Flight Path Monitoring

Flight Path Monitoring

Definition

Flight path monitoring means the observation and interpretation of the flight path data, aircraft-configuration status, automation modes and on-board systems appropriate to the phase of flight. It involves a cognitive comparison of real-time data against the expected values, modes and procedures. It also includes observation of the other pilot and timely intervention in the event of a deviation.

This definition covers anytime the aircraft is in motion, including during taxi. It also includes continuous awareness of both the trajectory and energy state of the aircraft.

Description

Monitoring covers an extensive behavioural skill set that all pilots are expected to apply in the cockpit. The designated Pilot Flying (PF) is responsible for flying the aircraft in accordance with the operational brief and for monitoring the flight path. The Pilot Monitoring (PM) will have an explicit set of activities designated by the Standard Operating Procedures (SOPs) , and as such will have a specific and primary role to monitor the aircraft’s flight path, communications and the activities of the PF. Both pilots are responsible for maintaining their own situation awareness gained through cross-checking each other’s actions, communication of intent and diligent observation of the PF selections, mode activations and aircraft responses. Predictive monitoring supports anticipation of expected threats and the mitigation of consequences. Reactive monitoring enables the identification of unexpected/pop-up threats and mitigation of consequences; the detection and correction of errors; and the recognition of and recovery from undesired aircraft states.

Techniques

The cognitive processes engaged during monitoring are complex and involve the selective application of mental resources to encode the sensory inputs whilst performing a goal directed task. The senses relating to flight path monitoring are mainly visual and auditory, but tactile inputs from the flight controls (e.g. stick shaker, aeroplane buffet, etc.) can influence the monitoring task particularly in the event of a stall. Similarly, the smell and taste senses can alert the flight crew to fumes in the cockpit and therefore also perform a monitoring stimulus. Intent also forms an important part of monitoring and provides a baseline against which to monitor. Intent relates to system behaviour (what it is going to do), aircraft handling (predicted flight path/aircraft manoeuvrability) and Pilot Flying’s intent (the plan). Timely, accurate monitoring activities will result in outputs that, following crew judgement and decision making, can take the form of:

  • Verbalization to other pilot or self;
  • Non-verbal communication in the form of gesture/eye contact;
  • Note-taking in the case of auditory monitoring;
  • Reinforcement of collective situation awareness; and,
  • Maintenance of the mental model of the aircraft state.

Regarding physical ergonomics, pilots must be able to see and hear all information relevant to their monitoring tasks. Their seat positions must be adjusted to the design eye position to enable each pilot to view the internal displays and controls whilst maintaining an adequate view of the external scene. The optimal seat position is usually set by reference to two small balls on the central windscreen pillar. The balls appear aligned only when the pilot’s eye is at the design position.

Vision is a very complex subject and involves the ability of the eye to adapt to different lighting levels (called adaptation), focus on the information (normally referred to as accommodation) and to perceive information, such as texts and graphics, as legible at the required viewing distance (called visual acuity). Adaption, accommodation and acuity all vary with, and are affected by, age. Pilots need to be aware if they are experiencing any difficulty with focus, adaption or legibility of the displayed information as this will certainly compromise the monitoring task. Medical professionals will be able to advise on correction or treatment if necessary.

Hearing can be impaired by accumulation of wax in the outer ear (which is easily remedied), a head cold which blocks the Eustachian tube and prevents equalization of pressure or by infections in the middle ear. Hearing can be expected to deteriorate with age particularly with the higher frequencies. In addition, high ambient noise environment or distractions/interruptions in the cockpit can impact the clarity of aural messages. Under all circumstances, if there is any ambiguity related to information received aurally then ask for it to be repeated.

Barriers to Monitoring

Many factors hamper monitoring, including system and ergonomic design, organisational factors and external environment. But the biggest concern relates to human vulnerabilities, such as complacency/inattention, distraction, low attentional resource, low arousal, disorientation, tiredness etc, and stressors (i.e., workload, etc.). These concerns arise from some relatively recent accidents and incidents.

Safety experts emphasize that it can be difficult for humans to effectively monitor for errors and deviations on a continuous basis when errors and deviations rarely occur, particularly in a highly automated environment. This holds true over the range of workload conditions experienced by the flight crew members. Monitoring during high-workload periods is critical because these periods present situations in rapid flux and because high workload increases vulnerability to error. However, studies show that poor monitoring performance can be present during low-workload periods as well. Lapses in monitoring performance during lower-workload periods are often associated with boredom, complacency, or both.

Potential challenges and barriers to effective monitoring include:

  • Time Pressure – Time pressure can exacerbate high workload and increase errors. It can also lead to rushing and “looking without seeing."
  • Lack of Feedback – When monitoring lapses occur, pilots are often unaware that monitoring performance has degraded.
  • Design of SOPs – Procedures may fail to explicitly address monitoring tasks.
  • Automation – Pilots’ inadequate mental model of autoflight system modes. Pilots may not have a complete or accurate understanding of all functions and behaviours of the autoflight system. Some aspects of automated systems for flightpath management are not well matched to human information processing characteristics.
  • Training – Training may overlook the importance of monitoring and how to do it effectively. Lack of emphasis on monitoring may occur in training and evaluation.

Solutions

While different types and levels of pilot training may involve pilots with differing levels of competence, the training of flight path monitoring should include uniform objectives and standards. Therefore, because the same monitoring concepts apply to all pilots, course content should not differentiate between different types of training courses. A graduated approach should be taken in developing an integrated pilot monitoring training program. It should start with solid grounding in theoretical knowledge, followed by instructor-led case studies. This should include videos and finally line-oriented flight training (LOFT), progressively building on each layer of content:

  • Knowledge – Without proper knowledge of systems and automation, the flight crew will not be able to understand nor predict the aircraft’s behaviour.
  • Skill – Without the necessary skills to operate the aircraft effectively, a flight crew will be overwhelmed by the flight path monitoring tasks.
  • Discipline – Discipline is a foundation for monitoring. Adherence to division of duties is essential for managing workload.
  • Attitude – Developing the right attitude often is the most important aspect of a training program.

