3.
The OBOGS’s Backup Oxygen System (BOS) has a capacity of 260 liters of oxygen.

4.
Adjustment of oxygen regulators will be  ac-complished by the medical attendant.

5.
The OBOGS control/status panel, located at the top of the medical cabinet is described in para-
graph 4.12.13.2.

4.12.13 Oxygen Generating System. A OBOGS (Figure 4-28) powered by bleed air is installed in the tran-
sition section. The system will charge from empty in 30 minutes with either APU or engine bleed air power. It is fully operational with either APU power, or when engines apply greater than 30% torque. Each regulated station has the capability to provide oxygen up to 10 liters / minute. The quick disconnect oxygen outlet has the capability of 36 liters / minute. Maximum system output is 36 liters / minute. The OBOGS utilizes engine bleed air and electrical power from the aircraft to provide oxygen enriched breath-ing gas for MEDEVAC operations. Bleed air is conditioned by a heat exchanger and .lter assembly and then routed to a concentrator. The concentrator utilizes pressure swing ab-sorption technology to produce oxygen enriched breathing gas. When bleed air is removed from the system, a self contained backup oxygen supply (BOS) with a capacity of 260 liters, provides 15 minutes of oxygen to six litter pa-tients at 3 liters / minute. The backup system will be op-erational when O2 requirements exceed the .ow rate. The pilot has control of the system and must activate the OBOGS prior to attendants using the oxygen delivery sys-tem. The attendants can monitor the .ow of oxygen by observing the OXY FLOW dial on the OBOGS panel. When the purity of the oxygen falls below 91 percent the OBOGS unit will switch to backup oxygen supply (BOS) breathing gas and trip the BIT FAULT indicator on the status panel.
4.12.13.1 Controls and Functions. Controls and indi-cators are located on a panel above the medical cabinet. The pilot has the capability to disable the OBOGS if re-quired.
CONTROLS/  FUNCTION 
INDICATORS 
OXY FLOW  Indicates  rate  (lpm)  of  oxygen 
being delivered. 
BOS QTY  Indicates level (liters) of oxygen. 
PWR ON  Indicates .ow of oxygen. 
Light 
BOS  Indicates backup oxygen is being 
Light  supplied. 
BIT FAULT  Indicates system fault. 
Light 

4.12.13.2 Normal Operation.
NOTE
Built in test (BIT) will be initiated on initial start up of OBOGS, and will last 3 to 5 min-utes. BIT light on monitor panel will be lit during BIT.
1.  
AIR SOURCE HEAT/START switch -APU or ENGINE .

2.  
AUX SW panel OBOGS switch -ON Check that BIT/FAULT light goes out within 5 min-utes.

4-56 Change 4
5.
Attach the patients oxygen hose to the patient and to the corresponding oxygen regulator on the side medical control panel.

6.
Select the desired oxygen rate on the regulator.

3.
The medical attendant determines the oxygen system is available after the PWR ON light is illuminated.

4.
Determine which patients need oxygen and ob-tain an oxygen hose and mask from the medical cabinet.

Change 4 4-56.1/(4-56.2 Blank)
NOTE
Oxygen .ow from the OBOGS is degraded with increased altitude or ambient tempera-ture. Up to 10,000 feet, the .ow can be up to 10% below the selected rate. Between 10,000 and 15,000 feet the .ow rate can be 15% below the selected rate. To achieve a speci.c minimum .ow rate above 10,000 feet, the next higher rate may be needed.
To prevent depleting oxygen levels, ensure unused oxygen regulators are turned to OFF.

Puritan Bennet outlets are provided, but connection
plates may be changed to others: i.e. Ohio, Chemetron, etc,
as required.
4.12.13.3 Back Up System Operation.
　
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