The Life-and-Death Significance of Wiring Maintenance
Aircraft wiring is just as important as airframes, engines, and avionics. The consequence of aircraft wiring failure can literally be the death of all onboard.
Unfortunately, unlike an airplane’s single airframe or one to four engines, there is a lot of wiring to be inspected and maintained during an aircraft’s life span. A case in point: According to Boeing, there are about 42 miles of wire on its 737-600/700/800/-900ER (Extended Range) models. If you find this factoid daunting, take heart! That’s four miles less of wiring that can be found on Boeing 737-300/400/500 models.
The 737 isn’t the only aircraft that has miles of wire. This level of wiring is common on all modern aircraft, simply because so many airplane systems are either electrically controlled, or interact with electrical instruments to display sensor data in the cockpit.
Current aircraft wire bundles are generally protected in line with the exposure they receive to heat, vibration and other potentially damaging influences during flight.
The most rugged wiring is found in high heat areas such as the engines. “For the harshest environments, we manufacture a metal convoluted conduit design that provides the necessary protection from extreme heat,” said Sam Symonds. He is president and CEO of Co-Operative Industries Aerospace & Defense, a manufacturer and repair facility of aircraft wiring products. “This conduit or bent tube design, coupled with a compatible hermetic connector design, serve to protect against the most severe conditions,” Symonds continued. “For less extreme temperature, but still high vibration areas, a less rigid type design is utilized to react more fluidly with the environment. For forward turbine engine sections where chaffing and fluid intrusion is a concern, a double braided design is incorporated to protect from fluid wicking, EMI and abrasion.”
“Connector platings can greatly increase resistance to corrosion in harsh environments,” added Bob Gannon. He is a design engineer with Harco, a designer/manufacturer of electrical cable assemblies. For instance, “500 hour or 1000 hour salt spray resistance prolongs the flying hours of connectors,” Gannon said. “Inside the cable assembly, Harco has engaged in improvements such as the sealing of cable entry points into the connector and backshell. Thorough experimentation with epoxies to match thermal expansion of connectors has yielded improvements in prevention of movement of corrosive water and salt spray into the areas where cables are joined to connectors.”
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