Monitoring requires motivation and discipline and must be a continuous effort. The primary aim for flight crew members should be to effectively monitor the flight path, but first, flight crews must be well-trained in flying skills, discipline and behaviours . Without these, effective monitoring may not be possible.

Accidents & Incidents

On 10 April 2019, an Airbus A321 suddenly rolled sharply left just as it was getting airborne from New York JFK at night and reports followed of left wing damage observed from the cabin. After an uneventful return to land, evidence of wing impact was found beyond the edge of the 60 metre-wide runway and confirmed by wing inspection. The left roll during rotation was attributed to an excessive and unexplained left rudder pedal input by the Captain. The damage caused was sufficient to result in the six year old aircraft being declared an economic hull loss and scrapped.

On 11 September 2021, a Boeing 737-800 was instructed to discontinue an ILS approach to runway 34 at Aberdeen, climb to 3000 feet and turn left onto a westerly heading. With the Autopilot disconnected it approached the cleared altitude but before reaching it rapidly descended to just over 1500 feet above terrain before climbing away, the whole event occurring in IMC. The episode was attributed to crew overload in manual flight consequent upon the combination of the heading instructions, flap configuration changes and a complete absence of pitch trim. Both pilots’ pandemic-related lack of the usual operational recency was noted.

On 6 January 2018, a Boeing 737-900 and an Airbus A320 both inbound to Surabaya with similar estimated arrival times were cleared to hold at the same waypoint at FL100 and FL110 respectively but separation was lost when the A320 continued below FL110. Proximity was limited to 1.9nm laterally and 600 feet vertically following correct responses to coordinated TCAS RAs. The Investigation found that all clearances / readbacks had been correct but that the A320 crew had set FL100 instead of their FL110 clearance and attributed this to diminished performance due to the passive distraction of one of the pilots.

On 29 November 2017, a Boeing 737-900 on an ILS approach at Atlanta became unstable after the autothrottle and autopilot were both disconnected and was erroneously aligned with an occupied taxiway parallel to the intended landing runway. A go-around was not commenced until the aircraft was 50 feet above the ground after which it passed low over another aircraft on the taxiway. The Investigation found that the Captain had not called for a go around until well below the Decision Altitude and had then failed to promptly take control when the First Officer was slow to begin climbing the aircraft.

On 1 January 2020, an Airbus A350-900 made an unstabilised night ILS approach to Frankfurt in good visual conditions, descending prematurely and coming within 668 feet of terrain when 6nm from the intended landing runway before climbing to position for another approach. A complete loss of situational awareness was attributed to a combination of waypoint input errors, inappropriate autoflight management and communication and cooperation deficiencies amongst the operating and augmenting flight crew on the flight deck who were all type-rated holders of Thai-issued ATPLs. Neither of the observing pilots detected anything abnormal with the way the approach was being flown.

On 10 September 2017, the First Officer of a Gulfstream G550 making an offset non-precision approach to Paris Le Bourget failed to make a correct visual transition and after both crew were initially slow to recognise the error, an unsuccessful attempt at a low-level corrective realignment followed. This had not been completed when the auto throttle set the thrust to idle at 50 feet whilst a turn was being made over the runway ahead of the displaced threshold and one wing was in collision with runway edge lighting. The landing attempt was rejected and the Captain took over the go-around.

On 19 January 2021, a Boeing 737-400SF on an ILS approach to Exeter became unstabilised below 500 feet but despite multiple EGPWS ‘SINK RATE’ Alerts, a go-around was not initiated. The subsequent touchdown recorded 3.8g and caused such extensive damage that the aircraft was declared a hull loss. The Investigation found that the First Officer, who had more hours flying experience than the 15,000 hour Captain, had failed to adequately control the flight path below 500 feet and noted that whilst the Captain had commented on the excessive rate of descent, he had not called for a go around.

On 10 June 2018, a Boeing 737-800 departing Amsterdam with line training in progress and a safety pilot assisting only became airborne just before the runway end. The Investigation found that the wrong reduced thrust takeoff performance data had been used without any of the pilots noticing and without full thrust being selected as the end of the runway approached. The operator was found to have had several similar events, not all of which had been reported. The implied absence at the operator of a meaningful safety culture and its ineffective flight operations safety oversight process were also noted. 

On 12 September 2020, an Airbus A318 was seriously mismanaged during a largely autopilot-controlled ILS glideslope capture from above and despite being unstabilised after the crew had intentionally ignored required approach management procedures, the flight was continued without hesitation to a landing. The Investigation found that the operator’s oversight of operating standards relating to unstabilised approaches was systemically flawed and also insufficiently supportive of their ‘Evidence Based Training’ method used for pilot training. It was also noted that the Captain involved had stated to the Investigation that “he considered this flight as a non event”.

On 20 December 2019, an Airbus A318 making a tailwind ILS approach to Toulon-Hyères with the autopilot engaged and expecting to intercept the glideslope from above had not done so when reaching the pre-selected altitude and after levelling off, it then rapidly entered a steep climb as it captured the glideslope false upper lobe and the automated stall protection system was activated. Not fully following  the recovery procedure caused a second stall protection activation before a sustained recovery was achieved. The Investigation noted Captain's  relative inexperience in that rank and a First Officer's inexperience on type.

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