This week discusses activities during removal/installation
of components, tests to be performed on pressurisation system and other allied
maintenances.
COMPONENT INSTALLATION
Before installing any component of a
cabin pressure control system, an inspection should be made to ensure that no
deterioration of rubber components, corrosion of metal parts or other damage
has occurred during storage or transit. The security of pipe connections,
electrical connections, actuators, etc., should also be checked and, where
specified, pre-installation functioning tests carried out.
Some aircraft pressure controllers' discharge valves and
safety valves operate as preset units and must only be used in specific
combinations. When renewing or replacing such units it is therefore essential
to ensure that their part numbers are correct for the installation.
Pressure
Controllers
It is recommended that where facilities are available,
controllers should be bench tested before installation to ensure that the
controlling mechanism has not been disturbed during storage or transit. Details
of tests peculiar to particular types of controller should be obtained from the
relevant Aircraft Maintenance Manual.
When assembling static pressure and reference pressure
sensing pipelines, care is necessary to ensure that no obstruction
or leakage can occur. Particular care is necessary to ensure that all pipes are
correctly assembled. Cabin pressure must not leak into low pressure pipes or
chambers as this would unbalance the control characteristics of the system.
Where vents to cabin pressure form part of the system, they should not be
obstructed by loose trimming or soundproofing materials.
After the installation is completed, functioning
tests should be made to prove the correct connection or adjustment of
electrical circuits, micro-switches, altitude selectors, rate of change control
mechanisms and the pipeline system. Details of tests applicable to particular
aircraft installations should be obtained from the relevant Aircraft
Maintenance Manual. General guidance on the testing of pressurization systems
is provided in this discussion.
