Presentation on theme: "AST 473 Cessna Citation II Landing Gear and Brakes"— Presentation transcript:
1 AST 473 Cessna Citation II Landing Gear and Brakes Dr. R. Kurt Barnhart
2 Landing Gear and Brakes Electrically controlled- Hydraulically activatedMechanically actuated doors cover nose gear and struts of main gear when retracted- main gear wheels uncovered in flightNosewheel steering- via mechanically linked rudder pedals- shimmy damp. Included- on top of nose strutBraking- W/ or W/O anti-skid & pneumatic emerg. BrakingIndication- colored indicator lights & warn. horn
3 Landing Gear and Brakes Overview:Each gear retracts inboard utilizing 2 hyd. Actuators ea.- one for uplock release and one for gear actuationNose gear- 2 identical actuators- retracts forwardElec. Cnt’l valve directs hyd. Press. For gear actuation
4 Landing Gear and Brakes Indication:One red and three green down/locked position indicator lights plus warning horn whenThrottle or flap settings indicate lndg. But gear not down & locked
5 Landing Gear and Brakes Nose wheel- steering via a cable linkage enabled when gear extendedCentering during retraction accomplished automatically via a centering cam
6 Landing Gear and Brakes Brakes- separate hyd. system powered by an electric pumpEach main gear- multiple disk brake- actuated by press. FromElectric pumpMaster cylinderAir Pressure (emergency)
7 Landing Gear and Brakes Struts: conventional oleo struts (air/oil)Floating piston- air/hyd. Fluid- data plate on strut tells amt. Of strut to be showing on preflightGear normally hydraulic – pneumatic for emerg. Ext.
8 Landing Gear and Brakes Main Gear:Strut2 ea. ActuatorsTorque linksLanding lightWheelMultiple disk brakeSquat switch- left main (and on nose if Thrust Rev.)
9 Landing Gear and Brakes Main gear- locked in retract by spring loaded/hydraulic uplock actuatorIn sequence with main actuator such that it must reach full travel (release) prior to main actuationLock ring within main actuator locks gear downReleased with hyd. Press. To the retract side of actuator thus no downlock pins required
10 Landing Gear and Brakes Main Gear:Gear door covers strut upon retraction- wheel not coveredEach main wheel has fusible plug- melts & diffuses tire pressure after overheat (such as heavy braking)
11 Landing Gear and Brakes Nose Gear:Strut2 hyd. ActuatorsTorque linksSingle wheelSelf-contained shimmy damper
12 Landing Gear and Brakes Nose Gear- held retracted by hyd. Uplock mechanism- same as main gear3 doors fully enclose nose gear upon retraction2 fwd. Doors only open during extension & retraction (transit)- aft remains upon during extension
13 Landing Gear and Brakes Nosewheel Spin-up System (optional):Reduces gravel spray at touchdown- uses bleed airPrior to touchdown place Bleed air switch to LOW or HIWinshield Bleed AIR valve to OFFNosewheel spin up control to ON
14 Landing Gear and Brakes Nose wheel spin up system (above 60% N2)-Nosewheel RPM indicator illuminates green as speed incr. Into 1,600 – 2,400 RPM range.Maintain speed with NOSE WHEEL SPIN-UP control- overspeed changes indicator changes to redUse of windshield bleed (ice or rain) reduces wheel acceleration ratePosition Spin-up control of OFF at nose touchdown
15 Landing Gear and Brakes Controls- gear handle completes circuits to extend or retract solenoid of gear cnt’l valveOn gnd. Spring-loaded plunger in handle mechanism prevents inadvertent retraction.DC power to: lights, horn, lock solenoids via LDG GEAR CB on left panel (warning section)
16 Landing Gear and Brakes Operation- with squat switch in flight pos.Lock solenoid energizes to retract plunger (if pwr. Fails- no retract possible)Gear handle actuated by pulling it out of detent position to either UP or DOWNIndication- as each gear locks down the respective light should illuminate.Red light indicates gear unsafe (illuminates when handle moved out from up position until all 3 are down and locked & at retraction when any down lock released until all 3 gear are up and locked)Lights & horn can be tested by rotary test switch
17 Landing Gear and Brakes Warning Horn- sounds when:One or more gear not down & locked AND one or both throttles less than 70% N2 (later SN’s also have an airspeed below 150 rqm’t)- Horn can be silenced by HORN SILENCE PUSH button on gear control panelFlaps beyond 15 deg. And one or more gear not down & locked- Warning horn cannot be silenced
18 Landing Gear and Brakes Movement of gear handle:Energizes gear control valveCloses hyd. System bypass valve to create hyd. Press. (HYD PRESS ON light illuminates)When cycle complete valve opens & light goes outDC for lndg. Gear control circuit via GEAR CONTROL CB (in systems section) on left panel
19 Landing Gear and Brakes Retraction- moving gear handle to UP:Energizes retract solenoid (gear cnt’l valve) & positions to direct press. To retract side of each gear actuator & preloads uplocksDown lock in ea. Actuator releasesRetraction begins
20 Landing Gear and Brakes Retraction- As each gear fully retractsSpring loaded uplock engagesUplock switch actuatedWhen all 3 actuated gear cnt’l valve circuit is interruptedValve returns to neutralAll position indicator light on panel go out
21 Landing Gear and Brakes Extension- Placing handle in ext. pos.:Energizes extend solenoid (gear cnt’l valve)Valve positioned to direct press. To uplocks releasing them then:Press. Continues to actuators to extend then:Downlock switch is actuated- when all 3 actuated:Cnt’l valve circuit interrupted- valve returns to neutral positionWith no pressure on gear actuator- internal lock mechanism engages; verified by visual indicator pins & 3 green lights.
