AirComm Corporation Bell 407 Air Conditioner Instructions for Continued Airworthiness User Manual

							AIR CONDITIONER SERVICE MANUAL 407EC-200M-2 
 
 
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19. AIR CONDITIONER FEATURES 
The  vapor  cycle  air  conditioner  features  one  or  two  forward  mounted  evaporator 
(cockpit),  one  aft  mounted  evaporator  (main  cabin),  one  condenser,  and  a 
compressor  driven  by  the  tail  rotor  drive  shaft  just  forward  of  the  aft  engine 
compartment  fire  wall.  These  components  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 Blower mode.  
In  the  A/C  mode,  conditioned  air  is  provided  by  the  forward  and  aft  evaporators 
to the cockpit and main cabin areas respectively. 
In the Blower 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  switches for  the  air  conditioner  system  are located  on  the  existing 
overhead  circuit  breaker  /  switch  panel  between  the  pilot’s  and  co-pilot’s  seats. 
This panel consists of the A/C and Blower switch, two switches, for the control of 
the Fwd and Aft evaporator blower fan speeds.  
 
 
Figure 1:  Overhead Panel A/C Control Switches 
The  blower  motors  feature  dual  speed  operation  (Hi  or  Lo),  and  this  feature  can 
be  used  in  both  the  air  conditioner  or blower  modes.  The  air  conditioner 
temperature  control  knob  is located  under  the  left  hand  side  of  the  instrument 
panel.  
						

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Figure 2:  A/C Temperature Control Knob 
The  compressor  is  mounted  to  the  surface  of  the  engine  drain  pan,  in  the  aft 
aircraft  left  portion  of the  engine  compartment.  It  is  driven  by  a  V-belt  and  a 
pulley  which  is mounted  to  the  tail  rotor drive  shaft.  Access  to  the  compressor is 
provided by engine compartment access doors. 
Airflow through the condenser heat exchanger is provided by one 28 volt DC high 
performance  blower,  and  is  enhanced  by  means  of  a  retractable  scoop  door 
providing ram air in forward flight. 
The  aft  evaporator  is  equipped  with  a freeze switch.  The freeze switch  probe  is 
located  in  the  core  of  the  evaporator  heat  exchanger.  This unit  performs  two 
functions;  1.  It  acts  to  prevent  coil  freeze-up  by  limiting  the  minimum  coil 
temperature  to  32º  F  (0º  C),  and  2.  It  acts  in  conjunction  with  the  cabin  air 
temperature  control  system,  by  controlling  the  bypass  of  refrigerant  through  the 
evaporator coil in response to adjustment of the temperature control knob located 
on the left hand lower section of the instrument panel. 
The  system  is  also  equipped  with  a  Binary  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: 
 Cut-out at 28 ± 2.8psi (2.0 ± .2 Kg/cm²)  
 Cut-in at 29 ± 4.3 psi (2.1 ± .3 Kg/cm²) 
 High Pressure Function: 
 Cut-out at 384 ± 30psig (28.0 ± 2.0 
Kg/cm²) 
 Cut-in at 298 ± 43psig (20.9 ± 2.0 
Kg/cm²) 
 
   
						

							AIR CONDITIONER SERVICE MANUAL 407EC-200M-2 
 
 
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20. DESCRIPTION  OF  THE  VAPOR  CYCLE  AIR  CONDITIONER  AND  ITS 
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.  Refer to the Refrigeration Cycle Illustration. 
Liquid  refrigerant  is  contained  in  the  receiver-drier  under  pressure  from  the 
compressor.  The  receiver-drier  also  filters  the  refrigerant  through  a  material 
known as desiccant. The desiccant ensures that the fluid leaving this component 
is free of any water or other contaminants. 
The  low  pressure  (suction)  line  from  the  compressor  is  attached  to  the 
evaporator lines and  causes  the  refrigerant  to  be  pulled  out  of  the  receiver-drier 
and  through  the  expansion  valves.  The  expansion  valves  serve  as  a  controlled 
spray orifice, to spray the correct amount of refrigerant into the evaporator. 
This  regulation  of  refrigerant  allows  the  liquid  to  absorb  the  heat  from  the  cabin 
air and transform it to a vapor state just prior to its exiting the evaporator. 
The  low  pressure  vapor  is  then  drawn  into  the  compressor  where  its  pressure  is 
raised  to  approximately  200  psi  (14.06  kg/cm),  and  its  temperature to  around 
200º  F  (93.3º  C).  The high  pressure  /  high  temperature  vapor  then  travels  to  the 
condenser  (a  heat  exchanger  cooled  by  a  flow  of  outside  air).  Heat  is  extracted 
from the refrigerant, and as it cools it condenses back into a liquid and flows into 
the receiver-dryer, ready to repeat the cycle. 
   
