AirComm Corporation Airbus AS350 Air Conditioner Instructions for Continued Airworthiness User Manual

							AIR CONDITIONER SERVICE MANUAL AS350-200M-1 
Revision 6 Page 3 
11. Distribution 
This  document  is  to  be  placed  with  the  aircraft  maintenance  records  at  the  time  of 
system installation. 
 
Changes  will  be  made  to  this  document  in  response  to safety-of-flight  or non-safety-of-
flight  issues.  Any  changes  will  result  in  a  revision  to  this  document.  Revisions  shall  be 
noted in the Record of Revisions and on the List of Revisions of this manual. 
 
In  addition  to  the  revision  of  the  manual,  those  changes  categorized  as safety-of-flight 
shall  have  a  Service  Bulletin  issued  to  the  operator  providing  the  necessary  information 
to comply with or to correct the safety-of-flight issue. 
 
Replacement or revised copies of this manual can be obtained by contacting: 
 
Air Comm Corporation Service Department 
1575 124th Avenue 
Westminster, CO.80234 
Phone No. 303-440-4075 Fax No. 303-440-6355 
Email: [email protected] 
12. Changes to Instructions for Continued Airworthiness 
Changes made to a line or paragraph of this document will be indicated by a vertical bar 
in the right hand margin. A complete page change will be indicated by a vertical bar next 
to the page number. 
 
(Example: Any change will appear with a vertical bar next to that change). 
13. Air Conditioner Features 
The AS350 air conditioner features one forward mounted evaporator assembly (cockpit), 
one aft  mounted  evaporator  assembly (behind main  cabin),  one  condenser assembly, 
and  a  compressor  driven  by  the main  rotor  input shaft  just  aft  of  the  aft  main 
transmission, aircraft  left.  These components  and  associated  plumbing  combine  to 
provide conditioned air through the existing air distribution system when the engines are 
operating during both ground and flight operations. 
 
This  system  can  be  operated  in either  the Air Condition  (A/C),  or Fan mode.  In  the  A/C 
mode,  conditioned  air  is  provided  by  the  forward  and  aft  evaporator assemblies to  the 
cockpit  and  main  cabin  areas  respectively. In Fan mode,  the evaporator  blowers  are 
used  to  circulate cabin  air,  while  the  compressor  clutch  remains  disengaged. When 
using  the  cabin  heater  it  is  acceptable  to  operate  the  air  conditioner  if  desired,  to  defog 
the cabin windows. 
 
The air conditioning system is connected electrically to the aircraft’s DC Power Panel 28 
VDC  Bus.  The  control  panel  for  the  air  conditioner  system  is  located  on  the cockpit 
overhead panel or instrument panel. The control panel consists of an A/C & Fan switch, 
two  switches  for  the  control  of  cockpit  and  cabin  evaporator  blower  speeds,  a 
temperature control rheostat knob and a panel light dimmer rheostat knob. Temperature 
control is achieved by means of a refrigerant bypass valve, thus eliminating compressor 
cycling. The fan motors feature dual fan speed. This feature can be used in both the A/C 
or fan modes. 
  
						

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A  “COMP  ON” green  or  blue annunciator,  located  on  the  instrument  panel,  provides  a 
visual  status  of  compressor  operation.  For  aircraft  equipped  with  a VIVISUN  lighted 
pushbutton switch, compressor engagement is displayed on the switch as a blue COMP 
ON annunciation. 
 
 
 
Figure 1-1 – Air Conditioning System Control Panel 
 
The compressor is mounted on the surface of the main gearbox coupling case, in the aft 
aircraft  center  portion of  the transmission  compartment.  It is  driven  by  a flat  or Poly  V-
Belt  and  a  pulley  which  is  mounted to  the main  rotor  input shaft.  Access  to  the 
compressor is provided by the transmission compartment access doors. 
 
The  condenser  assembly for  the -200  & -202  systems is  mounted  in the upper  RH 
baggage compartment and features  a  blower  assembly  and  a  separate  heat  exchanger 
to  reject  system  heat overboard. Airflow  through  the  condenser  heat  exchanger  is 
provided  by a 28  volt  DC  high  performance  blower. For the  optional -204  system,  the 
condenser is mounted in the forward tail boom and features dual blowers. 
 
The forward evaporator is mounted on the right side of the lower console forward of the 
anti-torque  pedals.  Conditioned  air  is  delivered  to  the  crew  by means  of  air  ducts, 
mounted to the sides of the instrument panel console. 
 
The  aft  evaporator  assembly  is  mounted on the transmission  deck,  RH  side and  is 
enclosed  by  the  transmission  cowling.  Cabin  return  air  is  ducted  to  the  evaporator 
through  a  cutout in  the aft  cabin  bulkhead.  Conditioned  air  is  pumped  to  the  existing 
headliner ducting in the cabin top. 
 
The  aft  evaporator assembly is  equipped  with  a  freeze  switch. The freeze switch  probe 
is located in the core of the evaporator heat exchanger. This switch prevents coil freeze-
up by limiting the minimum coil temperature to 32º F (0º C). 
 
