Impaired Judgment, Decision Making and Flying Skills due to Fatigue (OGHFA SE)
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|Content source:||Flight Safety Foundation|
|Human Factors Aspects||Fatigue, Fixation, Critical Thinking, Judgment, Decision Making|
|ENR / APR|
|Operator's Guide to Human Factors in Aviation|
|Impaired Judgment, Decision Making and Flying Skills due to Fatigue|
The Accident as a Situational example
Your crew has been recalled to flying duty for an unexpected trip to replace another aircraft that is grounded because of mechanical problems. You have been awake during the preceding two nights, and your crew has been on duty for about 18 hr, having flown all night before accepting this new assignment. The captain feels tired when accepting this mission but not to the point of refusing it. After an initial positioning flight, your crew reviews arrival and departure procedures for the destination while the aircraft is loaded. None of the crew has ever landed this aircraft type at the destination airport.
Upon completion of the aircraft’s dispatch and loading operations, the flight departs in the early afternoon with the captain pilot flying (PF) and you as pilot not flying (PNF). The aircraft also has a highly qualified flight engineer.
After two and a half hours of flight, you begin your approach and are transferred from the radar controller to the tower controller, who requests you to report at a specific place, “Point Papa.” Moments later, the tower requests you to remain within designated airspace and close to the runway related to the point designated by a flashing strobe light.
The strobe light is mounted on a guard tower along the shoreline at the border of a foreign country. There is only one strobe, and it is used as a visual aid to identify the location of the border fence. Today, the strobe light is not working, but this fact is not reported by the tower controller.
This strobe light is supposed to help maintain the necessary space to turn right towards the nearby runway for landing. The aircraft slows down with full flaps and gear down, and the captain repeatedly tells you and the flight engineer that he has difficulty identifying the runway and the strobe light. He receives advice from his crewmembers to slow down even more and check the turn.
What would your strategy be for landing?
This approach is becoming even more troublesome as there is a southerly wind resulting in increased groundspeed during the base leg and an increased turn radius to align the aircraft with the runway, making it necessary to start the turn earlier or use a steeper turn to maintain the proper ground track.
Would you continue the landing?
Being on a wide base turn at about 1,000 ft, the aircraft turns late at a bank angle of 30 to 40 degrees. At 400 ft, the bank angle increases to 60 degrees while still overshooting the runway extended centerline.
The aircraft then turns right as if the pilot is using rudder to make the runway centerline, rocking toward wings level. At that point, the right wing appears to stall, the aircraft rolls to a bank of 90 degrees and pitches down after stalling. The aircraft hits terrain west of the approach end of runway and is destroyed.
The three crew members survive, but they are seriously injured. The stick-shaker activated seconds before the stall and the cockpit voice recorder (CVR) recorded that maximum power had been called for, even though by then it was too late.
Data, Discussion and Human Factors
Approach-and-landing accidents account for 55 percent of hull losses and 50 percent of fatalities. (Flight Safety Digest, “Killers in Aviation,” 1999.)
The investigation reviewed cumulative totals for sleep and wakefulness in the 28.5 hr prior to the accident, which confirmed that fatigue played a pivotal role for all the crewmembers, even though the flight engineer had only joined the others on the morning of the event.
The crew had been on duty for about 18 hr at the time of the accident, having flown all night before accepting this new assignment. The captain had felt tired when accepting the mission but not to the point of refusing it, a practice that would not be welcomed. Crew scheduling stated it was told by dispatch that the crew would complete its sequence within the 24-hr duty time, which did not pose any legal problem for the international flight.
Substandard performance by an experienced and proficient crewmember may reflect the debilitating influences of fatigue indicated by three factors pushing them over the edge and negatively affecting judgment:
- Cumulative sleep loss, in the 28.5 hr prior to the accident :
- the captain had been awake 23.5 hr with only 5 hr of sleep,
- the first officer had been awake 19 hr with only 8 hr of sleep,
- the flight engineer had been awake 21 hr with only 6 hr of sleep,
- These continuous hours of wakefulness created the likelihood of committing procedural and tactical decision-making errors,
- Circadian disruption, whereby two periods of maximum sleepiness merge as regulated by the brain, i.e. between 3 and 5, morning or afternoon, the latter being applicable to the time of this event, late afternoon, when waking performance and alertness only just start to rise again,
Crewmembers had been awake during the preceding two nights and had tried to sleep during the day, adding to their circadian sleep disorder. In fact, both the captain and first officer stated that they normally needed some 8 hr sleep per night, but in the 48 hr preceding the flight they had only slept 8 and 10 hr, respectively. The flight engineer normally slept about 9.5 hr each night but had only had 12 hr in the preceding 48.
