Enstrom TH-28/480 Series. Maintenance Manual (2020)

SECTION 1

INTRODUCTION

1-1. Maintenance Manual Arrangement

The maintenance manual sections divide the aircraft into major systems and related

subsystems to provide maintenance procedures required for proper system function and

optimum component service life. Each section details the following maintenance functions for

the associated subsystems and components, if applicable:

General Description

Troubleshooting

Adjustment/Rigging

Removal

Disassembly

Inspections (other than Periodic Inspections)

Repair

Assembly

Installation

1-2. Aircraft Effectivity

The maintenance data presented in this manual is applicable to all TH-28, 480, and 480B model

Enstrom helicopters with standard equipment. Optional equipment maintenance procedures are

included in the TH-28/480 Series Maintenance Manual for common optional equipment that is

installed before aircraft delivery (This does not include avionics installations).

1-3. Maintenance Manual Supplements

Maintenance procedures for optional equipment may be provided in maintenance manual

supplements. These supplements are part of the TH-28/480 Series Maintenance Manual when

an aircraft is equipped with optional equipment which requires a maintenance manual

supplement. The following optional equipment supplements are applicable to the TH-28/480

Series Maintenance Manual.

Supplement 1:

Air Conditioning System, P/N 4220176-( ), Revision 8, Dated: May 1/17.

Supplement 2:

Emergency Pop-Out Floats, P/N 4220091-1 and 4220091-3, Revision 3,

Dated: Mar 21/16.

Supplement 3:

Gyrocam Dual or Triple Sensor Camera System, Dated: Feb 8/08.

Supplement 4:

Chelton Flightlogic EFIS System, Revision 1, Dated: Nov 9/10.

Supplement 5:

Avionic Systems, Revision 17, Dated: May 23/19.

Supplement 6:

Partial Wide Instrument Panel, Dated: Nov 15/10.

Supplement 7:

Bambi Bucket Interface Kit, Dated: Apr 30/13.

Supplement 8:

G1000H Integrated Flight Control System, Revision 2, Dated: Oct 18/19.

Rev. 26

MM-1-3

Feb 28/2020

1-4. Maintenance Manual Changes and Revisions

Subsequent to the publication of the initial issue of this manual, changes in equipment, support

concepts and procedures, as well as information developed by experience may affect the

contents of this manual. To ensure that coverage in the manual continues to reflect such

changes, revised information is released by one of the following methods:

1. Revision - A revision alters portions of the manual by replacement, addition, and/or

removal of pages.

2. Reissue - A reissue of this manual will occur when the amount of changes warrants

complete reissue.

3. Service Directive Bulletins - Used to direct the owner/operator and/or maintenance

personnel to make mandatory changes, improvements, or inspections to the aircraft

applicable to the entire fleet or a segment of the fleet that are typically safety/airworthiness

related. The information provided in the Service Directive Bulletins will be incorporated in

the maintenance manual as needed at a later date. At the time of incorporation, the Service

Directive Bulletin is superseded by the maintenance manual, and accomplishment or sign-

off of the Service Directive Bulletin in the maintenance records book is no longer required.

A detailed entry should be made in the maintenance records to indicate that the Service

Directive Bulletin is superseded by the maintenance manual.

4. Service Information Letters - Used to transmit information, recommendations, and general

service instructions to the aircraft owner/operator and/or maintenance personnel applicable

to the entire fleet or a segment of the fleet. The information provided in the Service

Information Letters will be incorporated into the maintenance manual as needed at a later

date.

5. Service Instructions - Used to provide the owner/operator and/or maintenance personnel

with information that is applicable to specific aircraft and does not meet the criteria of a

Service Information Letter or Service Directive Bulletin. Service Instructions will not be

distributed to the entire fleet.

Enstrom distributes maintenance manual revisions and reissues in electronic form via the

Enstrom Helicopter website: www.enstromhelicopter.com (follow the applicable link under the

Technical Publications section of the Technical Support page). Revision update notices are sent

via email to owners and operators who are registered with Enstrom. Registration to receive

publication mailing notifications can be coordinated through the Enstrom Technical Publications

Administrator. A complete manual hardcopy may be ordered through Enstrom Customer

Service.

Service Information Letters and Service Directive Bulletins incorporated into the maintenance

manual are logged in the Service Information Letter Index or the Service Directive Bulletin Index

(as appropriate) located on the Enstrom Helicopter website: www.enstromhelicopter.com (follow

the applicable link under the Technical Publications section of the Technical Support page).

Each index numerically lists all Service Information Letters and Service Directive Bulletins,

respectively, and identifies those which have been incorporated into the maintenance manual.

All Service Information Letters and Service Directive Bulletins are also located under the

Technical Publications section of the website.

Notice of recently released Service Information Letters and Service Directive Bulletins is

provided via email notification. Registration to receive publication mailing notifications can be

coordinated through the Enstrom Technical Publications Administrator.

Rev. 26

MM-1-4

Feb 28/2020

SECTION 2

GENERAL INFORMATION

TABLE OF CONTENTS

Paragraph

Description

Page

Table of Contents

MM-2-1

2-1.

General Description

MM-2-3

2-2.

General Arrangement

MM-2-3

2-3.

Principal Dimensions

MM-2-3

2-4.

Turning Radius

MM-2-3

2-5.

Fuselage

MM-2-3

2-6.

Tailcone

MM-2-3

2-7.

Landing Gear

MM-2-3

2-8.

Cabin

MM-2-4

2-9.

Cabin Doors

MM-2-4

2-10.

Seats

MM-2-4

2-11.

Engine Assembly

MM-2-5

2-12.

Engine Compartment Cooling

MM-2-5

2-13.

Flight Controls

MM-2-9

2-14.

Power Train

MM-2-9

2-15.

Main Rotor Assembly

MM-2-9

2-16.

Tail Rotor Assembly

MM-2-9

2-17.

Cabin Ventilation

MM-2-9

2-18.

Operating Limitations and Restrictions

MM-2-9

2-19.

Placards

MM-2-9

2-20.

Vendor Information

MM-2-11

2-21.

Special Tools

MM-2-13

2-22.

Torque Data

MM-2-17

2-23.

Consumable Parts List

MM-2-22

2-24.

Taper Pin Size Chart

MM-2-23

Rev. 26

MM-2-1

Feb 28/2020

maintenance on the seats or the cockpit area. Both seats use a composite bucket mounted on a

pedestal assembly. A four point restraint system with adjusters in the lap and shoulder belts and

an inertia reel mounted on the back of the seat pedestal are an integral part of the seat.

2. Passenger Seats: The passenger seats are mounted to the cabin backwall and

fold up to the stowed position when not in use and use a combination diagonal shoulder

harness and lap belt restraint system.

C. Inertia Reel Shoulder Harness: An inertia reel and shoulder harness is incorporated

in all seats. There is no independent control to manually lock the harness. With the shoulder

straps properly adjusted, the reel strap will extend to allow the occupant to lean forward;

however, the reel automatically locks when the helicopter encounters an impact force of 2 to 3

"G" deceleration. To release the lock, it is necessary to lean back slightly to release tension on

the lock.

2-11. Engine Assembly

A. The TH-28/480 series helicopters are equipped with a Rolls-Royce 250-C20W free

turbine, turboshaft engine rated at 420 SHP (313 kW); however, engine power is limited

depending on model and drive system configuration of the helicopter (Refer to Table 2-1). Refer

to the Rolls-Royce 250-C20 Operation and Maintenance Manual (10W2) for a complete

description of the engine assembly and its sub-components.

Table 2-1. Engine Power Limitations

Helicopter Model

Takeoff Rating

Maximum Continuous

(5 minute maximum)

Power

TH-28 and 480

285 SHP (213 kW)

256 SHP (191 kW)

480 equipped with

290 SHP (216 kW)

268 SHP (200 kW)

Increased Rotor Speed Kit

(P/N 4230002)

480B

305 SHP (227 kW)

277 SHP (206 kW)

2-12. Engine Compartment Cooling

A. The engine compartment is convection cooled and augmented by air movement

created by the airfoil shaped spokes in the upper pulley.

480B serial number 5114 and subsequent are equipped with fuselage panels/cowls

that have additional holes to increase the cooling efficiency of the engine compartment and can

be equipped with Engine Access Panels, P/N 4220150, to allow aircraft operation at an

increased maximum ambient temperature limit. 480B serial numbers 5087 through 5113 can be

equipped with the Increased Cooling Kit, P/N 4230031, for operation at the increased maximum

ambient temperature limit.

Rev. 26

MM-2-5

Feb 28/2020

2-20. Vendor Information

A. The following components listed in Table 2-2 are to be maintained I/A/W the

manufacturer's instructions to ensure the continued airworthiness of the aircraft.

B. The owner/operator is responsible for ensuring that current maintenance publications

are available to ensure continued airworthiness of the aircraft.

