HANDBOOK OF MAINTENANCE INSTRUCTIONS FOR MDHI 369D/E/FF-500/600N HELICOPTERS (ISSUED: 1990)

CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

9. Vertical Stabilizer Torque Tube

(2). Apply one layer of teflon tape (CM726)

Replacement

to threads of torque tube prior to

installing locknut.

A. Vertical Stabilizer Torque Tube Removal

(3). Install locknut, hand tighten and adjust

(1). Remove vertical stabilizers (Ref.

to a 0.005-0.010 inch (0.127-0.254 mm)

Vertical Stabilizer Replacement).

gap; Install cotter pin.

NOTE: When installing the bellcrank, opening

(2). Remove horizontal tip plate access

in bellcrank must face outboard.

cover and disconnect YSAS torque tube

(if installed) from vertical stabilizer

(4). Install bellcrank, with opening facing

bellcrank.

outboard, on torque tube and install

expandable bolt; Torque to 30 - 40

(3). Remove bellcrank from torque tube by

inch-pounds (3.39 - 4.52 Nm) plus

removing expandable bolt.

drag torque; Install cotter pin.

(4). Remove cotter pin, locknut and bushing

(5). Connect YSAS actuator to vertical

from torque tube. Remove torque tube

stabilizer torque tube bellcrank. Torque

by lifting upward.

nut to 30 - 40 inch-pounds (3.39 -

4.52 Nm) and install cotter pin.

B. Vertical Stabilizer Torque Tube

Installation

(6). Install end plate access covers.

(1). Slide torque tube from the top thru the

(7). Install vertical stabilizer (Ref. Vertical

horizontal stabilizer.

Stabilizer Replacement).

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CSP-HMI-2

MAINTENANCE MANUAL

10. Horizontal Stabilizer Repair

4.52 Nm) plus drag torque; Install

cotter pin.

Refer to MDHI Field Service Representative.

(10). Connect YSAS actuator to vertical

stabilizer torque tube bellcrank. Torque

11. Vertical Stabilizer Torque Tube and/or

nut to 30 - 40 inch-pounds (3.39 -

Bushing Replacement (Non−Bonded

4.52 Nm) and install cotter pin.

Bushings)

(11). Install end plate access covers.

(Ref. Figure 201) The following procedure is for

replacing the early style (non-bonded) torque

(12). Install vertical stabilizer (Ref. Vertical

tube bushings.

Stabilizer Replacement).

12. Vertical Stabilizer Torque Tube and/or

Consumable Materials

Bushing Replacement (Bonded Bushings)

(Ref. Section 91−00−00)

Item

Nomenclature

(Ref. Figure 201) The following procedure is for

CM726

Tape, teflon

replacing the current style (bonded) torque

tube bushings.

(1).

Remove vertical stabilizers (Ref.

Consumable Materials

Vertical Stabilizer Replacement).

(Ref. Section 91−00−00)

Item

Nomenclature

(2).

Remove horizontal tip plate access

cover and disconnect YSAS torque tube

CM222

1,1,1-Trichloroethane

(if installed) from vertical stabilizer

CM402

Adhesive

bellcrank.

CM726

Tape, teflon

CM802

Abrasive cloth, aluminum oxide

(3).

Remove bellcrank from torque tube by

removing expandable bolt.

(1). Remove vertical stabilizers (Ref.

(4).

Remove cotter pin, locknut and bushing

Vertical Stabilizer Replacement).

from torque tube. Remove torque tube

by lifting upward.

(2). Remove horizontal tip plate access

cover and disconnect YSAS torque tube

(5).

Remove bushing from bearing race of

(if installed) from vertical stabilizer

torque tube.

bellcrank.

(6).

Install one bushing on bearing race of

(3). Remove bellcrank from torque tube by

torque tube and insert torque tube

removing expandable bolt.

through fitting of horizontal stabilizer

(4). Remove cotter pin, locknut and bushing

from the top downward.

from torque tube. Remove torque tube

(7).

Apply one layer of teflon tape (CM726)

by lifting upward.

to threads of torque tube prior to

In the following steps, care must

installing locknut.

CAUTION

be taken to not damage the fi

bers of the horizontal stabilizer.

(8).

Install bushing and locknut, hand

tighten locknut and adjust to a

(5). Remove bushing(s) from horizontal

0.005-0.010 inch (0.127-0.254 mm)

stabilizer by gently working a sharp

gap; Install cotter pin.

scraper between bushing and stabilizer.

NOTE: Ensure shouldered bushings are

(6). Sand excess sealant from horizontal

installed in bellcrank.

stabilizer taking care not to disturb the

composite fibers of the stabilizer.

(9). Install bellcrank on torque tube and

install expandable bolt and washers;

(7). Clean faying surfaces of horizontal

Torque to 30 - 40 inch-pounds (3.39 -

stabilizer, where bushings are to be

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CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

bonded, with 1,1,1-trichloroethane

13. Vertical Stabilizer Torque Tube Bushing

(CM222).

Rework (Non−Bonded Bushings to

Bonded Bushings)

(8). Wipe dry using a clean dry rag and

then allow to air dry for 15 minutes.

(Ref. Figure 201) The following procedure is for

converting the vertical stabilizer torque tube to

(9). Lightly abrade the faying surface of the

the current 500N3980-3 bushings,

new bushings with abrasive cloth

500N3970-3 locknuts and MS24665-361

(CM802) until all gloss is removed.

cotter pins.

Wipe clean with 1,1,1-trichloroethane.

(10). Wipe dry using a clean dry rag and

Consumable Materials

then allow to air dry for 15 minutes.

(Ref. Section 91−00−00)

Item

Nomenclature

(11). Mix adhesive (CM402) according to

CM222

1,1,1-Trichloroethane

manufacturers instructions. Apply

CM402

Adhesive

adhesive within 2 hours of cleaning.

CM726

Tape, teflon

(12). Apply a thin uniform layer of adhesive

CM802

Abrasive cloth, aluminum oxide

to faying surfaces.

Do not apply too much pressure,

(1).

Remove vertical stabilizers (Ref.

CAUTION

damage to horizontal stabilizer

Vertical Stabilizer Replacement).

may occur.

(2).

Remove cotter pins, locknuts and

(13).

Press the faying surfaces firmly

bushings, and scrap. Remove torque

together and maintain contact pressure

tube by lifting upward. Remove bushing

or apply 50 psi (3.45 kPa) maximum for

and scrap.

24 hours at ambient temperature.

(3).

Clean faying surfaces of horizontal

stabilizer, where bushings are to be

(14).

Using 1,1,1-trichloroethane, clean

bonded, with 1,1,1-trichloroethane

excess adhesive from parts before

(CM222).

adhesive has had time to cure.

(4).

Wipe dry using a clean dry rag and

(15).

Slide torque tube from the top thru the

then allow to air dry for 15 minutes.

horizontal stabilizer.

(5).

Lightly abrade the faying surface of the

(16).

Apply one layer of teflon tape (CM726)

new bushings with abrasive cloth

to threads of torque tube prior to

(CM802) until all gloss is removed.

installing locknut.

Wipe clean with 1,1,1-trichloroethane.

(17).

Install locknut, hand tighten and adjust

(6).

Wipe dry using a clean dry rag and

to a 0.005-0.010 inch (0.127-0.254 mm)

then allow to air dry for 15 minutes.

gap; Install cotter pin.

(7).

Mix adhesive (CM402) according to

(18).

Install bellcrank on torque tube and

manufacturers instructions. Apply

install expandable bolt; Torque to 30 -

adhesive within 2 hours of cleaning.

40 inch-pounds (3.39 - 4.52 Nm)

plus drag torque; Install cotter pin.

(8).

Apply a thin uniform layer of adhesive

to faying surfaces.

(19).

Connect YSAS actuator to vertical

stabilizer torque tube bellcrank. Torque

Do not apply too much pressure,

CAUTION

nut to 30 - 40 inch-pounds (3.39 -

damage to horizontal stabilizer

4.52 Nm) and install cotter pin.

may occur.

(9). Press the faying surfaces firmly

(20).

Install end plate access covers.

together and maintain contact pressure

(21).

Install vertical stabilizer (Ref. Vertical

or apply 50 psi (3.45 kPa) maximum for

Stabilizer Replacement).

24 hours at ambient temperature.

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CSP-HMI-2

MAINTENANCE MANUAL

(10).

Using 1,1,1-trichloroethane, clean

(a). Locate a steel plate of approximately

excess adhesive from parts before

0.250 inch (6.35 mm) thickness.

adhesive has had time to cure.

(b). Drill a 1.510 inch (38.3540 mm) hole

in the plate.

(11).

Slide torque tube from the top thru the

horizontal stabilizer.

(c). Deburr edges of hole to prevent

damage to torque tube.

(12).

Apply one layer of teflon tape (CM726)

to new 500N3970-3 locknut.

(d). Apply tape (CM730) to tool to prevent

damage to bearing race.

(13).

Install locknut, hand tighten and adjust

to a 0.005-0.010 inch (0.127-0.254 mm)

(4). Insert torque tube through the removal

gap; Install MS24665-361 cotter pin.

tool and install on arbor press.

In the following steps, care must

(14).

Install bellcrank on torque tube and

CAUTION

be taken to not damage the hori

install expandable bolt; Torque to 30 -

zontal stabilizer torque tube.

40 inch-pounds (3.39 - 4.52 Nm)

plus drag torque; Install cotter pin.

(5). Place suitable device over torque tube

end to protect tube from damage from

(15).

Install end plate access covers.

arbor press.

(16).

Install vertical stabilizer (Ref. Vertical

(6). Remove bearing from the torque tube

Stabilizer Replacement).

by gently pressing torque tube through

the removal tool.

14. Vertical Stabilizer Torque Tube Bearing

Race Replacement

(7). Using solvent (CM234), clean primer

residue from torque tube.

(Ref. Figure 201) The following procedure is for

(8). Inspect torque tube for damage to

removal of the bearing race from the vertical

bearing race contact surface.

stabilizer torque tube. Some special tools will

need to be manufactured for this procedure.

(9). Fabricate the following tool for bearing

race installation.

Consumable Materials

(a). Locate a steel plate of approximately

(Ref. Section 91−00−00)

0.250 inch (6.35 mm) thickness.

Item

Nomenclature

(b). Drill a 1.390 inch (35.306 mm) hole

CM234

Solvent, dry-cleaning

in the plate.

CM318

Primer

CM730

Tape, duct

(c). Deburr edges of hole to prevent

damage to torque tube.

Special Tools

(d). Apply tape (CM730) to tool to prevent

(Ref. Section 91−00−00)

damage to bearing race.

Item

Nomenclature

(10). Insert bearing race into tool and mount

N/A

Arbor press

on arbor press.

(11). Coat torque tube bearing race mating

(1). Remove vertical stabilizers (Ref.

surface with primer (CM318).

Vertical Stabilizer Replacement).

In the following steps, care must

(2). Remove vertical stabilizer torque tubes

CAUTION

be taken to not damage the the

(Ref. Vertical Stabilizer Torque Tube

horizontal stabilizer torque tube.

Replacement).

(12). Place suitable device over torque tube

(3). Fabricate the following tool for bearing

end to protect tube from damage from

race removal.

arbor press.

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MD Helicopters, Inc.

MAINTENANCE MANUAL

In the following step, ensure

ensure no warpage occurred during

CAUTION

bearing race is not cocked on

installation.

torque tube, this will cause non-repairable

(15). Reinstall vertical stabilizer torque

damage to bearing race and torque tube.

tubes (Ref. Vertical Stabilizer Torque

Tube Replacement).

(13). While primer is wet, press torque tube

down through the bearing race until

(16). Reinstall vertical stabilizers (Ref.

bearing race is tight against flange on

Vertical Stabilizer Replacement).

torque tube.

15. Stabilizer Troubleshooting

(14). Inspect bearing race flanged surface to

(Ref. Table 201)

Table 201. Troubleshooting Tailboom and Tail Surfaces

Symptom

Probable Trouble

Corrective Action

High frequency vibration

Fan assembly out of balance

Re−balance fan assembly.

Loose fan blades

Replace and re−balance fan assy.

Loose bolts/nuts on Horizontal or

Inspect mounting hardware; adjust or

Vertical stabilizer

replace as necessary.

NOTE: High frequency vibrations in helicopter can be caused by components in other systems (Ref. Sec.

64−00−00, 63−25−10, 63−25−30 and 71−00−00).

