11 Engine Controls B737-NG.pdf

8/9/2019 11 Engine Controls B737-NG.pdf

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ENGINE - CONTROLS

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ENGINE CONTROLS - INTRODUCTION

Purpose

The engine control system supplies most of the signalsto control the engine thrust. It also supplies signals toother airplane systems that require engine controlstatus.

The engine control system has these components:

- Thrust lever assemblies- Engine start levers and switches- Thrust lever interlock solenoids.

Abbreviations and Acronyms

AGB - accessory gearbox AMM - aircraft maintenance manual ASM - autothrottle servomotorCDS/DEU - common display system/display

electronics unitEEC - electronic engine controlFDAU - flight data acquisition unitIDG - integrated drive generatorHPSOV - high pressure shutoff valveTO/GA - takeoff/go-aroundT/R - thrust reverser

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EFFECTIVITYENGINE CONTROLS - INTRODUCTION

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ENGINE CONTROLS - GENERAL DESCRIPTION

General

The engine control system supplies manual andautomatic control inputs to operate the engine. Theengine control system has these components:

- Thrust levers (forward and reverse)

- Engine start levers and switches- Thrust lever interlock solenoids.

Thrust Levers

You use the thrust levers to supply the manual inputsto the engine control system. There are two thrust leverassemblies, one for each engine. For each engine,

there is a forward thrust lever and a reverse thrustlever. The reverse thrust lever is on the forward thrustlever.

For each engine, the thrust levers supply a thrustcommand signal to the electronic engine control (EEC)through a resolver. Each thrust lever assemblyconnects mechanically to a resolver through anadjustable rod.

An interlock latch prevents the operation of the forwardthrust lever and the reverse thrust lever at the sametime.

EFFECTIVITY

Start Levers

There are two start levers, one for each engine. Youuse the engine start lever during an engine start. Youalso use it to shutdown the engine. The start leversoperate switches which supply signals to differentaircraft and engine systems and components.

Reverse Thrust Interlock Solenoids

There are two reverse thrust interlock solenoics, onefor each engine. Each reverse thrust interlock solenoidlimits the range of motion of a reverse thrust lever. Youcan make the thrust reverser deploy, but you can notincrease the reverse thrust until the thrust reverser

sleeves are near the full deployed position. The EECoperates the solenoids. The thrust lever interlocksolenoids are in the autothrottle assembly. You mustremove the autothrottle assembly to access the thrustlever interlock solenoids.

See the thrust reverser section for more information.(AMM PART I 78-31)

See the autoflight chapter for more information on theautothrottle system. (AMM PART I 22)

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ENGINE CONTROLS - COMPONENT LOCATIONS

Component Locations

The thrust levers and the start levers are on the controlstand in the flight compartment. You remove panelsfrom the aisle stand to get access to thesecomponents:

- Start lever switches- Interlock latch- Thrust lever cranks and rods.

The reverse thrust interlock solenoids are in theautothrottle assembly. The autothrottle assembly isunder the flight compartment floor, in the forwardequipment compartment. You go into the forward

equipment compartment through the access door,forward of the nose landing gear.

See the autothrottle section for more information on theautothrottle assembly (AMM PART I 22-31)

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ENGINE CONTROLS - INTERFACES

General

These equipment and mechanisms, related with theengine control system, are on the control stand andbelow the flight compartment floor:

- Resolvers

- Clutch pack- Switch packs- Autothrottle servomotor (ASM) and gearbox

assembly- Take off/go-around (TO/GA) switches and

autothrottle disengage switches.

Resolvers

There are two resolvers, one for each engine. Eachthrust lever assembly drives a resolver. The resolverchanges the thrust lever mechanical input into anelectric signal for the EEC.

See the engine fuel and control chapter for moreinformation on the resolver. (AMM PART I 73)

Clutch Pack

The clutch pack gives a friction connection betweenthese mechanisms:

- Thrust levers- ASM and gearbox assembly.

The clutch lets the autothrottle system move theresolver and the thrust levers. The clutch also gives afriction force to prevent the free movement of thethrust levers, but lets the pilot move them.

See the engine fuel and control chapter for more

information on the clutch pack. (AMM PART I 73)See the autoflight chapter for more information on theautothrottle system. (AMM PART I 22)

Switch Packs

There are two switch packs, one for each thrust lever

assembly. Each thrust lever assembly drives a switchpack through a mechanical linkage. Each switch packhas nine switches which supply the thrust lever positionto various systems.

These are the switches and the function of each switch:

- S1 - auto ground speedbrake control and landing gear

warning- S2 - autobrake system- S3 - autobrake system- S4 - engine thrust reverser synchronous shaft locks- S5 - engine thrust reverser control- S6 - engine thrust reverser control- S7 - wing thermal anti-ice system

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ENGINE CONTROLS - INTERFACES

- S8 - aural warning - takeoff warning and weatherradar

- S9 - landing gear warning.