Table 2-2. Vendor Contact Information

Component

Part Number

Manufacturer

Rolls-Royce

450 S. Meridian Street

Engine

250-C20W

Indianapolis, IN 46206

Tel: (317) 230-2000

http://www.rolls-royce.com/

Thales Avionics Inc. (Auxilec)

140 Centennial Avenue

Starter/Generator

524-080

Piscataway Township, NJ 08854

Tel: (732) 494-6300

https://customeronline.thalesgroup.com/en

Skurka Aerospace, Inc.

4600 Calle Bolero

150SG117Q-3-1

Starter/Generator

Camarillo, CA 93011

150SG117Q-4-1

Tel: (805) 484-8884

http://www.skurka-aero.com/

Thales Avionics Inc. (Auxilec)

140 Centennial Avenue

Generator Control

VR1528-11B

Piscataway Township, NJ 08854

Unit (GCU)

Tel: (732) 494-6300

https://customeronline.thalesgroup.com/en

Avionic Instruments, LLC

Generator Control

1414 Randolph Avenue

Unit

GCSG501-2

Avenel, NJ 07001

(GCU)

Tel: (732) 388-3500

http://www.avionicinstruments.com/

Marathon Power Technologies

P.O. Box 8233

Battery*

TSP-1728-20-17SP100

Waco, TX 76712-8233

Tel: (254) 776-0650

http://www.mptc.com/

Teledyne Battery Products (Gill Batteries)

840 West Brockton Avenue

Redlands, CA 92374

Battery**

G-641

Tel: (800) 456-0070

Tel: (909) 793-3131

http://www.gillbatteries.com/

Aerotech

8354 Secura Way

Fuel Cells

4122052-“X”

Santa Fe Springs, CA 90670

(Standard)

Tel: (562) 696-1128

http://www.aerotechservicesinc.com/

Rev. 26

MM-2-11

Feb 28/2020

Table 2-2. Vendor Contact Information

Component

Part Number

Manufacturer

Zodiac Aerazur Caudebec

Fuel Cells

4122009-“X”

4, rue Lesage-Maille

Caudebec 76320, France

Tel: +33 (1) 6486-6922

Fuel Cell Crossover

500123

http://www.zodiacaerospace.com/en/zodiac-

aerosafety-systems-elastomer

Zodiac Aerazur Caudebec

4, rue Lesage-Maille

Caudebec 76320, France

Vent Crossover

500122

Tel: +33 (1) 6486-6922

http://www.zodiacaerospace.com/en/zodiac-

aerosafety-systems-elastomer

Airwolf Aerospace LLC

15369 Madison Rd.

Tension-Torsion (TT Strap)

Middlefield, OH 44062-8404, U.S.A.

AA-ECD-084-480

Tel: (440) 632-1687 / Fax: (440) 632-1685

(STC SR03465CH)

www.airwolfaerospace.com /

info@airwolfaerospace.com

Breeze-Eastern Corporation

35 Melanie Lane

Whippany NJ, 07981 U.S.A.

2A20B-17149-2

(800) 929-1919 / (973) 602-1083 / (973) 602-1090

Fax: (973) 739-9344

customerserives@breeze-eastern.com

Cargo Hook

www.breeze-eastern.com

(option)

Onboard Systems International, Inc.

13915 NW 3^rd Court

Vancouver, WA 98685 U.S.A.

528-023-01

Tel: (800) 275-0883 / (360) 546-3072

Fax: (360) 546-3073

www.onboardsystems.com

This is the standard battery for the TH-28 and 480. Refer to the correct publication if an optional or

special battery is installed.

** This is the standard battery for the 480B. Refer to the correct publication if an optional or special

battery is installed.

Rev. 26

MM-2-12

Feb 28/2020

2-22. Torque Data

A. Unless specified in Table 2-4 and/or in this manual’s maintenance procedures or as

called out in the component manufacturer’s specifications, all hardware should be torqued to the

recommended torque values listed in Tables 2-5 through 2-13.

NOTE

The following table does not contain all of the special torque values found

in this maintenance manual.

Table 2-4. Special Torque Values

Location

Torque Value

Airframe

a. Tailcone Attachment Bolts

240 in-lb/27.3 Nm

b. Landing Gear Oleo Pivot Points (all)

(¹)

b. Landing Gear Leg/Drag Strut Pivot Points (all)

40-60 in-lb/4.5-6.8 Nm

Flight Controls

a. Dogleg to Lower Swashplate Nut

40-60 in-lb/4.5-6.8 Nm

b. Dogleg to Push/Pull Rod Nut

130-140 in-lb/14.7-15.8 Nm

c. Upper Swashplate Guidetube Nuts

240 in-lb/27.3 Nm

Main Rotor Transmission

a. Mast Nut

450 ft-lb/613.6 Nm

b. Attachment Bolt Nuts

240 in-lb/27.3 Nm

c. Pinion Nut

250 ft-lb/340.9 Nm

d. Tail Rotor Coupling Bolt

100-140 in-lb/11.3-15.8 Nm

e. Magnetic Pick-up

60-65 in-lb/6.8-7.3 Nm

Main Rotor Hub

a. Blade Attachment Nut

50 ft-lb/68.2 Nm

b. Damper Pivot Nut

190 in-lb/21.6 Nm

c. Drag Link Nut

140 in-lb/15.8 Nm

d. Flapping Bearing Reservoir Cap

10-20 in-lb/1.1-2.3 Nm

e. Flapping Pin Nut

150-175 ft-lb/204.5-238.6 Nm

Lamiflex Bearing Retention Nut

5-15 in-lb/0.6-1.7 Nm

g. Lower U-block Nut

50 ft-lb/67.8 Nm

Tail Rotor

a. Assembly Retention Bolt

300 in-lb/34.1 Nm

b. Blade Grip Bolts²

75 in-lb/8.5 Nm

c. Driveshaft Taper Pins

25 in-lb/2.8 Nm

d. Pitch Change Plate to Grip Attachment Bolts

50-70 in-lb/5.7-8.0 Nm

e. Thrust Bearing Retention Nut

80-90 ft-lb/109.1-122.7 Nm

1 Inch-Pound = 0.113 Newton Meter

1 Newton Meter = 8.851 Inch-Pound

1 Foot-Pound = 1.3558 Newton Meter

1 Newton Meter = 0.7376 Foot-Pound

¹ Refer to (para. 8-70.A).

² Torque for oversize bolts: 140 in-lbs/15.8 Nm maximum.

Rev. 26

MM-2-17

Feb 28/2020

Table 2-5. Torque Values for Nuts and Bolts

CAUTION THE FOLLOWING TORQUE VALUES ARE DERIVED FROM OIL FREE CADMIUM PLATED THREADS.

TORQUE LIMITS RECOMMENDED FOR INSTAL-

MAXIMUM ALLOWABLE TIGHTENING

LATION (BOLTS LOADED PRIMARILY IN SHEAR)

TORQUE LIMITS

(inch-pounds)

Thread Size

Tension type nuts

Shear type nuts MS20364

Nuts MS20365 and

Nuts MS20364 and

MS20365 and AN310

and AN320

AN310

AN320

(40,000 psi in bolts)

(24,000 psi in bolts)

(90,000 psi in bolts)

(54,000 psi in bolts)

FINE THREAD SERIES

8-36

12-15

7-9

10-32

20-25

12-15

1/4-28

50-70

30-40

100

5/16-24

100-140

60-85

225

140

3/8-24

160-190

95-110

390

240

7/16-20

450-500

270-300

840

500

1/2-20

480-690

290-410

1100

660

9/16-18

800-1000

480-600

1600

960

5/8-18

1100-1300

600-780

2400

1400

3/4-16

2300-2500

1300-1500

5000

3000

7/8-14

2500-3000

1500-1800

7000

4200

1-14

3700-5500

2200-3300*

10,000

6000

1-1/8-12

5000-7000

3000-4200*

15,000

9000

1-1/4-12

9000-11,000

5400-6600*

25,000

15,000

COARSE THREAD SERIES

8-32

12-15

7-9

10-24

20-25

12-15

1/4-20

40-50

25-30

5/16-18

80-90

48-55

160

100

3/8-16

160-185

95-100

275

170

7/16-14

235-255

140-155

475

280

1/2-13

400-480

240-290

880

520

9/16-12

500-700

300-420

1100

650

5/8-11

700-900

420-540

1500

900

3/4-10

1150-1600

700-950

2500

1500

7/8-9

2200-3000

1300-1800

4600

2700

The above torque values may be used for all cadmium-plated steel nuts of the fine or coarse thread series which have

approximately equal number of threads and equal face bearing areas. * Estimated corresponding values.

