ENSTROM TH-480 Series, TH-480B, TH-480, TH-28, TH-28 Series Supplement Manual
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ENSTROM TH-28/480 SERIES MAINTENANCE MANUAL
SUPPLEMENT 1
ENSTROM 480/480B AIR CONDITIONING SYSTEM
P/N 4220176-( )
The Airworthiness Limitations Section is FAA approved and specifies
inspections and other maintenance required under 14 CFR §§ 43.16 and
91.403 of the Federal Aviation Regulations unless an alternative program
has been FAA approved.
This manual supplement supersedes all previous editions of the TH-28/480 Maintenance
Manual Supplement 1 originally dated November 26, 1996.
Copyright 2011, 2017 by
The Enstrom Helicopter Corporation
2209 22
Menominee, Michigan 49858-3515
http://enstromhelicopter.com/
Telephone: 906-863-1200
Fax: 906-863-6821
nd
Street
Rev. 8
i May 1/17
ENSTROM TH-28/480 SERIES MAINTENANCE MANUAL SUPPLEMENT 1
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Rev. 8
ii May 1/17
ENSTROM TH-28/480 SERIES MAINTENANCE MANUAL SUPPLEMENT 1
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RECOMMENDED CHANGE REPORT
This maintenance manual is prepared and distributed by The Enstrom Helicopter Corporation
and is intended for use by personnel responsible for maintaining Enstrom TH-28, 480, and 480B
helicopters. This manual is periodically revised. If, in the opinion of the user, any information has
been omitted or requires clarification, please direct your comments to Enstrom via this form
(duplicate) or other similar form. Send the recommended changes to:
The Enstrom Helicopter Corporation
2209 22
nd
Street
Menominee, MI 49858-3515
ATTN: Technical Publications
Manual Identification: Enstrom TH-28/480 Series Maintenance Manual Supplement 1
Manual Date: February 9, 2001
Revision Number and Date:
Aircraft Model:
Recommended Change:
Rev. 8
iii May 1/17
ENSTROM TH-28/480 SERIES MAINTENANCE MANUAL SUPPLEMENT 1
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Rev. 8
iv May 1/17
ENSTROM TH-28/480 SERIES MAINTENANCE MANUAL SUPPLEMENT 1
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TABLE OF CONTENTS
Paragraph Description Page
Cover Page ..................................................................................................... i
Recommended Change Report ...................................................................... iii
Table of Contents ........................................................................................... v
Effective Page List ......................................................................................... vii
Section 1 Introduction
1-1. Aircraft Effectivity ......................................................................................... 1-1
1-2. Supplemental Changes and Revisions ....................................................... 1-1
1-3. Service Document Publications ................................................................... 1-1
1-4. Application of Warnings, Cautions, and Notes ............................................ 1-2
Section 2 General Information
2-1. System Description ..................................................................................... 2-1
2-2. Safety Precautions ...................................................................................... 2-2
2-3. Equipment and Consumables ..................................................................... 2-3
2-4. Suggested Spares List ................................................................................ 2-4
Section 3 Airworthiness Limitations
3-1. Airworthiness Limitations ............................................................................. 3-1
Section 4 Lubrication, Servicing, Troubleshooting, and Periodic Inspections
4-1. Lubrication ................................................................................................... 4-1
4-2. Servicing ...................................................................................................... 4-1
4-3 Troubleshooting ........................................................................................... 4-3
4-4 Periodic Inspections .................................................................................... 4-5
4-5 Periodic Inspection Checklist ...................................................................... 4-5
Section 5 System Maintenance
5-1. Belt Replacement and Adjustment, Pulley Alignment ................................. 5-1
5-2. Refrigerant Fitting Installation ...................................................................... 5-5
