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

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Presentation on theme: "AST 473 Cessna Citation II Landing Gear and Brakes Dr. R. Kurt Barnhart."— Presentation transcript:

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

2 Landing Gear and Brakes  Electrically controlled- Hydraulically activated  Mechanically actuated doors cover nose gear and struts of main gear when retracted- main gear wheels uncovered in flight  Nosewheel steering- via mechanically linked rudder pedals- shimmy damp. Included- on top of nose strut  Braking- W/ or W/O anti-skid & pneumatic emerg. Braking  Indication- 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 actuation –Nose gear- 2 identical actuators- retracts forward –Elec. 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 when  Throttle 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 extended  Centering during retraction accomplished automatically via a centering cam

6 Landing Gear and Brakes  Brakes- separate hyd. system powered by an electric pump  Each main gear- multiple disk brake- actuated by press. From –Electric pump –Master cylinder –Air 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 preflight –Gear normally hydraulic – pneumatic for emerg. Ext.

8 Landing Gear and Brakes  Main Gear: –Strut –2 ea. Actuators –Torque links –Landing light –Wheel –Multiple disk brake –Squat switch- left main (and on nose if Thrust Rev.)

9 Landing Gear and Brakes  Main gear- locked in retract by spring loaded/hydraulic uplock actuator –In sequence with main actuator such that it must reach full travel (release) prior to main actuation –Lock ring within main actuator locks gear down  Released 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 covered –Each main wheel has fusible plug- melts & diffuses tire pressure after overheat (such as heavy braking)

11 Landing Gear and Brakes  Nose Gear: –Strut –2 hyd. Actuators –Torque links –Single wheel –Self-contained shimmy damper

12 Landing Gear and Brakes  Nose Gear- held retracted by hyd. Uplock mechanism- same as main gear  3 doors fully enclose nose gear upon retraction –2 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 air –Prior to touchdown place Bleed air switch to LOW or HI –Winshield Bleed AIR valve to OFF –Nosewheel 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 red –Use of windshield bleed (ice or rain) reduces wheel acceleration rate –Position 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 valve  On 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 DOWN –Indication- 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 panel –Flaps 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 valve –Closes hyd. System bypass valve to create hyd. Press. (HYD PRESS ON light illuminates)  When cycle complete valve opens & light goes out DC 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 uplocks –Down lock in ea. Actuator releases –Retraction begins

20 Landing Gear and Brakes  Retraction- As each gear fully retracts –Spring loaded uplock engages –Uplock switch actuated  When all 3 actuated gear cnt’l valve circuit is interrupted  Valve returns to neutral  All 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 position –With 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 failure –Manually release uplocks –Blow 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 reservoir –Maintained 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. System  Constant press. Maintained for braking  Use with or w/o anti-skid feature  Emer. 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 pressure –Reservoir- 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 conditions  Speed 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 OFF  Deploy 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 system –Accumulator- dampens pressure surges –Reservoir supplies fluid to master cylinders –Depressing 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 available –If 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 then –Goes out 3 sec after test switch moved –System self-tests airborne each time gear handle is selected down- result same as gnd. test

33 Landing Gear and Brakes  Parking Brakes –Apply brakes as normal and pull park brake handle on left lower side of pilot’s instr. Panel  Mechanically actuates parking brake valve- traps fluid  Release brakes by pushing on PARK BRAKE handle  NOTE: 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 movement –Air supplied to both brakes simultaneously- no diff. braking –Return 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. Braking –Do not attempt taxi after Emer. Brake application- mx. Required.

37 The End


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