Aging Aircraft Wiring: Fault prevention and detection issues

Joe Escobar
Created:

Let's face it, the average age of the nation's aircraft fleet is getting older. As we struggle to maintain these older aircraft, aging wiring issues come to the forefront of critical issues.


The 900 AST is the size of a typical digital multimeter. In addition to offering all of the functions of a digital multimeter, the 900 AST offers a time domain reflectometer (TDR) to identify the distance to an open circuit as well as a function called resistive fault locate (RFL) that calculates the distance to a short or ground.

The TDR on the 900 AST can examine single conductor wires with a reference wire, twisted pair cables, shielded wires, and coax cables.

While the TDR function of the unit works well with open circuits, it does not detect all faults or grounds. This is where the RFL function comes in. This function will display the distance to a fault or ground accurately. A color-coded ground on the screen shows the mechanic how to set up this test.

The 900 AST has the ability to store up to 200 TDR traces in its internal memory. Past traces can be recalled in order to compare it to a live trace. In addition, wire traces can be uploaded to a computer using a built-in infrared port.

ESP Meter

Eclypse International Corporation has launched its own fault location meter. Dubbed the ESP Meter, it can also locate faults in wiring. It uses Standing Wave Reflectometry to locate faults in wiring up to 1,000 feet. It can also store data and link to a PC for upload via a RS-232 data port. It is being deployed for operational evaluation with units at Marine Corps Air Station, Cherry Point, NC and Tinker AFB in Oklahoma.

The technology available to help us do our jobs is increasing each day. With these additional tools available, mechanics may be able to meet the demands that aging wiring poses to the safe operation of the aircraft we work on. AMT

Some Statistics

  • At least one "smoke in the cockpit" incident occurs every week on U.S. commercial planes.

  • Electrical arcing in the fuel probe system is suspected to have caused the loss of TWA 800 (7/96).

  • SR111 crash (9/98) was caused by in-flight fire resulting from electrical wire arcing in cockpit ceiling panel.

  • A large commercial transport with roughly 500,000 feet of wiring has 200-2000 insulation breaches.

  • 64 in-flight fires on Navy aircraft (7/95 to 12/97) -2.1 per month.

  • 80 to 90 percent preventable with AFCB.
Presentation by Texas Instruments at the 2003 Aging Aircraft Conference

Future of Fault Detection

There is a new technology being developed to help detect faults in wiring. Killdeer, ND - based Killdeer Manufacturing Company is developing a fiber-optic detection system that would help detect faults in both wiring and other applications such as hydraulic or fuel lines. The system is a passive system that uses fiber-optic cable encircling the item to be monitored. There is a light source at one end of the fiber and a monitoring system at the other end. A flaw in the wiring or tubing would cause damage to the fiber-optic wire, thereby causing detection at the monitoring side. The system is currently undergoing flight testing on a military test bed. This system could possibly be available as both an OEM application and as a retrofit system in the future.

Aging Aircraft Issues

For more on this topic check out the "Aging Aircraft Issues" presentation in AMT's Virtual IA Seminar series. Duncan Aviation's Pete Kilmartin discusses aging aircraft issues ' providing operators with knowledge about the challenges of maintaining older aircraft. The presentation includes a discussion of known problem areas, ideas for prevention, and a perspective on dealing with aging aircraft issues.

AMT's Virtual IA Seminar series is available at www.AMTonline.com.

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