AST 473 Cessna Citation II Landing Gear and Brakes

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AST 473 Cessna Citation II Landing Gear and Brakes

• Dr. R. Kurt Barnhart

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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

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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. Cntl valve directs hyd. Press. For gear
  actuation

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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

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Landing Gear and Brakes

• Nose wheel- steering via a cable linkage enabled
  when gear extended
• Centering during retraction accomplished
  automatically via a centering cam

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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)

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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.

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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.)

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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

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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)

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Landing Gear and Brakes

• Nose Gear
• Strut
• 2 hyd. Actuators
• Torque links
• Single wheel
• Self-contained shimmy damper

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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

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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

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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

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Landing Gear and Brakes

• Controls- gear handle completes circuits to
  extend or retract solenoid of gear cntl 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)

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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

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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 SNs also
  have an airspeed below 150 rqmt)- 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

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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

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Landing Gear and Brakes

• Retraction- moving gear handle to UP
• Energizes retract solenoid (gear cntl valve)
  positions to direct press. To retract side of
  each gear actuator preloads uplocks
• Down lock in ea. Actuator releases
• Retraction begins

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Landing Gear and Brakes

• Retraction- As each gear fully retracts
• Spring loaded uplock engages
• Uplock switch actuated
• When all 3 actuated gear cntl valve circuit is
  interrupted
• Valve returns to neutral
• All position indicator light on panel go out

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Landing Gear and Brakes

• Extension- Placing handle in ext. pos.
• Energizes extend solenoid (gear cntl 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
• Cntl 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.

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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.

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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.

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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

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Landing Gear and Brakes

• For towing- ensure flight control lock
  disengaged- dont 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
  its extended

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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

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Landing Gear and Brakes

• Brake System components
• Hydraulic accumulator- stores pressure
• Reservoir- pressurized by cabin air- fluid level
  and pressure- pre-flight items

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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

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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).

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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)

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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

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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

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Landing Gear and Brakes

• Parking Brakes
• Apply brakes as normal and pull park brake handle
  on left lower side of pilots 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

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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 SNs 2 460 if pump fails manual braking
  still avail using accumulator press.- be ready
  with emerg. Brakes.

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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

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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.

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The End