22 Landing Gear and Brakes Emergency Extension- during hydraulic or electrical failureManually release uplocksBlow down with 2,00 psi pneumatic bottle (in rt. Nose baggage compt.
23 Landing Gear and Brakes Emergency Extension:Pull AUX GEAR CONTOL T-handle & rotate clockwise (releases uplocks for gear free fall- 150 kts.)Use rudder to yaw aircraft (aids full extension- flaps 0)Pull round know behind T-handle to blow gear down and ensure extension (also opens a hyd. Fluid dump valve & provides for fluid return to reservoirMaintained in locked position by actuators (internal lock). Hyd. Ext. inop. After bottle - Mx. Required.
24 Landing Gear and Brakes Nosewheel steering- mechanically linked through nosewheel.Travel limited by rudder pedal stops to 20 deg.Application of diff. thrust actuates spring loaded bungee in nose gear providing additional swivel
25 Landing Gear and Brakes For towing- ensure flight control lock disengaged- don’t exceed 95 deg. Nosewheel deflection or damage will occur-Indicated by loss of nosewheel steering- DO NOT FLY!Center nosewheel just prior to touchdown during crosswind lndg. Since nosewheel deflects anytime it’s extended
26 Landing Gear and Brakes Brakes- multi-disk powered by separate hyd. SystemConstant press. Maintained for brakingUse with or w/o anti-skid featureEmer. Pneumatic braking available if brake hyd. Pressure lost.Braking initiated by rudder pedal master cylinders- pilot & co-pilot in series- whoever pushes harder (most scared) has braking control
27 Landing Gear and Brakes Brake System components:Hydraulic accumulator- stores pressureReservoir- pressurized by cabin air- fluid level and pressure- pre-flight items
28 Landing Gear and Brakes Anti-skid system- permits max. braking w/o skidding under all conditionsSpeed transducer in ea. Wheel sends speed signal to control box (detects sudden decel.- impending skid)Causes anti-skid valve to relieve hyd. Brake pressure- self-restoring system
29 Landing Gear and Brakes Touchdown protection available on later models (prevents touchdown w/ locked wheels) otherwise allow wheels spin up after lndg. To prevent blowout; Also- do not pump brakes- HOLD.W/O touchdown protection taxi w. anti-skid OFFDeploy speedbrakes after touchdown to aid braking (increases effectiveness by putting more wt. on wheels).
30 Landing Gear and Brakes Anti-skid System Operation-W/ gear handle down a separate DC hyd. Pump maintains 900 – 1,300 psi for brake systemAccumulator- dampens pressure surgesReservoir supplies fluid to master cylindersDepressing brake pedals applies master cylinder press. To actuate the PBV (power brake valve which meters pump pr. To brakes w.r.t. pedal pressure)
31 Landing Gear and Brakes Anti-Skid operation ctn.:Fwd. speed of 12 kts. Required for operation- disengages below 12 kts.Differential braking availableIf ANTI-SKID INOP annunciator comes on- a system fault has been detected- switch system off.Pressure below 750 psi causes this plus the PWR BRK PRESS LO annunciator to come on
32 Landing Gear and Brakes Anti-Skid Test-On ground place rotary test switch in ANTISKID- ANTISKID INOP light comes on thenGoes out 3 sec after test switch movedSystem self-tests airborne each time gear handle is selected down- result same as gnd. test
33 Landing Gear and Brakes Parking BrakesApply brakes as normal and pull park brake handle on left lower side of pilot’s instr. PanelMechanically actuates parking brake valve- traps fluidRelease brakes by pushing on PARK BRAKE handleNOTE: Do not apply park brake after a hard stop- heat x-fer to wheel may melt fuse plug
34 Landing Gear and Brakes Emergency Brakes- uses same pneumatic system as for emerg. Gear ext.Bottle press. Adequate for stopping even if gear has been blown down.On SN’s 2 – 460 if pump fails manual braking still avail using accumulator press.- be ready with emerg. Brakes.
35 Landing Gear and Brakes Emerg. Brake Operation:Pull EMER BRAKE PULL aft- mechanically actuates emerg. Brake valve- meters air press. Via shuttle valves to brakes- proportional to amt. of movementAir supplied to both brakes simultaneously- no diff. brakingReturn lever to orig. position to vent trapped brake press. Overboard- releases brakes
36 Landing Gear and Brakes EMER. BRAKE NOTES:Do not actuate brake pedals during emerg. Braking as shuttle valve may be disrupted allowing air press. Into hyd. Line rupturing brake reservoir.No anti-skid avail. During emerg. BrakingDo not attempt taxi after Emer. Brake application- mx. Required.