Possible Causes of the Asiana Flight 214 Crash
The National Transportation Safety Board (NTSB) is working with Boeing, the
Federal Aviation Administration (FAA), and the Korean Air and Accident Investigation
Board to determine the exact cause of the crash. A typical NTSB crash
investigation can take 12 to 18 months, but Chairperson Deborah Hersman has
stated she hopes to have the report completed earlier. However, some possible causes can be surmised now.
There is no indication the weather played any part in the crash. The weather was fair and the aircraft was cleared for a visual approach. The tower may have requested the pilots make a visual approach as a result of the airport’s Instrument Landing System (ILS) not functioning at the time of the landing. NTSB’s Hersman addressed the issue by stating that because the jet was on a visual approach in excellent weather, “you don’t need instruments to get into the airport” safely.
There has been speculation, however, that Korean pilots tend to be more comfortable with automated systems and less comfortable with visual approaches than their western counterparts. A recent Reuters story reported a Korean government aviation official as saying that manual flying was once common among Korean pilots, many of whom where former military pilots, but in an effort to improve safety after a 1997 Korean Air crash in Guam, pilots were encouraged to make more use of automated controls. Many Korean commercial pilots are former military, having gained much of their flying experience in highly automated aircraft. On the other hand, commercial pilots who trained in the U.S. tend to have had an opportunity to hone their skills flying smaller, simpler planes with fewer automatic features.
Slow Approach Speed
The pilots allowed the jet’s speed to slow below proper approach speed causing it to lose altitude too quickly. Seven seconds before impact, a voice is heard on the cockpit voice recorder calling out to “increase speed.” The relief first officer who occupied the cockpit jump seat told NTSB investigators he was warning the pilots that their speed was too slow as they approached the runway. Four seconds before impact, the stall warning stick shaker rattled into audible action. One and a half seconds before impact, the pilots attempted to initiate a go-around, but by that point, the airplane was descending too close to the ground to recover.
Last-second Abort Attempt
According to former TWA pilot Barry Schiff, once the airplane nears its
destination and goes below an altitude of 500 feet, “target airspeed on final
approach must be established and stabilized; power required for the descent must
be established and stabilized; the required rate of descent must be established
and stabilized; and the airplane must be on the desired descent profile and
stabilized. If any of these variables becomes unstabilized or allowed to vary
significantly, the pilot is required to abandon the approach and begin anew.”
On a typical Boeing 777 landing flying at an appropriate landing speed of 132
knots, the plane will descend to the benchmark of 500 feet about 35 to 42
seconds before landing. It is unknown at this point why the Asiana 214
pilot did not attempt to abort the landing until a
few seconds before impact.
Aircraft Equipment or Systems Failure
From initial NTSB reports, there was no indication of any problem, mechanical or otherwise, with no distress calls or other problem reports during the flight except for the final few seconds. The NTSB is investigating whether a failure in the mechanics or in the crew’s use of the aircraft’s autothrottle system could have occurred.
The NTSB reports that the autothrottle was programmed to be in the “Vertical Speed mode,” one of the three available modes. Typically, the Vertical Speed mode is used for step down descents during an earlier part of the approach process. The most preferred mode for final approach is known as the “Vertical Navigation with Speed Intervention mode.” It is not yet known why the pilot chose a less common mode for the final approach.
In addition, the autothrottle control was found to be in the “armed” position during documentation of cockpit levers and switches, differing from both the “on” and “off” positions, and the flying pilot’s flight director was deactivated whereas the instructor pilot’s was activated. “Armed” means the autothrottle is available to be engaged, but is not necessarily active. Thorough understanding of each of the modes of the autothrottle, as well as understanding its armed and automatic processes and limitations, is critical during final descent. The pilot must also be prepared to land the plane manually in case there is any equipment malfunction or confusion.
NTSB will attempt to understand the pilot’s actions with respect to use of
the autothrottle and their ability to land the plane without the use of the
The flying pilot was undergoing training and had never before landed a Boeing 777 plane at San Francisco International Airport (SFO). He only had 43 hours in the Boeing 777. Likewise, Flight 214 was the trainer pilot’s first flight as an instructor and he had never overseen a trainee during a landing. The NTSB will look at whether the training exercise distracted the pilots from performing their duties.
the crash, Asiana has already announced they will enhance the training
program for pilots looking to fly new aircraft. The new measures will include
enhancing training for visual approach and automated flight. They also pledge to
further conduct flight inspection at airports which are “vulnerable
One of the pilots reported being temporarily blinded by a bright light on approach at about 500 feet. There was little information regarding that claim and Chairperson Hersman discounted the idea that the light was from a potentially dangerous laser.
The crew was engaged in a training exercise. The NTSB will look to see whether the crew became so distracted during the
approach that they lost awareness of their airspeed. It is unknown if any of
the pilots were engaged with personal electronic devices such as a cellphone or
tablet during the approach. According to a New York Times story, one crash in
which cellphone interference with airplane navigation was cited as a possible
factor involved a charter in Christchurch, New Zealand, in 2003. Eight people
died when the plane flew into the ground short of the runway. In the New
Zealand crash, the pilot had called home and the call remained connected for
the last three minutes of the flight. In the final report, the New Zealand
Transport Accident Investigation Commission stated, “The pilot’s own cellphone
might have caused erroneous indications” on a navigational aid. Not to mention
the possibility of the pilot being distracted at one of the most critical parts
of the flight.
Potential Language Barriers
According to the NTSB, the pilots were speaking both English and Korean in the cockpit. We assume that communication with SFO air traffic controllers was in English and the Korean communication that was recorded would have been between the Korean pilots.
Additionally, it is unknown if the post-crash NTSB
interviews of the pilots were conducted in English, Korean or with the aid of
an interpreter. It would be part of the NTSB investigation to conclude if
language differences played any role in delaying action or misinterpreting
directives during the approach.
The pilots were at the end of a long transoceanic flight. The NTSB will
look at how fatigue played a role in the flight crew’s mistakes.
Construction at the Airport
According to the NTSB, a component of the airport’s Instrument Landing System (ILS) that tracks the glide path of incoming airplanes was not working at the time of the crash. The computerized system calculates a plane’s path of descent and sends the information to pilots in real-time. The NTSB will investigate how the runway markings and the absence of the instrument glide slope contributed to the accident.
The investigation will examine the crashworthiness of the airplane. In
particular it will examine the failure of some of the emergency slides to
properly deploy. Two of the emergency slides may have actually deployed inside the aircraft. Some passenger statements indicated that one of the
malfunctioning slides may have temporarily trapped a flight attendant.
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