Ata Chapter 27 Flight Controls

ATA CHAPTER 27 FLIGHT CONTROLS

27-00 GENERAL

8

GENERAL ... 8

Primary Flight Controls... 9

Secondary Flight Controls... 9

Spoilers... 9

Stall Warning and Prevention... 9

Gust Lock ... 9

27-10 AILERON CONTROLS AND TRIM

10

Aileron Controls... 11

Aileron Trim... 11

INTERFACE TO OTHER SYSTEMS ... 11

Roll Spoiler System... 11

Indicating/Recording Systems... 11

Autoflight ... 11

AILERON CONTROLS

12

LH and RH Control Wheels ... 13

Control Cables... 13

Pulleys ... 14

LH and RH Cable Tension Regulators... 14

LH and RH Transition Units ... 15

Aileron Disconnect Unit... 15

Quadrant Assembly ... 16

Levers and Bellcranks ... 17

Control Rods... 17

Aileron Disconnect Microswitch 7CW ... 18

LH and RH Aileron Position Transmitters 5CX and 4CX... 18

OPERATION(refer to Fig. 3, Fig. 5, Fig. 7)... 18

Power Supplies... 18

Aileron Controls... 18

Flight Compartment Controls... 18

Flight Compartment to Upper Center Fuselage Control Run... 18

Regulation of Cable Tension in Fuselage Control Run... 18

Aileron Controls from Transition Units to Wing Roots... 19

RH Aileron Servo Tab ...20

LH Aileron Trim/Servo Tab ...20

SYSTEM INDICATIONS ...21

Aileron Position Indicating ...21

Aileron Disconnect Unit Monitoring ...21

AILERON TRIM

23

Aileron Trim Actuator 4CC (refer to Fig. 9) ...23

Trim Control Panel 10CC ...24

Main Aileron Trim Switch 2CC...24

Standby Aileron Trim Switch 12CC...25

Aileron Trim Reset Switch/Light 17CC ...25

Trim Test Switch 50CC ...25

OPERATION...25

Power Supplies...25

System Power-Up ...25

Aileron Trim ...28

SYSTEM INDICATIONS ...31

Standby Trim/Main Lockout Circuit Status...31

27-20 RUDDER CONTROLS AND TRIM

32

Rudder Controls ...32

Rudder Trim...33

INTERFACE TO OTHER SYSTEMS...33

Navigation System ...33

Communications ...33

Autoflight...33

RUDDER CONTROLS

34

LH and RH Rudder Pedal Assemblies...35

LH and RH Pedal Adjustment Assemblies...35

LH and RH Forward Quadrant Assemblies ...36

Pulleys...36

Control Rods ...36

Levers and Bellcranks...37

Pressure Bulkhead Fairleads ...37

Aft Quadrant Assembly ...37

Spring Tab Lever Assembly ...38

Rudder Limiter Actuator 7CL...38

TEST TAB LOCK Switch/Light 2CL ...39

RUD LIMIT Switch/Light 5CL ...40

Current Detector 16CX ...40

Rudder Position Transmitter 19CX...40

OPERATION...40

System Power-Up... 41

Rudder Controls ... 41

Electrical Control of Rudder Limiter ... 43

SYSTEM INDICATIONS ... 44

Rudder Position Indicating... 44

Rudder Limiter Monitoring... 45

RUDDER TRIM

48

Rudder Trim Switch 22CC... 48

Trim Test Switch 50CC... 49

Rudder Trim Actuator 25CC... 50

OPERATION ... 50

Power Supplies... 50

System Power-Up... 50

Rudder Trim (refer to Fig. 27)... 51

SYSTEM INDICATIONS ... 53

T rim Position Indicating... 54

Rudder Trim Selection Status... 54

27-30 ELEVATOR CONTROLS AND TRIM

55

Elevator Controls... 56

Elevator Trim ... 56

INTERFACE TO OTHER SYSTEMS ... 56

Indicating/Recording Systems... 56

Navigation System ... 56

Auto Flight System... 56

ELEVATOR CONTROLS

57

LH and RH Control Column ... 58

LH and RH Cable Tension Regulator ... 59

Control Cables... 59

Pulleys ... 59

Control Rods... 59

Levers and Bell cranks ... 59

Pressure Bulkhead Fairleads ... 59

Quadrant Assembly ... 60

Elevator Disconnect Unit ... 61

Elevator Disconnect Micro switch 8CW... 61

LH and RH Elevator Position Transmitters 25CX and 26CX... 62

OPERATION ... 62

Power Supplies... 62

Elevator Controls... 62

Flight Compartment to Vertical Stabilizer Control Run ... 62

LH and RH Elevator Tab... 63

Elevator Position Indicating...63

Elevator Disconnect Unit Monitoring...63

ELEVATOR TRIM

65

LH (RH) Elevator Trim Actuator 53CC (52CC) ...66

Main Elevator Trim Switches 33CC...67

Standby Elevator Trim Switch 63CC...68

Elevator Trim Reset Switch/Light 69CC...68

Trim Test Switch 50CC ...68

OPERATION...68

Power Supplies...68

System Power-Up ...68

Trim Control ...69

Main Trim Control...69

Standby Trim Control and Main Trim Lockout...69

Actuator Speed Control...72

Main Trim Runaway Override...73

Runaway Override Test ...73

Main Trim Circuit Fault Protection ...74

Standby Trim Circuit Fault Protection...74

Auto-Trim ...75

SYSTEM INDICATIONS ...75

Trim Position Indicating ...76

Trim Synchronization ...76

Trim Speed Mode Indicating ...77

Standby Trim/Main Lockout Circuit Status...79

Trim Actuator Status...79

27-33 STALL WARNING AND PREVENTION

80

Angle of Attack Information...81

Stall Warning Computing ...81

Stick Shaker ...81

Stick Pusher...81

System Inhibition on Ground and below 100 ft Radar altitude ...81

Stick Pusher Disarm...82

Autopilot Disengagement ...82

System Test...82

System Monitoring and Indicating...82

INTERFACE TO OTHER SYSTEMS...83

Auto Flight System (Chapter 22)...83

Communications (Chapter 23)...83

FUNCTIONAL DESCRIPTION ...83

LH (RH) AOA Sensor 2WH (12WH)...84

LH (RH) Stick Shaker 6WH ...85

Stick Pusher 25WH...85

LH (RH) Stall Warning Test Switch 7WH (17WH)...86

Pusher Disarm Switch/Light 22WH ...87

OPERATION ... 87

Power Supplies... 87

System Power-Up... 87

Power-Up Test... 89

System Test ... 89

Stall Warning Computing... 90

Stick Shaker Operation... 91

Stick Pusher Operation... 91

SYSTEM INDICATIONS ... 93

General ... 93

AOA Sensor Status... 93

AOA Comparison... 93

Shaker Status ... 94

Pusher Status ... 94

27-50 FLAPS

97

INTERFACE TO OTHER SYSTEMS ... 98

Hydraulic Power (Chapter 29) ... 98

Landing Gear (Chapter 32)... 98

Navigation (Chapter 34)... 98

Indicating/Recording Systems (Chapter 31) ... 98

FUNCTIONAL DESCRIPTION ... 98

Flap Control Unit 2CG... 99

Flap Control Switch 3CG... 101

Flap Control Valve Manifold 4CG... 102

LH and RH Flap Actuators... 103

LH (RH) Flap Position Feedback Sensor 5CG (6CG) ... 103

Torque Shaft... 104

Relay 8CG ... 104

OPERATION ... 104

Electrical Power Supplies... 104

Hydraulic Power Supplies... 104

System Power-Up... 106

Power-Up Test... 106

Flap Operation... 107

SYSTEM INDICATIONS ... 108

General ... 108

System Operating Status Monitoring ... 109

System Reset ... 109

Flap Position Indicating... 109

27-60 SPOILERS

111

Ground Spoilers (optional)... 112

Roll Spoilers... 112

Indications ... 112

INTERFACE TO OTHER SYSTEMS ... 112

GROUND SPOILERS (OPTIONAL)

