ANC98FA069

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 during a climb, the pilot noted smoke and heat coming from beneath the mid-cabin floor, and declared an emergency, reporting a fire in the airplane. 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. Post-accident examination disclosed a fuel line, a bundled set of electrical wires, and a Loran antenna cable, had all been routed adjacent to each other under the cabin floor, contrary to FAA recommended methodology. 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.

History of flight

On June 9, 1998, about 1231 Alaska daylight time, a wheel equipped Cessna 207A airplane, N96AK, sustained substantial damage during an emergency landing and ditching, about 4 miles southwest of Juneau, Alaska. The airplane was being operated as a visual flight rules (VFR) scheduled passenger flight under Title 14 CFR Part 135, when the accident occurred. The airplane was operated by Wings of Alaska, Juneau, as Flight 17 to Hoonah, Alaska. The certificated commercial pilot, and the four passengers, were not injured. Visual meteorological conditions prevailed. VFR company flight following procedures were in effect. The flight originated at the Juneau International Airport, about 1213.

The pilot reported that while climbing through 1,900 feet msl, approaching the coast of Barlow Cove (about 9 miles southwest of Juneau), she smelled smoke in the airplane. The passengers also indicated they smelled smoke. The pilot made a 180 degree turn to return to Juneau, and then saw smoke coming from the rear of the airplane, possibly from the baggage area. At 1226:50, the pilot called the Juneau Air Traffic Control Tower (ATCT) stating, "Juneau Tower, Wings 96, ah I'm declaring an emergency, I've got a fire." The airplane was cleared to land at Juneau.

The passengers reported smoke and heat coming from the floor area, under the right front seat. The pilot told the passengers to use the airplane's Halon fire extinguisher to put out the fire. The airplane cabin filled with smoke, hindering the pilot's vision. Several passengers said they saw a red glow coming from the floor mounted vent, located between the front and second row seats.

At 1228:48, in response to a position report request from the Juneau ATCT, the pilot reported, "ah I think I'm at the north side of Portland, and we're gonna try to put it down." The pilot selected a landing area near the northwest tip of Portland Island, located in the Favorite Channel of the Lynn Canal. The pilot said her first approach to a beach area in a southerly direction was too fast, and she decided to turn right toward another beach on the west side of the island. The pilot landed in the water, just short of the beach. The airplane received damage to the right wing, fuselage, and nose gear. After ditching, the fire was self-extinguished by ocean water, and the passengers waded ashore in ankle deep water.

The accident occurred during the hours of daylight at latitude 58 degrees, 20.25 minutes north, and longitude 134 degrees, 44.25 minutes west.

Crew information

The pilot holds a commercial pilot certificate with airplane single-engine land and sea, multiengine land, and instrument airplane ratings. In addition, the pilot holds a flight instructor certificate with airplane single-engine, and instrument airplane certificates. The most recent first-class medical certificate was issued to the pilot on June 27, 1997, and contained no limitations.

According to the operator, the pilot's total aeronautical experience consisted of about 1,330 hours, of which 45 were accrued in the accident airplane make and model.

The pilot was hired by the operator on April 20, 1998. She completed a 14 CFR Part 135.293/.299 check ride on May 2, 1998, in a Cessna 206. She completed a Part 135.293 check ride in a Cessna 207 on May 31, 1998.

Aircraft information

The airplane had accumulated a total time in service of 11,809.1 hours. Examination of the maintenance records revealed that a mechanical irregularity was noted on December 8, 1997; the navigation light circuit breaker had popped. The corrective action noted by a company mechanic was that a short was found, and corrected, in the left wing wiring. The most recent annual inspection was accomplished on December 30, 1997, 470.9 hours before the accident. In addition, a 100-hour inspection was completed on May 29, 1998, 45.8 hours before the accident. Each company inspection checklist includes an inspection of the internal structure of the fuselage, an inspection of the flight control cables, and an inspection of the antennas and antenna cables.

The lower cabin/fuselage structure is comprised of laterally placed, vertically oriented, aluminum formers. In the area of the fire, from forward to aft in the cabin, the most forward lateral former is under the instrument panel, ahead of the fuel reservoir tanks. The second lateral former is located aft of the fuel reservoir tanks, adjacent to the forward cabin door post, and the wing lift strut attach points. The third former is located about midway between the forward and aft door post. The fourth former is located just forward of the main gear attach point, adjacent to the aft door post. Two longitudinal formers are attached near the outboard edges of the fourth lateral former, and angle inboard to the second lateral former. All of the formers have flanged openings (lightening holes) oriented along their respective spans. The cabin floor is riveted to the fuselage formers. Access holes in the floor, each with a removable cover, are provided for maintenance and inspection procedures. The lower belly skin of the airplane is riveted to the fuselage formers.

Rear cabin floor ventilating air, both fresh and heated, is supplied by three ducts, including a duct extending under the center of the cabin floor. The floor duct outlet is a 90 degree plastic elbow that is flush mounted to the floor. The upper end of the floor duct has a screen covering the duct opening, and a removable, and rotatable airflow diverter. The lower portion of the duct, under the floor, has a flexible hose attached to the forward end of the duct. The hose is routed under the floor to the heat/ventilation system.

Fuel for the engine is routed from the two wing fuel tanks. The lines from the tanks descend vertically down each side of the fuselage wall, under the interior floor of the cabin, and then forward horizontally to reservoir tanks, one for each fuel tank. The left and right horizontal fuel lines are formed in a modified "Z" shape. The right fuel line is routed from a union/fitting under the cabin floor, located just forward of the fourth lateral former, then outboard through the right longitudinal former and the third lateral former, then forward through the second lateral former to the right reservoir tank. The fuel lines are constructed of 5052 aluminum, and are 1/2 inch in diameter.

Electrical wires for the tail position light, the tail mounted rotating beacon, and a Loran antenna, were routed horizontally under the floor, adjacent to the right fuel line. The operator installed molded plastic clamps to the vertical edges of the lighting holes. Each clamp is comprised of a plastic tab, through which a screw or bolt secured the clamp body to a former, and a small "U" shaped body, oriented 90 degrees to the tab. The wires and the antenna cable were attached to the body of the clamp by a plastic, self locking tie wrap. If the clamp is installed by the use of a screw, the screw is installed on one side of a former. The threads of the screw extend through the former, and slice new threads in the plastic body of the clamp tab on opposite side of the metal former.

A review of major repair and alteration records (FAA Form 337), revealed the airplane's Loran receiver was installed on February 20, 1988. The cable was routed from the instrument panel, under the cabin floor, alongside the tail position light and rotating beacon wires, to about the landing gear attach point. The cable was then routed up to the top of the fuselage.

Electrical circuit breakers are provided for each electrical circuit. The rotating beacon light circuit is provided with a 10 amp breaker. The position light circuit is provided with a 5 amp breaker. The circuit breakers are designed to open when their internal temperature is exceeded.

Communications

A transcript of the air to ground communic