19980609012809A

Air taxi ditched in the water after experiencing a fire on board, 1 minor inj, acft was destroyed. (.4) the certificated commercial pilot, and four passengers, departed in a single-engine airplane on a scheduled commuter flight over terrain consisting of open water and wooded islands. Thirteen minutes later, the pilot declared an emergency, reporting a fire in the airplane. Smoke and heat were coming from beneath the mid-cabin floor. The pilot ditched the airplane in shallow water along a shoreline of a small island. The fire, which was located under the right front seat between the cabin floor and the lower airplane belly skin, was self-extinguished during the ditching. Postaccident examination disclosed a fuel line, a bundled set of electrical wires and a loran antenna cable, were routed adjacent to each other, under the cabin floor. The loran antenna cable had been installed 10 years prior to the accident. Two small holes, consistent with arcing, were found in the fuel line. Evidence of arcing was found on one of the electrical wires. Plastic tie wraps attached the wire/antenna bundle to plastic clamps that were each secured to fuselage formers under the floor by bolts or screws. One clamp, adjacent to the holes found in the fuel line, was missing from its attach point. A screw and a small melted portion of a plastic tie wrap were found adjacent to each other in the fuselage belly, beneath the cabin floor. An annual inspection was accomplished six months before the accident. A 100-hour inspection was completed 11 days before the accident. Each company inspection checklist includes an inspection of the internal structure of the fuselage, and an inspection of antenna cables. The FAA recommended technique for attaching clamps to structure is the use of bolts with locknuts, or self-locking nuts.