Atlas B763 at Houston on Feb 23rd 2019, loss of control on approach
Last Update: August 5, 2020 / 18:45:43 GMT/Zulu time
The NTSB determines that the probable cause of this accident was the inappropriate response by the first officer as the pilot flying to an 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 flightpath 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.
The NTSB analysed the first officer's response and somatogravic illusion:
The NTSB notes that, about 2 minutes before the go-around mode was activated, the CVR captured a conversation that suggested the FO had briefly experienced an anomaly with his EFIS display. The FO transferred PF duties to the captain and mentioned the EFI switch, which pilots can use to resolve display faults. Transferring control of the airplane to the other pilot would be consistent with Atlas’ procedures for a PF needing to address a non-normal occurrence, such as a display issue. Two seconds after the FO mentioned the EFI switch, he said, “okay, I got it back,” presumably referring to his displays, and the captain acknowledged.
Although the FDR data do not show any changes in the EFI switch position during the flight, that parameter was sampled only once every 4 seconds, and simulator observations showed the EFI switch could be cycled (from normal to alternate and back) to clear an issue such as an intermittent display blanking in less than 4 seconds. Addressing a display fault involving a loss of parametric data would require a pilot to set the EFI switch to the alternate position and leave it there. Thus, the NTSB concludes that, whatever EFIS display anomaly the FO experienced was resolved to both crewmembers’ satisfaction (by the FO’s cycling of the EFI switch) before the events related to the accident sequence occurred.
Before the inadvertent activation of the go-around mode, the airplane was descending to a target altitude of 3,000 ft msl, and the flight crew would have been expecting the airplane’s automation to increase thrust and increase pitch slightly from about 1° nose-down to level off once the flight reached that altitude. However, once the go-around mode was inadvertently activated about 6,300 ft msl, the airplane’s automation advanced the thrust levers and increased the airplane’s pitch to about 4° nose up to initiate a climb. In addition, the flight mode annunciator changed to indicate go-around mode activation by illuminating “GA/GA/GA/CMD.”
The unexpected mode change associated with the inadvertent go-around mode activation (and the higher altitude at which it occurred) would have been recognizable to the FO and the captain through an effective instrument scan. Both the flight mode annunciator and the engine indicating and crew-alerting system (EICAS) would have displayed “GA” indications, and the altimeter would have indicated about 6,300 ft msl.
According to Atlas’ procedures, the expected crew response to unwanted operation of automated flight systems was to disconnect the automation. However, neither the FO nor the captain ever acknowledged that the airplane had transitioned to go-around mode or disengaged the autopilot or autothrottle. Thus, the NTSB concludes that, despite the presence of the go-around mode indications on the flight mode annunciator and other cues that indicated that the airplane had transitioned to an automated flight path that differed from what the crew had been expecting, neither the FO nor the captain were aware that the airplane’s automated flight mode had changed.
Research has shown that pilots can miss changes in displayed modes, particularly those that are unexpected (Mumaw et al 2000), and other factors (discussed in the next sections) may have reduced the effectiveness of each crewmember’s scan.
Although the FO did not verbalize awareness that something unexpected had happened until about 13 seconds after go-around mode activation (when he said “oh” and then “whoa” in an elevated voice), manual control inputs that began sooner suggest that the FO (as PF) had sensed changes in the airplane’s state and had begun to react without fully assessing the situation.
The manual retraction of the speedbrakes 5 seconds after go-around mode activation was likely performed by the FO (as PF) instinctively once he felt the increased load factor from the airplane leveling off and heard and felt the engine thrust increasing. He had likely been anticipating the need to perform this task when the airplane leveled off.
However, beginning about 1 second later, as the airplane’s acceleration and upward pitch began to increase (which would have resulted in the aft movement of the GIF vector sensed by the pilots), manual forward control column inputs were applied, overriding the small, autopilot-driven pitch-up command and resulting in decreasing pitch. Thus, the NTSB concludes that, given that the FO was the PF and had not verbalized any problem to the captain or initiated a positive transfer of airplane control, the manual forward elevator control column inputs that were applied seconds after the inadvertent activation of the go-around mode were likely made by the FO. Further, the captain was communicating with an air traffic controller at the time, consistent with his PM duties.
