6/24/2014 9:00 AM
NATIONAL TRANSPORTATION SAFETY BOARD
Public Meeting of June 24, 2014
(Information subject to editing)
Descent Below Visual Glidepath and Impact With Seawall
Asiana Airlines Flight 214
San Francisco, California
July 6, 2013
This is a synopsis from the Safety Board’s report and does not include the Board’s rationale for the conclusions, probable cause, and safety recommendations.Â Safety Board staff is currently making final revisions to the report from which the attached conclusions and safety recommendations have been extracted.Â The final report and pertinent safety recommendation letters will be distributed to recommendation recipients as soon as possible.Â The attached information is subject to further review and editing.
On July 6, 2013, about 1128 Pacific daylight time, a Boeing 777-200ER, Korean registration HL7742, operating as Asiana Airlines flight 214, was on approach to runway 28L when it struck a seawall at San Francisco International Airport (SFO), San Francisco, California. Three of the 291 passengers were fatally injured; 40 passengers, 8 of the 12 flight attendants, and 1 of the 4 flight crewmembers received serious injuries. The other 248 passengers, 4 flight attendants, and 3 flight crewmembers received minor injuries or were not injured. The airplane was destroyed by impact forces and a postcrash fire. Flight 214 was a regularly scheduled international passenger flight from Incheon International Airport, Seoul, Korea, operating under the provisions of 14 Code of Federal Regulations Part 129. Visual meteorological conditions prevailed, and an instrument flight rules flight plan was filed.
The flight was vectored for a visual approach to runway 28L and intercepted the final approach course about 14 nautical miles (nm) from the threshold at an altitude slightly above the desired 3Â° glidepath. This set the flight crew up for a straight-in visual approach; however, after the flight crew accepted an air traffic control instruction to maintain 180 knots to 5 nm from the runway, the flight crew mismanaged the airplane’s descent, which resulted in the airplane being well above the desired 3° glidepath when it reached the 5 nm point. The flight crew’s difficulty in managing the airplane’s descent continued as the approach continued. In an attempt to increase the airplane’s descent rate and capture the desired glidepath, the pilot flying (PF) selected an autopilot (A/P) mode (flight level change speed [FLCH SPD]) that instead resulted in the autoflight system initiating a climb because the airplane was below the selected altitude. The PF disconnected the A/P and moved the thrust levers to idle, which caused the autothrottle (A/T) to change to the HOLD mode, a mode in which the A/T does not control airspeed. The PF then pitched the airplane down and increased the descent rate. Neither the PF, the pilot monitoring (PM), nor the observer noted the change in A/T mode to HOLD.
As the airplane reached 500 ft above airport elevation, the point at which Asiana’s procedures dictated that the approach must be stabilized, the precision approach path indicator (PAPI) would have shown the flight crew that the airplane was slightly above the desired glidepath. Also, the airspeed, which had been decreasing rapidly, had just reached the proper approach speed of 137 knots. However, the thrust levers were still at idle, and the descent rate was about 1,200 ft per minute, well above the descent rate of about 700 fpm needed to maintain the desired glidepath; these were two indications that the approach was not stabilized. Based on these two indications, the flight crew should have determined that the approach was unstabilized and initiated a go-around, but they did not do so. As the approach continued, it became increasingly unstabilized as the airplane descended below the desired glidepath; the PAPI displayed three and then four red lights, indicating the continuing descent below the glidepath. The decreasing trend in airspeed continued, and about 200 ft, the flight crew became aware of the low airspeed and low path conditions but did not initiate a go-around until the airplane was below 100 ft, at which point the airplane did not have the performance capability to accomplish a go-around. The flight crew’s insufficient monitoring of airspeed indications during the approach resulted from expectancy, increased workload, fatigue, and automation reliance.
When the main landing gear and the aft fuselage struck the seawall, the tail of the airplane broke off at the aft pressure bulkhead. The airplane slid along the runway, lifted partially into the air, spun about 330 degrees, and impacted the ground a final time. The impact forces, which exceeded certification limits, resulted in the inflation of two slide/rafts within the cabin, injuring and temporarily trapping two flight attendants. Six occupants were ejected from the airplane during the impact sequence: two of the three fatally injured passengers and four of the seriously injured flight attendants. The four flight attendants were wearing their restraints but were ejected due to the destruction of the aft galley where they were seated. The two ejected passengers (one of whom was later rolled over by two firefighting vehicles) were not wearing their seatbelts and would likely have remained in the cabin and survived if they had been wearing them.
