In documents filed with federal accident investigators, Asiana Airlines stated Monday that flawed automatic throttles and the pilots themselves failed to maintain enough speed and altitude to safely land at San Francisco International Airport in July.
Asiana's assertion about the throttles was immediately countered by Boeing Co., which lodged its own report with investigators, saying that the pilots were solely to blame and Boeing 777's automated throttle system was working properly.
Asiana and Boeing filed their reports with the National Transportation Safety Board, the primary agency investigating the July 6 crash that killed three teenagers. The NSTB's final report on the cause of the accident has not been released.
The Asiana jetliner struck a seawall at the end of the San Francisco runway, shearing off the tail section and ejecting three flight attendants who were still in their seats. Wreckage was scattered across the airfield as the jet spun around.
Asiana told the National Transportation Safety Board that the auto throttles had major design flaws related to its settings that misled pilots into believing the system was maintaining the airspeed. The system also lacked an alerter to warn pilots when their speed sharply declined, the report stated.
Airline officials noted that U.S. and European aviation officials have had similar concerns and warned Boeing about the matter.
The South Korean airline conceded, however, that its pilots failed to monitor and maintain the required speed and altitude during the final approach for landing.
The trainee captain at the controls told investigators he was concerned about his ability to land the plane manually without automated systems. He said that the approach was very stressful and that he mistakenly thought the auto throttle would maintain the proper speed.
Boeing officials told the NTSB that the airplane's auto throttles, a kind of cruise control for planes, were functioning as expected.
They said that at an altitude of 500 feet, the crew should have noticed that the approach did not conform to established procedures, although they had significant indications that their speed, thrust settings and altitude were not correct.
In addition, the NTSB's preliminary investigation indicated that the auto throttles were working properly the day of the crash and showed "no anomalous behavior."