5-3. Leak Check ................................................................................................. 5-6
Plumbing Schematic Diagrams
A-1. Two Evaporator System ............................................................................. A-1
A-2. Three Evaporator System .......................................................................... A-2
A-3. Two Evaporator, Litter Compatible System ................................................ A-3
Electrical Schematic Diagrams
B-1. Two Evaporator System ............................................................................. B-1
B-2. Three Evaporator System .......................................................................... B-2
B-3. Transient Suppression Circuitry ................................................................. B-3
B-4. Two Evaporator, Litter Compatible System ................................................ B-4
Rev. 8
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ENSTROM TH-28/480 SERIES MAINTENANCE MANUAL SUPPLEMENT 1
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Rev. 8
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EFFECTIVE PAGE LIST
Page Date Page Date
i May 1/17
ii May 1/17
iii May 1/17
iv May 1/17
v May 1/17
vi May 1/17
vii May 1/17
viii May 1/17
1-1 May 1/17
1-2 May 1/17
2-1 Dec 3/10
2-2 Dec 3/10
2-3 May 1/17
2-4 May 1/17
2-5 May 1/17
2-6 May 1/17
2-7 May 1/17
2-8 May 1/17
2-9 May 1/17
2-10 May 1/17
3-1 May 1/17
3-2 May 1/17
4-1 Feb 20/08
4-2 Feb 20/08
4-3 Feb 9/01
4-4 Feb 9/01
4-5 May 1/17
4-6 May 1/17
5-1 May 1/17
5-2 May 1/17
5-3 May 1/17
5-4 May 1/17
5-5 Mar 17/09
5-6 Mar 17/09
A-1 Jun 14/11
A-2 Jun 14/11
A-3 Jun 14/11
A-4 Sep 12/08
B-1 Dec 3/10
B-2 Dec 3/10
B-3 Dec 3/10
B-4 Dec 3/10
Rev. 8
vii May 1/17
ENSTROM TH-28/480 SERIES MAINTENANCE MANUAL SUPPLEMENT 1
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Rev. 8
viii May 1/17
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SECTION 1
INTRODUCTION
1-1. Aircraft Effectivity
A. The data presented in this TH-28/480 Series Maintenance Manual Supplement is
applicable to all Enstrom 480 and 480B model helicopters equipped with the optional air
conditioning system, Part Numbers 4222176-1, 4220176-2, 4220176-3, 4220176-5, 4220176-6,
or 4220176-7.
1-2. Supplemental Changes and Revisions
A. Subsequent to the publication of the initial issue of this supplement, changes in the air
conditioning equipment, support concepts and procedures, as well as information developed by
experience may affect the contents of this supplement. To ensure that coverage in the
supplement 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 supplement will occur when the amount of changes
warrants complete reissue.
1-3. Service Document Publications
1. 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 or a segment of the aircraft fleet that are typically
safety/airworthiness related. The
will be incorporated in the
At the time of incorporation, the Service
maintenance manual supplement, and accomplishment or signDirective Bulletin in the maintenance records book is no longer required.
entry should be made in the maintenance records to indicate that the Service
Bulletin is superseded by the maintenance manual supplement.
2. Service Information Letters - Used to transmit information, recommendations, and
general
personnel applicable to the entire or a segment of the aircraft fleet. The
provided in the Service Information Letters will be incorporated into the
manual supplement as needed at a later date.
service instructions to the aircraft owner/operator and/or maintenance
information provided in the Service Directive Bulletins
maintenance manual supplement as needed at a later date.
Directive Bulletin is superseded by the
off of the Service
A detailed
Directive
information
maintenance
3. 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.
Rev. 8
1-1 May 1/17
ENSTROM TH-28/480 SERIES MAINTENANCE MANUAL SUPPLEMENT 1
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Service Information Letters and Service Directive Bulletins incorporated into the
maintenance
the Service Directive Bulletin Index
website: www.enstromhelicopter.com (follow
Publications section of the Technical Support page). Each index numerically lists all
Service Information Letters and Service Directive Bulletins,
those which have been incorporated into the maintenance manual supplement.
Service Information Letters and Service Directive Bulletins are also located under the
Tech
Publications section of the website.
