TABLE 11-29. ELECTRONIC/ELECTRICAL SYMBOLS (CONTINUED) Symbol Meaning ojo Two-Circuit, Maintained, or Not Spring- Return Nonlocking Switching, Momentary, or Spring-Retur Locking Switch Combiration Locking and Nonlocking Switch Key-Type Switch Lever Switch Par 11-272 Page 11-126
TABLE 11-29. ELECTRONIC/ELECTRICAL SYMBOLS (CONTINUED) Symbol Meaning 8000 .... 29000 Selector or Multiposition Switch Safety Interlock a te Sensitive Switch Limit Switch 11100 Switches with Time-Delay Feature Flow-Actuated Switch Par 11-272 Page 11-127
TABLE 11-29. ELECTRONIC/ELECTRICAL SYMBOLS (CONTINUED) Symbol Meaning Liquid-Level Actuated Switch Pressure- or Vacuum-Actuated Switch Temperature-Actuated Switch Thermostat Flasher Self-Interrupting Switch Foot-Operated Switch Foot Switch Switch Operated by Shaft Rotation and Responsive to Speed or Direction Chai aIo Switches with Specific Features Par 11-272 Page 11-128
TABLE 11-29. ELECTRONIC/ELECTRICAL SYMBOLS (CONTINUED) Symbol Meaning Governor Speed Regulator
AC D DP MC
I P DB EP NB ) SO SA SW ) SR L ML FR · Relay Inertia Switch Mercur Switch Terminals Par 11-272 Page 11-129
TABLE 11-29. ELECTRONIC/ELECTRICAL SYMBOLS (CONTINUED) Symbol Meaning Cable Termination → Connector Disconnecting Device Connectors of the Type Commonly Used for Power-Supply Purposes Test Blocks Coaxial Connector Waveguide Flanges Waveguide Junction Par 11-272 Page 11-130
TABLE 11-29. ELECTRONIC/ELECTRICAL SYMBOLS (CONTINUED) Symbol Meaning Fuse Lightning Arrester Arrester Gap Circuit Breaker
- CC Protective Relay F S GP T =00 Audible-Signaling Device Microphone Par 11-272 Page 11-131
TABLE 11-29. ELECTRONIC/ELECTRICAL SYMBOLS (CONTINUED) Symbol Meaning Handset Operator's Set Lamp ₩ Visual-Signaling Device Mechanical Connection Mechanical Interlock Mechanical Motion ~ Clutch Brake Par 11-272 Page 11-132
TABLE 11-29. ELECTRONIC/ELECTRICAL SYMBOLS (CONTINUED) Symbol Meaning Manual Control Gyro Gyposcope Gyrocompass Position Indicator Fire Extinguisher Actuator Head Position Transmitter Radio Station a 5· Space Station Par 11-272 Page 11-133
TABLE 11-29. ELECTRONIC/ELECTRICAL SYMBOLS (CONTINUED) Integrated Circuit Amplifiers
GENERAL SYMBOLS MAGNETIC AMPLIFIER
INVERTOR OR
NOT GATE AND GATE WITH THREE INPUTS NAND (NOT AND) GATE Logic Gates
OR GATE NOR (NOT OR) GATE
EXCLUSIVE OR GATE Diode
EMITTER BASE COLLECTOR Transistor Symbols
EMITTER BASE COLLECTOR E - C N
11-273.-11-283. [RESERVED.] Par 11-272 Page 11-134
Par 12-1 Page 12-1 CHAPTER 12. AIRCRAFT AVIONICS SYSTEMS SECTION 1. AVIONICS EQUIPMENT MAINTENANCE
12-1. GENERAL. There are several methods of ground checking avionics systems.
a. Visual Check. Check for physical condition and safety of equipment and components.
b. Operation Check. This check is performed primarily by the pilot, but may also be performed by the mechanics after annual and 100-hour inspections. The Aircraft Flight Manual (AFM), the Airman’s Information Manual (AIM), and the manufacturer’s information are used as a reference when performing the check.
c. Functional Test. This is performed by qualified mechanics and repair stations to check the calibration and accuracy of the avionics with the use of test equipment while they are still on the aircraft, such as the transponder and the static checks. The equipment manufacturer’s manuals and procedures are used as a reference.
d. Bench Test. When using this method the unit or instrument is removed from the aircraft and inspected, repaired, and calibrated as required.
e. Electromagnetic Interference (EMI). For EMI tests, refer to chapter 11, paragraph 11-107 of this AC.
