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