Table 2-6. Fittings, Tubing

6061-O & 5052-O

Steel Tube:

Fitting

Tubing OD

Aluminum-Alloy Tube:

Fitting or Nut Torque

Size

(inches)

Fitting or Nut Torque

(in-lb)

-2

1/8

20-30

75-85

-3

3/16

25-35

95-105

-4

1/4

50-65

135-150

-5

5/16

70-90

170-200

-6

3/8

110-130

270-300

-8

1/2

230-260

450-500

-10

5/8

330-360

650-700

-12

3/4

460-500

900-1000

Rev. 26

MM-2-18

Feb 28/2020

Table 2-7. Fittings, Hose Assemblies

Flexible Hose or Tube Fittings (excluding nylon pitot static lines)

Measurements based on Hose Inside Diameter or Fitting Size

Flex Hose and 6061-T6

Steel (Torque Limits

Aluminum Alloy Torque

Tube Size

(in-lb)

Fitting Size

Thread

Limits (in-lb)

(inches)

Min

Max

Min

Max

-3

3/16

3/8-24

140

-4

1/4

7/16-20

120

135

185

-5

5/16

1/2-20

120

180

230

-6

3/8

3/4-16

130

180

270

345

-8

1/2

3/4-16

300

400

450

525

-10

5/8

7/8-14

430

550

650

750

-12

3/4

1-1/6-12

650

800

900

1,100

Table 2-8. Fittings

Torque Limits (inch-pounds)

For Jamnuts and Fittings Without

For Gasketed Aluminum or Steel Fittings*

Gaskets* *

Nominal

AN924 Nut AN815

Tube

Fitting

Union

AN814 Plug

AN6289 Nut

Aluminum

Steel

O.D.

Thread

(inches)

Size

Min

Max

Min

Max

Min

Max

Min

Max

Min

Max

1/8

5/16-24

3/16

3/8-24

1/4

7/16-20

100

105

110

130

5/16

1/2-20

100

120

105

125

140

160

3/8

9/16-18

100

150

120

150

200

125

145

225

275

1/2

3/4-16

180

230

150

200

250

240

280

400

450

5/8

7/8-14

250

350

200

350

275

400

330

370

550

650

3/4

1-1/6-12

420

600

300

500

450

650

540

660

800

960

For use with O-rings and aluminum, asbestos, leather, Teflon, gaskets, or washers.

* * For combinations of materials (either jamnut, fittings, or boss), use the lowest applicable values shown.

Rev. 26

MM-2-19

Feb 28/2020

Table 2-9. Steel Fittings Using Jam Nuts or Straight Thread O-Ring Boss

Torque Limits (inch-pounds)

Thread Size

Tube Size

(inches)

Min

Max

-02

5/16-24

-03

3/8-24

105

-04

7/16-20

155

180

-05

1/2-20

170

180

-06

9/16-18

275

290

-08

3/4-16

480

515

-10

7/8-14

515

575

Table 2-10. Pitot Static System Nylon Fittings

Torque Limits

Nominal Tube

Thread Size

(inch-pounds)

O.D. (inches)

(inches)

Min

Max

1/4

7/16-20

Table 2-11. Pipe Plugs

Thread Size

Torque Limits

(inches)

(inch-pounds)

1/16-27 NPT

40 to 44

1/8-27 NPT

40 to 44

1/4-18 NPT

85 to 94

3/8-18 NPT

110 to 121

1/2-14 NPT

160 to 176

3/4-14 NPT

230 to 252

1-11-1/2 NPT

315 to 347

Rev. 26

MM-2-20

Feb 28/2020

Table 2-12. Crush Type Gaskets

NOTE

Turn the part until the sealing surfaces are in contact and then tighten to

the angle of turn listed for the appropriate thread size.

Thread Pitch On

Angle of Turn

Part to be

Tightened

(Threads per Inch)

Aluminum

Copper

135°

67°

135°

67°

180°

90°

180°

90°

270°

135°

270°

135°

270°

135°

360°

180°

360°

180°

Table 2-13. Minimum Prevailing Torque Values for Re-used Self-Locking Nuts

Bolt, or Screw Thread

Seating Torque

Prevailing Torque Max.

Prevailing Torque Min.

Size (inches)

(in-lb ±10%)

On or Off (in-lb)

4-40

0.5

6-32

1.0

8-32

1.5

AN3

2.0

AN4

110

3.0

AN5

190

5.0

AN6

345

110

9.0

AN7

545

150

12.0

AN8

850

220

16.0

If not listed in Table 2-13, a self-locking nut can be reused as long as a wrench is

required to turn it on the bolt.

Rev. 26

MM-2-21

Feb 28/2020

2-23. Consumable Parts List

A. Table 2-14 lists the consumable parts and lubricants that are normally used during

servicing or periodic inspection of the aircraft. The quantities listed reflect normal inspection

intervals; however, they may need to be adjusted if adverse operating conditions require more

frequent servicing or inspections.

B. Refer to the Rolls-Royce 250-C20 Series Operation and Maintenance Manual (10W2)

and the Rolls-Royce 250-C20 Series Illustrated Parts Catalog (10W4) for the consumable parts

required for servicing or periodic inspection of the engine.

NOTE

Obtain engine parts through the Rolls-Royce Parts Distribution System.

Enstrom does not stock engine parts for customer service use.

Table 2-14. Consumable Parts List

Item

Part Number †

Quantity

50 Hour Service

Grease

MIL-PRF-81322 and MIL-G-25537

As Required

Silicon Oil

L-45 or SF96-20

As Required

Oil

As Required

Oil

MIL-PRF-23699

As Required

O-ring

NAS1612-2

7 EA *

100 Hour Service/Inspection

Same as 50 hour Requirements

Crush Washer

AN900-8 or MS35769-9

1 EA

Crush Washer

AN900-10 or MS35769-11

1 EA

Oil Filter

HP-1003

1 EA

Oil

MIL-PRF-23699

6 QTS

Oil

MIL-PRF-2105/API GL-5

7 PTS

O-ring

NAS1612-2

2 EA*

O-ring

NAS1612-8

4 EA*

O-ring

MS28778-6

1 EA*

200 Hour Service/Inspection

Same as 100 hour requirements

Filter Element - APM

AC-B283F-107

1 EA

O-ring - APM

M83248/1-138

1 EA

Filter Element - Purolator/Facet

038088-08

1 EA

Seal Kit - Purolator/Facet

1741125

1 EA

O-ring

NAS1612-2

3 EA*

Oil (ORC)

MIL-PRF-23699

7 OZ

300 Hour Service/Inspection

Same as 100 hour requirements

Fuel Filter Kit

1743645-02

1 EA**

Gasket

28-13107-15

1 EA*

NOTES:

Replace on condition

The external fuel filter is optional equipment and might not be installed on the aircraft.

†

Verify configuration, part number and quantity with latest revision of illustrated parts

catalog, service letters, and service bulletins as required.

Any grade internal combustion engine motor oil.

 Refer to the Rolls-Royce 250-C20 Series Operation and Maintenance Manual (10W2) for

engine oil change requirements.

Rev. 23

MM-2-22

Jul 3/15

2-24. Taper Pin Size Chart

Table 2-15 lists information pertaining to taper pin part numbers and physical properties.

NOTES

Always check the condition and security of taper pins at every inspection.

The dash number of the 28-16323 series taper pins is vibro-etched on the

head of the taper pin.

Table 2-15. Taper Pin List

Old Enstrom P/N

Current Enstrom P/N

Head Diameter

Grip Length

AN386-2-7A ¹

0.296 in / 7.5 mm

1.00 in / 25.4 mm

AN386-2-8A ¹

0.302 in / 7.6 mm

1.12 in / 28.4 mm

AN386-2-9A ¹

0.308 in / 7.8 mm

1.26 in / 32 mm

28-13600-3 ²

28-13623-25 ²

0.302 in / 7.6 mm

1.00 in / 25.4 mm

28-13600-4 ²

28-13623-27 ²

0.307 in / 7.7 mm

1.00 in / 25.4 mm

28-13600-5 ²

28-13623-29 ²

0.314 in / 7.9 mm

1.00 in / 25.4 mm

28-13623-31 ²

0.316 in / 8 mm

1.00 in / 25.4 mm

28-13600-7 ³

28-13623-13 ³

0.310 in / 7.8 mm

1.12 in / 28.4 mm

28-13600-8 ³

28-13623-17 ³

0.318 in / 8 mm

1.12 in / 28.4 mm

28-13623-15 ³

0.315 in / 8 mm

1.12 in / 28.4 mm

28-13600-6 ³

28-13623-11 ³

0.305 in / 7.7 mm

1.12 in / 28.4 mm

¹Standard

² Tail Rotor Transmission

³ Main Rotor Transmission

Rev. 26

MM-2-23

Feb 28/2020

SECTION 4

SERVICING, RECOMMENDED OVERHAULS, INSPECTIONS,

AND GENERAL MAINTENANCE

TABLE OF CONTENTS

Paragraph

Description

Page

Table of Contents

MM-4-1

4-1.

Servicing

MM-4-5

4-2.

Description

MM-4-5

4-3.

Fuel System

MM-4-14

4-4.

Servicing

MM-4-14

4-5.

Draining

MM-4-14

4-6.

