Learjet 31A

Pilot's Manual

TABLE OF CONTENTS

FLIGHT SYSTEMS

Flight Controls . . . . .. . . .. . . . . . . .. . . . . . . . .. .. .. . . .. .. .. .. . . . . .. .. .. .. .. . . .. .. .. . . . . . . . . . .. . . . . . . . . .. .. .. .. 5-1Aileron and Elevator . . .. . . . . . . . .. .. .. . . .. .. .. . . . . . . .. .. . . .. . . . . .. .. . . . . . . . . .. . .. . . . . . . . ... .. .. . . .5-1Rudder. . . .. .. . . . . . .. .. . . .. .. . . . . .. . . . .. . . .. .. .. .. .. .. .. . . .. . . .. .. .. .. . . . . ... . . . . . . . ..... .. ... . . . . ... .. .. .. .5-1Controls Gust Lock. . . . . . . . .. . . . . .. .. . . . . .. .. .. . . . . . . .. .. .. .. .. . . .. .. . . . . . . . . . . . .. . . . . . . . . .. .. .. . . .5-2Controls Gust Lock (Figure 5-1) . .. . . . . . . . . . . .. .. .. .. .. . . .. .. . . . . .. . . . .. .. . . . . . . . . .... .. . . 5-2Flaps . .. .. .. .. . . . . . .. .. .. . . .. .. . . . . . . . . . .. . . .. .. . . .. .. . . .. . . . . . . .. .. .. .. . . . . .. . .. . .. . . . . . .. .. . . . . . . . . .. .. .. . . .5-3Flap Selector Switch . . . . . .. . . .. .. .. .. .. .. .. . . . . . . .. .. .. .. . . . . .. .. . . . . . . . . . . .. . . . . . . . . . .. .. .. . . .5-3Flap Position Indicator . . . . .. .. .. . . .. . . .. . . .. . . .. . . .. .. . . . . .. .. . . . . . . . . . . . . . . . . .. . . . . . .. .. . . . 5-3

Spoilers .. .. . . . . . . . .. .. . . .. .. . . . . .. . . . . . . . .. .. . . . . .. .. .. . . .. . . .. .. .. .. .. . . .. .. . .. . . . . . . . . .. . . . . . . . . .. .. .. . . . 5-4SPOILER Switch . . . . . . .. . . .. . . . .. .... . . .. .. .. .. .. . . .. .. .. .. .. . . .. .. . . . . .. . . . . ... . . . . . . . . ...... . . .5-4SPOILER Light . . . .. .. . . .. . . . . . . . .. .. .. . . .. . . .. . . . . . . .. .. .. .. .. . . .. .. .. . . .. . . . . . . . . . . . . . . . .. .. .. .. .5-4

Warning Systems . .. . . . . .. . . .. . . . . . . . .. . . .. .. .. .. .. . . .. . . .. .. .. .. .. . . .. .. .. . . .. . . . . . .. .. . .. . . . .. .. .. . . .5-5Stall Warning System . .. . . . . .. . . . . . .. .. .. . . .. . . .. .. .. .. .. .. .. . . .. .. . . . . . . . .. . . .. . . . . . . .. .. .. .. .. .5-5Stall Warning System Block Diagram (Figure 5-2) . . . . . .. . . . . .. . . . . .. .. .. .. .. . 5-6Angle-of-Attack Indicators . . . .. .. . . .. .. .. . . .. . . .. .. .. . . .. . .. .. . .. . .. . . .. .. . . . . .. .. .. .. . . . 5-7STALL Warning Lights . . . .. .. .. .. .. . . .. . . .. . . .. .. .. .. .. . . .. ... .. . . . . .. .. .. .. . . .. .. .. .. .. .. .5-7SYSTEM TEST Switch- Stall Warning Function . . .. .. .. .. . . .. .. .. .. .. .. 5-7

Overspeed Warning System .. .. .. .. . . .. . . .. . . .. .. .. .. .. . . .. ... .. . . . . .. .. .. .. . . . . .. .. .. .. .. .5-8SYSTEM TEST Switch- Overspeed Warning Function . .. .. .. .. .. .5-8

Traffic Alert and Collision Avoidance System (TCAS-1) .. . . . . .. .. .. ..5-8ATraffic Alert and Collision Avoidance System (TCAS-II) .. .. . . .. .. .. ..5-8AGround Proximity Warning System withWindshear Warning (GPWS) . .. .. .. . . .. . . .. .. .. . . . . . . .... . .. . . . . .. .. .. .. . . . . .. .. .. .. 5-8B

Enhanced Ground Proximity Warning System withWindshear Warning (EGPWS).. .. . . . . .. . . .. .. .... .. . . .. . .. .. . . . . .. .. .. .. .. .. .. .. .. ..5-8C

Mach Trim System . .. .. . . . . ... .. .. .. .. .. .. . . .. ... . .. . . . . .. ... . .. .. . ....» .. . . . . .. .. .... . . .. .. .. . . .. .. .5-9PITCH TRIM Selector Switch -Mach Trim Function . .. .. .. . . .. .. .. .. .. . 5-9MACHTRIM Light . . . . ... .. .. .. .. .. . . . . .. .. . .. . . . . . .. .. .... ... .. .. .. .. . . .. .. . . . . .. .. .. .. .. .. .. .5-10SYSTEM TEST Switch -Mach Trim Function . .. .. . . .. .. .. .. .. . . .. .. .. .. . . . 5-10

Pitch Trim System .. .. . . . .. . .. ... .. .. .. . . .. . . .. . . . . . . . . . . .. ... . . . . .. .. .. .. .. . . .. .. . . . . .. .. .. .. . . . . . . . 5-11PITCH TRIM Selector Switch . . . . .. .. . .. . . . . . .. .. .. . . . .. . . .. .. .. . . .. . . .. . . .. .. .. .. . . . . . . . 5-11Control Wheel Trim Switches- Pitch Function . .. . . . . . . . . . . .. .. .. . . . . . . . . . 5-12Pedestal NOSE DN-OFF-NOSE UP Switch . .. .. .. .. .. . . .. . . .. .. .. .. .. .. . . . . . . .5-12Control Wheel Master Switches - Pitch Trim Function. .. .. .. .. . . . . . . . 5-12Pitch Trim System Block Diagram (Figure 5-3) .. .. .. . . . . . . . . . . .. .. .. . . . . . . . . .5-13

Pilot's Manual

Learjet 31A

TABLE OF CONTENTS (Copt)

PITCH TRIM Light .. . . . . . . .. .. .. . . .. .. . . . .. . . . . . . . .. .. .. . . .. .. . . .. .. .. . . . . . . . . . .. . . . . . . . . . . . . . . 5-14T.O. TRIM Light . . . . . . .. . . . . . . .. .. .. . . . . .. . . . . . . . . . .. . .. .. . . .. .. .. . . .. .. .. .. . . . . .. .. . . .. .. . . .. . . . . . 5-14SYSTEM TEST Switch Trim Monitor Function ... .. . . .. .. .. .. .. .. . . .. ... . .5-14SYSTEM TEST Switch - Trim Overspeed Function. .. .. . . .. . . .. . . .. .. .. . 5-14PITCH TRIM Indicator . . . . . . . . . . . . .. .. .. .. . . . .. .. .. . . . . . . .. . .. . . . . . . . . .. .. .. . . . . . . .. .. .. .. .. . 5-14Trim-in-Motion Audio Clicker . .. .. .. . . . .. . . .. .. . . . . .. .. . . .. . . . . . .. .. .. . . . . . . . . .. .. . . .. . 5-15

Roll Trim System .. .. .. .. .. .. .. .. .. .. .. . . . . ... .. .. . . . .. . . . . .. . . . . .. .. .. .. . . . . .. . .. . . . . . . . . .. .. .. .. . . . 5-15Control Wheel Trim Switches- Roll Function . .. . . .. .. . . . . . . . . .. ... .. . . . . . 5-15Aileron Trim Indicator . .. . . .. .. .. .. .. ... .. .. . . . . . . . . ... .. .. .. .. .. .. . . .. .. . . . . . . . . .. . . . .. . . . . .5-16

Trim Indicator Panel (Figure 5-4) .. .. ... .. .. .. . . . . ... .. .. . . .. .. .. . . .. .. .. . . . . . . .. .. .. . . . . . . 5-16Pedestal Trim Control Panel (Figure 5-5) . . . .. . .. .. . . . . ... . .. .. .. .. .. .. . . .. .... . . .. . . 5-17Yaw Trim System . .. . . . . .. .. . . ... . . . . . ... .. .. .. . .. .. .. .. . . . . ... . . .. . . . . . . .. .. .. .. .. .. .. . . .. ..... . ... . 5-17RUDDERTRIM Switch . . . . . . . .. . .. .. ..... . . .. .. . . . . ... .. .. . . . . . ... .. .. .. .. .. .. .. .

. . ... 5-17RUDDERTRIM Indicator . . . ..... .. .. ... .. .. .. .. . . ... . . . .. . . . . .. . .. .. .. .. .. .. . . .. .... .. .. .. 5-18

Autopilot/Flight Director System . .. . .. . . .. .. .. .. . . .. . . . . . . .. ... .. .. .. .. .. .. .. .. .. .. .. .. 5-18Autopilot Controller .. . . .. .. .. .... .. ... . . .. . . . .... .. .. .. .. .. .. .. .. .. . .... . . .. .. .. .. .. .. .. .. ....5-19Autopilot Controller (Figure 5-6) .. .. . .. . ... .. .. .. .. .. . . .. ..... .. . . .. . . .. .. .. .. .. .. .. .. 5-19Autopilot/Yaw Damper Engage Functions . . . .. .. . .. . . .. . ... . . .. .. .. . . .. .. 5-20Autopilot/Flight Director Modes . . . ..... .. .. .. .. .. .. .. ... .. . . .. .... . . .. . . . . .... .. 5-20

