AST 473 Cessna Citation II Landing Gear and Brakes Dr. R. Kurt Barnhart.

AST 473 Cessna Citation II AST 473 Cessna Citation II Landing Gear and BrakesLanding Gear and Brakes

Dr. R. Kurt BarnhartDr. R. Kurt Barnhart

Landing Gear and BrakesLanding Gear and Brakes

Electrically controlled- Hydraulically activatedElectrically controlled- Hydraulically activated Mechanically actuated doors cover nose gear and Mechanically actuated doors cover nose gear and

struts of main gear when retracted- main gear struts of main gear when retracted- main gear wheels uncovered in flightwheels uncovered in flight

Nosewheel steering- via mechanically linked Nosewheel steering- via mechanically linked rudder pedals- shimmy damp. Included- on top of rudder pedals- shimmy damp. Included- on top of nose strutnose strut

Braking- W/ or W/O anti-skid & pneumatic emerg. Braking- W/ or W/O anti-skid & pneumatic emerg. BrakingBraking

Indication- colored indicator lights & warn. hornIndication- colored indicator lights & warn. horn


Overview:Overview:– Each gear retracts inboard utilizing 2 hyd. Each gear retracts inboard utilizing 2 hyd.

Actuators ea.- one for uplock release and one Actuators ea.- one for uplock release and one for gear actuationfor gear actuation

– Nose gear- 2 identical actuators- retracts Nose gear- 2 identical actuators- retracts forwardforward

– Elec. Cnt’l valve directs hyd. Press. For gear Elec. Cnt’l valve directs hyd. Press. For gear actuationactuation


Indication:Indication:– One red and three green down/locked position One red and three green down/locked position

indicator lights plus warning horn whenindicator lights plus warning horn when Throttle or flap settings indicate lndg. But gear not Throttle or flap settings indicate lndg. But gear not

down & lockeddown & locked


Nose wheel- steering via a cable linkage Nose wheel- steering via a cable linkage enabled when gear extendedenabled when gear extended

Centering during retraction accomplished Centering during retraction accomplished automatically via a centering camautomatically via a centering cam


Brakes- separate hyd. system powered by Brakes- separate hyd. system powered by an electric pumpan electric pump

Each main gear- multiple disk brake- Each main gear- multiple disk brake- actuated by press. Fromactuated by press. From– Electric pumpElectric pump– Master cylinderMaster cylinder– Air Pressure (emergency)Air Pressure (emergency)


Struts: conventional oleo struts (air/oil)Struts: conventional oleo struts (air/oil)– Floating piston- air/hyd. Fluid- data plate on Floating piston- air/hyd. Fluid- data plate on

strut tells amt. Of strut to be showing on strut tells amt. Of strut to be showing on preflightpreflight

– Gear normally hydraulic – pneumatic for emerg. Gear normally hydraulic – pneumatic for emerg. Ext.Ext.


Main Gear:Main Gear:– StrutStrut– 2 ea. Actuators2 ea. Actuators– Torque linksTorque links– Landing lightLanding light– WheelWheel– Multiple disk brakeMultiple disk brake– Squat switch- left main (and on nose if Thrust Squat switch- left main (and on nose if Thrust

Rev.)Rev.)


Main gear- locked in retract by spring Main gear- locked in retract by spring loaded/hydraulic uplock actuatorloaded/hydraulic uplock actuator– In sequence with main actuator such that it In sequence with main actuator such that it

must reach full travel (release) prior to main must reach full travel (release) prior to main actuationactuation

– Lock ring within main actuator locks gear downLock ring within main actuator locks gear down Released with hyd. Press. To the retract side of Released with hyd. Press. To the retract side of

actuator thus no downlock pins requiredactuator thus no downlock pins required


Main Gear:Main Gear:– Gear door covers strut upon retraction- wheel Gear door covers strut upon retraction- wheel

not coverednot covered– Each main wheel has fusible plug- melts & Each main wheel has fusible plug- melts &

diffuses tire pressure after overheat (such as diffuses tire pressure after overheat (such as heavy braking)heavy braking)


Nose Gear:Nose Gear:– StrutStrut– 2 hyd. Actuators2 hyd. Actuators– Torque linksTorque links– Single wheelSingle wheel– Self-contained shimmy damperSelf-contained shimmy damper


Nose Gear- held retracted by hyd. Uplock Nose Gear- held retracted by hyd. Uplock mechanism- same as main gearmechanism- same as main gear

3 doors fully enclose nose gear upon 3 doors fully enclose nose gear upon retractionretraction– 2 fwd. Doors only open during extension & 2 fwd. Doors only open during extension &

retraction (transit)- aft remains upon during retraction (transit)- aft remains upon during extensionextension


