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

(7) Altimeter:

Test the altimeter following the instructions for performing a pitot/static system

leak check (paragraph 7-68).

7-13. Repair - Instrument Maintenance

A. Replace any required decals which are missing or not clearly legible.

B. Replace any instrument if the cover glass is loose, cracked, broken, or when the

instrument is found to be unserviceable.

7-14. Installation - Instrument Maintenance

A. Position the instrument into the panel. Install the mounting screws or tighten the

screw of the mounting clamp.

B. Remove the protective caps or covers as necessary, and connect the electrical

connectors and/or hoses to the instrument.

C. Check the instrument for operation.

NOTE

See Figure 7-1 for instrument location in the instrument panels. Optional

equipment instruments are not shown.

7-15. Rotor and Power Turbine Tachometer (Dual Tach)

7-16. General Description - Dual Tach

The rotor and power turbine tachometer (Dual Tach) is powered by the aircraft 28-volt

electrical system and driven by a tachometer generator for the power turbine section and a

magnetic pick-up mounted in the main rotor transmission for the rotor section. Refer to

paragraphs 7-10 through 7-14 for maintenance procedures.

7-17. Power Turbine Tachometer Generator

7-18. Description - Power Turbine Tachometer Generator

The power turbine tachometer generator is mounted on the N₂ tach pad on the left side of

the engine accessory drive gearbox and is connected to the dual tach. Refer to paragraphs 13-

129 through 13-132 for maintenance procedures.

MM-7-15

Feb 9/01

7-19. Rotor RPM Magnetic Pick-up

7-20. Description - Rotor RPM Magnetic Pick-up

The rotor rpm magnetic pick-up, located in the forward portion of the main rotor

transmission, is used to generate pulses used to drive the rotor rpm portion of the dual tach.

7-21. Removal - Rotor RPM Magnetic Pick-up

A. Drain the oil from the main rotor transmission (para. 4-13).

B. Remove the upper plenum/air inlet assembly (para. 13-28).

C. Disconnect the magnetic pick-up electrical connector.

D. Remove the magnetic pick-up from the main rotor transmission. If replacing the

magnetic pick-up, remove any shims installed on the pick-up.

7-22. Inspection - Rotor RPM Magnetic Pick-up

A. Inspect the magnetic pick-up for security of installation and condition and security of

the electrical wires and connectors.

B. Using a multi-meter, check for 270-330 ohms across the leads.

7-23. Repair - Rotor RPM Magnetic Pick-up

A. Repair damaged wiring or electrical connectors.

B. Replace the magnetic pick-up if the ohm check is outside the 270-330 ohm range or if

inspection of the system components and wiring isolates the problem to the magnetic pick-up.

7-24. Installation - Rotor RPM Magnetic Pick-up

A. Remove the inspection magnetic pick-up inspection plug located on the front of the

main rotor transmission.

B. Turn the gearbox until a gear tooth is directly under the center of the magnetic pick-

up installation hole.

C. Install the magnetic pick-up into the main rotor transmission.

(1) Insert a 0.030 feeler gauge through the access plug hole.

(2) Install any shims, P/N 28-16524-( ), from the old pick-up onto the replacement

magnetic pick-up between the check nut and the top base of the magnetic pick-

up.

(3) Replace the O-ring on the magnetic pick-up.

(4) Screw the magnetic pick-up in until it touches the feeler gauge.

Rev. 26

MM-7-16

Feb 28/2020

(5) Adjust the amount of shims as required to set the final clearance between the

magnetic tip of the pick-up and the gear tooth to .030-.045 inch/.76-1.14 mm.

(6) Torque the magnetic pick-up to 60-65 in-lb/6.8-7.3 Nm.

D. Install the inspection plug.

(1) Replace the O-ring on the plug and reinstall the plug in the front of the

transmission.

(2) Torque the plug and lockwire (.032) the magnetic pick-up to the plug.

E. Reconnect the electrical connector

F. Service the main rotor transmission (para. 4-12).

G. Install the upper plenum/air inlet assembly (para. 13-31).

Figure 7-2. Magnetic Pick-up Installation

Rev. 26

MM-7-17

Feb 28/2020

7-25. Gas Producer Tachometer

7-26. General Description - Gas Producer Tachometer

The gas producer tachometer (N₁) provides an indication in percent rpm of the engine gas

producer (N₁) section by connection to a tachometer generator mounted on the engine

accessory gearbox. Two different type N₁ Tach systems are used in the TH-28/480. The

"passive" system uses an indicator that is powered by the signal from the tachometer generator.

The "active" system uses an indicator that is powered by the aircraft electrical system and uses

a micro processor to convert the signal from the tachometer generator. Refer to paragraphs 7-

10 through 7-14 for maintenance procedures.

7-27. Gas Producer Tachometer Generator

7-28. General Description - Gas Producer Tachometer Generator

The gas producer tachometer generator is mounted on the N₁ tach pad on the right side of

the engine accessory drive gearbox and is connected to the N₁ tach. Refer to paragraphs 13-

129 through 13-132 for maintenance procedures.

7-29. Engine Oil Temperature and Pressure Indicator

7-30. General Description - Engine Oil Temperature and Pressure Indicator

The engine oil temperature and pressure indicator is a dual indicator which uses a

temperature bulb located in the engine oil reservoir for engine oil temperature indications and a

pressure transducer connected to the engine oil pressure line on the engine. Refer to

paragraphs 7-10 through 7-14 for maintenance procedures.

7-31. Engine Oil Temperature Bulb

7-32. General Description - Engine Oil Temperature Bulb

The engine oil temperature bulb, installed on the engine oil reservoir is a resistance type

temperature bulb which monitors the engine oil temperature and transmits varying voltage

signals to the engine oil temperature and pressure indicator.

7-33. Removal - Engine Oil Temperature Bulb

A. Drain the engine oil reservoir (para. 4-8).

B. Remove the lockwire and disconnect the electrical connector.

Rev. 26

MM-7-18

Feb 28/2020

CAUTION

Use a backing wrench when removing the temperature bulb to prevent from

damaging the engine oil reservoir.

C. Remove the lockwire and remove the temperature bulb from the engine oil reservoir.

D. Remove the gasket from the temperature bulb.

7-34. Inspection - Engine Oil Temperature Bulb

A. Inspect the temperature bulb for cracks, leaks, security, and proper installation.

B. Inspect the electrical connector for damaged or bent pins and cracked inserts

7-35. Repair - Engine Oil Temperature Bulb

A. Repair damaged electrical connectors.

B. Replace the gasket.

C. Replace the temperature bulb if cracked or damaged.

7-36. Installation - Engine Oil Temperature Bulb

A. Lubricate the gasket and bulb threads with MIL-PRF-23699 and install the gasket

onto the temperature bulb.

CAUTION

Use a backing wrench when installing the temperature bulb to prevent from

damaging the engine oil reservoir.

B. Install the temperature bulb into the engine oil reservoir and lockwire using .032 wire.

C. Connect the electrical connector and lockwire with 0.020 lockwire.

D. Service the engine oil reservoir (para. 4-7).

7-37. Engine Oil Pressure Transducer

7-38. General Description - Engine Oil Pressure Transducer

The engine oil pressure transducer, located on the right side of the pylon assembly just aft

of the engine, monitors engine oil pressure and transmits voltage signals to the engine oil

temperature and pressure indicator.

Rev. 26

MM-7-19

Feb 28/2020

7-39. Removal - Engine Oil Pressure Transducer

A. Open the right side engine access panel.

B. Disconnect the electrical connector and the oil pressure line from the engine oil

pressure transducer. Cap, plug, and cover the open line, port, electrical connections.

C. Loosen the hardware securing the transducer in the mounting clamps and remove the

transducer.