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CSP-HMI-2

MAINTENANCE MANUAL

TABLE OF CONTENTS

Para/Figure/Table

Title

Page

62-00-00 Main Rotor (369D/E/FF - 500/600N)

Fault Isolation

101

1. Main Rotor System - General Information

101

2. Main Rotor System Troubleshooting

101

Table 101. Troubleshooting Main Rotor Vibrations

102

62-10-00 Main Rotor Blade (369D/E/FF - 500/600N)

Removal/Installation

401

1. Main Rotor Blade - General

401

A. Main Rotor Blade Leading Edge Erosion Protection - General

401

2. Main Rotor Blade Replacement

401

A. Main Rotor Blade Removal

401

B. Main Rotor Blade Installation

401

3. Main Rotor Blade and Damper Attach Pin Installation and Adjustment

401

Figure 401. Main Rotor Blade - Attachment and Outboard End

403

Inspection/Check

601

1. Main Rotor Blade Inspection

601

Figure 601. Main Rotor Blade Damage and Repair Limits - Nicks,

Scratches, Gouges and Cracks

603

2. Main Rotor Blade and Damper Attach Pin Inspection and Corrosion

Protection

604

3. Main Rotor Blade and Damper Attach Pin Disassembly and Special

Inspection

605

4. Main Rotor Blade Forward Tip Cap Inspection and Corrosion Protection

605

5. Main Rotor Blade Upper and Lower Root Fitting Attach Lug and Lead-Lag

Link Attach Lug Inspection (25 Hour)

605

Figure 602. Main Rotor Blade Damage Limits for Dents and Depressions

606

Figure 603. Main Rotor Blade Attach Pin

607

6. Main Rotor Blade Upper and Lower Root Fitting, Attach Lug and Lead-Lag

Link Attach Lug Inspection (100 Hour)

608

7. Main Rotor Blade Leading Edge Abrasion Strip Check

610

8. Main Rotor Blade Torque Event Inspection

610

Figure 604. Main Rotor Blade Root Fitting, Attach Lugs and Lead-Lag Link

Assembly Inspection

611

Figure 605. Application of Slippage Mark to Main Rotor Blade Bushings and

Root Fittings

612

Repairs

801

1. Main Rotor Blade Repair (Nicks, Scratches and Wear Spots)

801

2. Main Rotor Blade Repair (Dents, Depressions and Erosion)

801

Page i

62 Contents

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CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

TABLE OF CONTENTS (Cont.)

Para/Figure/Table

Title

Page

3. Trim Tab Damage Repair

802

4. Forward Tip Cap Threaded Insert Repair

802

Figure 801. Main Rotor Blade Trailing Edge Weight Rework

803

5. Loose Balance Weight Repair

804

6. Loose Trailing Edge Weight Repair

804

7. Loose or Missing Rivets or Aft Tip Cap Repair

804

Figure 802. Repair and Removal of Trim Tab, Main Rotor Blade

805

Figure 803. Bearing Replacement - Main Rotor Blade Damper Attach

Fitting

805

8. Damper Attach Blade Fitting Bearing Replacement

806

9. Leading Edge Protective Tape Replacement

806

Figure 804. Installation/Replacement of Stainless Steel Abrasion Tape

(Main Rotor Blade Leading Edge)

807

Figure 805. Installation/Replacement of Double Layer Abrasion Tape

(369D21100-505 and -509 Rotor Blades)

808

10. Leading Edge Abrasion Strip Sealing

809

11. Tip Cap Sealing

809

Figure 806. Main Rotor Blade Abrasion Strip and Tip Cap Sealing

810

12. Main Rotor Blade Protective Tape Installation

811

A. Stainless Steel Tape Installation

811

62-20-00 Main Rotor Hub (369D/E/FF - 500N)

Removal/Installation

401

1. Main Rotor Hub - General

401

2. Main Rotor Hub Replacement

401

A. Main Rotor Hub Removal

401

B. Main Rotor Hub Installation

401

Figure 401. Pulling Hub Assembly

403

3. Main Rotor Damper

404

4. Main Rotor Damper Replacement

404

A. Main Rotor Damper Removal

404

B. Main Rotor Damper Installation

404

5. Main Rotor Damper Nominal Adjustment

405

Figure 402. Main Rotor Hub - Installation

406

Inspection/Check

601

1. Main Rotor Hub Balancing - General

601

2. Main Rotor Blade Phasing Check and/or Adjustment

601

3. Main Rotor Hub Inspection

601

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MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

TABLE OF CONTENTS (Cont.)

Para/Figure/Table

Title

Page

Figure 601. Strap Pack Lamination - Exploded View

602

4. Lead-Lag Bolt Inspection

603

5. Main Rotor Strap Pack Lamination Inspection

603

Figure 602. Strap Pack Lamination Inspection (Sheet 1 of 2)

605

Table 601. Strap Pack Inspection

607

6. Main Rotor Hub Droop Angle Check

608

7. Main Rotor Damper and Attachments Inspection

608

8. Main Rotor Damper Weight Loading and Extension Check

609

Figure 603. Periodic Check of Main Rotor Damper Assembly

610

Repairs

801

Main Rotor Retention Strap Pack Repair

801

Pitch Housing Repair

801

Unbushed Outboard Clevis Lug Hole Repair

801

Figure 801. Field Repair of Main Rotor Hub Pitch Control Lugs

(Sheet 1 of 2)

802

Pitch Control Bearing Housing Assembly, Spacer or Striker Strip

Replacement

804

Pitch Control Bearing Housing Modification

805

Pitch Control Bearing Replacement

805

Figure 802. Main Rotor Hub Components - Repair and Installation

(Sheet 1 of 2)

806

Lead-Lag Link Blade Stop Replacement

808

Figure 803. Striker Strip Replacement

809

Damper Attach Lug Bearing Replacement

809

Lead-Lag Bolt Corrosion Control

810

10.

Pitch Control Bearing Pivot Pin Repair or Replacement

810

11.

Droop Stop Roller Repair or Replacement

810

12.

Droop Stop Ring Repair

811

13.

Droop Stop Ring Replacement

811

14.

Droop Stop Follower (T-Head) Replacement

811

15.

Droop Stop Plunger Removal, Inspection and Installation

812

16.

Main Rotor Hub Droop Angle Adjustment

812

Figure 804. Main Rotor Hub Assembly - Repair

813

17.

Main Rotor Hub Tapered Bearing Grease Repack, Inspection and

Replacement

814

18.

Main Rotor Hub Scissors Attach Lug Bearing Replacement

815

Figure 805. Main Rotor Hub - Cross Section (Sheet 1 of 2)

817

Figure 806. Tapered Bearing Tools - Main Rotor Hub (Sheet 1 of 2)

819

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CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

TABLE OF CONTENTS (Cont.)

Para/Figure/Table

Title

Page

62-20-60 Main Rotor Hub (600N)

Removal/Installation

401

1. Main Rotor Hub - General

401

2. Main Rotor Hub Replacement

401

A. Main Rotor Hub Removal

401

B. Main Rotor Hub Installation

401

Figure 401. Pulling Hub Assembly

403

3. Main Rotor Damper

403

4. Main Rotor Damper Replacement

404

A. Main Rotor Damper Removal

404

B. Main Rotor Damper Installation

404

5. Main Rotor Damper Nominal Adjustment

404

Figure 402. Main Rotor Hub Installation

405

Inspection/Check

601

1. Main Rotor System Balancing - General

601

2. Main Rotor Hub Inspection

601

Figure 601. Strap Pack Lamination - Exploded View

602

3. Lead-Lag Bolt Inspection

603

4. Main Rotor Strap Pack Lamination Inspection

603

Figure 602. Strap Pack Lamination Inspection (Sheet 1 of 2)

604

Table 601. Strap Pack Inspection

606

5. Main Rotor Hub Droop Angle Check

608

6. Main Rotor Damper and Attachments Inspection

608

7. Main Rotor Damper Weight Loading and Extension Check

609

Figure 603. Periodic Check of Main Rotor Damper Assembly

610

Repairs

801

1. Main Rotor Retention Strap Pack Repair

801

2. Pitch Control Bearing Housing Assembly, Spacer or Striker Strip

Replacement

801

Figure 801. Striker Strip Replacement

802

3. Lead-Lag Link Blade Stop Replacement

802

Figure 802. Main Rotor Hub Components Repair and Installation

803

4. Lead-Lag Bolt Corrosion Control

804

5. Pitch Control Bearing Pivot Pin Repair or Replacement

804

6. Droop Stop Roller Repair or Replacement

804

7. Droop Stop Ring Repair

805

8. Droop Stop Ring Replacement

805

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CSP-HMI-2

MAINTENANCE MANUAL

TABLE OF CONTENTS (Cont.)

Para/Figure/Table

Title

Page

9. Droop Stop Follower (T-Head) Replacement

805

Figure 803. Droop Stop Ring Replacement and Repair

806

10. Droop Stop Plunger Removal, Inspection and Installation

807

11. Main Rotor Hub Droop Angle Adjustment

807

12. Main Rotor Hub Tapered Bearing Grease Repack, Inspection and

Replacement

808

Figure 804. Tapered Bearing Tools - Main Rotor Hub (Sheet 1 of 2)

809

13. Main Rotor Hub Upper Bearing Grease Repack, Inspection and

Replacement

811

14. Main Rotor Hub Scissors Attach Lug Bearing Replacement

813

Figure 805. Main Rotor Hub - Cross Section

814

62-30-00 Swashplate and Mixer (369D/E/FF - 500N)

Removal/Installation

401

Main Rotor Swashplate

401

Swashplate Replacement

401

A. Swashplate Removal

401

B. Swashplate Installation

401

Mixer Controls

401

Mixer Controls Replacement

401

A. Mixer Controls Removal

401

Figure 401. Pitch Control Rods and Swashplate Scissors - Installation

402

B. Mixer Controls Installation

403

Figure 402. Mixer Controls - Assembly

404

Scissors

405

Scissors Replacement

405

A. Scissors Removal

405

B. Scissors Installation

405

Scissors Link Replacement

405

Pitch Control Rods

406

Pitch Control Rod Replacement

406

A. Pitch Control Rod Removal

406

B. Pitch Control Rod Installation

406

10. Counterweight and Interrupter Installation

406

Figure 403. Main Rotor Swashplate

407

Inspection/Check

601

1. Swashplate Inspection

601

2. Mixer Controls Inspection

602

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CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

TABLE OF CONTENTS (Cont.)

Para/Figure/Table

Title

Page

3. Scissors Inspection

602

4. Pitch Control Rod Inspection

602

Repairs

801

1. Swashplate Repairs

801

2. Mixer Controls Repair

801

3. Scissors Bushing and Bearing Replacement

801

4. Scissors Modification

802

Figure 801. Field Modification - 369D21002-11 Crank Assembly to

369D21002-21 Configuration

803

Figure 802. Installation of 369D21002-21 Crank to Hub Lower Shoes

804

5. Mixer Controls Rework

804

Figure 803. Rework of Main Rotor and Mixer Controls (Sheet 1 of 2)

806

62-30-60 Swashplate and Mixer (600N)

Removal/Installation

401

Main Rotor Swashplate

401

Swashplate Replacement

401

A. Swashplate Removal

401

B. Swashplate Installation

401

Figure 401. Pitch Control Rods and Swashplate Scissors - Installation

402

Controls Mixer

403

Controls Mixer Replacement

403

A. Controls Mixer Removal

403

B. Mixer Controls Installation

403

Figure 402. Controls Mixer - Assembly

404

Scissors

405

Scissors Replacement

405

A. Scissors Removal

405

B. Scissors Installation

405

Scissors Link Replacement

405

Pitch Control Rods

406

Pitch Control Rod Replacement

406

A. Pitch Control Rod Removal

406

B. Pitch Control Rod Installation

406

Figure 403. Main Rotor Swashplate

407

Inspection/Check

601

1. Swashplate Inspection

601

2. Mixer Controls Inspection

602

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MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

MAIN ROTOR

FAULT ISOLATION

1. Main Rotor System − General Information

NOTE: Unless specifically indicated in the text

and illustrations, information applies to all

NOTE: Auto-Rotation RPM charts are found in

model helicopters. Where information is

Chapter 18.

limited to a specific model helicopter or con

figuration, the text or effectivity block will

The main rotor located over the helicopter

indicate.

center-of-gravity provides lift, lateral and

longitudinal control. The fundamental

components of the rotor are five or six remov

2. Main Rotor System Troubleshooting

able blades, pitch housings and a hub. Each

articulated blade is controlled through a pitch

Sudden onset of excessive

WARNING

housing and link arrangement which transfers

and/or unusual main rotor

flight control inputs into the rotor blades.

vibration should be investigated imme

Rotor blades, pitch housings and links are

diately as to the cause, prior to contin

secured to the hub by five sets of laminated

ued flight. Under no circumstance

steel straps. The collective, stick working

should main rotor tracking be at

through linkages, increases or decreases rotor

tempted to correct the problem until a

blade angle affecting helicopter ascent and

thorough inspection of the main rotor

descent (collective pitch). Helicopter pitch and

blades, hub assembly and strap pack

roll angles are controlled by the cyclic stick.

assembly has been performed.

Mixed collective and cyclic control inputs are

simultaneously transferred into the main rotor

(1). First determine which major installa

for coordinated flight control. The four main

tion is defective.

equipment groups of the main rotor and

(2). Isolate each linkage installation from

control system are the rotor blades, hub, upper

others until area of malfunction is

exterior controls, and cyclic and collective

located.

controls in the pilot's compartment.

(1). Main rotor blades

(3). Investigate and determine exact

(Ref. Sec. 62-10-00).

location of malfunction.

(2). Main rotor hub

(4). Repair or replace defective components.

(Ref. Sec. 62-20-00 and 62-20-60).

NOTE: First indications of trouble are usually

(3). Main rotor swashplate and mixer

felt through cyclic or collective controls. Iso

(Ref. Sec. 62-30-00 and 62-30-60).

lation procedures (Ref. Table 101, Sec.

(4). Main rotor flight controls

67-10) indicate symptoms detected through

(Ref. Chap. 67).

these controls.

Page 101

62-00-00

Revision 20

CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

Table 101. Troubleshooting Main Rotor Vibrations

Symptom

Probable Trouble

Corrective Action

Unusual or excessive vibration.

Main rotor blades damaged.

Inspect blades

(Ref. Sec. 62−10−00).

Vertical or Lateral vibration.

Main rotor hub or hub components

Inspect main rotor hub assembly

damaged.

(Ref. Sec. 62−20−00/62−20−60).

Inspect strap pack assemblies.