Engine Oil System

MM-4-15

4-7.

Servicing

MM-4-15

4-8.

Draining

MM-4-16

4-9.

Overrunning Clutch

MM-4-19

4-10.

Servicing

MM-4-19

4-10.1

Draining

MM-4-20

4-11.

Main Rotor Transmission

MM-4-20

4-12.

Servicing

MM-4-20

4-13.

Draining

MM-4-21

4-13.1

Flushing

MM-4-21

4-14.

Oil Filter Replacement

MM-4-22

4-15.

Tail Rotor Transmission

MM-4-22.1

4-16.

Servicing

MM-4-22.1

14-17.

Draining

MM-4-22.1

4-17.1

Flushing

MM-4-22.2

4-18.

Main Rotor Dampers

MM-4-24

4-19.

Servicing

MM-4-24

4-20.

Main Rotor Flapping Bearings

MM-4-25

4-21.

Servicing

MM-4-25

4-22.

Draining

MM-4-25

4-23.

Lower Pulley Bearings

MM-4-29

4-24.

Servicing

MM-4-29

4-25.

Draining

MM-4-29

4-26.

Oleos

MM-4-30

4-27.

Servicing

MM-4-30

4-28.

Battery

MM-4-34

4-29.

Servicing

MM-4-34

4-30.

Lubrication

MM-4-34

4-31.

Description

MM-4-34

4-32.

Lower Pulley

MM-4-35

4-33.

Lubrication

MM-4-35

4-34.

Main Rotor Blade Grip

MM-4-35

4-35.

Lubrication

MM-4-35

4-36.

Main Rotor Flapping Bearings

MM-4-37

4-37.

Lubrication

MM-4-37

Rev. 26

MM-4-1

Feb 28/2020

SECTION 4

SERVICING, RECOMMENDED OVERHAULS, INSPECTIONS,

AND GENERAL MAINTENANCE

TABLE OF CONTENTS

Paragraph

Description

Page

4-38.

Tail Rotor Pitch Control Bearing

MM-4-37

4-39.

Lubrication, Preferred Method

MM-4-37

4-39.1.

Lubrication, Alternate Method

MM-4-38

4-39.2.

Blower Assembly Bearing

MM-4-38

4-39.3.

Lubrication

MM-4-38

4-39.4.

Tail Rotor Feathering Bearing

MM-4-38

4-39.5.

Lubrication

MM-4-38

4-40.

Recommended Overhaul Cycles

MM-4-39

4-41.

Periodic Inspections

MM-4-41

4-42.

General Information

MM-4-41

4-43.

Daily Inspection

MM-4-41

4-44.

Periodic Inspection Checklists

MM-4-41

4-45.

100 Hour Inspection

MM-4-43

4-46.

200 Hour Inspection

MM-4-57

4-47.

300 Hour Inspection

MM-4-59

4-48.

Special Scheduled Inspection

MM-4-61

4-49.

Special Inspections

MM-4-63

4-50.

General Information

MM-4-63

4-51.

Main Rotor Blade Strike/Sudden Stoppage (Minor)

MM-4-63

4-52.

Main Rotor Blade Strike/Sudden Stoppage (Major)

MM-4-64

4-53.

Tail Rotor Blade Strike/Sudden Stoppage

MM-4-65

4-54.

Hard Landing

MM-4-66

4-55.

Main Rotor Overspeed

MM-4-67

4-56.

Overtorque

MM-4-67

4-57.

Main Rotor or Tail Rotor Transmission Chip Indication

MM-4-68

4-58.

Engine Overspeed

MM-4-70

4-59.

Engine Overtemp

MM-4-70

4-60.

Maintenance Ground Run

MM-4-70

4-61.

Maintenance Test Flight

MM-4-73

4-62.

Ground Handling

MM-4-81

4-63.

Ground Handling Wheels

MM-4-81

4-64.

Installation/Removal

MM-4-81

4-65.

External Power

MM-4-82

4-66.

Parking

MM-4-82

4-67.

Leveling

MM-4-83

4-68.

Hoisting

MM-4-83

4-69.

Jacking

MM-4-83

4-70.

Cleaning

MM-4-89

4-71.

Exterior

MM-4-89

4-72.

Interior

MM-4-90

4-73.

Plexiglass

MM-4-90

Rev. 26

MM-4-2

Feb 28/2020

SECTION 4

SERVICING, RECOMMENDED OVERHAUL CYCLES, INSPECTIONS,

AND GENERAL MAINTENANCE

4-1. Servicing

4-2. Description - Servicing

Servicing of the TH-28 and 480/B is normally accomplished at specified hourly intervals.

Operators should take into consideration the environmental conditions and determine whether

more frequent servicing intervals are necessary. Refer to Tables 4-1 thru 4-7.1 and Figure 4-1

for approved fuels, oils, lubricants, intervals, and locations.

Table 4-1. Fuels, Lubricants, Specifications, and Capacities

SYSTEM/COMPONENT

SPECIFICATION

CAPACITY

Fuel - Standard

ASTM D1655, Jet A or A1

*(C-1)

91.7 U.S.Gals

(90.0 usable)

ASTM D6615, Jet B

347.08 Liters

MIL-T-5624, JP-4 or JP-5

(340.65 usable)

(See Note 6)

MIL-DTL-83133, Grade JP-8

(See Note 1)

Fuel - Crashworthy

ASTM D1655, Jet A or A1

*(C-1)

90.0 U.S.Gals

(89.7 usable)

ASTM D6615, Jet B

340.65 Liters

MIL-T-5624, JP-4 or JP-5

(339.51 usable)

(See Note 6)

MIL-DTL-83133, Grade JP-8

(See Note 1)

Engine Oil

MIL-PRF-7808 or

*(C-2)

12.0 U.S. Pints

MIL-PRF-23699

(See Note 2)

5.7 Liters

Overrunning Clutch

MIL-PRF-7808 (See Table 4-4)

3.8 U.S. Ounces

or MIL-PRF-23699

*(C-2)

(See Table 4-5)

110 ml

Overrunning Clutch

MIL-PRF-7808 (See Table 4-4)

6.5 U.S. Ounces

with Vented Clutch Oil Reservoir

or MIL-PRF-23699

*(C-2)

(If Equipped)

(See Table 4-5)

192 ml

Rev. 26

MM-4-5

Feb 28/2020

Table 4-1. Fuels, Lubricants, Specifications, and Capacities

SYSTEM/COMPONENT

SPECIFICATION

CAPACITY

Main Rotor Transmission

MIL-PRF-2105/API GL-5

*(C-3)

Dry -

(See Note 5)

6 U.S.Pints

2.84 Liters

Reservicing - 5.5

U.S. Pints

2.6 Liters

Main Rotor Transmission

MIL-PRF-2105/API GL-5

*(C-3)

Dry -

(See Note 5)

6.5 U.S.Pints

(Equipped with oil filter and cooling

installation)

3.1 Liters

Reservicing - 6.0

U.S. Pints

2.84 Liters

Tail Rotor Transmission

MIL-PRF-2105/API GL-5

*(C-3)

5 U.S.Ounces

(See Note 5)

150 ml

Main Rotor Dampers

L-45 or SF96-20 Silicone Oil

*(C-4)

Until Full

(See Note 8)

Main Rotor Blade Grips

MIL-G-25537 or MIL-PRF-81322

As Required

(See Notes 7, 9, 12)

*(C-8 or C-5)

Main Rotor Lead-Lag Bearings

MIL-G-25537 or MIL-PRF-81322

As Required

(See Notes 7, 10, 12)

*(C-8 or C-5)

Main Rotor Flapping Bearings

MIL-G-25537 or MIL-PRF-81322

As Required

(Grease Lubricated)

(See Notes 7, 10, 12)

*(C-8 or C-5)

Main Rotor Flapping Bearings

MIL-PRF-23699

*(C-2)

As Required

(Oil Lubricated)

(See Table 4-5)

Pitch Change Bellcrank Pivot

MIL-G-25537 or MIL-PRF-81322

As Required

Bearings

(See Note 7, 10, 12)

*(C-8 or C-5)

Upper Pulley Bearing

MIL-PRF-81322 (See Note 7)

*(C-5)

As Required

Lower Pulley Bearings

MIL-PRF-81322

*(C-5)

As Required

(Grease Lubricated)

(See Note 7)

(See Note 3)

Lower Pulley Bearings

MIL-PRF-23699

*(C-2)

.27 U.S. Ounces

(Oil Lubricated)

(See Table 4-5)

Dry - 8 ml

Reservicing - 6 ml

Blower Assembly Bearings

MIL-PRF-81322 (See Note 7)

*(C-5)

As Required

(See Note 11)

Tail Rotor Drive Shaft Bearings

MIL-PRF-81322 (See Note 7)

*(C-5)

As Required

Tail Rotor Pitch Control Bearing

MIL-PRF-81322 (See Note 7)

*(C-5)

