Disassembly

These procedures consist of a detailed step-by-step processes to disassemble the main rotor hub assembly to the level necessary for restoration (overhaul). If main rotor hub is being disassembled for replacement of defective component(s) instead of restoration (overhaul), disassemble only to the extent necessary to replace defective parts.

Preliminary Requirements

Support equipment

Bearing Splitter

Bearing Puller

Socket Wrench

Main Rotor Grip Retainer Dowel

Pitch Horn Trunnion

Trunnion Bearing Pressing Plate

Trunnion Bearing Pressing Plug

Safety conditions

Review Airworthiness Limitations Schedule. Components that are scheduled for retirement shall be removed from service.

If accompanying records and/or physical appearance of hub indicate components have been subject to an accident or incident such as overspeed, overtorque, or sudden stoppage, the following steps prior to disassembly.

If the following evaluation requires the replacement of any part, also replace both tension-torsion straps, both strap pins, and both strap bolts.

Carefully inspect all detail parts visually for any apparent damage or abnormal appearance. Visual defects that are cause for replacing the entire hub include the following:

1. Pitch horn pulled from grip.

2. A segment of sheared mast attached to trunnion.

3. Obvious deformation of any other detail part within the hub would cause only the part that is deformed to be replaced along with both tension-torsion straps, both strap pins, and both strap bolts.

Main Procedures

Main Rotor Hub Support

Put the main rotor hub assembly on the Main rotor hub support supporting the grips with two pieces of wood, approximately 2 x 4 x 10 inches (51 x 102 x 254 mm).

Blade Bolt Assembly Removal

1.Remove nuts, washers, and blade bolts from each grip.

Blade Bolt Disassembly

1. Remove caps from blade bolts and remove balance weights. Retain weights for future use during rebalancing of hub and blade assembly. Discard packings.

DO NOT EXCEED THE MAXIMUM ALLOWABLE TEMPERATURE WHEN YOU HEAT A PART OR DAMAGE TO THE PART MAY OCCUR.

1. Heat the blade bolt in the area of the plug to a maximum of 200°F (93°C) and remove the plug with an aluminum or wood drift.

Blade Grip and Pitch Horn Assembly Removal

DO NOT ALLOW GRIPS OR YOKE TO ROTATE ON PITCH CHANGE AXIS. IF GRIP OR YOKE IS ALLOWED TO ROTATE ON THE PITCH CHANGE AXIS BEYOND 90°, REPLACE MAIN ROTOR GRIP RETENTION STRAPIS. USE T-HANDLE WORKAID OR LOCKWIRE TO SECURE GRIPS.

1. Make sure grips and yoke are secured to prevent rotation.

2. Remove latch nuts and blade latches.

3. Remove strap bolt nuts with Socket Wrench (T101554) then remove washers and strap bolts. Discard the strap bolts if they have reached their retirement life.
4. Remove pitch horn nuts, washers, and bolts.

5. Remove grips and pitch horns from yoke. Do not allow hub weight to rest on wear sleeves. Support yoke with pieces of wood.

Blade Grip Disassembly

1. Make sure grips are secured to prevent rotation.

2. Insert Main Rotor Grip Retainer Dowel (Workaid) into retainer.
3. Rock dowel to break sealant around retainers. Remove retainers from grips.

4. Remove excluders and packings from retainers.

5. Thoroughly heat grips with a heat lamp.

6. Remove bearings and spacers from each grip.

7. Remove closures, two buffer pads, and spot decals from each grip. Do not remove blade bolt bushings or pin.

Pitch Horn Disassembly

1. Remove relief valve from pitch horn.

2. Remove retaining nuts and washers from bolts retaining pitch horn trunnion.

3. Insert tangs of Pitch Horn Trunnion (Workaid) into pitch horn slot and tighten screw until trunnion bolts and trunnion can just be pulled out. Immediately release screw tension and remove trunnion workaid.
4. As an alternate method, insert a phenolic wedge in pitch horn slot just far enough to remove trunnion bolts and trunnion.

5. Using care to prevent damage to pitch horns, press seals from horns.

Pillow Block and Trunnion Removal

1. Remove pillow block nuts and washers from inboard side of yoke.

2. Remove bolts, washers, shims, and bushings from each pillow block.

3. Remove grease fittings from pillow blocks.

4. Using a soft faced plastic mallet, tap pillow blacks from yoke and trunnion.

5. Remove trunnion from yoke.

Pillow Block Disassembly

1. Fabricate a pressure block from 0.25 to 0.50 inch (6.35 to 12.7 mm) phenolic, approximately 1.50 to 1.75 inches (38.1 to 44.5 mm) in diameter.

2. Place pressure block in bottom of pillow block.

3. Insert Bearing Puller (T101491) into pillow block with jaws contacting inside surface of seal by use of adjusting screw.
4. Tighten pulling screw until seal clears pillow block.

5. Invert pillow blocks on workbench and apply heat lamp.

6. When pillow blocks are heated, tap face of pillow blocks on a hard wood surface to remove bearings.

7. Remove and discard pillow block pads.

Trunnion Disassembly

1. Using a 1/4 inch hexagon wrench, turn adjusting screws clockwise to drive wear disc and thrust washers from journal ends of trunnion. Discard packings from thrust washers.

2. Continue turning adjusting screws until threads clear trunnion.

3. Using a sharp plastic scraper, remove sealant from radius groove around trunnion and inboard end of bearing race.

Make sure pressing plate fits snug to bearing inner race and sufficient clearance is available to allow plate to clear spindle of trunnion.

1. Position Trunnion Bearing Pressing Plate around trunnion at inboard end of bearing inner race.
2. Position trunnion in hydraulic press. Support bearing press plate with support blocks across parting line of pressing plate.

DO NOT PERMIT TRUNNION TO DROP WHEN TRUNNION SPINDLE CLEARS INNER RACE

During pressing operation, make sure pressing plate does not damage spindle of trunnion.

1. Insert pressing plug into journal end of trunnion and press trunnion from bearing inner race.

Yoke Disassembly

1. Remove nuts, washer, retainer, and balance washers.

2. Remove static stop bolts and washers.

3. Remove static stops, rubber stops, and laminated shims.

4. Using a sharp plastic scraper, trim sealant from around inboard end of strap fitting and surface of yoke.

If bond cannot be broken with hand pressure, insert a 0.50 inch (12.7 mm) wooden dowel into yoke journal against strap fitting and lightly tap from yoke.

1. With hand pressure, push tension-torsion straps inboard in yoke to break sealant bond.

2. Remove strap pins , radius rings, strap fittings, and tension-torsion straps.

3. Remove strap pins , radius rings, strap fittings, and tension-torsion straps.

4. Press wear sleeves off yoke. Inspect yoke for possible damage resulting from wear sleeve removal.