113

FUNCTIONAL DESCRIPTION ...113

Valve Manifold 10CS ...113

Ground Spoiler Actuators ...115

Restrictor Relief Valves...116

Ground Spoiler Arm/Disarm Switch/Light 2CS...117

Microswitches 3CS/5CS/7CS/8CS ...117

Proximity Sensors 3CW/5CW (refer to Fig. 64)...118

OPERATION...118

Electrical Power Supplies ...118

Hydraulic Power Supplies...118

System Power-Up ...118

System Pre-Takeoff Test...118

Spoiler Inflight Inhibition ...119

Landing Gear Circuit ...119

Power Lever Circuit...119

Spoilers Disarm/Arm ...122

Auto-Deployment on Landing ...122

Auto-Deploy on Aborted Takeoff...122

Auto-Stow ...122

Spoiler Lockout During Ground Manoeuvring...122

SYSTEM INDICATIONS ...123

Ground Spoiler Position Indicating...123

Spoiler Proximity Sensor Monitoring...123

Ground Spoiler not Stowed...123

Ground Spoiler Control Circuit Armed ...123

ROLL SPOILERS

125

LH and RH Roll Spoiler Actuators...125

LH (RH) Roll Spoiler Position Sensor 21CX (22CX)...127

Double Shuttle Valve...127

OPERATION...128

Hydraulic Power Supplies...129

Roll Spoiler Control...129

SYSTEM INDICATIONS ...130

Spoiler Position Indicating...130

27-70 GUST LOCK AND DAMPER

132

Aileron and Elevator Control Gust Locks...132

Rudder Damper...133

FUNCTIONAL DESCRIPTION ...133

Gust Lock Lever, Flexible Cables and Distribution Box...133

Aileron Controls Gust Lock...134

Elevator Controls Gust Lock...134

INDEX

137

27-00 GENERAL

GENERAL

This chapter provides information on those units and components which furnish a means of manually controlling the flight attitude of the aircraft. The chapter is divided into sections containing detailed information on the following flight control subsystems:

- Aileron Controls and Trim - Rudder Controls and Trim - Elevator Controls and Trim - Stall Warning and Prevention - Flaps

- Spoilers

- Ground Spoilers (Option) - Roll Spoilers

- Gust Lock and Damper Primary Flight Controls

The aircraft primary controls consist of conventional ailerons, elevators and rudder. The primary control surfaces are moved manually by linkage systems consisting of cables, pulleys, levers and rods. Dual controls are installed for the three primary controls. The elevator and aileron control runs are each equipped with a disconnect unit. This allows the captain's and first officer's controls to be disconnected from each other should one control run become jammed. The rudder pedals drive a Flettner-type spring tab on the trailing edge of the rudder. At airspeeds up to 160 knots the rudder is deflected by aerodynamic servo reaction from the tab. The rudder itself is not connected to the rudder pedals directly except at airspeeds above 160 knots.

Secondary Flight Controls

The secondary flight controls consist of aileron, elevator and rudder trim systems and trailing edge flaps. The aircraft is trimmed in the three axes by electro-mechanical actuators driving trim tabs. Roll trim is achieved by a single actuator driving a tab on the left aileron. Pitch trim is achieved by a tab on each elevator, each tab having its own actuator. Yaw trim is achieved by a single actuator driving a tab on the trailing edge of the rudder. The flaps consist of one flap section on the trailing edge of each wing half. The two sections are mechanically linked and are driven hydraulically.

Spoilers

For improved performance roll spoilers and ground spoilers are installed. The roll spoilers assist the ailerons. Both sets of spoilers are located on the top surface of the wing and are driven hydraulically. Stall Warning and Prevention

A stall warning and prevention system (stick shaker and stick pusher) is installed. Gust Lock

The ailerons and elevators can be locked for parking by a lever in the flight compartment. The rudder control system is equipped with a hydraulic gust damper which prevents damage to the structure when the aircraft is parked in gusty conditions

27-10 AILERON CONTROLS AND TRIM

General

RH Aileron Position Transmitter

Aileron Disconnect Unit

LH Aileron Position Transmitter

Control Wheels

Cable Tension Regulators

EICAS position status position 30° 25° 30° 25° Servo Tab Trim/Servo Tab

Fig. 2 Aileron - General Arrangement

This section provides information on that portion of the flight control system which controls the ailerons and the aileron trim tab. Also included are the aileron and trim tab position indicating systems and the aileron disconnect indicating system.

The section is divided into subsections containing detailed information on the following aileron and tab subsystems:

- Aileron Controls - Aileron Trim

Aileron Controls

The aircraft is controlled about the roll axis by a conventional aileron control system. Two ailerons are installed, one on the outboard trailing edge of each wing. The ailerons are manually operated by dual control wheels. The linkage from the control wheels to the ailerons is by an arrangement of pulleys, cables, quadrants, push-pull rods, levers and bellcranks. The maximum aileron movement is 30° up and 25° down. The captain's and first officer's aileron control runs are joined by a disconnect unit. This unit allows the two control runs to be separated by the application of higher than normal input forces should one control run become jammed.

Aileron Trim

The aircraft can be trimmed about the roll axis by a Trim/Servo-tab located on the inboard trailing edge of the left aileron. The tab is driven by an electrically powered linear actuator installed in the trailing edge of the wing. Due to the actuator attachment geometry the tab also functions as a servo tab to provide aerodynamic assistance to flight crew roll commands.

The actuator is powered by two separate DC motors and controlled by either a main or a standby aileron trim switch. Override circuits are provided to protect against a trim runaway. Test facilities are provided for the override circuits.

INTERFACE TO OTHER SYSTEMS

Roll Spoiler System

The roll spoiler control actuators are connected by push-pull rods to the aileron control system. Indicating/Recording Systems

The following functions of the aileron and tab subsystem are indicated on the electronic indicating, caution and advisory system EICAS:

- the position of each aileron

- the status of the aileron disconnect unit - the position of the aileron trim actuator. Autoflight

Signals from the automatic flight control system (AFCS) are used to operate the ailerons when the aircraft is flying under automatic control. Refer to (Chapter 22 - AUTO FLIGHT) for further details.

AILERON CONTROLS

FUNCTIONAL DESCRIPTION

The aileron control subsystem consists of the following components:

FIN Component Panel Zone Access Door

LH and RH control wheels 210 211-FZF

212-EZF LH and RH cable tension regulators 120 211-LFZ 212-KFZ

LH and RH fairlead brackets 120 221-MFZ

222-EFZ control cables 120 130 210 various + furnishing pulleys 220 panels control rods 220 530 630 various

levers and bellcranks 530

630

various

LH and RH transition units 220 251-bt

252-bt furnishing

panels

aileron disconnect unit 250 251-bt

quadrant assembly 252-bt

7CW aileron disconnect microswitch

4CX RH aileron position transmitter 632 632-JB

LH and RH Control Wheels

A

Pulley Cable Tension Regulator

Control Cable

Fig. 3 Aileron - Control Wheels to Transition Units

The control wheels are of the horn type and are mounted with splined shafts on the top of the control columns. Wheel movement is transmitted to the aileron control cable tension regulators beneath the flight compartment floor by cables and pulleys.

Control Cables

The aileron control cables transmit the movement of the control wheels to the tension regulators and from there to the transition units located on the passenger compartment roof between frames 25 and 26. The cables are 7 x 19 flexible steel wire ropes made from corrosion resistant steel and have a nominal diameter of 3.2 mm (0.13 in.).

The LH and RH aileron control runs each consist of eight separate cable sections. Each control wheel is connected to its associated tension regulator by four sections. Each tension regulator is connected to its associated transition unit by a further four sections. Cable sections are joined by turnbuckles and terminated by swaged end fittings.

Pulleys

The control cables are guided by pulleys equipped with cable guards. The pulleys are made of a phenolic material and run in sealed ball bearings.

A double pulley connected to the control wheel at the top of each control column and two single pulleys at the base of the control column guide the cable run from the control wheel to the associated tension regulator. The cable run from each tension regulator to the associated transition unit is guided by a total of fifteen pulleys.

