BOOST
VENT
NITROGEN
OFF
OFF
BOOST PUMP
BOOST PUMP
NITROGEN
BOOST PUMP
NITROGEN
DRIVE VALVE
DRIVE VENT
SUPPLY VALVE
DRIVE
SUPPLY
PRESSURE GAUGE
PRESSURE GAUGE
NITROGEN PANEL
OXYGEN
SERVICE
CONNECTION
OXYGEN
REGULATOR
VENT
BYPASS
OFF
OXYGEN
BOOST
VENT VALVE
OXYGEN
SELECTOR
SUPPLY
VALVE
REGULATOR INLET
PRESSURE GAUGE
REGULATOR OUTLET
PRESSURE GAUGE
PRESSURE GAUGE
OXYGEN PANEL
ASf10019
Figure 10-19.--Servicing controls and indicators.
NOTE: The number in parentheses following a
servicing a high-pressure system, ensure that the
component name refers to figure 10-13.
oxygen supply pressure gauge indicates greater than
450 psi. Install a fully charged oxygen cylinder if the
CHARGING AN EXTERNAL SYSTEM.--
gauge indicates less than 450 psi. If the pressure is
Before charging a system, prepare the oxygen
greater than 2,150 psi, use the pressure equalization
servicing unit as outlined below. Three methods can be
delivery method. If the pressure is less than 2,150 psi,
used to charge an aircraft system with the A/U26U-1:
use the boost pump.
direct servicing from the oxygen cylinder (referred to
2. Determine the pressure of the system to be
as the "pressure equalization" or "cascade" method);
charged.
boost pump using nitrogen drive; and boost pump
using air drive. Prepare the servicing unit for charging
3. Position the unit sufficiently close to the system
an external system as follows:
to be charged to avoid stretching the servicing
hose.
1. Perform a preoperational inspection on the
oxygen servicing unit in accordance with its
4. Attach the servicing hose and valve with the
preoperational checklist.
appropriate servicing adapter (figure 10-18) to
NOTE: When servicing a low-pressure (0 to 500
the oxygen service connection on the oxygen
psi) system, ensure that the oxygen supply pressure
module. (See figure 10-16, right side view.)
gauge indicates greater than 250 psi. Install a fully
5. Verify that all valves on the servicing unit are
charged oxygen cylinder if the gauge indicates less
either OFF or closed.
than 250 psi. If the pressure is greater than 650 psi, use
6. Ensure that the oxygen regulator on the oxygen
the pressure equalization delivery method. If the
module reads zero.
pressure is less than 650 psi, use the boost pump. When
10-33
