Mastering automation is a foundational skill required to safely operate any modern state-of-the-art aircraft. Under normal circumstances, automation reduces workload, creates efficiencies and, to a fault, is highly dependable. On rare occasions, these highly reliable systems present pilots with an unexpected, obscure, or highly complex scenario that if mismanaged may quickly deteriorate and jeopardize the safety of flight.
The challenge for professional pilots is to not only understand their own human cognitive limitations but to fully comprehend their aircraft’s automated systems and how each relate. From a practical operational standpoint, those same pilots must maintain proficiency, become experts at monitoring, combat complacency, adhere to standard operating procedures (SOP), and mentally stay out in front of these aircraft during all modes of operation.
Safety reports are littered with automation interface issues that pit the pilot against the aircraft. Often these events begin with an automation error, and when not trapped, may evolve into additional errors or an undesired aircraft state (UAS).
Automation errors have led to numerous accidents; categorized as either loss of control in-flight (LOC-I), controlled flight into terrain (CFIT), approach and landing (ALA), and runway excursions (RE) accidents. The list of common automation errors contributing to these accidents is long and varied and may include data entry errors, mode confusion, mode awareness, unexpected mode reversion, and inappropriate use of automation.
Mismanaged automation errors are often coupled with additional errors from the pilot monitoring (PM) such as cross-checking or verification steps. Poor pilot monitoring skills across the industry have been recognized as a threat to aviation safety. When these errors are not trapped, the flightpath and/or energy management may be compromised. Below is an example of an early accident that combined an automation management error and poor active pilot monitoring skills. Considered a “watershed” moment, this accident put the industry “on notice,” that there was a problem managing highly automated aircraft.
Nearly 26 years ago, a simple flight management system (FMS) entry error led to the loss of a Boeing 757 near Cali, Columbia. During this event, on an arrival from the North, ATC offered a straight-in VOR/DME Runway 19 approach, which the crew accepted. The actual clearance was to fly the ROZO 1 arrival for the VOR/DME Runway 19. The captain subsequently made a request with ATC to proceed direct to the ROZO NDB, which was coded as “R” in the FMS. ATC denied this request and reiterated the original clearance for the ROZO 1 arrival with additional instructions to report their position at 21 DME from the airport. The crew misunderstood these instructions. Still in a descent, the pilots selected and executed “R” (ROZO NDB) in the FMS and the aircraft turned to the left 90 degrees and departed the desired lateral course. Passing through 9,000 feet the GPWS “terrain” warning activated and despite the crew’s efforts to recover from the event, the aircraft impacted a mountainside killing 159 people and severely injuring another four.
Verifying the FMS selection and cross-checking the aircraft’s navigation display (it would have indicated a 90-degree turn) may have helped prevent this accident. There were several threats associated with this accident such as language barriers, operating in mountainous terrain, a late-night flight, and a poorly coded (“R”) waypoint and a similarly named procedure; all led to a lot of confusion. From this accident, the industry has learned a lot, but we have a long way to go, considering similar automation-related accidents continue to occur.
The Unevolved Brain
The problem with automation management is twofold; it’s the human, the machine, and how they interface with each other. According to IATA’s study on FMS Data Entry and Error Prevention, the human brain has changed little in hundreds if not thousands of years. Remarkably, even in an “unevolved state," the brain has been able to assimilate well into the complex world of aviation by adapting to new environments and accumulating countless new skills.
In simple terms, the brain has two channels. One channel involves conscious thought in the brain’s “simple but faster processor.” This is the cognitive channel where things like problem-solving and decision-making take place. The other one, the subconscious channel, is taught through repetition by using complex movement sequences, such as tying a shoe, ballroom dancing, or flying an airplane.
According to the IATA study, “The trouble is that each of these channels are vulnerable.” Channel One—the cognitive one—has limited capabilities and is prone to overload in times of stress. Furthermore, this cognitive channel is easily misled by confusing or contradictory inputs and does a poor job at recognizing its own errors.
So, when a NASA Aviation Safety Reporting System submission reads: “Needless to say, confusion was in abundance. There are just too many different functions that control airspeed and descent rates, all of which can control the altitude capture” or “We missed the crossing altitude by 1,000 feet,” those pilots were possibly overloaded, stressed, or having trouble keeping up due to cognitive limitations.
Concerns about an over-reliance on automation and an erosion in manual flying skills relates to Channel Two, the subconscious one. These skills are lost due to a lack of practice, confounded by unfamiliar circumstances or initiated at an inappropriate time.
As aircraft become more sophisticated and automated, the role of the pilot has changed from flying to mostly monitoring and observing. Pilots (as humans) are poor monitors because they are vulnerable to fatigue, distractions, boredom, complacency, illness, and stress—all things that negatively impact concentration.
Failing to monitor an aircraft’s flightpath and energy state is problematic and has been a causal factor in several accidents. Monitoring airspeed is a fundamental skill acquired early during a pilot’s training, yet these accidents occur at an alarming rate.
