AST 473 Cessna Citation II Landing Gear and Brakes

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