7-40. Inspection - Engine Oil Pressure Transducer

A. Inspect the transducer for cracks, security, and the mounting clamps do not cover the

static ports in the middle area of the transducer.

B. Inspect the oil line for leaks and proper operation.

C. Inspect the electrical connector for damaged or bent pins and cracked inserts.

7-41. Repair - Engine Oil Pressure Transducer

A. Repair damaged electrical connectors.

B. Tighten loose oil line fittings.

C. Replace defective or damaged oil lines.

D. Replace the pressure transducer if cracked or damaged.

E. Reinstall a improperly mounted pressure transducer.

7-42. Installation - Engine Oil Pressure Transducer

A. Install the pressure transducer into the mounting clamps and position so the static

ports are not obstructed by the clamps. Tighten the securing hardware.

B. Remove the caps, plugs, and covers. Reconnect the oil pressure line and the

electrical connector.

7-43. Turbine Outlet Temperature (TOT) Indicator

7-44. General Description - Turbine Outlet Temperature (TOT) Indicator

The turbine outlet temperature (TOT) indicator indicates the turbine outlet temperature in

degrees Celsius (C). Two different type TOT indicator systems are used in the TH-28/480. The

"passive" indicator system operates on electrical potential from the engine thermocouple

harness via a thermocouple lead spool resistor. The "active" indicator system is powered by the

aircraft electrical system and converts the electrical potential from the engine thermocouple

MM-7-20

Feb 9/01

SECTION 8

STRUCTURES

TABLE OF CONTENTS

Paragraph

Description

Page

8-83.

Baggage Compartment

MM-8-74

8-84.

Description

MM-8-74

8-85.

Removal

MM-8-74

8-86.

Inspection

MM-8-74

8-87.

Repair

MM-8-74.1

8-88.

Installation

MM-8-74.1

8-89.

Tailcone

MM-8-74.1

8-90.

Description

MM-8-74.1

8-91.

Removal

MM-8-74.1

8-92.

Inspection

MM-8-74.2

8-93.

Repair

MM-8-74.2

8-94.

Replacement

MM-8-76

8-95.

Installation

MM-8-77

8-96.

Horizontal and Vertical Stabilizers

MM-8-78

8-97.

Removal

MM-8-78

8-98.

Disassembly

MM-8-78

8-99.

Inspection

MM-8-80

8-100.

Repair

MM-8-80

8-101.

Assembly

MM-8-80

8-102.

Installation

MM-8-80

8-103.

Horizontal Stabilizer Spar

MM-8-81

8-104.

Removal

MM-8-81

8-105.

Inspection

MM-8-81

8-106.

Repair

MM-8-81

8-107.

Installation

MM-8-82

8-108.

Extension Tube

MM-8-82

8-109.

Removal

MM-8-82

8-110.

Inspection

MM-8-83

8-111.

Repair

MM-8-83

8-112.

Installation

MM-8-83

8-113.

Tail Rotor Guard

MM-8-83

8-114.

Removal

MM-8-83

8-115.

Inspection

MM-8-85

8-116.

Repair

MM-8-85

8-117.

Installation

MM-8-85

8-118.

Vibration Absorber

MM-8-86

8-119.

Removal

MM-8-86

8-120.

Disassembly

MM-8-86

8-121.

Inspection

MM-8-86

8-122.

Repair

MM-8-86

8-123.

Assembly

MM-8-86

8-124.

Installation

MM-8-87

8-125.

Consumable Materials List

MM-8-91

Rev. 26

MM-8-3

Feb 28/2020

B. Touch up areas of the epoxy primer finish using MIL-PRF-23377 primer or equivalent.

C. Repair damage to the pylon assembly I/A/W AC 43.13-1B. Contact The Enstrom

Helicopter Corporation Customer Service for detailed damage and repair limitations.

8-13. Access Panels, Covers, and Cowlings

8-14. Removal - Access Panels, Covers, and Cowlings

Remove the following access panels, covers, and cowlings using the procedures listed for

each panel, cover, or cowling. Refer to Figure 8-1 for access panel locations.

Forward Landing Gear Leg Panel(s):

(1) Remove the screws securing the access panel(s) to the keel access panels and

remove the panel(s).

Keel Access Panel(s):

CAUTION

Support the keel access panel(s) during the removal process to prevent from

damaging the antenna leads before they are disconnected.

(1) Remove the forward landing gear leg panel(s).

(2) Remove the screws securing the panel(s) to the cabin and the outboard screws

securing the forward landing gear leg panel(s) to the keel access panel(s).

(3) Disconnect the ground wire from the antenna ground plane and disconnect the

antenna lead from the antenna.

(4) Remove the panel(s).

Engine Access Panel(s):

(1) Unlock the turn lock fasteners at the bottom edge of the access panel(s).

WARNING

The pneumatic springs have approximately 25 pounds/11.4 kg of

pressure. Use extreme caution when removing the pneumatic springs.

(2) If installed, disconnect and remove the pneumatic spring door opener.

Rev. 22

MM-8-7

Jun 25/14

(3) Remove the hinge pin securing the access panel hinge half to the hinge half

installed on the airframe and remove the panel(s).

Bottom Engine Access Panel:

(1) Disconnect the engine and the engine fire pan drain lines.

(2) Remove the screws securing the access panel to the left and right side

cowlings, the cabin shell, and the bottom edge of the left and right side engine

fire curtain.

(3) Slide the access panel to one side and pull the opposite edge of the panel from

under the side cowling and remove the panel.

Fuel Cell Cover(s):

NOTE

Procedures for removing the covers are the same for both sides except as

noted in the instructions.

(1) Defuel the aircraft (para. 4-5).

(2) Remove the upper plenum/air inlet (para. 13-28).

(3) Remove the air deflector from the top of the cabin.

(4) Remove the hardware securing the filler port to the fuel cell cover on the left side

fuel cell.

NOTE

TH-28 S/N 3007 and subsequent and 480 S/N 5011 and subsequent have a

fuel quantity probe cover and gasket installed on the right fuel cell cover.

(5) Remove the hardware securing the cell to the cover (Aerazur fuel bladder

system), the fuel quantity probe cover, and the fuel cell cover to the cell

structure.

CAUTION

All or a portion of the fuel cell covers and possibly the filler port assembly are

sealed with sealant to prevent fuel leaks. A putty knife or other suitable tool

may be required to separate the cover from the cell structure and the filler

port. Use extreme caution to prevent from damaging the cover, fuel cell, fuel

cell structure, or injuring yourself while removing the cell cover.

(6) Remove the fuel cell cover.

Rev. 26

MM-8-8

Feb 28/2020

8-17. Installation - Access Panels, Covers, and Cowlings

Install the following access panels, covers, and cowlings using the procedures listed for

each panel, cover, or cowling.

Forward Landing Gear Leg Panel(s):

(1) Install by reversing the removal instructions.

Keel Access Panel(s):

CAUTION

Support the keel access panel(s) during the installation process to prevent

from damaging the antenna leads before the panels are installed.

(1) Install by reversing the removal instructions.

Engine Access Panel(s):

(1) Install by reversing the removal instructions.

Bottom Access Panel:

(1) Install by reversing the removal instructions.

Fuel Cell Cover(s):

NOTE

Procedures for installing the covers are the same for both sides except as

noted in the instructions.

CAUTION

Use extreme caution to prevent from damaging the cover, fuel cell, fuel cell

structure, or injuring yourself while removing the old sealant.

(1) Remove the old sealant from the fuel cell covers, the fuel cell support structures,

and possibly the fuel filler port if the left side cover is removed.

Rev. 26

MM-8-18.1

Feb 28/2020

NOTE

Do not install the sealant for the fuel cell covers until all troubleshooting,

adjusting, and/or repairs have been made to the fuel cells, the fuel quantity

system, or the low fuel warning system.