Autothrottle Servomotor (ASM) and Gearbox Assembly

The automatic thrust management function of the

autothrottle system supplies the automatic thrustcommand signal to the EEC. To do this, the ASM andgearbox assembly drives the TLA resolvers and thethrust levers through the clutch pack.

See the autoflight chapter for more information on the ASM and gearbox assembly and on the autothrottlesystem. (AMM PART I 22)

Takeoff/Go-Around (TO/GA) and AutothrottleDisengage Switches

A TO/GA switch and an autothrottle disengage switchare in each thrust lever assembly. The TO/GA switchlets the pilot set the TO/GA automatic function. Theautothrottle disengage switch lets the pilot disengage

the autothrottle function. The command buttons forthese switches are just under and on the forward thrustlever knob.

See the autoflight chapter for more information on thego-around and autothrottle switches. (AMM PART I 22)

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ENGINE CONTROLS - START LEVER

General

You lift the start lever during an engine start sequence.You lower the start lever to shutdown the engine. Thestart lever sends signals to interfacing systems.

Start Lever

There are two start levers, one for each engine. Thestart lever has two positions, IDLE and CUTOFF. Adetent locks the lever in each position. You must pullthe lever out to move it from one detent to the other.The lever connects mechanically to a brake whichgives a friction force.

Each start lever operates 6 switches. Two of the switchessend signals to the EEC. Two of the switches interfacewith the engine ignition system. The other two switchessend signals to valves in the engine fuel feed system.

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ENGINE CONTROLS- START LEVER - FUNCTIONALDESCRIPTION

Functional Description

Each engine start lever operates six switches. Theseswitches are in the engine start lever switch module.The switches send signals to other systems.

These actions happen when you move the start lever tothe IDLE detent position, and the switches move to theidle position:

- The fuel control panel receives an input of startlever position for indication logic

- Electrical power opens the engine fuel shutoff valve- Ignition power (115v ac) goes to the EEC

- The two engine start lever relays move to the idleposition- The integrated drive generator (IDG) manual

disconnect circuit arms- The flight data acquisition unit (FDAU) sees the start

lever in the idle (engine run) position- The two CDS/DEUs see the start lever in the idle

(engine run) position.

These actions happen when you move the start lever tothe cutoff position and the switches move to the cutoffposition:

- The fuel control panel receives an input of startlever position

- Electrical power closes the engine fuel shutoff valve

- The ignition power circuits open- The two engine start lever relays move to the cutoff

position- Electrical power closes the high pressure shutoff

valve (HPSOV) in the hydromechanical unit (HMU)- EEC channels A and B reset.

See the engine fuel and control, engine control sectionfor more information on the HPSOV (AMM PART I 73-21)

See the engine ignition chapter for more information onthe ignition system (AMM PART I 74)

The EEC reset feature lets the EEC operate correctly

after a software error occurs in the EEC. See the enginefuel and control chapter for more functional descriptioninformation on the EEC.(AMM PART I 73)

See the engine fuel and control chapter for morefunctional description information on the EEC(AMMPART I 73)

See the fuel chapter for more information on the fuelsystem. (AMM PART I 28)

See common display system section for moreinformation on the CDS/DEU.(AMM PART I 31-62)

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See the flight controls chapter for more information onthe flight data acquisition unit (AMM PART I 27)

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ENGINE CONTROLS - REVERSE THRUSTINTERLOCK SOLENOIDS

General

The reverse thrust interlock solenoids energize topermit further movement of the reverse thrust leversduring a T/R deploy operation. If the reverse thrustinterlock solenoid does not energize, you can not movethe reverse thrust lever and increase reverse thrust.The solenoids energize when the T/R sleeves are 60%of travel to the full deploy position. Each EEC controlsone of the solenoids. See the thrust reverser controlsection for more information. (AMM PART I 78-34)

Reverse Thrust Interlock Solenoids

There are two reverse thrust interlock solenoids, onefor each thrust lever assembly. They are a rotarysolenoid type. Each reverse thrust interlock solenoiduses a rod to operate a latch. When you move areverse thrust lever to the DEPLOY position, a contouron the brake mechanism catches the latch. This stopsthe rotation of the brake mechanism and limits themotion of the reverse thrust lever and the reverse

thrust lever moves enough to operate switches tocommand the thrust reverser deployment. When theEEC energizes the reverse thrust interlock solenoid,the latch disengages. This permits the motion of thereverse thrust lever towards the full reverse thrustposition.

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Functional Description

Each solenoid connects to both channels of the EEC.The EEC receives the T/R translating sleeves positiondata from the LVDT of each sleeve. When both sleevesare at more than 60% of deploy, the EEC energizesthe solenoid. The solenoid retracts the interlock latch.The reverse thrust lever can now move past the deployposition so reverse thrust can increase.

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11 Engine Controls B737-NG.pdf

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