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The Changing Roles of Technology and People in Aviation
Published in José Sánchez-Alarcos, Aviation and Human Factors, 2019
Since this same failure happened on other planes that avoided a bad outcome, it seems that the event could have been avoided through alertness, with better visibility or both. The official report includes two paragraphs very clearly pointing to the lack of system understanding by the pilots: The Board concludes that the improper functioning of the left-hand radio altimeter system led to the thrust from both engines being reduced by the autothrottle to a minimal value too soon, ultimately causing too big a reduction in speed. The airspeed reached stall speed due to a failure of monitoring the airspeed and pitch attitude of the aircraft and a failure to implement the approach to stall recovery procedure correctly. This resulted in a situation where the wings were no longer providing sufficient lift, and the aircraft crashed.…The erroneous altitude reading … was used by various aircraft systems, including the autothrottle. The crew were unaware of this, and could not have known about it. The manuals for use during the flight did not contain any procedures for errors in the radio altimeter system. In addition,the training that the pilots had undergone did not include any detailed system information that would have allowed them to understand the significance of the problem.
Speaking for the Second Victim
Published in Philip J. Smith, Robert R. Hoffman, Cognitive Systems Engineering, 2018
Because of its intermittent radar altimeter fault (essentially believing the jet was already on the ground), that radar altimeter was telling the engines to go to idle. This while the crew believed the autothrottle was getting faithful information from the co-pilot’s radar altimeter, as that is what they thought they’d set up. The co-pilot’s autopilot, in other words, was diligently flying the approach track to the runway (or trying to keep the nose on it at least) while the autothrottle system had already decided it was time to land. As a result, speed bled away. The aircraft had been kept high by air traffic control and had had to go down and slow down at the same time—this is very difficult with newer jets, as they have highly efficient wings. Going down and slowing down at least requires the engines to go to idle and remain there for a while. In other words, the action of the autothrottle system (while actually the result of a misinformed radar altimeter) was entirely consistent with crew intentions and expectations. It was only during the last seconds that the crew would have had to notice that the engines remained idle, rather than slowly bringing some life back so as to help them stay on speed. In other words, the crew would have had to suddenly notice the absence of change. That is not what human perceptual systems have evolved to be good at.
Automation surprises in commercial aviation
Published in Michael A. Vidulich, Pamela S. Tsang, John Flach, Advances in Aviation Psychology, Volume 2, 2017
Overall, 55 percent of the automation surprises occurred during the arrival and approach phases of flight (see Table 9.2). By contrast, only 13 percent of the events occurred during cruise. However, this pattern differed according to the type of event. Failures or freezing of autoflight system components, categorized as “AFS component” failures in Table 9.2, were evenly divided between climb, cruise, and approach. Two of the three autothrottle events occurred in cruise. Although most of the autopilot disconnects, unexpected mode changes, and control anomalies occurred during arrival and approach, a substantial proportion occurred during climb and cruise. Display faults occurred equally during climb, cruise, and arrival. Waypoints dropping from FMS flight plans as well as lateral course deviations occurred mainly during climbs below 10,000 feet, and arrival and approach phases.
Plan B for Eliminating Mode Confusion: An Interpreter Display
Published in International Journal of Human–Computer Interaction, 2021
The autopilot (or autothrottle) mode reverts to another mode; the pilot is unaware of the reversion: Turkish Airlines Boeing 737–800 accident, Amsterdam, 2009 – Due to a radio altimeter failure, the autothrottle reverted into a mode that does not manage airspeed on approach; the flightcrew was unaware of this mode change and its implications. Airspeed dropped off naturally during the descent but continued to drop below its target speed because it was not protected by autothrottle. Then, the autopilot pitched the airplane up to attempt to maintain the glidepath until the stick shaker was triggered. The flightcrew failed to recover from the stall.