NOTE

Follow the mixing instructions on the sealant container or the sealant may not

properly cure.

(2) Using a sealant meeting AMS-S-8802 Type II Class B, apply a bead on all

interfacing fuel cell support structures - cowl ring, cabin structure, fuel shelf

structure. Ensure the sealant is on the inboard side of the hardware used to

secure the cell covers and apply more sealant in areas where needed to ensure

proper sealing (lower forward corner for example).

(3) Place the cover in position and install the hardware along the bottom edge of the

cover.

NOTE

Step (4) below only applies to TH-28s and 480s equipped with the Aerazur

fuel bladder system.

CAUTION

Do not over inflate the fuel cells to prevent from damaging the fuel cell

structure or the fuel cells.

(4) Install the hardware securing the fuel cells to the covers. Inflating the fuel cells

might be required to perform this task. To inflate the fuel cells, ensure the fuel

shutoff valve is "OFF", the sump drain and low point drain valves are closed, and

that the fuel filler port is installed or the port in the fuel cell is taped over. Using

filtered, dry, low pressure compressed air, inflate the fuel cells via the overboard

vent line. Remove the air source after installing the hardware.

NOTE

Early model TH-28/480s may have had sealant installed between the fuel cell

and the fuel cell cover at the filler port and may also have had sealant

between the filler port assembly and the fuel cell cover. If your aircraft has had

sealant installed in these areas, the sealant does not need to be installed

when reinstalling the cover provided the old sealant is removed and the filler

port area seals when reassembled.

Rev. 26

MM-8-18.2

Feb 28/2020

G. Install the door strikers onto the cabin shell.

8-43. Installation - Cabin Doors

A. If equipped, Position the door on the hinges and insert the jettison pins in the hinges

and in the restrain strap on the inside of the door. Ensure the jettison handle is correctly

positioned in the handle retainer. Lockwire the hinge jettison pins to the hinges using breakaway

lockwire (MS20995CY20 or equivalent).

B. Position the door on the hinges installed on the cabin shell and install the hinge pins

and secure.

C. Install the pin securing the restraint strap to the cabin and secure.

WARNING

The pneumatic springs have approximately 45 pounds/20.5 kg of

pressure. Use extreme caution when installing the pneumatic springs.

NOTE

Install the pneumatic springs with the piston rod oriented down to prevent the

seals from drying out and subsequent loss of gas pressure.

D. Install the pneumatic spring onto the fitting located on the cabin floor and install the

retaining clip. Install the upper end of the pneumatic spring onto the door fitting and install the

retaining clip.

E. Check the door assembly for proper fit and the latching system for proper operation.

If required, adjust the door hinges by shimming or the latching system by adjusting the strikers.

8-44. Windshields and Windows

8-45. Inspection - Windshields and Windows

A. Inspect the windshields and windows for cracks, crazing, pits, and scratches.

8-46. Repair - Windshields and Windows

A. Damage to the windshields and windows which does not interfere with pilot's line of

sight during normal flight and landing attitudes or damage that does not impair structural

integrity may be repaired by stop drilling or patching I/A/W AC 43.13-1B; however, the

windshield or window should be replaced at the earliest opportunity.

B. Damage to the decorative vinyl tape (P/N 70-0160-1056-6) which covers the paint

line may be repaired by removing the damaged portion and applying new tape. Use a cotton

glove and apply firm pressure while installing the tape. Do not stretch the tape when applying.

Rev. 21

MM-8-41

Apr 30/14

8-47. Replacement - Windshields and Windows

Replace the windshields as follows:

NOTE

Replacement procedures are the same for both windshields.

NOTE

All replacement windshields are now the "blown" version. Replace both

windshields if replacing a "flat" windshield with a "blown” windshield.

(1) Remove the cabin doors.

(2) If equipped, disconnect the defroster from the supply line and remove the

hardware securing it to the cabin shell.

(3) Remove the center strip from the windshields.

(4) Remove the hardware securing the windshield to the cabin shell.

CAUTION

Use extreme care while removing the windshield with a putty knife to prevent

from damaging the cabin shell or injuring yourself.

CAUTION

Use extreme care when using a portable heat gun to prevent from damaging

the paint finish due to excessive heat.

(5) Heat the edge of the windshield and adhesive using a portable heat gun and

separate the windshield from the cabin shell and center support with a putty

knife.

NOTE

Tape application for the windshield installation was discontinued for S/N 5238

and subsequent.

(6) Remove the residual foam tape or adhesive from the windshield recess in the

cabin shell and the center support. Clean the recess with acetone or equivalent.

(7) Place the replacement windshield into position and verify it will properly fit. Mark

areas of interference and trim the windshield using a belt sander. Ensure the

cabin door upper hinge post cutout in the replacement windshield is large

enough.

Rev. 26

MM-8-42

Feb 28/2020

(8) Drill the mounting holes in the replacement windshield using a pointed dull #11

drill bit if “-10" screws are used to secure the windshield or a pointed dull #15

drill bit if “-8" screws are used to secure the windshield by temporarily taping the

replacement windshield into place and back drilling the mounting holes through

the cabin shell and center support.

CAUTION

Use extreme caution while using an awl or other suitable device to prevent

from damaging the aircraft or injuring yourself.

NOTE

Mask off the area around the windshields on the outside of the aircraft and place

protective coverings inside the aircraft to prevent damage from excess adhesive.

(9) Prepare the adhesive (PR-1425-B2 or equivalent) following the manufacturer's

instructions and apply a coating approximately .0625 in/1.6 mm thick to the

center support.

(10) Prepare the adhesive (PR-1425-B2 or equivalent) following the manufacturer's

instructions and apply a coating approximately .0625 in/1.6 mm thick in the

cabin shell recess.

CAUTION

Do not over tighten the mounting screws for the windshields.

(11) Position the windshield in place. Temporarily install and tighten the mounting

hardware. Allow the adhesive to cure for 24 hours.

(12) Remove the mounting hardware and using a plastic scraper, remove the excess

adhesive.

(13) Apply a small bead of sealant (Phenoseal 102 or equivalent) on each side of the

windshield center strip and at the top and bottom and place into position. Apply

a small amount of sealant (Phenoseal 102) onto the shanks of the windshield

mounting hardware and install the mounting hardware. Do not over tighten the

mounting hardware.

(14) Paint the outer edges of the windshield(s).

(15) Install the defroster(s).

(16) Install the cabin doors.

Replace the overhead and cheek windows as follows:

NOTE

Overhead and cheek windows for late production 480 aircraft had putty-filled cleco

holes. Rivets are used in early (TH-28/480) and current production aircraft (480B).

Rev. 26

MM-8-43

Feb 28/2020

(1) Drill out the existing rivets.

CAUTION

Use extreme care while removing the windows with a putty knife to prevent

from damaging the cabin shell or injuring yourself.

CAUTION

Use extreme care when using a portable heat gun to prevent from damaging

the paint finish due to excessive heat.

(2)

Heat the edge of the window and adhesive using a portable heat gun and

separate the window from the cabin shell with a putty knife.

(3)

Remove the residual adhesive from the window recess while it is still warm.

(4)

Remove any remaining adhesive by sanding and wipe the recess area clean

with acetone or equivalent.

(5)

Place the replacement window on the cabin and tape into position.

(6)

Using a marker, mark the cabin hole locations.

(7)

Apply 1/4 (0.25) inch masking tape following the window recess in the cabin to

mark the window size for cutting.

(8)

Remove the window and cut to size using a fine tooth bandsaw and sand the

edges on a belt sander.

(9)

Check the fit of the window and re-sand the edges as necessary.

(10)

Using a pointed dull #17 (4.4 mm) drill bit, drill the replacement window at the

marked locations.