One−per revolution lateral beat in

Defective damper or blade phasing.

Check damper nominal adjustment

hover and cruise. May also occur

(Ref. Sec. 62−20−00/62−20−60)

on ground during warmup or

Replace defective damper.

shutdown.

Five−per−revolution or

Worn pitch control bearings.

Replace pitch control bearings

medium−frequency beat.

(Ref. Chap. 67).

One−per revolution vertical beat.

Main rotor blades out of track.

Track main rotor blades

Beat may appear throughout

(Ref. Sec. 18−10−00/18−10−60).

entire flight regime, becoming

more pronounced at higher

airspeeds.

Lateral feedback (beat) in cyclic

Rotor blades out of track.

Track main rotor blades

control stick with no longitudinal

(Ref. Sec. 18−10−00/18−10−60).

feedback detected.

One−per−revolution lateral beat,

Main rotor blade tip balance weights

Check balance weights for security;

continuous.

not secure.

repair as necessary:

(Ref. Sec. 62−10−00).

Incorrect blade phasing.

Check main rotor track and balance

(Ref. Sec. 18−10−00/18−10−60).

High frequency vibrations.

Loose or defective component in

(Ref. Chaps. 18, 62, 64 and 67)

another system.

Main rotor track and/or balance

Play between longitudinal pitch mixer

Re−bond collective pitch mixer

inconsistant.

bellcrank and collective pitch mixer

bearings and install shims between

bellcrank.

longitudinal pitch mixer bellcrank and

collective pitch mixer bellcrank

bearings (Ref. Sec. 62−30−00 or

62−30−60).

Page 102

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MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

MAIN ROTOR BLADE

REMOVAL/INSTALLATION

1. Main Rotor Blade − General

etc). Detach damper clevis from blade.

Remove two blade fitting attaching

Each of the main rotor blades are a balanced

pins.

airfoil consisting primarily of a wraparound,

aluminum alloy skin bonded to an extruded

(3). If rotor system is not already color

aluminum alloy spar, an upper root fitting and

coded, use masking tape and/or grease

a lower root fitting (Ref. Figure 401). Two

pencil, to mark each blade and its

pre-set balance weights are installed in the tip

respective pitch housing links so that

end of each blade. A removable forward tip

blades can be reinstalled in same

cap, at the outboard end of each blade, is

relative positions.

replaced with a tracking cap when tracking.

(4). Slide blade from lead-lag links.

Blade trailing edge tab may be bent up or

down to compensate for differences in diving or

B. Main Rotor Blade Installation

climbing characteristics between individual

blades during forward flight.

(Ref. Figure 401)

A. Main Rotor Blade Leading Edge Erosion

(1). Position main rotor blade in its

Protection − General

(marked) pitch housing links. Install

blade attaching pins.

Rotor blades produced since 1980 have an 18

inch or 36 inch leading edge abrasion strip to

If new blade is to be installed, or

CAUTION

reduce wear. Earlier model blades without the

if blades are not reinstalled in

abrasion strip that are used in a highly

same positions from which removed or are

abrasive environment should have outer 24

installed on new rotor hub, blade attach

inches of each blade (PN 369D21100-503 or

pins must be adjusted. It is also necessary to

-507, Ref. Figure 804) or outer 18 inches of

track blades.

each blade (PN 369D21100-505 or -509, Ref.

Figure 805) leading edge covered equally by

(2). Align damper clevis on fitting of main

protective tape so blade life is not reduced by

rotor blade; install damper attach bolt

excessive erosion.

to attach clevis to blade.

(3). Remove blade-to-pitch housing link

2. Main Rotor Blade Replacement

match-markings.

A. Main Rotor Blade Removal

3. Main Rotor Blade and Damper Attach Pin

Installation and Adjustment

When main rotor blades are re

CAUTION

moved, the weight of the blades

Whenever new attach pin is in

is not there to balance the force of the col

CAUTION

stalled, main rotor blade is re

lective bungee spring. The collective may

placed, or rotor hub assembly is replaced,

move quickly when the collective stick is

adjustment is required to ensure that pins

moved past the over-center position.

properly fit in mating holes.

(Ref. Figure 401)

(1). Check main rotor blade and damper

arm attach pins for cracks, wear and

(1). Relieve load on blade attachment points

corrosion.

by supporting main rotor blade from

below.

(2). Support blade tip to establish align

ment of holes in blade root fittings and

(2). Identify blade attaching hardware and

pitch housing lead-lag links; install

pins for location (grease pencil, tape,

pin.

Page 401

62-10-00

TR12-001

CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

NOTE: After final adjustment of main rotor

NOTE: After adjustment, measure installed

blade and damper attach pins, thread pro

length of pins from face of thrust washer to

trusion from adjuster nut of 1/2 to 1 thread

outer edge of last bushing, dimension

is acceptable if adjuster nut run-on torque

should be 0.99-1.04 inch (2.515-2.642 cm)

is a minimum of 4 inch-pounds (0.45

for damper pins and 2.84-2.89 inches

Nm) and attach pin safety latch is securely

(7.214-7.341 cm) for main rotor blade pins.

latched over adjuster nut.

(3). Adjust pin for correct fit by rotating

(4). At final installation, locking levers of

small hex nut at end of pin until 25 -

35 pounds force (111.2 - 155.68 N) is

both blade root fitting pins should be

required to snap safety latch into place

located inboard of (behind) stop springs

over nut.

of pitch housing lead-lag links.

Page 402

TR12-001

62-10-00

MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

TURNBUCKLE

JAMNUT

MINIMUM 2-THREAD

PROTRUSION AFTER

FINAL ADJUSTMENT

BOLT

WASHER

NUT

JAMNUT

COTTER PIN

ALTERNATE DAMPER

CLEVIS ATTACH PIN

JAMNUTS SAFETY WIRED TO

TURNBUCKLE AFTER FINAL

ADJUSTMENT

DAMPER CLEVIS ATTACHMENT

BLADE ATTACHING

DAMPER

UPPER ROOT

FITTING

369D21102 BLADE

BUSHING

(NOTE 2)

BLADE TAB

LOWER ROOT

FITTING

VENT HOLE

TIP CAP

BLIND RIVET

(NOTE 1)

AFT TIP CAP

0.130-0.160 IN.

SPAR AND WEIGHT RIVETS

2.62 INCH

(6.655 CM)

FORWARD BALANCE WEIGHT

AFT BALANCE WEIGHT

SCREW

THREADED

FORWARD

INSERT

TIP CAP

369D21100 BLADE

NOTES:

BLIND RIVETS TO BE INSTALLED THRU EACH SIDE OF

ALL BLADES. IF ONE TIP CAP REPLACED OR REPAIRED,

ASSEMBLY BALANCE IS NOT AFFECTED.

BUSHING INSTALLED IN EACH OF UPPER AND LOWER

ATTACHMENT LUGS.

G62-1000A

Figure 401. Main Rotor Blade − Attachment and Outboard End

Page 403

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Revision 20

MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

MAIN ROTOR BLADE

INSPECTION/CHECK

1. Main Rotor Blade Inspection

90 degrees from spanline are acceptable

without repair. Nicks and gouges not

exceeding 0.003 inch (0.076 mm) depth

Special Tools

are acceptable without repair and to

(Ref. Section 91−00−00)

0.005 inch (0.127 mm) with repair.

Item

Nomenclature

N/A

Plastic inspection tool (Fabricate from

AREA 3: Scratches to 0.005 inch (0.127

0.001-0.002 inch (0.025-0.051 mm) thick

mm) depth if oriented 0-30 degrees

plastic material)

from spanline and to 0.003 inch (0.076

mm) deep if oriented between 30-40

degrees from spanline must be re

(1). Inspect skin for evidence of cracks and

moved. No sharp nicks or gouges

holes. Cracks or holes in blade skin

requiring more than 0.005 inch (0.127

surface, regardless of location, are

mm) removal of skin surface are

cause for rejection of blade. Scratches,

permissible.

dents, nicks and other surface defects

AREA 4: Scratches to 0.003 inch (0.076

in blade skin are limited according to

mm) depth if oriented 0-30 degrees and

(3). below. Use suitable dial indicator to

to 0.003 inch (0.076 mm) depth if

check depth of blade dents and

oriented between 30-90 degrees from

scratches.

spanline must be removed. No sharp

Repairable limit dimensions in

nicks or gouges requiring more than

CAUTION

following procedures apply to

0.003 inch (0.076 mm) removal of skin

surfaces that have not been repaired before.

surface are permissible.

Be sure that material has not been removed

AREA 5: Scratches exceeding a depth

from damaged areas before determining

of 0.001 inch (0.025 mm) are cause for

that damage depth limit has not been ex

rejection. Remove scratches to a depth

ceeded. Refer all questionable surface dam

of 0.001 inch (0.025 mm). Area inside

age not covered by following information to

outboard two root fitting bolt holes

MDHI.

(both upper and lower surfaces) and

(2).

(Ref. Figure 601) Limitations for

including skin surface adjacent to these

surface scratches, nicks, gouges and

bolt holes within radius of 1.00 inch

erosion in seven areas of blade skin are

(2.54 cm) from each hole must be free of

described below. Scratches that do not

scratches, nicks, or gouges as would be

penetrate clad surface are acceptable

detected under 5X magnification

without reword in all areas except

(minimum).

AREAS 5 and 8.

AREA 6: Scratches to 0.005 inch (0.127

mm) depth and oriented 0-15 degrees

AREA 1: Minor scratches, nicks and

from spanline are acceptable without

gouges without skin penetrations are

repair. Scratches to 0.005 inch (0.127

acceptable without repair. Skin defor

mm) depth and oriented from 15-30

mation with holes is cause for replace

degrees from spanline must be re

ment. Blade leading edge erosion may

moved. Scratches 0.003 inch (0.076

be repaired if skin is not eroded

mm) deep and oriented from 15-30

through. If leading edge skin is eroded

degrees from spanline are acceptable

through, no matter how slightly, blade

without repair. Scratches to 0.003 inch

must be replaced immediately.

(0.076 mm) depth and oriented from

AREA 2: Scratches to 0.005 inch (0.127

30-90 degrees from spanline must be

mm) depth if oriented 0-30 degrees

repaired. Nicks and gouges not exceed

from spanline and to 0.003 inch (0.076

ing 0.005 inch (0.127 mm) depth must

mm) depth if oriented between 30 and

be repaired. All gouges, nicks, scratches

Page 601

62-10-00

Revision 20

CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

and cracks on trailing edge not exceed

acceptable without repair. No repairs

ing 0.030 inch (0.076 mm) depth must

are permitted in this area.

be smoothed and radiused out over

0.120 inch (3.048 mm) area on each side

AREA C: No repairs permitted.

of damage. Defects beyond 0.030 inch

(0.762 mm) depth are cause for rejec

AREA D: Dents and depressions

tion.

exceeding 0.005 inch (0.127 mm)

without sharp change in section to a

AREA 7: Scratches, nicks, or gouges up

maximum of 0.030 inch (0.762 mm)

to 0.005 inch (0.127 mm) deep and

must be repaired.

detectable with 5X magnification are

not acceptable without repair. Defects

AREA E: Dents and depressions

beyond 0.005 inch (0.127 mm) depth are

exceeding 0.010 inch (0.254 mm)

cause for rejection. Gouges, nicks,

without sharp change in section to a

scratches and cracks not exceeding

maximum of 0.040 inch (1.016 mm)

0.250 inch (6.35 mm) depth on trailing

must be repaired.

edge, except for AREA 8, must be

smoothed and radiused out to 0.250

AREA F: Dents and depressions

inch (6.35 mm) area on each side of

exceeding 0.010 inch (0.254 mm)

damage center. Defects beyond 0.250

without sharp change in section to

inch (6.35 mm) depth require blade

maximum of 0.040 inch (1.016 mm)

replacement.

must be repaired.

AREA 8: Check for gouges, nicks,

AREA G: No repairs permitted.

scratches and cracks detected by using

a bright light and 5X magnification at

AREA H: Dents and depressions

trailing edge corners where blade and

exceeding 0.010 inch (0.254 mm)

tabs join. View area from different

without sharp change in section to

angles during inspection. Damage at

maximum of 0.040 inch (1.016 mm)

this point not exceeding 0.030 inch

must be repaired.

(0.762 mm) depth must be smoothed

and radiused out over a 0.120 inch

AREA J: Dents and depressions

(3.048 mm) area on each side of

exceeding 0.010 inch (0.254 mm)

damage. Defects beyond 0.030 inch

without sharp change in section to

(0.762 mm) depth (Ref. Trim Tab

maximum of 0.040 inch (1.016 mm)

Damage Repair).

must be repaired. Dents and depres

sions exceeding these limitations, refer

to trim tab damage repair.

(3).

(Ref. Figure 602) Depth limitations for

surface dents or depressions in eight

areas of blade skin are described below.

(4).

Inspect surface areas of upper and

A dent or depression is defined as a

lower root fittings (other than AREA 5)

smooth depression or discontinuity with

for evidence of nicks, scratches, and

no sharp changes in section.

wear spots. Nicks, scratches, and wear

spots deeper than 0.010 inch (0.254

mm) in attachment lug area, and bolt

AREA A: Dents and depressions

hole area are not repairable. Damage

exceeding 0.015 inch (0.381 mm)

0.010 inch (0.254 mm) deep or less

without sharp changes in section to a

must be repaired.

maximum of 0.062 inch (1.575 mm)

must be repaired.

(5).