Attitude Hold .... .. . . .. .. .. .. .. . . .... . .. .. . . . . . . . .. .. .. .. .. .. .. .. ... .. . . . . .... . .. . .. .. .... . . 5-20HDG (Heading). . . . .. .. .. .. .. .. .. . . . .. .. .. .. . . . .. .. .. .. .. .. .. .. ... ... . . . . ... .. .... .. .... ..5-21HALFBANK.... .... . . .. .. .. .. .. .. .. .. . .. .. . . . . . . . . . .. .. .. .. .. .. .. .. . .. . . . . .. ... .. . . . . . .. .. .. 5-21NAV (Navigation) . .. .. .... .. . . .. .. . . . .. .. . . .. . .. .. . . . . .. .. .. .. .. .. .. . . . . .... .. .. . . . . .. . . .5-21APR (Approach) . .. .. . .. .... .. . . .. .. . . . .. .. . . .. .. ... . . . . .. .. .. .. . . .. .. .. .. .. .. . . .. . . . . .... .5-21ALT SEL (Altitude Select) .. .. . . . .. .. .. .... ... . . . . . ... .. .. . . .. .. .. .. .. .. . . .. .. .. .. .. . 5-21ALTHOLD (Altitude Hold) . . . .. .. .. .. .. .... . . . . .. . . . . . .. .. . . .. .. .. .. . . .. .. .. .. .. . 5-21CLB (Climb) .. .. .. .. .. ... . ..... .. . . .. .. .. . .. .. .. .. .. ... . . . . ... .. . .... .. .. .. .. .. . . . . .. .. .. .. .. . 5-21DES (Descend) .. .. .. .. . . .. .... . . . .. .. . . . . . . . .. .. .. .... . . . . .. ... .. . . . . .. .. .. .. .. . . .. .. . . .. .. . 5-22MACH (Mach Hold).. .. . .. . . .. .. .. . .. . . .. .... ... . . . . ... .. . . . . . .. .. .. .. .. . . . . .. .. .. .. .. . 5-22IAS (Indicated Airspeed Hold) . . .. .. .. .. .. . . . . .. . . . . .. . . . .. .. .. .. . . . . .. .. .. .. .. .5-22VNAV (Vertical Navigation) .. . .. . . .. .. . . .. .. . . . . .. . . .. . . . .. . . .. .. .. . . . . .. .. .. .. .. .5-22VS (Vertical Speed Hold). . .. .. .. . . . . . .. .. . . .. .. . . . . .. . . . . .. . . . . . .. .. ... . . . .. .. .. .. .. .5-22Go-Around .. .. .. .. .. .. .. .. .. .. .. . . . . . . . .. .. . . . .. .. . . .... .. . . .. . . . .. . .. . .. .. .. .. . . . . .. .. .. .. .. . 5-22

Status Annunciators .. .. .. .. .. .. .. . . . .. . . . . . .. .. . . .. . . . . . . .. . . ... . . . . . . .. .. .. . . . . .. .. .. .. 5-22AControl Wheel Master Switches- Autopilot Function . . . . . .. .. .. .. .. . 5-23PITCH TRIM Selector Switch- Autopilot Function . .. .. . . . . .. .. .. .. .. . 5-23Control Wheel Switches (Figure 5-7) . .. . . . . .. . . . . .. .. . . .. . . . . ... .. .. . . . . .. . . .. .. .. . 5-23Control Wheel Trim Switches- Autopilot/Flight

Director Function . . . .. .. .. . . .. .. .. . . . .. .. .. . . . .. . . .. . . . . . . .. . . . .. . . . . .. .. .. .. . . . . .. .. .. .. .. . 5-24Pedestal NOSE DN-OFF-NOSE UP Switch - Autopilot

Function . . .. . . .. .. . . . . . . . . .. . .. .. . . . . . . .. . . . .. .. .. . .... . . . . . . . . . . .. .. .. .. . . . .. .. .. .. . . . . .. .. .. .. .. . 5-25

Learjet 31A

Pilot's Manual

TABLE OF CONTENTS (Cont)

Control Wheel Steering (CWS) Switches . .. .. . .. . . . . . . .. . . .. . . . . . . . . . . .. . . . . . . . . .5-25Control Wheel FD CLEAR Switches . . . . . . . . .. .. . . . . . . . . . . . . . .. . . . . . . . . . . .. . . . . . . . . .5-25SYSTEM TEST Switch -A/P RESET Function . . . . . . . . . . . . . . . . . . .. . . . . . . . . .5-26

Yaw Damper System . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . .5-26Yaw Damper Control . . . . . .. . . .. . . . . . . .. . . . . . . . . . . . . . .. .. . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . .5-26Control Wheel Master Switches -Yaw Damper Function . . . . . . . . . . . 5-26

Rudder Boost System . . . . . . . . . . . . . . . . .. . . .. .. . . . . . . . . . .. .. .. .. . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-27RUDDER BOOST Switch . . . . .. . . . . .. . . . . . . . . . . . . . .. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-27Control Wheel Master Switches - Rudder Boost Function . . . . . .. . .5-27Rudder Boost Block Diagram (Figure 5-8) . . . .. .. . . . .. . .. . . . . . . . . . . . . . . . . . . . . . . . .5-28

Attitude Heading System (AHS 1 and AHS 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..5-29Heading Control Switches .. . . . . . . .. . . .. . . . . . .. . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . .5-30AHS 1 and AHS 2 Annunciator Lights . . . . . .. . . . . . . . . . . . . .. . . . . . . . . . . . . .. . . . . . . . . . . 5-30AHS 1/AHS 2 Reversionary Mode . . . . . . . . . ... . . . . . . .. . . . . .. .. . . . . . . . . .. .. .. .. . . .. . .5-30

Electronic Flight Instruments System (EFIS) . . .. . . .. . . .. .. .. . . . . . . .. . . . . .. .. . . .. . .5-31Electronic Attitude Director Indicator (EADI) . . . . .. .. . . . . . . . . .. . . . . .. . . . . .. . .5-31Electronic Horizontal Situation Indicator (EHSI) . . . . . .. . . . . .. . . . . .. .. . . .. . .5-31EFIS Control Panel .. . . .. .. .. . . . . . . .. . . . . . . . . . . . .. . . .. .. . .. . . .. .. .. .. .. .. .. . . . . . . .. . . .. .. .. . . .. . .5-32EFIS Control Panel (Figure 5-9) . . . . . . . .. . . .. . . . . . . . . . .. .. . . .. . . . . . . . . .. .. . . . . .. . . . . .. . .5-32Multifunction Display (MFD) . . . . . . . . . . .. . . .. . . . . . . . . . . . .. .. .. . . . . . . . . . . . . . . . . .. .. . . .. . .5-32MFD Control Panel . .. .. .. .. .. . . . . .. . . . . . . . . . .. .. . . .. .. ... . . .. .. .. .. .. . . .. .. . . . . .. . . .. . . .. . . .. . .5-32MFD Control Panel (Figure 5-10) . . .. .. . . .. . . ... . . . . .. .. .. .. . . . . .. . . . . .. . . . . .. .. .. .. . .5-33EFIS Reversionary Control Panel . . .. .. . . .. . . ... . . . . .. .. .. .. . . . . . . . . . . .. . . . . . . .. . . .. ..5-33EFIS Reversionary Control Panel (Figure 5-11) .. .. . . . . .. . . . . .. . . . . .. .. . . .. . .5-34

Flight Instruments . . . . . . .. . . . . . . .. . . . . .. .. . . . . . . . . . . . .. .. . . . . . . . . . . . .. . . .. . . .. .. . . . . .. . . .. . . .. .. .. . .5-34Airspeed/Mach Indicators . . .. .. .. . . . . . .. . . .. .. . . .. .. . . . . . .. . . .. . . . . .. . . .. .. .. . . . . .. .. .. . .5-34Airspeed/Mach Indicator (Figure 5-12) . .. . . . . . .. .. .. .. . . . . .. . . . . .. . . . . . . .. .. .. . .5-35Altitude/Vertical Speed Indicators . . . .. .. .. .. . . . . . . . .. .. .. . . . . .. .. . . .. . . . . .. .. .. .. . .5-35Altitude/Vertical Speed Indicator (Figure 5-13) .. . . . . .. . . .. .. . . . . .. .. . . .. . .5-36Speed/Temperature Indicator . . . . . . . .. .. .. .. . . .. . . . . . . . .. .. .. . . . . .. .. . . .. . . . . . . .. .. .. . .5-37Speed/Temperature Indicator (Figure 5-14) . .. . . .. .. . . . . .. . . .. .. . . . . . . .. .. .. . .5-37Standby Airspeed/Mach Indicator . .. .. .. . . .. . . . . . . . .. . . .. . . . . . . . . . . .. . . . . . . .. .. .. . .5-37Standby Altimeter . .. .. .. .. .. .. .. . . .. .. . . . . . . . .. .. . . .. .. .. . . . . . . . .. .. .. . . .. . . . . . . .. . . .. . . .. . . .. . . 5-38Standby Airspeed/Mach Indicator and

Altimeter (Figure 5-15) . . . . .. .. . . . . . . . . . .. . . .. .. .. . . . . . .. .. .. .. . . . . . . . . . . .. . . .... .. . . .. . .5-38Standby Attitude Indicator . . .. .. . .. . . . . .. .. .. .. .. ... . . .. .. .. . . .. . . .. . . . . . . . . . . . . . . . . . . .. . . 5-38Standby Attitude Indicator (Figure 5-16) . . . . . . .. .. . . .. . . . . . . . . . . . . . . . . . . . . . . . . .. 5-39Standby Horizontal Situation Indicator (HSI) .. . . .. .. . . . . . . . . . . . . .. . . . . . . . . ..5-40Standby Horizontal Situation Indicator (Figure 5-17) . . . . . . . . . . . . . . . . . . .5-40

Pilot's Manual

Learjet 31A

TABLE OF CONTENTS (Copt)

Pitot-Static System . . . . . . . . . . . .. . . . .. . . .. . . . . . . . .. . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . .. . . . 5-41STATIC SOURCE Switch . . . . . . . . . . . . . . . . .. .. . . . . .. . . . . . . . . . . . . . . . . . . . . . .. .. . . .. .. . . . . . . . . . . 5-41Pitot-Static System (Figure 5-18) . . . . . .. . . . . . . .. . . . . . . . . . . . . . . . .. . . .. .. . . .. .. . . . . .. . . . . . . 5-42

Air Data System (ADC 1 and ADC 2) . . . . . . . . . . . . .. .. . . .. . . . . . . . . . . . . . . . .. . . . . .. .. . . . . 5-43SYSTEM TEST Switch-ADC Function . . . . .. . . . . .. .. . . .. . . . . . . . .. . . . . .. .. . . .. .. 5-44

Takeoff Configuration Monitor System . . . . . . . .. .. . . .. .. . . .. .. . . . . . . . . . . . . . . . .. .. . . . . 5-44Audio Control System . .. . . . . . . . .. .. . . . . . . . .. . . .. . . . . . . . . . .. .. . . . . . . .. . . .. . . . . . . . . . . . . . . . .. . . . . . . 5-45Audio Control Panel .. .. .. . . . .. .. . . .. . . . .. .... .. . . . . . . . .. .. . . . . . . . . .. .. .. .. .. . . . . .. .. . .. . . . . . . 5-45TRANSMIT SELECT Switch . . . . .. .. .. .. . . . . . . . .. .. . . . . . . . . .. .. .. .. .. . . . . . . .. . .. . . . . . . 5-45MIC SELECT Switch . . . . . . .. .. .. .. . . ... . . .. .. .. .. .. . .. . .. . . . . . . . . . .. . . .. .. .. . . .. .. . .. . . . . . . 5-46Volume Controls .. .. . . . . . . . . . .. .. .. .. . . ... . . .. .. .. .. .. . . . . . . . . . . .. . . . .. .. .. .. .. . . .. .. . . . . . . . . . 5-46Speaker Switch . ..... . . . . .. . . . . . .. .. .. .. .. . . . . . . . .. . . .. .. . . . . . . . . .. . . . .. .. .. .. .. . . .. .. . . . . . . . . . 5-46Mixer Switches ... ... . . . . .. .. . . . .. .. .. .. .. . . . .. .. .. .. .. .. .. .. . . .. .. . . . .. .. . . .. .. .. .. .. . ... . . . . .5-47BOTH/VOICE/IDENT Switch . . . . . . . .. .. .. .. .. . . . . . . .. . . . .. .. . . . . .. .. .. .. . . . . . . . . .5-48MICRHI/LO Switch . .. .. . . . .. .. .. . . . . .. . . . . . .. .. .. .. .. . . . . .. .. .. .. . . . . . .. .. .. .. .. . . .. . . . . . 5-48

