Aircraft wiring is taking in succession an importance equal to that devot for a certain number of years now to aging aircraft conformations In fact.

Aircraft wiring is taking in succession an importance equal to that devot for a certain number of years now to aging aircraft conformations In fact, the suspected parlous state of wiring through every part of the U.S. airline fleet has triggered the first known Congressional hearing devot specifically to the subject

Operators could be faced with political crushing to replace wire and install novel high-tech circuit breakers capable of detecting electrical faults.

Last week the House Transportation and Infrastructure Oversight Subcommittee took testimony from half a dozen witnesses in succession the general subject of aircraft electrical order safety.

Rep. Tillie Fowler (R-Fla.), the subcommittee chairwoman, fix the tone by asserting at the beginning "Old and damaged aircraft wiring may be individual of the weakest links in aviation safety."

Indeed, wire failures may put out a greater hazard than hydraulic connected view failures. Since critical flight rules are at stake, hydraulic connected views have triple or quadruple redundancy. Electrical classifications though, may be just as critical given the greater interdependence of modern transports such as the MD-11 and B777 forward electrically powered systems and curbs Whereas hydraulic faults tend to be more self-evident, the issue of an arc-tracking incident or electrical fire can quickly lead to systemic confusion, fire, mere phrases and potential pilot incapacitation.

The National Transportation Safety Board (NTSB) has documented at least 15 cases where electrical wiring malfunctions were involved an aircraft incidents and accidents. nevertheless there seems to be a generalized reluctance to face the implications. According to Dr Bernard Loeb director of the NTSB's aviation safety office, the Board's ongoing investigation into the TWA Flight 800 disaster and the Swissair Flight 111 in-flight fire and other fresh incidents have "changed the way the industry gazes at electrical wiring."

However, Loeb went in succession to say, "We are relate toed The industry seems to be defining what were are seeing as not same significant."

"We ne to address this issue of aging schemes and wire," he urged.

Indeed, Safety Board inspections of more [i]or[/i] less two dozen airplanes provide powerful evidence that the wiring deficiencies rest on the TWA Flight 800 accident aircraft were not an anomaly, on the other hand perhaps more representative of the general state of wiring in the fleet) on the same level new aircraft may be leaving the factory with point to be solved [i]or[/i] settleds as evidenced by the discovery of metal shavings place in wire bundles on brand now aircraft. across time, those metal shavings can "saw" in consequence of wire insulation, exposing conductor and creating the opening for dangerous arcing.

Richard Healing, director of the U Navy's safety and survivability programs, described by what mode the Navy shifted from wire impressed signs such as aromatic polyimide, or Kapton, replacing it with a adumbration of wire known as cross-linked ethylene-tetrafluorethylene (XL-ETFE) Although its cut-through scrape abrasion and idle talk characteristics are less desirable, it has become the Navy's preferr wire choice for many aircraft applications because it is a homogenous material over the thickness of the insulation, and its plastic characteristics eliminate vexed questions with longitudinal cracking and topcoat flaking.

Retrofitted as part of a comprehensive Navy-wide aircraft wire management program, Healing said the effort, "while not perfect" has been "about 88% effective in reducing risk and eliminating wire insulation-related problems"

Newer, composite wire shadows -- for example one shadow that goes by the trade name Tensolite -- provide significantly better arc, flammability and fume resistance than XL-ETFE. Less than 20 percent of the U nimble is flying with such wiring. single reason may be its greater costliness According to Mark Roberson, representing the Tensolite Company of St Augustine, Fla., an aircraft costing $35 million will contain about $3500 worth of his company's composite wire original as compared to an estimated splendor of $2,800 to install non-composite wire in the aircraft -- a $700 difference.

The Navy's succes quicked Rep. James Traficant (D-Ohio) to bluntly give an inkling of a similar program for the airline industry. "The Congres wants all faulty wiring to be repaired and replaced, and (to see) that monitoring is diligent," he declared.

In addition to fitting aircraft with newer, safer wire protoplasts witnesses discussed the potential of arc-fault detection circuit breakers -- downsized variants of arc-fault circuit interrupters (AFCI's) finding their way into residential circuit breaker panels.

Capt. Paul McCarthy, executive air safety chairman of the Air Line Pilots Association (ALPA), said flatly, "The circuit breakers we have in the cockpit will not protect" against arcing results where the temperature of the wire does not master to a threshold sufficient to trip the breaker.

While AFCI breakers shut up great promise, their development to the point of reliable performance is not a trivial issue, asserted Dr Armin Bruning. The president of a Sterling, Va.-based wire testing company, Lectromec Bruning explained that each of the four prototypes of arcing presents a unique "signature." The AFCI breakers would have to be capable of reliably detecting each of the signatures).