The human body uses three integrated systems to determine orientation and movement in space: vestibular (otolith organs in the inner ear that sense position), somatosensory (nerves in the skin, muscles, and joints that sense position based on gravity, feeling, and sound), and visual (eyes, which sense position based on sight) (FAA 2016, 17-6). The vestibular and somatosensory systems alone cannot distinguish between acceleration forces due to gravity and those resulting from maneuvering the airplane.
Thus, when visual cues are limited and an airplane rapidly accelerates or decelerates, a pilot may be susceptible to a somatogravic illusion (FAA 2016, 17-6). Somatogravic illusion is a form of spatial disorientation that results from a false sensation of pitch due to the inability of the otolith organs of the human inner ear to separate the gravitational and sustained linear acceleration components of the GIF vector (Young 2003 and Cheung 2004). Rapid acceleration in an airplane stimulates the otolith organs in the same way as tilting the head backward and may lead a pilot to mistakenly believe that the airplane has transitioned to a nose-up attitude (FAA 2016, 17-7).
The accident airplane was likely flying in IMC when the go-around mode was activated. The timing of the FO’s subsequent nose-down control inputs correlated with increases in the airplane’s longitudinal acceleration associated with the go-around mode-commanded increase in engine thrust and retraction of the speedbrakes. This relationship suggests that the FO experienced a pitch-up somatogravic illusion at that time.
Somatogravic illusion has long been recognized as a significant hazard that is likely to occur under conditions of sustained linear acceleration when outside visual references are obscured (Buley and Spelina 1970, 553-6). Further, such conditions can degrade a pilot’s ability to effectively scan and interpret the information presented on primary flight displays.50 For a pilot flying in IMC with no external visual horizon, maintaining spatial orientation when presented with conflicting vestibular cues depends upon trusting the airplane’s instruments and disregarding the sensory perceptions (FAA 2003, 8).
The NTSB analysed the captain's response:
Like the FO, the captain had been expecting the airplane to automatically increase thrust and slightly increase pitch to level off at the MCP-selected altitude of 3,000 ft msl. The captain, as PM, was required to actively monitor the flight, including the airplane flightpath, automation status, and the FO’s actions as PF. Effective monitoring and crosschecking are essential because detecting an error or unsafe situation can be the last line of defense to prevent an accident (FAA 2004, 14).
Based on the available CVR information, from before activation of the go-around mode until about 10 seconds after, the captain was setting up the approach to IAH on the FMC and communicating with ATC. While setting up the approach, the captain was likely head-down and concentrating on the FMC rather than monitoring the flight instruments or the FO’s actions. This would reduce the captain’s awareness of the airplane’s automation status and energy state and could explain why the captain did not notice the “GA” indications on the flight mode annunciator or the EICAS or that the anticipated increase in airplane thrust began when the airplane was at a much higher-than-expected altitude.
However, the captain’s response to less subtle aspects of the developing situation, such as the FO’s nose-down control column inputs associated with his spatial disorientation, were also delayed. Research has shown that a PM may be slow to take control when the PF is subtly incapacitated (for example, due to spatial disorientation) because the PM’s recognition of something being wrong can be delayed if his or her attention is focused on normal operational tasks or if the deviation in performance is a surprise (Harper, Kidera, and Cullen 1971).
As previously mentioned, at 1238:44, the FO said, “oh,” indicating surprise, which was about 2 seconds after the captain’s last routine radio communication to the controller and concurrent with the controller’s response. It also occurred about 4 seconds after the cockpit’s owl beeper sounded, which, based on the FDR data, likely indicated an autopilot caution alert (due to the opposing manual inputs on the control columns). At 1238:46 (about 15 seconds after the inadvertent activation of the go-around mode), the captain took hold of the left control column and started pulling back, countering the FO’s continued nose-down control inputs. The NTSB concludes that, while the captain was setting up the approach and communicating with ATC, his attention was diverted from monitoring the airplane’s state and verifying that the flight was proceeding as planned, which delayed his recognition of and response to the FO’s unexpected actions that placed the airplane in a dive.