After the airplane came to a stop, a fire initiated within the separated right engine, which came to rest adjacent to the right side of the fuselage. When one of the flight attendants became aware of the fire, he initiated an evacuation, and 98% of the passengers successfully self-evacuated. As the fire spread into the fuselage, firefighters entered the airplane and extricated five passengers (one of whom later died) who were injured and unable to evacuate. Overall, 99% of the airplane’s occupants survived.
The safety issues discussed in the report relate to the need for the following:
- Adherence of Asiana pilots to standard operating procedures (SOP) regarding
callouts. The flight crew did not consistently adhere to Asiana’s SOPs involving selections and callouts pertaining to the autoflight system’s mode control panel. This lack of adherence is likely the reason that the PF did not call out “flight level change” when he selected FLCH SPD. As a result, and because the PM’s attention was likely on changing the flap setting at that time, the PM did not notice that FLCH SPD was engaged.
- Reduced design complexity and enhanced training on the airplane’s autoflight system. The PF had an inaccurate understanding of how the Boeing 777 A/P and A/T systems interact to control airspeed in FLCH SPD mode, what happens when the A/T is overridden and the throttles transition to HOLD in a FLCH SPD descent, and how the A/T automatic engagement feature operates. The PF’s faulty mental model of the airplane’s automation logic led to his inadvertent deactivation of automatic airspeed control. Both reduced design complexity and improved systems training can help reduce the type of error made by the PF.
- Opportunity at Asiana for new instructors to supervise trainee pilots in operational service during instructor training. The PM was an experienced 777 captain who was on his first flight as an instructor pilot supervising a trainee captain gaining operating experience. The PM did not have the opportunity during his instructor training to supervise and instruct a trainee during line operations while being observed by an experienced instructor. Such an opportunity would have improved the PM’s awareness of the dynamic and often unpredictable challenges that an instructor must deal with when supervising a trainee during line operations.
- Guidance for Asiana pilots on use of flight directors during a visual approach. During the accident flight, after the A/P was disconnected, the PM loosely followed Asiana’s informal practice, which was to turn both flight directors (F/Ds) off and then turn the PM’s F/D back on when conducting a visual approach. However, the two F/D switches were not both in the off position at the same time. If they had been, the A/T mode would have changed to speed mode and maintained the approach speed of 137 knots. In addition, during a visual approach, F/D pitch and roll guidance is not needed and can be a distraction.
- More manual flight for Asiana pilots. Asiana’s automation policy emphasized the full use of all automation and did not encourage manual flight during line operations. If the PF had been provided with more opportunity to manually fly the 777 during training, he would most likely have better used pitch trim, recognized that the airspeed was decaying, and taken the appropriate corrective action of adding power. FAA guidance and a recent US regulatory change support the need for pilots to regularly perform manual flight so that their airplane handling skills do not degrade.
- A context-dependent low energy alert. The airplane was equipped with a low airspeed alerting system that was designed to alert flight crews to low airspeed in the cruise phase of flight for the purpose of stall avoidance. However, this accident demonstrates that existing low-airspeed alert systems that are designed to provide pilots with redundant aural and visual warning of impending hazardous low-airspeed conditions may be ineffective when they are developed for one phase of flight (i.e., cruise) and are not adequately tailored to reflect conditions that may be important in another phase of flight (e.g., approach). During the approach phase of flight, a low airspeed alert may need to be designed so that its activation threshold takes airspeed (kinetic energy), altitude (potential energy), and engine response time into account.
- Research that examines the injury potential from significant lateral forces in airplane crashes and the mechanism that produces high thoracic spinal injuries. In this accident, the dynamics were such that occupants were thrown forward and experienced a significant lateral force to the left during the impact sequence. One passenger sustained serious head injuries as a result of striking the arm rest of the seat that was in front of and to his left. While current Federal Aviation Administration (FAA) dynamic seat certification requirements do include testing row/row seat interactions with seats positioned slightly off the longitudinal axis, they would not likely approximate the forces encountered in this accident. Further, there was a high number of serious injuries to the high thoracic spine in this accident, and the mechanism that produces these injuries is poorly understood.