						

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21. Refrigeration Cycle Illustration 
(PLEASE NOTE: This illustration is provided as a reference only and may 
not match actual installation) 
 
 
 
 
Figure 3:  Refrigerant Cycle Illustration 
 
High pressure liquid 
Low pressure vapor 
Low pressure liquid 
High pressure vapor 
Compressor  
Condenser 
Evaporator 
Receiver 
Drier Bottle  
Bypass 
Valve 
Expansion 
Valves  
Evaporator   
						

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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 paragraph 43.16 and 91.403 of the Federal Aviation 
Regulations unless an alternative program has been FAA approved. 
 
No airworthiness limitations are associated with this type design change. 
 
 
 
____________________________________________________________________________
ACO approval                                                                                                         Date  
						

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CHAPTER 3 
INSPECTIONS 
 
1. INSPECTION REQUIREMENTS 
 
PERIODIC INSPECTIONS 
(Hours are aircraft time) 
 
Item Annual, +/- 1 month Every 50 Hours of  Operation, +/- 5 hrs. Every 100 Hours of Operation, +/-10 hrs. Special Inspection Information Evaporator Blower Hi/Lo Operation  X   X Check for operation. 
Condenser Blower Motor, Scoop Door Actuator ES39210-2 
 X    X Check for operation.  
Forward Evaporator Blower Motor ES61064-10 Aft Evaporator Blower Motor ES61142-1 
X  X Check for operation in Hi and Lo settings. 
Compressor Drive Belt 7270 (7265 ALT)  X  X  X 
Check belt tension, and for signs of excessive wear (example: Glazing, Cracks, and exposed fibers). Air Conditioner Placards & Markings (see chapter 4) 
X   X Check for security and legibility. 
Compressor Assembly S-3008EC-6  X  X  X 
Check for operation, security of attaching hardware, and signs of oil or refrigerant leaks.  
Compressor Mount S-3003EC-1  X    X 
Check mount for cracks, and security of the attaching hard -ware. 
Aft Evaporator Foam Insulation X   Check for security and signs of deterioration, replace as necessary. 
Plumbing and Fittings X  X Check for security and signs of oil or refrigerant leaks. Compressor drive pulley S-3532EC-4 X  X Check for security of attaching hardware.  
Blower Electrical Connectors X   
Visually inspect the condenser and evaporator blower connectors for signs of overheating 
 
2. COMPONENT OVERHAUL / REPLACEMENT SCHEDULE 
Description Part Number Overhaul / Replacement Hours Condenser & Forward / Aft Evaporator  Blower Motor & Fan replacement   
ES73186-1 (Condenser Blower Assembly) ES73190-1 (Condenser Blower Assembly – Brushless)  ES61064-10 (Fwd. / Aft Evaporator Motor)  ES61142-1 (Aft Evaporator Motor) 
The blower manufacturer recommended TBO is 500 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.  
						

							AIR CONDITIONER SERVICE MANUAL 407EC-200M-2 
 
 
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3. INSPECTION PROCEDURES.  
 
NOTE 
Refer to “Chapter 4 location and access” to locate all components for inspection. 
 
A. Inspection of the FWD and AFT evaporator blower motors 
 
CAUTION 
Fans are designed to operate with the resistance of the entire ducting system. 
Operation of the evaporator fans with any part of the distribution system 
removed may cause permanent damage to the fan motor. 
 
WARNING 
Fans may take up to 10 seconds to start after the switch is turned on. Keep 
hands away from fan whenever switch is in Fan or A/C positions. 
 
a. At the Cockpits Air Conditioner Control Panel place the AIR 
COND switch in the FAN position and verify: 
1. That both the fwd and aft fans are activated and operating – 
Place blower switches to “low” and “high” to verify blowers 
increase and decrease speed accordingly. 
2. That the condenser fan is non-operational. 
3. That the compressor clutch is disengaged. 
 
b. Place the AIR COND switch in the OFF position and verify that: 
1. That both the fwd and aft fans deactivate 
2. That the compressor clutch remains disengaged.  
 