Nosewheel Spin-up System (optional):Nosewheel Spin-up System (optional):– Reduces gravel spray at touchdown- uses bleed Reduces gravel spray at touchdown- uses bleed

airair– Prior to touchdown place Bleed air switch to Prior to touchdown place Bleed air switch to

LOW or HILOW or HI– Winshield Bleed AIR valve to OFFWinshield Bleed AIR valve to OFF– Nosewheel spin up control to ONNosewheel spin up control to ON


Nose wheel spin up system (above 60% N2)-Nose wheel spin up system (above 60% N2)-– Nosewheel RPM indicator illuminates green as speed Nosewheel RPM indicator illuminates green as speed

incr. Into 1,600 – 2,400 RPM range.incr. Into 1,600 – 2,400 RPM range.– Maintain speed with NOSE WHEEL SPIN-UP control- Maintain speed with NOSE WHEEL SPIN-UP control-

overspeed changes indicator changes to redoverspeed changes indicator changes to red– Use of windshield bleed (ice or rain) reduces wheel Use of windshield bleed (ice or rain) reduces wheel

acceleration rateacceleration rate– Position Spin-up control of OFF at nose touchdownPosition Spin-up control of OFF at nose touchdown


Controls- gear handle completes circuits to Controls- gear handle completes circuits to extend or retract solenoid of gear cnt’l valveextend or retract solenoid of gear cnt’l valve

On gnd. Spring-loaded plunger in handle On gnd. Spring-loaded plunger in handle mechanism prevents inadvertent retraction.mechanism prevents inadvertent retraction.

DC power to: lights, horn, lock solenoids via DC power to: lights, horn, lock solenoids via LDG GEAR CB on left panel (warning LDG GEAR CB on left panel (warning section)section)


Operation- with squat switch in flight pos.Operation- with squat switch in flight pos.– Lock solenoid energizes to retract plunger (if pwr. Fails- Lock solenoid energizes to retract plunger (if pwr. Fails-

no retract possible)no retract possible)– Gear handle actuated by pulling it out of detent position Gear handle actuated by pulling it out of detent position

to either UP or DOWNto either UP or DOWN– Indication- as each gear locks down the respective light Indication- as each gear locks down the respective light

should illuminate.should illuminate.– Red light indicates gear unsafe (illuminates when handle Red light indicates gear unsafe (illuminates when handle

moved out from up position until all 3 are down and moved out from up position until all 3 are down and locked & at retraction when any down lock released until locked & at retraction when any down lock released until all 3 gear are up and locked)all 3 gear are up and locked)

– Lights & horn can be tested by rotary test switchLights & horn can be tested by rotary test switch


Warning Horn- sounds when:Warning Horn- sounds when:– One or more gear not down & locked AND one One or more gear not down & locked AND one

or both throttles less than 70% N2 (later SN’s or both throttles less than 70% N2 (later SN’s also have an airspeed below 150 rqm’t)- Horn also have an airspeed below 150 rqm’t)- Horn can be silenced by HORN SILENCE PUSH can be silenced by HORN SILENCE PUSH button on gear control panelbutton on gear control panel

– Flaps beyond 15 deg. And one or more gear not Flaps beyond 15 deg. And one or more gear not down & locked- Warning horn cannot be down & locked- Warning horn cannot be silencedsilenced


Movement of gear handle:Movement of gear handle:– Energizes gear control valveEnergizes gear control valve– Closes hyd. System bypass valve to create hyd. Closes hyd. System bypass valve to create hyd.

Press. (HYD PRESS ON light illuminates)Press. (HYD PRESS ON light illuminates) When cycle complete valve opens & light goes outWhen cycle complete valve opens & light goes out

DC for lndg. Gear control circuit via GEAR CONTROL DC for lndg. Gear control circuit via GEAR CONTROL CB (in systems section) on left panelCB (in systems section) on left panel


Retraction- moving gear handle to UP:Retraction- moving gear handle to UP:– Energizes retract solenoid (gear cnt’l valve) & Energizes retract solenoid (gear cnt’l valve) &

positions to direct press. To retract side of each positions to direct press. To retract side of each gear actuator & preloads uplocksgear actuator & preloads uplocks

– Down lock in ea. Actuator releasesDown lock in ea. Actuator releases– Retraction beginsRetraction begins


Retraction- As each gear fully retractsRetraction- As each gear fully retracts– Spring loaded uplock engagesSpring loaded uplock engages– Uplock switch actuatedUplock switch actuated

When all 3 actuated gear cnt’l valve circuit is When all 3 actuated gear cnt’l valve circuit is interruptedinterrupted

Valve returns to neutralValve returns to neutral All position indicator light on panel go outAll position indicator light on panel go out


