The Pan American Boeing 747 struck the Approach Light Structure (ALS) at the departure end of runway 01R while taking off from the San Francisco International Airport. Two passengers, in seats 47G and 48G, were seriously injured by parts of the Approach Light System structure which penetrated the passenger compartment. The flightcrew continued the takeoff and then flew the aircraft for 1 hour and 42 minutes while assessing the structural damage and dumping fuel before landing on runway 28L. After landing, the aircraft veered off the right side of runway 28L and came to a stop in the unpaved area approximately 5,300 feet from the approach end of the runway. The passengers and crew evacuated the aircraft using the emergency evacuation slides. Upon activation of the slides for evacuation, four of the 10 passenger slides failed to function properly and were not useable. During the evacuation the aircraft tilted slowly back onto the rear section of the fuselage. The aircraft had been dispatched for a departure from a closed runway and, upon changing to an open runway, the crew did not recompute the proper reference speeds for takeoff under the existing conditions. PROBABLE CAUSE: “The National Transportation Safety Board determines that the probable cause of this accident was the pilot’s use of incorrect takeoff reference speeds. This resulted from a series of irregularities involving: (1) the collection and dissemination of airport information; (2) aircraft dispatching; and (3) crew management and discipline; which collectively rendered ineffective the air carrier’s operational control system.”