Inspect four attachment lug bushings

in root fittings (Ref. Figure 401) for

AREA B: Dents and depressions to a

security, and evidence of cracks or

maximum of 0.010 inch (0.254 mm) are

severe scoring.

Page 602

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MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

DAMAGE 0.010 INCH (0.254 MM)

IN DEPTH OR LESS IS REPAIR

ABLE IN THESE AREAS (NOTE

CHORD LINE

1.00 INCH (2.54 CM) RADIUS AROUND LAST

SPAN LINE

2 BOLT HOLES 0.001 INCH (0.025 MM) MAXI

0.380 INCH

MUM DEPTH

(9.652 MM)

90°

3.00 INCH

120°

(7.62 CM)

1.25

30°

120°

1.00 INCH

(2.54 CM)

305

30°

120°

30°

15°

DAMAGE LESS THAN

0.030 INCH (0.762 MM)

DEPTH REPAIRABLE IN

THIS AREA (NOTE 1)

30°

15°

23.00 INCH

(58.42 CM)

GOUGES, NICKS AND CRACKS

SCRATCHES

GOUGES AND NICKS

TRAILING EDGE ONLY

ORIENTATION

MAXIMUM DEPTH WITH

MAXIMUM DEPTH

MAXIMUM DEPTH WITH

MAXIMUM DEPTH

MAXIMUM DEPTH WITH

AREA

FROM SPANLINE

OUT REPAIR

WITH REPAIR

OUT REPAIR

WITH REPAIR

OUT REPAIR

REPAIR

0°-90°

MINOR WITHOUT

SKIN PENETRATION

0°-30°

0.005 INCH (0.127 MM)

0.003 INCH (0.076 MM)

0.005 INCH (0.127 MM)

30°-90°

0.003 INCH (0.076 MM)

0.005 INCH (0.127 MM)

0°-30°

NONE

0.005 INCH (0.127 MM)

NONE

0.005 INCH (0.127 MM)

N/A

ÉÉÉ

30°-90°

NONE

0.003 INCH (0.076 MM)

NONE

0.005 INCH (0.127 MM)

ÉÉÉ

0°-30°

NONE

0.003 INCH (0.076 MM)

30°-90°

NONE

0.002 INCH (0.051 MM)

NONE

0.003 INCH (0.076 MM)

0.001 INCH (0.025 MM)

0°-90°

NONE

(NOTE 2)

0°-15°

0.005 INCH (0.127 MM)

NONE

0.005 INCH (0.127 MM)

0.030 INCH (0.762 MM)

15°-30°

0.005 INCH (0.127 MM)

NONE

0.005 INCH (0.127 MM)

NONE

0.003 INCH (0.076 MM)

(NOTES 2, 4)

30°-90°

NONE

0.003 INCH (0.076 MM)

NONE

0.005 INCH (0.127 MM)

0°-90°

NONE

0.250 INCH (6.35 MM)

(NOTE 2)

(NOTES 2, 5)

(NOTES 2, 3, 5)

NOT APPLICABLE

NONE

0.030 INCH (0.762 MM)

(NOTES 2, 4, 5)

TAB END

NOTES:

DAMAGE LIMITS APPLY TO BOTH UPPER AND LOWER ROOT FITTING

SMOOTHED AND RADIUSED CLEANOUT OVER 0.120 INCH (3.048 MM)

SURFACES.

AREA ON EACH SIDE OF DAMAGE.

INSPECTION UNDER 5X MAGNIFICATION (MINIMUM) REQUIRED.

REFER TO TRIM TAB DAMAGE REPAIR.

AREAS NOTED: 0.250 INCH (6.35 MM) SMOTHERED AND RADIUSED

CLEANOUT ALLOWED.

G62-1001A

Figure 601. Main Rotor Blade Damage and Repair Limits −

Nicks, Scratches, Gouges and Cracks

Page 603

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Revision 20

CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

(6). Inspect damper-attachment bearing for

and aft balance weights (Ref.

binding, evidence of galling or scoring

Figure 401) for security. Weights are

in bore and wear. No radial play is

normally recessed 0.050 inch (1.270

permissible. Maximum axial play is

mm) inside end surface of tip. Security

0.015 inch (0.381 mm).

of weights may be checked by using

torque wrench with screwdriver socket

(7). Inspect all bonded areas for evidence of

in slot of weight to detect if weight can

separation. If there appears to be

be rotated by less than 20 inch-

separation of trailing edge bond, lightly

pounds (2.26 Nm). If torque wrench is

probe joint with a 0.001-0.002 inch

not available, check weight security by

(0.025-0.051 mm) plastic inspection

fitting small coin in weight slots and

tool. If plastic inspection tool can be

applying maximum force that can be

inserted to a depth of 1/2 inch (12.70

exerted by only index finger and thumb.

mm) or more, either above or below V

If weights are found to be loose,

insert, separation is excessive.

retighten (Ref. Loose Balance Weight

Repair).

NOTE: Trailing edge structural bond line to V

insert starts 1/4 inch (6.35 mm) in (chord

2. Main Rotor Blade and Damper Attach Pin

wise) from trailing edge joint: therefore

Inspection and Corrosion Protection

above tolerance allows 1/4 inch (6.35 mm)

separation. Be sure measurement is taken

(Ref. Figure 603)

from trailing edge joint, not tab trailing

edge. Maximum trailing edge joint gap al

Consumable Materials

lowed during fabrication is 0.080 inch (2.032

(Ref. Section 91−00−00)

mm).

Item

Nomenclature

CM120

Oil, corrosion preventive

(8). Inspect doubler shown in AREA G

(Ref. Figure 602) for bonding voids

between doubler and blade skin top and

(1). Inspect pin cam handle lobe for cracks

bottom. Use a heavy coin and lightly

and excessive wear. Remove pin from

tap doubler surface. A void is detected

service if cracking or excessive wear is

by a distinct change in sound. Note that

noted.

tapping sounds differ slightly due to

blade structure in leading and trailing

NOTE: If hard anodizing surface of cam lobes is

edge, internal channel and doubler

worn, cam lobes can be re-anodized or

areas. Allowable voids or debonds on

treated with corrosion preventive oil

main rotor blade ribs are as follows:

(CM120).

(2). Inspect attach pin for evidence of

(a).

50% void or debond.

corrosion, or wear, and for straightness.

(b). Maximum four (4) ribs, no more than

Pay particular attention to area along

two (2) adjacent for the 369D21100

edges of barrel nut and bore in cam

and 369D21102 blades.

handle. Remove pin from service if

corrosion or wear is noted or if pin is

(9). Ensure that vent holes are open (Ref.

bent.

Figure 401).

NOTE: If subject to salt laden atmosphere, fol

(10). Inspect fasteners that secure upper and

lowing corrosion prevention treatment is to

lower root fittings, and six rivets that

be applied at each periodic inspection to en

secure skin to spar near tip, for securi

sure continued serviceability of attach pin;

ty. Inspect forward tip cap screw insert

and at each pin removal.

for security and thread damage. Inspect

(3). With attach pin removed, lubricate

trailing edge upper and lower weights

mating surfaces of barrel nut and cam

for debonding and loose rivets.

handle, using corrosion preventive oil

(11). When continuous one-per-revolution

(CM120). Rotate cam handle back and

lateral vibration occurs, inspect forward

forth on barrel nut several times to

Page 604

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MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

ensure that oil penetrates all sections of

(1). Inspect tip caps for evidence of corro

pin operating mechanism. Wipe excess

sion, with particular attention at

oil from pin surfaces.

mating area of blade skin to tip weight

interface. Verify integrity of sealant

3. Main Rotor Blade and Damper Attach Pin

coating.

Disassembly and Special Inspection

(2). If damage is evident, remove tip caps

(Ref. Figure 603) This inspection is to be

and apply penetrating oil to blade tip

preformed in event of a main rotor blade

weight area. Oil arrests any corrosion

strike.

between blade skin and weight assem

bly.

Consumable Materials

(Ref. Section 91−00−00)

(3). Using brush and clean cloth, clean area

Item

Nomenclature

with isopropyl alcohol (CM217). Dry

CM217

Isopropyl alcohol

with clean cloth.

(4). Spray area with light film of rust

Do not intermix bushings,

CAUTION

inhibitor (CM232); then apply thin film

spacers and thrust washers be

of primer and paint lightly as required

tween bolts. Component parts make up a

(Ref. Sec. 20-40-00).

single bolt assembly.

(1). Remove adjusting nut and remove

5. Main Rotor Blade Upper and Lower Root

adjusting bushings, spacers and thrust

Fitting Attach Lug and Lead−Lag Link

washers from pin.

Attach Lug Inspection (25 Hour)

(2). Using brush and clean cloth, clean

parts with isopropyl alcohol (CM217).

(Ref. Figure 604 and Figure 605) The following

Dry with clean cloth.

procedure pertains to helicopters equipped

with 369D21100-BSC thru -515 and

(3). Inspect pin as follows:

369D21102-BSC and -501 main rotor blades

and/or 369H1203-BSC, -11, -21 and -31

(a). Fluorescent inspect pin per MIL-

lead-lag link assemblies.

STD-6866.

(b). Magnetic particle inspect thrust

Consumable Materials

washers, bushings and spacer per

(Ref. Section 91−00−00)

MIL-STD-1949.

Item

Nomenclature

(4). Reassemble pin in sequence as follows;

CM805

Dye penetrant kit

install thrust washer, three (3) adjust

able bushings, spacer, three (3) adjust

able bushings and secure with adjust

NOTE: Main rotor blades and hub assemblies

ing nut.

installed on helicopters operating in a salt

water or corrosive environment should be

Main Rotor Blade Forward Tip Cap

cleaned and washed on a daily basis as a

Inspection and Corrosion Protection

preventative measure to arrest corrosion

(Ref. Figure 603)

(Ref. Main Rotor Hub Corrosion Prevention

(Tri-Flow Wash Procedures)).

Consumable Materials

(1). Visually inspect exposed portion of all

(Ref. Section 91−00−00)

installed main rotor blade upper and

Item

Nomenclature

lower root fitting attach lugs, and main

CM217

Isopropyl alcohol

rotor hub lead-lag link attach lugs, for

CM232

Rust inhibitor spray

broken or cracked lugs, corrosion or

other damage to the lug areas.

Page 605

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Revision 20

CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

2.12 INCH

0.38 INCH

(5.385 CM)

(9.652 MM)

ÇÇÇÇÇÇÇÇÇÇ

1.58 INCH

(3.81CM)

ÇÇÇÇÇÇ

ÂÂÂÂÂÂÂÂÂÂ

2.00 INCH

(5.08 CM)

0.58 INCH

(14.732 MM)

2.17 INCH

23.00 INCH

0.96 INCH

(5.512 CM)

(58.42 CM)

(24.384 MM)

DENTS AND DEPRESSIONS

MAXIMUM

MINIMUM DISTANCE

MAXIMUM DEPTH

MAXIMUM NUMBER

AREA

ALLOWED

BETWEEN DEFECT

WITHOUT REPAIR

WITH REPAIR

OF DEFECTS

AREA

CENTERS

1.5 INCH (3.81 MM)

0.015 INCH

0.062 INCH

(0.381 MM)

(1.575 MM)

N/A

1.5 INCH (3.81 MM)

0.250 INCH (6.35 MM)

0.010 INCH

0.000

(0.254 MM)

0.25 INCH (6.35 MM)

ÇÇÇÇÇ

NONE

ÇÇÇÇÇ

0.000

N/A

ALLOWED

1.5 INCH (3.81 MM)

ÂÂÂÂÂ

0.005 INCH

0.030 INCH

(0.127 MM)

(0.762 MM)

1.5 INCH (3.81 MM)

ÂÂÂÂÂ

0.010 INCH

0.040 INCH

1.5 INCH (3.81 MM)

(0.254 MM)

(1.016 MM)

1.5 INCH (3.81 MM)

0.010 INCH

0.040 INCH

(0.254 MM)

(1.016 MM)

1.5 INCH (3.81 MM)

0.000

NONE

N/A

ALLOWED

1.5 INCH (3.81 MM)

0.010 INCH

0.040 INCH

N/A

(0.254 MM)

(1.016 MM)

1.5 INCH (3.81 MM)

0.350 INCH

1.5 INCH (3.81 MM)

0.010 INCH

N/A

(8.89 MM)

N/A

(0.254 MM)

(NOTE 2)

1.5 INCH (3.81 MM)

NOTES:

N/A - NOT APPLICABLE.

G62-1002B

REFER TO TRIM TAB DAMAGE REPAIR

Figure 602. Main Rotor Blade Damage Limits for Dents and Depressions

Page 606

Revision 40

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CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

NOTE: If movement is suspected but cannot be

verified with the blades installed, remove

Consumable Materials

those blades and inspect bushings for move

(Ref. Section 91−00−00)

ment.

Item

Nomenclature

CM217

Isopropyl alcohol

(2). Using a bright light, inspect slippage

CM318

Primer

marks on the root fitting bushings to

CM420

Sealant

ensure there has been no movement of

CM805

Dye penetrant kit

the bushings. If bushings have moved,

replace main rotor blade before next

flight. Return those main rotor blades

(1). Remove affected main rotor blades (Ref.

where bushing movement has occurred

Main Rotor Blade Removal).

to MDHI for possible rework.

CAUTION

D If cracked or broken lug is noted in main

rotor blade upper and lower root fittings,

D If broken or cracked lugs are noted in

replace main rotor blade (Ref. Main Rotor

main rotor blade upper and lower root fit

Blade Removal) before further flight.

tings, replace main rotor blade before fur

D If cracked or broken lug is noted in main

ther flight (Ref. Main Rotor Blade Remov

rotor lead-lag links, replace or repair

al).

main rotor hub before further flight (Ref.