12-2. HANDLING OF COMPONENTS. Any unit containing electronic components such as transistors, diodes, integrated circuits, programmable read-only memory (PROM), Read-Only Memory (ROM), and memory devices should be protected from excessive shocks. Excessive shock can cause internal failures of these components. Most electronic devices are subject to damage by electrostatic discharges (ESD).
CAUTION: To prevent damage due to excessive electrostatic discharge, proper gloves, finger cots, or grounding bracelets should be used. Observe the standard procedures for handling equipment containing electrostatic sensitive devices or assemblies in accordance with the recommendations and procedures set forth in the maintenance instructions set forth by the equipment manufacturers.
12-3.–12-7. [RESERVED.]
Par 12-8 Page 12-2 SECTION 2. GROUND OPERATIONAL CHECKS FOR AVIONICS EQUIPMENT (ELECTRICAL)
12-8. GENERAL. When the operating or airworthiness regulations require a system to perform its intended function, the use of the Technical Standard Order (TSO) equipment or the submission of data substantiating the equipment performance is strongly recommended. An operation check of avionics is the responsibility of the pilot in command. However, it is recommended that after replacement of equipment during 100-hour or annual inspections, an operational check of avionics equipment be performed. The accomplishments of these checks must be done in accordance with the recommendations and procedures set forth in the aircraft’s flight manual instructions published by the avionics equipment manufacturers.
12-9. INSPECTION OF AVIONICS SYSTEMS.
a. The inspection shall include the following:
(1) Inspect the condition and security of equipment including the proper security of wiring bundles.
(2) Check for indications of overheating of the equipment and associated wiring.
(3) Check for poor electrical bonding. The bonding requirements are specified by equipment manufacturers. Installation cabling should be kept as short as possible, except for antenna cables which are usually precut or have a specific length called out at installation. Proper bonding on the order of 0.003 ohms is very important to the performance of avionics equipment.
(4) Check to assure that the radios and instruments are secured to the instrument panel.
(5) Check that all avionics are free of dust, dirt, lint, or any other airborne contaminates.
If there is a forced air cooling system, it must be inspected for proper operation. Equipment ventilation openings must not be obstructed.
(6) Check the microphone headset plugs and connectors and all switches and controls for condition and operation. Check all avionics instruments for placards. Check lighting, annunciator lights, and cockpit interphone for proper operation.
(7) The circuit breaker panel must be inspected for the presence of placarding for each circuit breaker installed.
(8) Check the electrical circuit switches, especially the spring-load type for proper operation. An internal failure in this type of switch may allow the switch to remain closed even though the toggle or button returns to the OFF position. During inspection, attention must be given to the possibility that improper switch substitution may have been made.
Par 12-9 Page 12-3
b. Inspect antennas for:
(1) Broken or missing antenna insulators,
(2) Lead through insulators,
(3) Springs,
(4) Safety wires,
(5) Cracked antenna housing,
(6) Missing or poor sealant at base of antenna,
(7) Correct installation,
(8) Signs of corrosion,
(9) The condition of paint/bonding and grounding, and
(10) Check the bonding of each antenna from mounting base to the aircraft skin.
Tolerance: .1 ohm, maximum.
(a) Test equipment:
1. 1502B Metallic Time Domain Reflectometer or equivalent.
2. Thruline Wattmeter.
(b) Perform the antenna evaluation check using the domain reflectometer to determine the condition of the antenna and coax cables. Refer to manufacturer’s maintenance procedures.
(c) Use Thruline wattmeter as needed for addition evaluation. Refer to manufacturer’s maintenance procedures. Check for the following:
1. Resistance.
2. Shorts.
3. Opens.
c. Inspect the static dischargers/wicks for:
(1) Physical security of mounting attachments, wear or abrasion of wicks, missing wicks, etc.;
(2) Assurance that 1 inch of the inner braid of flexible vinyl cover wicks extends beyond the vinyl covering;