Extension- Placing handle in ext. pos.:Extension- Placing handle in ext. pos.:– Energizes extend solenoid (gear cnt’l valve)Energizes extend solenoid (gear cnt’l valve)– Valve positioned to direct press. To uplocks releasing Valve positioned to direct press. To uplocks releasing

them then:them then:– Press. Continues to actuators to extend then:Press. Continues to actuators to extend then:– Downlock switch is actuated- when all 3 actuated:Downlock switch is actuated- when all 3 actuated:– Cnt’l valve circuit interrupted- valve returns to neutral Cnt’l valve circuit interrupted- valve returns to neutral

positionposition– With no pressure on gear actuator- internal lock With no pressure on gear actuator- internal lock

mechanism engages; verified by visual indicator pins & mechanism engages; verified by visual indicator pins & 3 green lights.3 green lights.


Emergency Extension- during hydraulic or Emergency Extension- during hydraulic or electrical failureelectrical failure– Manually release uplocksManually release uplocks– Blow down with 2,00 psi pneumatic bottle (in rt. Blow down with 2,00 psi pneumatic bottle (in rt.

Nose baggage compt.Nose baggage compt.


Emergency Extension:Emergency Extension:– Pull AUX GEAR CONTOL T-handle & rotate clockwise Pull AUX GEAR CONTOL T-handle & rotate clockwise

(releases uplocks for gear free fall- 150 kts.)(releases uplocks for gear free fall- 150 kts.)– Use rudder to yaw aircraft (aids full extension- flaps 0)Use rudder to yaw aircraft (aids full extension- flaps 0)– Pull round know behind T-handle to blow gear down and Pull round know behind T-handle to blow gear down and

ensure extension (also opens a hyd. Fluid dump valve & ensure extension (also opens a hyd. Fluid dump valve & provides for fluid return to reservoirprovides for fluid return to reservoir

– Maintained in locked position by actuators (internal Maintained in locked position by actuators (internal lock). Hyd. Ext. inop. After bottle - Mx. Required.lock). Hyd. Ext. inop. After bottle - Mx. Required.


Nosewheel steering- mechanically linked Nosewheel steering- mechanically linked through nosewheel.through nosewheel.

Travel limited by rudder pedal stops to 20 Travel limited by rudder pedal stops to 20 deg.deg.

Application of diff. thrust actuates spring Application of diff. thrust actuates spring loaded bungee in nose gear providing loaded bungee in nose gear providing additional swiveladditional swivel


For towing- ensure flight control lock For towing- ensure flight control lock disengaged- don’t exceed 95 deg. disengaged- don’t exceed 95 deg. Nosewheel deflection or damage will occur-Nosewheel deflection or damage will occur-– Indicated by loss of nosewheel steering- DO Indicated by loss of nosewheel steering- DO

NOT FLY!NOT FLY!– Center nosewheel just prior to touchdown Center nosewheel just prior to touchdown

during crosswind lndg. Since nosewheel during crosswind lndg. Since nosewheel deflects anytime it’s extendeddeflects anytime it’s extended


Brakes- multi-disk powered by separate hyd. Brakes- multi-disk powered by separate hyd. SystemSystem

Constant press. Maintained for brakingConstant press. Maintained for braking Use with or w/o anti-skid featureUse with or w/o anti-skid feature Emer. Pneumatic braking available if brake hyd. Emer. Pneumatic braking available if brake hyd.

Pressure lost.Pressure lost. Braking initiated by rudder pedal master cylinders- Braking initiated by rudder pedal master cylinders-

pilot & co-pilot in series- whoever pushes harder pilot & co-pilot in series- whoever pushes harder ((most scaredmost scared) has braking control) has braking control


Brake System components:Brake System components:– Hydraulic accumulator- stores pressureHydraulic accumulator- stores pressure– Reservoir- pressurized by cabin air- fluid level Reservoir- pressurized by cabin air- fluid level

and pressure- pre-flight itemsand pressure- pre-flight items


Anti-skid system- permits max. braking w/o Anti-skid system- permits max. braking w/o skidding under all conditionsskidding under all conditions

Speed transducer in ea. Wheel sends speed Speed transducer in ea. Wheel sends speed signal to control box (detects sudden decel.- signal to control box (detects sudden decel.- impending skid)impending skid)– Causes anti-skid valve to relieve hyd. Brake Causes anti-skid valve to relieve hyd. Brake

pressure- self-restoring systempressure- self-restoring system


Touchdown protection available on later models Touchdown protection available on later models (prevents touchdown w/ locked wheels) otherwise (prevents touchdown w/ locked wheels) otherwise allow wheels spin up after lndg. To prevent allow wheels spin up after lndg. To prevent blowout; Also- do not pump brakes- HOLD.blowout; Also- do not pump brakes- HOLD.