As Required

Tail Rotor Feathering Bearings

MIL-G-25537 or MIL-PRF-81322

As Required

(See Notes 7, 10, 12)

*(C-8 or C-5)

Rev. 20

MM-4-6

Apr 25/13

Table 4-2. Servicing Intervals, Methods, and Locations

SYSTEM / COMPONENT

FREQUENCY

METHOD

LOCATION

(Fig. 4-1) & ** C-#

Fuel

As required

1 / C-1

Engine Oil

100 Hrs / As Required

Oil Can

2 / C-2

Overrunning Clutch

25 Hrs / As Required

Oil Can / Syringe

3 / C-2

(See Notes 4, 5 & 6)

Main Rotor Transmission

100 Hrs / As Required

Oil Can

4 / C-3

Tail Rotor Transmission

100 Hrs/ As Required

Oil Can

5 / C-3

Main Rotor Dampers

50 Hrs / As Required

Tool T-2896

6 / C-4

Main Rotor Blade Grips

50 Hrs

Grease Gun

7 / C-5

Main Rotor Lead-Lag Bearings

50 Hrs

Grease Gun

8 / C-5

Main Rotor Flapping Bearings

50 Hrs

Grease Gun

9 / C-5

(Grease Lubricated)

Main Rotor Flapping Bearings

600 Hrs / As Required

Oil Can

9 / C-2

(Oil Lubricated)

Pitch Change Bellcrank Pivot

50 Hrs

Grease Gun

10 / C-5

Bearing

Upper Pulley Bearing

100 Hrs

Grease Gun

11 / C-5

Lower Pulley Bearings

100 Hrs

Grease Gun

12 / C-5

(Grease Lubricated)

(See Note 3)

Lower Pulley Bearing

100 Hrs

Syringe

12 / C-2

(Oil Lubricated)

Blower Assembly Bearings

300 Hrs

Syringe

13 / C-5

(See Note 7)

Tail Rotor Drive Shaft Bearings

50 Hrs

Grease Gun

14 / C-5

Tail Rotor Pitch Control Bearing

100 Hrs

Syringe

15 / C-5

Tail Rotor Feathering Bearings

25 Hrs (See Note 8)

Grease Gun

16 / C-5

50 Hrs

Tail Rotor Teeter Bearings

50 Hrs

Grease Gun

17 / C-5

Collective Guidetube Bearing

50 Hrs

Grease Gun

18 / C-5

Cyclic Swashplate Bearing

50 Hrs

Grease Gun

19 / C-5

Tail Rotor Control Pivot Points

100 Hrs

Oil Can

20 / C-6

Pitch Change Bellcrank Inboard

50 Hrs

Oil Can

21 / C-6

Pivot Points

Collective Walking Beam Pivot

100 Hrs

Oil Can

22 / C-6

Strap Bushings

Lateral Push/Pull Rod

50 Hrs

Oil Can

23 / C-6

Trim Motor Attachment Points

50 Hrs

Oil Can

24 / C-6

Rev. 26

MM-4-9

Feb 28/2020

Table 4-2. Servicing Intervals, Methods, and Locations

SYSTEM / COMPONENT

FREQUENCY

METHOD

LOCATION (Fig. 4-

1) & ** C-#

Tail Rotor Pedal Pivot Points

100 Hrs

Oil Can

25 / C-6

Landing Gear Oleos

100 Hrs / As Required

26 / C-7

Battery

(See Note 1)

(See Note 2)

Ground Handling Wheel

As Required

Hand Pack

28 / C-5

Bearings

C-# refers to the fuel or lubricant in Table 4-1.

NOTE 1.

Service in accordance with manufacturer's instructions.

NOTE 2.

The battery is located in the right side of the engine compartment in a TH-28 and

480/B. An alternate location is in the baggage box.

NOTE 3.

Do not purge lubricate the lower pulley bearings. Refer to paragraph 4-33.

NOTE 4.

If the overrunning clutch (ORC) cover is equipped with a sight glass, service the

ORC when oil does not fill the sight glass.

NOTE 5.

If the overrunning clutch (ORC) cover is equipped with a sight glass and oil

completely fills the sight glass, the servicing interval can be extended to 100

hours. If the ORC cover is equipped with a sight glass and the ORC requires

servicing after less than 10 flight hours, inspect the ORC bearing housing seal

and power output shaft seal for leaks and replace the seal(s) as required. If the

ORC bearing housing and power output shaft seals are not leaking, replace the

double lip seals (2 each) in the engine gearbox assembly at or before the next

100 hour/annual inspection.

NOTE 6.

If the overrunning clutch (ORC) is equipped with a vented clutch oil reservoir, the

servicing interval can be extended to 100 hours. Service the vented clutch oil

reservoir if oil does not fill the reservoir sight glass. The oil level between the

reservoir sight glass and the ORC cover sight glass should be the same. Service

the reservoir until the oil level is just below the reservoir service port. Allow

sufficient time for the oil to flow into the ORC.

NOTE 7.

Do not purge lubricate the blower assembly bearings. Refer to paragraph 4-39.2.

NOTE 8.

Applicable for helicopters operating with infrequent inputs to the tail rotor pitch

control system (for example: extended flight with unchanging blade pitch).

Rev. 26

MM-4-10

Feb 28/2020

Table 4-6. Approved Domestic Commercial Oils

for MIL-PRF-2105/API GL-5

MANUFACTURER

MANUFACTURER'S DESIGNATION

Exxon Mobil Corp.

Mobil 1 Synthetic Gear Lubricant LS 75W-90

Mobil Delvac 1¹ Synthetic Gear Oil 75W-90

Mobilube HD LS 80W-90

Mobilube HD Plus 80W-90

Shell Oil Company

Shell Helix Racing Gear Oil 75W-90

Shell Spirax HD 80W90

BP Lubricants USA, Inc.

Castrol Syntrax Limited Slip 75W-90 (Syntec Gear Oil)

Table 4-7. Approved Commercial Greases

for MIL-PRF-81322

MANUFACTURER

MANUFACTURER'S DESIGNATION

Anderol Specialty Lubricants

Royco 22CF

Shell Oil Company

Aeroshell 22, 22CF

Table 4-7.1. Approved Commercial Greases

for MIL-G-25537

MANUFACTURER

MANUFACTURER'S DESIGNATION

Shell Oil Company

AeroShell Grease 14

¹ Mobil Delvac 1 75W-90 supersedes Mobil Delvac 75W-90 and Mobil SHC 75W-90.

Rev. 26

MM-4-12.1

Feb 28/2020

D. If the transmission is equipped with the oil filtration/cooling system, turn the battery

switch on and check the system for oil leaks and proper operation of the oil pump and pressure

switch. If required, prime the oil pump by disconnecting the oil line between the pressure switch

tee and the pump inlet and filling the line with oil. Reconnect the line and check the oil pump

and pressure switch for proper operation.

4-13. Draining - Main Rotor Transmission

A. Open the left side engine access panel.

NOTE

The chip detector is located on the front side of the oil filter housing if the

transmission is equipped with the oil filter and cooling installation.

NOTE

Transmissions equipped with an oil filter may be drained by removing the oil

filter (para. 4-14).

B. Place a trough under the chip detector located by the aft left side transmission mount

and use a suitable container to collect the oil.

C. Remove the chip detector from the quick disconnect receptacle.

NOTE

Tool T-0198-11 may be inserted in the base of the chip detector to drain the

oil.

D. Remove the quick disconnect receptacle from the transmission or the oil filter housing

to drain the oil.

E. When the transmission is drained, replace the crush washer on the receptacle and

reinstall until finger tight. Tighten an additional 90° and lockwire the receptacle.

F. Reinstall the chip detector.

4-13.1 Flushing - Main Rotor Transmission

A. Install the ground handling wheels and lower the wheels.

B. Set 1-1/2”/38 mm blocks under the left and right forward skid shoes and raise the left

side wheel.

C. Remove the upper plenum (para. 13-28).

D. Drain the oil from the gearbox (para. 4-13). (The oil may be drained by removing the

filter.)

E. Remove the oil filter from the gearbox.

F. Remove the pinion inspection plate from the transmission.

Rev. 26

MM-4-21

Feb 28/2020

G. Inspect the gears in accordance with SIL T-064 paragraph 6.1 (C).

H. Use a syphon sprayer with kerosene, mineral spirits or equivalent oil based solvent to

spray down the interior of the gearbox. Direct the aim of the sprayer around the inside of the

gearbox and the ring gear and carrier while turning the gearbox. (The objective is to introduce

sufficient volume of solvent to flush any debris out of the gearbox and drain it out the oil filter

housing.)

Allow the gearbox (main rotor) to drain completely.

NOTE

The previously installed oil filter may be reinstalled.

