Wednesday, October 10, 2012

Aircraft Wiring and Schematic Diagrams

Module 7 of EASA Part 66 include the wiring and schematic diagrams in the syllabus. For the symbols, I had been using the Boeing documents and the DC10 Lamn book.

The following  are the topics that are included in the teaching:

a. Differences between wiring and schematic diagram.

To demonstrate the differences, I use the example from DC schematic diagram and airbus wiring diagram.

Schematic Diagram DC10 Hydraulic System
The above is taken from DC 10 Lamn book. Schematic diagram focuses to show how the system operates. It is suitable for learning and teaching and for troubleshooting. The wiring diagram, as shown below, is necessary for wiring installation and to show the actual path of the wiring. In some trouble shooting situation, it is referred to identify wiring problems, such as short-circuit or open circuit.
Wiring Diagram A320 Hydaulic Pump
The Schematic Symbols

The students were exposed to Boeing symbols taken from the company's documents. Students are expected to be able to identify the common symbols and apply it in the reading of the wiring and schematic diagrams.
One of the 4 pages of symbols used in the module 7

Reading The aircraft Wiring DiagramsThe students are expected to be able to read and capture the essential information. I usually use the DC10 Lamn diagram to get the students to pick up some points in trouble shooting.

Example.. Using the above DC10 hydraulic pump 1 for the practice.
a. Before I go into reading the wiring diagram, I normally go into the design concept of a simple electrical hydraulic pump. Start with the simplest pump where the switch control the pump directly. Then, the use of relay to control the pump. The next type will be to have an overheat protection to switch the pump off.

Then go to the diagram and start with identifying the parts involved in the operation.

b. Switch pump 1 to ON.
- focus on pump 1 and explain the equipment and power supplies involved, such as the pump with the O/H switch, the relay with 2 power supplies, the gen bus and the ADG bus.
- explain the function of air driven generator (ADG) as the emergency resources for electrical power.
- in normal operation, we expect to use the generator power.

c. What will happen when the switch selected to off...?

d. With pump 1 operating, what will happen when overheat switch operated?

About aircraft wiring and schematic diagrams.
1. To supplement the maintenance manual and the IPC, the manufacturers of airplane are required to provide, the wiring and schematic diagrams. It is arranged in the IATA 100 chapters. The chapter 20 is the standard practices for aircraft wiring system.You can get the information about electrical parts and its location.

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