Equipment Maintenance

Equipment Maintenance By Jim Sparks May 2000 Manufacturers of aircraft and of avionics equipment generally provide guidance to assist in keeping their equipment operating properly. This may include information for functional tests, bench tests...

Unfortunately, the facility installing a new system is usually responsible for resolving any conflicts which develop with the addition of equipment.

Ground Electro Magnetic Induction (EMI) testing has been found adequate for installation of similar types of equipment. Devices such as wireless telephones or any device that transmits radio frequencies will need to be tested to verify lack of interference with other aircraft systems. As an example, during the initial installation and certification of a High Frequency (HF) communication radio on a business jet using an Electronic Engine Control (EEC), it was noted that anytime the microphone was keyed for transmission purposes both engines would FLAME OUT — obviously not a condition conducive to safe flight. The engineers were then forced back to the drawing board to determine where the HF signal was being induced and then to decide whether to filter the transmission or shield against the reception.

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Handing procedures and techniques
Electronic equipment manufacturers frequently publish "Handling" Procedures or Techniques for their specific equipment. Any component containing electronic devices such as diodes, transistors, or integrated circuits should be protected from Electro-Static Discharge (ESD). For example, Intertechnique, an electronic equipment manufacturer for numerous aircraft, provides a list of "General Handling Rules." These include:

1. Avoid having non-conductive items such as trays, bags, packaging material, drawings, or personal effects that are not essential for the work at hand within the immediate area of the component.
2. Only use appropriate gloves or finger protection when handling Electro- Static Sensitive Devices (ESSDs).
3. Prior to removing any component from a conductive package, the technician should first touch the package. This also applies to re-packing the device. Care should also be taken to insure that the electrical terminals on the device do not come in contact with any plastic or paper outer containers.
4 . If it is necessary to place an electronic component on a conductive workbench without a protective cover on its terminals, it should always be done with the terminals in contact with the conductive surface.
5. Technicians are reminded that ESSDs can be destroyed by only momentary contact with any non-conducting or ungrounded object and that the damage is inflicted at the moment of contact.
6. Technicians should also be aware that the use of conductive surfaces in Special Handling Areas (Static Free Rooms) departs from the normal procedure of electrically insulated work surfaces and appropriate care should be taken so that unauthorized electrical equipment is not used in the proximity of the work area.
7. Protect removed components against Electro-Static Discharge. 8. When soldering, heat should be confined as much as possible to a limited area. This can be done by using temperature-controlled soldering irons and heat sinks.

Suitable test equipment is essential to safe maintenance of airborne avionics systems and it is up to the certificated technician to make sure the test equipment calibration standards are met and traceable. In the United States, for example, the standards are from the National Institute of Standards and Technology (NIST) or an established test equipment manufacturer. In all cases, test equipment used must meet with the approval of the FAA if the test is used to satisfy an Airworthiness Requirement. It is also up to the technician to verify that the test equipment is capable of performing all parameters of the required test and that the level of accuracy is sufficient. Frequently, airframe and avionics system manufacturers will provide a list of recommended test equipment for accomplishment of different tasks.

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