B. Inspection of the air conditioner condenser 
 
NOTE 
This inspection may be performed with the air conditioner charged with 
refrigerant or it may be performed with no refrigerant in the system. In the 
case where there is no refrigerant in the system or the system is low on 
refrigerant or in the case where the ambient temperature is low, the binary 
switch will need to be jumpered. The temporary installation of a jumper wire 
across the terminals of the binary switch will do no harm even if it was not 
necessary. 
 
CAUTION 
 
THE TEMPORARY JUMPER MUST BE REMOVED AFTER THIS 
INSPECTION IS COMPLETED. 
 
a. Visually inspect condenser air inlet for any obstructions or 
debris. Airflow in this area is critical for air conditioner 
operation.  
						

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b. Install a jumper between the contacts of the binary switch if 
required. 
c. Connect 28V ground power to the aircraft and place the A/C 
mode switch in the “A/C” position and verify that: 
1. Condenser scoop opens. 
2. Condenser fan is activated and operating. This fan should 
pull air into the aircraft through the open scoop and exit at 
the screen below the condenser. 
3. Compressor clutch is engaged. Verify compressor clutch 
engagement by visually observing the clutch plate clamp to 
the compressor rotor or an audible click when the switch is 
moved to “on”. 
 
d. Place the A/C mode switch into the Off position and verify that: 
1. The condenser fan is deactivated. 
2. The condenser scoop closes. 
e. Ensure that the jumper wire is removed from the binary switch 
 
C. Inspection of compressor drive belt 
a. Remove transmission cowling to gain access to compressor 
drive belt and visually inspect the A/C compressor drive belt for 
the following: 
1. Any signs of excessive wear. 
2. Any signs of glazing. 
3. Any cracks or missing pieces. 
4. Any exposed fibers. 
b. Verify proper belt tension as shown in the illustration in Figure 
4. 
 
 
Figure 4:  belt tension inspection 
   
						

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D. Inspection of air conditioner placards and markings. 
a. Check all air conditioner placards and markings for security and 
legibility. 
 
E. Inspection of air conditioner compressor assembly 
NOTE: 
The air conditioning system must be serviced with refrigerant to perform this 
inspection 
a. Connect 28V ground power to the aircraft and place the A/C 
mode switch in the “A/C” position and verify: 
1.  Compressor clutch is engaged. 
b. Place air conditioner switch to the OFF position and verify: 
1. Compressor clutch is disengaged.  
c. Visually inspect the compressor assembly for the following:  
1. Security of all attaching hardware. 
2. Signs of refrigerant or oil leaks.  
3. Signs of excessive belt slippage or excessive heat.  
 
F. Inspection of Air Conditioner Compressor Mount Assy. 
Visually inspect compressor mount of any signs of the following: 
1. Any cracks. 
2. Security of attaching hardware.  
3. Elongation of component mounting holes. 
4. Any loose rivets. 
 
G. Inspection of Air Conditioner Refrigerant Plumbing 
Visually inspect plumbing and fittings for any signs of the following: 
1. Refrigerant gas or oil leaks. 
2. Chaffing or excessive corrosion.  
3. Security of attaching hardware. 
 
H. Inspection of Compressor Drive system 
1. Cut the safety wire on the belt tensioning link assembly jam 
 nuts and adjust the tensioning link assembly to loosen the 
 compressor drive belt.  
2. Check the S-3532EC drive pulley for play relative to the tail 
 rotor drive shaft, both in the direction of rotation as well as for 
 lateral movement relative to the shaft, and inspect area around 
 the base of the drive ring at the shaft for any buildup of metal 
 dust/powder residue. 
3. If there is any detectable looseness, and/or if there is significant 
 metal dust/powder residue present, refer to Section 8 for  
						

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 removal instructions to allow removal and further inspection to 
 determine if the pulley or drive ring need to be replaced. 
4. If there is no detectable looseness, and no significant metal 
 dust/powder residue present, re-tension the belt per Section 8. 
5. Check security and condition of all related fasteners. 
 
I. Inspection of Blower Electrical Connectors 
1. Locate the electrical connectors that power the evaporator and 
condenser blowers. The connectors are at the interface 
between the blower harness and the aircraft harness and 
identified by their white plastic housing. 
 
Note: 
For 407EC-202 and 407EC-203 AC kits the evaporator blowers have an additional 
connector to inspect located several inches away from the harness connector. 
 
2. De-mate each connector and inspect both mates for signs of 
overheating (discoloration or plastic deformation).  
3. 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.