W/O touchdown protection taxi w. anti-skid OFFW/O touchdown protection taxi w. anti-skid OFF Deploy speedbrakes after touchdown to aid Deploy speedbrakes after touchdown to aid

braking (increases effectiveness by putting more braking (increases effectiveness by putting more wt. on wheels).wt. on wheels).


Anti-skid System Operation-Anti-skid System Operation-– W/ gear handle down a separate DC hyd. Pump W/ gear handle down a separate DC hyd. Pump

maintains 900 – 1,300 psi for brake systemmaintains 900 – 1,300 psi for brake system– Accumulator- dampens pressure surgesAccumulator- dampens pressure surges– Reservoir supplies fluid to master cylindersReservoir supplies fluid to master cylinders– Depressing brake pedals applies master Depressing brake pedals applies master

cylinder press. To actuate the PBV (power cylinder press. To actuate the PBV (power brake valve which meters pump pr. To brakes brake valve which meters pump pr. To brakes w.r.t. pedal pressure)w.r.t. pedal pressure)


Anti-Skid operation ctn.:Anti-Skid operation ctn.:– Fwd. speed of 12 kts. Required for operation- Fwd. speed of 12 kts. Required for operation-

disengages below 12 kts.disengages below 12 kts.– Differential braking availableDifferential braking available– If ANTI-SKID INOP annunciator comes on- a If ANTI-SKID INOP annunciator comes on- a

system fault has been detected- switch system system fault has been detected- switch system off.off. Pressure below 750 psi causes this plus the Pressure below 750 psi causes this plus the PWR PWR

BRK PRESS LOBRK PRESS LO annunciator to come on annunciator to come on


Anti-Skid Test-Anti-Skid Test-– On ground place rotary test switch in On ground place rotary test switch in

ANTISKID- ANTISKID INOP light comes on ANTISKID- ANTISKID INOP light comes on thenthen

– Goes out 3 sec after test switch movedGoes out 3 sec after test switch moved– System self-tests airborne each time gear System self-tests airborne each time gear

handle is selected down- result same as gnd. handle is selected down- result same as gnd. testtest


Parking BrakesParking Brakes– Apply brakes as normal and pull park brake Apply brakes as normal and pull park brake

handle on left lower side of pilot’s instr. Panelhandle on left lower side of pilot’s instr. Panel Mechanically actuates parking brake valve- traps Mechanically actuates parking brake valve- traps

fluidfluid Release brakes by pushing on PARK BRAKE handleRelease brakes by pushing on PARK BRAKE handle NOTE: Do not apply park brake after a hard stop- NOTE: Do not apply park brake after a hard stop-

heat x-fer to wheel may melt fuse plugheat x-fer to wheel may melt fuse plug


Emergency Brakes- uses same pneumatic Emergency Brakes- uses same pneumatic system as for emerg. Gear ext.system as for emerg. Gear ext.

Bottle press. Adequate for stopping even if Bottle press. Adequate for stopping even if gear has been blown down.gear has been blown down.

On SN’s 2 – 460 if pump fails manual On SN’s 2 – 460 if pump fails manual braking still avail using accumulator press.- braking still avail using accumulator press.- be ready with emerg. Brakes.be ready with emerg. Brakes.


Emerg. Brake Operation:Emerg. Brake Operation:– Pull EMER BRAKE PULL aft- mechanically Pull EMER BRAKE PULL aft- mechanically

actuates emerg. Brake valve- meters air press. actuates emerg. Brake valve- meters air press. Via shuttle valves to brakes- proportional to Via shuttle valves to brakes- proportional to amt. of movementamt. of movement

– Air supplied to both brakes simultaneously- no Air supplied to both brakes simultaneously- no diff. brakingdiff. braking

– Return lever to orig. position to vent trapped Return lever to orig. position to vent trapped brake press. Overboard- releases brakesbrake press. Overboard- releases brakes


EMER. BRAKE NOTES:EMER. BRAKE NOTES:– Do not actuate brake pedals during emerg. Do not actuate brake pedals during emerg.

Braking as shuttle valve may be disrupted Braking as shuttle valve may be disrupted allowing air press. Into hyd. Line rupturing brake allowing air press. Into hyd. Line rupturing brake reservoir.reservoir.

– No anti-skid avail. During emerg. BrakingNo anti-skid avail. During emerg. Braking– Do not attempt taxi after Emer. Brake Do not attempt taxi after Emer. Brake

application- mx. Required.application- mx. Required.

The EndThe End

Date post:	16-Dec-2015
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AST 473 Cessna Citation II Landing Gear and Brakes Dr. R. Kurt Barnhart.

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