32 Landing gear

 

TTP	B1-L3	ATA32
Beech 90 Series	B2-L2	Landing gear

32 LANDING GEAR 

-00 General                          

-10 Main Gear and Doors 

-20 Nose Gear and Doors 

-30 Extension and Retraction 

-40 Wheels and Brakes 

-50 Steering 

-60 Position and Warning 

-70 Supplementary Gear  

Retractable tricycle type landing gear of the King Air C90A/B/GT/GTi/E90 is electrically controlled and hydraulically actuated. A hydraulic powerpack supplies hydraulic pressure to the landing gear. Hydraulic fluid flow to the landing gear actuators is controlled by an electrically actuated selector valve. Safety switches on the main landing gear prevent accidental landing gear retraction.

The main and nose landing gear assemblies extend and retract by means of an electrically controlled hydraulic power pack.

The landing gear assemblies have the following components:

•  Shock struts

•  Torque knees

•  Drag legs

•  Wheels

•  Tires

The  main  wheel  is  supplied  with  an  8.50  x 10-inch, 8- or 10-ply rib, nylon tubeless tire. 

The nose wheel is supplied with a 6.50 x 10-inch, 6-ply rib, nylon tubeless tire.

Both main and nose wheels have inner and outer wheel halves bolted together. Washers beneath the nuts and bolt heads prevent galling and stress concentration. In all wheels, a packing in the groove in the inner wheel half, seals the wheel halves to prevent air leakage. Bearing cups and cones are around the hub. Balance weights fasten with nuts and screws to the inner surfaces. 

Hub caps and lock rings in the outer wheel hub area  retain  bearing  lubricant and  seal  against dirt. The inner wheels contain a retainer and a seal
assembly around the hub area. Torque keys are secured into slots in the inner wheel half flange area with screws.

The axle flange, spacers, and axle nut retain the grease seals around the wheel.

The shimmy damper is a balanced hydraulic cylinder, mounted on the right side of the nose gear strut. It bleeds fluid through an orifice to dampen nose wheel shimmy.

Shock Strut - The shock strut is made of top and bottom machined cylinders that contain a mixture of oil and air. The top and bottom cylinders give changes in the shock-absorb rates.

Torque Links - The torque links give a mechanical link between the top and bottom parts of the shock strut and help to keep the nose wheel aligned with the airframe.  

A  landing  gear  control  handle  operates  the landing gear through the hydraulic power pack. 

Moving the handle up or down retracts or extends the landing gear. When fully extended, the landing gear is a braced semi-cantilevered construction. The drag legs lock in place to become rigid components of the gear assemblies. Oleo pneumatic shock struts, forming semi-cantilevered beams, and the upper ends of the drag legs attach the gear to the aircraft structure. 

Each main gear locks down with a latch hook, lock link, and a lock link guide attached to the drag brace upper legs.

The nose gear locks down with an internal locking mechanism in the hydraulic actuator, plus a drag brace overcenter action.

 

The upper and lower portions of the shock struts connect with the torque knees. The torque knees allow strut compression and extension, but prevent rotation between the strut pistons and cylinders. On the nose gear assembly, the torque knees transmit steering motion to the nosewheel.

 Using a hydropneumatic design, the shock struts fill with  both  hydraulic  fluid  and  compressed air. The compressed air charge bears the aircraft weight and absorbs taxiing shocks.

 Nose and main gear strut extension is limited only by the torque knee assembly. At touchdown, the lower portions of the struts travel upward and are forced into the upper cylinders. This action forces hydraulic fluid through a metering orifice to further compress the air charge. The combined actions absorb landing shock forces. Orifice actions also reduce bounce during landing.

The landing gear assemblies comprise the following:

•  Hydraulic powerpack

•  Tubing

•  Reservoir

•  Hydraulic actuators

•  Brake system

•  Accumulator

•  Hydraulic fluid level sensor system

Three hydraulic lines supply pressure to the nose and main gear actuators. A pressure line from the powerpack provides the normal landing gear extension. A second line provides normal retraction. The third line provides manual or emergency extension  using  a  cockpit-mounted  hydraulic hand pump. On the main gear, the retract hoses connect to the bottom of the actuators. On the nose gear, the retract hose connects to the actuator via a swivel fitting that passes through the actuator support assembly. The extend and emergency extend hoses connect to the top of each actuator.

Actuators

Each main gear locks in the down position with a latch hook, lock link, and lock link guide attached to the drag brace upper legs. Hydraulic pressure holds the landing gear in the up position.