LH and RH Cable Tension Regulators

Notch for Aileron Gust Lock (LH Side Only)

Input Pulley

Lower Arm Compression Springs

Sliding Lever Assembly Compression Springs

Upper Arm

Fig. 4 Aileron - Cable Tension Regulator

The tension of the control cables installed in the flight control system must be maintained within specified tolerances. Temperature effects cause the cables and the aircraft structure to expand and contract. The expansion coefficient of the aluminium structure is higher than that of the steel cables. This means that the cables tighten at high ambient temperatures and slacken at low ambient temperatures. Control cable tension regulators compensate for these effects.

A control cable tension regulator is installed below the flight compartment floor in the captain's and first officer's aileron control runs. The two tension regulators are identical in operation. Each regulator automatically regulates the tension of the control cables between the regulator output quadrant and the associated cable termination quadrants in the upper center fuselage. The tension regulator consists of a shaft to which an input pulley and a spring compensator mechanism are firmly attached. An output quadrant with separate upper and lower sections is installed on but not attached to the shaft. The two sections are connected to each other by the compensator mechanism but are otherwise free to rotate on the shaft. The compensator mechanism consists of two compression springs which act on a sliding lever assembly. The sliding lever is connected to the upper and lower sections of the output quadrant by two arms. If the control cables become tight the cables pull the two sections of the output quadrant towards the shaft against the force of the springs. This effectively shortens the length of the cable run. If the cables become slack the springs push the quadrant sections in the other direction to take up the slack.

LH and RH Transition Units

The transition units are installed in the roof section of the passenger compartment between frames 25 and 26. The units have two functions:

- they act as a connection point between the LH (RH) cable run in the fuselage and the rods in the LH (RH) wing

- they act as pressure seals at the point where the control run exits the pressure compartment.

Each unit consists of a cable quadrant located in the pressure compartment and an output lever located in the fairing between the fuselage and the wing. The quadrant and the lever are mounted on a common shaft . The shaft bearing is installed in the passenger compartment roof and acts as the pressure seal. The quadrant accepts the control inputs from the fuselage control cables and the lever transmits the movement into the control rod run in the wing.

Aileron Disconnect Unit

A

A

Rod to RH Aileron Control

LH/RH Interconnect Rod

Autopilot Roll Servo Actuator

Cable Quadrant

Lever Assembly

Rod to LH Aileron

Lever Assy Drive Rod Quadrant Output Lever

Roll Disconnect Unit

Quadrant Assembly

Output to RH Aileron

Transverse Rod to LH Control Circuit

Rear Half

Command Input from RH Control Circuit Front Half

Fig. 6 Aileron - Disconnect Unit

The captain's and first officer's aileron control cable runs are routed completely separately along the left and right sides of the fuselage respectively. They are joined by an interconnect rod in the wing center section and an aileron disconnect unit located in the trailing edge section of the RH wing root. Under normal circumstances the movement of one control wheel moves both ailerons and the other control wheel. Should one aileron control become jammed the two control circuits can be separated by the application of a higher than normal force to a control wheel.

The unit has two halves which are held engaged by a spring and cam arrangement. The front half has levers for two push-pull rods. The lower lever is for the command input from the RH aileron control circuit. The upper lever is for the output rod to the RH aileron. The rear half has a single lever for the interconnect rod that joins the LH and RH control circuits. Under normal operating conditions the two halves of the unit are firmly engaged and move together as a single unit. Should one of the aileron control circuits jam, the two halves can be disconnected from each other by the application of a higher than normal force at a control wheel. The disconnect force is 39 daN (87.7 lb). The applied force causes the cam to override the spring force and move out of its detent. The two halves of the unit are now disengaged, effectively isolating the jammed control circuit. In this situation the captain's control circuit is connected to the left aileron only. The first officer's control circuit is connected to the right aileron only. The aircraft can be controlled about the roll axis using the free control wheel. Once activated, the disconnect unit can only be reset on the ground.

The unit has an integral microswitch 7CW which is operated if the disconnect unit is activated. The switch sends a signal to EICAS

Quadrant Assembly

The quadrant assembly is installed in the trailing edge section of the LH wing root at rib 2. The assembly consists of three levers and a cable quadrant all mounted on a common shaft. The lower lever accepts the control inputs from the LH transition unit. The forward upper lever is the drive lever for the LH aileron control run. The aft upper lever forms the connection point for the LH/RH aileron control interconnect rod. The cable quadrant is the connection point for the autopilot roll servo to the aileron control run. The control cable from the autopilot roll servo is connected to cable arms that extend from the upper and lower sections of the cable quadrant. Because the control cable has no turnbuckles, the arms can be adjusted with screws for setting the cable tension.

Levers and Bellcranks R 3 R 4 R 5 R 6 R 7 R 8 R 9 R 10 R 11 R 12 R 12 R 13 R 14 R 15 R 16 R 17 R 18 R 19 R 20 R 0 A 1 7 2 3 4 5 LH SIDE SHOWN, RH SIDE SIMILAR.

6

A

Fig. 7 Aileron - Wing Root to Aileron

The control rods in the wing are supported by idler levers and bellcranks running in sealed ball bearings. The connection points for the rod clevis ends are formed by self-aligning sealed ball bearings.

Control Rods

The aileron control run from the transition units in the upper center fuselage to their associated aileron is formed by a series of aluminium push-pull control rods. Another rod forms the interconnection between the LH (captain's) and RH (first officer's) aileron controls. The Servo-tab on each aileron is also controlled by rods. Rod ends are either of the clevis or eye type. Eye type rod ends are equipped with self-aligning sealed ball bearings.

1. Interconnection Rod 2. Quadrant Assembly 3. Position Transducer 4. Aileron Drive Rod 5. Bellcrank

6. Rollspoiler Drive Rod 7. Disconnect Unit

Aileron Disconnect Microswitch 7CW

A microswitch located in the aileron disconnect unit monitors the status of the unit and sends a discrete signal to the EICAS when the disconnect unit is activated. The switch contacts are connected to ground under normal operating conditions and open under aileron disconnect conditions.

LH and RH Aileron Position Transmitters 5CX and 4CX

An aileron position transmitter is installed for each aileron. The transmitters are installed on their associated wing rear spar between ribs 17 and 18. Each transmitter is driven by a short rod connected to the outboard idler lever in the aileron control run. The transmitters are identical 0 to 10 kΩ three-wire potentiometers whose resistance changes as a function of the aileron position. They send a variable resistance signal to the EICAS for aileron position indicating.

OPERATION

Power Supplies

Electrical power is not required for the aileron control system. Power for the indicating part of the system is provided by the EICAS

Aileron Controls

Note:

The LH (captain's) and RH (first officer's) aileron controls from the flight compartment to the upper center fuselage are similar. The operation of the LH side is described. Differences for the RH side are covered in the text or given in brackets.

Flight Compartment Controls

The Control wheel movement is transmitted through the pulleys by a cable to the cable tension regulator located at frame 9. The tension of this short cable run can be adjusted by turnbuckles. A notch is provided in the aft portion of the LH cable tension regulator between the upper and lower quadrants. The aileron gust lock engages with this notch to lock the aileron controls for gust protection when the aircraft is parked.

Flight Compartment to Upper Center Fuselage Control Run

From the cable tension regulator, the control movement is continued aft below the flight and passenger compartment floor by control cables and pulleys. The cables pass through guides in some frames under the floor. Cable fairleads equipped with small pulleys are used to guide the cables through the machined part of frame 24. The cable run is virtually straight as far as a point between frames 25 and 26. At this point the cables are routed outboard and then upwards. The cable run now passes between the fuselage skin and the passenger compartment furnishing panels and terminates at a transition unit on the passenger compartment roof just left (right) of the aircraft centerline.

Regulation of Cable Tension in Fuselage Control Run

The continuous cable run from the cable tension regulators to the cable quadrants on the passenger compartment roof is approximately 9.5 m (31 ft) long. Approximately 6.5 m (21 ft) of this is a virtually straight horizontal run. The expansion coefficient of the aluminium structure is higher than that of the steel cables. This means that the cables tighten at high ambient temperatures and slacken at low ambient temperatures. The control cable tension regulators compensate for these effects.