About the time that the captain took hold of the left control column and started pulling back, the thrust levers were abruptly reduced then advanced; however, it is unknown which crewmember took this action. The captain’s action on the control column was not followed by the command “I have control” to indicate a positive transfer of control of the airplane, as required by Atlas procedures. As a result, the captain and the FO each continued to apply opposing forces on the elevator control columns, with the captain adding enough force to overcome the elevator system’s control column override mechanism and split the positions of the elevators on each side.
The captain’s and the FO’s opposing elevator control forces continued for about 10 seconds, during which the airplane’s dive continued to steepen. Thus, the NTSB concludes that the captain’s failure to command a positive transfer of control of the airplane as soon as he attempted to intervene on the controls enabled the FO to continue to force the airplane into a steepening dive.
Although the captain may have been trying to diagnose the situation and determine what corrective actions were needed, he likely experienced startle and surprise once he recognized that the airplane was in a dive, resulting in increased stress and reduced performance. Also, the situation was likely difficult for the captain to evaluate, considering that the FO’s control inputs, the automated inputs, and external forces were each affecting control feel and airplane behavior.
Although the captain asked the FO what was happening, the FO made only panicked statements and was unable to provide the captain with any useful information. The captain was being subjected to the same stressful and disorienting accelerations as the FO, which could have degraded his ability to correctly interpret the instruments and identify the most appropriate course of action. When such situations occur unexpectedly, they can be ambiguous and confusing. The captain’s failure to disconnect the autopilot or autothrottle, in keeping with Atlas’ procedures, during any point in the accident sequence suggests that he had not fully processed the airplane’s energy state, automation status, or the reason for the FO’s actions.
Analysis of the available weather information determined that, once the airplane had descended through an altitude of about 3,000 ft msl (which corresponded with the expected cloud base heights for the area), it would have been exiting IMC; thus, the crew would have been able to clearly see the airplane’s attitude and descending trajectory. About this time, both elevators began to move concurrently to an airplane nose-up position, attaining the full airplane nose-up position and remaining there until the end of the FDR recording. Thus, it likely that both the FO and the captain were pulling back on the control columns to arrest the airplane’s descent, but, by this time, the situation was unrecoverable.
Therefore, the NTSB concludes that the captain’s degraded performance, which included his failure to assume positive control of the airplane and effectively arrest the airplane’s descent, resulted from the ambiguity, high stress, and short timeframe of the situation.
The NTSB analysed the first officer's hiring processes:
When the FO applied for employment at Atlas, he did not disclose having worked for CommutAir in 2011 and Air Wisconsin Airlines in 2012, two airlines from which he resigned after not having completed initial training. Although his employment at CommutAir fell outside the 5-year reporting window required by the PRIA, his employment at Air Wisconsin Airlines did not.
However, the FO’s resume included his employment with another airline (for which he successfully completed training and worked for 2 years), even though his employment there fell outside the PRIA reporting requirements. In addition, when the FO applied to Trans States Airlines in 2014, he did not disclose his previous employment with Air Wisconsin, even though such employment occurred within the 5-year PRIA reporting requirement (see table).
The FO’s training records made available to Atlas under the PRIA included information about his unsuccessful attempt to upgrade to captain on the Embraer ERJ175 at Mesa Airlines, which occurred just 2 months before Atlas hired him. A pilot’s unsuccessful upgrade on the same airplane that he or she had been flying for several years is a significant event for a hiring operator to evaluate, particularly when it is a recent occurrence. However, neither the DA vendor nor Atlas’ HR personnel identified the record of the FO’s unsuccessful upgrade attempt as a “red flag” item to be brought to the attention of Atlas’ director of training. As a result, no one at Atlas followed up with the FO or Mesa Airlines to further evaluate the event before hiring the FO; the FO had already begun Atlas’ initial training and had started Boeing 767 full-flight simulator training at the time the records were obtained.
After the accident FO completed Atlas’ basic indoctrination training and Boeing 767 ground school, he was assigned and completed remedial training to address weaknesses in his knowledge of airplane takeoff and landing performance and airplane systems, and he subsequently passed his oral examination. He was also assigned remedial training in the fixed-base simulator on performing normal procedures, which he successfully completed before he was recommended to progress to the Boeing 767 full-flight simulator.
