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...


Equipment Maintenance



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 and even proper handling techniques. In addition, Advisory Circular 43.13-1B provides a wealth of data that manufacturers may not include, for example something as simple as defining different types of inspections.

A Visual check generally needs no explanation as most in the industry realize this will involve looking at the physical condition of the components and checking for any defects such as corrosion, tightness of attaching hardware, and proper safety. Also included, but often overlooked, is the identification of placards. Placards regarding system operation or component description that are worn or missing should be renewed or replaced.

An Operational test should always be carried out after specific system maintenance or component removal. A qualified technician should always carry this out — one who is familiar with proper system/component operation and who can recognize any peculiarity. The data used for operational tests is available in most cases from the aircraft Flight or Operating Manuals. Some operational tests may require the aircraft to be in an "In-Flight" environment and can require either jacking the aircraft or somehow "fooling" the ground/flight sensing system. There are also situations where temperature change may have an effect on operation. In an environmentally-conscious society, it is no longer acceptable to spray Freon at a component to reduce temperature. There are several atmosphere-friendly materials that can be used such as carbon dioxide and of course, where possible, a bag full of ice cubes. A heat gun or sometimes a hair dryer can be used. The effects of excess heat or cold should always be considered prior to the application and proper safety measures should be implemented.

Functional tests are often confused with Operational tests but by definition have a significant difference. A Functional test, like an Operational test, should always be performed by a qualified technician. Unlike an Operational test, a Functional test is conducted to verify the calibration and accuracy of the system or device. Frequently, test equipment and manufacturers' technical procedures are needed — an example of this would be an Altimeter or Transponder check.

The Bench test is used only after a component has been removed from the aircraft. This is necessary after a component fault has been recognized and adjustment or repair is required. Frequently after a Bench check, either a Functional or Operational test should be conducted after component reinstallation.

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Interference tests are another consideration with any electric or electronic equipment installation. All mechanical and electrical connections should be checked for proper installation in accordance with manufacturer recommendations. Another consideration is the temperature rating of the wire insulation in different areas of the aircraft. Worst case situations should always be evaluated. Testing of equipment should be conducted using the aircraft's power generating system and with all associated electrically operated equipment and systems operating unless otherwise specified. With the component/system under evaluation operating, activate other equipment one system at a time to verify no significant radiated or induced interference occurs. Reasonable combinations of control settings and modes of operation should be evaluated. For communication and navigation equipment testing should be accomplished using at least one frequency selection in a high, mid, and low frequency band. It is often advantageous to make note of certain system combinations that should be observed during a dedicated non-revenue test flight. Electromagnetic incompatibility may result from design characteristics of previously installed equipment.

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