In 2005, a Cessna Citation 560 crashed while on approach to Pueblo, Colorado. Two pilots and six passengers were killed. Approaching from the east, the crew initially planned to overfly the airport and land on Runway 8L. Upon checking in with Pueblo Approach Control, the crew was advised that they would land on Runway 26R. The aircraft was on autopilot during the descent and arrival into Pueblo. According to the cockpit voice recorder transcript, the flight crew noted the change in runway assignment and immediately tuned the navigational radios and inbound course for Runway 26. According to the NTSB, however, there was an approximate 5-minute delay in conducting the approach briefing. Minutes later the crew began to intercept the localizer and glideslope and to slow and configure the aircraft for landing. During this time, the pilots continued to brief the approach. Moments later the first officer recognized the need to “run the deice boots” and indicated that the aircraft had slowed to Vref. The aircraft continued to slow which caused an aerodynamic stall and the crew failed to recover.
Four years later, in February 2009, Colgan Air Flight 3407, a Bombardier Dash 8-Q400 crashed outside of Buffalo, New York, killing 49 people aboard and one individual on the ground. During this flight, while on approach to Runway 23 at KBUF the crew failed to recognize a loss of 50 knots of airspeed over a period of 22 seconds. The result was an aerodynamic stall that led to a fatal LOC-I accident.
These two accidents demonstrate how distractions, fatigue, stress, and potentially complacency—all human vulnerabilities—can affect concentration and the ability to monitor the energy state of an aircraft.
Outside of the pilot, there is probably some culpability with the design of the aircraft or machine and how it interfaces with the pilot or human. The concept of machine is broadly defined as a device that people interface with, such as a mobile phone, laptop, or in this case, an aircraft.
A productive discussion on human-machine interface must begin with two questions. (1) How do we communicate with the machine? and (2) How does the machine communicate with us? This two-way communication in an aircraft is accomplished using controls, displays, audio cues, etc. The design of these items must consider ergonomics (physical aspects) and must align with the user’s mental model (usage architecture, logic, and intuitiveness) to be effective. The basis for this interface between machine and human is no different than any other form of communication—it’s a two-way conversation.
Third-generation air transport aircraft (the first automated aircraft with FMS and glass cockpits) introduced into service during the 1980s incorporated crude FMS and flight mode annunciator (FMA) displays. Early FMS incorporated monochromatic displays with an alpha-numeric interface, while FMA displays used symbology and (often truncated) nomenclature that included multiple non-intuitive sub-modes. This understandably created several challenges for pilots.
Fortunately, each new generation of aircraft has shown an improvement. Although, as demonstrated with the Boeing 737 Max saga, there are still significant areas of improvement when it comes to automation and the many subsystems associated with complex aircraft. As described below, long before the Max, there was a scenario on 737NGs where a single radar altimeter (RA) failure would force the autothrottle system into a “retard” mode—logic that the aircraft was in the landing flare—on approach.
In February 2009, a Turkish Airlines Boeing 737-800 stalled while on approach and crashed short of Runway 18 at Schiphol Airport in Amsterdam. During this event, a single RA failure caused the autothrottle system to enter the “retard” mode, which the flight crew failed to recognize. As a result, during the approach, the thrust went to idle, allowing the airspeed to decrease to 83 knots (40 knots below Vref). The stickshaker activated at 495 feet and the captain attempted to recover with full power. Without enough altitude or airspeed to recover, the aircraft struck the ground tail first (at 95 knots) and broke into three pieces. Six passengers and three flight crew were killed.
At the time of the accident, SOPs (Turkish Airlines) required both autopilots (a two-channel system) to be engaged during an approach. This action would add redundancy to many critical systems related to the autoflight systems including the autothrottle. During this flight, however, an inexperienced first officer—the pilot flying—failed to engage the second autopilot system. System logic reverted to a single autopilot channel (left only) and relied on the captain’s or left RA for autothrottle input. When the left RA failed, the indication dropped from a valid reading to -8 feet and causing the autothrottle system to enter the “retard” or landing mode.
Mismanaged automation errors and poor flight path and energy state monitoring are at the crossroads of many accident types (CFIT, LOC-I, ALA, and RE). Operators must reinforce their automation philosophies and protocols into training and SOPs.
According to the Flight Safety Foundation (FSF) Approach-and-Landing Accident Reduction Toolkit (Briefing Note 1.2 – Automation), the safe and efficient use of the autoflight system (AFS) and FMS is based on the following three-step method.
Anticipate: Understand system operation and the results of any action, be aware of modes being armed or selected, and seek concurrence with the other flight crewmembers.
Execute: Perform the action on the AFS control panel or on the FMS control display unit (CDU); and,
Confirm: Cross-check armed modes, selected modes, and target entries on the FMA, primary flight display and navigation display, and FMS CDU.
Likewise, pilots must engage in an active monitoring role to identify and correct flightpath or energy state deviations. In addition to the FSF ALAR Toolkit, the FSF has published “A practical guide for improving flight path monitoring.” This document is the go-to for the best practices related to flight path monitoring—it’s a must-read.
For pilots, the guide outlines accepted practices that promote effective monitoring and clearly defines the role of each pilot during various flight phases. Likewise, there are discussions on workload/task management and how best to manage distractions and interruptions. For the operator, the guide provides an outline to create effective SOPs and enhance training profiles to promote better pilot monitoring skills.