D If broken or cracked lugs are noted in

Sec. 62-20) (Ref. NOTE: below).

main rotor lead-lag links, replace main

D If a crack is suspected in either the rotor

rotor hub (Ref. Sec. 62-20) (Ref. NOTE:

blade or lead-lag link attach lug, perform

below).

dye penetrant (CM805) inspection per

MIL-I-25135 of lug. If a crack in noted,

D If cracking is suspected in either the rotor

replace main rotor blade (Ref. Main Rotor

blade or hub lead-lag link attach lugs,

Blade Removal) or replace or repair main

perform dye penetrant (CM805) inspec

rotor hub assembly (Ref. Sec. 62-20) (Ref.

tion of lugs per MIL-I-25135. If cracking

NOTE: below).

is noted, replace main rotor blade (Ref.

Main Rotor Blade Removal) or replace or

NOTE: Do not remove bushings or corrosion in

repair main rotor hub assembly (Ref. Sec.

hibiting sealer.

62-20), before further flight (Ref. NOTE:

below).

(2). Using bright light and 5X magnifying

glass, visually inspect the attach lugs of

all main rotor blade upper and lower

NOTE: Lead-Lag link assemblies may only be

root fitting and main rotor lead-lag

replaced by MDHI authorized personnel or

links for broken or cracked lugs,

under MDHI supervision. Contact your local

corrosion or other damage to the lug

MDHI Field Service Representative for fur

areas.

ther information.

NOTE:

6. Main Rotor Blade Upper and Lower Root

D Pay particular attention to area around

Fitting, Attach Lug and Lead−Lag Link

attach pin hole bushings in the lugs.

Attach Lug Inspection (100 Hour)

D Pay particular attention to the cross-

hatched areas.

(Ref. Figure 604 and Figure 605) The following

procedure pertains to helicopters equipped

(3). If slippage marks have already been

with 369D21100-BSC thru -523,

applied, inspect the root fitting for any

369D21120-501, 369D21102-BSC thru -523

indication of movement of the bushings;

and 369D21121-501 main rotor blades and/or

no movement is allowed. Return main

369H1203-BSC, -11, -21 and -31 lead-lag

rotor blades that have root fitting

link assemblies.

bushing movement to MDHI for

Page 608

Revision 33

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MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

possible rework. If slippage mark is

(5). Inspect lead-lag link blade attach pin

degraded, reapply.

hole bushings for any indication of

movement of the bushings in the links.

(4). Perform main rotor blade upper and

If any of the bushings have movement,

lower root fitting inspection as follows:

replace the links.

(a). Inspect main rotor blade root fitting

If required, apply a light but

for missing (no squeeze-out) or

CAUTION

thorough coat of sealer (CM420)

cracked adhesive/paint around the

or primer (CM318) around bushings. Note

periphery of the root fitting. If this

that excessive amounts of sealant or primer

condition exists, proceed as follows:

around the bushings are not desirable and

1). Loosen, but do not remove the

can unbalance the main rotor system.

extreme outboard bolt.

(6). If sealing compound is not already

2). Insert a 0.004 inch (0.102 mm)

installed or becomes loose, clean and

thick piece of mylar/viewfoil

then seal all junctions between all the

between the fitting and the dou

steel bushings and the main rotor blade

bler.

root fitting attach lugs with a film of

sealing compound or zinc-chromate

3). If the mylar can be inserted,

primer without removing the bushings.

contact Field Service Representa

tive for disposition of blade.

(7). For the main rotor blade root fitting

attach lugs, carefully remove sufficient

4). If the insertion is 0.10 inch (2.54

amount of sealant and paint from only

mm) or greater, remove blade from

the bushing in the area where the

service.

slippage mark is to be applied (if not

already done). Using isopropyl alcohol

NOTE: Measurement of the insertion is from

(CM217), clean the area where the

the edge of the root fitting.

slippage mark is going to be applied to

5). Retorque root fitting outboard bolt

allow adequate adherence of epoxy

to 60 - 65 inch-pounds (6.78 -

paint.

7.34 Nm) plus drag torque.

NOTE:

In the following step, a crack

CAUTION

D Locate slippage mark in a position that

might be difficult to detect if

can be viewed at subsequent inspections

bright light is not used.

with main rotor blade installed in the

NOTE: The lower side of the blade is more sus

hub. Slippage marks should not be ap

ceptible to cracking.

plied to cross-hatched areas to preclude

masking possible cracks.

(b). Using a bright light, inspect doubler

D Insure that slippage mark is applied to

and root fitting, paying particular

bushing at upper and lower root fitting in

attention to the lower side, for

side surfaces.

cracks. If crack is found, blade is to

be scrapped.

D Do not use torque seal.

NOTE: Lead-Lag link assemblies may only be

(8). Apply epoxy paint slippage marks to

replaced by MDHI authorized personnel or

four locations as shown.

under MDHI supervision. Contact your local

Field Service Representative for further in

(9). Install main rotor blades (Ref. Main

formation.

Rotor Blade Installation).

Page 609

62-10-00

Revision 29

CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

7. Main Rotor Blade Leading Edge Abrasion

8. Main Rotor Blade Torque Event Inspection

Strip Check

(Ref. Figure 604)

The leading edge abrasion strip should be

NOTE: This inspection requires the use of a

checked prior to each flight or on every daily

bright light.

check. The following is a comprehensive

checklist:

(1). Lifting from the outboard end of the

blade, lift blade off the droop stop.

NOTE: If void is noted towards end of blade, re

move tip cap and check for presence of bal

(2). Inspect the bottom-side of the blade as

ance weights. If weights are not installed, a

follows:

false indication of a void is possible.

(a). Using a bright light and 10x magni

(1). Check for any blistering, bubbling or

fying glass, inspect for chordwise

lifting of the abrasion strip; this

cracks protruding from under root

indicates a void.

fitting and doubler (View C and Note

7).

(a). Voids cannot be closer than 0.50 inch

(12.70 mm) to any outside edge of

(b). Inspect the area around the root

abrasion strip.

fitting, doubler and skin for cracks.

(b). Voids exceeding 1.5 square inch

(c). Inspect the attach lugs at the bush

(9.677 square cm) are unacceptable.

ings for cracks.

(c). Voids cannot be closer than one inch

(d). Inspect the entire length of the blade

(2.54 cm) to any other void.

for cracks.

(2). Number of acceptable voids depends

(e). Lower blade back onto droop stop.

upon length of abrasion strip.

(3). With blade resting on the droop stop,

inspect the top-side of the blade as

(a). There cannot be more than three

voids on either the top or bottom of

follows:

the 36 inch (91.44 cm) long abrasion

(a). Inspect the area around the root

strip surface.

fitting, doubler and skin for cracks.

(b). There cannot be more than two voids

(b). Inspect the attach lugs at the bush

on either the top or bottom of the 18

ings for cracks.

inch (45.72 cm) long abrasion strip

surface.

(c). Inspect the entire length of the blade

for cracks.

(3). Record all voids in regards to size and

location in the helicopter log book and

(4). If any of the above defects are found,

check each void prior to each flight for

the main rotor blade is to be rejected

growth and acceptable criteria.

and scrapped.

Page 610

Revision 35

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MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

NOTES 2, 3 AND 4

DOUBLER

NOTE 6

ROOT FITTING

NOTE 5

(NOTES 1, 2 AND 3)

NOTE 7

NOTE 5

VIEW LOOKING UP

ROTATED

LOOSEN BUT DO NOT REMOVE BOLT.

RETORQUE BOLT TO 60 - 65 INCH-POUNDS

(6.78 - 7.34 NM) PLUS DRAG TORQUE.

UPPER ROOT FITTING ATTACH LUG

(TYP 2 PLACES) (NOTE 1)

NOTE 5

LEAD-LAG LINK ATTACH LUG

(TYP 8 PLCS) (NOTE 1)

MAIN ROTOR BLADE

LOWER ROOT FITTING AT

TACH LUG (TYP 2 PLCS)

(NOTE 1)

NOTES:

VISUALLY INSPECT AREAS OF ALL ROOT FITTINGS AND LEAD-LAG ATTACH LUGS FOR CRACKS OR

BREAKS. INSPECT BLADE ATTACH BUSHINGS FOR LOOSENESS. IF LOOSE, REPLACE LEAD-LAG LINKS.

PAY PARTICULAR ATTENTION TO AREA AROUND ATTACH PIN HOLES IN LUGS.

SEAL ALL JUNCTIONS BETWEEN BUSHINGS AND ATTACH LUGS WITH SEALER OR PRIMER (CM318).

LEAD-LAG LINK ASSEMBLIES ARE SUB-ASSEMBLIES OF THE MAIN ROTOR HUB ASSEMBLY.

INSPECT MAIN ROTOR BLADE UPPER AND LOWER ROOT FITTING FOR MISSING OR CRACKED ADHESIVE.

USING BRIGHT LIGHT, INSPECT MAIN ROTOR BLADE DOUBLER FOR CRACKS. PAY PARTICULAR ATTENTION

TO BOTTOM SIDE OF BLADE, JUST BEYOND ROOT FITTING AND IN LINE WITH ROOT FITTING ATTACH BOLTS.

USING A BRIGHT LIGHT AND 10X MAGNIFYING GLASS, INSPECT FOR CHORDWISE CRACKS PROTRUDING

FROM UNDER ROOT FITTING AND DOUBLER.

G62-1009D

Figure 604. Main Rotor Blade Root Fitting, Attach Lugs and Lead−Lag Link

Assembly Inspection

Page 611

62-10-00

Revision 35

MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

MAIN ROTOR BLADE

REPAIRS

1. Main Rotor Blade Repair (Nicks,

CAUTION

Scratches and Wear Spots)

D Repair only those damaged areas that are

Consumable Materials

within repairable limits specified.

(Ref. Section 91−00−00)

D Do not use chemical paint remover to re

Item

Nomenclature

move paint from abrasion strip. Chemi

CM206

Chemical coating

cals can attack the abrasion strip to blade

CM801

Abrasive paper, silicon carbide

bonding agent.

(1). Using abrasive paper (CM801), not

(Ref. Figure 601)

coarser than grade 320, remove paint

Do not use chemical paint re

from surface area to be repaired.

CAUTION

mover to remove paint from

abrasion strip. Chemicals can attack the

(2). Clean abraded area with clean cloth

abrasion strip to blade bonding agent.

dampened by solvent (CM234). Allow to

dry for minimum of 15 minutes.

(1). Using abrasive paper (CM801), not

coarser than grade 320, remove nicks,

(3). Mask edges of repair areas with one

scratches and wear spots from upper

layer of tape (CM708).

and lower root fittings, and from blade

skin.

Do not cut tape after it is

CAUTION

(2). Use finer grade of paper, as necessary

applied to blade.

to restore surface roughness to original

finish.

(4).

Mix filler (CM507), three parts ”A” and

two parts ”B” by weight. Mix thorough

(3). Remove material in such a manner that

ly until mixture is dark red in color. An

no abrupt changes occur in surface

alternate filler (CM508) may be used if

contours.

equal parts ”A” and ”B” by weight are

(4). Apply chemical film surface treatment

mixed.

(CM206) to repaired surface(s) (Ref.

Sec. 20-30).

(5).

Allow filler to cure for minimum of 24

hours at room temperature.

2. Main Rotor Blade Repair (Dents,

Depressions and Erosion)

(6).

Smooth filler area with grade 400

abrasive paper (CM801). Limit smooth

(Ref. Figure 602)

ing to masked area.

Consumable Materials

(7).

Remove the tape and inspect alclad

(Ref. Section 91−00−00)

coating of area around repair. Penetra

Item

Nomenclature

tion of coating is cause for blade

CM220

Naphtha aliphatic

replacement.

CM229

Paint remover

(8).

Clean repaired area with a cloth

CM234

Solvent, dry-cleaning

dampened by solvent (CM220).

CM304

Enamel, epoxy

CM507

Resin, filler

(9).

Apply chemical film treatment to

CM508

Resin, filler

repaired surface (Ref. Sec. 20-30-00).

CM708

Tape

CM801

Abrasive paper, silicon carbide

(10).

Touch-up reworked area with paint

(CM304) as required.

Page 801

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Revision 33

CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

3. Trim Tab Damage Repair

(6). If excessive damage requires full or

partial removal of trim tab from blade,

(Ref. Figure 802)

perform the following (no minimum

length of trim tab is required):

Consumable Materials

(a). Position blade on workbench so that

(Ref. Section 91−00−00)

a straight edge is provided for cutting

Item

Nomenclature

or filing off trim tab.

CM206

Chemical coating

CM220

Naphtha aliphatic

Cutting, grinding or filing to re

CAUTION

move trim tab, and deburring of

CM234

Solvent, dry-cleaning

reworked blade trailing edge, are to be per

CM304

Enamel, epoxy

formed in a SPANWISE direction only. Do

CM318

Primer

NOT use shears or clippers to remove trim

tab.

Provide protective surface and/

(b). Use metal cutting saw or equivalent

CAUTION

or covering to prevent scratch

to remove the 0.38 inch (9.65 mm)

ing, nicking or other damage to blade during

wide trim tab per dimensions shown

rework. Position blade on work bench or

Ref. Figure 802, View A-A). Deburr

equivalent.

edges in a SPANWISE direction only.

