Wiring Inspections Are Money-Making Opportunity

Most repair station operators have to agree that it would be nice to find a few extra thousand dollars of workorders regularly. Yet, according to a discussion held at the Aircraft Electronics Association (AEA) regional meeting last October, most repair stations are leaving several thousand dollars worth of necessary work unfulfilled. During a meeting entitled "Wiring Inspections," Ric Peri, AEA vice president of government and industry affairs, presented results from the Aging Transport Systems Rulemaking Advisory Committee (ATSRAC) Harmonization Working Group 10 (HWG-10) that illustrated the lost business opportunity.

Thirty-nine small transport category aircraft of eight different models were inspected by HWG-10 members as they were made available during normal maintenance cycles. From these 39 aircraft, individual findings were checked against OEM standards and industry practices. These checks revealed 2,281 individual discrepancies. While none of the discrepancies were considered safety of flight concerns, 73 of them were categorized as significant items and all were items needing correction under a zero- tolerance system.

Discrepancies were found in the areas of installation (85 percent), wiring conditions (11 percent), and connectors and terminations (less than 5 percent).

The majority of discrepancies involved the following:

• Excessive lint, dust, and dirt accumulation.
• Inappropriate repairs.
• Inappropriate wire routing.
• Inappropriate clamping and wiring support.

While most of the installations appeared clean upon initial inspection, when wiring bundles were disassembled they often had metal shavings caught between wires. These shavings, by-products from equipment installations or aircraft completions, caused chafing of the wires. In some cases the wiring insulation was completely worn through. Various fluids had also seeped onto wiring. The fluids should have either been cleaned off or the wiring should have been replaced.

Inappropriate repairs or installations included inadequate clearance to the structure, inadequate bend radius of wire bundles, improper clamp size, excessive slack or sag between clamps, and inappropriate splice distances.

�Findings by HWG-10 members did not support that age of the wiring is the sole factor in discrepancies. However, wiring age combined with other factors such as poor or inappropriate maintenance practices will increase discrepancies due to degradation effects. These factors tend to increase over the life span of the aircraft as more maintenance and repairs are performed.

Meeting participants voiced concerns that often it is difficult to persuade owner/operators to spend additional money on what appears to be minor work. That argument faded with Peri's emphasis on the fact that OEMs universally hold a position of zero-tolerance for discrepancies in wiring condition.

In areas that an OEM manual may not cover, it was recommended that the criteria for wiring inspections from Advisory Circular 43.13-1B be used. Although AC43.13-1B states it is for "...inspection and repair of nonpressurized aircraft..." it was agreed that no other standard for pressurized aircraft has been published and that a wiring inspection would not be prescribed that fell below the criteria set forth in the advisory circular.

The customer may have reservations about the additional work being done during the next scheduled inspection or maintenance. However, zero tolerance is a persuasive argument. That, plus the increased electrical system safety and reliability should help to put things in perspective. Additionally, most customers will be more satisfied knowing that they have an improved aircraft that should need fewer related work orders in the future.

Before the start of the meeting, the general feeling was that there was going to be some new technical process introduced that would make wiring inspections easier or more automated. What transpired instead was a sort of call to arms for technicians to get back to the basics and pay renewed attention to performing work to the industry standards already in place.

AC43.13-1B, Chapter 11 outlines pretty well the details of aircraft electrical system inspection criteria. The following caution is mentioned, which is worth pointing out: "For personal safety, and to avoid the possibility of fire, turn off all electrical power prior to starting an inspection..."

Many technicians will get a chuckle out of that, but many have also seen someone take a jolt, burn out a system, or worse.

The bulk of the text from Chapter 11 will not be included here, for brevity. Besides, there is certainly already a copy somewhere nearby. Take another look at its entirety, with particular attention paid to all that is said about inspection. It's comprehensive, like your inspections should be. You are urged by the following statement excerpted from Section 11-1: "Damaged wiring or equipment in an aircraft, regardless of how minor it may appear to be, cannot be tolerated."

How many work orders will you find just lying around in your shop?

The full text of HWG-10 may be found at www.mitrecaasd.org/atsrac-/final_reports/2003-01-Task10_Final_Report.pdf