Enstrom distributes maintenance manual supplement reissues and revisions in
hardcopy form via mail to
Notice of recently released Service
provided via a postcard mailing. Registration to receive publication mailings can be
coordinated through Enstrom Product
1-4. Application of Warnings, Cautions, and Notes
A. Throughout this supplement, it is necessary to highlight or emphasize important points
to avoid injury to personnel, damage to equipment, or unnecessary confusion while performing
maintenance procedures. The terms “WARNING”, “CAUTION”, and “NOTE” are used to draw
attention to instructions or information deserving special consideration.
manual supplement are logged in the Service Information Letter Index or
(as appropriate) located on the Enstrom Helicopter
the applicable link under the Tech
respectively, and identifies
All
owners and operators who are registered with Enstrom.
Information Letters and Service Directive Bulletins is
Support.
B.
C.
D.
WARNING
Calls attention to use of materials, processes, methods,
procedures, or limits that must be followed to avoid injury to
personnel.
CAUTION
Calls attention to methods and procedures that must be followed
to avoid damage to equipment.
NOTE
Calls attention to information essential to highlight for clarification
of procedures or to make a task easier.
Rev. 8
1-2 May 1/17
ENSTROM TH-28/480 SERIES MAINTENANCE MANUAL SUPPLEMENT 1
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SECTION 2
GENERAL INFORMATION
2-1. System Description
A. The air conditioning system, Part Number 4220176, is a vapor cycle type air
conditioner consisting of a compressor, condenser, receiver/drier bottle, by-pass valve, two
(4220176-1, -3, -5 or -7) or three (4220176-2 or -6) evaporator assemblies, plumbing, and
electrical control equipment. The refrigerant used in this system is HFC R134a. Refer to Figure
2-1 for the general arrangement of the air conditioning system.
NOTE
Part numbers 4220176-1, -2, or -3 are applicable to aircraft with a
110 amp system (S/N 5133 and earlier). Part numbers 4220176-5,
-6, or -7 are applicable to aircraft with a 150 amp system (S/N
5134 and subsequent).
B. The compressor, located on the left side of the lower pulley assembly, is a five cylinder,
reed valve, wobble plate type air conditioner compressor. It is belt driven off the lower pulley
assembly and is engaged electrically by a magnetic clutch. It is lubricated with oil carried by the
refrigerant.
C. The condenser, located in the tail cone aft of the baggage box, is a tube-fin design with
an axial flow cooling fan mounted directly above the condenser. The cooling fan draws fresh air
supplied by two air scoops mounted on opposite sides of the tailcone. The condenser air exit is
located at the bottom of the tailcone.
D. The receiver/drier bottle, located in the left side of the tailcone next to the condenser, is
the system reservoir. The receiver/drier bottle contains a desiccant filter (silica gel) which serves
to absorb moisture from the system.
E. The by-pass valve, located in the right side of the tailcone next to the condenser, is
used to prevent evaporator heat exchanger freeze-up by controlling the minimum evaporator
pressure (temperature). A thermally controlled switch, located in the left side forward evaporator
assembly, controls the by-pass valve.
F. Two evaporator assemblies (4220176-1, -2, -5 and -6) are located in the nose of the
helicopter. The evaporator assemblies are equipped with a centrifugal blower and a tube-fin
heat exchanger. Cooled air is discharged via four adjustable vents, two located on each side of
the instrument console. An optional third evaporator assembly (4220176-2 or -6) can be
mounted behind the pilot's seat to provide additional cooling for occupants of the aft bench seat
in the 480/480B. Cooling air from the third evaporator is ducted to vents located above the
bench seat occupants. An optional single evaporator assembly (4220176-3 or -7) with a
modified mount assembly allows compatibility of a litter installation in the nose of the helicopter.
The litter compatible air conditioning option also consists of a second evaporator assembly
(4220176-3 or -7) mounted behind the pilot’s seat to provide additional cooling.