NOTE: No minimum length of trim tab is re

(7). Peel and remove tape from blade and

quired. In addition, the entire trim tab, or

inspect area around repair; clean

portion of the trim tab, may be removed if

repaired area with cloth dampened in

required. Removal of entire trim tab elimi

naptha (CM220).

nates adjustment of blade tracking capabili

ty for that blade. Main rotor blades with and

(8). Apply chemical film treatment (CM206)

without trim tabs are 100% interchange

to reworked area of blade trailing edge

able, individually and in ship sets.

or trim tab; apply a thin film of primer

(CM318) and paint (CM304) lightly.

(1).

Remove main rotor blade with damaged

trim tab.

(9). Reinstall main rotor blade and perform

track and balance (Ref. Sec. 18-10).

(2).

Wipe away dirt on and around trim tab

area with clean cloth dampened with

NOTE: Removal of entire trim tab eliminates

dry cleaning solvent (CM234).

adjustment of blade tracking capability for

that blade.

(3).

Mask edges of blade area around trim

tab area with tape; do NOT cut tape

after it has been applied to blade.

4. Forward Tip Cap Threaded Insert Repair

(4).

Remove damaged area of trim tab by

Consumable Materials

making V-type cut with 45° sides

(Ref. Section 91−00−00)

joined by a 0.25 inch (6.35 mm) radius

Item

Nomenclature

at the bottom of the V. Maximum V-cut

depth is 0.35 inch (8.89 mm); do not cut

CM318

Primer

past trim tab area into main portion of

blade.

Replace a loose or stripped insert. Use

(5).

If damage occurs within 1 inch (2.54

self-locking insert of correct size and install

cm) of either or both ends of trim tab,

with wet primer (CM318). Comply with

remove tab end(s) and restore contour

replacement requirements of applicable NAS

as shown.

standard.

Page 802

Revision 20

62-10-00

CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

5. Loose Balance Weight Repair

(4). Mix epoxy adhesive (CM409) per

manufacturer`s instructions and apply

(Ref. Figure 401) Reinstall loose forward and aft

to bonding surfaces.

balance weights as follows:

(5). Position weights on blade by aligning

holes in weights to existing rivet holes

Consumable Materials

on blade and apply light pressure to

(Ref. Section 91−00−00)

weights until epoxy sets.

Item

Nomenclature

(6). Install (3 ea.) rivets in existing holes.

CM431

Sealing, locking and retaining compound

(7). If not already installed, install two

more rivets as follows.

(1). Unscrew loose weight until it projects

approximately one-half inch (12.7 mm)

(a). Mark location of rivets to be in

and remove old accumulation of

stalled.

powdered compound.

(b). Drill holes at marked locations.

(2). Apply grade A locking compound

(c). Deburr and clean debris from holes.

(CM431) and screw weight back into

(d). Coat all exposed surfaces with primer

blade until slotted end of weight is

(CM318).

recessed 0.050 inch (1.27 mm) below tip

surface. Wipe off excess compound.

(e). Install rivets.

Allow to cure for a minimum of

(f). Allow epoxy adhesive to cure per

CAUTION

12 hours. If faster cure is de

manufacturer's instructions before

sired, complete cure can be obtained by al

flying aircraft.

lowing part to set for 30 minutes at room

7. Loose or Missing Rivets or Aft Tip Cap

temperature and then heating for 30 min

Repair

utes at approximately 212°F (101°C).

(Ref. Figure 401) Replace all loose or missing

(3). If locking compound is not available,

rivets. Reinstall or replace loose or missing aft tip

screw weight into normal position and

cap as follows:

centerpunch end of weight into mating

threads at three evenly spaced points to

Consumable Materials

prevent rotation.

(Ref. Section 91−00−00)

6. Loose Trailing Edge Weight Repair

Item

Nomenclature

CM234

Solvent, dry-cleaning

(Ref. Figure 801)

CM318

Primer

CM411

Adhesive, epoxy

Consumable Materials

CM801

Abrasive paper, silicon carbide

(Ref. Section 91−00−00)

Item

Nomenclature

NOTE: Spare tip caps are supplied with bond

CM220

Naphtha aliphatic

ing surface coated with nylon primer to fa

CM318

Primer

cilitate installation. Main rotor balance is

CM409

Adhesive, epoxy

not affected by following repair.

CM804

Emery cloth, fine

(1). Lightly abrade primed surfaces of tip

cap with grade 180 abrasive paper

(1). Carefully remove loose or partially

(CM801). Wipe away residue with cloth

debonded weights.

dampened in solvent (CM234) and

allow tip cap to dry at room tempera

(2). Abrade debonded surface using

ture for 30 minutes.

#200-300 grit emery cloth (CM804).

(2). Mix two-part bonding adhesive

(3). Clean bonding surfaces with naptha

(CM411) in equal proportions by

aliphatic (CM220).

weight.

Page 804

Revision 20

62-10-00

MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

NOTE 2

NOTES 2, 3

TOP

6.80 INCH (17.272 CM)

SURFACE

0.38 INCH

NOTE 1

(9.652 MM)

NOTE 3

0.00 - 0.10 INCH

(0.00 - 2.54 MM)

NOTE 4

0.38 INCH

1.00 INCH

(9.652 MM)

1.00 INCH

(2.54 CM)

VIEW A-A

NOTES:

REMOVE DAMAGED END(S) IF THEY OCCUR WITHIN 1 INCH (2.54 CM) OF TAB ENDS.

0.25 INCH (6.35 MM) RADIUS CLEANUP. FINISH PER BASIC HMI.

MAXIMUM DEPTH OF REPAIR 0.35 INCH (8.89 MM).

NO MINIMUM LENGTH OF TAB REQUIRED. IF DAMAGE OCCURS AT BOTH ENDS, IT IS

PERMISSIBLE TO REMOVE AT BOTH ENDS

Figure 802. Repair and Removal of Trim Tab, Main Rotor Blade

0.002 INCH

(0.0508 MM)

MAXIMUM

EDGE OF

STAKING TOOL

FLUSH TO

ARM

+0.010 INCH

(+0.254 MM)

BEARING WITH STAKING

GROOVE IN OUTER RACE

PRESSING

STAKING

BEARING IN ARM

G62 1005A

Figure 803. Bearing Replacement − Main Rotor Blade Damper Attach Fitting

Page 805

62-10-00

Revision 20

CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

(3). Apply bonding adhesive to abraded tip

(5). Measure fitting bore diameter. Accept

cap and mating surfaces at rotor blade

able limits are 0.7488-0.7493 inch

tip. To extent possible, be sure that

(19.01952-19.03222 mm).

there are no adhesive voids.

(6). Apply thin coat of primer (CM318) to

fitting bore.

(4). Install tip cap in blade tip, apply

uniform clamping pressure to joint, and

(7). Press bearing into fitting with arbor

wipe away excessive adhesive. Allow to

press and fixture (ST709). Wipe away

cure for eight hours at room tempera

excess primer.

ture or two hours at 150°F (66°C).

(8). Stake bearing at both sides of fitting

with staking tool (ST710) in hydraulic

(5). Install two MS20604AD3C2 blind

press with 6000-8000 pounds

rivets, one though each side of blade tip

(2722-3629 Kg) of force. When staked,

and tip cap.

outer race of bearing shall be flush to

not more than 0.010 inch (0.254 mm)

8. Damper Attach Blade Fitting Bearing

above fitting surface (both sides). Gap

Replacement

between staked lip of bearing race and

chamfered surface of fitting bore shall

(Ref. Figure 803)

not exceed 0.002 inch (0.0508 mm) as

checked with feeler gage. Staking

Consumable Materials

operation shall produce no cracks in

(Ref. Section 91−00−00)

fitting or bearing.

Item

Nomenclature

(9). Fill staking gap, if any, with primer

CM216

Loctite remover

(CM318).

CM219

Methyl-ethyl-ketone

9. Outboard Leading Edge Abrasion Tape

CM318

Primer

Replacement

(Ref. Figure 804 and Figure 805) Replace

Special Tools

abrasion tape when it is worn or eroded. Operation

(Ref. Section 91−00−00)

in rain or dust reduces tape life and more frequent

Item

Nomenclature

replacement is necessary.

ST709

Arbor press fixture

ST710

Staking tool

Consumable Materials

(Ref. Section 91−00−00)

Item

Nomenclature

(1).

Use fly or circle cutter with 5/16 inch

CM220

Naphtha aliphatic

(7.9375 mm) pilot to remove staked lip

CM717

Tape, pressure sensitive

from one side of bearing without

CM801

Abrasive paper, silicon carbide

removing any material from fitting. If

fitting is damaged by cutter, blade must

be replaced.

A. Removal

(2).

Use an arbor press to press bearing

NOTE: A second abrasion tape may be applied

from fitting.

on top of the first tape to help replacement

when top tape becomes eroded.

(3).

Clean primer residue from fitting bore

(1). When only the top tape is replaced, peel

with MEK (CM219). Remove locking

off top tape. Do not damage bottom tape

compound residue, if any, with locking

bond to main rotor blade.

compound remover (CM216).

(2). Wipe surface of bottom tape with a

(4).

Using 10-power magnifying glass,

clean cloth dampened with naptha

inspect fitting bore for cracks. No

aliphatic (CM220) to remove any

cracks are permitted.

adhesive.

Page 806

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MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

(3). Do not allow naptha aliphatic (CM220)

B. Installation

to touch the bond line between the

bottom tape and the main rotor blade

(1). Lightly abrade faying surface of main

surface.

rotor blade with 400 grit abrasive paper

(CM801).

(4). If necessary, remove bottom tape from

(2). Wipe faying surface of blade with

main rotor blade.

naptha aliphatic (CM220) to eliminate

grease or dirt film.

(5). Wipe main rotor blade surface with a

clean cloth dampened with naptha

(3). Use heat gun or equivalent to warm

aliphatic (CM220) to remove any

blade faying surface. Temperature must

adhesive.

not exceed 120°F (49°C).

24.00 INCH

(60.96 CM)

(NOTE 1)

MAIN ROTOR BLADE

ABRASION STRIP

ABRASION STRIP TIP

(369A1105)

EROSION 0.40 INCH

BLADE PROFILE

(369D21105)

(NOTE 2)

(10.16 MM) MAXIMUM

ABRASION TAPE

(369D21104 OR CM717)

SKIN TIP EROSION

0.30 INCH (7.62 MM)

CHORDWISE

MAXIMUM

BALL. WEIGHT

VIEW A-A

(NOTE 3)

NOTES:

END OF TAPE TO BE FLUSH WITH OUTBOARD END OF BLADE SKIN. TAPE

TO BE SYMMETRICAL ABOUT LEADING EDGE.

ABRASION TAPE MUST BE ALIGNED AT TOP PART OF BLADE.

VIEW IS TYPICAL FOR 369D21100 BLADES EXCEPT -505, -509, -511

G62-1006B

(SEE ALSO DN-39).

Figure 804. Installation/Replacement of Abrasion Tape

(Main Rotor Blade Leading Edge)

Page 807

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MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

(4). Remove backing and apply (CM717

MEK is flammable. Use in

WARNING

preferred over 369D21104) abrasion

well ventilated area and

tape to outboard leading edge of main

away from open flame.

rotor blade as follows:

(3). Clean areas to be sealed with clean

(a). Trim corners of abrasion tape to a

cloth moistened with solvent (CM228).

0.25 inch (6.35 mm) radius to reduce

For hard to clean problem areas, MEK

peeling.

(CM219) may be used.

(b). Apply 6.50 inch (16.5 cm) wide and

(4). Prepare adhesive (CM404) per

24 inch (61 cm) long abrasion tape

manufacturer's instructions.

along blade leading edge (Ref.

Figure 804) so tape overlaps bottom

(5). Apply bead of adhesive to interface of

and top of blade edge equally or (Ref.

abrasion strip and blade skin. Ensure

Figure 805) for 369D21100-505, -509

there are no gaps or bridges in bead.

and -511 blades.

(6). Cure adhesive per manufacturer's

(c). Smooth and press abrasion tape into

instructions.

place by hand. Use heat gun or

equivalent to maintain temperature.

11. Tip Cap Sealing

(d). Re-apply pressure by hand following

(Ref. Figure 805)

initial installation to make sure of

proper bonding. Abrasion tape must

be free of surface wrinkles or air

Consumable Materials

(Ref. Section 91−00−00)

bubbles.

Item

Nomenclature

NOTE: A second abrasion tape may be applied

CM212

Releasing agent

on top of the first tape to facilitate replace

CM213

Releasing agent

ment when top tape becomes eroded. To ap

CM318

Primer

ply second tape, wipe surface of installed

strip clean with naptha aliphatic (CM220)

CM420

Sealant

and repeat steps (3). and (4). above. Second

CM427

Sealing compound

abrasion tape must be evenly aligned with

CM428

Sealing compound

first at top surface of blade (Ref. Figure 804

or Figure 805).

(1). Apply release agent (CM212 or CM213)

10. Leading Edge Abrasion Strip Sealing

to inside of tip cap per manufacturer's

instructions.

(Ref. Figure 805)

(2). Prepare and apply a 0.010-0.020 inch

(0.254-0.508 mm) coating of sealant

Consumable Materials

(CM420, CM427 or CM428) to faying

(Ref. Section 91−00−00)

surfaces per manufacturer's instruc

Item

Nomenclature

tions.

CM219

Methyl-ethyl-ketone

CM228

Surface cleaner

(3). Attach tip cap to blade and install

CM404

Adhesive, epoxy

screw with primer (CM318).

(4). Wipe off squeezed out sealant flush

(1). Remove screw and tip cap from main

with surface.

rotor blade.