(11)

Sand the hole edge.

(12)

Remove the window and clean the recess in the cabin shell.

(13)

Lightly sand the bonding edges of the window and wipe clean with acetone or

equivalent.

NOTE

Mask off the area around the window on the outside of the aircraft and place

protective coverings inside the aircraft to prevent damage from excess

adhesive.

(14) Prepare the adhesive (PR-1425-B2 or equivalent) following the manufacturer's

instructions and apply a coating approximately .0625 in/1.6 mm thick in the

cabin shell recess.

Rev. 26

MM-8-44

Feb 28/2020

(15) Install the window into position and press firmly against the adhesive. Install the

mechanical fasteners (clecos). Allow the adhesive to cure for 24 hours.

(16) Remove the mechanical fasteners (clecos).

(17) Remove excess adhesive from around the window using a plexiglass scraper

made from the damaged window.

(18) Paint the outer edges of the window.

(19) Apply sealant (732-RTV or equivalent) to the washers and rivets upon

installation.

(20) Apply sealant (732-RTV or equivalent) between the window and the cabin shell.

Replace/Remove the chin windows as follows:

NOTE

TH-28, S/N 3007 and subsequent, and 480/480B, S/N 5039 and subsequent,

are equipped with removable chin windows. Refer to paragraph 8-47, B, for

aircraft not equipped with removable chin windows.

(1) Remove the screws securing the chin window.

CAUTION

Use extreme care while removing the windows with a putty knife to prevent

from damaging the cabin shell or injuring yourself.

(2) Using a putty knife, carefully break the seal around chin window and remove the

chin window.

(3) If required replace the foam tape (4516).

(4) If required, replace any damaged Rivnuts.

(5) Place the replacement window on the cabin and tape into position.

(6) Apply 0.25 inch/6 mm masking tape following the window recess in the cabin to

mark the window size for cutting.

(7) Remove the window and cut to size using a fine tooth bandsaw and sand the

edges on a belt sander.

(8) Check the fit of the window and re-sand the edges as necessary.

(9) Place the replacement window on the cabin and tape into position.

(10) Using a pointed dull #30 drill bit, carefully drill the mounting pilot holes in the

window using the Rivnuts as guides.

Rev. 26

MM-8-45

Feb 28/2020

(11) Remove the window from the cabin and open the pilot holes with a pointed dull

#15 drill bit.

CAUTION

Do not over tighten the mounting screws for the chin windows.

(12) Place the window on the cabin and install the mounting screws but do not

tighten. Apply sealant (Phenoseal 102 or equivalent) under the screw heads and

tighten the screws until the screw head contacts the window.

(13) Apply sealant around the seam between the chin window and the cabin.

Remove excess sealant from the seam and the screw heads as required.

(14) Paint the outer edges of the window.

Replace the opera windows as follows:

(1) Remove the pop-out vent window.

NOTE

Rivets and foam tape were used to secure the opera windows only in early

production TH-28/480 aircraft.

(2) Drill out the existing rivets.

CAUTION

Use extreme care while removing the windows with a putty knife to prevent

from damaging the cabin shell or injuring yourself.

(3) Separate the window from the cabin shell with a putty knife.

(4) Remove the residual tape or adhesive from the window recess and wipe the

recess area clean with acetone or equivalent.

(5) Place the replacement window into position and verify it will properly fit. Mark

areas of interference and trim the window using a belt sander.

(6) Using a pointed dull #41 drill bit, drill as many holes as required through the

window around the edges for mechanical fasteners (clecos) as required to

secure window while the adhesive cures.

(7) Remove the window and clean the recess in the cabin shell.

(8) Lightly sand the bonding edges of the window and wipe clean with acetone or

equivalent.

Rev. 26

MM-8-46

Feb 28/2020

NOTE

Mask off the area around the window on the outside of the aircraft and place

protective coverings inside the aircraft to prevent damage from excess

adhesive.

(9) Prepare the adhesive (PR-1425-B2 or equivalent) following the manufacturer's

instructions and apply a coating approximately .0625 in/1.6 mm thick in the

cabin shell recess.

(10) Install the window into position and press firmly against the adhesive. Install the

mechanical fasteners (clecos). Allow the adhesive to cure for 24 hours.

(11) Remove the mechanical fasteners (clecos) and fill the holes with glazing putty

(Bondo 801 or equivalent).

(12) Remove excess adhesive from around the window using a plexiglass scraper

made from the damaged window.

(13) Install the pop-out vent window.

(14) Paint the outer edges of the window.

Replace the cabin door window as follows:

(1) Remove the cabin door.

(2) Remove the upper hinge half from the door.

(3) Remove the pop-out vent window or the sliding vent window.

CAUTION

Use extreme care while removing the windows with a putty knife to prevent

from damaging the cabin shell or injuring yourself.

CAUTION

Use extreme care when using a portable heat gun to prevent from damaging

the paint finish due to excessive heat.

(4) Heat the edge of the window and adhesive using a portable heat gun and

separate the window from the cabin shell with a putty knife.

(5) Remove the residual adhesive from the window recess while it is stall warm.

(6) Remove any remaining adhesive by sanding and wipe the recess area clean

with acetone or equivalent.

Rev. 26

MM-8-47

Feb 28/2020

(7) Place the replacement window into position and verify it will properly fit. Mark

areas of interference and trim the window using a belt sander.

NOTE

Avoid drilling holes in the area of the upper hinge half and the forward edge of

the sliding vent window installation.

(8) Tape the window into position and drill approximately 20 to 25 holes using a

pointed dull #41 drill bit through the window around the edges for mechanical

fasteners (clecos).

(9) Remove the window and clean the recess in the cabin shell.

(10) Lightly sand the bonding edges of the window and wipe clean with acetone or

equivalent.

NOTE

Mask off the area around the window on the outside of the aircraft and place

protective coverings inside the aircraft to prevent damage from excess

adhesive.

(11) Prepare the adhesive (PR-1425-B2 or equivalent) following the manufacturer's

instructions and apply a coating approximately .0625 in/1.6 mm thick in the

cabin shell recess.

(12) Install the window into position and press firmly against the adhesive. Install the

mechanical fasteners (clecos). Allow the adhesive to cure for 24 hours.

(13) Remove the mechanical fasteners (clecos) and fill the holes with glazing putty

(Bondo 801 or equivalent).

(14) Remove excess adhesive from around the window using a plexiglass scraper

made from the damaged window.

(15) Paint the outer edges of the window.

(16) Back drill the holes for the upper hinge half using a pointed dull #11 drill bit and

Back drill the holes for the forward edge of the sliding vent window frame using a

pointed dull #28 drill bit.

(17) Install the pop-out vent window or the sliding vent window.

(18) Install the upper hinge half.

(19) Install the cabin door.

Replace the sliding vent window as follows:

Rev. 26

MM-8-48

Feb 28/2020

CAUTION

Protect the plexiglass window from damage.

(1) Remove the cabin door.

(2) Remove the handle from the sliding window and remove the window from the

track.

(3) Remove the hardware securing the window track to the door window and

remove the window track.

(4) Remove any residual tape from the cabin door window and the sliding vent track

if the track is going to be reused.

NOTE

If a replacement track is installed and the cabin window is drilled for the

installation, proceed to step (8). If the track is going to be reused and the

cabin door window is not drilled, proceed to step (9). If the track or the window

is not drilled for the installation, use as much of the damaged track and

damaged cabin door window as possible for a template and the hole pattern.

(5) Tape the replacement track onto the cabin door window and Back drill through

the window using a pointed dull #28 drill bit for the mounting holes.

(6) Tape the track into position and install the four screws in the forward edge of the

track. Drill the remaining holes in the window using a pointed dull #28 drill bit.

Turn the door over and carefully drill the four holes for the air deflector mounting

blocks.

