On May 11, 1997, about 1934 eastern daylight time, a McDonnell Douglas DC-10-30, G-NIUK, operated by Flying Colours Airlines Inc., as British Airways Flight 4508 (BA4508), operating as a Title 14 CFR Part 129, scheduled flight, from San Juan, Puerto Rico to Gadwick, England, was evacuated via the slides after the No. 3 (right) engine caught fire at the San Juan International Airport. Visual meteorological conditions prevailed and an a IFR flight plan was filed. The airplane was not damaged. The flightcrew of 3, cabin crew of 11, and 248 passengers were not injured. One passenger was seriously injured during the evacuation. The airplane was taxiing for departure on taxiway "N", when a strong smell of fuel was detected in the passenger cabin. About the same time, the crew of a commuter flight taxiing behind BA4508, reported that the DC-10's right engine was on fire. The crew of BA4508 saw the smoke from the cockpit window, the captain stopped the airplane, shut down the engines, and ordered an evacuation. At 1939, crash fire rescue equipment was used to put out the fire. Passengers said that they smelled "raw aviation fuel in the cabin." They said, "...the smell was very different from the smell of engine exhaust fumes common on planes when the engines first start up." Several of the passengers became concerned about their safety, and overheard flight attendants tell passengers the smell was "not unusual" and there was "no need to worry." After a few minutes the flight crew announced to the passengers that "they were aware of the presence of fumes in the cabin and that the air conditioning intake was being changed to the auxiliary power unit." The smell of fuel was reduced, but still "strong." According to the passengers "several" minutes elapsed before the engines were shut down, and they received an announcement from the flight crew that they would be returning to the gate. Another announcement was made that they would be returning to the gate, but the airplane remained stationary with the engines shut down. A passenger described the evacuation by saying the "lights went out momentarily and emergency lighting illuminated; a faint alarm sounded; the cabin crew screamed Get out! Get out! There was general panic in the cabin-passengers screamed and pushed to get out...some...passenger[s]...had not cleared the bottom of the shute [sic]. No-one was at the bottom of the shute [sic] to help people stand up and move out of the way promptly." After evacuating the airplane passengers were standing around on the tarmac and did not know were to go. A passenger said, "nobody was directing passengers away from the plane: some passengers were standing near the bottom of the shute [sic]...others were moving away in all possible directions." Examination of the right engine [No.3] revealed that the fuel/oil heat exchanger was leaking fuel. There was no damage to the engine or the airframe. The heat exchanger (part number 158210-11) from the No. 3 engine was returned Normalair, United Kingdom (UK), and examined under the supervision of AAIB (Air Accidents Investigation Branch), Department of Transportation (see AAIB report attached to this report). The examination revealed that the heat exchanger failed, and a "large fuel leak" had occurred into the oil system in the of the No. 3 engine. Detailed examination revealed that two high pressure internal baffles within the heat exchanger had become out alignment, due to fretting wear between the baffle plate and retaining slots in the casing. The pressure distribution across the affected baffle plates, due to the flow of oil through the unit, had loaded one end of the plate more than the other resulting in the fretting wear between the baffle plate and the retaining slot, causing the fuel leakage.