDP. All lights,

                              including the NO MODE light should be off. When switch is released, dashes appear in the EPR LIM readout, the NO MODE

                              light comes on, and all the mode switch lights are off. 

 

 

THROTTLES, REVERSERS, AND FUEL LEVERS

 

 

LOCATION: Throttle Quadrant

 

THRUST REVERSER LEVERS

 

Moving aft (F2) deploys the thrust reversers.

 

THROTTLES

 

Each throttle control is connected by cable to its respective engine fuel control unit to regulate engine thrust.

 

FUEL LEVERS

 

    ON - Completes ignition circuit, then turns on fuel.

 

    OFF - Shuts off fuel, then shuts off ignition.

 

 

LOCATION: Main Panel

 

ENG REVERSE THRUST - Comes on when thrust reversers are fully extended.

 

ENG REVERSE UNLOCK - Comes on when thrust reversers are unlatched.

 

 

LOCATION: Overhead Panel

 

ENG SYNC SELECTOR

 

    OFF - N1 and N2 synchronization is disabled. Left engine EPR is matched to right engine EPR if autothrottle is on.

 

    N1 - Left engine N1 is matched to right engine N1

 

    N2 - Left engine N2 is matched to right engine N2

 

 

AUTOMATIC RESERVE THRUST

 

 

ART INOP LIGHT - Indicates a failure of the automatic reserve thrust system or that the ART switch is off.

 

READY AND ART LIGHTS

 

    READY - Indicates that self-test of automatic reserve thrust system is satisfactory.

 

    ART - Indicates that automatic reserve thrust system has been activated.

 

ART SWITCH

 

    AUTO - Automatic reserve thrust system enabled. If engine failure occurs during takeoff, operating engine automatically provides thrust increase

                   to EPR limit.

 

 

ENGINE ANNUNCIATOR LIGHTS

 

 

FUEL HEAT ON - Indicates bleed air supply valve to fuel/air heat exchanger is open.

 

ENG SYNC ON - Indicates engine synchronization selector is in N1 or N2 position when landing gear is down.

 

ART INOP - Indicates a failure of the automatic reserve thrust system or that the ART switch is off.

 

L (R) START VALVE OPEN - Indicates engine start valve is open.

 

L (R) OIL STRAINER CLOGGING - Indicates excessive differential pressure across main engine oil filter.

 

L (R) OIL PRESSURE LOW - Indicates low oil pressure.

 

L (R) INLET FUEL PRESS LOW - Indicates fuel pressure is at engine is low.

 

L (R) FUEL FILTER PRESS DROP - Indicates differential pressure across the engine fuel filter.

 

 

SCHEMATICS