Audio Control- Flight Operation . . . ... .. .. .. .. .. . . .. .. .. .. .. . . . .. . . .. .. . . .. . . .. . . . 5-48Flight Management System .. .. . . ... . . . . .. . . . . ... .. .. .. .. .. . . .. .. .. .. . . . . . . . .. .. .. . . .. .. . . . . . 5-49UNS-1B Flight Management System/KFC 3100 Flight Control System Interface .. .. .. .. .. .. . . . . . . . .. . . . . .. .. .. .. . 5-49Enroute .. . . . . . .... . .. .. . . .. .. .. . . . .. .. .. .. . . . . . .. . . .. .. ... .. .. .. . . .. .. .. .. .. .. . . . . .. . .. .. .. .. .. . . .. .5-49Enroute VNAV .. . . . . .. .. .. . . . . . .. .. .. . . . . . .. . . . . .. . .. .. . . .. .. .. .. .. .. .. .. . . . . .. . .. .. . . .. .. .. . . . 5-50Approach Mode (Lateral) .. .. . . . . . .. .. . . .. . .. .. . . .. .. .. .. .. .. .. .. . . . . ... .. .. .. .. .. .. . . . 5-50Approach Mode (Vertical) . .. .. . . . . . .. . . .. .. . .. . . . . . . .. .. .. .. .. .. .. . . .. ... .. . . .. .. .. .. . 5-51

Learjet 31A

Pilot's Manual

FLIGHT CONTROLS

The primary flight controls (ailerons, elevator, and rudder) are me-chanically operated through the control columns, control wheels, andrudder pedals. The flaps and spoilers are hydraulically operated andelectrically controlled . Aircraft trim systems (pitch, roll, and yaw) areelectrically operated and controlled .

AILERON AND ELEVATOR

Movement of the control columnsand control wheels is mechanicallytranslated into elevator and aileron control surface movementthrough systems of cables, pulleys, and push-pull rods. In addition toaileron control, the control wheels incorporate switches that controlnormal trim, pitch-axis interrupt, rudder boost interrupt, autopilotand yaw damper disconnect, autopilot control wheel steering (CWS)function, flight director dear, microphone keying, transponder identfunction, and nose-wheel steering engage and disengage circuits.Control wheel switch functions are discussed under the applicablesystem.

RUDDER

FLIGHT SYSTEMS

Rudder pedal movement is mechanically translated into rudder con-trol surface movement through a system of cables, pulleys, and bell-cranks. Nose-wheel steering, when engaged, is electronically con-trolled by the pedals and braking maybe accomplished by depressingthe upperportion of the pedals .

PM-121

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Pilot's Manual

Learjet 31A

CONTROLS GUST LOCK

Acontrols gust lock is provided to help prevent wind gust damage tothemvable control surfaces. When installed, the lock provides secur-ity by holding full rudder, full aileron, and full down elevator.

CONTROLS GUST LOCKRgureS-1

141LSA

5-2

PM-121Original

Learjet 31A

Pilots Manual

FLAPS

The hydraulically-actuated, electrically-controlled flap system pro-vides flap settings of UP V), 8°, 20°, and DN (40°). The single-slottedflaps are attached to the rear wing spar with tracks, rollers, and hing-es. The flap selector switch controls a solenoid-operated hydrauliccontrol valve that meters hydraulic pressure to the flap actuators. Theactuators mechanically rotate sectors attached to the flaps through ad-justable push-pull tubes. Interconnecting cables and pulleys syn-chronize flap movement throughout the range of travel . A flap posi-tion switch is mechanically connected to each flap sector. Theseswitches provide flap position information to the landing gear warn-ing, stall warning, spoiler warning, trim-in-motion warning, takeoffconfiguration monitor system, and rudder boost systems. A flap limitswitch is mechanically connected to each sector to automaticallymaintain flap position at the selected setting. The flap control systemoperates on 28 VDC supplied through the 3-amp FLAPS circuit break-er on the copilot's circuit breaker panel. The flap control system is op-erative during EMER BUS mode.

FLAP SELECTOR SWITCHThe flap selector switch is located on the right side of the pedestalnear the thrust levers. The switch has four positions: UP, 8, 20, andDN. When 8° or 20° flaps are selected, 28 VDC is directed to the appli-cable (up or down) solenoid of the flap control valve. The flap controlvalve will meter hydraulic pressure to the flap actuators and movethe flaps in the desired direction. As the flaps approach within 1° ofthe selected setting, the applicable flap limit switch will remove pow-er from the flap control valve solenoid and flap travel will stop . WhenUP is selected, 28 VDC is directed to the up solenoid of the flap con-trol valve and the flaps will move in the up direction. When DN is se-lected, 28 VDC is directed to the down solenoid of the flap controlvalve and the flaps will move in the down direction. When the flapsreach full extension, the "down" pressure will remain to maintain theflaps full down.

FLAP POSITION INDICATORThe vertical-scale FLAP position indicator, mounted in the centerswitch panel, provides the crew with visual indication of flap posi-tion . The indicator face consists of a scale, which has markings for UP(0°), 8°, 20°, and DN (40°), and a pointer on the right margin of thescale. A potentiometer connected to the left flap sector transmits theflap position signal to the indicator . The indicator operates on 28 VDCsupplied through the 2-amp TRIM-FLAP IND circuit breaker on thecopilot's circuit breaker panel.PM-121

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Learjet 31A

SPOILERS

The spoilers are located on the uppersurface of the wings forward ofthe flaps. The spoilers are electrically controlled and hydraulically ac-tuated. The SPOILER switch on the forward pedestal is used to sym-metrically extend and retract the spoilers. As the switch is moved tothe EXT position, the solenoid valve directs hydraulic pressure to theextend port of the spoiler actuators which causes the spoilers to ex-tend . As the spoilers unseat and extend through 1°, the amber SPOIL-ER light will illuminate signifying the spoilers are not retracted andlocked. The spoilers will fully extend in 5 to 7 seconds. Full extensionis approximately 47°. However, during flight, a pressure relief allowsthe spoilers to "blow down" to a lesser extension angle. When BET isselected, the solenoid valve will direct hydraulic pressure to the re-tract port of the spoiler actuators which causes the spoilers to retract.When retracted, the spoilers are secured by an internal locking mech-anism in the actuators. During normal operation, the spoilers will ful-ly extend or retract in approximately 5 to 7 seconds. Spoiler controlcircuits operate on 28 VDC supplied through the 3-amp SPOILER cir-cuit breaker on the copilot's circuit breaker panel. The spoiler controlsystem is operative during EMER BUSmode.

SPOILERSWITCH

Symmetric extension and retraction of the spoilers is controlledthrough the SPOILER switch located on the right side of the pedestaladjacent to the thrust levers. The switch is guarded to prevent inad-vertent spoiler actuation. The switch has two positions: EXTand RET.When the switch is set to EXT, both spoilers will extend and theSPOILER light will illuminate. When the switch is set to RET, bothspoilers will retract.

SPOILER LIGHT

The amber SPOILER light, located on the glareshield annunciatorpanel, will illuminate steady whenever the flaps are UP and the spoil-ers are extended . The light will flash if the spoilers are extended andthe flaps are beyond 3° . The light is operated by a 1°-up positionswitch for each spoiler. The light will illuminate if either 1°-up switchis actuated .

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WARNING SYSTEMSSTALL WARNING SYSTEM

A stall warning system is installed to provide the crew with visualand tactile warning of an impending stall. The major components ofthe stall warning system consist of the following: left and right stallvanes on the forward fuselage, a two-channel computer-amplifier,shaker interrupt box, flap position switches for each flap, a stick shak-er for each crew position, an angle-of-attack indicator for each crewposition, L and R STALL warning lights, and associated aircraft wir-ing. The flap position switches provide bias information to the com-puter-amplifier which will decrease stall indication speeds as theflaps go from 0° to 40°. Above approximately 22,500 feet pressure alti-tude, a signal from the air data computers will bias the system to in-crease stall indication speeds approximately 15 knots. The stick shak-ers are eccentric weights driven by an electric motor and actuation isevidenced by a high-frequency vibration of the control columns. Theleft and right systems are completely independent and utilize separ-ate electronics, stall vanes, altitude bias signals, shaker motors, andflap switches . The stall warning system operates on 28 VDC suppliedthrough the 5-amp L and R STALL WARN circuit breakers on the pi-lot's and copilot's circuit breaker panels respectively . The stall warn-ing system is operative during EMER BUS mode. The stick shakerand STALL warning light circuits are wired through the shaker inter-rupt box and squat switches; therefore, the stick shaker and STALLwarning lights are deactivated when the squat switches are in theground mode. The stick shaker and STALL warning lights will be de-activated for 3 to 5 seconds after lift-off. The angle-of-attack indicatorsremain active both on the ground and inflight . The stall warning sys-tems may be tested on the ground using the rotary-type systems testswitch, located on the pilot's instrument panel. The stall vanes areheated to provide anti-ice protection during flight (Refer to PITOT-STATIC AND STALL WARNING ANTI-ICE, Section VI).

During flight, the stall warning vanes align with the local airstreamand transducers produce a voltage proportional to airplane angle ofattack . The transducer signals are transmitted to the appropriate com-puter-amplifier channel along with flap position information from theflap position switches and altitude information from the air data com-puters . The angle-of-attack indicator pointers will enter the yellowsegment, the L and R STALL lights will illuminate and flash, and thestick shakers will actuate when the angle of attack increases to an an-gle corresponding to an airspeed at least 7% above the stall speedpublished in the Airplane Flight Manual.

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LEFTSHAKER

LEFT STARANNUNCIATOR

AUTOPILOT/SHAKER INTEFFACE

ADC z

STALL WARNING SYSTEM BLOCK DIAGRAMFigure 5-2

RKaHTSHAKER

RK;HTSTALLANNUNCIATOR

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ANGLE-OF-ATTACK INDICATORS

The angle-of-attack indicators, located on the pilot's and copilot's in-strument panels, translate signals from the stall warning computer-amplifier into visual indication of stall margin . The left stall warningsystem utilizes the pilot's angle-of-attack indicator and the right stallwarning system utilizes the copilot's angle-of-attack indicator . Eachindicator face is divided into three segments as follows: green - safe,yellow - caution/shaker, and red - danger.