J. Reinstall the gearbox (main rotor) oil filter and hand tighten.

K. Add 4 quarts/3.9 l of the gear lube that is currently being used in the gearbox.

L. Rotate the gearbox (main rotor) by hand 7-10 revolutions.

M. Remove the oil filter and drain the gearbox while rotating the gearbox.

N. Allow gearbox (main rotor) to drain completely.

O. Inspect and clean the chip plug.

P. Install and secure the pinion cover plate in accordance with SIL T-064 paragraph 6.1 (E).

Q. Install a new oil filter (para. 4-14).

R. Service the gearbox (para. 4-12).

S. Remove the blocks and the ground handling wheels.

T. Install the upper plenum (para. 13-31).

4-14. Oil Filter Replacement - Main Rotor Transmission

NOTE

The following maintenance procedures only apply to aircraft equipped with the

main rotor transmission oil filter/cooling system.

A. Drain the oil from the transmission.

B. Remove the lockwire from the oil filter and remove the oil filter.

C. Lubricate the seal on the replacement filter with oil (MIL-PRF-2105).

D. Install the filter until the seal contacts the seal surface on the filter housing. Turn the

filter an additional ¾ turn and lockwire (.025) the filter to the chip detector assembly.

E. Service the transmission.

Rev. 26

MM-4-22

Feb 28/2020

F. Turn the battery switch on and check the system for oil leaks and proper operation of

the oil pump and pressure switch. If required, prime the oil pump by disconnecting the oil line

between the pressure switch tee and the pump inlet and filling the line with oil. Reconnect the

line and check the oil pump and pressure switch for proper operation.

4-15. Tail Rotor Transmission (See Figure 4-4)

4-16. Servicing - Tail Rotor Transmission

NOTES

Refer to Table 4-1 for system capacity and approved oils.

When the tail rotor transmission is properly serviced (5 oz./.147 l), the sight

glass will be completely full. The transmission oil level is serviceable until the

oil level is at the center of the sight glass.

A. Check the oil level of the transmission by using the sight plug located in the aft side of

the transmission. The transmission is serviceable until the oil level is at the center of the sight

glass. Raise and lower the tail to change the attitude of the aircraft to verify the level of the oil in

the transmission if a bubble is present in the sight glass.

NOTE

Check the transmission for leaking seals if servicing is required between

periodic inspections.

B. Remove the filler port located directly above the sight glass.

C. Add 5 oz./.147 l of oil if servicing the transmission after draining or slowly add oil until

oil flows from the filler port.

D. Install new O-ring and install the filler plug (10-16 in-lb/1.1-1.8 Nm) and lockwire

(.032) to the chip detector receptacle and the sight glass.

4-17. Draining - Tail Rotor Transmission

A. Remove the chip detector from the quick disconnect receptacle.

B. Place a suitable container under the receptacle.

C. Remove the quick disconnect receptacle and drain the transmission.

D. When the transmission is drained, replace the crush washer and secure magnetic

plug/chip detector (finger tight plus 135° but not to exceed 35 in-lb/4 Nm) and lockwire the

receptacle/magnetic plug to the sight glass and the filler plug after the transmission has been

serviced.

(1) Apply lubricant (MIL-PRF-2105) to the threads the chip detector prior to

installation.

E. Reinstall the chip detector.

Rev. 26

MM-4-22.1

Feb 28/2020

4-17.1 Flushing - Tail Rotor Transmission

A. Drain the oil (paragraph 4-17).

B. Remove the filler plug, sight glass, and top visual inspection plug (if not already

removed) from the gearbox.

C. Inspect the gears closely for cracked or missing teeth and the gearbox for damage.

D. Use a syphon sprayer with kerosene, mineral spirits, or equivalent oil-based solvent

to spray down the interior of the gearbox and flush any debris out of the gearbox. Direct aim the

sprayer around the inside of the gearbox to flush the input and output bearings, while rotating

the gearbox.

E. Loosely install the bottom drain plug, sight glass, and fill plug.

F. Add one-half quart of the gear lube that is currently used in the gearbox (Table 4-1).

G. Rotate the gears at least ten times to circulate the oil.

H. Remove the drain plug and drain the gearbox while rotating the gears.

Allow the gearbox to drain completely.

J. Install new O-ring and secure the sight plug (20-60 in-lb/2.3-6.8 Nm).

K. Install new crush washer and secure magnetic plug/chip detector (finger tight plus

135° but not to exceed 35 in-lb/4 Nm).

L. Service the gearbox (para. 4-16).

Rev. 26

MM-4-22.2

Feb 28/2020

4-28. Battery

4-29. Servicing - Battery

A. Service the battery I/A/W the manufacturer’s instructions.

4-30. Lubrication

4-31. Description - Lubrication

A. Lubrication of the TH-28/480 is normally accomplished at specified hourly intervals.

Operators should take into consideration the environmental conditions and determine whether

more frequent lubrication intervals are necessary. Refer to Tables 4-1 to 4-5 and Figure 4-1 for

approved lubricants, intervals, and locations.

B. Purge lubricate all bearings and remove the excess grease before performing the

post maintenance ground run. Follow the procedures listed below for lubricating the lower

pulley, main rotor blade grips, main rotor flapping bearings, and the tail rotor pitch control

bearing.

(1) For tail rotor feathering bearing lubrication, refer also to paragraph 4-39.4.

C. Lubricate the flight control pivot points sparingly to prevent the accumulation of dirt.

D. Remove the following panels and covers as required to service and lubricate the

aircraft:

(1) Keel access panels.

(2) Engine access panels.

(3) Transfer duct access panel.

(4) Tail rotor drive shaft covers.

Rev. 26

MM-4-34

Feb 28/2020

4-36. Main Rotor Flapping Bearings (See Figure 4-10)

4-37. Lubrication - Main Rotor Flapping Bearings

NOTE

Refer to paragraphs 4-20 through 4-22 if the main rotor hub assembly is

equipped with oil lubricated flapping bearings.

A. Purge lubricate the main rotor flapping bearings using the grease fitting located in the

recess of the inboard side of the universal block (See Figure 4-10).

4-38. Tail Rotor Pitch Control Bearing

4-39. Lubrication, Preferred Method - Tail Rotor Pitch Control Bearing

NOTE

Purge the needle prior to each use and lubricate the external surface of the

needle with grease to prevent seal damage.

A. Using a 6 cubic centimeter (cc) medical syringe and an 18 gauge hypodermic needle,

inject .5cc of grease into the bearing in two places, approximately 180 apart. Carefully insert

the tip of the needle under the lip of the seal where it contacts the inner race of the bearing. The

tip of the needle can be worked under the lip of the seal and into the bearing between the balls.

If the needle does not penetrate between the balls, the needle can be withdrawn and inserted in

another position on the bearing (Figure 4-11.1).

Figure 4-11.1. Tail Rotor Pitch Control Bearing Lubrication

B. Wipe the excess grease from the surface of the seal as necessary

Rev. 26

MM-4-37

Feb 28/2020

4-39.1. Lubrication, Alternate Method - Tail Rotor Pitch Control Bearing

WARNING

Use extreme caution when removing the seal to prevent from injuring

yourself or damaging the tail rotor pitch controls.

A. Using a small flat-blade screwdriver or small knife blade, remove the seal from the

inboard side of the bearing.

B. Hand pack the bearing with grease.

C. Reinstall the seal. Ensure it is properly seated.

4-39.2. Blower Assembly Bearing

4-39.3. Lubrication - Blower Assembly Bearing

A. Wipe the seal clean on the accessible side of the bearing to reveal the four (4)

servicing locations. These locations will either be a small holes in the metal seal or small raised

rings in the non-metal seal.

NOTE

Purge the needle prior to each use and lubricate the external surface of the

needle with grease to prevent seal damage.

B. Using a 6 cubic centimeter (cc) medical syringe and an 18 gauge hypodermic needle,

inject 0.5 cc of grease into the bearing. Inject the grease into one of the holes in the seal. If the

hypodermic needle does not fully enter the seal and bearing, remove the needle and rotate the

blower assembly slightly to clear the bearing cage and reinsert the needle and inject the grease

into the bearing.

C. Wipe excess grease from the exterior of the bearing and repeat the procedure on the

other blower assembly bearing.

4-39.4. Tail Rotor Feathering Bearing

4-39.5. Lubrication - Tail Rotor Feathering Bearing

A. Disconnect the pitch change links from the tail rotor assembly (para. 12-121, A).

B. Lubricate the tail rotor blade and grip assemblies. Purge lubricate the blade and grip

assembly at the normal 50 hour or 25 hour service interval, as applicable.

C. Rotate (one complete rotation on the feathering axis) the tail rotor blade grip

assemblies eleven times.

D. Lubricate the tail rotor blade and grip assemblies again.

E. Reconnect the pitch change links to the tail rotor assembly (para. 12-126, C).

Rev. 26

MM-4-38

Feb 28/2020

Table 4-8. Recommended Overhaul Cycles

COMPONENT

ITEM

OVERHAUL CYCLE

TH-28

480

480B

524-080

Starter/Generator

1,200 Hrs.