CAUTION

Use extreme caution while using an awl or similar tool to prevent from

damaging the aircraft or injuring yourself.

(7) Remove the track from the window and apply double backing tape (3M brand #

4910-50) to the track. Perforate the tape at the rivet holes using an awl or other

suitable device.

CAUTION

Do not over tighten the hardware for the window track.

(8) Install the track into position and press firmly against the window. Install the

mounting hardware.

(9) Install the sliding window and the handle.

(10) Install the cabin door.

MM-8-49

Feb 9/01

8-48. Landing Gear Assembly (Figures 8-5 & 8-6)

8-49. Description - Landing Gear Assembly

The landing gear assembly consists of two cross tubes, four landing gear legs, four air/oil

oleos, two drag struts and two skid tubes. The cross tubes, which distribute the weight of the

aircraft to the landing gear assembly, are sleeved aluminum tubes with clamps and end caps

used to attach the gear legs and oleos. The aft cross tube is mounted to the bottom of the pylon

assembly and the forward cross tube is mounted in the keel assembly. The gear legs are

tubular steel and attach the skid tubes to the cross tubes. The oleos, connected between the

ends of the oleos and just above were the landing gear legs attach to the skid tubes, cushion

ground contact during landing. The oleos have a step attached to the lower portion to aid in

entering and exiting the cockpit and performing inspections or maintenance in the aft fuselage

area. The drag struts are tubular steel and used to give the gear stability and strength and to

prevent fore and aft movement during ground contact maneuvers. The skid tubes are aluminum

tubes which are used to distribute the weight of the aircraft onto the landing surface.

Replaceable hardened steel skid shoes are installed on the skid tubes to protect against skid

tube wear on hard surfaces. Attaching bolts or brackets for the ground handling wheels are also

installed in the skid tubes. (Refer to SIL T-066, latest revision, for additional ground handling

wheel bracket installation information.) All attachment points of the landing gear assembly

except the cross tubes to pylon/keel assemblies and the gear legs to the skid tubes are pivoting

attachments.

8-50. Removal - Landing Gear Assembly (Figures 8-5 & 8-6)

A. Remove the keel access panels.

B. Hoist up the aircraft (para. 4-68).

C. Remove the oleos (para. 8-65).

D. Remove the bolts securing the forward gear legs to the forward cross tube.

E. Remove the bolts securing the aft gear legs to the aft cross tube and remove the gear

legs and skid tubes.

F. Remove the bolts securing the aft cross tube to the pylon and remove the cross tube.

G. Remove the forward cross tube as follows:

(1) Remove the hardware from one of the end caps.

(2) Loosen the clamping hardware and remove the positioning hardware from both

gear leg attachment clamps.

(3) Remove the hardware securing the cross tube in the keel assembly.

(4) Slide the cross tube out the side of the aircraft opposite of the end cap with the

hardware removed. Remove the gear leg attachment clamps as they clear the

end of the cross tube.

Rev. 26

MM-8-50

Feb 28/2020

8-51. Disassembly - Landing Gear Assembly

NOTE

Disassembly of the landing gear is the same for both sides.

A. Remove the hardware and spacer attaching the universal blocks to the ends of the

gear legs.

B. Remove the hardware attaching the drag strut to the aft gear leg and remove the

strut.

C. Remove the hardware attaching the skid shoes and gear legs to the skid tube and

remove the gear legs.

D. Remove the hardware attaching the forward skid shoe to the skid tube and remove

the skid shoe.

E. Remove the attachment bolts or brackets, as applicable, for the ground handling

wheels.

NOTE

Disassembly of the cross tubes is the same except as noted.

F. Remove the hardware securing the end caps into the cross tubes and remove the

end caps.

G. Loosen the clamping hardware and remove the positioning hardware from the gear

leg and the pylon attachment clamps and remove the clamps from the aft cross tube.

8-52. Inspection - Landing Gear Assembly

A. Inspect the cross tubes for bends, bows, corrosion, and cracks. Inspect the pylon

attachment (aft cross tube) and the gear leg attachment clamps for corrosion, cracks, evidence

of elongated bolt holes, and security of the attaching hardware.

B. Inspect the landing gear legs and drag struts for any deformation, distortion, all

fittings and bolt holes for elongation, and all welds and gussets for cracks and corrosion.

C. Inspect the skid tubes for bends, bows, corrosion, cracks, dents, wear, and hardware

attachment holes for elongation. Inspect the ground handling wheel attachment lugs for damage

and security.

D. Inspect the skid shoes for wear (para. 8-62).

E. Inspect the oleos for damage, leakage, proper extension, and freedom of movement

(para. 8-67).

F. Inspect all skid tube bolts for corrosion, especially if the helicopter is operated with

the skids submerged, such as with floats.

Rev. 26

MM-8-54

Feb 28/2020

8-53. Repair - Landing Gear Assembly

A. Cross Tubes:

(1) Cross tubes with bows up to 0.5 inches/12.7mm are serviceable. Replace cross

tubes with bends, cracks, or elongated bolt holes.

(2) Replace end caps that are cracked or the bolt holes are elongated. Repair

pylon attachment (aft cross tube) or gear leg attachment clamps that are

cracked by welding I/A/W AC 43.13-1B. Replace pylon attachment (aft cross

tube) or gear leg attachment clamps that have elongated bolt holes.

B. Landing Gear Legs and Drag Struts:

(1) Landing gear legs and drag struts that are bent, bowed, or cracked may be

repaired I/A/W AC 43.13-1B. Contact The Enstrom Helicopter Corporation

Customer Service for detailed damage and repair limitations.

(2) Replace landing gear legs with elongated bolt holes. Replace drag struts that

have deformed, distorted, cracked, or elongated bolt holes (> 0.465 inch in any

direction) of the forward attachment plate.

C. Skid Tubes:

(1) Skid tubes that are bent, bowed, dented, or have holes in them are repairable

I/A/W AC 43.13-1B. Contact The Enstrom Helicopter Corporation Customer

Service for detailed damage and repair limitations.

(2) Replace skid tubes with elongated bolt holes.

8-54. Assembly - Landing Gear Assembly

NOTE

Assembly of the cross tubes is the same except as noted.

A. Install the gear leg clamps and the pylon attachment clamps onto the aft cross tube.

Ensure all of the clamps are oriented properly.

(1) Line the holes up between the P/N 4174013-903 clamp and the cross tube.

NOTE

Perform step 2 only if installing a new replacement aft cross tube and/or clamps.

(2) Ream the holes using a 5/16 Chicago-Latrobe type 405 Chucking Reamer.

(3) Lubricate the attachment bolts with a light coat of MIL-PRF-81322 grease.

NOTE

Eductor must be aligned IAW para. 13-14 before tightening the aft clamp bolts.

(4) Install and tighten the positioning and clamping bolts.

Rev. 26

MM-8-55

Feb 28/2020

B. Install the end caps into the aft cross tube and in one side of the forward cross tube.

Tighten the hardware.

NOTE

Assembly of the landing gear is the same for both sides.

C. Install the ground handling wheel attachment bolts or brackets, as applicable.

D. Install the forward skid shoe onto the skid tube.

E. Install the gear legs onto the skid tube. Install the two center bolts in the gear legs.

Install the skid shoes into place and install the remaining hardware and tighten.

F. Attach the drag strut to the aft gear leg. Torque the hardware to 40-60 in-lbs/4.5-6.8 Nm.

G. Install the universal blocks onto the ends of the gear legs. Do not torque at this time.

8-55. Installation - Landing Gear Assembly

A. Install the forward cross tube as follows:

NOTE

Perform step 1 only if installing a new replacement forward cross tube.

(1) Ream the holes for the installation of the cross tube to the keel and the clamps

to the cross tube using a 5/16 Chicago-Latrobe type 405 Chucking Reamer.

