Flight 811 took off from Honolulu International Airport bound for Auckland, New Zealand with 3 flight crew, 15 flight attendants, and 337 passengers at approximately 01:52 HST. Its flight crew consisted of Captain David Cronin, First Officer Al Slater and Flight Engineer Mark Thomas.
During the climb, the crew made preparations to detour around thunderstorms along the aircraft's track; anticipating turbulence, the captain kept the seat-belt sign lit. Around this time (02:08) the plane had been flying for approximately 16 minutes and was passing between 22,000 and 23,000 feet (6,700–7,000 m). In the business-class section, a grinding noise was heard, followed by a loud thud which rattled the whole aircraft — 1½ seconds later the forward cargo-door blew out abruptly. The pressure differential caved in the main cabin floor above the door, causing ten seats (8G&H through 12G&H) and an individual seated in 9F to be ejected from the cabin, resulting in nine fatalities (seats 8G and 12G were empty) and leaving a gaping hole in the aircraft. The fatalities were: Anthony and Barbara Fallon, Harry and Susan Craig, Lee Campbell, Dr. J Michael Crawford, John Swan, Rose Harley and Mary Handley-Desso. Mae Sapolu, a flight-attendant in the Business-Class cabin, was almost pulled out of the plane, but was seen by passengers and fellow crew clinging to a seat leg; they were able to pull her to safety inside the cabin, although she was severely injured. The pilots began an emergency descent to get the aircraft rapidly down to breathable air, while performing a 180-degree left turn to take them back to Honolulu. The decompression had damaged components of the on-board emergency oxygen supply system, which is primarily located in the forward cargo sidewall area, just aft of the cargo door.
The debris ejected from the plane during the explosive decompression caused severe damage to the number 3 and 4 engines, causing visible fires in both. The crew did not get fire warnings from either of them, although engine 3 was experiencing heavy vibration, no N1 reading, and low EGT and EPR, leading the crew to deactivate it. At 02:10, an emergency was declared, and the crew began dumping fuel to get the plane's weight down to an acceptable landing weight. Initially, they pushed the number 4 engine slightly to help force the plane down faster, but once they noticed it was giving almost no N1, high EGT, and was emitting flames, they shut it down also. Some of the explosively ejected debris damaged the right wing's LEDs (Leading Edge Devices), dented the horizontal stabilizer on that side, and even struck the tailfin. NTSB reports found human remains in the fan blades of Number 3 engine, bringing a cold comfort that some of the victims died almost instantly as they were pulled out of the plane.
During the descent Captain Cronin had ordered Flight Engineer Randal Thomas to tell the flight attendants to prepare for an emergency landing, but he was unable to contact the flight attendants. Thomas asked the captain if he could go down and find out what was happening. Cronin agreed. Thomas saw severe damage immediately upon leaving the cockpit: the aircraft's skin was peeled off in some areas on the upper deck revealing the frames and stringers. As he went down to the lower deck the magnitude of the damage became obvious as he now saw the gigantic hole in the side of the plane. Thomas came back to the cockpit, visibly pale, and reported that large section of fuselage aft of the Number 1 exit door was open. He concluded that it was probably a bomb, and considering the condition of the plane, it would be unwise to exceed 250 knots (460 km/h). The plane's stall speed was around 240 knots (440 km/h), producing a narrow operating envelope.
As the plane neared the airport, the landing gear was extended. The flaps were only partially deployed, as a result of damage sustained following the decompression. This resulted in a landing speed between 190–200 knots (350–370 km/h). Regardless, Captain Cronin was able to get the plane to a halt without going off the end of the runway. Fourteen minutes had elapsed since the emergency was declared. Evacuation was carried out and all passengers and flight attendants were off in less than 45 seconds, though every flight attendant suffered some injury during the evacuation, ranging from scratches to a dislocated shoulder.
The NTSB issued a recommendation for all 747-100s in service at the time to replace their cargo door latching mechanisms with new, non-faulty locks. A sub-recommendation suggested replacing all outward-opening doors with inward-opening doors, which cannot open in flight due to the pressure differential. No similar fatality-causing accidents have officially occurred on this aircraft type, although other investigations indicate the possibility that other old Boeing 747s were afflicted.
In 1989, the flight crew received the Secretary's Award for Heroism for their actions. United Airlines ran a simulation through a flight simulator and were, despite many attempts and variable tweaks, unable to successfully land a plane after losing the forward cargo door.
The aircraft was successfully repaired, re-registered as N4724U in 1989, and returned to service with United Airlines in 1990. In 1997, the aircraft was registered with Air Dabia as C5-FBS, but abandoned in 2001 during overhaul maintenance at Plattsburgh International Airport. The plane was broken up for parts in 2004.
Original Source: http://en.wikipedia.org/wiki/United_Airlines_Flight_811