The  system  is  also  equipped  with  a binary pressure switch.  This  switch  is  designed  to 
protect  the  system  against  over-pressure  situations,  or  under-pressure  in  the  event  of 
refrigerant  loss from the system. The  switch  also  prevents  the  system from  operating  in 
low ambient temperatures below 50º F (10º C). 
 
The switch operating pressures are: 
 
    Low Pressure Function:                                            High Pressure Function: 
Open at 28 psig (1.97 kg/cm)                                  Open at 384 psig (27.0 kg/cm) 
Close at 29 psig (2.04 kg/cm)                                  Close at 298 psig (21.0 kg/cm)  
						

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As a backup measure to protect the system from an over-pressure situation a pressure 
relief valve is also incorporated into the flow circuit. The relief valve will open between 
550 and 610 psi and will re-close once pressures are relieved below those pressures.  
14. Description of Vapor Cycle Air Conditioner and Installation 
 
This  section  contains  a  general  overview  of  a vapor-cycle  air  conditioning  system  and 
how  it  functions.  This  type  of  system  operates  in  a  closed  loop,  in  which  the  refrigerant 
absorbs  heat  from  the  cabin  and rejects  it  into  the  outside air.  The  refrigerant  then 
returns to the cabin to repeat the cycle. The operation of the system is described below 
(See Figure 1-2). 
 
The  compressor  receives  low  pressure  heat  laden  refrigerant  vapor  from  the 
evaporators. The compressor pressurizes the refrigerant depending on system demand. 
This  increases  the  temperature  of  the  refrigerant.  At  this  temperature  and  pressure  the 
refrigerant is above its boiling point. The compressor discharges superheated refrigerant 
vapor to the condenser. 
 
The  refrigerant flows  into  the  condenser.  The  condenser  has  numerous  cooling  fins  in 
which the vapor  is pumped. In the condenser the high pressure vapor condenses into a 
high  pressure  liquid by  reducing  the  temperature  of the  refrigerant.  This  is  achieved  by 
forcing  air over  the  surface  of  the  condenser  enabling  heat  to  transfer  from  the 
refrigerant to the outside air thus reducing its temperature. Only refrigerant in the form of 
a high pressure liquid leaves the condenser outlet. 
 
The  high  pressure  liquid  refrigerant  flows  into  the  receiver-drier  which  stores,  dries  and 
filters the liquid refrigerant. 
 
The  liquid  refrigerant  then  flows  from  the  receiver-drier  to  the  expansion  valves.  The 
expansion valves changes the refrigerant into low pressure, low temperature liquid/vapor 
by  lowering  the  pressure  using  a  variable  orifice.  The  orifice  has  high  pressure on one 
side  (from  the  receiver-drier)  and  low  pressure on the  other  (evaporator  and 
compressor)  and  allows  a  small  quantity  of  refrigerant  to  flow  through  it.  The  sudden 
drop  in  pressure  and  temperature  causes  some  of  the  refrigerant  to  vaporize.  The  low 
pressure  low  temperature  liquid/vapor  then  flows  to  the  evaporator  where  the  heat  is 
transferred from its surface to the refrigerant through vaporization. The heat comes from 
inside  the cabin and  is  blown  over  the  evaporator’s  surface.  Once  the  refrigerant  has 
completely vaporized and reached its saturation point it should still be able to carry more 
heat.  The  refrigerant  continues  to  flow  through  the  remainder  of  the  evaporator  coils 
absorbing more heat and becoming slightly superheated. 
 
The  low  pressure  low  temperature  slightly  superheated  vapor  refrigerant  flows  to  the 
compressor and the cycle repeats itself. 
 
   
						

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Figure 1-2 – Refrigeration Cycle Illustration 
(NOTE: This illustration is provided as a reference only and may not match actual installation) 
 
 
  
Compressor 
Condenser 
Aft Evaporator 
Receiver- 
Drier 
Bypass 
Valve 
Expansion 
Valves 
Fwd Evaporator 
high-press. high-
temp gas 
low-press. low-
temp gas low-press. low-
temp liquid 
high-press. high-
temp liquid  
						

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CHAPTER 2 
AIRWORTHINESS LIMITATION SECTION 
 
1. Airworthiness Limitations 
 
The  Airworthiness limitations  section  is  FAA  approved  and  specifies  inspections  and 
other  maintenance required  under  Sections  43.16  and  91.403  of  Federal  Aviation 
Regulations unless an alternative program has been FAA approved. 
 
“No airworthiness limitations are associated with this type design change.” 
 