STALL WARNING LIGHTS

Thered L and R STALL warning lights, located in the glareshield an-nunciator panel, are installed to indicate impending stall or a systemmalfunction. During flight operations, the lights will illuminate andflash when the shaker is actuated. The lights are pulsed at the samefrequency and duration as the shakers; therefore, the flash durationwill increase as the angle-of-attack increases from initial shaker actua-tion . At or just prior to the angle-of-attack pointer entering the redsegment, the flash duration is sufficient to cause the lights to appearsteady.

SYSTEM TEST SWITCH - STALL WARNING FUNCTION

The rotary-type system test switch, located on the pilot's instrumentpanel, is used to test the left and right stall warning systems. Eachsystem is individually tested through the L STALL and R STALL po-sitions of the system test switch. The test is initiated by rotating thesystem test switch to L or RSTALL (as applicable) and then depress-ing the switch PRESS TEST button. When the test sequence is initiat-ed, the corresponding angle-of-attack indicator pointer will begin tosweep from the green segment toward the red segment. As the point-er passes the green-yellow margin, the stick-shaker will actuate, theMSTR WARN lights will illuminate, and the applicable STALL lightwill begin to flash. Shaker actuation is made evident by high frequen-cy vibration of the control column.

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OVERSPEED WARNINGSYSTEM

The overspeed warning system provides an audible overspeed warn-ing in the event aircraft speed exceeds a Mach or airspeed limit. Theoverspeed warning hom is activated by the air data computers whenthe position of the airspeed pointer and the maximum allowablepointer (barber pole) coincide. 28 VDC for system circuits is suppliedthrough the 5-amp WARN HORNS circuit breaker on the copilot'scircuit breaker panel. The overspeed warning horn is operative dur-ing EMER BUS mode. The overspeed warning horn will sound underany of the following conditions :1. Airspeed exceeds VMO.2. Mach exceeds MMO.NOTE: When Mach trim is inoperative and autopilots are disen-

gaged, themaximum allowable pointers will reposition to re-flect the reduced MMO for this condition.

SYSTEM TEST SWITCH - OVERSPEED WARNING FUNCTION

The rotary-type system test switch, located on the pilot's instrumentpanel, is used to test the overspeed warning system. The test se-quence is initiated by rotating the system test switch to ADC and thendepressing the switch PRESS TEST button. When the test sequence isinitiated, the pilot's air data system will test and the overspeed warn-ing horn will sound, then the copilot's air data system will test andthe overspeed warning hom will sound. Refer the Bendix/King KFC3100 Flight Control System Pilot's Guide for a detailed explanation ofthe air data system self-test .

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TRAFFICALERTAND COLLISION AVOIDANCE SYSTEM (TCAS-1)(OPTIONAL)

TheTCAS-I system provides the crew with aural andvisual indicationsof potentially dangerous flight paths relative to other aircraft in the vi-cinity. The system interrogates other transponder-equipped aircraftand determines their bearing, range, and relative altitude if the intrud-er has altitude encoding transponder in operation . With this informa-tion theWASprocessor can generate aural and visual advisories to thecrew.

The TCAS-I system consists of a processor, TPR/TCAS control unit,twobearing antennas, aTCAS ONLY display on theMFD(selectable bythe WD control panel), remote TCAS status annunciator and associat-ed aircraft wiring. System control is through the TPR/TCAS controlunit. Power for the system operation is 28 VDCsupplied through the 5-amp WAScircuit breaker on the copilot's circuit breaker panel.

Advisories are issued to the crew via the aircraft audio system, theMFD, and a remote annunciator located above the MFD. Aural adviso-ries generated by the ground proximity/windshear warningsystem (ifinstalled) will have priority over aural advisories generated by theWAS-1.

Refer to the applicable AFM supplement and Bendix/King Pilot'sGuides for further details and operating instructions.

TRAFFIC ALERTAND COLLISION AVOIDANCE SYSTEM (TCAS-10(OPTIONAL)

The TCAS-II system provides the crew with aural and visual indica-tions of potentially dangerous flight paths relative to other aircraft inthe vicinity. The system interrogates other transponder-equipped air-craft and determines their bearing, range, and altitude . With this infor-mation the WAS processor can generate Traffic Advisories (TA) andResolution Advisories (RA) to prevent or correct traffic conflicts.

The TCAS-II system consists of a processor, TPR/TCAS control unit,twobearing antennas, remote WAS status annunciator and associatedaircraft wiring. System control is through the TPR/TCAS control unit.Power for the system operation is 28 VDCsupplied through the 5-ampWAS circuit breaker on the copilot's circuit breaker panel.

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Advisories are issued to the crew via the aircraft audio system, theMFD, the pilot andcopilot altitude/vertical speed indicators, anda re-mote annunciator located above the MFD. Aural advisories generatedby the ground proximity/windshear warningsystem (if installed) willhave priority over aural advisories generated by the TCAS-II.

Refer to the applicable AFM supplement and Bendix/King Pilot'sGuides for further details and operating instructions .

GROUND PROXIMITY WARNING SYSTEM WITH WINDSHEARWARNING (GPWS) (OPTIONAL)

The MK-VII Warning System (GPWS/WS) provides the pilot with au-ral and visual warning of potentially dangerous flight paths relative toground and windshear conditions.

The system automatically and continuously monitors the airplane'sflight path with respect to terrain when the aircraft is below 2450 feetradio altitude (altitude AGL). If the airplane's projected flight pathwould imminently result in terrain impact, the system issues appropri-ate visual and voice warnings. Warnings are issued for excessive sinkrate, excessive terrain closure rate, descent after takeoff or missed ap-proach, proximity to terrain with flaps and/or gear up, descent belowglideslope, and descent below decision height (DH).

The system computes windshear and alerts the crew of windshear ofsufficient magnitude to be hazardous to the aircraft. Windshear alertsare given for increasing headwind/decreasing tailwind and/or up-draft. Windshear warnings are given for decreasing headwind/in-creasing tailwind and/or down-draft.

The system consists of the GPWS computer, a biaxial accelerometer, aset of annunciator light/switches on the instrument panel at each crewposition, "FAIL" annunciators on the center instrument panel, a flapposition override switch, and associated aircraft wiring . Voice warn-ings are made through the cockpit speakers and the headphones. Thesystem receives inputs from the #1 air data computer, #1 AHRS,Lstallwarning vane, radio altimeter, #1 nav receiver (G/S), nose gear downand locked switch, and the left flap 13° and 25° switch . Thesystem op-erates on 115 VAC supplied through the 1-amp GPWS/WNDSHR cir-cuit breaker on the pilot's circuit breaker panel.

Refer to the applicable AFM supplement for further details and operat-ing instructions .

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ENHANCED GROUND PROXIMITY WARNING SYSTEM WITHWINDSHEAR WARNING (EGPWS) (OPTIONAL)

The AlliedSignal Enhanced Ground Proximity Warning System(EGPWS) provides the pilot with aural and visual warnings of possibleterrain (or obstacle) proximity, excessive deviation below ILS glides-lope, and for detection of severe windshear conditions. The EGPWSalso provides aural alerts for descent below pre-defined altitudes dur-ing final approach, including a minimum descent altitude awarenesscallout and excessive bank angle alerting .

The EGPWS extends the Ground Proximity Warning (including Alti-tude Awareness Callouts and Bank Angle Alerting) and Windshear De-tection functionality of previous GPWS systems by adding Terrain (orObstacle) Awareness Alerting and Display (TAAD) (including "PeaksMode") and Terrain Clearance Floor (TCF) functions.

The system consists of : the EGPWS computer; a set of annunciatorlight/switches located on the instrument panel at each crew position; aflap override switch, an inhibit terrain switch, an inhibit glideslopeswitch and a test switch (all located in the pedestal); terrain not avail-able, TCAS fail, TCAS standby annunciators and terrain display onswitch (all located on the center instrument panel); and the associatedaircraft wiring. Voice warnings are made through the cockpit speakersand the headphones. Voice warnings generated by the EGPWS willhave priority over voice warnings generated by the TCAS (if installed).Terrain data may be displayed on the MFD. The system receives inputsfrom ADC, AHRS, stall warningvane, NAV receiver, the FMS, the radioaltimeter, the nose gear down and locked switch, and the left flap 13°and 25° switches . The system operates on 28 VDC supplied through the5-amp GPWS/WNDSHR circuit breaker on the pilot's circuit breakerpanel.

Refer to the applicable AFM supplement for further details and operat-ing instructions .

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MACH TRIM SYSTEM

The Mach trim system provides automatic pitch trim in response toMach changes to increase longitudinal stability and counteract thecenter-of-lift movement at speeds above approximately 0.70 MI if theautopilot is disengaged or inoperative. The system consists of a com-puter, a trim followup, MACHTRIM annunciatorand associated air-craft wiring. The Mach trim system utilizes the primary motor of thehorizontal stabilizer pitch trim actuator to effect trim changes. TheMach trim computer operates on 115 VAC supplied through the l-amp MACHTRIM circuit breaker on the pilot's circuit breaker paneland 28 VDC supplied through the 20-amp primary pitch trim currentlimiter.During flight, with neither autopilot engaged, the Mach trim systemwill automatically engage at approximately 0.70 MI. As the aircraftMach number changes, the change is sensed by the air data comput-ers and transmitted to the Mach trim computer . If the aircraft is notretrimmed to compensate for the Mach change, the Mach trim com-puter will command the appropriate pitch trim change (nose up forincreased Mach and nose down for decreased Mach ) through the hor-izontal stabilizer pitch trim actuator. A followup on the horizontalstabilizer will transmit a horizontal stabilizer position signal to theMach trim computer. Stabilizer trim motion will cease as the followupstabilizer position signal cancels the pitch trim signal from the Machtrim computer. A monitor is installed to disengage Mach trim in theevent of a malfunction. If the monitor disengages Mach trim andMach is above 0.78 My the overspeed warning horn will sound. TheMach trim system is resynchronized whenever either pilot manuallytrims the aircraft and a synchronous standby mode is maintained ifthe autopilot is engage. In flight, synchronization mayalso be accom-plished through the system test switch on the pilot's instrumentpanel.

PITCH TRIM SELECTOR SWITCH - MACH TRIM FUNCTION

The Mach trim system utilizes the primary motor of the horizontalstabilizer pitch trim actuator to increase longitudinal stability . If thePITCH TRIM selector switch on the pedestal is in the PRI position,Mach trim will automatically engage at approximately 0.70 MI if nei-ther autopilot is engaged. Mach trim will not engage or will disen-gage when the PITCH TRIM selector switch is moved to the OFF or

Pilot's Manual

Learjet 31A

SEC position. If the PITCH TRIM selector switch is in OFFor SEC, theMach trim monitor will remain active and will illuminate the MACHTRIM light and cause the overspeed warning horn to sound above0.78 MI.

