Wheel and Brake Pesawat GC 680 FL

Prepared by :Ref. Used : Aircraft Maintenance Manual Pesawat Grand Commander 680 FL

SECTION VI

Topics of DiscussionGeneral and DescriptionMain Wheel Removal and DisassemblyMain Wheel Reassembly and InstallationBrake Removal and DisassemblyBrake Reassembly and InstallationBrake Lining WearBrake and Nose Wheel Steering Cylinder Bleeding ProcedurePower Brake Valve AdjustmentNose Wheel Removal and DisassemblyNose Wheel Reassembly and InstallationEmergency Braking System

General and DescriptionGood years wheel and brakes are used on the aircraft.Single disc hydraulic brakes are located on the wheels of the main landing gear are indiviually controlled by toe pressure on the top of either of rudder pedals.Rudder pedal toe pressure opens the power brake valves to apply main hydraulic system pressure are desired.Power Brake valves are installed on the forward side of the forward cabin bulkhead immediately in front of the pilots rudder pedals.Emergency braking system use in the event of a main hydraulic system malfunction. If the system pressure drops below 500 (± 30) psi, a pressure sensitive switch installed in the main hydraulic system supply line, senses the main system pressure and closes to energize the auxiliary hydraulic system pump which builds the system pressure up to 575 (± 30) psi.Single disc brakes contain a self-adjusting mechanism which maintains proper brake clearance at all times to increase lining life and assure a free turning wheel.

Main Wheel Removal and Disassembly

a. Jack aircraft.b. Remove hub cap (1), cotter pin, nut, washer

(12), and wheel assembly from landing gear.c. Remove outer bearing.d. Remove bearing lockring, bearing closure

ring (8), felt ring (9), and bearing from brake side of wheel.

e. Deflate tire.f. Remove lock nuts (15), washers (12), and

wheel half (5) retaining bolts and remove tire.NOTE : Bearing cups (4) are shrink fitted. Brake disc drive key screw are staked in the drive keys. Do not remove these parts unless necessary.g. Clean all parts throughly in a cleaning fluid,

Federal Spesification P-D-680, paying special attention to bearing cones and felt ring.

h. Inspect all parts for cracks, corrosion, or other evidance of wear.

Main Wheel Reassembly and Installation

a. Lubricate wheel seals with grease and position seals on wheel flanges.

b. Position tire on one wheel half, then position other wheel half on tire, beiang careful not to remove grease from wheel seals when positioning wheel halves, as grease acts as an air seal.

c. Install wheel-half bolts, washers, and nuts. Tighten nuts evenly and torque to 18 foot-pounds.

d. Lubricate end of inflating needle with glycerine.

e. Throughly lubricate tire inflation valve marked with small blue dot sidewall of tire with glycerine.

f. Insert inflating needle into tire inflation needle. If needle does not enter easlu, additional lubrication is required.

g. Over inflate tire to 60 psi to seat tire beads, then air pressure to 50 psi.

h. Remove inflating needle.

Brake Removal and Disassembly

a. Jack Aircraft.b. Deflate tire and remove wheel from landing gear.c. Disconnect and cap brake hydraulic line at brake. Remove bolts attaching brake assembly to axle

torque flange.d. Remove brake disc (2) and brake lining from brake housing (3).e. Remove cylinder head(12) and piston assembly from brake housing (3).f. Remove locknut (16) and threaded bushing (15).g. Place cylinder head and piston assembly in arbor press and press self-adjusting pin (6) through

split collar grip (14) using a 3/16 inch diameter smooth pin.h. Remove split collar grip (14), adjusting pinwasher (13), and O-ring seals (10 and 11) from cylinder

head (12).i. Remove piston assembly spring retainer plate (9), brake release springs (7 and 8) and self-

adjusting.j. Remove round head bleeder screw, washer, valve, adapter, and gasket.k. Clean all parts throughly in cleaning solveny Federal Specification P-D-680, paying special

attention to O-ring grooves.l. Inspect all parts for cracks, corrosion, or other evidance of wear.