The result was delayed reaction time as the captain became slow in his decision making and was subject to tunnel vision or fixation, focusing exclusively on one aspect to the exclusion of others. He became fixated on the strobe light and was continually trying to locate it rather than flying the aircraft. Fatigue had led him to being lethargic and indifferent to the developing situation — the non-stabilized approach and the lack of situational awareness relative to the runway.
The problem, however, was that the captain did not know that the strobe light was inoperative and continued to look for it because the first officer had falsely identified it, as he himself was fatigued.
Had the captain known there was no strobe light, he would probably have concentrated on flying the aircraft and might have recognized the evolving lethal cocktail of low airspeed, steep bank, low altitude and increasing stall speed as a result of increasing bank angles in the attempt to still try to make the runway so late on short final. Had the captain been in a critical-thinking mode and had not suffered severe fatigue, he would most likely have reduced the bank angle, increased thrust, levelled the wings and gone around.
The approach was quite demanding and easily caused visual confusion. There was neither a missed approach briefing nor any specific review of the difficulties inherent in this very specific non-precision approach.
The captain’s decision to land on the runway — and not on the reciprocal because of prevailing winds — was not challenged by either of the other crewmembers, who knew this approach was going to be difficult.
Toward the final approach crew communications deteriorated even more when both the flight engineer and the first officer repeatedly tried to express their doubts about the flight’s successful outcome. The tired captain seemed to ignore their concerns and suggestions for a go-around. The first officer failed to assist him in calling out safety-related information concerning runway proximity and excessive bank angle and not supporting the flight engineer’s pressing warnings about dangerously low airspeed.
Prevention Strategies and Lines of Defense
It is a fact that sleepiness traditionally has not been considered very seriously. Operationally, alertness matters more than fatigue as it conditions almost every aspect of human capability and performance. And when it comes to scheduling practices, irrespective of organization, personal relations, organizational issues and even politics often confuse the subject.
Hence, ICAO recommends setting up fatigue and alertness management systems as dedicated safety management systems to embed this specific preoccupation and tie it with scheduling into an airline’s prevention strategies and lines of defense.
The following strategies are recommended to avoid this type of incident:
- Because of the difficulties inherent in this approach, the crew should have focused more on preparing for a go-around.
- Explicitly agree on limits beyond which a go-around or other recovery action will be initiated.
- Explicitly define task-sharing so that it is clear who is to monitor all critical flight parameters.
- Work as a team to perform accurate risk assessments and tactical decision making based on:
- Approach type
- Risk of specific threats
- Conduct effective briefings that fully review approach procedures, profiles and aircraft configurations, including:
- Final Approach Fix (FAF)
- Minimum Descent Altitude (MDA)
- Do not fall prey to press-on-it-is or fixation by yielding to ATC or time pressures to rush the approach.
- If necessary, execute a go-around to provide time to build situational awareness and stabilize any stressful situation.
- Buy time to create common situational awareness among the crew.
- Make sure you use callouts effectively when flying an unfamiliar non-precision approach.
Summary of Key Points
This accident could have been prevented if the crew had recognized that all three were exhausted from fatigue from their previous flight duties and if they had taken the right decision not to accept the flight. Had this crew not been overly exhausted, they would have routinely performed the more difficult approach. However, unable to cope with more workload, the captain trapped himself by focusing on a single task, searching for a missing strobe light. Sleepiness impaired his decision making, reaction time, coordination with the rest of the crew and information processing.
Addressing situations involving impaired decision-making, judgment and flying abilities due to fatigue requires:
- Being sensitive to possible fixation, tunnel vision and press-on-it-is.
- Maintaining situational awareness at all times and assess whether available information is sufficient to support mission goals.
- Preserving judgment to allow sufficient time to prepare for essential aspects of flight management such as conducting briefings and working together as a team to enable critical thinking and maintain appropriate decision making.
- Managing pressures, stress and distractions due to unexpected events, unusual circumstances or breakdowns in crew communications when the situation becomes very critical.
Additional OGHFA Material
- Situational Awareness
- Pilot judgment and expertise
- Fatigue Manifestations
- Circadian Rhythms
- Managing Interruptions and Distractions
- Flight Preparation and Conducting Effective Briefings
- Situational Awareness
- Fatigue and Alertness Management in Aviation
- Managing Interruptions and Distractions
- Critical Thinking
- Operations Golden Rules