Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Sandia preemptive spark helps find intermittent electrical short circuits in airplanes

21.06.2006
Finding a short circuit before it finds you
A preemptive spark lasting for nanoseconds that helps find potentially dangerous short circuits hidden in the miles of wiring behind the panels of aging commercial airliners has been patented by Sandia National Laboratories.

The rapid technique may make it financially feasible for airlines to quickly diagnose and repair the hard-to-locate intermittent faults that have plagued the industry and cost millions of dollars in lost revenue due to aircraft downtime.

The product, called PASD (Pulsed Arrested Spark Discharge) is expected to be marketed by September by licensee Astronics Advanced Electronic Systems of Redmond, Wash., and combined with that company's other patented test methods under the name ArcSafe.

Other possible uses eventually envisioned for PASD are as inexpensive tests for the wiring harnesses of passenger cars and new homes. Military tanks and the hard-to-reach wiring behind the steel bulkheads of submarines are also possible candidates.

The commercial product is about the size of a small suitcase. It can be plugged into aircraft-installed wire harnesses, 40 wires at a time, to check for the very small insulation breaks associated with intermittent faults.

Sandia is a National Nuclear Security Administration laboratory.

Detecting intermittent faults before they scuttle a plane

The challenge to engineers has been how to locate an intermittent wiring fault before - not after - it becomes a problem.

Intermittent electrical short circuits in aging commercial airliners range from the trivial to the deadly. They can make cabin lights blink, air conditioning falter, or even cause fatal crashes, as with flights SwissAir 111 or TWA 800.

PASD's trick is to make the short circuit manifest before it normally would and to do so on the ground so that technicians can fix it. To achieve this, the Sandia method sends a nanosecond pulse of electricity, fiercely propelled by a high voltage, along airplane wiring bundles. The tiny pulse is powerfully driven so that it can jump gaps in slightly frayed insulation but has so little energy that it is harmless.

Energy like a trickle over a high waterfall

The process resembles sending a brief trickle of water over a high waterfall. The fluid will certainly fall a long ways very fast, but the tiny amount arriving at the bottom isn't enough to do damage.

Because the voltage is higher than that normally used in airplanes, the electrical pulse will jump like a rabbit from the smallest wiring insulation fault (which to ordinary instrumentation seems undamaged) either to the bulkhead or to another nearby damaged wire. That spark - like static electricity leaping from hand to doorknob - in effect lights up the invisibly damaged spot like a tracer bullet at night lights up a target. The amount of time it takes for the current to return to its source is analyzed by the automated test-set to tell within inches how far the break is from the test entry point.

"Rather than reacting to a problem, these systems can find a fault before it manifests into a catastrophic event," says Sandia team leader Larry Schneider. "Rather than ripping apart the fuselage for access to a faulty harness that may run the length of the plane, airline mechanics will be able to use this new tool to efficiently locate and repair the intermittent fault."

Faults the size of a pinhole, or invisible as a slice from a razor

Sporadic short circuits occur where two exposed conductors, or a conductor and aircraft frame, make temporary contact during flight. Vibrations caused by turbulence may cause wires to touch, interrupting power to sensitive electronics and possibly damaging wires. These conditions are tricky to diagnose when the aircraft is stationary (on the ground) because the shorting wires often have shifted back to a non-shorted state. Sometimes these breaks can barely be seen by the naked eye because missing insulation may be the size of a pinhole, or nearly invisible like a fine cut from a razor blade. Traditional wire-test systems have great difficulty finding these faults.

To overcome myriad problems initially besetting the promising technique, the National Nuclear Security Administration and the U.S. Navy supported the research, followed by the Federal Aviation Administration, to the tune of about $2 million. It took two years for Astronics to adapt it to its suite of tools, which were developed over four years of research to locate wire breaches with the potential for electrical shorting.

Says Astronics team leader Mike Ballas, "We really value PASD technology. We licensed it, turned it into a practical portable test unit targeted for the aviation industry to find intermittent faults, and we believe it's the best way now to do the job. It's a nice complement to our patented technology."

Says Robert Pappas, Federal Aviation Agency project manager for aging aircraft research and the first to recognize the value of Sandia's original research proposal in 1998, "It would have been unfortunate if PASD had been developed and then remained stuck in a lab. Integration of the technique [with those of Astronics' ArcSafe] is a real success story."

There'll be problems, just the same, in getting the method accepted, says Mike Walz, current FAA overseer of the project. For one thing, he says, "What PASD looks like is an electrostatic discharge [ESD] - something aircraft manufacturers work hard to keep out of their wiring system."

One researcher responds with humor, "[In that respect,] PASD is a little like homeopathy: Uncontrolled ESD can kill you, but a little bit can help cure you." In electronics, at least, the theory seems to work.

More technical information

Astronics welcomed the addition of PASD because of other problems involving the varying resistance of wires over long distances, called electrical impedance, particularly in the branched wiring systems prevalent in aircraft. This was a problem for earlier versions of ArcSafe, which used a DC current to detect breaks. Varying impedance meant it was difficult to accurately locate an intermittent fault, since electrical return signals were inconsistent, especially on complex wire geometries. Still, the DC method is most effective for identifying ordinary faults and Astronics retained it for quick fault screening.

Rider on a horse

To enhance its fault-locating ability, Astronics developed a method that allows the PASD pulse to ride upon the DC current like a rider on a horse. The DC current provides support for the high-voltage pulse, which then can be effective even a hundred feet from its starting point in accurately locating critical breaches in wire insulators, even those occurring on branched wire-harnesses. The distance to a fault is computable, regardless of changes in impedance produced by the wiring as it reacts to the PASD pulse at various voltage levels.

"Wiring insulation grown defective over time can cause malfunctions or even fires, but is devilishly hard to spot and even harder [once spotted,] to [exactly] locate," says Schneider. "Other methods have faltered when confronted with the varying impedances of bundles of wires, or the difficulty of providing the exact location of the defect as wiring bundles branch into other bundles. This nondestructive, inexpensive method not only detects cracking or pinholes but also is able to pinpoint the defect's precise location to facilitate wire replacement."

The actual location of the defect may require checking out over several possible branches, since the same distance-to-short may exist along several paths, but the problem is minor compared with the alternative.

The hybridized system is an improvement because of its greater robustness on complex systems.

The technique probably would be best used to check those wiring subsystems that are known problem areas, says Larry. To check all the wiring in a plane might take several days.

Sandia pulsed power

PASD relies on a Sandia specialty called pulsed power, developed over decades of research. Usually the public thinks of this research - if it thinks of it at all - in terms of Sandia's massive Z machine, which sends great bursts of electrical current down conduits as big around as a horse's girth. But the PASD device in its experimental state was only the size of a small refrigerator.

Neal Singer | EurekAlert!
Further information:
http://www.sandia.gov

More articles from Power and Electrical Engineering:

nachricht Did you know that the wrapping of Easter eggs benefits from specialty light sources?
13.04.2017 | Heraeus Noblelight GmbH

nachricht To e-, or not to e-, the question for the exotic 'Si-III' phase of silicon
05.04.2017 | Carnegie Institution for Science

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Fighting drug resistant tuberculosis – InfectoGnostics meets MYCO-NET² partners in Peru

28.04.2017 | Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

 
Latest News

Wireless power can drive tiny electronic devices in the GI tract

28.04.2017 | Medical Engineering

Ice cave in Transylvania yields window into region's past

28.04.2017 | Earth Sciences

Nose2Brain – Better Therapy for Multiple Sclerosis

28.04.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>