The shaft of the tension regulator (and thus the regulator mechanism) is rotated by flight crew commands acting on the input pulley. The movement is transmitted to the upper and lower sections of the output quadrant by the arms of the regulator mechanism. The control cable is a two-part cable, each part being attached to its associated quadrant section by a nipple. The two sections of the output quadrant are thus allowed to move in relation to each other.

Under high ambient temperature conditions the control cables tighten. The cable tension pulls on the two sections of the output quadrant and moves them in opposite directions on the shaft. The movement acts through the arms and pulls the sliding lever assembly towards the shaft against the force of two compression springs. This effectively shortens the length of the cable run. The sliding motion continues until the spring compression is equal to the cable tension.

If the ambient temperature is low the cables slacken. The springs push the two sections of the output quadrant in the other direction to take up the slack.

Aileron Controls from Transition Units to Wing Roots

The shaft of the transition unit on the LH side of the passenger compartment roof exits the fuselage through a pressure tight fitting. A lever is fixed to the shaft out-side the fuselage. A push-pull rod connected to the lever transmits the aileron commands to the quadrant assembly at LH wing station Y 600 (rib 2). A cable quadrant shares a common shaft with three levers on the quadrant assembly. The autopilot roll servo is connected by a control cable to the aileron control run at this quadrant.

Two push-pull rods are connected to the upper levers of the quadrant assembly. The aft rod connects to the aileron disconnect unit (at RH wing station Y 600 (rib 2). This rod forms the interconnection between the LH (captain's) and RH (first officer's) aileron controls. The forward rod is the first of six push-pull rods which form the control run from the wing root to the aileron drive bellcrank at LH wing station Y 7345.4 (between ribs 19 and 20).

The RH side is similar to the LH. The differences are: - the disconnect unit replaces the quadrant assembly - the control run starts with rod from the disconnect unit

- the interface to the autopilot is connected through the disconnect unit. Aileron Controls from Wing Root to Aileron

Six push-pull rods - supported at intervals by idler levers and a bellcrank - form the control run from the quadrant assembly in the LH wing root to the LH aileron drive bellcrank. The six rods are routed along the aft face of the rear spar. A further push-pull rod is connected to the idler lever located on the rear spar between ribs 15 and 16. This is the drive rod for the LH roll spoiler actuator. A short push-pull rod connects the aileron drive bellcrank to the aileron control horn. The horn is attached to the underside of the aileron.

The aileron position transmitter is driven by the outboard idler lever and indicates the aileron position on the flight control system page on EICAS.

The control run in the RH wing starts with rod at the disconnect unit. Otherwise it is similar to the LH wing control run.

RH Aileron Servo Tab

A B

B Servo Tab Push-Pull Rods

Servo Tab Push-Pull Rods

Connection to Wing Trailing Edge

Reduction Lever in Aileron Leading Edge

Connection to Servo Tab

Fig. 8 Aileron - Servo Tab

A Flettner-type servo tab is installed on the inboard trailing edge of the RH aileron. The tab is connected by four short push-pull rods and a reduction lever to the structure of the wing trailing edge at approximately station Y 6880 (just outboard of rib 18). The reduction lever is installed in the leading edge of the aileron. The tab moves in the opposite direction to the aileron to provide aerodynamic assistance for reduced pilot effort.

LH Aileron Trim/Servo Tab

A

Connection to Trim Tab

Aileron Trim Actuator

Connection to Wing Trailing Edge

Trim Tab Drive Rods Reduction Lever in Aileron

Leading Edge

An aileron trim tab is installed on the inboard trailing edge of the LH aileron. The dual-shaft trim actuator is installed in the trailing edge of the wing. The actuator drives the tab through a reduction lever installed in the leading edge of the aileron. The reduction lever is connected to the trim tab by twin push-pull rods. Due to this attachment geometry the trim tab also functions as a Flettner-type servo tab in addition to its function as a trim tab.

SYSTEM INDICATIONS

Certain components of the aileron control system send signals to EICAS. The signals are sent to data acquisition units (DAU’s) and are used:

- to display the position of the ailerons by synoptics

- to indicate the status of the aileron disconnect unit by a synoptic - to display a caution message if the aileron disconnect unit is activated.

The position of the ailerons and the status of the disconnect unit are displayed on the FLIGHT CONTROL page. The caution message is displayed on the CAS field of the primary EICAS page and on the FLIGHT CONTROL page.

Aileron Position Indicating

An aileron position transmitter is installed for each aileron. Each transmitter is a three-wire potentiometer whose resistance changes as a function of the aileron position. The LH transmitter sends resistance signal to DAU 1 in the EICAS system for processing. The RH transmitter sends an identical signal DAU 2. The resistance values correspond to the following aileron deflections:

- 0.5 kΩcorresponds to an aileron up deflection of -30° - 5 kΩcorresponds to aileron neutral

- 9.5 kΩcorresponds to an aileron down deflection of +25°.

The position of each aileron is indicated by a blue synoptic on the FLIGHT CONTROL page of the EICAS. If the transmitter signal is invalid, the blue synoptic is replaced by an amber X. Under normal operating conditions the LH and RH aileron synoptics are joined by a white bar. The bar changes to amber if the aileron disconnect unit is activated below.

Aileron Disconnect Unit Monitoring

A micro switch 7CW in the aileron disconnect unit monitors the status of the unit. It sends a discrete ground or open signal to DAU 1 for processing. The signal line is connected to ground under normal operating conditions and open circuit if the disconnect unit is activated. If the captain's and first officer's aileron control runs are disconnected:

- an amber AIL DISCONNECT caution message is displayed on the CAS field of the primary EICAS page and on the FLIGHT CONTROL page

- on the FLIGHT CONTROL page the white bar which connects the LH and RH aileron synoptics changes to amber.

CAS FIELD Indication MFD PAGE Indication Fault or Condition

AMBER

AIL DISCONNECT

AMBER

AIL DISCONNECT

AMBER Bar

Aileron disconnect unit activated

- blue

LH (RH) aileron synoptic Invalid synoptic replaced by an amber X RH aileron similar

Indicates position of Aileron

white pointer against white aileron scale

white pointer against white aileron scale

RUDDER LIMITED

TRIM SPEED FAST

FLAP ASYM

ELEV DISCONNECT

Honeywell

SYSTEM 1 / 3

HYDR ENGINE FUEL NEXT FLIGHT CONTROL ROLL ROLL 0 ° 0 ° NU ND AIL RUD E L E V TRIM RUDDER AILERON ELEVATOR LH RH FLAPS 12 20 AIL DISCONNECT 32

AILERON TRIM

FUNCTIONAL DESCRIPTION

The aileron trim subsystem consists of the following components:

FIN Component Panel Zone Access Door

1CC/11CC circuit breaker 12VE 210

1CX circuit breaker 18VE 210

2CC main aileron trim switch 10CC 210

4CC aileron trim actuator 532 532-JB

5CC trim runaway interlock relay LH 23VE 210 6CC trim runaway override relay LH 23VE 210 7CC trim runaway override relay RH 23VE 210 8CC trim runaway interlock relay RH 23VE 210

9CC aileron trim test relay 23VE 210

10CC trim control panel 210

12CC standby aileron trim switch 10CC 210

14CC 15CC

diodes 10CC 210

16CC standby aileron trim control relay 23VE 210 17CC aileron trim reset switch/light 10CC 210

50CC trim test switch 30VE LH 210

Aileron Trim Actuator 4CC (refer to Fig. 9)

The aileron trim actuator is installed in the left wing trailing edge at approximately station Y 6880 (just outboard of rib 18). The actuator has two separate DC motors (main and standby). The main motor is controlled by the main trim switch 2CC and the standby motor by the standby trim switch 12CC. Only one motor can operate at a time. An external electrical lockout circuit prevents the main motor from operating when the standby motor is active. Internal limit switches for both motors stop actuator movement before the mechanical limits are reached.

