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Unformatted text preview: ATA-39 ELECTRICAL AND ELECTRONIC PANELS
An organized form of power distribution throughout an aircraft is essential, and as an example of this we may conclude by considering the sequence illustrated in the diagrams, although based on the B737 power distribution and control system, are generally representative of the standard approach adopted in other types of public transport aircraft. Figure shows the routing of the feeder lines from the main generators and the APU generator. At the wing/fuselage junction, the lines pass through sealed connectors into the under floor area. All lines are then routed through an electrical/electronic compartment. Those from the main generators pass through sealed connectors into the unpressurized nose-wheel well to connect up with the generator breakers. The feeder lines from the APU generator are connected to its breaker located above floor level within a special compartment (designated P6 panel) to the rear of the captain's position. This compartment contains most of the AC and DC busbars, the bus-tie breakers, voltage control and protection units for all three generators, and an external power control unit. The feeder lines from the main generator breakers pass into this compartment to connect with the AC busbars; a circuit breaker panel is mounted on the front side of the compartment. As a complete unit therefore, the compartment or P6 panel, establishes what is termed the load control centre of the aircraft. The electrical/electronic compartment serves as a centralized area for the rack mounting of the many "black boxes'' associated with automatic (light control, compass, radio, and certain other airframe systems. Removal, installation and maintenance checks of these boxes are thereby facilitated by this arrangement. In order to establish an organized form of systems control by each member of the flight crew, and also of circuit protection, an appropriate number of control panels are strategically located on the flight deck. The panels are designated by the letter "P prefixing the panel numbers, and in the example considered they are as follows: P7 Glare shield panel containing annunciator lights for each pilot P8 Fire protection system control panel P9 Weather radar display indicator and radio communication system selector controls Circuit breakers are located on panels behind each pilot and since they are allied to load control, then they are part of the load control centre, as for example, the P6 panel. The breakers are grouped appropriate to each system. P1 Captain's flight instrument panel P2 Centre engine instrument panel P3 First Officer's flight instrument panel P5 Overhead panel from which electrical power generation systems and other major systems of the aircraft are controlled. Reference to Fig. shows that the panel is subdivided into sections so that control switches, meters and indicating lights are grouped appropriate to their respective systems. For example, section P5- 4 is the primarily one for switching the main generators, APU generator and external power onto the busbars. ...
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