MD11 Wiring Photos

Courtesy of Air Safety Week
Photos: Tim Van Beveren

The modulator box to the in-flight entertainment system (IFEN), installed in the cabin ceiling. The top bundle of multicolored wires is part of the entertainment system. The larger bundle below is original equipment. Starting at the right on the IFEN bundle, the metal bracket connecting it to the support member is not cushioned. Moving to the left along the bundle, note the inappropriate use of a hard plastic or metal spring, another potential source of abrasion. Moving further to the left, note that the white wire running straight along the bundle is not affixed under the plastic tie, as it should be.
Wire routed in the ceiling, close to the track guide for the upward-sliding forward right passenger door.  The flexible conduits route IFEN wiring forward to the cockpit. Conduits are vulnerable to abrasion at the ends; as shown here, self-vulcanizing tape was wrapped around the ends to minimize the potential for chafing. According to a U.S. military manual on wiring practices: "do not depend on ... sleeving of any type for protection against abrasion or chafing, or as s substitute for good routing practices."

  With respect to "good routing practices," wires can be seen going over a cushion clamp affixed to the vertical metal tube. If the clamp was too small to contain all the wires, the wire experts who examined the photo said a larger cushion clamp should have been used.

Wires connected to a power bus, the boxlike structure lower right. Note the mass of bundles running along the horizontal metal beam, with no evidence of cushioned grommets or clamps. At least every fourth plastic cable tie should be of the cushioned type, not evident here, according to the wire experts who examined the photo. Notice the proximity of wires to sharp metal edges, including hex nuts. Note above the bus, the plastic clamp holding all the bundles up against what appears to be pneumatic tubing, a clear violation of good wiring practices.
Poor wire routing, tie-wrapping and clamping.