(2) Install the cross tube from the opposite side of the aircraft that the end cap is not

installed in. Install the gear leg attachment clamps as the cross tube is installed

into the keel assembly.

(3) Lubricate the attachment bolts with a light coat of MIL-PRF-81322 grease.

(4) Install the hardware securing the cross tube in the keel assembly and tighten.

(5) Install the positioning and clamping hardware into the gear leg attachment

clamps and tighten.

(6) Install the end cap and tighten the hardware.

B. Install the aft cross tube onto the pylon and tighten the hardware.

C. Place the landing gear into position and install the hardware attaching the aft gear leg

to the attachment clamp on the aft cross tube.

D. Install the hardware attaching the forward gear leg to the attachment clamp on the

forward cross tube. Torque the gear leg and universal block attachment hardware to 40-60 in-

lbs/4.5-6.8 Nm.

Rev. 26

MM-8-56

Feb 28/2020

B. Assemble the guide shaft assembly (5) as follows:

(1) Press the brass guide (4) into position if previously removed.

(2) Install the wiper (3) into the brass guide (4).

(3) Install the O-ring (6) on the O.D. of the guide shaft (threaded end).

CAUTION

The concave side of the back-up ring must face toward the O-ring.

(4) Install the back-up ring (7) and then the O-ring (8) into the groove in the I.D. of

the guide shaft (threaded end).

C. Lubricate both ends of the guide shaft assembly with hydraulic fluid (MIL-PRF-5606)

and install the guide shaft assembly onto the piston shaft (2).

CAUTION

The flanged end of the spacer faces towards the threads of the guide shaft

assembly.

D. Install the spacer (9) onto the piston shaft (2).

CAUTION

The notches in the rebound rings must be staggered.

E. Install the rebound rings (5 each) (10) on to the piston shaft (2).

F. Align the flow passage port on the inner edge of the piston assembly (12) to the flow

passage hole in the piston shaft (2) and install the piston assembly.

CAUTION

The ends of the dowel pin must be seated below the O.D. surface of the

piston to prevent possible binding on installation in the cylinder assembly.

G. Secure the piston assembly to the piston shaft with the dowel pin (11).

CAUTION

The notches in the rebound rings must be staggered.

H. Slide the guide shaft assembly (5) and the rebound rings (10) up against the piston

assembly (12).

Rev. 24

MM-8-67

Dec 4/15

CAUTION

Do not clamp the cylinder in the vise by the ears at the bottom of the cylinder.

Use tool T-0169-1.

Clamp the cylinder assembly (13) in a vise using tool T-0169-1 in an upright position.

Fill the cylinder to the base of the threads with hydraulic fluid (MIL-PRF-5606).

CAUTION

The notches in the rebound rings must be staggered.

NOTE

The piston must be inserted into the cylinder assembly slowly to allow the

hydraulic fluid to work through the staggered notches of the rebound rings and

the flow passage in the piston assembly.

J. Install the piston and guide shaft assembly. Insert piston and guide assembly into the

base of the cylinder assembly.

K. Hand tighten the guide shaft assembly to the cylinder assembly. Make an index mark

from the guide shaft assembly (5) to the cylinder assembly (13).

L. Torque the guide assembly using tool T-0169-1. Using the index mark from step K

above, torque the guide assembly to the cylinder assembly by turning the index mark on the

cylinder assembly approximately 1/4 in/6 mm past the index mark on the guide assembly.

M. Install and secure oleo valve (1) and torque to 170-180 in-lb/19.2-20.3 Nm. Safety

(0.032) the valve to the mount flange of the piston shaft. Loosen the air valve.

N. Attach one end of a clear plastic hose to the oleo valve and the other end in a

container of MIL-PRF-5606. Open the oleo valve. Slowly pump the strut in and out until the hose

is free of air bubbles when compressing the oleo assembly. Fully collapse the strut, tighten the

air valve, and remove the hose.

O. Torque the guide assembly using T-0169-1. Using the index mark, torque the guide

assembly to the cylinder assembly by turning the index mark on the cylinder assembly

approximately ¼ inch past the index mark on the guide assembly.

NOTE

The oleo may be pressurized before or after installation in the helicopter.

P. Connect the nitrogen pressure line to the oleo valve. Set the nitrogen pressure

regulator to 550 psig/3790 kPa for the aft oleos and 250 psig/1720 kPa for the forward oleos.

Remove oleo from the vise and remove tools T-0035 and T-0169-1.

WARNING

The piston shaft will extend when the oleo valve is opened.

Rev. 26

MM-8-68

Feb 28/2020

Q. Slowly open the oleo valve and allow the oleo to fill until the piston shaft is fully

extended and the oleo pressure has equalized to the regulator pressure. Close the oleo valve.

R Close the nitrogen tank valve, set the regulator pressure back to zero, and disconnect

the nitrogen pressure line from the oleo valve.

S. Install the valve cap.

T. Inspect the oleo for leaks.

8-70. Installation - Oleos (See Figure 8-7)

NOTE

If required, install the oleo condition placard (para. 8-70.2) prior to lowering the

aircraft.

Use the following procedures to install any of the oleos.

Refer to SIL T-028 to facilitate oleo fairing installation. If SIL T-028 has not

been complied with, install the fairings for the oleos while installing the oleos.

Install the top and bottom universal block to the oleo assembly.

NOTES

The P/N 4174027-11 bolt used to attach the universal to the oleo is a special

bolt with the head thickness and thread length decreased. Install the bolt so

that the nut will be facing outward when the oleo is installed on the aircraft.

Install the bolt attaching the forward oleos to the crosstube with the bolt head

facing aft.

Lubricate the attach bolt hardware with LPS 2, ACF 50, or MIL-PRF-81322

grease and install while wet.

(1) Place a light washer on each side of the universal link and install the link

between the mounting ears of the cross tube. Secure using a bolt, heavy

washers, and a nut.

(2) Install the oleo with the valve facing aft to the top cross tube.

(3) Connect a spring scale to the bottom hole in the bottom universal link and torque

the top attachment hardware until it requires 2 lb force to swing the oleo strut

assembly in and out and fore and aft.

Rev. 26

MM-8-69

Feb 28/2020

(4) Use a beam type in/lb torque wrench to record the torque on the nut that is

installed on the bolt facing aft.

(5) Place a light washer on each side of the universal link and connect the bottom

universal block to the landing gear leg.

(6) Remove the hardware connecting the top of the oleo to the cross tube. Set the

hardware aside in the same position and order for installation.

(7) Connect the spring scale to the top hole in the top universal link and torque the

attachment hardware at the bottom universal block connections with a required

2 lb drag as in step 3 above.

(8) Reinstall the top universal link to the cross tube. Ensure the hardware is

installed in the position and order as previously installed.

(9) Tighten the nut to the torque setting recorded in step 4.

B. Pressurize the oleos in accordance with para. 8-70, steps O through S if not

pressurized previously.

C. Lower the aircraft.

D. Check the oleos for proper extension and adjust as required.

Rev. 26

MM-8-70

Feb 28/2020

8-110. Inspection - Extension Tube

A. Inspect the extension tube for corrosion, cracks, dents, nicks, scratches, elongated

bolt holes, condition and security of the nutplates installed in the end of the tube, and security of

the installation.

B. Inspect the extension tube mounting clamp for condition, damage, and security.

8-111. Repair - Extension Tube

A. Corrosion, nicks, and scratches not exceeding 0.008 inch/.2 mm may be polished out.

Replace damaged nut plates. Replace the extension tube if cracked, damage exceeds 0.008

inch/.2 mm, or the tail rotor transmission screw holes are elongated.