The rotary output of each motor is converted in a reduction gearbox to a dual shaft linear output. Total shaft travel between the electrical limits is 26.8 mm (1.05 in.). The twin shafts of the actuator are connected to a reduction lever arrangement in the leading edge of the aileron. Two push-pull rods connected to the output side of the reduction lever transmit the actuator movement to the tab.

An integral synchro-type position transmitter in the actuator sends an aileron trim position indicating signal to the EICAS.

Trim Control Panel 10CC RESET ELEV S T B Y T R I M UP RH RUD LH AIL STBY OFF PRESS TO RESET STBY ELEV UP RH LH AIL RH LH AIL DN NH OVSP ENG LH LH FI TEST OFF 1 TEST PLA FI PLA FI ENG RH SSEC DISABLE MADC 2 TRIM TEST

Fig. 11 Aileron Trim Controls - Trim Control

The trim control panel is installed in the aft LH section of the center pedestal. The panel interfaces with the aileron, rudder and elevator trim circuits and has the following switches:

- main aileron trim switch 2CC - standby aileron trim switch 12CC - aileron trim reset switch/light 17CC - rudder trim switch

- rudder trim on/off switch/light - elevator trim reset switch/light - standby elevator trim switch Main Aileron Trim Switch 2CC

The main aileron trim switch is installed in the forward LH section of the trim control panel. The switch is labelled LH AIL RH and contains two three-position center biased rocker switches. Both rocker switches must be activated together to operate the aileron trim actuator. The two switches have a total of eight sets of contacts (four per switch). Each contact of one rocker switch is connected in either series or parallel with a contact in the other switch, making a total of four contact pairs.

Standby Aileron Trim Switch 12CC

The standby aileron trim switch is installed in the forward RH section of the trim control panel. The switch is labelled LH AIL RH and is identical to the main trim switch 2CC. It controls the standby motor of the aileron trim actuator. A lockout circuit is activated when the standby trim switch is operated. This circuit disables the main motor of the aileron trim actuator. The main motor remains disabled until the reset switch/light 17CC is pressed.

Aileron Trim Reset Switch/Light 17CC

A lockout circuit disables the main trim motor when the standby trim motor is operated. The lockout circuit remains active even after the trim operation has been completed. The main trim motor can be re-enabled by pressing an aileron trim reset switch/light. The switch is labelled PRESS TO RESET and is installed in the trim control panel between the two aileron trim switches . A white STBY AIL annunciator in the front face of the switch comes on to indicate when the standby trim circuit - and thus the lockout circuit - is active. The switch is guarded by a transparent spring-loaded cover.

Trim Test Switch 50CC

The trim test push switch is installed in the LH engine/propeller test panel 30VE located in the forward LH section of the center pedestal. The switch is labelled TRIM TEST and is used to test the trim runaway override circuits of the following systems:

- aileron trim actuator main motor - rudder trim system

- elevator trim system

To test the aileron trim runaway override circuit, press and hold the TRIM TEST switch and then press the main aileron trim switch to LH and then RH. If the runaway override circuits of the actuator main motor are serviceable, the actuator will operate in the reverse direction to that commanded. When the test switch is released the motor will start again in the commanded direction.

OPERATION

Power Supplies

The aileron trim subsystem is supplied with 28 VDC and 26 VAC electrical power as follows:

Component BUS circuit breaker No.

trim actuator main motor control and power circuit

ESSENTIAL BUS 3PP AIL TRIM 1CC trim actuator standby control and power

circuit

BUS 1 2PP STBY AIL TRIM 11CC trim actuator position indicating circuit AC BUS 4XP AIL TRIM IND 1CX System Power-Up

The trim tab control and indicating circuits are energized when 28 VDC and 26 VAC are applied to the aircraft bus system.

10 11 12 4 5 6 7 8 9 1 2 3 2 10 C O T 3 C O T 5 C O T 1 4 6 C O T 9 C O T 8 11 AIL TRIM RH B8 B6 A8 A6 2CC AIL TRIM LH B2 B4 A2 A4 2CC 4CC B FILTER M R LH RH NORMAL OPERATION Br AIL TRIM ACTR AIL TRIM LH 2CC A1 A3 B1 B3 ESS BUS-3PP 3A 1CC AIL TRIM A5 A7 2CC AIL TRIM RH B5 B7 A2 A1 A3 8CC A2 A1 A3 9CC B2 B1 B3 C2 C1 C3 8CC 5CC X1 X2 6CC X1 X2 A1 7CC A3 A2 A3 6CC A1 A2 A1 A2 A3 B1 B2 B3 A2 A1 A3 7CC X1 X2 B2 B1 B3 8CC X1 X2 (9) (11) (5) (4) 5CC B2 B1 B3 C2 C1 C3 9CC 5CC (3) 16CC (18) 7 9CC X1 X2 A1 A2 A3 TRIMM TEST 50CC G3 G2 50CC G1 C = closes O = opens T = change over(transition) 5 7 4 8 6 3 1 2 A 5 7 4 8 6 3 1 2 B

Electrical Schematic for: Main Trim Switch 2CC and Stby Trim Switch 12CC

13 14 15 16 17 18 19 20 5 6 C O T 14 15 18 AIL TRIM STBY RH B8 B6 A8 A6 12CC 4CC B FILTER M R LH RH STBY OPERATION 16CC X1 X2 E 16CC E1 E2 E3 17CC A2 A3 A1 RESET 2LF STBY AIL 2CX 6CX 3CX LAMP TEST D/N A5 A7 12CC AIL TRIM STBY RH B5 B7 16CC D1 D3 D2 C1 C3 C2 B2 B4 A2 A4 AIL TRIM STBY LH 12CC AIL TRIM STBY LH 12CC A1 A3 B1 B3 BUS 1-2PP 3A 11CC STBY AIL TRIM

21 22 23 24 25 26VAC-BUS-6XP 1A 1CX AIL TRIM IND 4CC R1 R2

ACTR POSIT SENSOR S3 BK/W S1 S2 L W H SIGN 41 1TU H L SIGN 34 DAU 1

AIL POSIT POTI LH CW CCW W 5CX R H W L SIGN 609 11TU DAU 2

AIL POSIT POTI RH CW CCW W 4CX 26 27

Fig. 14 Aileron Trim - Electrical Diagram (Sheet 3 of 3)

Aileron Trim Main Trim Circuit

The main motor of the aileron trim actuator is controlled by the main aileron trim switch 2CC. If both rockers of the switch are held to LH (left wing down), the following contacts operate:

- series contacts A1/A3 and B1/B3 close and supply 28 VDC to the left wing down circuit

- parallel contacts A2/A4 and B2/B4 open and remove the ground from the right wing down circuit.

- contacts A3/A2 of relay 7CC - contacts A2/A3 of relay 16CC

- the contacts of the actuator LH internal limit switch. The ground circuit for the motor is provided by either:

- the contacts of the actuator RH internal limit switch (and then direct to ground if the actuator is at its maximum RH travel)or by the following series circuit:

- the contacts of the RH internal limit switch - contacts B3/B2 of relay 16CC

- contacts A2/A3 of relay 6CC - contacts B2/B3 of relay 9CC

- the parallel contacts B8/B6 and A8/A6 of the main trim switch 2CC.

The motor runs in the commanded direction (drives the trim tab down) until either the trim switch is released or until the LH internal limit switch operates. The operation sequence is similar in reverse when right wing down is commanded.

Main Trim Runaway Override Circuits

An electrical fault in the actuator control circuitry, such as sticking contacts in the main trim switch, could cause a trim runaway. Override circuits ensure that a main trim motor runaway can be stopped and reversed by instinctive operation of the main trim switch in the opposite direction to the runaway.

The following example describes the operation of the circuit in the event of a runaway towards left wing down.

Relay 5CC is the LH trim runaway interlock relay. It is energized when the main trim switch is held to the LH position. If contacts A1/A3 and B1/B3 of the main trim switch 2CC stick closed when the switch is released, the trim actuator will run uncommanded towards left wing down and relay 5CC will remain energized. The relay has three sets of contacts:

- contacts C2/C1 close and arm the test circuit

- contacts B2/B3 open and disable the coil circuit of relay 8CC (8CC is the RH trim runaway interlock relay)

- contacts A2/A1 close and arm the coil circuit of the trim runaway override relay 7CC.