Plumbing

Hydraulic plumbing for the retract, extend, and emergency modes runs from the powerpack to each gear actuator. The extend and emergency extend lines connect to fittings on shuttle valves in each actuator. Spring-loaded shuttle valves allow fluid flow from the extend ports through the actuator. Fluid entering the ports must overcome spring pressure, which restricts reverse flow.

 The plumbing lines  are  color-coded with tape two inches from each connection. The following codes identify the plumbing lines:

•  Orange—Regulated engine bleed air

•  White—Extend

•  Blue—Retract

•  Yellow—Manual hand pump suction

 

•  Brown/white—Manual       hand       pump pressure

•  Brown—Emergency (manual) extend

•  Purple—Hydraulic fluid fill

 

Fill Reservoir

A fill reservoir, just inboard of the left nacelle and forward of the front spar, contains a cap and dipstick assembly, marked HOT/FILL–COLD/ FILL, to maintain the system fluid level. The fill reservoir is  pressurized to 18-20 psi from the pneumatic system. The vent line orifice from the fill reservoir requires periodic cleaning.

 

Powerpack

The hydraulic powerpack is just forward of the main spar in the cabin center aisle beneath the floorboards. This powerpack includes the following components:

•  Hydraulic pump

•  28-VDC motor

•  Primary and secondary reservoirs

•  Filter screens

•  Gear-up selector solenoid

•  Gear-up pressure switch

•  Low fluid level sensor

The landing gear doors are side hinged and include one set of nose gear doors and two sets of main gear doors. The doors are spring loaded open and are mechanically closed by gear movement as the landing gears retract. As the main gear retract,  a door uplock hook on the gear engages a single roller on a torque tube which rotates and pulls the doors closed. As the nose gear retracts, a roller on each side of the strut engages a cam assembly on each door, which pulls the door shut. During gear extension, the reverse action takes place and spring-loading opens the doors.

Shimmy Damper ( Lord Shimmy Damper) - The shimmy damper uses rubber with a lubricant to absorb nose wheel vibration. The damper is connected between the shock strut and the steering arm assembly.

Shimmy Damper gives resistance to shimmy when it moves hydraulic fluid through the small orifices in a piston. The damper is connected between the shock strut and the steering arm assembly.

Landing Gear Retraction

As the aircraft takes off or is placed on jacks, the struts extend and the right safety switch provides a ground to the gear handle downlock hook rotary solenoid, pulling the hook clear of the handle. The handle can now be pulled out and moved up. The landing gear remote power relay is powered closed, sending current to the pump motor. The solenoid selector valve on the powerpack is energized to port hydraulic fluid to the retract side of the actuators. (The solenoid selector valve is spring loaded to the extend position and moves to the retract position only when energized.)

 The main gear actuators moves to the retract position when hydraulic pressure is applied, but the mechanical downlock assembly in the nose gear actuator requires 200 to 400 psi to unlock before the nose actuator retracts. With pressure to the upside of the actuators, all three landing gear are driven to the up or retracted position. Fluid from the extend or downside of the actuator returns to the powerpack primary reservoir via the extend lines and a channel in the powered solenoid selector valve.

 With the actuators in the full-up or retract posi- tion, hydraulic system pressure continues to increase  to 1,800-1,850 psi. At this value,  the pressure switch on the motor end of the power opens and removes power from the remote relay, turning off the pump motor.

 There are no mechanical  gear up locks in the system; trapped hydraulic pressure in the retract lines holds the landing gear up. As the trapped hydraulic pressure bleeds  down to 1,400 from the 1,800-1,850 psi value,  the pressure switch closes and the pump drives the pressure back up to the 1,800-1,850 psi value. Automatic cycling of the pump maintains pressure to keep the landing gear up. A piston-type accumulator/pressure gauge assembly, in the left wing center section, is plumbed into the gear up lines to delay the bleed downtime of the trapped hydraulic pressure. Normal accumulator static pressure is serviced to 700-800 psi of dry nitrogen. With the landing gear retracted, this static pressure is increased to the dynamic hydraulic pressure. An accumulator with a low or depleted precharge causes the system to cycle frequently.

    WARNING: Never service the accumulator or the hydraulic system, or do maintenance or rigging of the landing gear, without first placing the aircraft on jacks. Servicing the accumulator without placing the aircraft on jacks may inadvertently retract the landing gear causing severe aircraft damage and personal injury.