- Evaluation of the adequacy of slide/raft inertia load certification testing. The forces experienced by the slide/rafts during the impact sequence far exceeded their certification limits, leading to overload failures of the slide/raft release mechanisms on the 1R and 2R slide/rafts. Given the critical nature of these evacuation devices and their proximity to essential crewmembers, slides and slide/rafts must be certified to sufficient loads so that they will likely function in a survivable accident. Although this exact accident scenario is unlikely to occur again, the data obtained during this accident investigation could prove useful for future slide/raft design.
- Aircraft rescue and firefighting (ARFF) training for officers placed in command of an aircraft accident. The arriving incident commander placed an officer in charge of the fire attack who had not received ARFF training, and this individual made decisions that reflected his lack of ARFF training. Although no additional injuries or loss of life could be attributed to the fire attack supervisor’s lack of ARFF training, it demonstrates the potential strategic and tactical challenges associated with having nonARFF trained personnel in positions of command at an airplane accident.
- Guidance on when to pierce the fuselage of a burning airplane with a skin-piercing nozzle. The airport’s fire department had two vehicles equipped with high-reach extendable turrets (HRETs) that were not used to the best of their capabilities in the initial attack. This was partially the result of departmental guidance that discouraged penetration of the fuselage using the skin-piercing nozzles on the HRETs until all of the occupants were known to have evacuated the airplane. Current FAA guidance provides information on how to pierce but does not include any guidance on when to pierce.
- Integration of the medical supply buses at SFO into the airport’s preparation drills. Although the airport’s emergency procedures manual called for airport operations personnel to deliver the airport’s two emergency medical buses to the accident site, neither of the medical buses arrived. Further, the monthly emergency drills conducted by the airport did not include deployment of the buses either as a matter of routine or as part of the unique scenario being evaluated. This lack of integration of the medical buses into the airport’s preparation drills likely played a part in their lack of use in the initial response to the accident.
- Guidance or protocols for ensuring the safety of passengers and crew at risk of being struck or rolled over by a vehicle during ARFF operations. In this case, only one passenger was at significant risk for a vehicle strike due to her close proximity to the burning airplane; however, there are other accident scenarios in which many injured or deceased persons could be located near an accident airplane. There is currently no guidance or any recommended protocols for ensuring the safety of passengers and crew at risk of being struck or rolled over by a vehicle during ARFF operations.
- Requirements for ARFF staffing. Seven ARFF vehicles and 23 ARFF personnel from SFO’s fire department were involved in the initial response to the accident. This equipment level exceeded the FAA-required minimum of three vehicles, and there is currently no FAA-required minimum staffing level. Because of the amount of available ARFF vehicles and personnel, the airport firefighters were able to perform exterior firefighting and send firefighters into the airplane who rescued five passengers who were unable to self-evacuate amid rapidly deteriorating cabin conditions. Due to the lack of an FAA-required minimum staffing level, passengers involved in an aviation accident at a smaller airport may not be afforded the same level of protection that the passengers of flight 214 had.
- Improvements in emergency communications at SFO. Numerous problems with communications occurred during the emergency response, the most critical being the inability for responding mutual aid units to speak directly with units from the airport on a common radio frequency. Although some of the communications difficulties encountered during the emergency response, including the lack of radio interoperability, have been remedied, others, such as the breakdown in communications between the airport and city dispatch centers, should be addressed.
- Increased FAA oversight of SFO’s emergency procedures manual. Although the airport had submitted, and the FAA had approved in December 2012, an updated emergency procedures manual, the airport had not yet distributed or trained personnel on the updated manual when the accident occurred and was still actively operating with the manual approved by the FAA in December 2008.
- The following were not factors in the accident: flight crew certification and qualification; flight crew behavioral or medical conditions or the use of alcohol or drugs; airplane certification and maintenance; preimpact structural, engine, or system failures; or the air traffic controllers’ handling of the flight.
- Although the instrument landing system glideslope was out of service, the lack of a glideslope should not have precluded the pilots’ successful completion of a visual approach.
- The flight crew mismanaged the airplane’s vertical profile during the initial approach, which resulted in the airplane being well above the desired glidepath when it reached the 5 nautical mile point, and this increased the difficulty of achieving a stabilized approach.