FAA approval: 
 
______________________________________________________________________ 
ACO Representative                                                                                     Date 
 
 
   
						

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CHAPTER 3 
INSPECTIONS AND OVERHAUL  
1. Inspection Requirements 
 
PERIODIC INSPECTIONS 
(Hours are aircraft time) 
 Item Annual Every 25 Hours of Operation Every 100 Hours of Operation Special Inspection Information 
Evaporator Blower Hi/Lo Operation  X   X Check for operation  
Condenser Blower(s)  X    X Check for operation     Forward & Aft Evaporator Blower Motor 
X   X  Check for operation in Hi and Lo settings 
Compressor Drive Belt  
 X  X  X Check belt tension, and for signs of excessive wear (example: glazing, cracks, and exposed fibers) Air Conditioner Placards & Markings (see chapter 5) 
X   X Check for security and legibility 
Air Conditioner Compressor Assembly  
 X  X  X Check for operation, security of attaching hardware, and signs of oil or refrigerant leaks. Inspect compressor pulley assembly for minimum 0.3” (7.62 mm) clearance between pulley and transmission support tube Air Conditioner Compressor Mount  X    X Check for cracks and security of attaching hardware 
Plumbing and Fittings X  X Check for security and signs of oil or refrigerant leaks Air Conditioner Compressor drive pulley (mounted to main rotor input shaft) 
X  X Check for security of attaching hardware  
Blower Electrical connectors X   Visually inspect for signs of overheating. See sec. 2.0 below for details. 
 
 
2. Inspection Of Blower Electrical Connectors (annual requirement) 
 
a) Locate the Molex electrical connectors that power the aft evaporator and condenser 
blowers. See figures 4-1,2 and 4-9 thru 13.The connectors are at the interface between 
the blower harness and the aircraft harness and identified by their white plastic housing. 
Note that the evaporator blowers have an additional connector to inspect located several 
inches away from the harness connector.  
NOTE: Aft evaporators supplied in late 2014 and newer use a gray plastic Deutsch 
connector and are not part of this inspection requirement.  
						

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b) De-mate each connector and inspect both mates for signs of overheating 
(discoloration or plastic deformation). If any signs of overheating of the housing are 
present the system must be rendered inoperative and the connector housing and 
contacts replaced before further operation. Contact ACC service dept. for replacement 
parts if necessary. 
c) Installation & replacement of the wire harness electrical connectors for the evaporator 
and condenser blowers. 
To avoid potentially serious overheating issues the Molex style connectors (identified 
by their white plastic housing) installed on the aircraft harness for connecting to the 
evaporator and condenser blowers must be installed per ACC procedure PPP23 and 
only using the appropriate terminal crimp tool. This document is available on the 
ACC website www.aircommcorp.com/customer-support/service-manuals/. 
 
 
3. Component Overhaul / Replacement Schedule 
 Description Part Number Overhaul / Replacement Hours 
Forward Evaporator Blower Motor   
ES61064-1   
The blower manufacturer recommends TBO at 1000 hrs. At the discretion of the operator, it is acceptable to operate the blower until failure. A blower failure will result in a reduction in cooling, but no safety-of-flight issues are involved. Aft Evaporator Blower Motor ES61142-1 Same as above 
Condenser Motor/Fan Assembly ES73131-1 (side mount) S-7095EC-1 or -2 (tail boom) Same as above 
   
						

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CHAPTER 4 
LOCATION AND ACCESS 
1. Location of Air Conditioner Components 
 
 
 
Nomenclature Description of Location 
 Air Conditioner Circuit Breaker & Relay Panel  Forward bulkhead of right side baggage compartment 
 Air Conditioner Control Panel  Overhead panel or Instrument Panel 
 Forward (Cockpit) Evaporator and Blower  
RH side center console below instrument panel in chin bubble area – blower is integral to forward evaporator 
 Aft (Main Cabin) Evaporator and Blower  Transmission deck just forward of transmission, right side 
 Condenser Assembly and Blower Assembly  
RH baggage compartment (200 &202 Systems) Forward Tail Boom (Optional Configuration, 204 System) 
 Compressor  Aft LH section of transmission compartment 
Refrigerant Plumbing 
Routes from compressor, to area below baggage compartment, and forward to nose area (As refrigerant plumbing connects compressor, condenser, and evaporators, it may be necessary to access these components through several panels and cabin headliner  Hi & Lo Service Ports  Adjacent to Aft Evaporator 
 Receiver Drier Bottle  
Adjacent to condenser assembly in RH baggage compartment (200 &202 Systems), below right  baggage compartment (204 Systems)  Bypass Valve  Aft cabin bulkhead in forward fuel bay 
 Binary Switch  Adjacent to Aft Evaporator  
						

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SIDE VIEW 
Figure 4-1 – Layout of AS350 Air Conditioning System 
 
 
 
TOP VIEW 
Figure 4-2 – Layout of AS350 Air Conditioning System 
Air Dist Instl 
Compressor Instl 
Condenser Instl (Baggage) 
Plumbing Instl 
Aft Evap Instl 
Electrical Instl 
Forward Evap Instl 
Air Dist Instl 
Aft Evap Instl 
Condenser Instl (Baggage) Forward Evap Instl 
Compressor Instl 
Condenser Instl (Tail Boom) 
Condenser Instl (Tail Boom)