Texas Instruments announced the development of an Arc Fault Circuit Breaker for aircraft applications. These are similar to the household AFCIs in background. However for aircraft work the skin of the aircraft forms the return path for the current for many of the circuits. Some aircraft circuits are DC and some are AC and the arc detection methods are different for the two type of power. The packaging constraints and form factor are different for aircraft service. EMI and RFI immunity are important for aircraft breakers and are not addressed in the residential breakers. Texas Instruments announces the development of an Arc Fault Circuit Breaker for aircraft applications. http://www.ti.com/mc/docs/precprod/docs/feature.htm
Aircraft AFCIs continue to be a problem. As recent as April 2002 ONR announced a Broad Agency Anouncement (BAA) that requested proposals for research in the area of aircraft AFCIs. http://www.onr.navy.mil/02/baa/expired/02_013.htm. This is lengthy request for proposals.
There is a 2001 FAA briefing on aircraft AFCIs at http://av-info.faa.gov/dst/LAsep01/c2-02-Portwood.pdf. One of their reports can be found at http://www.tc.faa.gov/its/cmd/visitors/data/AAR-430/aanon str.pdf.
Eaton Aerospace has a line on aircraft AFCIs and their web site includes a video showing small arcing faults. http://www.aerospace.eaton.com/products /power_load_subsystems/afci_technology.html
Eaton announced their first successful flight tests of AFCIs in September 2001, http://www.aerospace.eaton.com/news.asp ?NewsCommand=ViewArticle&ArticleId=1100.
For a report on the results of the NAVAIR’s first tests of AFCIs go to http://www.iasa.com.au/folders/Publications/pdf_libr ary/gazettemv.pdf.
One of the major problems of aircraft arcing fault seems to
be related to the use of Kapton insulation on wiring. “EVEALED: WHY JETS FALL FROM THE SKY”
By Tom Mangold and Tim Clark of THE FAIRFAX NEWSPAPER GROUP extensively discussed Kapton wiring in July 1999. A copy of the article can be found at http://www.vision.net.au/~apaterson/aviation/kapton_mangol d.htm.
International Aero Inc., has invested in a new state of the art fire test facility called the IAI Fire Suppression Laboratory. The testing of AFCIs is one component of their test capability. http://www.pyrogen.com/IAIfireLab.htm
A paper on “Risk Assessment for Aircraft Electrical Interconnect Subsystems” can be found at http://www.adventengineering.com/Publications/ICWSA2002_C.pd f
Case Histories:
UPDATE ON NTSB INVESTIGATION OF AIRTRAN
EMERGENCY LANDING IN GREENSBORO, NC
Washington DC: 9/12/2000 –
On Tuesday, August 8, AirTran flight 913 returned to Greensboro, NC shortly after takeoff when crew members reported smoke in the cockpit. The National Transportation Safety Board sent a 5-member team of investigators to the Piedmont Triad Airport to conduct the investigation.
Eight investigative groups were organized, including Operations, Aircraft Systems, Survival Factors, Fire, Maintenance Records, Air Traffic Control and Flight Recorders (Cockpit Voice Recorder and Flight Data Recorder). Parties to the investigation include the Federal Aviation Administration, Association of Flight Attendants, Boeing (McDonnell Douglas), Leach International, and AirTran. The investigation has so far developed the following information:
The Operations and Survival Factors groups interviewed both flight and cabin crewmembers. The Survival Factors group will also be reviewing interviews with Airport Fire and Rescue personnel. According to information from the crew interviews, the Captain and First Officer smelled smoke shortly after takeoff. The crew immediately donned oxygen masks and goggles. The crew reported that the smoke became very dense and restricted their ability to see the cockpit instruments, the visual references outside the airplane, and even each other. The cabin crew also smelled smoke, then saw smoke and sparks in the area of the forward flight attendant's jumpseat. One flight attendant entered the cockpit momentarily and was instructed to
prepare the cabin for an emergency landing. The flightcrew was able to identify the airport and make a successful emergency landing. The airplane was immediately stopped and an emergency evacuation was conducted on a taxiway.
The Aircraft Systems and Fire Groups worked jointly to document fire and heat damage. They have noted extensive wire and insulation heat damage and smoke damage and determined that the heat was sufficient to blister the primer on the fuselage crown skin. Initial examination of the electrical panel that sustained the heat and fire damage indicated that the fire likely originated in the electrical panel. There is no evidence of fire, smoke or heat damage below the mounted location of the relay. The group has removed 5 electrical relays from the panel and examined them at the manufacturer's facility. The examination revealed evidence of arcing in the relay for the left heat exchanger.
The Maintenance Records Group has secured records for the aircraft from the AirTran facility in Orlando, FL, and will be reviewing the records to determine evidence of electrical system anomalies. The maintenance records investigation will also include examination of several Service Bulletins issued for certain relays within the DC-9 to determine their applicability in this incident. Further, Boeing is conducting a search of its databases to identify electrical system events in the DC-9 and MD-80 series airplanes that have resulted in smoke and fire.
Copies of the air traffic control tape and a preliminary transcript have been provided to the Safety Board by the FAA. The examination of both the FDR and CVR revealed they functioned adequately and recorded event information.
An archive of press releases is available at http://www.ntsb.gov/pressrel/pressrel.htm.
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