MACH TRIM LIGHTThe amberMACH TRIM annunciator light, located on the glareshieldannunciator panel, will illuminate whenever the Mach trim monitorhas disengaged the Mach trim system. Whenever the Mach trim sys-tem is disengaged and Mach is above 0.78 Mb the overspeed warninghorn will sound if neither autopilot is engaged. The Mach trim moni-tor continuously monitors input signals and power to the Mach trimcomputer. In the event of loss of power to the Mach trim computer orprimary pitch trim system, loss of input signals to the Mach trim com-puter, or a Mach/horizontal stabilizer position error, the Mach trimmonitor will disengage Mach trim and illuminate the MACH TRIMlight-

SYSTEM TEST SWITCH -MACH TRIM FUNCTONThe rotary-type system test switch, located on the pilot's instrumentpanel, is used to test the Mach trim system and the Mach trim moni-tor while the aircraft is on the ground . In flight, the switch may beused to resynchronize the system if the Mach trim monitor has disen-gaged the system. The test function is initiated by rotating the switchto MACH TRIM and then depressing the switch PRESS TEST button.When the aircraft is on the ground and the test sequence is initiated,the test switch inserts a signal that causes the horizontal stabilizer totrim in the nose-up direction. Since there is no corresponding air-speed change, theMach trim monitor senses aMach/horizontal stabi-lizer position error, disengages Mach trim, and illuminates theMACH TRIM light. In flight, depressing the PRESS TEST button willresynchronize the Mach trim system to the horizontal stabilizer posi-tion and Mach existing when the PRESS TESTbutton wasdepressed.

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PITCH TRIM SYSTEM

Pitch trim is accomplished by repositioning the horizontal stabilizerto the desired trim setting through actuation of the horizontal stabiliz-er pitch trim actuator. The actuator is a dual-motor, screwjack-typeactuator. The primary motor is operated by the aircraft primary pitchtrim system. The secondary motor is operated by the aircraft secon-dary pitch trim system and the autopilot. A speed controller in theprimary pitch trim system changes primary pitch trim rate as a func-tion of flap position . The speed controller allows high trim rates whenthe flaps are beyond 3° down and low trim rates when the flaps areup. A trim speed monitor is incorporated into the speed controller toalert the crew of a trim speed error. Theprimary and secondary pitchtrim systems are electrically independent and mode selection is madethrough a selector switch . Primary pitch trim is pilot controlledthrough trim switches on each control wheel. Secondary pitch trim ispilot controlled through a switch on the pedestal . Emergency inter-rupt is provided for both systems through the Control Wheel Masterswitches (MSW). Horizontal stabilizer trim position is displayed on apedestal mounted indicator . Primary pitch trim control circuits oper-ate on 28 VDC supplied through the 3-amp PRI PITCH TRIM circuitbreaker on the pilot's circuit breaker panel. The primary motor oper-ates on 28 VDC supplied through a 20-amp current limiter. Secondarypitch trim control circuits and actuator motoroperate on 28 VDCsup-plied through the 75-amp SEC PrICH TRIM circuit breaker on thecopilot's circuit breaker panel. Primary and secondary pitch trim areoperative during EMERBUSmode.

PITCHTRIM SELECTOR SWITCH

ThePITCHTRIM selector switch, located on the pedestal trim controlpanel, provides primary and secondary mode selection for the pitchtrim systems. The switch has three positions: PRI, OFF, and SEC.When the switch is set to PRI, a ground path is provided for the pri-mary pitch trim system control circuits and trim changes are accom-plished through the control wheel trim switches. When the switch isset to SEC, a ground path is provided for the secondary pitch trimsystem control circuits and trim changes are accomplished throughthe pedestal NOSE DNOFFNOSE UP switch. When the switch is setto the OFFposition, both pitch trim electrical control circuits are iso-lated from the aircraft electrical system . The autopilot is inoperativewith thePITCHTRIM selector switch in theOFFposition .

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CONTROL WHEEL TRIM SWITCHES - PITCH FUNCTION

Each control wheel trim switch is a dual-function (trim and trim arm-ing) switch which controls primary pitch trim and roll trim. Oneswitch is located on the outboard horn of each control wheel . Eachswitch has four positions: LWD, RWD, NOSE UP, and NOSE DOWN.The trim arming button on top of the switch must be depressed fortrim motion to occur. With the PITCH TRIM selector switch in thePRI position, actuation of either switch to NOSE UP or NOSE DOWNwill signal the primary motor in the horizontal stabilizer pitch trimactuator to move the stabilizer in the appropriate direction. Actuationof the pilots switch will override actuation of the copilot's switch. Ac-tuation of either switch to any of the four positions (LWD, RWD,NOSE UP, or NOSE DOWN) with the trim arming button depressedwill disengage the autopilot if an autopilot CWS switch is not de-pressed.

PEDESTAL NOSE DN-OFF-NOSE UP SWITCH

The NOSE DN-OFFNOSE UP switch, located on the pedestal trimcontrol panel, controls secondary pitch trim. The switch is springloaded to the center (OFF) position. With the PITCH TRIM selectorswitch in the SEC position, actuation of the NOSE DNOFFNOSE UPswitch to NOSE DN or NOSE UP will signal the secondary motor ofthe horizontal stabilizer pitch trim actuator to move the stabilizer inthe appropriate direction. Actuation of the secondary pitch trimswitch will disengage the autopilot. With the PITCH TRIM SelectorSwitch in the PRI or OFF position, this switch has no trimming effect.

CONTROL WHEEL MASTER SWITCHES - PITCH TRIM FUNCTION

A Control Wheel Master Switch (MSW) is located beneath the controlwheel trim switch on the outboard horn of each control wheel . In ad-dition to the switch's other functions, either Control Wheel MasterSwitch (MSW), when depressed, will inhibit primary or secondarypitch trim. If the Control Wheel Master Switch (MSW) is used to in-hibit primary pitch trim, primary pitch trim will riot resume until theControl Wheel Master Switch (MSW) is released and the trim input isremoved. Therefore, during the preflight check of the primary pitchtrim system, it is necessary to release the control wheel trim switch aswell as the Control Wheel Master Switch (MSW) to reset the system.Secondary pitch trim, however, will be inhibited only as long as theControl Wheel Master Switch (MSW) is held.

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3°FLAPSWITCH

CONTROL WHEELMASTER SWITCH

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PM-121Original

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PITCH TRIM SYSTEM BLOCK DIAGRAMFigure 5-3

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5-13

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II

Pilot's Manual

Learjet 31A

PITCH TRIM LIGHT

An amber PITCH TRIM annunciator light, located on the glareshieldannunciator panel, is installed to alert the crew of primary pitch trimsystem malfunctions during flight. Additionally, the PITCH TRIMlight will illuminate whenever either Control Wheel Master Switch(MSW) is depressed.

T.O. TRIM LIGHT

An amberT.O. TRIM annunciator light, located on the glareshield an-nunciator panel, is installed to alert the crew that the PITCHTRIM in-dicator pointer is not within the T.O . segment when the aircraft is onthe ground. The light will be extinguished whenever the indicatorpointer is set within the T.O. segment. The light is disabled duringflight operations.

SYSTEM TEST SWITCH -TRIM MONITOR FUNCTION

The rotary-type system test switch, located on the pilot's instrumentpanel, is used to test the trim system monitor. The monitor is testedby rotating the system test switch to TRIM MON and depressing theswitch PRESS TEST button. When the PRESS TEST button is de-pressed, a signal simulating an electrical ground fault to the pitchtrim actuator is applied to the trim monitor and the monitor will illu-minate the PITCHTRIM light.

SYSTEM TEST SWITCH -TRIM OVERSPEED FUNCTION

The rotary-type system test switch, located on the pilot's instrumentpanel, is used to test the trim speed monitor. The monitor test is ini-tiated by rotating the system test switch to TRIM OVRSPD, initiatingprimary pitch trim through either control wheel trim switch, and thendepressing the switch PRESS TEST button. When the PRESS TESTbutton is depressed, a flaps down signal is applied to the trim speedcontroller and a flaps up signal is applied to the trim speed monitorsimulating the high trim rate with the trim speed monitor in the lowtrim rate mode . This will cause the trim speed monitor to illuminatethePITCHTRIM light.

PITCH TRIM INDICATOR

Horizontal stabilizer position is indicated by thePITCHTRIM indica-tor located in the trim indicator panel on the pedestal . The indicatorface has markings for 2° to 11° of horizontal stabilizer travel; howev-er, only the T.O. range markings are labeled. N DN and NUP mark-

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ings indicate the direction of trim travel for airplane nose down andairplane nose up respectively. The T.O. (takeoff) segment is markedfrom 5.75° to 8.75° . The indicator receives horizontal stabilizer posi-tion inputs from a potentiometer installed in the horizontal stabilizerpitch trim actuator . The indicator operates on 28 VDC suppliedthrough the 2-amp TRIM-FLAP IND circuit breaker on the copilot'scircuit breaker panel.

TRIM-IN-MOTION AUDIO CLICKER

A trim-in-motion audio clicker system is installed to alert the crew ofhorizontal stabilizer movement . The system will annunciate continu-ous movement of the horizontal stabilizer by producing a series ofaudible clicks through the headsets and cockpit speakers . The systemconsists of a potentiometer in the horizontal stabilizer pitch trim actu-ator, a trim-in-motion detector box, and associated aircraft wiring. Asthe horizontal stabilizer actuator drives the stabilizer, the output sig-nal from the potentiometer is altered. The change in potentiometersignal is sensed by the detector box. After approximately 1/4 secondof continuous stabilizer movement, the detector box will produce thespeaker and headset clicks. The trim-in-motion audio clicker systemis wired through the flap position switches and will not sound if theflaps are lowered beyond 3° . The trim-in-motion audio clicker may ormay not sound during mach trim or autopilot trim due to the dura-tion of the trim inputs . Power for system operation is 28 VDC derivedfrom the 5-amp WARN HORNS circuit breaker on the copilot's circuitbreaker panel.

ROLL TRIM SYSTEM

Roll trim is accomplished by positioning the aileron trim tab on theinboard trailing edge of the left aileron through actuation of the rolltrim actuator. The roll trim actuator is an electrically-operated, rotary-type actuator connected to the aileron trim tab by a push-pull rod.The system is controlled through the pilot's and copilot's controlwheel trim switches. Trim tab position information is displayed on apedestal mounted indicator. The roll trim system operates on 28 VDCsupplied through the 7.5-amp ROLL TRIM circuit breaker on the pi-lot's circuit breaker panel.