- The flight crew’s mismanagement of the airplane’s vertical profile during the initial approach led to a period of increased workload that reduced the pilot monitoring’s awareness of the pilot flying’s actions around the time of the unintended deactivation of automatic airspeed control.
- About 200 ft, one or more flight crewmembers became aware of the low airspeed and low path conditions, but the flight crew did not initiate a go-around until the airplane was below 100 ft, at which point the airplane did not have the performance capability to accomplish a go-around.
- The flight crew was experiencing fatigue, which likely degraded their performance during the approach.
- Nonstandard communication and coordination between the pilot flying and the pilot monitoring when making selections on the mode control panel to control the autopilot flight director system (AFDS) and autothrottle (A/T) likely resulted, at least in part, from role confusion and subsequently degraded their awareness of AFDS and A/T modes.
- Insufficient flight crew monitoring of airspeed indications during the approach likely resulted from expectancy, increased workload, fatigue, and automation reliance.
- The delayed initiation of a go-around by the pilot flying and the pilot monitoring after they became aware of the airplane’s low path and airspeed likely resulted from a combination of surprise, nonstandard communication, and role confusion.
- As a result of complexities in the 777 AFCS and inadequacies in related training and documentation, the pilot flying had an inaccurate understanding of how the autopilot flight director system and autothrottleÂ interacted to control airspeed, which led to his inadvertent deactivation of automatic airspeed control.
- If the autothrottle automatic engagement function (wakeup), or a system with similar functionality, had been available during the final approach, it would likely have activated and increased power about 20 seconds before impact, which may have prevented the accident.
- A review of the design of the 777 automatic flight control system, with special attention given to the issues identified in this accident investigation and the issues identified by the Federal Aviation Administration and European Aviation Safety Agency during the 787 certification program, could yield insights about how to improve the intuitiveness of the 777 and 787 flight crew interfaces as well as those incorporated into future designs.
- If the pilot monitoring had supervised a trainee pilot in operational service during his instructor training, he would likely have been better prepared to promptly intervene when needed to ensure effective management of the airplane’s flightpath.
- If Asiana Airlines had not allowed an informal practice of keeping the pilot monitoring’s (PM) flight director (F/D) on during a visual approach, the PM would likely have switched off both F/Ds, which would have corrected the unintended deactivation of automatic airspeed control.
- By encouraging flight crews to manually fly the airplane before the last 1,000 ft of the approach, Asiana Airlines would improve its pilots’ abilities to cope with maneuvering changes commonly experienced at major airports and would allow them to be more proficient in establishing stabilized approaches under demanding conditions; in this accident, the pilot flying may have better used pitch trim, recognized that the airspeed was decaying, and taken the appropriate corrective action of adding power.
- A context-dependent low energy alert would help pilots successfully recover from unexpected low-energy situations like the situation encountered by the accident pilots.
- The flight attendants acted appropriately when they initiated an emergency evacuation upon determining there was a fire outside door 2R. Further, the delay of about 90 seconds in initiating an evacuation was likely due partly to the pilot monitoring’s command not to begin an immediate evacuation, as well as disorientation and confusion.
- Passengers 41B and 41E were unrestrained for landing and ejected through the ruptured tail of the airplane at different times during the impact sequence. It is likely that these passengers would have remained in the cabin and survived if they had been wearing their seatbelts.
- Passenger 42A was likely restrained for landing, and the severity of her injuries was likely due to being struck by door 4L when it separated during the airplane’s final impact.
- The dynamics of the impact sequence in this accident were such that occupants were thrown forward and experienced a significant lateral force to the left, which resulted in serious passenger injuries that included numerous left-sided rib fractures and one left-sided head injury.
- The reasons for the high number of serious injuries to the high thoracic spine in this accident are poorly understood.
- The release and inflation of the 1R and 2R slide/rafts inside the airplane cabin was a result of the catastrophic nature of the crash, which produced loads far exceeding design certification limits.
- Clearer guidance is needed to resolve the concern among airport fire departments and individual firefighters that the potential risk of injuring airplane occupants while piercing aircraft structure with a skin-penetrating nozzle outweighs the potential benefit of an early and aggressive interior attack using this tool.