Landing Gear Extension

 

When the landing gear control handle is in the down position, the landing gear remote  power relay is powered closed sending current to the pump motor. The solenoid selector valve on the powerpack is deenergized causing the spring- loaded valve to reposition to port pressurized hydraulic fluid to the extend side of the actuators. Hydraulic pressure on the downside of the actuators drives all three landing gear to the down or extended position. The nose gear actuator, with its internal locking mechanism, locks down and the main gear locks down with J-hooks and pins on the drag braces. Fluid from the up or retract side of the actuators is returned to the powerpack primary reservoir via the retract lines and a channel in the relaxed solenoid selector valve

Pressurized fluid from the pump opens a pressure check valve in the powerpack to allow return fluid into the primary reservoir. Since the  main  gear  is  lowered  into  the  slip  steam, air loading attempts to snatch the main gear to the extended position. To prevent this, one-way restrictor valves are installed in the up ports of the actuators to slow the flow of fluid from the actuators and increase the main gear extension time. When all three landing gear are down and locked, the circuit to the pump relay is opened, which turns off the pump motor. Three landing gear down switches (one on each gear drag brace and a downlock switch built into the nose gear actuator) must all be opened to open the pump relay. As the three gears are mechanically locked down,  normal  hydraulic  pressure  bleed down is allowed and the pump does not cycle after landing gear extension as it did on retraction.

Landing Gear Manual Extension

 

The powerpack assembly contains two coaxial reservoirs in a single assembly.

 The primary reservoir containing the motor- driven pump is inside the secondary reservoir, which forms the external body or shell of the powerpack assembly. Holes along the top of the primary reservoir allow hydraulic fluid to transfer from the top of the secondary reservoir into the primary reservoir. Both reservoirs are normally kept completely full from the fill reservoir in the left wing center section.

 Should one of the lines in the normal extend system fail and allow the system hydraulic fluid to be pumped overboard, the fill reservoir would supply its contents to the primary reservoir. The primary reservoir would then empty out and the top level of  the  secondary  reservoir  would  be  depleted, but only to the level of the holes in the primary reservoir. The pump, in the primary reservoir cavity, continues to run dry until the 2-amp control circuit breaker is pulled. Sufficient fluid is left in the secondary reservoir for manual landing gear extension.

 Manual landing gear extension is provided through a hydraulic hand pump placarded LANDING GEAR ALTERNATE EXTENSION,  on  the  floor  between  the  pilot seat and the pedestal, and a system of indepen- dent alternate extension lines. The pump is used when manual extension of the gear is required. To extend the gear with this system, pull the landing gear control circuit breaker on the pilot inboard subpanel and place the landing gear control handle in the DN position. Slide the manual pump handle from under the securing clip and pump the handle up and down to extend the gear. As the handle is pumped, hydraulic fluid is drawn from the hand pump suction port of the secondary reservoir into the pump. Fluid under pressure from the pump is routed through the service valve to the shuttle valve in each landing gear actuator and to the hand pump dump valve. Fluid pressure at the landing gear actuator shuttle valves positions the valves to allow fluid to flow into the extend side of the actuator  cylinders. As the actuator pistons move to extend the landing gear, the fluid in the retract side of the actuators exits through the normal retract port of the actuators and flows back to the powerpack through the normal retract plumbing. The hand pump pressure routed to the hand pump dump valve unseats the internal dump valve to allow the return fluid from the actuators to flow back into the primary reservoir.

 As the landing gear is being pumped down, hydraulic pressure is trapped in the alternate extension  fluid lines.  When  the  manual  pump handle is in the fully-down position, an internal relief valve in the pump is opened to relieve this hydraulic pressure. Ensure the pump handle is in the fully-down position and placed under the securing clip prior to performing a normal retract cycle.

Landing Gear Maintenance Retract

 

With the aircraft on jacks and external power sup- plied, pulling the red knob on the top of the service valve directs hand-pump pressure to the retract side of the landing gear actuators. Although pulling the red knob up makes the landing gear motor circuit inert, pull the 60-amp circuit breaker to the motor, also. The landing gear handle must be placed to the up position to power up the solenoid selector valve which allows hydraulic fluid in the extent side of the actuators to flow back into the primary reservoir. Without power on the aircraft and the gear handle up, attempting to hand pump the landing gear up results in a liquid lock on the actuator downlines and the landing gear does NOT  retract.  After  required  maintenance  has been accomplished, the red knob can be pushed down and the hand pump can be used to extend the landing gear.

