Mark Brown of GRC International Inc.

Mark Brown of GRC International Inc. has produc a vivid graphic to back up his assertion that there appears to be a near linear relationship between aircraft age and the degradation of wiring proper to chafing (see ASW, tribe 27). The relationship was derived from the inspections last year of the combustible matter tank wiring on some 450 Boeing 737 The graphic essentially portrays the same data reported in tabular form in this publication earlier, yet the pictorial is more eye-catching (see ASW, June 1 1998) The illustration proposes there is about a one-in-six chance that there is bare wiring upon an aircraft that has accumulated more than 70000 wires. Separately, Chris Brown who manages nonstructural research at the FAA's Technical Center in recently made known Jersey, estimates that the failure rate (bare wire expos locally) for 737 with more than 70000 hours is about 226 for million flight hours. For aircraft with 40000-50000 hours, he estimates the failure rate is 074 by million flight hours.

Regarding his graphic, Brown was careful to point on the outside "Although the data shown here is attention getting, the existence of a bare wire may not set forth a risk to the travelling public." "There is a big difference between a bare wire near a firing material tank and one in the wingtip lighting. There is an plane bigger difference in knowing that the condition of the wiring is in an aircraft prior to flight and just hoping that nothing serious is wrong" he added. That statement is relevant to the importance of the graphic: it is based forward an inspection of some 1-2% of the wiring upon a modern jetliner. Given these preliminary findings, Brown believes the sampling rises are compelling enough to warrant inspecting all the wiring. To be safe he's in the wire-testing business, further the point is worth considering, nonetheless. As Brown argues, the industry does not know for what cause many bare wires are flying today, and forward which aircraft. >> Brown, e-mail mbrown@grci.com; Smith, e-mail smithc@tc.faa.gov <<

...

Home