NOTE: To inhibit moisture entering bond joint

(2). Remove any loose or cracked sealant or

of abrasion strip after initial application,

adhesive from areas of main rotor

reapply sealant, when sealant is worn away

blade.

or becomes cracked.

Page 809

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TR12-001

CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

369A1116 TIP CAP

SEAL WITH

PR1436G, CLASS B-2

SEAL WITH EC2216 B/A FROM L.E. TO

PR1422G, CLASS B

0.75 INCH (19.05 MM) DIM. ON T.E.

RADIUS (UPPER AND LOWER SURFACE)

0.75 INCH

(19.05 MM)

0.75 INCH

(19.05 MM)

369D21100 MAIN ROTOR BLADE ASSEMBLY

369D21105 ABRASION STRIP REF.

0.003-0.005 INCH

369A1103 SKIN REF.

TYP.

(0.0762-0.127 MM)

SEAL WITH

EC2216 B/A

369A1109-501, 269A1186

0.010 INCH

SEAL SKIN / BAL. WT.

BAL. WT. REF.

(0.254 MM)

ASSY INTERFACE

SEAL WITH

TYP

WITH EC2216 B/A

EC2216 B/A

A-A

TIP CAP OMITTED FOR CLARITY

0.12 INCH

(3.048 MM)

TYP

369D21105 ABRASION STRIP

C-C_{TYP 2 PLCS}

SEAL SCREW BY INSTALLING

369A1103 SKIN

WITH WET PRIMER

NAS517-3-0

Figure 806. Main Rotor Blade Abrasion Strip and Tip Cap Sealing

Page 810

Revision 20

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MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

12. Main Rotor Blade Protective Tape

NOTE: Tape must be of equal length on all

Installation

blades to ensure proper balance.

In an effort to reduce the amount of erosion in

(2). Cut tape long enough to cover erosion

the area inboard of the abrasion strip, MDHS

plus approximately one-half inch (12.7

has approved the installation of stainless steel

mm) overlap on leading edge abrasion

or Mylar tape to the blade leading edge.

strip.

Installation of the tape is optional.

(3). Round off square corners of tape to

The approved 3M Mylar tape, P/N 8671-1, is

reduce peeling.

one inch (2.54 cm) wide and the 304 stainless

steel tape, P/N 87-369D21104, is 0.027 inch

(4). Lightly abrade faying surface of main

(0.6858 mm) thick and two inch (5.08 cm)

rotor blade in area where tape is to be

wide.

installed with 400-grit abrasive paper

(CM801).

The length of the tape can vary, up to 8.0

inches (20.32 cm) in length, but must be equal

(5). Wipe abraded area with naphtha

on all blades.

aliphatic (CM220) to eliminate grease

and dirt film.

It is recommended to start with 2.5 inch (6.35

cm) length and increase the length as erosion

(6). Treat any bare metal with epoxy-type

occurs by replacing the tape.

paint.

NOTE:

NOTE: Do not allow temperature to exceed

D This installation is only approved on

120°F (49°C).

main rotor blades equipped with the 36

(7). Using a heat gun, or equivalent, heat

inch (91.44 cm) abrasion strips.

abraded area.

D For installation of the Mylar tape, refer to

manufacturer's instructions. Use of aero

(8). Apply aerosol primer to bonding area

sol primer Promoter 86 may be used to

and allow to dry.

speed cure time of the tapes adhesive.

Mylar tape comes in rolls one inch (2.54

(9). Remove backing and apply tape to

cm) wide by 36 yards (329184 m) in length

leading edge of blade.

and the promoter comes in 36 ounce

(a). Apply tape so it overlaps each side of

(1.065 L) cans. Mylar tape can be pur

blade equally.

chased from RS Hughes Company

(1-800-453-8116).

(b). Tape should overlap the inboard end

of abrasion strip 0.5 ±0.03 inch (12.7

A. Stainless Steel Tape Installation

±0.762 mm) at the leading edge of

blade.

Consumable Materials

(Ref. Section 91−00−00)

NOTE: Tape must be free of surface wrinkles or

Item

Nomenclature

air bubbles.

CM220

Naphtha aliphatic

(10). Smooth and press tape into place by

CM801

Abrasive paper, silicon carbide

hand.

Do not cut or trim tape after

(11). Re-apply pressure by hand following

CAUTION

installation on blade, damage to

initial installation to ensure proper

blade will occur.

bonding.

(1). Measure length of eroded area on blade

(12). Perform main rotor balance (Ref. Sec.

with the most erosion.

18-10-00 or 18-10-60).

Page 811

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Revision 20

MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

MAIN ROTOR HUB

REMOVAL/INSTALLATION

1. Main Rotor Hub − General

(3). Remove lockwire and disconnect

flexible boot from lower end of hub

The main rotor hub consists of a central hub,

liner.

five identical pitch housings spaced 72 degrees

apart horizontally around the hub with

(4). Disconnect each pitch control rod from

associated mechanisms and linkages.

pitch housing.

Lead-lag links, a lead-lag damper, a droop

(5). Disconnect scissors crank from main

stop striker strip and spacer, and a pitch

rotor hub or scissors link.

control bearing with each pitch housing

produce the pivoting axis, blade flapping stop

NOTE: To facilitate assembly, color code each

contact surfaces and lead-lag hinge function

pitch control rod to match pitch housing to

for the rotor blades.

which it is attached.

Five laminated retention strap assemblies that

(6). Remove two screws securing retainer to

are flexible both vertically and torsionally

main rotor hub nut.

extend through the pitch housings and connect

to the lead-lag links.

(7). Remove nut retainer.

(8). Using main rotor mast nut wrench

A lower shoe, attached to the central hub,

(ST701), remove nut from mast.

contains a droop stop ring and droop restrain

ers that support the blades at rest and

(9). Using hub puller (ST702), break loose

distribute droop loads at low blade rpm.

main rotor hub (Ref. Figure 401).

Remove hub puller.

The following instructions provide field

maintenance and repair procedures for the

(10). Attach hoisting adapter, to eyebolts and

main rotor hub.

hoist hub from mast.

2. Main Rotor Hub Replacement

B. Main Rotor Hub Installation

A. Main Rotor Hub Removal

(Ref. Figure 402)

(Ref. Figure 401)

Consumable Materials

(Ref. Section 91−00−00)

Special Tools

Item

Nomenclature

(Ref. Section 91−00−00)

CM111

Grease, aircraft

Item

Nomenclature

CM115

Grease, oscillating bearing

ST201

Hoisting adapter

CM204

Compound, corrosion preventative

ST701

Main rotor wrench assembly

CM702

Lockwire CRES

ST702

Hub puller

Special Tools

(1). Remove all main rotor blades.

(Ref. Section 91−00−00)

Item

Nomenclature

(2). Remove main rotor drive shaft; then

ST201

Hoisting adapter

reinstall hoisting eyebolts, washers and

ST701

Main rotor wrench assembly

nuts in rotor hub. Locate them to

correspond with lugs of hoisting

ST703

Main rotor hub driver

adapter (ST201).

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Revision 36

CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

Main rotor hub is a highly

(5). Hand-pack hub cavity, between sleeve

CAUTION

stressed component. Use ex

bushing and hub, with grease (CM111).

treme care to prevent it from striking any

(6). Place recessed spacer, recess down, on

object. Any impact damage may require re

top of sleeve bushing.

placement of hub.

(7). Hand-pack upper bearing cup and cone

NOTE:

with grease; then install cone on mast

D Removal of recessed spacer, upper bear

and use hub drive tool (ST703), to fully

ing cone, upper seal and seal retainer is

seat cone.

not mandatory for installation of the

main rotor hub. If these items are in

(8). Fill remaining cavity to upper seal with

stalled, perform steps (1). thru (4). and

grease.

(11). thru (22). Caution should be used

(9). Position upper seal in seal retainer

when installing hub to prevent damage to

with lip up; then press seal and retain

these parts.

er in hub counterbore.

D If recessed spacer, upper bearing cone,

upper seal and seal retainer have been re

(10). Using a soft drift, carefully tap seal

moved, these parts should not be as

outer ring to seat in counterbore. Wipe

sembled in hub before installation of hub

away any excess grease.

on helicopter. These items are reas

(11). Apply grease (CM111) to exposed

sembled in hub after seating hub on mast.

threads on mast.

Prior to installing main rotor hub, insure

that all bearings are adequately serviced

Be sure that seal is properly po

CAUTION

with grease (CM111).

sitioned against seal retainer

and that seal retainer does not pinch seal.

D Replacement main rotor hubs do not come

Check by inserting a loop of approximately

balanced from MDHS. If installing a re

0.050 inch (1.27 mm) diameter lockwire,

placement hub, perform a main rotor hub

balance (Ref. Sec. 18-10-00, Main Rotor

round feeler gage or other suitable tool with

Hub Balance Procedure).

out sharp edges between seal lip and retain

er.

(1). Attach hoisting adapter (ST201) to

NOTE: To insure that hub is seated onto mast

eyebolts in main rotor hub and connect

properly before torquing, 2 - 4 threads

suitable hoist.

should be showing above the mast nut with

If hub assembly (with sleeve

nut installed finger tight.

CAUTION

bushing, spacer, upper bearing

(12). Install mast nut, using wrench (ST701);

and seal retainer installed) does not seat

torque nut to 200 foot-pounds (271

properly onto mast, do not attempt to force it

Nm). Apply coat of corrosion preventive

into position. Remove hub assembly from

compound (CM204) to screw holes in

mast and determine cause of hub not seat

mast nut.

ing, correct the problem and follow the pro

cedures for reinstallation.

(13). Place retainer on nut and check

retainer-to-nut screw hole alignment.

(2). Check that rotor mast is clean. Hoist

main rotor hub and position over mast;

(14). Increase nut torque to not more than

then lower hub onto mast.

250 foot-pounds (339 Nm) to align

holes in retainer and nut.

NOTE: To inhibit mast corrosion when operat

ing in salt water environment, lightly coat

NOTE: If holes cannot be aligned in 200 - 250

bearing journals of mast with grease

foot-pound (271 - 339 Nm) torque range,

(CM115).

remove and invert nut and repeat proce

dures in (12). thru (14). to align holes.

(3). Remove adapter, hoist and eyebolts.

(15). Secure retainer to nut with two screws;

(4). Check that hub is fully seated on mast.

lockwire screws.

Page 402

Revision 20

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MD Helicopters, Inc.

MAINTENANCE MANUAL

Ensure that no washers are

Excessive lead-lag load applied

CAUTION

used under screwheads and that

to the main rotor blades during

screwheads are free of burrs.

ground handling can result in damage to the

elastomeric damper buns and failure of the

damper assembly. Operators and mainte

(16). Verify that screwheads do not project

nance personnel should use extra caution to

more than 0.020 inch (0.508 mm) above

avoid lead-lag loads in excess of 35 pounds

hub upper surface, for adequate

(155.68 N) at the tip of the main rotor

clearance between screwheads and

blades.

driveshaft flange.

NOTE:

(17). Connect scissors crank to main rotor

D Refer to MDHS Notice DN-45.2 for infor

hub lower shoe and/or to scissors link.

mation concerning required modification

of dampers produced prior to October

NOTE: Ensure pitch control rods are installed

1979. If lead-lag dampers, P/N

at same locations from which removed.

369D21400-501 are installed, they must

be modified to M50452 or be replaced

with P/N 369D21400-503 dampers.

(18). Install five pitch control rods to pitch

D If one or more main rotor blades strike an

housings (Ref. Sec. 62-30-00, Pitch

object while rotating or the drive system

Control Rod Replacement).

has been subjected to sudden stop, inspect

damper.

(19). Connect flexible boot to lower end of

rotor hub liner and secure with lock

4. Main Rotor Damper Replacement

wire (CM702).

A. Main Rotor Damper Removal

(20). Install main rotor drive shaft (Ref. Sec.

(1). Note and record location from which

63-10-00).

damper is to be removed from main

rotor hub.

(21). Install five main rotor blades.

NOTE: At reinstallation, if damper is not rein

stalled at same location, a check of and/or

(22). Perform main rotor blade droop angle

blade phasing is required.

check if hub is new or replacement.

(2). Support blade parallel to ground.

(23). Perform main rotor hub balance (Ref.

(3). Remove damper.

Sec. 18-10-00, Main Rotor Hub

NOTE: If damper is to be reinstalled at same lo

Balance Procedure) if a new or rebuilt

cation, do not disturb damper clevis, jam

hub is installed.

nuts or turnbuckle setting. Otherwise, blade

phasing is required at reinstallation of

damper.

3. Main Rotor Damper

(4). If damper is not to be reinstalled,

(Ref. Figure 603) A main rotor damper is

remove bushing from damper ear and

attached to each pitch housing of the rotor

retain with hub.

hub. The damper is connected to the inboard

B. Main Rotor Damper Installation

trailing edge of the associated main rotor blade

by an adjustable clevis to prevent lateral

(1). Check, and if necessary, preset main

vibrations from occurring in main rotor blades.

rotor damper length (Ref. Nominal

Neither damper travel nor stiffness is adjust

Damper Adjustment Procedure). Leave

able on the helicopter. Phasing of rotor blades

jamnuts fingertight.

is affected by turnbuckle adjustment. Any

phasing problem caused by a defective damper

NOTE: Ensure that bushing is installed in

should be corrected by replacing damper.

large hole of damper ears.