 After any maintenance  requiring service  valve operation,  the  red  knob  must  be  safety  wired to the down position. If the knob is not safetied down, normal operation of the landing gear may cause the red knob to move up. With the knob in the up position, the landing gear can not be extended with the powerpack or the hand pump.

 

Service Valve

A service  valve,  forward of the powerpack in conjunction with the manual hand pump, may be used to raise (or lower) the gear for maintenance. The service valve on aircraft LJ-1063 to LJ-1099 has a plunger retainer and a detent pin to keep the service valve knob down. On aircraft LJ-1100 and after, the valve has been redesigned and a wedging assembly is provided to wedge the valve to the up position. A service valve switch incorporated into the service valve assembly interrupts the circuit to the gear motor when the red knob is pulled up.

Gearbox And Clutch Assemblies

 

The gearbox and clutch assemblies are located below  the  floor web  assembly  forward  of  the passenger seats in the passenger cargo compartment. The motor that operates the landing gear retraction system is mounted on the gearbox. The clutch protects the landing gear retraction system from overloads and absorbs the shock of starting and stopping.

Hydraulic brake system Operate the hydraulic brakes by depressing either the pilot or copilot toe brake pedals mounted to the top of each  rudder pedal  arm. Depressing the left or right pedal can independently operate either left and right brake assemblies. MIL-5606 hydraulic fluid is used in the braking system and is stored in a reservoir on the upper left side of the forward pressure bulkhead in the avionics bay. Fluid from the reservoir is gravity fed to the pilot master  cylinders.

The main landing wheels are equipped with multiple-disc type hydraulic brakes actuated by master cylinder at the rudder pedals of either the pilot or copilot position. A shuttle valve adjacent to each set of pedals permits changing braking action from one set of pedals to the other.

Parking brake system Cable actuated dual parking valves are adjacent to the rudder pedals between the master cylinders of the pilot rudder pedals. The parking brake handle is on the pilot left subpanel. After the brake pedals have been depressed to build up pressure in the brake lines, both valves are closed simultaneously by pulling on the parking brake handle. This traps hydraulic pressure in the brake lines. The parking brake releases by briefly depressing the brake pedals to equalize hydraulic pressure on both sides of the valves. The brake handle is then pushed to open the parking brake valves and release hydraulic pressure.

Parking Brake Handle

 

Pulling the  PARKING BRAKE handle on the pilot left subpanel sets the parking brakes.  Pressing  the  pilot  brake  pedals  develops brake line pressure. Pulling the PARKING BRAKE handle locks pressure in the lines. The parking brakes are released by first briefly pressing the brake pedals and then pushing in the parking brake handle

Emergency Landing Gear Clutch Disengage Lever

 

During manual landing gear extension, the landing gear motor must be disengaged from the landing gear drive mechanism). This is accomplished with a manually operated clutch disengage lever located adjacent to the emergency landing gear extension handle. To disengage the clutch, pull the clutch lever up and turn clockwise. To engage the clutch, turn the clutch lever counterclockwise and release.

The landing gear emergency handle on the floor-board right of the pilot seat, is used for manual extension of all landing gear, after the landing gear clutch has been disengaged. The handle is actuated by pumping up and down, which operates a ratcheted mechanism attached to the actuating torque tube, enabling the gear to be extended. The landing gear cannot be retracted manually. Approximately 50 full travel cycles to the handle are required to extend and lock the landing gear.

A nose wheel steering mechanism is fitted to the nose landing gear. When the nose gear is down, direct linkage of this mechanism to the rudder pedals controls the nose wheel steering. The upper and lower portions of the shock struts connect with the torque knees. The torque knees allow strut compression and extension, but prevent rotation between the strut pistons and cylinders. On the nose gear assembly, the torque knees transmit steering motion to the nose wheel.

The  nose wheel  can be turned from 14° left of center to 12° right of center. When rudder pedal force is augmented by main wheel braking action, the nose wheel can be deflected up to 48° either side of center.

A spring-loaded shock link in the linkage damp- ens the transmission of excessive shock loads to the rudder pedals. This shock link also absorbs some of the force applied to the rudder pedals until the nosewheel is rolling. As the nosewheel begins rolling, steering resistance decreases and more pedal motion results in more nosewheel deflection. A shimmy damper diminishes nose- wheel shimmy 

Shimmy Damper

 

The shimmy damper is a balanced hydraulic cylinder, mounted on the right side of the nose gear strut. It bleeds fluid through an orifice to dampen nose wheel shimmy.

