Aircraft Temperature Control System Components

Aircraft Temperature Control System Components

(a)       The temperature control of complex air conditioning systems is usually accomplished either electrically or electronically. Consequently the following precautions are normally adopted when installing such equipment.

(b)       As temperature-sensing elements are positioned so that they will be directly affected by the changes in duct and cabin air temperatures. Therefore, care should be taken to ensure that elements sensing cabin air temperature are not shielded by loose upholstery, and are protected if paint spraying or similar operations are performed in their vicinity.

(c)       The damping effect of shock absorbers and anti-vibration mountings which may provide support for electronic amplifiers and similar sensitive equipment, should be checked by hand after installation.

(d)       Cables interconnecting components must be of the rating specified by the manufacturer and all connections must be clean and securely made.

(e)       When installing control units, care should be taken that such controls as pre-set potentiometers and fine adjustment resistors are not disturbed.

(f)        On completion of the installation of a component, sensitivity tests and final balance adjustments should be carried out in accordance with the procedure laid down for the specific aircraft system. Tests of the overall controlling function should also be made by selecting various temperature settings and noting that the actuators controlling such components as heat exchanger cooling air flaps, by-pass valves, etc., move in the appropriate directions.

Valves

(a)       Mechanically and electrically-operated valves are employed in the various types of heating, ventilating and air conditioning systems and therefore Maintenance Manuals should always be referred to for the appropriate installation procedures. The details given in the following paragraphs are of a general nature.

(b)       All valves should be inspected before installation for cleanliness, signs of damage and freedom of movement. Functional checks should be made on electrically-operated valves, e.g. spill valves, by-pass valves and choke valves to ensure that limit switches are correctly adjusted at the extremes of valve travel.

(c)       Valves are often marked with arrows to indicate the direction of flow and particular care is necessary to ensure that the valve is installed in correct relation to flow.

(d)       The attachment of valves to their respective mountings and duct sections must be secure and torque loadings strictly observed.

(f)        Electrical connections to actuators and to position indicators where fitted, should be checked against the relevant wiring diagrams, and plugs, sockets and terminal screws checked for security.

(f)        On completion of the installation of a valve, an in-situ functional test should be carried out in accordance with the procedure specified in the relevant Component and Aircraft Maintenance Manual.