New Airworthiness Directive Addresses MD-11 Fuel Tank Ignition Risk

Based on the manufacturer's fuel system review, the AD would affect 111 aircraft in U.S. service at a total cost of $2,251,635 to $2,721,831, FAA said.

The Federal Aviation Administration yesterday proposed a new airworthiness directive for certain McDonnell Douglas MD-11 and MD-11F aircraft to reduce the risk of fuel vapor ignition inside their upper auxiliary fuel tanks. The proposed action, which includes a one-time inspection and installation of nonmetallic barrier/shield sleeving, new clamps, new attaching hardware, and a new extruded channel, is based on the manufacturer's fuel system review and would affect 111 aircraft in U.S. service at a total cost in parts and labor of $2,251,635 to $2,721,831 (cost per airplane differs because of differences in their configuration, the notice states).

"We have determined that the actions identified in this AD are necessary to reduce the potential of ignition sources inside fuel tanks, which, in combination with flammable fuel vapors, could result in fuel tank explosions and consequent loss of the airplane," it states. "We have received a report that wire bundles routed above the center upper auxiliary fuel tank are in close proximity to the upper surface of the tank on certain McDonnell Douglas Model MD-11 and MD-11F airplanes. In addition, some wire harness mounts may have loosened, allowing the wires to contact the tank. This condition may cause wire damage or chafing that can lead to possible arcing, sparking, and burn-through on the fuel tank upper surface, which can result in a fuel tank explosion."

Comments on this proposed AD are due by Oct. 5; fax to 202-493-2251 or search for Docket No. FAA-2009-0686 at www.regulations.gov.

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