AVIONICS
accomplished by connecting all personnel and the ESDS part and the mounting unit for the ESDS part to the same electrical ground source. Before handling an ESDS part, the technician must connect a grounding strap to his or her bare skin and ensure that it is fi rmly in place. A test is then conducted to see that the resistance reading of the technician through the grounding strap is below a particular value. A wrist strap with a fl exible wire is most commonly used for this purpose. Prior to removing any ESDS part from the aircraft, ensure that the mounting unit that the ESDS part is in and the
Grounding Wrist Strap
technician’s grounding strap are connected to the aircraft’s common ground point. The removed part should be placed in an approved antistatic bag or container immediately and the antistatic bag/container MUST be sealed/closed. An ESDS label should be affi xed to the bag/container. When installing an ESDS part in the aircraft, the same conditions apply. The ESDS part should be brought to the aircraft in a closed/sealed approved antistatic bag/container. Prior to removing the part from the antistatic bag/container, the technician MUST ensure that their grounding strap and the unit the ESDS part will be installed in are both connected to the aircraft’s common ground point. Upon removing the ESDS part from the antistatic bag/container, it should be seated in its mounting unit immediately. It should not be placed on the fl oor, aircraft seat or anywhere else. If the ESDS part is going to be taken to a workstation or shipping area, then the area where it will be looked at should also be an EPA. All the same rules apply for handling the ESDS part as were applicable on the aircraft. Additionally, there should be signs easily seen and tape placed along the fl oor reminding people that they are about to enter an EPA and need to take appropriate precautions.
Types of Static Damage Damage from static discharge is usually described as hard and soft failures. A hard failure caused by a static discharge event creates an immediate system failure. A soft failure caused by a static discharge event may only injure the ESDS part and cause unreliable operation and/or shorten the life of the overall system. Sometimes a part that has experienced a soft failure is said to be wounded. These parts will often pass bench and prefl ight tests and still fail in fl ight. In closing, all aircraft maintenance professionals who work with and around ESDS parts need to be aware of what static electricity can do to these parts. Be proactive in helping take the precautions required to eliminate the risk that static electricity poses to them.
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HelicopterMaintenanceMagazine.com April | May 2014
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