The trim runaway will be indicated to the flight crew by the continuing left roll and by the aileron trim position indicator on the EICAS. The runaway can be stopped and reversed by holding the main trim switch to the RH position. This action energizes relay 7CC through contacts A2/A1 of 5CC. The contacts of 7CC replace the 28 VDC power supply to the left wing down side of the main trim motor with a ground connection. 28 VDC is now supplied to the right wing down side of the motor through:

- contacts A5/A7 and B5/B7 of the main trim switch 2CC - contacts A3/A2 of relay 6CC

- contacts B2/B3 of relay 16CC

- the contacts of the actuator RH internal limit switch. The ground circuit for the motor is provided by either:

- the contacts of the actuator LH internal limit switch (and then direct to ground if the actuator is at its maximum LH travel) or by the following series circuit:

- the contacts of the LH internal limit switch - contacts A3/A2 of relay 16CC

- contacts A2/A1 of relay 7CC.

The motor drives the trim tab up (right wing down) until either the trim switch is released or until the RH internal limit switch operates. If the fault still exists on the main trim switch when the switch is released, the actuator will again run uncommanded towards left wing down. The main motor can be disabled by momentarily operating the standby trim switch 12CC to LH or RH .

Runaway Override Test Circuit

The TRIM TEST push switch 50CC is used to test the trim runaway override circuits of the following systems:

- aileron trim actuator main motor - rudder trim system

- elevator trim system

To test the aileron trim runaway override circuit, press and hold the TRIM TEST switch and then press the main aileron trim switch 2CC to LH and then RH. If the runaway override circuits of the actuator main motor are serviceable, the actuator will operate in the reverse direction to that commanded. When the test switch is released the motor will start again in the commanded direction. The following example describes the operation of the circuit when the test switch is pressed and the main aileron trim switch held to LH.

When the TRIM TEST switch is held pressed the trim test relay 9CC energizes. Relay 9CC has two sets of contacts, one for the LH circuit and one for the RH. If the main trim switch is now held to the L position, relay 5CC energizes. The RH trim runaway override relay 7CC energizes through the following series circuit:

- contacts C2/C1 of relay 5CC - contacts B1/B2 of relay 9CC - contacts A2/A1 of relay 5CC.

The contacts of 7CC remove the 28 VDC power supply from the left wing down side of the main trim motor and replace it with a ground connection. The actuator stops. 28 VDC is now supplied to the right wing down side of the motor through:

- the same circuit as the coil of relay 7CC (see above) - contacts A3/A2 of relay 6CC

- contacts B2/B3 of relay 16CC

- the contacts of the actuator RH internal limit switch. The ground circuit for the motor is provided by either:

- the contacts of the actuator LH internal limit switch (and then direct to ground if the actuator is at its maximum LH travel)or by the following series circuit:

- the contacts of the LH internal limit switch - contacts A3/A2 of relay 16CC

- contacts A2/A1 of relay 7CC.

The motor now starts in the reverse direction and trims the aileron tab up (right wing down) until either:

- the TRIM TEST switch 50CC is released or

- the main aileron trim switch 2CC is released or

- the RH internal limit switch operates.

The test sequence is similar in reverse when the main trim switch is held to RH. Main Trim Motor Lockout Circuit

If for any reason the aileron main trim circuit is unserviceable, it can be disabled. This is done by momentarily pressing the standby trim switch 12CC to either LH or RH. The standby aileron trim control relay 16CC energizes and self-latches through its contacts E2/E1. The ground circuit for the relay coil is provided through the RESET switch/light 17CC.

In addition to the contacts for the self-latching circuit, relay 16CC has four other sets of contacts. Contacts C and D complete the circuits to the left and right wing down sides of the standby trim motor. Contacts A and B disable the left and right wing down sides of the main trim motor . The main motor is thus locked out until relay 16CC is de-energized by pressing the RESET switch/light. This re-enables the main motor and disables the standby motor.

A white STBY AIL annunciator in the aileron trim reset switch/light indicates when the standby aileron trim subsystem is active. The annunciator is controlled by contacts E2/E1 of relay 16CC .

Standby Trim Circuit

The standby motor of the aileron trim actuator is controlled by the standby aileron trim switch 12CC. If both rockers of the switch are held to LH (left wing down), the following contacts operate:

- series contacts A1/A3 and B1/B3 close and supply 28 VDC to the left wing down circuit

- parallel contacts A2/A4 and B2/B4 open and remove the ground from the right wing down circuit.

The standby aileron trim control relay 16CC energizes and latches, disabling the main trim circuit and switching on the STBY AIL annunciator as previously described.

28 VDC is now supplied to the left wing down side of the motor through: - contacts C2/C1 of relay 16CC

- the contacts of the actuator LH internal limit switch. The ground circuit for the motor is provided by:

- the contacts of the actuator RH internal limit switch (and then direct to ground if the actuator is at its maximum RH travel) or by the following series circuit:

- the contacts of the RH limit switch - contacts D1/D2 of relay 16CC

- the parallel contacts B8/B6 and A8/A6 of the standby trim switch 12CC.

The motor runs in the commanded direction until either the trim switch is released or until the LH internal limit switch operates. The operation sequence is similar in reverse when right wing down is commanded.

SYSTEM INDICATIONS

The aileron trim actuator has an integral synchro-type position transmitter. The transmitter sends an aileron trim position signal to data acquisition unit 1 (DAU 1) in the EICAS system for processing.

The aileron trim setting is indicated by a white pointer against an analogue scale on the primary and FLIGHT CONTROL pages of the EICAS.

CAS FIELD Indication MFD PAGE Indication

Fault or Condition white pointer against white

aileron scale Scale has white tic marks

every 25%.

white pointer against white aileron scale Scale has white tic marks every 25%.

Indicates aileron trim settings

Standby Trim/Main Lockout Circuit Status

A STBY AIL annunciator in the front face of the RESET switch/light 17CC indicates when the standby trim circuit and the main trim lockout circuit are active.

27-20 RUDDER CONTROLS AND TRIM

GENERAL

Rudder Pedal Assemblies

Spring Tab Lock Actuator Autopilot Servo Spring Tab Drive Mechanism

Rudder Trim Actuator

Quadrant Assembly Rudder Position Transmitter

Cable Quadrants

-24_°

20

°

Fig. 15 Rudder - General Arrangement

This section provides information on that portion of the flight control system which controls the position and movement of the rudder and the rudder trim tab. Also included are the indicating systems for the rudder position, the rudder limiter status and the trim tab position.

The section is divided into subsections containing detailed information on the following rudder and tab subsystems:

- Rudder Controls - Rudder Trim Rudder Controls

The aircraft is controlled about the yaw axis by a rudder control system. At airspeeds below 160 knots the dual rudder pedal assemblies are connected to a Flettner-type tab on the lower trailing edge of the rudder through a torsion bar and lever assembly. Movement of the rudder pedals drives the tab in the opposite sense to the yaw command and aerodynamic effects from the tab move the rudder in the commanded sense.

At speeds above 160 knots the lever assembly is locked by an actuator controlled by micro air data computers 1 and 2. The pedal assemblies are then effectively connected directly to the rudder and flight crew commands are not assisted by the tab. This limits the rudder deflection at high airspeeds and prevents structural overload conditions. The tab can be unlocked and the limiter actuator disabled by manually operating a switch in the flight compartment. A facility is provided for testing the actuator. The linkage from the pedal assemblies to the rudder and tab is by an arrangement of pulleys, cables, quadrants, push-pull rods, levers and bellcranks. The control cables exit the pressure compartment through pressure fairleads at the rear pressure bulkhead. Maximum rudder deflection is 24° right and 20° left.

Rudder Trim

The aircraft can be trimmed about the yaw axis by a trim tab located on the trailing edge of the rudder immediately above the spring tab. The tab is driven by an electrically powered linear actuator installed in the leading edge of the rudder.