Brake Reassembly and Installation

a. Place brake release spring (7 and 8) and self-adjusting (6) in piston (5) and replace spring retainer plate (9).

b. Lubricate self-adjusting pin (6) and O-ring (11) with hydraulic fluid and install in groove of cylinder head (12).

c. Place adjusting pin washer (13) and split collar grip ( 14) in cylinder head (12) and screw threaded bushing (15) into cylinder head (12).

d. Using an arbor press, force adjusting pin (6) through collar grip (14) and through threaded bushing (15).e. Lubricate O-rings (4 and 10) with appropriate hydraulic system fluid and install on piston (5), and cylnder

head (12).f. Screw threaded bushing (15) into cylinder head (12) until tight then back off 1/8 turn, hold and tighten

locknut (16) 1/3 turn to lock threaded bushing (15).g. Screw piston and cylinder head assembly into brake housing (3) until cylinder head (12) is flush (±0.015)

inch with brake housing (3).h. Replace round head bleeder screw, washer, plug, adapter, and gasket.i. Install brake linings (1) in place on anvil and piston side of brake respectively.j. Place brake disc (2) between linings.k. Install brake on axle torque flange and torque bolts to 100-140 inch-pounds.l. Connect hydraulic line to brake housing.m. Install wheel on main landing gear.n. Bleed brakes as outlined in this section under brake and nose gear steering cylinder bleeding procedure.

Brake Lining WearTo measure brake lining wear proceed as follows:a. Place master switch in BATTERY position.b. Depress brake pedals and engage parking brake.c. Place master switch in OFF position.d. Measure the distance between inboard surface of brake disc and flat surface

of brake housign that parallels the disc . When a 3/16 inch feeler gage may be inserted between the two surfaces the completeset of brake lining must than 3/16 inch, visually check the thickness of less than 1/16inch, all linings should be replaced.

e. If the above measurement is less than 3/16 inch visually check the thickness of less than 1/16 inch, all linings should be replaced.

Brake and Nose Wheel Steering Cylinder Bleeding

Procedurea. Fill hydraulic reservoir with clean fluid and keep filled through the procedure to

prevent air from entering the system.b. Remove bleeder screw and washer from bottom of brake housing and install a

bleeder hose in the adapter.c. Place free end of hose in a clean glass receptacle containing enough hydraulic

fluid to cover end of hose.d. Apply brakes and open bleeder adapter when fluid starts to flow frombleeder

hose. Aplly and hold brake pressure to slowly force fluid out bleeder adapter.Crimp bleeder hose and close bleeder adapter before releasing toe pressure from brake pedal.

e. Repeat step d. Until air bubbles are no longer emmited from bleeder hose.f. Remove hose and install bleeder screw and washer.g. Fill hydraulic reservoir to FULL mark on dipstick with appropriate hydraulic

fluid.h. Loosen line to forward side of nose gear steering cylinder just enough to allow

fluid to seep out. Apply brake pressure slowly on left rudder pedal and hold. Tighten forward line before allowing pedal to return to “brakes off” position.

i. Repeat step h. Until no more air escapes from steering cylinder.j. Repeat steps h. And i. Loosening aft line and applying brake pressure to right

rudder pedal.k. Fill hydraulic reservoir to FULL mark on dipstick with appropriate hydraulic

fluid.

Power Brake Valve Adjustment

To adjust the power brake valve, proceed as follows.a. Bleed brakes and nose gear steering cylinder as outlined in this section

under Brake and Nose Wheel Steering Cylinder Bleeding procedure.b. Remova cap from tee fitting installed in brake line immediately above each

main landing gear brake. Install a hydraulic pressure gage with a 0-2000 psi range at each tee.

c. Build up hydraulic system pressure to 1000 psi, using an auxiliary hydraulic power unit.

d. Remove access door ocated on lower left side of fuselage at station 5.50.e. Turn pressuring screw clockwise until an indication of pressure is shown

on gage in respective main wheel brake line.f. Turn power brake valve pressure adjusting screw counterclockwise slowly

until pressure on brake line gage drops to zero, then back adjusting screw off one complete turn.

g. Move power brake valve yoke as far aft on operating and extention leversas possible and tughten to prevent slilppage.

h. Assume a normal flight position in pilots seat and apply maximum foot pressure to both brake pedals. Note pressure obtained on gage in each brake line. Minimum allowable brake pressure is 400 psi.

i. Remove pressure gages at each brake line and cap tee fittings.j. Install accesss door and bleed brakes and nose gear steering cylinder.k. Fill hydarulic reservoir to FULL mark on dipstick.