B. Replace the mounting clamp if cracked or damage makes it unserviceable.

8-112. Installation - Extension Tube

A. Lightly coat the end of the extension tube with Lubriplate 630-AA (MIL-PRF-81322).

Note the orientation of the tube and install the tube into the tailcone.

B. Install and tighten the hardware securing the tube to its mount in the tailcone. Install

the aft tailcone/horizontal spar access panels.

NOTE

The top half of the extension tube clamp is not symmetric. If there is

interference between the clamp and the bulkhead, turn the clamp 180°.

C. Install the top half of the extension tube clamp. Ensure clearance with the bulkhead.

Install the clamping bolts and torque (50-70 in-lb/5.6-7.9 Nm). Check that the difference

between the gap on both sides of the clamp is within 0.010 inch/.25 mm, adjust as required.

D. Install and tighten the bolts securing the aft tail rotor drive shaft bearing pillow block.

Safety wire with .032 wire and install the aft tail rotor drive shaft cover.

E. Install the tail rotor transmission (para. 11-92). If removed from the tail rotor

transmission, install the tail rotor assembly (para. 9-51).

F. Install the tail rotor guard.

G. Check the tail rotor control cable tension and rigging (para. 12-99 and 12-100).

8-113. Tail Rotor Guard (Figure 8-11)

8-114. Removal - Tail Rotor Guard

A. Remove the hardware from the mounting clamp on the tailcone.

B. Remove the hardware securing the tail rotor guard to the extension tube clamp and

the tail rotor transmission.

C. Remove the tail rotor guard.

Rev. 26

MM-8-83

Feb 28/2020

8-115. Inspection - Tail Rotor Guard

A. Inspect the tail rotor guard for cracks and wear or damage associated with ground

contact.

B. Inspect the end fittings for loose or sheared rivets and elongated bolt holes.

C. Inspect the tail rotor guard tube and plug fitting joint for looseness.

D. Inspect the securing hardware for damage and the anti-chaffing pads for condition

and security.

8-116. Repair - Tail Rotor Guard

A. Replace tail rotor guard if cracked or extensively damaged from ground contact.

NOTE

If the tail rotor guard is worn due to ground contact but is not worn through the

guard, install a piece of tape over the area as a contact indicator.

B. Replace sheared or working rivets in the end fittings. Replace the end fittings if the

bolt holes are elongated.

C. Install washer (22) (Figure 8-11) between tail rotor guard tube and strut if plug fitting

joint is loose.

D. Replace damaged hardware and worn anti-chaffing pads.

8-117. Installation - Tail Rotor Guard

NOTE

Shimming may be required at the extension tube clamp or tail rotor transmission

locations.

A. Apply grease (MIL-PRF-81322) to the inside surface of the ears of the extension tube

clamp. Place the tail rotor guard into position and install the hardware attaching the guard to the

extension tube clamp.

B. Install the clamp half and hardware onto the fitting at the bottom of the tailcone.

C. Apply grease (MIL-PRF-81322) to the inside surface of the ears of the tail rotor

gearbox assembly. Install the tail rotor guard fitting into the tail rotor transmission and install the

attaching hardware. Tighten all of the attaching hardware.

Rev. 26

MM-8-85

Feb 28/2020

8-118. Vibration Absorber (Figure 8-12)

NOTE

The vibration absorber can only be installed on aircraft equipped with Tailcone

Assembly, P/N 4112000-103, or after modification of the tailcone in

accordance with Vibration Absorber Kit, P/N 4230018-1, 4230018-3, or

4230018-5.

8-119. Removal - Vibration Absorber

A. Disconnect the lanyard (10) from the tailcone tab.

B. Remove the hardware (3, 4) attaching the beam (1) to the tailcone and remove the

backing plate (2) and beam (1).

8-120. Disassembly - Vibration Absorber

NOTE

Removing/moving the weights from a Atuned@ vibration absorber will require

absorber tuning when the vibration absorber is reinstalled.

A. Remove the hardware (7, 4, 8, 9) attaching the lanyard (10) and weights (6) to the

beam and remove the weights (6).

8-121. Inspection - Vibration Absorber

A. Inspect the beam, weights, and support brackets for cracks, nicks, scratches,

corrosion and security of installation.

B. Inspect the mounting hardware for damage.

C. Inspect the lanyard for condition.

8-122. Repair - Vibration Absorber

A. Replace the beam if cracked or damage exceeds a depth of .020 inches/.51 mm.

Polish out damage to a maximum depth of .020 inches/.51 mm.

B. Replace cracked support brackets or brackets with damage exceeding .020 inch/.51

mm in depth. Polish out damage to a maximum depth of .020 inches/.51 mm.

C. Replace damaged hardware or the lanyard as required.

8-123. Assembly - Vibration Absorber

A. Install the weights (6) and lanyard (10) on the beam (1) and secure with the hardware

(7, 4, 8, 9). Position the weights 0.3 inches/7.6 mm from the end of the beam and torque the

bolts (7) to 75 in-lbs/8.5 Nm.

Rev. 26

MM-8-86

Feb 28/2020

8-125. Consumable Materials List

ITEM

DESCRIPTION

PART NUMBER

Acetone

Acetone Solvent

Adhesive

Trim Adhesive, 3M Brand

8031

Adhesive

Window/Windshield Adhesive,

PR-1425-B2

Courtaulds Aerospace

Compound

Anti-Corrosion, Conductive Compound,

CP8-TB

Kopr-Shield Brand

Compound

ACF-50 Anti-Corrosion/Lubricant, Lear

10013

Chemical Research

Fabric

Fire Curtain, Nextel Brand

Enstrom P/N 400-006

Grease

Grease, Lubriplate Brand

630-AA¹ (06701)

Grease

MIL-PRF-81322

Hydraulic Fluid

MIL-PRF-5606²

Lockwire

Lockwire Copper .020”

MS20995CY20

Lockwire

Lockwire.032”

MS20995C32

Lubricant

LPS 2 Heavy Duty Lubricant, LPS

00216

Laboratories

Nitrogen

Paint, Touch-Up

Flat Black, Spray Can

Primer

Epoxy Primer

MIL-PRF-23377³

Putty

Glazing and Spot Putty, Bondo

801

Sealant

Fuel Resistant Coating, 3M Brand

EC 776

Sealant

Fuel Resistant, AMS-S-8802 Type II Class B

Sealant

Silicone Sealant, Dow Corning Brand

732-RTV

Sealant

Vinyl Sealant

Phenoseal 102

Glouchester Co., Inc.

P.O. Box 428, Franklin, MA 02038

Sealant

Fire Barrier Sealant, 3M Brand

CP25WB+

Shielding Coating

EMI/RFI Shielding Coating, Acheson Brand

Electrodag 437

¹ MIL-PRF-81322 is an acceptable alternate.

² AeroShell Fluid 41 (Shell Oil), Royco 756 (Anderol), or Phillips X/C 5606H (Phillips 66)

³ Example: PRC-DeSoto Brand 513x390/activated by 910x624; or equivalent.

Rev. 26

MM-8-91

Feb 28/2020

ITEM

DESCRIPTION

PART NUMBER

Solder

“44” Resin Solder

String

Cotton String

Tape

Transparent, 3M Brand

5430

Tape

Tape, Masking 1“

Tape

Double Sided, Foam .50”, 3M Brand

4910-50

Tape

Double Sided, Foam 1”, 3M Brand

4016-1

Tape

Single Sided, Foam .75”, 3M Brand

4516-75

Tape

Vinyl, Black .25”, 3M Brand

70-0160-1056-6

Thread

Sewing Thread Metalized, 0.020”

Enstrom P/N 300-093

(MT13)

Thread Sealant

Thread Sealant, Loctite Brand

Threadlocker Blue 242⁴

Thread Sealant

Thread Sealant, Vibra-Tite Brand

VC-3

⁴ Acceptable alternate to VC-3.