CONTROL WHEEL TRIM SWITCHES -ROLL FUNCTION

Each control wheel trim switch is a dual-function (trim and trim arm-ing) switch which controls roll trim and primary pitch trim. Oneswitch is located on the outboard horn of each control wheel. Eachswitch has four positions: LWD, RWD, NOSE UP, and NOSE DN. The

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arming button on top of the switch must be depressed for trim mo-tion to occur . Actuation of either control wheel trim switch to LWD orRWD will signal the aileron trim tab actuator to move the tab as re-quired to lower the appropriate wing. Actuation of the pilot's switchwill override actuation of the copilot's switch. Actuation of eitherswitch to any of the four positions (LWD, RWD, NOSE UP, or NOSEDN) with the trim arming button depressed will disengage the auto-pilot if an autopilot CWS switch is not depressed.

AILERON TRIM INDICATOR

Aileron trim tab position indication is provided by the AIL TRIM in-dicator located in the trim indicator panel on the pedestal . Two semi-circular scales and pointers present the trim tab position in terms ofLWD (left wing down) and RWD (right wing down). The scale mark-ings represent increments of trim tab travel. The indicator receivesaileron trim tab position inputs from a potentiometer in the roll trimactuator. The indicator operates on 28 VDC supplied through the t-amp TRIM-FLAP IND circuit breaker on the copilot's circuit breakerpanel.

TRIM INDICATOR PANELFigure 5-4

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YAWTRIM SYSTEM

Yaw trim is accomplished by positioning the rudder trim tab on thelower trailing edge of the rudder through actuation of the yaw trimactuator . The yaw trim actuator is an electrically-operated, rotary-type actuator connected to the rudder trim tab by a push-pull rod.Yaw trim is pilot controlled through the RUDDER TRIM switch onthe pedestal. Trim tab position information is displayed on a pedestalmounted indicator. The yaw trim system operates on 28 VDC sup-plied through the 7.5-amp YAW TRIM circuit breaker on the pilot'scircuit breaker panel.

RUDDER TRIM SWRCH

Yaw trim is pilot controlled through the RUDDER TRIM switch locat-ed on the pedestal trim control panel. The switch has three positions:NOSE LEFT, OFF, and NOSE RIGHT. The switch knob is split andboth halves must be rotated simultaneously to initiate yaw trim mo-tion . When the switch is released, both halves will return to the centerOFFposition. Actuation of theRUDDER TRIM switch to NOSE LEFTor NOSE RIGHT will signal the yawtrim actuator to move the ruddertrim tab in the appropriate direction.

PEDESTAL TRIM CONTROL PANELFigure 5-5

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RUDDER TRIM INDICATOR

Rudder trim tab position indication is provided by the RUDDERTRIM indicator located in the trim indicator panel on the pedestal . Asemi-circular scale and pointer indicates the direction (L or R) of yawtrim. The scale markings represent increments of rudder trim tab trav-el . The indicator receives rudder trim tab position inputs from a po-tentiometer in the rudder trim actuator. The indicator operates on 28VDC supplied through the 2-ampTRIM-FLAP IND circuit breaker onthe copilot's circuit breaker panel.

AUTOPILOT/FLIGHT DIRECTOR SYSTEM

The Bendix/King KFC 3100 Flight Control System is installed to pro-vide automatic flight control and/or flight guidance for climb, cruise,descent and approach. The system is fully integrated with the air-craft's air data system, attitude heading reference system (AHRS),and electronic flight instrument system (EFIS) . The system's dualflight computers provide separate pilot and copilot flight guidance inthe pitch and roll axes . Either pilot's or copilot's flight guidance steer-ing commands may be coupled to the autopilot . Pitch and roll axischange, when commandedby the autopilot, is effected through eleva-tor and aileron servos. The autopilot also provides pitch trim com-mands to the secondary trim system motorof the horizontal stabilizerpitch trim actuator. The system's pitch authority is limited to 10° nosedown and 20° nose up and roll authority is limited to 25° bank. Theautopilot controller, located on the glareshield, provides for engage-ment, mode selection and status annunciation. Pilot inputs to theflight control system are accomplished through the autopilot control-ler, control wheel switches, Altitude/Vertical Speed Indicator, andthe EFIS controls . The pilot's autopilot/flight guidance system oper-ates on 28 VDC supplied through the 5-amp AP 1, and 5-amp FLTDIR 1 circuit breakers, and 115 VAC supplied through the 1-amp AP1 MON circuit breaker on the pilot's circuit breaker panel. The copi-lot's autopilot/ flight guidance system operates on 28 VDC suppliedthrough the 5-amp AP 2, and 5-amp FLT DIR 2 circuit breakers and115 VAC supplied through the 1-amp AP 2 MON circuit breaker onthe copilot's circuit breaker panel. Yaw damper and rudder boost sys-tems are also integrated into the KFC 3100 Flight Control System . Re-fer to YAW DAMPER SYSTEM and RUDDER BOOSTSYSTEM.

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The system initiates a self-test sequence when the system is poweredup (both AC and DC power) . If the self-test sequence is not success-fully completed, a failure will be displayed on the autopilot controllerand the autopilot will not engage. Also, an "FD" flag will be dis-played on the EADI. Flight guidance steering commands are present-ed on the EADI displays. The pilot may manually fly the airplane tosatisfy the steering commands (flight director only operation) orcouple the flight guidance system to the autopilot in which case theautopilot will respond to the steering commands.

When the autopilot isengaged andthe stick shaker actuates, the auto-pilot will disengage. Stick shaker has no effect on flight director oper-ation.

AUTOPILOTCONTROLLER

The autopilot controller provides the autopilot and yaw damper en-gage function, as well as autopilot/flight director mode selection andannunciation. The controller is divided into three sections with thecenter section providing autopilot/yaw damper selection and engagebuttons as well as status annunciation. The section on the left sideprovides mode selection for the pilot's flight guidance system and thesection on the right side provides mode selection for the copilot'sflight guidance system. The autopilot controller is located in the cen-ter of the glareshield and is easily accessible from either crew posi-tion. The controller lights can be dimmed through the pilot's INSTRdimmer switch on the pilot's dimmer panel.

I,~ ___) lJ.; P Y~ a P

i ao o " as

ae ao?-)

=IC I=2

J~1

171

AUTOPILOTCONTROLLERFigure S-6

Pilot's Manual

Learjet 31A

AUTOPILOT/YAW DAMPER ENGAGE FUNCTIONS

AP -TheAP pushbutton alternately engages and disengages the au-topilot. Pressing this button will couple the autopilot to the selectedflight guidance system provided the self test has successfully beencompleted. A green light above the AP button will illuminate when-ever the autopilot is engaged. Engaging the autopilot will also engagetheyawdamper and flight director if not already engaged.

XFR - The XFR pushbutton alternately selects between the pilot'sand copilot's flight guidance computer for the source of autopilotcommands. Agreen arrow, on the controller, will will indicate the se-lected flight guidance computer .

SOFT RIDE-TheSOFT RIDE pushbutton is used to select the auto-pilot soft ride mode. When operating in soft ride mode, the autopilotreacts more slowly to commands thus giving a smoother ride. Softride is available whenever the autopilot is engaged and ApproachCapture mode is not active. A green light above the SOFT RIDE but-ton will illuminate whenever the soft ride mode is engaged.

YD - The YD pushbutton alternately engages and disengages theyaw damper independently of autopilot operation. A green lightabove theYD button will illuminate whenever theyaw damper is en-gaged-

AUTOPILOT/FUGHT DIRECTOR MODES

Autopilot and flight director modes are engaged by depressing theapplicable mode selector button on the autopilot controller. A greenlight above each selector button will illuminate when that particularmode is selected. Flight director only mode selection is accomplishedby depressing the applicable mode selector without the autopilot en-gaged-

Engaged autopilot and flight director modesmaybe cancelled by de-pressing the selector button a second time or selecting an incompati-ble mode.

Refer to the Bendix/King KFC 3100 Flight Control System Pilot'sGuide (No. 006-)8486-0000) for a detailed description and operationof the autopilot/flight director modes.

Learjet 31A

Pilot's Manual

Attitude Hold-When the flight director is operating and no verticalmode is selected, pitch attitude hold will automatically be active.When the flight director is operating and no lateral mode is selected,roll attitude hold will automatically be active . These modes are usedto maintain a reference pitch and bank angle . The reference anglesmay be established by manually flying the aircraft to the desired pitchand bank angle while depressing the CWS switch (on the controlwheel) . When the CWS switch is released, the flight director will gen-erate commands to maintain the existing pitch and roll attitude. Thereference values may be changed using the vertical and lateral com-mand function of the control wheel trim switches.

HDG (heading) - When HDG is selected, commands are generatedto maneuver the airplane as necessary to fly a heading selected by po-sition of the heading "bug" on the EHSI.

HALF BANK -WhenHALFBANK is selected, the KFC 3100 controlsystem reduces its maximum roll attitude command to one-half of thenormal limit. HALF BANK may be engaged in conjunction with anylateral mode except Approach.

NAV (navigation) - The NAV mode provides commands to captureand track the navigational course selected on the EHSI.

APR (approach) - The APR mode provides commands to captureand track the navigational course selected on the EHSI with approachaccuracy . During ILS front course approaches, commands to captureand track the glideslope will be generated after the Iocalizer has beencaptured.

ALT SEL (altitude select) - The ALT SEL mode provides commandsto capture and track the selected altitude shown in the altitude prese-lect window on the altitude/vertical speed indicator .

ALT HOLD (altitude hold) - The ALT HOLD mode provides com-mands to track the indicated altitude present at the time of mode en-gagement. The reference altitude may be changed using the verticalcommand function of the control wheel trim switches. If ALT SELmode is used to capture an altitude, the ALT HOLD mode will auto-matically engage after the selected altitude has been captured .

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CLB (climb) - The CLB mode provides commands to maintain apreset speed versus altitude profile. Two climb profiles (Normal andHigh Speed) have been programmed into the KFC 3100 system. Thevertical command function of the control wheel trim switches is usedto select the desired climb profile. Engaging the CLB mode will alsoactivate the ALT SEL mode if the preselected altitude is higher thanthe aircraft's present altitude .

DES (descend) -The DES mode provides commands to maintain apreset speed versus altitude profile. Two descent profiles (Normaland High Speed) have been programmed into the IBC 3100 system.The vertical command function o¬ the control wheel trim switches isused to select the desired descent profile. Engaging the DES modewill also activate the ALTSEL mode if the preselected altitude is low-er than the aircraft's present altitude.

MACH (Mach hold) - The MACH mode provides commands tomaintain the indicated Mach number present at the time of mode en-gagement. The reference Mach number may be changed using thevertical command function of the control wheel trim switches .

1AS (indicated airspeed hold) -The IAS mode provides commandsto maintain the indicated airspeed present at the time of mode en-gagement. The reference airspeed may be changed using the verticalcommand function of the control wheel trim switches_

VNAV (vertical navigation) - The VNAV mode provides com-mands to capture and track a vertical track angle as defined by a com-patible flight management system with vertical navigation capability.

VS (vertical speed hold) - The VS mode provides commands tomaintain the vertical speed selected on the altitude/vertical speed in-dicator. In the absence of a preselected vertical speed, flight directorcommands will be generated to maintain the vertical speed present atthe time of mode engagement. The reference vertical speed may bechanged using the vertical command function of the control wheeltrim switches or the VS select knob on the altitude/vertical speed in-dicator.