Page 404

Revision 36

62-20-00

MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

(2). With damper rotational direction decal

(2). Store all five dampers together in

facing outboard so it can be read, attach

horizontal position for minimum of six

damper ears to pitch housing lug with

hours. Preferred ambient temperature

bolt (head up), washers, and nut.

during storage is 55° to 85°F (13° to

Torque nut to 30 - 60 inch-pounds

30°C).

(3.39 - 6.78 Nm) and install cotter pin.

(3). Set damper length, centerline-to-cent

(3). Adjust main rotor blade phasing for

erline of bolt attach holes, for initial

associated main rotor blade.

installation.

369D/E

(4). After final phasing adjustments, torque

8.229 ±0.005 inch (209.017 ±0.127 mm)

jamnuts to 95 - 110 inch-pounds

369F/FF

(10.73 - 12.43 Nm). Safety jamnuts to

8.132 ±0.005 inch (206.553 ±0.127 mm)

turnbuckle with new lockwire. Lock

500N

wire must be located out-board, away

8.132 ±0.005 inch (206.553 ±0.127 mm).

from pitch housing.

(4). Install dampers on helicopter.

NOTE: Threaded end of damper turnbuckle

NOTE: If ground rock or stick shake is noted,

shaft must protrude through clevis base a

complete following step.

minimum of two full threads and must clear

blade damper attach fitting.

(5). Length of damper may be adjusted

after initial setting by checking main

(5). Connect damper to blade.

rotor system balance (Ref. Sec. 18-10,

(6). Remove blade support.

Main Rotor Balancing Procedure).

Check of main rotor system balance

5. Main Rotor Damper Nominal Adjustment

should be accomplished only after main

rotor blades have been tracked.

(1). Remove all five main rotor blade

If more than four flats turn of

dampers from helicopter if installed.

CAUTION

turnbuckle adjustment is neces

NOTE: If dampers are being replaced, do not

sary to correct balance, return to step (1).

mix part numbers.

and repeat procedure.

Page 405

62-20-00

Revision 20

CSP-HMI-2

MD Helicopters, Inc.

MAINTENANCE MANUAL

SCREW (2 PLACES)

(NOTE 2)

MAST

LOCKNUT

RETAINER

0.020 INCH (0.508 MM)

RETAINER

LOCKWIRE

MAXIMUM SCREW HEAD

HEIGHT ABOVE HUB

SCREW

LOCKNUT

DRIVE SHAFT

MAST

SEAL

RETAINER

SEAL RETAINER

SAFETYING

LOCKNUT AND SEAL

INSTALLATION

LOCKNUT

MAIN ROTOR

HUB

PITCH HOUSING

ASSEMBLY

SHIMS / SHIM WASHERS

(NOTE 4)

LOWER

SHOE

SHOULDERED BUSHING

PITCH

MAIN ROTOR MAST

CONTROL

ROD

FLEXIBLE BOOT

NOTES:

EDGE OF BUSHING MUST PROTRUDE A

NOTE 1

MINIMUM OF 0.010 INCH (0.254 MM) TO A

MAXIMUM OF 0.060 INCH (1.524 MM) ABOVE

ROTATING SWASHPLATE

OUTSIDE SURFACE OF PART AFTER NUT IS

TIGHTENED.

IF LOCKNUT AND RETAINER SCREWHOLES

DO NOT MATCH WITHIN CORRECT TORQUE

RANGE, LOCKNUT IS TO BE INVERTED.

WASHER(S) AS REQUIRED FOR BOLT END

NOTE 3

TO SWASHPLATE BOOT CLEARANCE.

SHIMS / SHIM WASHERS USED TO FILL GAP

ON SHOULDERED BUSHING SIDE.

SCISSORS CRANK

G62-2005A

Figure 402. Main Rotor Hub − Installation

Page 406

Revision 20

62-20-00

MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

MAIN ROTOR HUB

INSPECTION/CHECK

1. Main Rotor Hub Balancing − General

form of crescent-shaped grooves. If

chafing wear exists, repair or replace.

(Ref. Sec. 18-20) Main rotor hub balancing is

Chafed area must be cleaned up before

accomplished by adding or removing weight

measuring depth of damage to deter

(flat washers) as required at the lead-lag

mine housing serviceability.

bolts. Analysis of main rotor hub balance is

accomplished using instrumentation that

(3). Inspect droop stop ring for corrosion,

measures and localizes vibrations due to main

dents and scratches. If defects are

rotor hub imbalance. Data provided by the

found, repair or replace.

instrumentation is plotted on a chart designed

NOTE: To inhibit corrosion, spray droop stop

to indicate how much weight must be added or

ring, rollers and pitch bearings with rust in

removed from the lead-lag bolt. No other

hibitor (CM232).

means of balancing is to be used.

(4). Inspect droop stop roller for flat spots,

2. Main Rotor Blade Phasing Check and/or

pit marks and looseness on roller shaft.

Adjustment

(5). Inspect striker plate for dents and pit

Main rotor blade phasing (alignment) is

marks that exceed 0.030 inch (0.762

necessary at damper installation or replace

mm) depth. Damage exceeding this

ment, and may be necessary if there is ground

limit requires replacement of striker

rocking, or if one-to-one lateral (main rotor)

plate.

vibration occurs during flight (Ref. Main Rotor

Damper Nominal Adjustment).

(6). Press each pitch housing downward

several times and check for evidence of

3. Main Rotor Hub Inspection

binding pitch bearing or droop restrain

er follower. Inspect visible portion of

droop restrainer for cracks and follower

Consumable Materials

spring for breaks.

(Ref. Section 91−00−00)

Item

Nomenclature

NOTE: Do not remove tetrafluoroethylene

CM232

Rust inhibitor spray

(TFE) debris which works out of pitch bear

ing edge. Debris is normal and helps lubri

cate bearing. Removal of debris increases

(1). Inspect pitch housing for scratches,

bearing wear rate.

nicks and cracks. No cracks are permis

sible. Scratches and nicks must be

(7). Use bright light and 5-power magnify

cleaned up before measuring depth of

ing glass to inspect all main rotor hub

damage to determine housing service

lead-lag links (Ref. Figure 802) for

ability.

discoloration, pitting, intergranular

cracks or stress corrosion cracks. Any

(2). Inspect sleeve bushing for snug fit in

discoloration or pitting is evidence of

pitch housing arm clevis lug (Ref.

more than superficial corrosion and

Figure 805); lug must not show evi

main rotor hub must be removed for

dence of wear caused by bushing

replacement of lead-lag links.

movement. Maximum allowable

diameter for hole in bushed lug is

NOTE: Normal or premature overhaul requires

0.5004 inch (12.71016 mm); for un

visual inspection plus dye-penetrant in

bushed lug, not more than 0.3135 inch

spection of links for same conditions.

(7.9629 mm). Inspect inner surfaces of

all pitch housing arm clevis lugs for

(8). Inspection lead-lag link stop for broken

chafing caused by misaligned pitch

spring, cracks, breaks or visible bond

control rod end bearings. Chafing is in

line cracks.

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MD Helicopters, Inc.

CSP-HMI-2

MAINTENANCE MANUAL

(9).

Inspect interiors of lead-lag bolts using

(e). Reinstall screw, nut, washers and

bright light and 5X glass for cracks or

balance hardware removed in step 2.

corrosion per Lead-Lag Bolt Inspection.

Ensure hardware is installed exactly

as removed. Torque MS21042L08

(10).

Inspect each striker strip for cracks,

locknut on screw to 20 - 35 inch-

deformation and badly worn contact

pounds (2.26 - 3.95 Nm). Torque

surfaces.

MS21042L3 locknut on screw to 30 -

60 inch-pounds (3.39 - 6.78 Nm).

(11).

Inspect all parts of main rotor hub for

Coat exposed screw threads, washers

cracks, breaks, scratches and nicks.

and nut with sealant (CM420).

(Refer all questionable damage to

MDHI for disposition.)

NOTE: Excessive amount of sealant can unbal

ance rotor system. Apply light but thorough

(12).

Inspect lower shoe scissors attach

coat of sealant.

bearings for binding, looseness in bore

(f). Install new cotter pin to secure nut to

and wear. Maximum wear limits are

lead-lag bolt.

0.010 inch (0.254 mm) radial and 0.020

inch (0.508 mm) axial.

NOTE: There are prebalanced rotor hubs in

service. Lead-lag bolts of prebalanced hubs

(13).

Inspect each of five main rotor reten

may contain balancing hardware. If so, re

tion strap packs (Ref. Main Rotor Strap

move balancing hardware to perform in

Pack Lamination Inspection) at

spection. Each set of removed hardware

specified intervals (Ref. Sec. 5-10).

should be tagged or color-coded to ensure

(Ref. MDHI Notices DN-154 / EN-44 /

correct reinstallation.

FN-33 for specific inspection require

ments.)

5. Main Rotor Strap Pack Lamination

Inspection

4. Lead−Lag Bolt Inspection

CAUTION

Consumable Materials

D Figure 601 and Figure 602 depict the

(Ref. Section 91−00−00)

main rotor hub and strap pack assembly

Item

Nomenclature

disassembled for clarity of location and

CM318

Primer

area to be inspected for cracks. Under no

circumstances should the strap pack or

CM420

Sealant

main rotor hub assembly ever be disas

sembled in the field. MDHI and MDHI

(1). Inspect interiors of lead-lag bolts using

Approved Licensees are the only ap

bright light and 5X glass for cracks or

proved repair stations for main rotor hub

corrosion.

assembly overhaul.

D If a hub assembly or strap pack assembly

(a). Remove cotter pin securing nut to

(other than new parts in storage) are sub

lower end of lead-lag bolt. Do not

jected to extended periods of non-use,

disturb torque on nut or remove nut.

whether installed on the helicopter or not,

the strap assembly should be inspected

(b). Remove screw, nut, washers and

critically for corrosion and pitting before

balance hardware, if installed, from

return to service. If corrosion is found on

lead-lag bolt.

the strap pack assemblies, contact MDHI

for disposition.

(c). Inspect bolt interior. Treat minor

surface corrosion if noted. If corrosion

D It is acceptable to operate a helicopter

pitting or cracks are noted remove

with a hub assembly having a strap pack

and replace hub.

with up to two failed laminates in any one

leg of the strap assembly. When a lami

(d). Swab entire ID of bolt with primer

nate in the strap assembly fails, the re

(CM318).

maining laminates pick up and carry the

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MD Helicopters, Inc.

MAINTENANCE MANUAL

load. This increased load causes slightly

areas of the outboard shoes and pitch

more elongation in the remaining lami

housing assemblies.

nates of that leg thus shifting the mass of

the rotor system. Any time a vibration de

(5). Using a 10X magnifying glass, visually

velops or there is an increase in vibration

inspect the edge of strap pack lami

level over a short period of time, the main

nates on both sides at outboard end of

rotor strap pack assembly should be in

blade pitch housing (area between

spected for cracked or failed laminates.

outboard shoes).

(6). Use the following as acceptance/rejec

NOTE: Conduct inspection indoors, if possible,

tion criteria for laminate inspection:

or in a shaded area to eliminate glare of sun

or bright outdoor light. To facilitate inspec

(a). A laminate has failed if cracked in

tion, field fabricate and use plastic inspec

tongue area or in lead and lag legs of

tion tool and wooden probe (Ref Figure 602).

the same laminate.

(1). Remove main rotor blades.

(b). Reject strap pack and return hub

for overhaul when:

(2). If required, trim teflon from edges of

laminates using a aluminum chisel.

1). Three or more laminates in a

Fabricate from stock 0.250 x 6.00 x

single strap pack have failed.

0.100 inch (6.35 x 152.4 x 2.54 mm).

Carefully scrape excess interlaminate

2). Three or more laminates in a

teflon sheets from both sides of strap

single strap pack are cracked in

pack between top and bottom shoes at

the same lead or lag leg.

outboard attachment bolt of all five

strap packs.

3). One laminate is cracked at the

outboard end in the area between

NOTE:

outboard shoes (Ref. Figure 602).

D Do not pry at strap pack assemblies with

4). There are two or more gaps in the

sharp or hard edged tools. If edges become

same strap pack. A single gap in

nicked or laminates get scratched, addi

any one strap pack assembly is

tional cracking can occur thus causing

allowed.

hub replacement.

(7).

Visually inspect strap pack assemblies

D Where accessible, ends of acceptable

for evidence of corrosion. If corrosion is

cracked or broken laminates should be

found on strap pack laminates contact

taped to prevent scratching and damag

MDHI service department for disposi

ing of adjacent laminates.

tion.

(3).

(Ref. Figure 602) Field fabricate plastic

(8).

Using a blunt-nosed wooden or pheno

tool. Run plastic inspection tool in both

lic pin, pencil size with 1/16 inch

directions along each laminate, feeling

(1.5875 mm) radius point, probe at the

for a ”catch” from a crack on a single

upper and lower strap laminations at

laminate. Use the wooden or phenolic

the outboard ends of the blade pitch

probe and probe at upper and lower end

housings for evidence of laminate

of pack. Failed laminate in lead or lag

failure. A failed laminate, either at the

will move away from the other lami

lead or lag end of the strap pack, will

nates.

move away from the other laminates. If

the adjacent upper and lower laminates

(4). Using a light and mirror, visually

remain in tension under the probing

inspect each of the main rotor strap

operation, no laminate failures have

pack assemblies for evidence of cracks

occurred. Refer to Step (5). Caution for

or breaks in strap pack laminates in the

gap limitations.

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HANDBOOK OF MAINTENANCE INSTRUCTIONS FOR MDHI 369D/E/FF-500/600N HELICOPTERS (ISSUED: 1990) - page 17