- Medical buses were not effectively integrated into San Francisco International Airport’s monthly preparation drills, which played a part in their lack of use in the initial response to the accident and delayed the arrival of backboards to treat seriously injured passengers.
- Guidance on task prioritization for responding ARFF personnel, that addresses the presence of seriously injured or deceased persons in the immediate vicinity of an accident airplane, is needed to minimize the risk of these persons being struck or rolled over by vehicles during emergency response operations.
- The overall triage process in this mass casualty incident was effective with the exception of the failure of responders to verify their visual assessments of the condition of passenger 41E.
- The San Francisco Fire Department’s aircraft rescue and firefighting staffing level was instrumental in the department’s ability to conduct a successful interior fire attack and successfully rescue five passengers who were unable to self-evacuate amid rapidly deteriorating cabin conditions.
- Although no additional injuries or loss of life were attributed to the fire attack supervisor’s lack of aircraft rescue and firefighting (ARFF) knowledge and training, the decisions and assumptions he made demonstrate the potential strategic and tactical challenges associated with having non-ARFF trained personnel in positions of command at an airplane accident.
- Although some of the communications difficulties encountered during the emergency response, including the lack of radio interoperability, have been remedied, others, such as the breakdown in communications between the airport and city dispatch centers, should be addressed.
- The Alert 3 section of the San Francisco International Airport’s emergency procedures manual was not sufficiently robust to anticipate and prevent the problems that occurred in the accident response.
The National Transportation Safety Board determines that the probable cause of this accident was the flight crew’s mismanagement of the airplane’s descent during the visual approach, the pilot flying’s unintended deactivation of automatic airspeed control, the flight crew’s inadequate monitoring of airspeed, and the flight crew’s delayed execution of a go-around after they became aware that the airplane was below acceptable glidepath and airspeed tolerances. Contributing to the accident were; (1) the complexities of the autothrottle and autopilot flight director systems that were inadequately described in Boeing’s documentation and Asiana’s pilot training, which increased the likelihood of mode error; (2) the flight crew’s nonstandard communication and coordination regarding the use of the autothrottle and autopilot flight director systems; (3) the pilot flying’s inadequate training on the planning and executing of visual approaches; (4) the pilot monitoring/instructor pilot’s inadequate supervision of the pilot flying; and (5) flight crew fatigue which likely degraded their performance.
As a result of this investigation, the National Transportation Safety Board makes the following safety recommendations:
To the Federal Aviation Administration:
- Require Boeing to develop enhanced 777 training that will improve flight crew understanding of autothrottle modes and automatic activation system logic through improved documentation, courseware, and instructor training. (A-14-XX)
- Once the enhanced Boeing 777 training has been developed, as requested in Safety Recommendation , require operators Â and training providers to provide this training to 777 pilots. (A-14-XX)
- Require Boeing to revise its 777 Flight Crew Training Manual stall protection demonstration to include an explanation and demonstration of the circumstances in which the autothrottle does not provide low speed protection. (A-14-XX)
- Once the revision to the Boeing 777 Flight Crew Training Manual has been completed, as requested in Safety Recommendation , require operators and training providers to incorporate the revised stall protection demonstration in their training. (A-14-XX)
- Convene an expert panel (including members with expertise in human factors, training, and flight operations) to evaluate methods for training flight crews to understand the functionality of automated systems for flightpath management, identify the most effective training methods, and revise training guidance for operators in this area. (A-14-XX)
- Convene a special certification design review of how the Boeing 777 automatic flight control system controls airspeed and use the results of that evaluation to develop guidance that will help manufacturers improve the intuitiveness of existing and future interfaces between flight crews and autoflight systems. (A-14-XX)
- Task a panel of human factors, aviation operations, and aircraft design specialists, such as the Avionics Systems Harmonization Working Group, to develop design of context-dependent low energy alerting systems for airplanes engaged in commercial operations and establish requirements for such systems, based on the guidance developed by the panel. (A-14-XX)
- Conduct research that examines the injury potential to occupants in accidents with significant lateral forces, and if the research deems it necessary, implement regulations to mitigate the hazards identified. (A-14-XX)
