Preventive Maintenance

For those not well versed in the art of aircraft repair, words of caution: lack of knowledge may end up costing more in the long run.


Doing things before problems occur in an effort to prevent inopportune failures? What a concept! The term “preventive maintenance” does have an official definition as well as implications assigned by the United States Federal Aviation Administration.

So just what does it mean? According to the Administrator: “Preventive maintenance means simple or minor preservation operations and the replacement of small standard parts not involving complex assembly operations.” This definition has been tweaked a bit to enable pilots to perform certain functions on their aircraft and the guidelines are presented in Federal Aviation Regulation (FAR) 43.3.

Privileges for pilots include tasks such as troubleshooting and repairing landing light wiring circuits but do not include position and panel lights or similar systems that may be more complex. For those not well versed in the art of aircraft repair, words of caution: lack of knowledge may end up costing more in the long run.

Replacing and servicing batteries

Replacing and servicing batteries is another area where frequent attention can prevent missed trips and is suitable for pilots to accomplish. When replacing any aircraft’s battery, use only one approved for that make and model; plus preventive maintenance does include adding water and top charging. If corrosion is noted on the terminals or in the battery box area, a baking soda solution works well in aircraft equipped with lead acid batteries. This should be followed by a complete flush with fresh water so no trace of the baking soda remains.

Emergency locator transmitter battery replacement is also permitted provided manufacturer’s recommendations are followed. The new expiration date for replacement (or recharging) must be legibly marked on the outside of the transmitter and entered in the aircraft maintenance record.

Navigation units frequently contain internal batteries requiring replacement. In certain cases such as with a portable global position sensor (GPS) change out is most often not a complicated process. Many of these devices are manufactured with substances considered hazardous which will impact acceptable means of disposal. In other systems such as onboard flight management system (FMS) computers, internal batteries are used to assist in the shutdown process in the event aircraft electrical power is turned off prior to complete system termination.

Unfortunately devices such as this are not well advertised and their replacement only becomes realized when a malfunction occurs generally in the start-up process just prior to an important trip. It is worth conversing with the FMS manufacturer and determine if an internal battery is used as well as recommended replacement intervals. In some cases these batteries are not field replaceable or may require an alternate power source be applied during the change. A thorough inquiry should be made prior to attempting replacement.

Navigation systems

Pilots are also authorized to remove and replace self-contained, front instrument panel-mounted navigation and communication devices, provided they employ tray-mounted connectors secured in the rack. This does exclude automatic flight control system components, transponders, and distance measuring equipment (DME). The approved unit must be designed to be readily removed and replaced and pertinent instructions must be provided. Prior to the unit’s intended use, an operational check must be performed in accordance with maintenance instructions and where pertinent, the applicable sections of the FARs. Systems such as the auto pilot often involve complex testing to validate airworthiness and if full functionality is not achieved, operation of the aircraft in certain airspace may be impacted. This is particularly true of air data and auto pilot systems when operating in reduced vertical separation minimums (RVSM) regions.

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