Having spent too many years investigating too many mishaps, one learns not to second guess the crew but rather one attempts to understand what information was being presented to the crew and in what format. The captain believed there was a fire, but there is no indication in what format that information was being presented to the captain and on what he based his decision to evacuate the aircraft. All we know is that he stated he had a fire and he decided to evacuate the aircraft. Why is unknown.
As to why the aircraft did not depressurize, here is one theory being put forward (again, nothing official):
Blocked Pressure Valves Could Have Led To Death Of Flight Attendant
Dec 4, 2000
Insulation blankets left unfastened in the cargo hold of an American Airlines plane partially blocked both valves that control cabin pressure and possibly contributed to the death of a flight attendant during an emergency evacuation.
Jose Chiu, 34, died from injuries he suffered when the left front door of the Airbus A300 "exploded open" and he was thrown to the ground at Miami International Airport, the National Transportation Safety Board's (NTSB) preliminary report shows.
The plane's captain, Neal Talbot, 44, had reported trouble pressurizing the Airbus A300 shortly after departure from Miami for Port-au-Prince, Haiti.
After returning to Miami for an emergency landing, the captain said he was unable to depressurize the plane, and then ordered an evacuation because he believed there was a fire on board, the NTSB report says.
Passengers described a crushing sensation caused by mounting cabin pressure, as flight attendants struggled to open the doors. Finally, Chiu, the lead attendant, pried open the door and was catapulted an estimated 40 feet or more from the plane.
Jorge Prellezo, NTSB regional director, said the insulation blankets, normally secured with plastic fasteners, were somehow dislodged and partially obstructed the pressurization valves in the plane's cargo hold.
The rear valve was found about 90 percent blocked while the front valve was about one-third blocked, said Jeff Kennedy, air safety investigator for the NTSB, who is leading the investigation.
The heavy blankets, which insulate the cargo area, were two or three feet out of their normal position, Prellezo said. They are supposed to be fastened to the wall as a maintenance procedure.
The plane's flight to Port-au-Prince was its first after undergoing two days of undisclosed maintenance at American Airlines' Miami hangar.
While Prellezo called the finding regarding the blankets "significant," he said it did not entirely cause the pressurization problem. "We're looking at the procedures the crew was using," he said.
"The pressurization system is a complex system with many components, and we need to see exactly what went wrong to cause the problem."
The plane is now at American's maintenance base in Tulsa, Okla., being tested.
*NO CARRIER* -- A Naval Aviator's worst nightmare!