Rev. 5
2-1 Dec 3/10
ENSTROM TH-28/480 SERIES MAINTENANCE MANUAL SUPPLEMENT 1
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G. The plumbing used in this air conditioning system consists of aluminum hard lines,
medium pressure rubber flex lines, "B" nut pressure fittings, unions, and tees. Servicing ports
are located on the left side of the aircraft above the aft crosstube. Plumbing schematic diagrams
(A-1, A-2, and A-3) are located in the back of this supplement.
H. The air conditioner system is controlled by switches located in the center pedestal. The
pilot can turn the system on, off, or select the evaporator blowers only. The pilot can also select
high or low blower speeds. If the optional third evaporator assembly is installed, a separate
switch for controlling blower speed is installed. Actual location of the air conditioning system
switches in the 480B may change because of customer specified avionics installations.
The electrical system has a binary HI/LOW pressure switch, located on the receiver/drier bottle,
wired in series with the compressor clutch. This switch is intended to protect the compressor in
case of system over-pressure or loss of refrigerant. The switch operating pressures are:
Low pressure function - opens at 30 psi (207 kPa)
closes at 50 psi (345 kPa)
Hi pressure function - opens at 335 psi (2310 kPa)
closes at 280 psi (1931 kPa)
Electrical schematic diagrams (B-1, B-2, B-3, and B-4) are located in the back of this
supplement.
2-2. Safety Precautions
A. The refrigerant used in the air conditioning system is HFC R134a. This refrigerant is
non-explosive, non-flammable, non-corrosive, has practically no odor, and is heavier than air.
Although R134a is classified as a safe refrigerant, certain precautions must be observed to
protect parts involved and the person working on the unit.
B. Liquid R134a at normal atmospheric pressure and temperature evaporates so quickly
that it tends to freeze anything that it contacts. Care must be taken to prevent any liquid
refrigerant from coming in contact with the skin, especially the eyes. R134a is readily absorbed
by most types of oil. Therefore, it is recommended a bottle of clean mineral oil and weak
solution of boric acid be kept nearby when servicing the refrigerant system.
WARNING
This air conditioning system should only be serviced by
qualified personnel.
WARNING
Always wear safety goggles when servicing any part of the
refrigeration system. Should any liquid refrigerant get into
the eyes, use a few drops of mineral oil to wash them out,
then use a weak solution of boric acid to wash the eyes, and
seek aid from a doctor immediately even though the irritation
has ceased.
Rev. 5
2-2 Dec 3/10
ENSTROM TH-28/480 SERIES MAINTENANCE MANUAL SUPPLEMENT 1
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C. It is important to keep the system tightly sealed because the refrigerant system is
always under pressure. Heat applied to any part of the refrigerant system would cause the
pressure to build up excessively.
WARNING
To avoid explosion, never weld, use a flame-type leak
detector, blow torch, solder, steam clean, bake an aircraft
finish, or use excess amounts of heat on or in the immediate
area of any part of the air conditioning system or refrigerant
supply tank while they are closed to the atmosphere.
2-3. Equipment and Consumables
A. The proper equipment for maintaining and servicing the air conditioning system is
required to keep the air conditioning system operating at peak efficiency. The following listed
equipment is recommended for servicing the air conditioning system:
1) Recovery/Recycling/Recharging Station
Suggested Model: Robinair Model 34700 or equivalent
Montpelier, Ohio 43543
(800) 822-5561
2) HFC R134a Refrigerant Electronic Leak Detector
Suggested Model: Signstek Portable AC Refrigerant Halogen Gas Leakage
Detector Tester with High Sensitivity
or equivalent
B. The following consumable items are required for properly maintaining and servicing the
air conditioning system:
1) Refrigerant: DuPont HFC R-134a
CAUTION
Do not use PAG (polyalkylene glycol) lubrication oil in this air
conditioning system. Only use polyester based lubrication oil.
NOTE
All polyester based lubricating oils may not be compatible with
each other when mixed. Follow the oil manufacturer's instructions
concerning mixing of oils.
Rev. 8
2-3 May 1/17
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