(Adds Asiana comment in 13th paragraph and flight number in 5th
By Alwyn Scott and Annika McGinnis
WASHINGTON, June 24 U.S. investigators on
Tuesday said Boeing Co should consider modifying flight
controls on the 777 jetliner in response to an Asiana Airlines
crash in San Francisco last July that killed three
people and injured more than 180.
The National Transportation Safety Board accepted 30
findings following an 11-month investigation into the July 6,
2013 crash, and made more than two dozen recommendations to the
Federal Aviation Administration, the Seoul-based airline,
Boeing, firefighters and San Francisco city and county.
The NTSB said its probe did not find any failures in the
auto-throttle system or any other flight control or warning
system. The pilots committed 20 or 30 errors in the final 14
miles of approach, the NTSB said, and it cited "mismanagement"
by the pilots as the probable cause of the crash.
The pilots, though experienced, didn't understand exactly
how the auto throttle functioned and that it would not maintain
minimum air speed in all circumstances.
That complexity, and flight training manuals that did not
clearly describe how the controls would operate, contributed to
the crash of Asiana Airlines Flight 214, the NTSB investigation
"The automation performed as designed, but the pilots did
not fully understand what the automation would and would not
do," NTSB Acting Chairman Christopher Hart said. "It was not a
design issue by itself, it was the intersection between the
design and the pilots' understanding of how the design worked."
The airline's training may not have adequately prepared the
co-pilot, who was supervising the captain making his first
landing at the airport in a Boeing 777. Crew fatigue also played
a role, the NTSB investigators said.
The board recommended that Boeing develop and evaluate
changes to the control systems to ensure the plane's "energy
state" - a combination of speed, altitude, engine thrust and
other factors - "remains at or above the minimum desired ... for
any portion of the flight."
It also said Boeing and Asiana should revise flight training
manuals to better explain the auto-throttle functions.
And it called on the FAA to convene a special certification
review of how the 777 automatically controls air speed and use
that to make existing and future controls more intuitive.
The 777 auto throttle protects against low speed, and will
even "wake up" from being off to correct speed. But in "hold"
mode, the system requires a pilot to control speed, and will not
prevent speed from slipping below the minimum needed to stay
aloft, the NTSB said. The Asiana flight's system was in "hold"
mode and the pilots did not realize the risk, the NTSB said.
Had "wake up" been designed to occur in "hold mode," the
auto throttle "would likely have increased 20 seconds before
impact, which may have prevented the accident," said Roger Cox,
a senior NTSB air safety investigator.
Asiana said the NTSB had "properly recognized the multiple
factors that contributed to the accident, including the
complexities of the auto-throttle and autopilot systems, which
the agency found were inadequately described by Boeing in its
training and operational manuals. The recommendations made by
the agency can help ensure such an incident does not happen
The airline also said it had already implemented the four
training recommendations the NTSB made for its own operations
and had further strengthened training and safety.
Boeing said it "respectfully disagrees" with the NTSB's
finding that the automated system on the 777 contributed to the
accident. "We do not believe (it) is supported by the evidence,"
spokesman Doug Alder said in a statement. "We note that the 777
has an extraordinary record of safety - a record established
over decades of safe operation."
The Boeing 777, a wide-body, long-range aircraft, had no
prior fatal accidents since its introduction in 1995.
The 777 auto-flight system has flown more than 200 million
hours on several models and made more than 55 million safe
landings, Boeing said.
Boeing will review the board's recommendations carefully but
said any potential changes to systems must be weighed "with due
consideration for the potential unintended consequences."
The NTSB also raised concern that firefighters lacked
training. Airplane fires require specialized skills, and city
firefighting officers who took over at the scene had no previous
experience working at an airport, the NTSB said.
Emergency responders transported more than 300 people within
90 minutes, including 192 people to local hospitals.
But responders did not adequately verify their belief that
one passenger - 16-year-old Ye Meng Yuan - had died. She was run
over by two firefighting vehicles about a half an hour after the
crash, the NTSB said.
(Reporting by Alwyn Scott in Seattle and Annika McGinnis in
Washington; Editing by James Dalgleish, Sofina Mirza-Reid and