SD3-60 AIRCRAFT MAINTENANCE MANUAL

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Caroline Williams
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1 AMM PLATE BRAKES - DESCRIPTION & OPERATION 1. Description A. General Refer to Figure 1. This multi-piston type brake plate incorporates a heat pack comprising jigsaw type segmented rotor assemblies located between stator assemblies carrying inorganic pads. Automatic adjuster assemblies are fitted to maintain a pre-set working clearance as wear occurs in the heat pack, thus ensuring a constant fluid displacement. B. Torque plate and torque tube Radially disposed housings in the torque plate accommodate cylinder sub-assemblies which are interconnected by fluid passages. Further drillings provide for the attachment of a shuttle valve and bleed screws. The torque tube is bolted to the torque plate and has a series of equispaced integral tenons. C. Cylinder sub-assemblies A cylinder liner houses a piston which accommodates an automatic adjuster. The head of a retraction pin is located in an end plate which abuts the cylinder liner. The pin shank passes through an abutment tube and is gripped by a friction bush housed in a guide located within the piston. A set of disc springs is housed between the guide flange and a retaining tube which is secured to the piston by a wire circlip. An insulator is force fitted into the end face of the piston. Refer to Figure 2. D. Heat pack The heat pack comprises the pressure plate, one double and one single stator assembly and two rotor assemblies. Pads are riveted to the pressure plate and the single and double stators. Each rotor assembly comprises a series of jigsaw type segments interlocked to form a ring. Slots on their inner peripheries key the stators and pressure plate to the torque tube and tenon slots formed on the rotor segments engage drive blocks on the associated wheel. The complete heat pack is contained by a conical thrust ring secured to the end face of the torque tube. E. Wear indicator Two diametrically opposed wear indicators are screwed into the pressure plate and project through the torque plate. Refer to Figure 3. Page 1

2 SD3-60 AIRCRAFT MAINTENANCE MANUAL Brake Unit Assembly Figure 1 Page 2

3 Cylinder Sub-Assembly Details Figure 2 Page 3

4 SD3-60 AIRCRAFT MAINTENANCE MANUAL Wear Indicator Details Figure 3 Page 4

5 2. Operation When fluid in the cylinder assemblies is pressurised, the pistons move to apply a direct thrust to the pressure plate. The resultant clamping force between the pressure plate, stators, rotors and thrust ring imparts a retarding force to the rotors. When pressure is released the disc springs return the pistons to the brake off position. When the brake is applied, movement of the pistons compresses the disc springs. Primary movement is limited by the clearance between the retaining tube and the abutment tube. Any movement in excess of this (ie. during heat pack wear) draws the friction bush along the retraction pin. When the brake is released, the disc springs restore the clearance between the retaining tube and the abutment tube by withdrawing the pistons an amount equal only to the distance the springs were compressed. This distance is the correct working clearance for the brake and is thus maintained as the heat pack wears. Page 5

6 AMM PLATE BRAKES - TROUBLE SHOOTING 1. Trouble Shooting Sluggish response to operation of the brake controls Fault Cause Rectification Fluid seepage from a bleed point Fluid seepage from a cylinder sub-assembly Air in the hydraulic system Loose bleed screw Bleed the brake system. Torque tighten to 8 lb.ft. Damaged sealing ring (s) Renew sealing ring (s) -- return to overhaul base. NOTE: Where the rectification for a fault given in the above table involves testing or renewal of components, reference must be made to the appropriate Dunlop Component Maintenance Manual. Such faults are given to enable operators to decide whether to take line action or return the unit to an overhaul base. Page 101

7 AMM PLATE BRAKES AHA MAINTENANCE PRACTICES 1. Removal/Installation Refer to Figure 201 Special Tools & Equipment: Alignment Fixture : Pt. No. A15155 (Dunlop) CAUTION: ADEQUATE PRECAUTIONS MUST BE TAKEN TO PREVENT CONTAMINATION OF THE FRICTION FACES BY FLUIDS AND GREASES, DURING REMOVAL/ INSTALLATION. A. Remove a brake unit (1) Remove the wheel. Refer to , pb201. (2) Release the parking brake (if applied) (3) Exhaust main and emergency hydraulic pressure. Refer to , pb301. (4) Disconnect the two hydraulic pipes from the brake unit shuttle valve. Blank off connections. (5) Remove the five locknuts, washers and bolts from the brake attachment flange on the wheel lever and remove brake unit. NOTE: Operation (6) only applies if brake unit is unserviceable and has to be replaced. (6) Remove shuttle valve and discard 'O' rings. B. Install a brake unit NOTE: Operation (3) only applies if brake unit is not that which was previously removed (para A). (1) Place the brake unit cylinder block and associated caliper assembly in position on the brake flange on the wheel lever. (2) Align the attachment holes in the brake unit assembly with those in the flange. Grease the threads of the attachment bolts (Grease Spec. DTD.844/B). Fit the five bolts, washers and locknuts and torque tighten to 65 lb/ft. (3) Refit shuttle valve with new 'O' rings DAS (2 off) and torque tighten to 5 lb/ft. (4) Remove blanks, identify and connect the two hydraulic pipes to the brake unit shuttle valve. Torque tighten and witness mark. Refer to , pb1. (5) Bleed the normal and emergency lines to the brakes. Refer to , pb201. Page 201

8 SD3-60 AIRCRAFT MAINTENANCE MANUAL (6) With brakes released, correctly align the rotor assemblies by fitting the alignment fixture. Apply brakes and remove fixture. (7) Refit wheel. Refer to , pb201. (8) Perform function test. Refer to , pb201. (9) If unit is replacement, apply brakes and set protrusion of pad wear indicators as appropriate:- 2. Inspection/Check (a) New Heat Pack Set the wear indicators to.571 in. (14.5mm) and tighten the locknuts. (b) Part Worn Heat Pack A. Check pad wear Set the wear indicators to the dimension detailed on the brake unit transit label. (1) Check that emergency brake pressure is not less than 2000 psi. (2) Select brake EMERGENCY HYD control handle on left side of flight compartment centre console to EMERGENCY. (3) Select parking brake on and check that the brakes are applied. (4) Refer to Figure 202. Check protrusion of one or other of the two diametrically opposed wear indicators. WARNING: IF THE END OF AN INDICATOR IS FLUSH WITH THE FACE OF THE TORQUE PLATE, REMOVE THE BRAKE UNIT FROM THE AIRCRAFT FOR 'SCHEDULED REWORK' AS DETAILED IN DUNLOP COMPONENT MAINTENANCE MANUAL Page 202

9 Brake Unit - Removal/Installation Figure 201 Page 203

10 SD3-60 AIRCRAFT MAINTENANCE MANUAL Checking of Pad Wear Figure 202 Page 204

SD3-60 AIRCRAFT MAINTENANCE MANUAL & RETRACTION - DESCRIPTION & OPERATION

SD3-60 AIRCRAFT MAINTENANCE MANUAL & RETRACTION - DESCRIPTION & OPERATION AMM 17.0.0.0EXTENSION & RETRACTION - DESCRIPTION & OPERATION 1. Description A. General The landing gear is extended and retracted by the operation of a hydraulic actuator at each of the main and nose gear