The drying agent is removed by removing the
hose connecting the lower cap and the lower
manifold and unscrewing the drier lower cap. All
traces of the contaminated agent should be
removed and the lower cap replaced, and the
lower manifold hose connected. The drying agent
should be quickly placed in the drier so that it does
not pick up moisture from the air. Care should
be given to the replacement of the indicating
agent. The top cap should be screwed in place
immediately after observing the condition of the
indicator so that the moisture or humid air does
not cause the indicator to change color.
The caps on the drier should be screwed down
until they bottom. The caps should be removed
and replaced by hand only. It is not necessary to
tighten the caps extremely tight. The caps are
sealed with O-ring packings, which usually give
good service. If leakage occurs, the O-ring should
be replaced. Refer to the applicable Operation and
Service Instruction Manual (which includes the
Illustrated Parts Breakdown) for the part number
of the O-ring.
NOTE: All maintenance on the oxygen ser-
vicing trailer should be performed in accordance
with the instructions contained in the applicable
Operation and Service Instructions Manual or set
of Maintenance Requirements Cards.
Maintenance requirements for the gaseous
oxygen servicing trailer are provided on daily,
preoperational, or periodic maintenance re-
requirement cards. These cards provide the
minimum requirements necessary to maintain the
equipment and ensure that no item is overlooked.
They do not contain instructions for repair,
adjustment, or means of rectifying defective
conditions. The cards are arranged in a work
area sequence similar to aircraft maintenance
requirements cards so that the inspections can be
held in an efficient manner.
The daily requirements should be accom-
plished prior to the first use of the equipment for
that day. It may be necessary to repeat some of
the requirements prior to each use of the equip-
Gaseous Oxygen System Servicing
The danger involved in the transfer of gaseous
oxygen as well as its importance to the pilot
requires that it be handled with care. The
following general safety precautions should be
followed for safe operation of the oxygen servic-
1. Only qualified operators should operate
the trailer for recharging aircraft oxygen systems.
Complete familiarity with the trailer is a basic
prerequisite to safe operating techniques.
2. The aircraft electrical system must be
turned off, and no other servicing should be
conducted on the aircraft while servicing the ox-
3. Never permit oil, grease, or other readily
combustible materials to come in contact with
oxygen cylinders, valves, regulators, gauges, or
4. The servicing hose and aircraft connection
fittings must be thoroughly inspected prior to
servicing. Any trace of oil, grease, or foreign
material must be carefully removed.
5. The servicing hose should always be bled
prior to connecting with the aircraft oxygen
6. Open all valves slowly.
7. Always know the pressure existing in the
aircraft system to be filled and the pressure in all
cylinders to be used in the refueling process before
starting the recharging operation.
8. Ensure that the line valve on the discharge
end of the servicing hose is closed at all times when
not actually servicing aircraft.
9. Never have more than one cylinder
control valve open during operation.
10. The servicing hose must never be tightly
stretched to reach a connection. Position the
trailer so that the hose is not under tension.
11. When disconnecting the transfer hose
from an aircraft fitting, loosen the connection
slowly to prevent rapid bleeding of the trapped
12. A malfunctioning pressure regulator
should be disconnected from the line by closing
its associated shutoff valves. The trailer can then
be operated with the remaining pressure regulator.
13. When moving the trailer from place to
place, cylinder valves should be closed.
Before servicing an aircraft gaseous oxygen
system, you should take care to ensure that the
six manifold control valves on the trailer control
panel are closed. If these valves are partially
opened, the cylinder pressure will equalize from
one to the other.