Asiana Airlines Inc. said Boeing Co. should add cockpit warnings for its 777 jet so pilots don’t mistakenly get too slow using automatic speed controls that U.S. regulators urged the planemaker to upgrade.
Asiana, commenting on the crash that killed three people on July 6 in San Francisco, also said in a filing yesterday for the first time that its pilots erred in letting the 777 decelerate and strike a seawall as it neared the airport.
While crew actions will be central to investigators’ findings, Asiana’s comments to the U.S. National Transportation Safety Board show the design of one of Boeing’s most successful models is also under scrutiny. NTSB records released Dec. 11 show the pilot inadvertently switched the auto-throttle to a setting that didn’t hold the plane’s speed, causing it to slow and begin descending.
Boeing said the jet was “functioning as expected prior to impact and did not contribute to the accident,” according to its submission to the NTSB. The pilots would have prevented the accident if they had followed Asiana guidelines requiring an aborted landing under the circumstances, the manufacturer said.
The filings were added to the NTSB’s record of the Asiana investigation and may be considered as the agency decides on the crash’s causes and underlying issues. The accident was the first in more than four years involving fatalities on a passenger airline on U.S. soil.
The 777, the world’s largest twin-engine jetliner, entered commercial service in 1995. Last year’s accident was the first involving fatalities, and only the third that was serious enough to destroy a 777. A fourth 777 presumed destroyed is a missing Malaysian Air 777-200ER model, the same as the Asiana jet.
Simulations of the Asiana flight’s approach done by test pilots for Chicago-based Boeing and the U.S. Federal Aviation Administration showed it was almost impossible to have made the landing without violating the airline’s criteria for a safe and stable touchdown, according to the airline’s submission.
In addition to the crew’s actions, the accident was caused by “inconsistencies in the aircraft’s automation logic, which led the crew to believe that the auto-throttle was maintaining the airspeed set by the crew,” Asiana said in its submission.
Asiana also faulted “inadequate warning systems” that didn’t give the pilots enough notice the auto-throttle wasn’t protecting them and they were losing speed. The plane got almost 40 miles (64 kilometers) an hour less than the target landing speed, according to the NTSB.
The Korean Aviation and Railway Accident Investigation Board endorsed the airline’s submission, according to a March 17 letter to the NTSB released yesterday. The South Korean agency said it plans a more-formal report on its findings later.
The FAA in 2011 had urged Boeing to improve the auto-throttle system after one of its test pilots discovered the equipment could, in effect, be shut off in some settings, according to another document released yesterday.
Asiana also said the path assigned by air-traffic controllers contributed to the accident, giving pilots too much work to do to descend and slow the plane before approaching the runway.
The NTSB conducted simulations of the Asiana landing in January with 777 pilots from Boeing and the FAA. Both teams had difficulty meeting standard criteria for a safe landing, known as a “stabilized approach,” according to the submission.
The pilots sank too quickly, didn’t set the throttles properly or were too high and fast on the simulated landings, according to the submission. An FAA test pilot said he became “confused” by the plane’s automated systems and thought the auto throttle “was not working right.”
Out of 20 tests, none met Asiana’s guidance for how to conduct a landing, the airline said.
Boeing said its recommended landing procedures, which have been adopted by Asiana, call for a pilot to abort a touchdown and climb away from the runway if a plane is off its target speed, too low or off course.
There were “numerous cues” as the plane neared the runway to indicate that the plane wasn’t properly set up to land, Boeing said in its submission.
The pilot at the controls, Lee Kang Kuk, 45, told investigators he was reluctant to call for an aborted landing because that was the responsibility of the more-senior pilot in the cockpit, Lee Jung Min, 49, according to NTSB records. Lee Kang Kuk was training to become a 777 captain.
An appendix adds details to documents released in December showing an FAA test pilot flying Boeing’s new 787 Dreamliner in 2010 had experienced a similar issue. The auto-throttle designs are almost identical on the two models.
In most modes, the 777’s auto-throttle automatically adds power to ensure a safe airspeed. Those protections don’t exist in at least one combination of settings, which is what happened to the test pilot and the Asiana crew, according to the FAA pilot and NTSB records.
“The FAA strongly encourages Boeing” to improve its systems to ensure pilots don’t inadvertently lose speed protection, the agency said in 2011.
Boeing said it designs planes so that the pilots have final authority over a flight, which requires they monitor automated systems and intervene if they don’t work as expected.
“There are clear indicators built into the auto-flight system that make it easy for the crew to always be aware of their situation,” Boeing said in its submission. “The entire crew always has the responsibility to monitor course, path, and airspeed, and to intervene if the auto-flight system is not performing as expected.”