Go-Around- Go-Around is a flight director only mode . Depressingthe GO-AROUND button on the left thrust lever knob disengages theautopilot (if engaged) and commands both flight directors to 9° pitchup and wings level attitude.

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STATUS ANNUNCIATORS

The autopilot controller incorporates two identical sets of annuncia-tors to provide the status of the left and right autopilot systems. Addi-tionally, two rudder boost (RB) annunciatoos are installed to providethe status of the rudder boost system.

R (Roll Axis) -A steady amber R annunciation indicates a roll axisfailure. A flashing amber Rannunciation indicates a roll mistrim con-dition .

P (Pitch Axis)-A steady amberP annunciation indicates a pitch axisfailure. A flashing amber P annunciation indicates a pitch mistrimcondition.

Y (Yaw Axis)-A steady amber Y annunciation indicates a yaw axisfailure.

AP (Autopilot) -A red AP annunciation indicates an autopilot fail-ure. The red AP annunciation will accompany any steady annuncia-tion of R, P or Y.

PT (Pitch Trim) - A red PT annunciation indicates a pitch trimfailure.

RB (Rudder Boost) -Two separate RB annunciators, one green andone amber, are installed. Illumination of the green RB annunciator in-dicates the rudder boost system is active . Illumination of the amberRB annunciator indicates arudder boost system failure.

Selected Flight Guidance Computer-Oneof twogreen arrows willilluminate and point to the flight guidance system, pilot or copilot,that the autopilot will use as a source of steering commands.

Learlet 31A

Pilot's Manual

CONTROL WHEEL MASTER SWATCHES - AUTOPILOT FUNCTION

The Control Wheel Master Switches (MSW), located on the outboardhorn of the pilot's and copilot's control wheels, may be used to disen-gage the autopilot . Depressing either the pilot's or copilot's ControlWheel Master Switch (MSW) will apply a signal whichcancels the au-topilot engage signal. When the autopilot disengages, the green lightabove theAP button will extinguish and the autopilot disengage tonewill sound. When the autopilot is disengaged using the ControlWheel Master Switches (MSW), the flight director will remain activeand will display steering information from the flight guidance com-

TRIM SELECTOR SWITCH - AUTOPILOT FUNCTION

When the autopilot is engaged, the autopilot maintains aircraft pitchtrim through the secondary motor of the horizontal stabilizer pitchtrim actuator if the PITCH TRIM selector switch on the pedestal is inthe PRI or SEC position. The autopilot will not engage or will disen-gage if the PITCHTRIM selector switch is moved to theOFF position.

CONTROL WHEEL SWITCHES(PILOTS SHOWN, COPILOTS OPPOSITE)

Figure 5-7

puter-PITCH

Original

Pilot's Manual

Lealet 31A

CONTROLWHEELTRIM SWITCHES-AUTOPILOT/FLIGHT DIRECTORFUNCTION

The control wheel trim switches, located on the outboard horn of eachcontrol wheel, may be used to disengage the autopilot, to make trimadjustments with the autopilot pitch and roll axes inhibited, to makevertical and lateral inputs while in certain modes and to toggle be-tween normal and high speed profiles while operating in CLBor DESmode. When either control wheel trim switch (arming button de-pressed) is moved to any of the four positions (LWD, RWD, NOSEUP, or NOSE DN) the autopilot will disengage, the green light abovethe AP button will extinguish and the autopilot disengage tone willsound. When the autopilot is disengaged using the control wheel trimswitches, the flight director will remain active and will display steer-ing information from the flight guidance computer. Control wheeltrim switches (arming button not depressed), may be used to insertvertical and lateral changes when ALTHOLD, MACH,VS,LAS, PitchAttitude Hold or Roll Attitude Hold are engaged. To make a verticalcommand input, the control wheel trim switch (arming button not de-pressed) is moved to NOSE UP or NOSE DN. To make a lateral com-mand input, the control wheel trim switch (arming button not de-pressed) is moved to LWD or RWD. When the autopilot is engaged,pitch and roll trim changes can be made by holding the CWS switchand using the control wheel trim switches as discussed in PITCHTRIM SYSTEM andROLL TRIM SYSTEM.

Vertical Command-In Pitch Attitude Hold, commands a change inthe aircraft's pitch attitude; In ALT HOLD, increases or decreases thereference altitude; In MACH, increases or decreases the referenceMach number; In VS, increases or decreases the reference verticalspeed, In IAS, increases or decreases the reference indicated airspeed;In CLB or DES, toggles between normal and high speed profiles. Ini-tiating vertical command while operating in the VNAV, GlideslopeCapture, Altitude Capture or Go-around mode will cancel thosemodesand the system will revert to Pitch Attitude Hold mode.

Lateral Command-In Roll Attitude Hold, commands a change inthe aircraft's roll attitude. Initiating lateral command while operatingin the HDG, NAV Capture or APR Capture mode will cancel thosemodes and the system will revert to Roll Attitude Hold mode.

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PEDESTAL NOSE DN-OFF-NOSE UP SWITCH - AUTOPILOTFUNCTION

The NOSE DN-OFFNOSE UP switch, located on the pedestal trimcontrol panel, maybe used to disengage the autopilot or to make trimadjustments with the autopilot pitch and roll axes inhibited. With thePITCH TRIM selector switch in theSEC position, actuation of secon-dary pitch trim through theNOSE DNOFFNOSE UP switch will dis-engage the autopilot, extinguish the green light above the AP button,and sound the autopilot disengage tone. When the autopilot is disen-gaged through the NOSE DNOFF-NOSE UP switch, the flight direc-tor will remain active and will display steering information from theflight guidance computer. When the autopilot pitch and roll axes areinhibited using the control wheel CWS switches, pitch trim changescan be made by using the NOSE DNOFF-NOSE UP switch as dis-cussed in PITCHTRIM SYSTEM.

CONTROL WHEEL STEERING (CWS) SWITCHES

Depressing the control wheel steering (CWS) switch, located on theinboard horn of each control wheel, uncouples the autopilot servoclutches, if engaged, and allows for flying the aircraft to a new refer-ence value in certain modes. Manual pitch, roll, and trim commandscan be made while the switch is depressed. When the switch is re-leased, the system will resynchronize to the existing (new) values inMACH, IAS, ALT HOLD, or Attitude Hold modes. If the flight direc-tor is not engaged, depressing the CWS switch activates the system inPitch and Roll Attitude Hold mode and synchronizes to the values ex-isting at the time of switch release. Depressing the CWS switch willcancel Go-aroundmode and activate Pitch Attitude Hold mode.

CONTROL WHEEL FD CLEAR SWITCHES

The FD CLEAR switches, located on the inboard horn of each controlwheel, are used to stow the on-side flight director command bars .

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SYSTEM TEST SWITCH -A/P RESET FUNCTION

The rotary-type system test switch, located on the pilot's instrumentpanel, is used to reset the autopilot in the event it disengages andcan-not be reengaged. The reset sequence is initiated by rotating the sys-tem test switch to A/P RESET and then depressing the switch PRESSTEST button. On the ground, both autopilots will test and servos willengage momentarily. In flight, only the selected autopilot will testandthe servos will not engage .

YAW DAMPER SYSTEM

The yaw damper augments aircraft stability by opposing uncom-manded motion about the yaw axis and provides turn coordination.The yaw damper is provided by the yaw axis of the KFC 3100 flightcontrol system. Theyaw damper operates independent of the autopi-lot.

YAWDAMPER CONTROL

The yaw damper button and annunciator are located in the autopilotcontroller, and provides yaw damper selection and indicating func-tions. Theyaw damper engages when the autopilot is engaged, or bydepressing the YD button on autopilot controller. When the yawdamper is engaged the green light above theYD button will be illumi-nated. If the yaw damper is already engaged, depressing theYD but-ton will disengage the yaw damper.

CONTROL WHEEL MASTER SWITCHES- YAW DAMPER FUNCTION

The Control Wheel Master Switches (MSW), located on the outboardhorn of the pilot's and copilot's control wheels, may be used to disen-gage the yaw damper. Depressing either the pilots or copilot's Con-trol Wheel Master Switch (MSW) will apply a signal which cancelstheyaw damper engage signal. When theyawdamper disengages thegreen light above the YD button will extinguish and theyaw damperdisengage tone will sound.

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l.earjet 31A

RUDDER BOOST SYSTEM

The rudder boost system is installed to provide reduced rudder pedalforce, increased directional control effectiveness and improved take-off performance. With the rudder boost on, minimum control speed-ground (VMCG), takeoff speeds and distances are all lower. The rud-der boost system consists of a computer, force sensors, flap positionswitch, RUDDER BOOST Switch, and associated aircraft wiring. Theyaw damper servo provides the "boost" to assist the pilot in movingthe rudder in the desired direction. The rudder boost system is sup-plied 28 VDC through the 7.5-amp RUDDER BOOST circuit breakeron the pilot's circuit breaker panel.Normally the RUDDER BOOSTSwitch, on the pilot's switch panel, isleft on at all times. Applying approximately 35 pounds of force to ei-ther rudder pedal will cause the yaw servo to automatically engageand apply force to the rudder in the same direction as the pilot. As pi-lot input force is increased, the servo force will also increase up to themaximum yaw servo force. The flap position switch is used to reducethe maximum servo force available when the flaps are up. When therudder boost engages, the green RB annunciator, on the autopilot con-troller, illuminates to indicate rudder boost is active. If the yawdamper is on when the rudder boost engages, the system will make asmooth transition from yaw damper to rudder boost. A failure of thesystem is indicated by illumination of the amber RB annunciator onthe autopilot controller . Self-test of the system is initiated during sys-tempower-up. Refer to the FAA Approved AFM for self-test and useof the rudder boost system .

RUDDER BOOST SWITCH

Pilot's Manual

Arming of the rudder boost system is controlled by the RUDDERBOOSTSwitch located on the pilot's switch panel. When the switch isset to ON, the system will be armed. Setting the switch to OFF willdisarm the system and the rudder control system will not be assistedby theyaw servo.

CONTROL WHEEL MASTER SWITCHES - RUDDER BOOST FUNCTION

TheControlWheel Master Switches (MSW), located on the outboardhorn of the pilot's and copilot's control wheels, may be used to inter-rupt operation of the rudder boost system . Depressing either the pi-lot's or copilot's Control Wheel Master Switch (MSW) will disable therudder boost system while the switch is held .