The actuator is powered by a DC motor and controlled by a rudder trim switch in the flight compartment. Override circuits are provided to protect against a trim runaway. Test facilities are provided for the override circuits.

The rudder trim actuator can be disabled and re-enabled by a switch/light in the flight compartment.

INTERFACE TO OTHER SYSTEMS

Navigation System

The micro air data computers MADC 1 and 2 send discrete airspeed signals to the rudder limiter control circuit.

Communications

An amber RUDDER LIMITED caution message is displayed on page 2 of the radio management unit (RMU) if the rudder limiter is active at airspeeds lower than 155 knots.

Indicating /Recoording System

The following functions of the rudder and tab subsystem are indicated on EICAS: - the position of the rudder

- the status of the rudder limiter

- the position of the rudder trim actuator. Autoflight

Signals from the automatic flight control system (AFCS) are used to operate the rudder when the aircraft is flying under automatic control. Refer to (Chapter 22 - AUTO FLIGHT) for further details.

RUDDER CONTROLS

FUNCTIONAL DESCRIPTION

The rudder control subsystem consists of the following components:

FIN Component Panel Zone Access Door

LH (RH) rudder pedal assemblies 210, 120 123-AL, 211-FZF, 211GFZ, (122-AR, 212EFZ, 212-FZF) LH (RH) pedal adjustment assemblies 210,120 123-AL, 211FZF,

(122-AR, 212-FZF) LH (RH) forward quadrant assemblies 120 211-LZF, (212-KFZ

control rods 120, 320 various

control cables 120, 130,

140, 310

various

levers and bellcranks 120, 310 various

pulleys 120, 140,

310

various

pressure bulkhead fairleads 230 231-EFZ

LH (RH) fairlead brackets 130 221-FZF, (222-FZF)

aft quadrant assembly 310 312-AL, 324-AL

spring tab lever assembly 324 312-CL, 324-DL

torsion bar 324 324-AL, 324-DL

7CL rudder limiter actuator 324 324-DL

2CL TEST TAB LOCK switch/light 30VE (RH) 210

5CL RUD LIMIT switch/light 32VE 210

3CL, 4CL 160 knot relay 22VE 210

6CL manual rudder unlimit relay 22VE 210

9CL stby motor inhibit relay 22VE 210

16CX current detector 22VE 210

1CL, 8CL circuit breakers 12VE 210

LH and RH Rudder Pedal Assemblies

Rudder Pedal

Pedal Pivot for Wheel Brakes Pedal Adjust Handle

Rudder Pedal

Brake Actuating Rod Rods to NWS Rudder Command Potentiometer Push/Pull Rods to Quadrant Assembly Pedal Ajustment Assembly

Fig. 16 Rudder Components - Pedal Assembly

The rudder pedal assembly is a conventional pedestal mounted unit. Rudder commands are transmitted from the pedals to the forward quadrant assembly beneath the flight compartment floor by two push-pull rods and an idler lever. The idler lever of the LH (captain's) pedal assembly has a connection for the nose wheel steering potentiometer.

The pedals are mounted on pivots for controlling the wheel brakes. Brake actuating rods are connected to a lever at the pivot point. A pedal spring is connected between the brake operating mechanism of each pedal and the aircraft structure. The spring ensures that the brakes release when toe pressure is removed from the pedal.

LH and RH Pedal Adjustment Assemblies

A pedal adjustment assembly allows the rudder pedals to be adjusted to cater for the individual requirements of pilots. The pedals are adjusted by pulling a handle and allowing the pedals to move back under spring pressure or pushing the pedals forward. When the handle is released the pedals lock in the selected position. The handle is installed on a cover between the two rudder pedals.

LH and RH Forward Quadrant Assemblies Pressure Bulkhead Fairleads from Rudder Pedal Assemly Cable Faileads Control Cables forward Quadrant Assembly

Fig. 17 Rudder - forward Quadrant to Pressure Bulkhead

A quadrant assembly is installed below the flight compartment floor in the captain's and first officer's rudder control run. Each assembly consists of a single cable quadrant and an input lever on a common shaft. The push-pull rod from the associated rudder pedal assembly connects to the input lever. The assemblies form the starting point for the LH and RH control cable runs to the rear fuselage.

Control Cables

The rudder control cables transmit the flight crew rudder commands from the forward quadrant assemblies to the aft quadrant assembly at frame 49. The cables are 7 x 19 flexible steel wire ropes made from corrosion resistant steel and have a nominal diameter of 3.2 mm (0.13 in.). The LH and RH cable runs each consist of four separate cable sections. Cable sections are joined by turnbuckles and terminated by swaged end fittings.

Pulleys

The control cables are guided by pulleys equipped with cable guards. The pulleys are made of a phenolic material and run in sealed ball bearings. The complete cable run from the forward quadrant to the associated cable quadrant in the rear fuselage is guided by a total of twelve pulleys.

Control Rods

Each rudder pedal assembly is connected to its associated forward quadrant assembly by two aluminium push-pull control rods. Two rods connect the aft quadrant assembly at frame 49 to the spring tab lever assembly in the rudder, and a further two rods connect the lever assembly to the spring tab.

Levers and Bellcranks

The two control rods connecting each rudder pedal assembly to the associated forward quadrant assembly are supported by an idler lever. A bellcrank connects the two rods between the aft quadrant assembly at frame 49 and the spring tab lever assembly in the rudder. Levers and bellcranks run in sealed ball bearings. The connection points for the rod clevis ends are formed by self-aligning sealed ball bearings. Pressure Bulkhead Fairleads

The rudder control cables exit the pressure compartment through special fairleads at the rear pressure bulkhead. Each fairlead consists of a ball headed cable sleeve sandwiched between two plates. The plates are fixed to a bracket installed on and sealed to the lower part of the pressure bulkhead. The cable passes through the sleeve which acts as a cable seal.

Aft Quadrant Assembly

Rudder Drive Rod Bellcrank Assembly Push-Pull Rod RH Quadrant LH Quadrant Aft Quadrant Assembly

Autopilot Yaw Servo

from center fuselage

The aft quadrant assembly is installed on the upper forward face of frame 49. It forms the interconnection between the LH (captain's) and RH (first officer's) rudder controls. The assembly consists of a LH and a RH cable quadrant and an output lever on a common shaft. The LH quadrant has two functions:

- it terminates the cable run from the captain's rudder pedals

- it forms the connection point for the control cable from the autopilot yaw servo.

The RH quadrant terminates the cable run from the first officer's rudder pedals. The output lever is the connection point for a push-pull rod that continues the rudder commands into the vertical stabilizer. Spring Tab Lever Assembly

Spring Tab Locking Lever upper Torsion Bar

Output Lever

lower Torsion Bar

Connection to Rudder Spring Tab Lock

Actuator

Spring Tab Connection

Spring Tab Drive Rods

Command Input Rod

Actuator Connection to Rudder Connection to Rudder

Coupling Link Input Lever

Fig. 19 Spring Tab Lever Assembly

The spring tab lever assembly is installed in the lower leading edge section of the rudder. The assembly consists mainly of an input lever, a coupling link, an output lever and an upper and lower torsion bar. The input lever shares the same pivot axis as the rudder and acts through the coupling link on the output lever. The output lever is supported between the torsion bars and the rudder structure and has two functions:

- it drives the spring tab up to 160 knots as Flettner-Type (unlocked or not limited). - it drives the rudder directly at airspeeds above 160 knots (locked or limited). Rudder Limiter Actuator 7CL

The rudder limiter actuator is installed in the lower leading edge section of the rudder. The actuator has two separate (normal and standby) DC motors whose output shafts are mechanically connected to each other. The rotary output of the motors is converted in a reduction gearbox to a dual-shaft linear output. The output shafts of the actuator are connected to the rudder structure. The actuator body is connected to a locking lever. When the actuator is energized it moves the locking lever and either unlocks or locks the spring tab lever assembly. When the assembly is locked the rudder pedal assemblies are effectively connected directly to the rudder.