Nose Wheel Removal and Disassembly

a. To remove and disassemble the nose wheel, proceed as follows:Jack aircraft in accordance with instructions contained in Section II

b. Remove axle bolt nut, axle bolt, and plugs.c. Slide axle out of fork assembly.d. Remove nose wheel assembly and spacers.e. Remove bearing seals and bearing cones.f. Deflate tireg. Remove wheel half retainer bolts.h. Separate wheel halves and remove tirei. Inspect bearing cups and replace if cups are damaged or worn. If necessary to remove

bearing cups, heat wheel half in boiling water for at least 30 minutes, then remove cup by tapping evenly. To install cup, heat wheel half again and cool bearing cups with dry ice. Position cup and tap lightly to assure proper seating. Thoroughly clean wheel half and repaint with two coats of zinc chromate and two coats of lacquer of the correct color

NOTEWhen nose wheel only is to be removed, tail of aircraft may be lowered to the ground and work performed with aircraft in this attitude

Nose Wheel Reassembly and Installation

Prior to installing the tire and tube, check wheel halves for cracks, nicks, or gauges. Replace cracked wheel halves. Polish small nicks and gauges with fine emery paper. Repaint areas where protective coating has been removed, or where there is evidence of corrosion, with two coats of aluminum lacquer. Check and replace bearing cups if damaged or worn. Wash bearing cones thoroughly in cleaning fluid, Federal Specification P-D680 and inspect for wear and damage. Repack bearing cones with bearing grease and reinstall. Check bearing rings for damage or distortion.

CON’TTo install tubeless sidewall inlated tires, proceed as follows:a. Lubricate wheel seals with grease and position seals on wheel flanges.b. Position tire in wheel half, then position other wheel half on tire being careful not to remove grease from wheel seals when positioning wheel halves, as grease acts as an air seal.c. Install wheel half retainer bolts, washer, and nuts, tighten nuts evenly and torque to 82 inch-pounds

d. Lubricate end of inflating needle with glycerine.e. Thoroughly lubricate the tire inflation valve, marked with a small blue dot in sidewall of tire, with glycerine.f. Insert inflating needle into tire inflation valve, using a rotating motion. Do not force inflating needle. If needle does not enter easly additional lubrication is required.g. Overinflate tire enough to seat tire beads, then reduce air pressure to 30 psi.h. Remove inflating needle. During cold weather tire inflation valve will sometimes fail to close immediately after removing inflating needle. This may be remedied by sharply jarring tire inflation valve with fist, immediately after removing inflating needle.

Emergency Braking SystemThe emergency braking system consists of an emergency supply of hydraulic fluid, an electrical motor driven auxiliary hydraulic system pump, and a hydraulic pressure sensing switch. These units are located in the outboard side of the left wheel well. In the event of a hydraulic system fluid leak, the engine driven hydraulic pumps may pump all but 0.80 quarts of fluid supplies only the auxiliary hydraulic system pump. The hydraulic pressure sensing switch is calibrated to turn the pump on should hydraulic pressure fail below 500 (± 30) psi and turn the pump off when hydraulic pressure reaches 575 (± 30) psi. When the master switch is place in the BATTERY position prior to starting the engines, the sensing switch closes a relay, which complete a circuit to energize the auxiliary hydraulic system pump to provide pressure for intermediate use of the brakes and flaps. Should a hydraulic system failure occur during flight, the auxiliary hydraulic system pump automatically maintains auxiliary hydraulic system pressure within 470 to 605 psi for brake and flap operation during landing.