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Apr
23
2015
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Posted 9 years 250 days ago ago by Scott Skola
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April’s tips:
ATA 53
Airbus EC135 series: Avionics Deck vent openings in fuselage side panels. Much to a mechanic’s displeasure, this simple venting system has been the root of many electrical issues. Main problem is when water applied with force (e.g. hose while washing aircraft, etc.) at either vent grill will allow plenty of water to cover components on the avionics deck and even the master electrical boxes. One fix adopted by numerous operators is to fabricate and install a simple “hat” or deflector to the interior top section of the fiberglass vent tubes. The deflector should be mounted above vent tube edge on tabs, and designed to channel any water to the interior surface of the fuselage side panel. This will allow hot air to vent while directing the water toward the lower floor tunnel drains via the side panels. It’s not 100% corrective, but coupled with additional training to avoid these vent areas during aircraft washing keeps the issues to a minimum.
FYI: There is another method which involves fabricating external covers for the vent grills. However, I’ve heard they tend to joyride with the aircraft on occasion unless they’re tethered to the sloppy link in the right front seat. [Submitted by RW]
ATA 24
Airbus EC135 Series: Speaking of water infiltration…sometimes it finds its way into the aircraft Master Electrical Boxes. Water can come from either the vent tubes mentioned above, unsealed FADEC harness panel on engine deck, condensation issues, or simply magic! But not to fear. For those who remember the infamous AS355 Twin Star and their dual electrical boxes, the EC135 system is just the latest and greatest design, right down to the “Z” cards. And thankfully they are now made with a robust metal box instead of the old “Tupperware” containers whose lids didn’t fit. But I digress. Anytime unusual electrical problems pop up that normal methods can’t isolate, check both master electrical boxes for signs of moisture. Be sure to look at both boxes as they now contain microchips that monitor each other. With aircraft power OFF, disconnect the aircraft battery, and remove the cover panels on the electrical box. There will be five “Z” cards inside to include one that is a double-stacker. Each one slides out with a little persuasion. Check for signs of moisture or traces of corrosion. If excessive water is noted the interior of the boxes can be dried with a fan or heat gun. Use a pencil eraser to clean the card connection bar if needed. Once dry, reinstall cards, reconnect aircraft battery, and perform your standard smoke check. [Submitted by RW]
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About the author: After a 32 year career in maintaining helicopters, Scott provides limited maintenance consulting services through his company, TEK Aviation LLC. He can be contacted at
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