Rev. 23

MM-8-92

Jul 3/15

SECTION 9

ROTOR SYSTEMS

TABLE OF CONTENTS

Paragraph

Description

Page

Table of Contents

MM-9-1

9-1.

Main Rotor System

MM-9-3

9-2.

Description

MM-9-3

9-3.

Troubleshooting

MM-9-3

9-4.

Autorotation RPM Adjustment

MM-9-5

9-5.

Tracking

MM-9-6

9-6.

Main Rotor Hub

MM-9-15

9-7.

Removal

MM-9-15

9-8.

Disassembly

MM-9-16

9-9.

Inspection

MM-9-19

9-10.

Repair

MM-9-19

9-11.

Assembly

MM-9-19

9-12.

Installation

MM-9-25

9-13.

Retention Assembly

MM-9-26

9-14.

Removal

MM-9-26

9-15.

Disassembly

MM-9-27

9-16.

Inspection

MM-9-33

9-17.

Repair

MM-9-33

9-18.

Assembly

MM-9-33

9-19.

Installation

MM-9-48

9-19.1

Tension-Torsion Straps

MM-9-51

9-19.2

Removal

MM-9-51

9-19.3

Installation

MM-9-51

9-20.

Universal Block

MM-9-52

9-21.

Disassembly

MM-9-52

9-22.

Inspection

MM-9-52

9-23.

Repair

MM-9-52

9-24.

Assembly

MM-9-52

9-25.

Dampers

MM-9-62

9-26.

Removal

MM-9-62

9-27.

Disassembly

MM-9-62

9-28.

Inspection

MM-9-66

9-29.

Repair

MM-9-66

9-30.

Assembly

MM-9-66

9-31.

Installation

MM-9-69

9-32.

Main Rotor Blades

MM-9-74

9-33.

Description

MM-9-74

9-34.

Removal

MM-9-74

9-35.

Inspection

MM-9-77

9-36.

Repair

MM-9-87

9-37.

Refinishing

MM-9-95

9-38.

Installation

MM-9-97

Rev. 26

MM-9-1

Feb 28/2020

SECTION 9

ROTOR SYSTEMS

TABLE OF CONTENTS

Paragraph

Description

Page

9-39.

Tail Rotor Assembly

MM-9-97

9-40.

Description

MM-9-97

9-41.

Troubleshooting

MM-9-97

9-42.

Static Balancing

MM-9-99

9-43.

Tracking and Dynamic Balancing

MM-9-103

9-44.

Removal

MM-9-107

9-45.

Disassembly

MM-9-109

9-46.

Cleaning

MM-9-110

9-47.

Inspection

MM-9-111

9-48.

Repair

MM-9-111

9-49.

Refinishing

MM-9-119

9-50.

Assembly

MM-9-121

9-51.

Installation

MM-9-123

9-52.

Consumable Materials List

MM-9-126

Rev. 26

MM-9-2

Feb 28/2020

Bolt

14.

Upper Hub Plate

Bolt

15.

Universal Block

Bracket

16.

Center Spacer

Dust Cover

17.

Lower Hub Plate

Retaining Nut

18.

Lower Spline Adapter

Lock Washer

19.

Grease Fitting

DU Washer

20.

Grease Fitting

Shim

21.

Stop Pad

Retaining Nut

22.

Bearing

10.

Lock Key

23.

DU Washer

11.

Bolt

24.

Spacer

12.

Upper Spline Adapter

25.

Shim

13.

Dowel Pin

26.

Grease Fitting

Figure 9-4. Main Rotor Hub Assembly with Grease Lubricated Flapping Bearings

MM-9-17

Feb 9/01

Bolt

19.

Grease Fitting

Bolt

20.

Stop Pad

Bracket

21.

Bearing

Dust Cover

21A.

Bearing

Retaining Nut

22.

DU Washer

Lock Washer

23.

Spacer

DU Washer

24.

Shim

25.

Seal

Retaining Nut

26.

Sleeve

10.

Lock Key

27.

O-Ring

11.

Bolt

28.

Plug

12.

Upper Spline Adapter

29.

Reservoir

13.

Dowel Pin

30.

Reservoir Cap

14.

Upper Hub Plate

31.

O-Ring

15.

Universal Block

32.

O-Ring

16.

Center Spacer

33.

Seal

17.

Lower Hub Plate

34.

Shim

18.

Lower Spline Adapter

Figure 9-5. Main Rotor Hub Assembly with Oil Lubricated Flapping Bearings

Rev. 26

MM-9-18

Feb 28/2020

M. Heat the upper hub plate to approximately 250°F/121°C and lift the hub plate from the

universal blocks (15). Tap with a plastic mallet if necessary.

N. Heat the lower hub plate to approximately 250°F/121°C and tap the universal blocks

from the hub plate.

(1) Remove center spacer (16) and shim (34), if installed.

O. Remove the grease fittings (19) from the hub plates.

9-9. Inspection - Main Rotor Hub

A. See Table 9-1 for detailed inspection of the main rotor hub assembly.

9-10. Repair - Main Rotor Hub

A. Repair or replace components of the main rotor hub as indicated in Table 9-1.

9-11. Assembly - Main Rotor Hub (Figure 9-4 or 9-5)

WARNING

Use extreme caution when removing or installing the blade and grip

assemblies to prevent from injuring personnel.

WARNING

Use protective gloves when handling heated parts.

NOTE

The upper hub plate has heli-coil inserts in the outer bosses for the walking

beam mount brackets. The lower hub plate bosses are solid.

A. Heat the upper hub plate (14) and the lower hub plate (17) to approximately

250°F/121°C.

B. Place the lower hub plate on 2" X 4" wood blocks. Lubricate the bearing bores with

MIL-PRF-81322.

NOTE

Ensure the DU washers have been installed on the U-blocks with the

chamfered side facing the hub plates. The DU washers must be seated in the

recessed area of the hub plate.

C. Install the U-block (universal block) assemblies (15) into the bearing bore of the hub

plate with the threaded notched end of the U-blocks down (3 places).

Rev. 26

MM-9-19

Feb 28/2020

Table 9-1. Main Rotor Hub Assembly

Inspection Requirements

P/N

Fig. 9-4, 9-5

Part Name

Inspection*

Serviceable Limits*

Repair Limits

Repair or Action

Item #

28-14202-1

Walking Beam

Deformed or cracked

None Allowed

Not Repairable

Replace Bracket

Bracket

ears

Security of the

No Play Allowed

Not Repairable

Replace Bracket

bushings in the bracket

Nicks, scratches, or

None Allowed

≤ .010 deep

Blend and polish out

corrosion

smooth

28-14227-1,

Nut

Threads

None Allowed

Not Repairable

Replace Nut

-11

Fig. 9-6, 6

(rolled or missing)

W-09

Lockwasher

Tangs

None Allowed

Not Repairable

Replace Lockwasher

(deformed or cracked)

28-14236-1

DU Washer

Flatness

.005

Not Repairable

Replace Washer

Thickness .090 to .093

-.003

Not Repairable

Replace Washer

28-14256-1

Nut

Threads

None Allowed

Not Repairable

Replace Nut

(rolled or missing)

28-14224-1, -3,

12 & 18

Spline Adapters

Inboard face of adapter

.0025 FIM

Not Repairable

Replace Adapter

-5

perpendicular to the

O.D.

O.D. 3.6235 to 3.6245

-.0005

Not Repairable

Replace Adapter

Spline pitting

.003 deep

Not Repairable

Replace Adapter

Spline corrosion

None Allowed

Surface corrosion

Remove with wire brush

Rev. 26

MM-9-20

Feb 28/2020

Enstrom TH-28/480 Series. Maintenance Manual (2020) - page 4