1,200 Hrs

150SG117Q-3-1

Not Authorized

1,000 Hrs

150SG117Q-4-1

Not Authorized

1,000 Hrs

20306-2

Valve Assembly

Not Authorized

3 years to coincide

(Optional Pop-Out Floats)

with hydrotesting of

reservoir cylinder or

after valve activation

28-13525-9

Tail Rotor Transmission

1,000 Hrs

1,200 Hrs

1,000 Hrs

4130020

Main Rotor Transmission

1,200 Hrs

Not Authorized

(All dash numbers)

4130030-1

1,200 Hrs*

Not Authorized

4130060

Not Authorized

1,200 Hrs**

(All dash numbers)

4131001-101

Overrunning Clutch

2,400 Hrs

4131001-105

2,400 Hrs

4131001-131

2,400 Hrs

2A20B-17149-2

Cargo Hook (Optional)

∆

528-023-01

* These Main Rotor Transmissions can only be installed if the aircraft has been modified for

installation of main rotor transmissions equipped with the oil filtration/cooling system.

** Requires a 600 Hour Mandatory Inspection. This is a temporary restriction pending data

analysis from the component tear-down inspections. Refer to paragraph 3-2 and Table 3-2

for more information.

∆ Refer to the manufacturer’s maintenance publications (See Table 2-2).

Rev. 26

MM-4-40

Feb 28/2020

4-41. Periodic Inspections

4-42. General Information

A. Periodic Inspection Checklists are set forth in paragraphs 4-44 through 4-48. These

inspection checklists are intended to be used in conjunction with more detailed procedures

presented in other sections of this manual, optional equipment maintenance manual

supplements, or vendor manuals. Special inspections are set forth in paragraphs 4-49 through

4-59. These special inspections are required following such occurrences as a main rotor and/or

tail rotor blade strike, a hard landing, or a rotor overspeed.

(1) The time extension for the periodic inspections is as follows:

100, 200, and 300 hour periodic inspections - 10 hours.

(2) If the extension is used, the next scheduled inspection is due at the time

applicable prior to using the extension. For example, if a 100 hour periodic

inspection is due at 100 hours, but is performed at 108 hours, the next periodic

100 hour inspection is due at 200 hours not 208 hours.

(3) If the periodic inspection is performed early, the next periodic inspection is due

based on when the inspection was performed. For example, if the periodic

inspection was performed at 98 hours instead of 100 hours, the next periodic

inspection is due at 198 hours, not 200 hours.

(4) The 10 hour extension does not apply to life limited components.

Mandatory component replacement times in flight hours are specified in paragraph 3-2.

C. Recommended component overhaul cycles are specified in paragraph 4-40.

4-43. Daily Inspection

The Enstrom TH-28, 480, or 480B do not require a mandatory daily (maintenance)

inspection. Owner/Operators opting to have maintenance personnel check the aircraft should

perform a preflight check I/A/W the TH-28, 480, or 480B Rotorcraft Flight Manual.

4-44. Periodic Inspection Checklists

A. These inspection checklists are intended for aircraft operating under normal

conditions. More frequent inspections may be required should adverse operations be

encountered.

B. For more detailed inspection procedures and tolerances, refer to the appropriate

section in the maintenance manual, optional equipment maintenance manual supplements, or

vendor manuals.

C. Perform a 100 hour inspection, as a minimum, to meet the requirements for an

Annual Inspection.

D. Refer to the Rolls-Royce 250-C20 Series Operation and Maintenance Manual for the

specific inspection requirements for continued airworthiness of the engine.

Rev. 26

MM-4-41

Feb 28/2020

100 HOUR/ANNUAL INSPECTION CHECKLIST

INITIAL EACH ITEM AFTER ACCOMPLISHMENT

INITIAL

5. LANDING GEAR ASSEMBLY

A. Inspect the landing gear and crosstubes for:

1) Damage or cracks

_______

2) Condition of the skid shoes

_______

3) Security of attachments

_______

4) Condition of the end caps

_______

5) Condition of the non-skid tape/paint

_______

6) Condition of the ground handling wheel mounts

_______

B. Inspect the landing gear oleos for:

1) Evidence of corrosion

_______

2) Evidence of leakage

_______

3) Proper extension

_______

4) Security of attachments

_______

5) Security of the steps

_______

6. DRIVE BELT SYSTEM

A. Inspect the upper pulley for:

1) Evidence of roughness or looseness of the aft bearing or discoloration of the

bearing housing

_______

2) Condition and security of the taper pin and flex pack

_______

3) Proper torque on the transmission pinion nut (250 ft-lbs)

_______

4) Condition of the pulley

_______

5) Security and condition of the bearing support truss and attaching hardware

_______

6) Condition of the pylon

_______

B. Inspect the drive belt for:

1) Cracked or missing sections

_______

2) Proper tension (2,500 - 1,750 pounds)

_______

C. Inspect the lower pulley for:

1) Evidence of roughness or looseness of the bearings or discoloration of the

_______

bearing housings

2) Evidence of bearing seal leakage

_______

3) Condition of the pulley

_______

4) Condition and security of the "H" strut

_______

5) Condition and security of the flex packs

_______

6) Condition and security of attaching hardware

_______

Rev. 23

MM-4-45

Jul 3/15

100 HOUR/ANNUAL INSPECTION CHECKLIST

INITIAL EACH ITEM AFTER ACCOMPLISHMENT

INITIAL

D. Perform the following tasks if the aircraft is equipped with oil lubricated lower

pulley bearing assemblies.

1) Drain the oil from the lower pulley bearing

_______

2) Inspect the sight plugs for cleanliness and staining. Remove and clean or

replace the sight plugs as required.

_______

3) Service the lower pulley bearing assemblies

_______

E. Inspect the overrunning clutch for evidence of oil leakage

_______

F. Drain the overrunning clutch and vented oil clutch reservoir (if equipped), inspect

the drained oil for metal flakes, and service.

G. Inspect the vented clutch oil reservoir (if equipped) for evidence of oil leakage

_______

H. Service the ORC or the vented clutch oil reservoir (if equipped)

_______

7. OIL COOLING SYSTEM

A. Inspect the oil cooler for:

1) Security of installation

_______

2) Evidence of oil leakage or cracks

_______

B. Inspect the scavenge/external oil filter assembly, oil lines, and fittings for

condition and security of installation

_______

C. Inspect the oil cooler, blower, inlet, and exhaust ducting for condition and

security

_______

D. Inspect the blower shaft bearings for security of installation, excessive wear, and

discoloration of the bearing mounts

_______

E. Remove and inspect the flex packs for cracks (ref. para. 13-75 and 13-77)

_______

F. Condition and security of the taper and roll pins and the flex packs

_______

AIR INTAKE SYSTEM

A. Inspect the upper plenum/ air inlet for cleanliness, condition, and security, and

_______

inspect for clearance between the drive belt and the upper plenum (ref para. 13-

31).

B. Inspect the transfer ducts for cracks, cleanliness, and condition/bonding of duct

boots.

_______

C. Inspect the lower plenum for cleanliness, condition, security, and bonding of inlet

seal and inspect the protective shield for condition and security (ref. para. 13-39)

_______

D. Inspect air particle separator perimeter for gasket condition, security, and seal.

_______

TAIL CONE ASSEMBLY

A. Inspect the tail cone for:

1) Cracks in the tail cone mount fittings

_______

2) Proper security to the pylon

_______

Rev. 26

MM-4-46

Feb 28/2020

100 HOUR/ANNUAL INSPECTION CHECKLIST

INITIAL EACH ITEM AFTER ACCOMPLISHMENT

INITIAL

3) Cracked or damaged bulkheads or doublers

_______

4) Legibility of decals and markings

_______

B. Inspect the tail rotor drive shaft for:

1) Rough or worn bearings

_______

2) Position of the rubber inserts

_______

3) Condition and security of the taper pins and flex packs

_______

4) Security of the pillow blocks

_______

C. Inspect the horizontal and vertical stabilizers for:

1) Damage or cracks

_______

2) Loose rivets

_______

3) Security of attachment

_______

D. Inspect the tail rotor guard for:

1) Damage and loose rivets

_______

2) Security of attachment

_______

E. Inspect the stinger tube for:

1) Evidence of loose rivets at the aft bulkhead

_______

2) Security of mounting

_______

F. Inspect the vibration absorber assembly for condition and security (if installed).

_______

10. TAIL ROTOR TRANSMISSION

A. Inspect the tail rotor transmission for:

1) Evidence of leakage at the seals

_______

2) Condition and security of the mounting screws

_______

3) Evidence of a cracked or damaged housing

_______

4) Condition and security of the plugs and sight gauge

_______

B. Drain the transmission and inspect the chip detector for the presence of

magnetic particles

_______

C. Service the transmission

_______

D. Inspect the tail rotor pitch controls for:

1) Worn bushings at the pivot points

_______

2) Slider assembly for freedom of operation and wear

_______

3) Condition and security of the control hardware

_______

Rev. 26

MM-4-47

Feb 28/2020

100 HOUR/ANNUAL INSPECTION CHECKLIST

INITIAL EACH ITEM AFTER ACCOMPLISHMENT

INITIAL

11. TAIL ROTOR ASSEMBLY

A. Inspect the tail rotor assembly for:

1) Cracks, nicks, dents, scratches, and bends

_______

2) Evidence of bond separations, corrosion, and bond line corrosion

_______

3) Loose tip rivets

_______

4) Condition and security of the teeter bearings

_______

5) Condition and security of the pitch change bearing

_______

6) Inspect the pitch change links for condition, worn rod end bearings, proper

_______

hardware, and security of installation

7) Fretting of the blades and grips at the attachments

_______

12. MAIN ROTOR TRANSMISSION

A. Inspect the main rotor transmission for:

1) Evidence of leakage

_______

2) Cleanliness and corrosion

_______

3) Cleanliness of the sight glass

_______

4) Condition and security of the mounting bolts and plugs

_______

5) Condition of the main rotor mast

_______

6) Condition of the pylon assembly (transmission area)

