EL125 Test 2 (draft)

Block Diagram

Individual blocks that represent several components like PCBs and LRUs

Wiring Diagram

May identify each component within a system by its PN, SN, and wires by MIL code

Pictorial Diagram

Pictures of components are used instead of the conventional electrical symbols

Schematic Diagram

Illustrates the principle of operation, indicates location of components with respect to each other

Aviation approved stranded wires must have at least

19 strands

Cable

Two or more separately insulated wires grouped together in the same outer sleeve

Twisted Pair

Two or more separately insulated conductors twisted together

Radio Frequency Cable

A single insulated center conductor with a metallic braided outer conductor

Why do we ground and bond?

1. PROTECTION OF THE AIRCRAFT AND PERSONNEL

2. AGAINST LIGHTNING DISCHARGE IN THE AIR

3. RETURN PATHS FOR CURRENT FLOW

4. ELIMINATE RF POTENTIALS

5. PROTECT AGAINST SHOCK HAZARDS

6. REDUCE/PREVENT STATIC AND ERRATIC RADIO

7. TRANSMISSIONS AND RECEPTION

8. AVOID STATIC ELECTRICITY BUILD UP

Primary Structure

The main frame, fuselage and/or wing structure of the aircraft

Grounding

Process of electrically connecting conductive objects to a conductive structure or return path

Bonding

Electrical connection with a low resistance material of two or more conducting objects that wouldn’t be connected otherwise (with use of bonding straps, studs)

Shielding

The process of applying a metallic covering to wiring and equipment to eliminate electromagnetic interference

EMI

Caused when electromagnetic fields (radio waves) induce high frequency (HF) voltages in a wire or component

Advantages to bonding

1. PROTECTS FROM ELECTRIC SHOCK

2. PREVENTS STATIC ELECTRICITY BUILD UP THAT

   INTERFERES WITH RADIO AND NAVIGATION

   EQUIPMENT

3. PROVIDES LIGHTNING PROTECTION-ALLOWS

   CURRENT TO PASS THROUGH THE AIRFRAME

   WITH MINIMUM ARCING

Ground wires should never be run through what material structure?

Magnesium (it’s highly flammable)

Carbon fiber and grounding

1. Avoid grounding to carbon fiber structure

2. Although conductive, bad ground

3. Composite fabrication requires many substances that don’t conduct

Plating

A coating on wires to slow the oxidation rates

Factors that affect wire selection

1. Design temp

2. Flexibility

3. Abrasion Resistance

4. Strength

5. Insulation

6. Electrical Resistance

7. Weight