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Learjet 31A

RUDDERPEDALS

LH YAWFORCESENSOR

-------WMECHANICAL

-I" ELECTRICAL

GREEN &AMBERORB'

ANNUNCIATORS

RUDDER BOOST BLOCK DIAGRAMFigure 5-8

RUDDERPEDALS

RH YAWFORCESENSOR

RUDDER

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Pilot's Manual

ATTITUDE HEADING SYSTEM (AHS 1 AND AHS 2)

Aircraft avionics displays andequipment requiring attitude or headinginformation are supplied attitude and heading information from dual,independentAttitude HeadingReference Systems (AHS 1 and AHS 2).Each system consists of an attitude heading reference unit computer,magnetic slaving unit (flux valve), HEADING control switches, AHSannunciator light and associated aircraft wiring. The attitude headingreference unit computer is composed of inertial instruments, electron-ics, interface hardware, processing and memory circuits to provide at-titude andheading information to other aircraft systems. Onemagneticslaving unit is located in each wing tip and is used to sense the earth'smagnetic field. Themagnetic slaving unit can thus correct the AHS forprecession error. The HEADING SLAVE-FREE switch allows the crewto select either Free orSlaved Magnetic Headingmode. Thesystem hastwo operating modes, normal and basic. During normal operation, atrue airspeed input is supplied by the air data system to improveaccu-racy. If the true airspeed input is lost, the system will continue to oper-ate in the basic mode. AHS, operation is automatic and both systemswill energize when battery power is applied to the aircraft. Within 60seconds of power application, the system determines its orientationwith the local vertical andmagneticNorthand performs a series of self-test and calibration functions. TheAHS1 and 2systemsare powered by28 VDC, 7-5-ampAHS 1 andAHS2circuit breakers and26 VAC, 5-ampAHS 1 and 1-ampAHS 2circuit breakers located on the pilot's and co-pilot's circuit breaker panels . AHS 2 is operative during EMER BUSmode. In the event of a power loss, 2 to 11 minutes of back-up power(28 VDC) will be supplied to AHS 1 and AHS2by EMER BAT 2. Thisfeature makes it unnecessary to reinitialize the system should a mo-mentarypower loss be experienced. Should one of the systems fail, thefunctions of the failed system may be assumed by the remaining sys-tem using theAHS1/AHS 2reversionary mode. StandbyHSIheadingdata andweather radar antenna stabilization functions are provided byAHS2and cannot be assumed by AHS 1.Attitude/heading data is provided for the following using systems:

EFIS Displays -attitude andheading displaysAutopilot/Flight Director- attitude, heading and accelerationdataStandby HSI - heading display (heading data provided byAHS2 at all times)Weather Radar-pitch and roll data provided by AHS 2 forantenna stabilizationFlight Management System-heading data

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HEADING CONTROL SWITCHES

The HEADING control switches, located in the AVIONICS group onthe pilot's and copilot's switch panels, are used to control the headingoutput of the associated AHS. The switches on the pilot's side controlAHS 1 while the switches on the copilot's side control AHS 2. TheSLAVE-FREE switch provides slaving mode selection for the associatedAHSheading output. When the switch is set to SLAVE, the associatedAHSheadingoutput will be referenced to its magnetic slaving unit andthe associated compass cards will reflect this "slaved" alignment .When the switch isset toFREE, the associatedAHSheading output willnot be referenced to its magnetic slaving unit. The SLAVE L-R switchprovides for manual slewmg of the associated compass cards. Smallheading splits can usually be cleared by cycling the SLAVE-FREEswitch toFREE and thenback to SLAVEwhile theaircraft is not turningor accelerating.

AHS 1 ANDAHS 2 ANNUNCIATOR LIGHTS

On abrr* 31-035 thru 31-184, illumination of an amberAHS 1 or AHS2 light indicates a failure of the associated cooling fan in the attitudeheading reference unit computer. TheAHSwill continue to operate foraminimum of 30 minutes undernormal temperature conditions .

Onaim*l 31-185andsubsequent, the illumination of an amberAHS1 orAHS 2 light indicates a failure in the attitude heading reference unitcomputer. For a detailed list of failure modes, refer to theLITEF PilotsGuide, P/N 142185-0000-311, Revision 1 or later version.

AHS i/AHS 2 REVERSIONARY MODE

TheAHS 1/AHS 2 switches on the EFLS CONTROLpanels are used toselect the attitude heading system for the respective EFIS display andautopilot/flight director. On-sideAHSis thenormal selectionindicatedby a green annunciation on the switch. Reversionary (cross-side) selec-tion is indicated by an amber annunciation on the switch

Learjet 31A

Pilot's Manual

ELECTRONIC FLIGHT INSTRUMENTS SYSTEM (EFIS)

A Bendix/King 5-tube EFS 50 electronic flight instruments system isinstalled to display airplane attitude data, navigational data, flight di-rector command, mode annunciators, weather, checklist, warningsand diagnostic messages . The EFIS consists of an electronic attitudedirector indicator (EADI) and electronic horizontal situation indicator(EHSI) on both pilot's and copilot's instrument panels, a multifunc-tion display (MFD) on the center instrument panel, three symbol gen-erators (SG 1, SG 2 & SG 3), joystick (optional) and control panels tooperate the system. Cooling for the EFIS displays is provided by fansintegral to each display unit and two fans behind the instrument pan-el. Cooling for the symbol generators is provided by one fan on eachsymbol generator mounting rack. The pilot's displays are normallydriven by SG 1 and the copilot's displays are normally driven by SG2. Should SG 1 or SG 2 malfunction, SG 3 may be selected to assumethe functions of the failed unit . The WD is driven by SG 3. The sys-tem is powered by 28 VDC from the following circuit breakers: 7.5-amp EADI 1 & 2,5-amp EHSI 1 & 2,7.5-amp SG 1 EADI, SG 2 EADI&SG 3 EADI, 7.5-amp SG 1 EHSI, SG 2 EHSI&SG 3 EHSI, and 5-ampWD.

ELECTRONIC ATTITUDE DIRECTOR INDICATOR (EADI)

An EADI is installed at each crew position. Each EADI is a 5-inch,multicolor CRT display . An inclinometer is installed on the face ofeach EADI to provide slip and skid information. The EADIs providethe following information :

Pitch and Roll AttitudeMode AnnunciationsRadio Altitude & DH SetFast/Slow IndicationMarker BeaconRate-of-Turn (Optional)

Flight Director CommandsWarning Annunciations & FlagsGlideslope and Localizer DeviationVertical Navigation DeviationHeading

ELECTRONIC HORIZONTAL SITUATION INDICATOR (EHSI)

An EHSI is installed at each crew position Each EHSI is a 5-inch, mul-ticolor CRT display . The EHSIs provide the following information:

HeadingSource AnnunciationsCourse DeviationSelected HeadingBearing PointersWeather Radar

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DME DataWarning Annunciations & FlagsGlideslope and Localizer DeviationVertical Navigation DeviationSelected Course/Desired Track

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EFIS CONTROL PANELAn EFIS control panel is installed for both the pilot's and copilot's dis-plays . The control panels are located in the pedestal. Each panel con-trols the functions of the respective EFIS displays. Each panel pro-vides the following functions:

Decision Height SetEFIS TestDisplay FormatBearing Pointer SelectCourse SelectRange Select (weather andmap mode)

MULTIFUNCTION DISPLAY (MFD)

MFD CONTROLPANELSTANDARD (WITHOUT JOYSTICK)

EFIS TestDisplay FormatBearing Pointer SelectRange Select (weather andmap mode)

5- 32

Radio Altimeter TestDisplay BrightnessNavigation Source SelectHeading SelectGround Speed/Time to Station

Select

EFIS CONTROL PANELFigure 5-9

An MFD is installed in the center instrument panel. The NIFD is a 5-inch, multicolor CRT display. The MFD provides weather radar dis-play, FMS map display and functions as a third EHSI.

An MFD control panel is installed in the pedestal. The panel controlsthe functions of the multifunction display . The following functionsare provided:

Display BrightnessNavigation Source SelectCourse SelectGround Speed/Time to Station

Select

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(WITHOUT JOYSTICK)

OPTIONAL (WITH JOYSTICK)

(WITH JOYSTICK)MFD CONTROL PANEL

Figure 5-10

An MFD control panel is installed in the pedestal. The panel controlsthe functions of the multifunction display . The following functionsare provided :

DisplayFormatEFIS TestTCASONLY SelectChecklist SelectDisplay BrightnessCourse SelectNavigation Source Select

EFIS REVERSIONARY CONTROL PANEL

Bearing Pointer SelectRS 232 Communications Port(checklist programming)

Waypoint Position Entry (joystick)Range Select (weather and map mode)Ground Speed/Time to Station SelectEnter Select (waypoint coordinatetransfer)

An EFIS CONTROL panel is installed on both the pilot's and copilot'sinstrument panel. The panel controls the reversionary functions of theassociated EFIS display. The following reversionary functions are pro-vided:

AHS Select

ADC SelectSG Select

Composite/Display SelectSingle-cue/Double-cue

EADI Down SelectSelect

Refer to the FAA Approved AFM for a description and use of eachfunction.PM-121

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Learjet 31A

FLIGHT INSTRUMENTS

EFIS REVERSIONARY CONTROL PANELFigure 5-11

Flight instruments include airspeed/Mach indicators, altitude/vertical speed indicators, speed/temperature indicator, standby HSI,standby attitude gyro, standby airspeed indicator and standby altime-ter. Refer to Electronic Flight Instrument System, also .

AIRSPEED/MACH INDICATORSAn airspeed /Machindicator is installed on both the pilot's and copi-lot's instrument panel. Each indicator is a Bendix/King unit driven byelectrical signals from a remotely located air data computer. Featuresof the indicator include: circular scale graduated from 50 to 430 knots,airspeed pointer, maximum allowable pointer (barber pole), digitalKIAS/MACH display window, moveable Vref bug, moveable refer-ence airspeed bug and failure flag . Power for the indicators is 28 VDCsupplied through the I-ampPILOT A/S and CP A/S circuit breakers.The pilot's airspeed/Mach indicator is operative during EMER BUSmode.The airspeed pointer positions itself along the graduated scale to indi-cate the aircraft's airspeed in knots. The maximum allowable pointeraligns with the maximum allowable speed (VMO/MMO) for existingconditions (i .e. altitude and autopilot, and Mach trim status). The dig-ital display window displays speed in knots when Mach number isless than 0.50 MI, and in Mach when Mach number is greater than0.50 MI. AMACH annunciator illuminates when Mach number is dis-

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played. TheVref bug

nl is set by the crew with aknob on the face ofthe indicator. Differences between the Vref bug and actual airspeedwill be reflect by the fast/slow scale on the EFIS display. The refer-ence airspeed bug is set by the anew with aknob on the face of the in-dicator and is for reference purposes only. The failure flag will comeinto view when the airspeed data is invalid.

AIRSPEED/MACH INDICATORFigure 5-12

ALTRUDE/VERTICAL SPEED INDICATORS

An altitude/vertical speed indicator is installed on both the pilot'sand copilot's instrument panel. Each indicator is a Bendix/lung unitdriven by electrical signals from aremotely located air data computer.Features of the indicator include: circular altitude scale graduatedfrom 0 to 1000 feet in 20-foot increments, circular vertical speed scalegraduated from 0 to 6000 fe