_______

B. Drain the transmission and inspect the chip detector and (if applicable) the oil

filter for the presence of metal particles

_______

C. Replace the oil filter (if applicable)

_______

D. (If applicable) Condition and security of heat exchanger, filter housing, pressure

switch, oil lines, drain line, fittings, oil pump, and mounting brackets

_______

E. Service the transmission

_______

13. MAIN ROTOR ASSEMBLY

A. Inspect the main rotor blades for:

1) Cleanliness and evidence of corrosion

_______

2) Condition of the blade tape, if installed

_______

3) Nicks, dents, or scratches

_______

4) Evidence of bond line separation

_______

5) Condition and security of the trim tabs

_______

6) Evidence of loose rivets in the drag link attachment fittings

_______

7) Proper security of the blades

_______

Rev. 22

MM-4-48

Jun 25/14

100 HOUR/ANNUAL INSPECTION CHECKLIST

INITIAL EACH ITEM AFTER ACCOMPLISHMENT

INITIAL

Inspect the main rotor retention assemblies for:

1) Condition of the up and down stops

_______

2) Condition and security of the pitch horn and planipetal weight, if installed.

_______

Inspect the universal block assemblies for:

1) Condition of the lead/lag stops

_______

2) Proper security of the lower nuts

_______

3) Condition of flapping bearing oil seals (if applicable)

_______

Inspect the hydraulic main rotor dampers for:

1) Radial wear in the rod end bearing

_______

2) Evidence of leakage

_______

3) Condition (corrosion (see SDB T-058), corrosion protection (para. 9-30, S))

_______

and security of the rod end bearing

4) Proper security at the attachment points

_______

5) Proper security of all hardware

_______

Inspect the center hub section for:

1) Evidence of cracks

_______

2) Fretting at the upper and lower spline adapters

_______

3) Inspect the torque stripe indicators on the mast nut. If the indicators show

loss of torque on the mast nut or are not installed, check the torque on the

_______

mast nut

Inspect the pitch change bellcranks for:

1) Evidence of cracks in the mounting brackets

_______

2) Proper bearing operation and wear at the pivot points

_______

3) Condition and security of the pitch change link rod end bearings

_______

4) Proper security of all hardware

_______

Inspect the upper control push-pull rods for:

1) Evidence of loose rivets

_______

2) Evidence of damage

_______

Rev. 26

MM-4-49

Feb 28/2020

100 HOUR/ANNUAL INSPECTION CHECKLIST

INITIAL EACH ITEM AFTER ACCOMPLISHMENT

INITIAL

14. SWASHPLATE CONTROL SYSTEM

A. Inspect the swashplate assembly for:

1) Looseness of the universal points (Refer to paragraph 12-78, A)

_______

2) Looseness of the push rod dogleg bearings

_______

3) Roughness in the cyclic bearing

_______

4) Condition of the rod ends and the fitting on the push-pull rods at the cyclic

bearing housing

_______

5) Proper security of all hardware

_______

B. Inspect the collective guide tube assembly for:

_______

1) Radial wear of the DU bushings

_______

2) Roughness in the collective bearing

_______

3) Wear in the collective walking beam at the bushings in the straps at the

transmission attachment and at the bearings in the collective bearing

_______

housing

4) Proper security of all hardware

_______

15. CABIN SECTION

_______

A. Inspect the cabin exterior for:

1) Proper operation of the doors

_______

2) Cleanliness, cracks or crazing of the door and cabin plexiglass

_______

3) Obstructed or bent pitot tube

_______

B. Inspect the cabin interior for:

1) Cleanliness and evidence of corrosion

_______

2) Presence and legibility of decals and placards

_______

3) Condition and security of the seats

_______

4) Deterioration of the seat cushions

_______

5) Condition, operation, and security of attachment of the safety belts and

shoulder harnesses

_______

6) Date of the last inspection and security of the fire extinguisher

_______

C. Inspect the instrument console for:

1) Condition and security of all instruments

_______

2) Condition and security of the console shrouds

_______

3) Legibility of all decals and placards

_______

D. Inspect the keel structure for:

1) Cleanliness and corrosion

_______

Rev. 22

MM-4-50

Jun 25/14

4-46. 200 Hour Inspection - Periodic Inspection Checklist

AIRCRAFT REGISTRATION NUMBER:

SIGNATURE:

AIRCRAFT SERIAL NUMBER:

DATE:

HOURS:

Flight:

CYCLES (Start Counter):

200 HOUR INSPECTION CHECKLIST

INITIAL EACH ITEM AFTER ACCOMPLISHMENT

INITIAL

1. GENERAL INSPECTION

A. Perform a complete 100 Hour/Annual Inspection

_______

2. OIL COOLING SYSTEM

A. Inspect and replace the scavenge/external oil filter element

_______

3. MAIN ROTOR ASSEMBLY

A. Inspect the main rotor retention assemblies for:

1) Evidence of ratcheting or binding in the feathering bearings

_______

2) Proper spring-back of the Lamiflex bearings

_______

3) Evidence of Lamiflex bearing deterioration (see SDB T-054)

_______

4) Condition of the Lamiflex nylatron straps

_______

5) Remove the retention assembly dust cover and inspect the T-T strap

retention block and pin assembly for condition and security.

6) Evidence of O-ring leakage

_______

7) Security of the spindle retention nut

_______

8) Evidence of a sheared roll pin at the hinge pin

_______

9) Evidence of ratcheting or binding of the flapping bearings

_______

10) Proper preload setting of the retention assemblies in the flapping axis (Does

not apply to retention assemblies installed I/A/W paragraph 9-19,A

_______

11) Proper security of the hinge pin locking tang washer

_______

Rev. 26

MM-4-57

Feb 28/2020

4-48. Special Scheduled Inspection - Periodic Inspection Checklist

AIRCRAFT REGISTRATION NUMBER:

SIGNATURE:

AIRCRAFT SERIAL NUMBER:

DATE:

HOURS:

Flight:

CYCLES (Start Counter):

SPECIAL SCHEDULED INSPECTION CHECKLIST

INITIAL EACH ITEM AFTER ACCOMPLISHMENT

INITIAL

MAIN ROTOR TRANSMISSION

A. Retorque the aft pinion nut 20-25 hours after installation

_______

DRIVE BELT SYSTEM

A. Inspect the alignment of the Lower Pulley Drive System in accordance with

paragraph 11-17 every 12 months

_______

B. Inspect the individual elements of the flex packs, P/N ECD4024-1, for cracks

and general condition every 12 months

_______

C. Inspect the drive belt every 50 hours for the following:

1) Contact with the upper plenum/air inlet (para. 13-29, B)

_______

2) Protruding cord on both the forward and aft edges of the drive belt around

the circumference of the lower pulley

_______

3) Condition of the belt that has been edge-sealed I/A/W SDB T-046

_______

OIL COOLING SYSTEM

A. Perform bypass indicator functional test on the Purolator/Facet

scavenge/external oil filter assembly in accordance with paragraph 13-71.1

_______

every 600 hours

B. For aircraft operated in dusty environments, inspect the blower impeller for dirt

accumulation every 200 hours and clean as required

_______

NEOPRENE COMPONENTS

A. Inspect components comprised of neoprene materials when helicopter has been

in temperatures below -20° C (-4 °F). Visually examine components for breaks,

chips, cracks or other deteriorating indications and replace as needed.

Neoprene locations:

1) Vibration dampening pad in tailcone structure

_______

2) Gasket installed between fuel bladder skin and spacer in installation of fuel

cap assembly

_______

3) Rubber absorber between drag link and pylon mount location in drive

assembly

_______

4) Clamps attaching the tail rotor guard

_______

5) Isolator on the oil tank support

_______

Rev. 26

MM-4-61

Feb 28/2020

Enstrom TH-28/480 Series. Maintenance Manual (2020) - page 2