The FO began full-flight simulator training on August 10, 2017. However, after two sessions, the FO’s simulator partner complained that he was being held back by the FO. According to the fleet captain, at the time, Atlas did not have staff available to continue the FO’s simulator training, so his simulator training sessions were restarted from the beginning on August 27, 2017. On September 3, 2017, after the FO had completed his sixth training session, the effects of a hurricane forced Atlas to shut down all training. The FO’s training did not resume until September 19, 2017, and he failed his practical Boeing 767 type-rating examination 3 days later.
The examiner who observed the FO described him as having been very nervous and said the FO demonstrated “very low” situational awareness, poor CRM, and a tendency to take inappropriate action when he perceived the need to do something. The examiner said the FO’s performance was so poor that he was concerned that the FO would be unable to “mentally recover” enough to complete the course. However, after receiving remedial training on September 25, 2017, the FO passed the type-rating checkride the next day. The Atlas instructor who performed the FO’s remedial training described it as a “great training session” and said he thought the FO had a confidence problem.
When evaluating the FO’s initial training difficulties, Atlas’ fleet captain considered factors that he believed may have adversely affected the FO’s performance, including the training schedule interruptions (which were beyond the FO’s control), family issues the FO was experiencing, and the FO’s potential nervousness during the checkride due to the presence of an FAA examiner. For these reasons, the fleet captain chose to monitor the FO’s operating experience when considering whether the FO should be placed in the PWP. The FO subsequently completed 53 hours of initial operating experience, all of which was completed with an Atlas check airman, and he demonstrated no difficulties with his subsequent recurrent training at Atlas.
For reasons discussed previously in sections 2.4.1 and 2.4.2, Atlas’ director of training was unaware of the FO’s previous failures to complete initial training at two other airlines and his unsuccessful attempt to upgrade to captain at a third; however, it is not known how this information would have affected Atlas’ evaluation of the FO’s hiring application or his performance in its own initial training program.
The manual process by which a hiring operator (or DA) retrieves background records under the PRIA currently involves requesting the records directly from each former employer disclosed by a pilot applicant. Thus, if a pilot intentionally omits a previous employer, as the FO did, the hiring operator may never know the pilot’s complete background.
The accident investigation’s review of records from all of the FO’s previous employers (not all of which the FO disclosed to Atlas and other airlines for which he had worked) determined the FO had a long-term history of training program failures that spanned multiple employers and multiple airplane types. This pattern of failures indicated significant performance deficiencies and was indicative of a pilot with aptitude-related performance difficulties.
Although the FO was able to successfully perform highly proceduralized actions during training when given enough practice, he repeatedly demonstrated that he would become overwhelmed when confronted with novel, compounding, or unexpected situations. Such situations require complex cognitive processing to determine an appropriate response. The dominant predictor of success with such tasks is general cognitive ability, a trait long considered a core aspect of aviation aptitude (Ackerman 1988, 288-318; Ree and Carretta 2009, 111-23). The FO’s pattern of difficulties in training suggests that he may have been weak in this area. Therefore, the NTSB concludes that the FO’s long history of training performance difficulties and his tendency to respond impulsively and inappropriately when faced with an unexpected event during training scenarios at multiple employers suggest an inability to remain calm during stressful situations—a tendency that may have exacerbated his aptitude-related performance difficulties.
Review of data from ASRS reports, The Boeing Company, Atlas, and one other airline found no other known events involving inadvertent activation of the go-around mode on a Boeing 767-series airplane due to unintended contact with a go-around switch. This suggests that such an event on the Boeing 767-series airplane may be rare or may simply go unreported. The expected response to an unintended automation change would be for the pilot to disconnect the automation and return the airplane to its original profile. For such a scenario, a pilot may feel no need to file a voluntary safety report for something considered benign and easily corrected, particularly if the pilot recognized that the activation resulted from unintended contact with the switch, and it did not lead to an undesirable aircraft state or flight path deviation.62
Aircraft Registration Data
This article is published under license from Avherald.com. © of text by Avherald.com.
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