The control circuits for the two motors are mutually exclusive (external interlock circuits disable one motor when the other motor is enabled). The normal motor is controlled by signals from micro air data computers 1 and 2. The motor is driven automatically in either direction as follows:

- to retract the actuator and lock the spring tab above 160 knots (increasing airspeed) - to extend the actuator and unlock the spring tab below 155 knots (decreasing airspeed).

The standby motor is controlled by the RUD LIMIT switch/light 5CL. The purpose of this motor is to drive the actuator to the tab unlock position on a manual command from the flight crew. The standby motor cannot drive the actuator to the tab lock position.

Internal limit switches for both motors stop actuator movement before the mechanical travel limits are reached.

The actuator has an integral position transmitter. The transmitter is a three wire potentiometer whose resistance changes as a function of the actuator position. The transmitter signal is used in conjunction with the signals from the air data computers for indicating the status of the rudder limiter.

TEST TAB LOCK Switch/Light 2CL

+

-TRENDR IMTREC REFUEL QTYQTY

EXCEED REC/FDR UN-LIMIT R U D L I M I T ARM OFF TEST LOCK AUX PUMP ENG RH ENG LH RH 3 4 3 4 ENG-TRIM TAB LH GO ACTR A B

B

A

Test Tab Lock Switch/Light 2CL

Rudder Limit Switch/Light 5CL

Fig. 20 Rudder - Limiter Controls

The TEST TAB LOCK switch is a press-to-test switch/light used to test the lock/unlock circuit of the normal motor of the rudder limiter actuator. It is installed in the RH engine/propeller test panel 30VE located in the forward RH section of the center pedestal.

To test the lock circuit, press and hold the TEST TAB LOCK switch. If the circuit is serviceable, the actuator runs to the lock position. This is indicated by an ACTR GO caption which comes on in the front face of the switch. When the switch is released the actuator returns to the unlock position and the caption goes out.

RUD LIMIT Switch/Light 5CL

The RUD LIMIT switch is a press in/press out switch/light. It is installed in control panel 32VE located in the aft LH section of the center pedestal. The switch is used to manually unlock the spring tab (switch off the rudder limiter) should the flight crew consider this necessary.

Under normal operating conditions the switch/light is pressed in and the rudder limiter circuit is armed. At the discretion of the flight crew the switch can be pressed out to drive the rudder limiter circuit prior to the airspeed reaching 160 knots to unlocked the spring tab assembly.

When the switch is pressed out an UNLIMIT caption in the front face of the switch comes on to indicate that the rudder limiter is inoperative. The switch also sends a signal to the EICAS for processing. The signal is used to indicate that the rudder limiter is manually disabled.

Current Detector 16CX

The current detector consists of a shunt, an amplifier and a relay. The shunt is connected in series with the normal motor of the rudder limiter actuator and thus senses motor current. The amplifier is connected across the shunt and controls the ground circuit of the relay. The relay has two sets of contacts and energizes when the normal motor is operating (in either direction). One set of contacts is connected in the actuator test circuit. The other set disables the actuator's standby motor is open when the normal motor is operating.

Rudder Position Transmitter 19CX

A

A Rudder position transmitter Bracket

Lever Rod

Fig. 21 Rudder Components - Position Transmitter

A rudder position transmitter is installed on a bracket in the trailing edge of the vertical stabilizer at rib 3. A short rod attached to a lever in the leading edge of the rudder drives the transmitter. The unit is a three-wire potentiometer whose resistance changes as a function of the rudder position. It sends a 0 to 10 kΩ variable resistance signal to the EICAS for rudder position indicating.

OPERATION

Power Supplies

Component BUS Circuit Breaker No.

rudder limiter actuator (normal operating) ESSENTIAL BUS 3PP RUD LIMIT 1CL rudder limiter actuator (standby operating) BUS 1 2PP STBY RUD LIMIT 8CL

System Power-Up

The control and status indicating circuits for the rudder limiter actuator are energized when 28 VDC is applied to the aircraft bus system.

Rudder Controls

Flight Compartment to Vertical Stabilizer Control Run

Rudder pedal movement is transmitted by two push-pull rods and an idler lever to the forward quadrant assembly located at frame 9. The idler lever in the LH control run has a connection point for the nose wheel steering potentiometer

From the forward quadrant assembly, the movement is continued aft below the flight and passenger compartment floor by control cables and pulleys. The cables pass through guides in some frames under the floor. Cable fairleads equipped with small pulleys are used to guide the cables through the machined parts of frames 24 and 26. The cable run is virtually straight as far as a point between frames 33 and 35. At this point the cables are routed inboard and then upwards to follow the contour of the fuselage. The cables exit the pressure compartment through sealed fairleads at the rear pressure bulkhead. The cable run terminates at the aft quadrant assembly on the forward face of frame 49.

The aft quadrant assembly forms the interconnection between the LH (captain's) and RH (first officer's) rudder controls. The assembly has two cable quadrants and an output lever on a common shaft. The LH quadrant terminates the cable run from the captain's rudder pedals. The autopilot yaw servo is connected by a cable to the rudder control run at the LH quadrant. The RH quadrant terminates the cable run from the first officer's rudder pedals. The output lever serves as the connection point for a push-pull rod which continues the rudder commands into the vertical stabilizer.

The push-pull rod exits the fuselage immediately forward of the vertical stabilizer rear spar. The rod connects to a bellcrank assembly installed on the forward face of the rear spar between vertical stabilizer ribs 2 and 3. A short push-pull rod is connected to the output side of the bellcrank. This rod is the command input rod for the spring tab lever assembly

Spring Tab Lever Assembly

Flight crew yaw commands act through the input rod directly on the input lever. The movement is transmitted by the coupling link to the output lever which is installed between the upper and lower torsion bars and the rudder structure. The output lever is connected directly to the spring tab by the tab drive rods which deflect the tab in the opposite sense to the yaw command.

Aerodynamic effects from the tab deflect the rudder in the correct sense. Rudder deflection at airspeeds below 160 knots is thus a function of rudder pedal movement and airspeed and the deflection angle is only limited by mechanical stops.

At 160 knots micro air data computers (MADC) 1 and 2 send a signal to the control circuit of the rudder limiter actuator. The actuator moves the locking lever into a position which locks the spring tab lever assembly to the rudder structure. This effectively connects the rudder pedals directly to the rudder and prevents the spring tab from moving in relation to the rudder. Yaw commands from the flight crew now receive no assistance from the tab and rudder deflection is limited by aerodynamic forces.

328

DORNIER LUFTFAHR

T

42

FOR TRAINING PURPOSES ONLY

-Effectivity: 328-100 Mod.10 TM-Flight Controls <160kt=OPEN >160kt=GND <160kt=OPEN >160kt=GND 5A 1CL 2 1 RUDDER LIMIT 5A 8CL 2 1 STBY RUD LIMIT X2 X1 3CL X2 X1 4CL SIGN 653 SIGN647 A3 A1 A2 5CL RUD LIMIT UNLIMIT NORM B3 B1 B2 C3 C1 C2 1TU SIGN 660 DAU 1 B2 D1 D2 16CX X1 X2 9CL X1 X2 6CL 13 15 C O T 1 2 3 4 5 6 7 8 9 13 15 C O T 13 15 C O T 16 18 19 C O T 4 10 C O T DIMMER 2LF TEST +28V UNLIMIT C2 C1 2CL C3 B2 B1 B3 A2 A1 A3 TEST LAB LOCK A2 A3 C3 16CX 1CW STANDBY ACTR GO 17CX TEST LAB LOCK CD A1 D1 X2 16CX A1 A3 A2 A1 A3 A2 A3 A1 A2 6CL 7CL LOCK ACTR NORMAL OPERATING OFF FILTER M 10 11 12 13 14 15 16 17 B1 B3 B2 B1 B3 B2 B3 B1 B2 4CL 3CL C3 C1 C2 ON STBY OPERATING OFF FILTER M ON 18 19 20 21 22 23 D2 D1 D3 6CL A2 A1 A3 9CL 11TU LO W HI SIGN 621 DAU 2 C = closes O = opens T = change over(transition) Fig.