On July 28, 2005, about 1255 Alaska daylight time, a float-equipped deHavilland DHC-3 airplane, N6868B, received minor damage due to an in-flight fire during cruise flight, about 5 miles southeast of Ketchikan, Alaska. The airplane was being operated as a visual flight rules (VFR) local area sightseeing flight under Title 14, CFR Part 135, when the accident occurred. The airplane was operated by Promech Air, Ketchikan. The airline transport certificated pilot received serious injuries as the result of burns to his hands. The ten passengers were not injured. Visual meteorological conditions prevailed, and VFR company flight following procedures were in effect. The flight originated at the Ketchikan Seaplane Base about 1125, for a flight to the Misty Fjords National Monument. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on July 28, the director of operations for the operator reported that the flight was returning to Ketchikan when a flash fire erupted near the windshield/glare shield area of the cockpit, in front of the pilot. The pilot made an emergency landing, and a passenger assisted by utilizing a fire extinguisher to put out the fire. The pilot received second-degree burns to his hands. A second company airplane landed and assisted the pilot and passengers. The director of operations for the operator reported that the airplane's engine had recently been removed, and a 1,000 horsepower WSK PZL Kalis engine, model number ASZ-62IR-M18, was installed on July 26, 2005. The airplane then had an annual inspection and returned to service. The airplane was manufactured in 1958, and had accrued 3,742 hours on the airframe, and 6.4 hours since the last annual inspection. The director of maintenance for the operator reported that a postaccident examination of the airplane revealed a pin-size hole in an aluminum fuel pressure bourbon line, utilized as a fixed line between the engine firewall, and an airframe longitudinal former, behind the instrument panel. The bourbon line is located between flexible fuel pressure lines from the engine to the firewall, and from the airframe former to the backside of the fuel pressure gauge. The director of maintenance indicated that he believed the line was not disturbed during the most recent engine change, and he said the line was located about 20 inches from any electrical wiring. He removed the line and sent it to the NTSB IIC, and the line was then submitted to the NTSB Material Laboratory for examination. The laboratory examination found a circular-shaped hole about 3 inches from the firewall end of the line. A longitudinal cut was made through the hole which revealed blue and brown tinting, and evidence of metal flow typical of re-solidification. The features of the hole were consistent with heat damage from electrical arcing. The wall of the tube had no evidence of corrosion.