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National Transportation Safety Board Releases Report Abstract on Atlas 3591
Earlier this week, the National Transportation Safety Board (NTSB) released a synopsis of its forthcoming final report on the crash of Atlas Air Inc. Flight 3591 in February of 2019. The NTSB is currently in the process of making final revisions, and the information in the abstract is subject to editing.
On February 23, 2019, Atlas flight 3591, operated with a Boeing 767-375BCF, was approximately 40 miles east of Houston’s George Bush Intercontinental Airport. At approximately 6,300 feet MSL, the 767’s go around mode was activated and shortly thereafter it entered a rapid descent and crashed into Trinity Bay. At the time of the incident, the first officer was flying the aircraft.
The NTSB’s report abstract identifies seven safety issues evaluated by its investigation; inadvertent activation of the 767’s go around mode; flight crew performance; the carrier’s evaluation of the first officer; industry pilot hiring process deficiencies; awareness information for Boeing 757 and 767 pilots; adaptations of automatic ground collision avoidance technology; and cockpit image recorders.
The report also includes a list of 23 findings. Among the findings, the flight crew’s certifications and qualifications; air traffic control services; condition and maintenance of the 767’s structures, powerplants, systems; and the 767’s weight and balance were not factors in the accident. Based on the report, it appears that the activation of the 767’s go around mode was of particular interest to the NTSB. Go around mode is activated by pressing a switch on the throttle lever which cues the aircraft’s autothrottle to apply the thrust necessary to perform a go-around.
The findings state that the activation of the 767’s go-around mode was “unintended and unexpected” by the flight crew. It occurred during an encounter with light turbulence and “likely” instrument meteorological conditions. According to the findings, this inadvertent activation of the go-around mode “likely resulted from unintended contact between the first officer’s left wrist or watch and the left go around switch due to turbulence-induced loads that moved his arm.” The first officer then likely experienced a “pitch up somatogravic illusion.”
A somatogravic illusion occurs during high acceleration when there are no clear visual references (such as in instrument meteorological conditions). Essentially, the brain misinterprets the acceleration as an upward pitch. A rapid deceleration would have the opposite effect, the brain would misinterpret the deceleration as a downward pitch. The danger of this illusion to pilots is accordingly clear; a pitch up illusion can lead to a pilot believing he or she is pushing the nose of the aircraft down in recovery from an excessive pitch up attitude when, in fact, they are actually entering a dive because there was no excessive pitch up attitude to begin with. Conversely, a pitch down illusion can lead a pilot to believe he or she is pulling the nose up in recovery from an excessive pitch down attitude, when, in fact, they are actually entering an excessive pitch up attitude because there was no excessive pitch down attitude to begin with.
With an understanding of the somatogravic illusion, the NTSB’s probable cause of the accident becomes easier to comprehend. According to the NTSB, the probable cause of the Atlas 3591 accident was:
“The inappropriate response by the first officer as the pilot flying to inadvertent activation of the go-around mode, which led to his spatial disorientation and nose-down control inputs that placed the airplane in a steep descent from which the crew did not recover. Contributing to the accident was the captain’s failure to adequately monitor the airplane’s flight path and assume positive control of the airplane to effectively intervene. Also contributing were systemic deficiencies in the aviation industry’s selection and performance measurement practices, which failed to address the first officer’s aptitude-related deficiencies and maladaptive stress response. Also contributing to the accident was the Federal Aviation Administration’s failure to implement the Pilot Records Database in a sufficiently robust and timely manner.”
In light of the NTSB’s findings, the accident will almost certainly start a conversation with a renewed sense of urgency regarding the implementation of the pilot records database called for in the Airline Safety and Federal Aviation Administration Extension Act of 2010. It will almost certainly also prompt a close look at airline hiring practices and procedures. Indeed, four of the six safety recommendations the NTSB is making as a result of the accident center around pilot hiring processes and procedures. Among those recommendations is an advisory circular revision to emphasize the importance of including flight operations subject matter experts early in the pilot records review process and implementing the pilot record database.
The NTSB’s report abstract is available on its website. According to the NTSB, the final report and pertinent safety recommendation letters will be distributed to recipients as soon as possible.
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