PTP  Beech 90 Series	B1	LOC	FOT	SGH	R/I	MEL	TS
	B2	LOC	FOT	SGH	R/I	MEL

321002 Main Gear Spring Assemblies - Examine for cracks, dents, corrosion, condition of
paint or other damage. Examine for chips, scratches, or other damage that lets corrosion
get to the steel spring. Examine the axles for condition and security.B 05-12-02 721, 722
321007 Inspect main landing gear axle.
322001 Nose Gear - Inspect torque links, steering rods, and boots for condition and security
of attachment. Check strut for evidence of leakage and proper extension.
Check strut barrel for corrosion, pitting, and cleanliness. Check shimmy damper and/or
bungees for operation, leakage, and attach points for wear and security.
322003 Nose Gear Fork - Inspect for cracks, general condition, and security of attachment.

C 05-12-04 720
322004 Nose Gear Attachment Structure - Inspect for cracks, corrosion, or other damage and security of attachment.
322006 Nose gear trunnion, steering assembly, torque link assembly, nose gear fork and
axle. Make sure you inspect these areas: 1. Nose gear trunnion surface. 2. Steering collar
and steering collar attach bolt. 3. Torque link, torque link attach pin and attach bolt. 4.

Nose gear fork. 5. Nose gear axle.
324001 Brakes - Test toe brakes and parking brake for proper operation.

B 05-12-02 230
324002 Brakes, Master Cylinders, and Parking Brake - Check master cylinders and parking
brake mechanism for condition and security. Check fluid level and test operation of toe and parking brake.
324003 Brake Lines, Wheel Cylinders, Hoses,Clamps, and Fittings - Check for leaks, condition, and security and hoses for bulges and deterioration. Check brake lines and hoses for proper routing and support.
324004 Tires - Check tread wear and general condition. Check for proper inflation.
324005 Wheels, Brake Discs, and Linings - Inspect,for wear, cracks, warps, dents, or other
damage. Check wheel through-bolts and nuts for looseness.
324006 Wheel Bearings - Clean, inspect and lube.

 SHIMMY DAMPER – SERVICING PROCEDURE

                               

(1) Remove the shimmy damper from the airplane.

(2) While you hold the damper in a vertical position with the fitting end pointed down, pull the fitting end of the damper shaft to its limit of travel.

(3) While you hold the damper in this position, fill the damper through the open end of the cylinder with hydraulic fluid.

(4) Push the shaft up slowly to seal off the filler hole.

(5) Clean the damper with solvent. Make sure that the shaft comes out through the filler hole until the damper is installed on the aircraft.

(6) Install the damper on the airplane.

Shimmy damper cleaning

(1) Clean the shimmy damper with a clean, lint-free cloth to prevent the collection of dust and grit.

(2) Make sure that the part of the damper piston shaft that you can see is always clean.

(3) Clean the machined surfaces of the shimmy damper.

(a) Use a clean, lint-free cloth soaked with hydraulic fluid to clean the machined surfaces.

(b) After the surfaces are clean, remove the remaining hydraulic fluid from them with a clean, lint-free cloth.

Shimmy Damper Servicing (On Airplanes with the Lord Shimmy Damper)

                 Lord Shimmy Dampers do not need special servicing. However, you must lubricate the nose wheel shimmy damper pivots with general purpose oil MIL-L-7870.

 Shimmy damper cleaning

(1) Clean the shimmy damper with a clean, lint-free cloth to prevent the collection of dust and grit.

(2) Make sure that the part of the damper piston shaft that you can see is always clean.

(3) Clean the machined surfaces of the shimmy damper with a clean, lint-free cloth to prevent the collection of dust and dust.

C. If necessary, exercise a shimmy damper before installation.

(1) If a shimmy damper has been in storage for a long period, make sure that it moves freely before you install

CAUTION: Make sure that you do not push or pull on the shaft of the shimmy damper after it has reached its limit in either the up or the down position. If you continue to push a fully

compressed, bottomed-out shaft, you can cause damage to the shimmy damper. If you

continue to pull on a fully extended shaft, you can cause damage to the shimmy damper.

(2) If the shimmy damper does not move freely, push and pull the shaft through complete cycles until it does move freely. When the shimmy damper shaft has come to its limit of travel up and down as you push and pull, make sure that you do not continue to push or pull it beyond that limit of travel