- Conduct research to identify the mechanism that produces high thoracic spinal injuries in commercial aviation accidents, and if the research deems it necessary, implement regulations to mitigate the hazards identified. (A-14-XX)
- Analyze in conjunction with slide raft manufacturers the information obtained in this accident investigation and evaluate the adequacy of slide and slide/raft certification standards and test methods specified in Federal Aviation Administration regulations and guidance materials. If appropriate, modify certification standards and test methods for future slide and slide/raft design based on the results of this evaluation. (A-14-XX)
- Work with the Aircraft Rescue and Firefighting Working Group and equipment manufacturers to develop and distribute more specific policies and guidance about when, how, and where to use the high-reach extendable turret’s unique capabilities. (A-14-XX)
- Once the minimum staffing level has been developed by the Aircraft Fire and Rescue (ARFF) Working Group, as requested in Safety Recommendation , amend 14 Code of Federal Regulations 139.319(j) to require a minimum ARFF staffing level that would allow exterior firefighting and rapid entry into an airplane to perform interior firefighting and rescue of passengers and crewmembers. (A-14-XX)
- Work with the Aircraft Rescue and Firefighting (ARFF) Working Group to develop policy guidance and training materials to ensure that all airport and mutual aid firefighting officers placed in command at the scene of an aircraft accident have at least a minimum level of ARFF training. (A-14-XX)
- Issue a CertAlert to all Part 139 airports to distribute the information contained in the Federal Aviation Administration’s (FAA) legal interpretation of 14 CFR 139.319 that requires all personnel assigned to aircraft rescue and firefighting duties to meet the initial and recurrent training and live-fire drill requirements and clarify how the FAA will enforce this regulation. (A-14-XX)
- Conduct a special inspection of San Francisco International Airport’s emergency procedures manual and work closely with the airport to ensure that the airport meets its obligations under Part 139.325. (A-14-XX)
To Asiana Airlines:
- Reinforce, through your pilot training programs, flight crew adherence to standard operating procedures involving making inputs to the operation of autoflight system controls on the 777 mode control panel and the performance of related callouts. (A-14-XX)
- Revise your flight instructor operating experience (OE) qualification criteria to ensure that all instructor candidates are supervised and observed by a more experienced instructor during OE or line training until the new instructor demonstrates proficiency in the instructor role. (A-14-XX)
- Issue guidance in the Boeing 777 Pilot Operating Manual that after disconnecting the autopilot on a visual approach, if flight director guidance is not being followed, both flight director switches should be turned off. (A-14-XX)
- Modify your automation policy to provide for more manual flight, both in training and in line operations, to improve pilot proficiency. (A-14-XX)
- Using the guidance developed by the low-energy alerting system panel created in accordance with recommendation , develop and evaluate a modification to Boeing wide-body automatic flight control systems to help ensure that the aircraft energy state remains at or above the minimum desired energy condition during any portion of the flight. (A-14-XX)
- Revise your 777 Flight Crew Operating Manual to include a specific statement that when the autopilot is off and both flight director switches are turned off, the autothrottle mode goes to speed (SPD) mode and maintains the mode control panel-selected speed. (A-14-XX)
To the Aircraft Rescue and Firefighting Working Group:
- Work with the Federal Aviation Administration and equipment manufacturers to develop and distribute more specific policies and guidance about when, how, and where to use the high-reach extendable turret’s unique capabilities. (A-14-XX)
- Work with medical and medicolegal professional organizations to develop and distribute guidance on task prioritization for responding aircraft rescue and firefighting (ARFF) personnel that includes recommended best practices to avoid striking or rolling over seriously injured or deceased persons with ARFF vehicles in a mass casualty situation. (A-14-XX)
- Develop a minimum aircraft rescue and firefighting staffing level that would allow exterior firefighting and rapid entry into an airplane to perform interior firefighting and rescue of passengers and crewmembers. (A-14-XX)
- Develop and distribute, in conjunction with the Federal Aviation Administration, guidance and training materials to ensure that all airport and mutual aid firefighting officers placed in command at the scene of an aircraft accident have at least a minimum level of airport rescue and firefighting training. (A-14-XX)
To the City and County of San Francisco:
- Routinely integrate the use of all San Francisco Fire Department medical and firefighting vehicles in future disaster drills and preparatory exercises. (A-14-XX)
- Implement solutions to the communications deficiencies identified in ICF International’s after-action report as soon as practicable. (A-14-XX)